1
|
High promiscuity among females of the invasive pest species Drosophila suzukii. Mol Ecol 2023; 32:6018-6026. [PMID: 37804145 DOI: 10.1111/mec.17161] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2023] [Revised: 09/14/2023] [Accepted: 09/25/2023] [Indexed: 10/09/2023]
Abstract
Drosophila suzukii (Matsumura, 1931), the spotted-wing drosophila, is a highly invasive fruit fly that spread from Southern Asia across most regions of Asia and, in the last 15 years, has invaded Europe and the Americas. It is an economically important pest of small fruits such as berries and stone fruits. Drosophila suzukii speciated by adapting to cooler, mountainous, and forest environments. In temperate regions, it evolved seasonal polyphenism traits which enhanced its survival during stressful winter population bottlenecks. Consequently, in these temperate regions, the populations undergo seasonal reproductive dynamics. Despite its economic importance, no data are available on the behavioural reproductive strategies of this fly. The presence of polyandry, for example, has not been determined despite the important role it might play in the reproductive dynamics of populations. We explored the presence of polyandry in an established population in Trentino, a region in northern Italy. In this area, D. suzukii overcomes the winter bottleneck and undergoes a seasonal reproductive fluctuation. We observed a high remating frequency in females during the late spring demographic explosion that led to the abundant summer population. The presence of a high degree of polyandry and shared paternity associated with the post-winter population increase raises the question of the possible evolutionary adaptive role of this reproductive behaviour in D. suzukii.
Collapse
|
2
|
The worldwide spread of Aedes albopictus: New insights from mitogenomes. Front Genet 2022; 13:931163. [PMID: 36092930 PMCID: PMC9459080 DOI: 10.3389/fgene.2022.931163] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2022] [Accepted: 07/28/2022] [Indexed: 11/20/2022] Open
Abstract
The tiger mosquito (Aedes albopictus) is one of the most invasive species in the world and a competent vector for numerous arboviruses, thus the study and monitoring of its fast worldwide spread is crucial for global public health. The small extra-nuclear and maternally-inherited mitochondrial DNA represents a key tool for reconstructing phylogenetic and phylogeographic relationships within a species, especially when analyzed at the mitogenome level. Here the mitogenome variation of 76 tiger mosquitoes, 37 of which new and collected from both wild adventive populations and laboratory strains, was investigated. This analysis significantly improved the global mtDNA phylogeny of Ae. albopictus, uncovering new branches and sub-branches within haplogroup A1, the one involved in its recent worldwide spread. Our phylogeographic approach shows that the current distribution of tiger mosquito mitogenome variation has been strongly affected by clonal and sub-clonal founder events, sometimes involving wide geographic areas, even across continents, thus shedding light on the Asian sources of worldwide adventive populations. In particular, different starting points for the two major clades within A1 are suggested, with A1a spreading mainly along temperate areas from Japanese and Chinese sources, and A1b arising and mainly diffusing in tropical areas from a South Asian source.
Collapse
|
3
|
Bacterial Symbionts in Ceratitis capitata. INSECTS 2022; 13:insects13050474. [PMID: 35621808 PMCID: PMC9147879 DOI: 10.3390/insects13050474] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Revised: 05/06/2022] [Accepted: 05/17/2022] [Indexed: 11/16/2022]
Abstract
Ceratitis capitata (Diptera: Tephritidae) is responsible for extensive damage in agriculture with important economic losses. Several strategies have been proposed to control this insect pest including insecticides and the Sterile Insect Technique. Traditional control methods should be implemented by innovative tools, among which those based on insect symbionts seem very promising. Our study aimed to investigate, through the 16S Miseq analysis, the microbial communities associated with selected organs in three different medfly populations to identify possible candidates to develop symbiont-based control approaches. Our results confirm that Klebsiella and Providencia are the dominant bacteria in guts, while a more diversified microbial community has been detected in reproductive organs. Concertedly, we revealed for the first time the presence of Chroococcidiopsis and Propionibacterium as stable components of the medfly’s microbiota. Additionally, in the reproductive organs, we detected Asaia, a bacterium already proposed as a tool in the Symbiotic Control of Vector-Borne Diseases. A strain of Asaia, genetically modified to produce a green fluorescent protein, was used to ascertain the ability of Asaia to colonize specific organs of C. capitata. Our study lays the foundation for the development of control methods for C. capitata based on the use of symbiont bacteria.
Collapse
|
4
|
Impact of temperature on dengue and chikungunya transmission by the mosquito Aedes albopictus. Sci Rep 2022; 12:6973. [PMID: 35484193 PMCID: PMC9051100 DOI: 10.1038/s41598-022-10977-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2021] [Accepted: 03/16/2022] [Indexed: 12/28/2022] Open
Abstract
The mosquito Aedes albopictus is an invasive species first detected in Europe in Albania in 1979, and now established in 28 European countries. Temperature is a limiting factor in mosquito activities and in the transmission of associated arboviruses namely chikungunya (CHIKV) and dengue (DENV). Since 2007, local transmissions of CHIKV and DENV have been reported in mainland Europe, mainly in South Europe. Thus, the critical question is how far north transmission could occur. In this context, the Albanian infestation by Ae. albopictus is of interest because the species is present up to 1200 m of altitude; this allows using altitude as a proxy for latitude. Here we show that Ae. albopictus can transmit CHIKV at 28 °C as well as 20 °C, however, the transmission of DENV is only observed at 28 °C. We conclude that if temperature is the key environmental factor limiting transmission, then transmission of CHIKV, but not DENV is feasible in much of Europe.
Collapse
|
5
|
Behavioural Responses of Male Aedes albopictus to Different Volatile Chemical Compounds. INSECTS 2022; 13:insects13030290. [PMID: 35323588 PMCID: PMC8955809 DOI: 10.3390/insects13030290] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/13/2022] [Revised: 03/04/2022] [Accepted: 03/13/2022] [Indexed: 11/16/2022]
Abstract
Simple Summary Many studies have been performed to assess the effects of chemical compounds on mosquito behaviour. These studies almost exclusively involve only female mosquitoes as they can transmit disease pathogens, or at least, cause biting nuisance. Few studies have considered male mosquitoes. The identification of chemical substances that attract males can be very useful for trapping purposes, especially for monitoring the makeup of the male population during control programmes, such as those involving the release of sterile male mosquitoes. Twenty-eight chemical compounds from different chemical classes were evaluated using a dual-port olfactometer assay with at least three serial hexane dilutions against a hexane control. The compounds included known animal, plant and fungal volatiles, and the components of a putative Aedes aegypti pheromone. Many of the compounds were repellent for male mosquitoes, especially at the highest concentration. One compound, decanoic acid, acted as an attractant for males at an intermediate concentration. Decanoic acid did not elicit a significant response from female mosquitoes. Abstract The Asian tiger mosquito, Aedes albopictus, has become one of the most important invasive vectors for disease pathogens such as the viruses that cause chikungunya and dengue. Given the medical importance of this disease vector, a number of control programmes involving the use of the sterile insect technique (SIT) have been proposed. The identification of chemical compounds that attract males can be very useful for trapping purposes, especially for monitoring the makeup of the male population during control programmes, such as those involving the use of the SIT. Twenty-eight chemical compounds from different chemical classes were evaluated using a dual-port olfactometer assay. The compounds included known animal, fungal and plant host volatiles, and components of a putative Aedes aegypti pheromone. Many of the compounds were repellent for male mosquitoes, especially at the highest concentration. One compound, decanoic acid, acted as an attractant for males at an intermediate concentration. Decanoic acid did not elicit a significant response from female mosquitoes.
Collapse
|
6
|
Viviparity and habitat restrictions may influence the evolution of male reproductive genes in tsetse fly (Glossina) species. BMC Biol 2021; 19:211. [PMID: 34556101 PMCID: PMC8461966 DOI: 10.1186/s12915-021-01148-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Accepted: 09/06/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Glossina species (tsetse flies), the sole vectors of African trypanosomes, maintained along their long evolutionary history a unique reproductive strategy, adenotrophic viviparity. Viviparity reduces their reproductive rate and, as such, imposes strong selective pressures on males for reproductive success. These species live in sub-Saharan Africa, where the distributions of the main sub-genera Fusca, Morsitans, and Palpalis are restricted to forest, savannah, and riverine habitats, respectively. Here we aim at identifying the evolutionary patterns of the male reproductive genes of six species belonging to these three main sub-genera. We then interpreted the different patterns we found across the species in the light of viviparity and the specific habitat restrictions, which are known to shape reproductive behavior. RESULTS We used a comparative genomic approach to build consensus evolutionary trees that portray the selective pressure acting on the male reproductive genes in these lineages. Such trees reflect the long and divergent demographic history that led to an allopatric distribution of the Fusca, Morsitans, and Palpalis species groups. A dataset of over 1700 male reproductive genes remained conserved over the long evolutionary time scale (estimated at 26.7 million years) across the genomes of the six species. We suggest that this conservation may result from strong functional selective pressure on the male imposed by viviparity. It is noteworthy that more than half of these conserved genes are novel sequences that are unique to the Glossina genus and are candidates for selection in the different lineages. CONCLUSIONS Tsetse flies represent a model to interpret the evolution and differentiation of male reproductive biology under different, but complementary, perspectives. In the light of viviparity, we must take into account that these genes are constrained by a post-fertilization arena for genomic conflicts created by viviparity and absent in ovipositing species. This constraint implies a continuous antagonistic co-evolution between the parental genomes, thus accelerating inter-population post-zygotic isolation and, ultimately, favoring speciation. Ecological restrictions that affect reproductive behavior may further shape such antagonistic co-evolution.
Collapse
|
7
|
Identification of a Novel Brevibacillus laterosporus Strain With Insecticidal Activity Against Aedes albopictus Larvae. Front Microbiol 2021; 12:624014. [PMID: 33679643 PMCID: PMC7925996 DOI: 10.3389/fmicb.2021.624014] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Accepted: 01/19/2021] [Indexed: 11/13/2022] Open
Abstract
Bacterial species able to produce proteins that are toxic against insects have been discovered at the beginning of the last century. However, up to date only two of them have been used as pesticides in mosquito control strategies targeting larval breeding sites: Bacillus thuringensis var. israelensis and Lysinibacillus sphaericus. Aiming to expand the arsenal of biopesticides, bacterial cultures from 44 soil samples were assayed for their ability to kill larvae of Aedes albopictus. A method to select, grow and test the larvicidal capability of spore-forming bacteria from each soil sample was developed. This allowed identifying 13 soil samples containing strains capable of killing Ae. albopictus larvae. Among the active isolates, one strain with high toxicity was identified as Brevibacillus laterosporus by 16S rRNA gene sequencing and by morphological characterization using transmission electron microscopy. The new isolate showed a larvicidal activity significantly higher than the B. laterosporus LMG 15441 reference strain. Its genome was phylogenomically characterized and compared to the available Brevibacillus genomes. Thus, the new isolate can be considered as a candidate adjuvant to biopesticides formulations that would help preventing the insurgence of resistance.
Collapse
|
8
|
Bacillus subtilis as a host for mosquitocidal toxins production. Microb Biotechnol 2020; 13:1972-1982. [PMID: 32864888 PMCID: PMC7533320 DOI: 10.1111/1751-7915.13648] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Accepted: 07/23/2020] [Indexed: 02/05/2023] Open
Abstract
Aedes albopictus transmits several arboviral infections. In the absence of vaccines, control of mosquito populations is the only strategy to prevent vector-borne diseases. As part of the search for novel, biological and environmentally friendly strategies for vector control, the isolation of new bacterial species with mosquitocidal activity represents a promising approach. However, new bacterial isolates may be difficult to grow and genetically manipulate. To overcome these limits, here we set up a system allowing the expression of mosquitocidal bacterial toxins in the well-known genetic background of Bacillus subtilis. As a proof of this concept, the ability of B. subtilis to express individual or combinations of toxins of Bacillus thuringiensis israelensis (Bti) was studied. Different expression systems in which toxin gene expression was driven by IPTG-inducible, auto-inducible or toxin gene-specific promoters were developed. The larvicidal activity of the resulting B. subtilis strains against second-instar Ae. albopictus larvae allowed studying the activity of individual toxins or the synergistic interaction among Cry and Cyt toxins. The expression systems here presented lay the foundation for a better improved system to be used in the future to characterize the larvicidal activity of toxin genes from new environmental isolates.
Collapse
|
9
|
Transcriptional variation of sensory-related genes in natural populations of Aedes albopictus. BMC Genomics 2020; 21:547. [PMID: 32767966 PMCID: PMC7430840 DOI: 10.1186/s12864-020-06956-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Accepted: 07/27/2020] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND The Asian tiger mosquito, Aedes albopictus, is a highly dangerous invasive vector of numerous medically important arboviruses including dengue, chikungunya and Zika. In four decades it has spread from tropical Southeast Asia to many parts of the world in both tropical and temperate climes. The rapid invasion process of this mosquito is supported by its high ecological and genetic plasticity across different life history traits. Our aim was to investigate whether wild populations, both native and adventive, also display transcriptional genetic variability for functions that may impact their biology, behaviour and ability to transmit arboviruses, such as sensory perception. RESULTS Antennal transcriptome data were derived from mosquitoes from a native population from Ban Rai, Thailand and from three adventive Mediterranean populations: Athens, Greece and Arco and Trento from Italy. Clear inter-population differential transcriptional activity was observed in different gene categories related to sound perception, olfaction and viral infection. The greatest differences were detected between the native Thai and the Mediterranean populations. The two Italian populations were the most similar. Nearly one million quality filtered SNP loci were identified. CONCLUSION The ability to express this great inter-population transcriptional variability highlights, at the functional level, the remarkable genetic flexibility of this mosquito species. We can hypothesize that the differential expression of genes, including those involved in sensory perception, in different populations may enable Ae. albopictus to exploit different environments and hosts, thus contributing to its status as a global vector of arboviruses of public health importance. The large number of SNP loci present in these transcripts represents a useful addition to the arsenal of high-resolution molecular markers and a resource that can be used to detect selective pressure and adaptive changes that may have occurred during the colonization process.
Collapse
|
10
|
Vector competence of Aedes albopictus populations for chikungunya virus is shaped by their demographic history. Commun Biol 2020; 3:326. [PMID: 32581265 PMCID: PMC7314749 DOI: 10.1038/s42003-020-1046-6] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Accepted: 05/26/2020] [Indexed: 01/04/2023] Open
Abstract
The mosquito Aedes albopictus is one of the most dangerous invasive species. Its worldwide spread has created health concerns as it is a major vector of arboviruses of public health significance such as chikungunya (CHIKV). Dynamics of different genetic backgrounds and admixture events may have impacted competence for CHIKV in adventive populations. Using microsatellites, we infer the genetic structure of populations across the expansion areas that we then associate with their competence for different CHIKV genotypes. Here we show that the demographic history of Ae. albopictus populations is a consequence of rapid complex patterns of historical lineage diversification and divergence that influenced their competence for CHIKV. The history of adventive populations is associated with CHIKV genotypes in a genotype-by-genotype interaction that impacts their vector competence. Thus, knowledge of the demographic history and vector competence of invasive mosquitoes is pivotal for assessing the risk of arbovirus outbreaks in newly colonized areas.
Collapse
|
11
|
Structural and biochemical evaluation of Ceratitis capitata odorant-binding protein 22 affinity for odorants involved in intersex communication. INSECT MOLECULAR BIOLOGY 2019; 28:431-443. [PMID: 30548711 DOI: 10.1111/imb.12559] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
In insects, odorant-binding proteins (OBPs) connect the peripheral sensory system to receptors of olfactory organs. Medfly Ceratitis capitata CcapObp22 shows 37% identity and close phylogenetic affinities with Drosophila melanogaster OBP69a/pheromone-binding protein related protein 1. The CcapObp22 gene is transcribed in the antennae and maxillary palps, suggesting an active role in olfaction. Here, we recombinantly produced CcapObp22, obtaining a 13.5 kDa protein capable of binding multiple strongly hydrophobic terpene compounds, including medfly male pheromone components. The highest binding affinity [half maximal effective concentration (EC50) = 0.48 µM] was to (E,E)-α-farnesene, one of the most abundant compounds in the male pheromone blend. This odorant was used in cocrystallization experiments, yielding the structure of CcapOBP22. The monomeric structure shows the typical OBP folding, constituted by six α-helical elements interconnected by three disulphide bridges. A C-terminal seventh α-helix constitutes the wall of a deep, L-shaped hydrophobic cavity. Analysis of the electron density in this cavity suggested trapping of farnesene in the crystal structure, although with partial occupancy. Superposition of the CcapOBP22 structure with related seven-helical OBPs highlights striking similarity in the organization of the C-terminal segment of these proteins. Collectively, our molecular and physiological data on medfly CcapOBP22 suggest its involvement in intersex olfactory communication.
Collapse
|
12
|
The Nix locus on the male-specific homologue of chromosome 1 in Aedes albopictus is a strong candidate for a male-determining factor. Parasit Vectors 2018; 11:647. [PMID: 30583734 PMCID: PMC6304787 DOI: 10.1186/s13071-018-3215-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Background Global concern over the rapid expansion of the Asian tiger mosquito, Aedes albopictus, and its vector competence has highlighted an urgent need to improve currently available population control methods, like the Sterile Insect Technique. Knowledge of the sex determination cascade is a prerequisite for the development of early-stage sexing systems. To this end, we have characterised the putative sex determination gene, Nix, in this species. In Aedes species the chromosome complement consists of three pairs of chromosomes. The sex determination alleles are linked to the smallest homomorphic chromosome. Results We identified the male-specific chromosome 1 of Ae. albopictus that carries the putative male-determining gene Nix. We have also characterised the complete genomic sequence of the Nix gene which is composed of two exons and a short intron. The gene displays different levels of intron retention during development. Comparison of DNA sequences covering most of the Nix gene from individuals across the species range revealed no polymorphism. Conclusions Our characterisation of the Nix gene in Ae. albopictus represents an initial step in the analysis of the sex determination cascade in this species. We found evidence of intron retention (IR) in Nix. IR might play a role in regulating the expression of Nix during development. Our results provide the basis for the development of new genetic control strategies. Electronic supplementary material The online version of this article (10.1186/s13071-018-3215-8) contains supplementary material, which is available to authorized users.
Collapse
|
13
|
161. A crowd-knowledge-based analysis of DVHs in SBRT: First steps towards a national virtual audit. Phys Med 2018. [DOI: 10.1016/j.ejmp.2018.04.172] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
|
14
|
Larval Diet Affects Male Pheromone Blend in a Laboratory Strain of the Medfly, Ceratitis capitata (Diptera: Tephritidae). J Chem Ecol 2018; 44:339-353. [PMID: 29504084 DOI: 10.1007/s10886-018-0939-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Revised: 02/02/2018] [Accepted: 02/18/2018] [Indexed: 11/29/2022]
Abstract
The Mediterranean fruit fly (medfly) Ceratitis capitata is a polyphagous pest of fruits and crops with a worldwide distribution. Its ability to use different larval hosts may have multiple effects, including impacts on adult reproductive biology. The male sex pheromone, which plays a key role in attracting both other males to lekking arenas and females for mating, is a mixture of chemical compounds including esters, acids, alkanes and terpenes known to differ between laboratory strains and wild-type populations. The relationship between larval diet and adult pheromone composition remains unexplored. Here, we investigated the effect of larval diet, including laboratory media and fresh fruits, on the composition of the male pheromone mixture. Using Headspace Solid Phase Microextraction we collected the pheromone emitted by males reared as larvae on different substrates and found both qualitative and quantitative differences. A number of alkanes appeared to be typical of the pheromone of males reared on wheat bran-based larval medium, and these may be cuticular hydrocarbons involved in chemical communication. We also detected differences in pheromone composition related to adult male age, suggesting that variations in hormonal levels and/or adult diet could also play a role in determining the chemical profile emitted. Our findings highlight the plasticity of dietary responses of C. capitata, which may be important in determining the interactions of this pest with the environment and with conspecifics. These results also have applied relevance to increase the mating competitiveness of mass-reared C. capitata used in Sterile Insect Technique programs.
Collapse
|
15
|
The third International Workshop on Aedes albopictus: building scientific alliances in the fight against the globally invasive Asian tiger mosquito. Pathog Glob Health 2017. [DOI: 10.1080/20477724.2017.1333560] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
|
16
|
Erratum to: The whole genome sequence of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), reveals insights into the biology and adaptive evolution of a highly invasive pest species. Genome Biol 2017; 18:11. [PMID: 28100280 PMCID: PMC5241912 DOI: 10.1186/s13059-017-1155-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2017] [Accepted: 01/12/2017] [Indexed: 12/03/2022] Open
|
17
|
Genetic evidence for a worldwide chaotic dispersion pattern of the arbovirus vector, Aedes albopictus. PLoS Negl Trop Dis 2017; 11:e0005332. [PMID: 28135274 PMCID: PMC5300280 DOI: 10.1371/journal.pntd.0005332] [Citation(s) in RCA: 73] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2016] [Revised: 02/09/2017] [Accepted: 01/16/2017] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND Invasive species represent a global concern for their rapid spread and the possibility of infectious disease transmission. This is the case of the global invader Aedes albopictus, the Asian tiger mosquito. This species is a vector of medically important arboviruses, notably chikungunya (CHIKV), dengue (DENV) and Zika (ZIKV). The reconstruction of the complex colonization pattern of this mosquito has great potential for mitigating its spread and, consequently, disease risks. METHODOLOGY/PRINCIPAL FINDINGS Classical population genetics analyses and Approximate Bayesian Computation (ABC) approaches were combined to disentangle the demographic history of Aedes albopictus populations from representative countries in the Southeast Asian native range and in the recent and more recently colonized areas. In Southeast Asia, the low differentiation and the high co-ancestry values identified among China, Thailand and Japan indicate that, in the native range, these populations maintain high genetic connectivity, revealing their ancestral common origin. China appears to be the oldest population. Outside Southeast Asia, the invasion process in La Réunion, America and the Mediterranean Basin is primarily supported by a chaotic propagule distribution, which cooperates in maintaining a relatively high genetic diversity within the adventive populations. CONCLUSIONS/SIGNIFICANCE From our data, it appears that independent and also trans-continental introductions of Ae. albopictus may have facilitated the rapid establishment of adventive populations through admixture of unrelated genomes. As a consequence, a great amount of intra-population variability has been detected, and it is likely that this variability may extend to the genetic mechanisms controlling vector competence. Thus, in the context of the invasion process of this mosquito, it is possible that both population ancestry and admixture contribute to create the conditions for the efficient transmission of arboviruses and for outbreak establishment.
Collapse
|
18
|
Sperm-less males modulate female behaviour in Ceratitis capitata (Diptera: Tephritidae). INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2016; 79:13-26. [PMID: 27720923 DOI: 10.1016/j.ibmb.2016.10.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2015] [Revised: 09/22/2016] [Accepted: 10/04/2016] [Indexed: 06/06/2023]
Abstract
In the Mediterranean fruit fly, Ceratitis capitata (Wiedemann)(Diptera: Tephritidae), mating has a strong impact on female biology, leading to a decrease in sexual receptivity and increased oviposition and fecundity. Previous studies suggest that sperm transfer may play a role in inducing these behavioural changes. Here we report the identification of a medfly innexin gene, Cc-inx5, whose expression is limited to the germ-line of both sexes. Through RNA interference of this gene, we generated males without testes and, consequently, sperm, but apparently retaining all the other reproductive organs intact. These sperm-less males were able to mate and, like their wild-type counterparts, to induce in their partners increased oviposition rates and refractoriness to remating. Interestingly, matings to sperm-less males results in oviposition rates higher than those induced by copulation with control males. In addition, the observed female post-mating behavioural changes were congruent with changes in transcript abundance of genes known to be regulated by mating in this species. Our results suggest that sperm transfer is not necessary to reduce female sexual receptivity and to increase oviposition and fecundity. These data pave the way to a better understanding of the role/s of seminal components in modulating female post-mating responses. In the long term, this knowledge will be the basis for the development of novel approaches for the manipulation of female fertility, and, consequently, innovative tools to be applied to medfly control strategies in the field.
Collapse
|
19
|
The Worldwide Spread of the Tiger Mosquito as Revealed by Mitogenome Haplogroup Diversity. Front Genet 2016; 7:208. [PMID: 27933090 PMCID: PMC5120106 DOI: 10.3389/fgene.2016.00208] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2016] [Accepted: 11/09/2016] [Indexed: 11/13/2022] Open
Abstract
In the last 40 years, the Asian tiger mosquito Aedes albopictus, indigenous to East Asia, has colonized every continent except Antarctica. Its spread is a major public health concern, given that this species is a competent vector for numerous arboviruses, including those causing dengue, chikungunya, West Nile, and the recently emerged Zika fever. To acquire more information on the ancestral source(s) of adventive populations and the overall diffusion process from its native range, we analyzed the mitogenome variation of 27 individuals from representative populations of Asia, the Americas, and Europe. Phylogenetic analyses revealed five haplogroups in Asia, but population surveys appear to indicate that only three of these (A1a1, A1a2, and A1b) were involved in the recent worldwide spread. We also found out that a derived lineage (A1a1a1) within A1a1, which is now common in Italy, most likely arose in North America from an ancestral Japanese source. These different genetic sources now coexist in many of the recently colonized areas, thus probably creating novel genomic combinations which might be one of the causes of the apparently growing ability of A. albopictus to expand its geographical range.
Collapse
|
20
|
The whole genome sequence of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), reveals insights into the biology and adaptive evolution of a highly invasive pest species. Genome Biol 2016; 17:192. [PMID: 27659211 PMCID: PMC5034548 DOI: 10.1186/s13059-016-1049-2] [Citation(s) in RCA: 101] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2016] [Accepted: 08/26/2016] [Indexed: 01/01/2023] Open
Abstract
Background The Mediterranean fruit fly (medfly), Ceratitis capitata, is a major destructive insect pest due to its broad host range, which includes hundreds of fruits and vegetables. It exhibits a unique ability to invade and adapt to ecological niches throughout tropical and subtropical regions of the world, though medfly infestations have been prevented and controlled by the sterile insect technique (SIT) as part of integrated pest management programs (IPMs). The genetic analysis and manipulation of medfly has been subject to intensive study in an effort to improve SIT efficacy and other aspects of IPM control. Results The 479 Mb medfly genome is sequenced from adult flies from lines inbred for 20 generations. A high-quality assembly is achieved having a contig N50 of 45.7 kb and scaffold N50 of 4.06 Mb. In-depth curation of more than 1800 messenger RNAs shows specific gene expansions that can be related to invasiveness and host adaptation, including gene families for chemoreception, toxin and insecticide metabolism, cuticle proteins, opsins, and aquaporins. We identify genes relevant to IPM control, including those required to improve SIT. Conclusions The medfly genome sequence provides critical insights into the biology of one of the most serious and widespread agricultural pests. This knowledge should significantly advance the means of controlling the size and invasive potential of medfly populations. Its close relationship to Drosophila, and other insect species important to agriculture and human health, will further comparative functional and structural studies of insect genomes that should broaden our understanding of gene family evolution. Electronic supplementary material The online version of this article (doi:10.1186/s13059-016-1049-2) contains supplementary material, which is available to authorized users.
Collapse
|
21
|
Relevant genetic differentiation among Brazilian populations of Anastrepha fraterculus (Diptera, Tephritidae). Zookeys 2015:157-73. [PMID: 26798258 PMCID: PMC4714068 DOI: 10.3897/zookeys.540.6713] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2015] [Accepted: 10/05/2015] [Indexed: 11/12/2022] Open
Abstract
We used a population genetic approach to detect the presence of genetic diversity among six populations of Anastrephafraterculus across Brazil. To this aim, we used Simple Sequence Repeat (SSR) markers, which may capture the presence of differentiative processes across the genome in distinct populations. Spatial analyses of molecular variance were used to identify groups of populations that are both genetically and geographically homogeneous while also being maximally differentiated from each other. The spatial analysis of genetic diversity indicates that the levels of diversity among the six populations vary significantly on an eco-geographical basis. Particularly, altitude seems to represent a differentiating adaptation, as the main genetic differentiation is detected between the two populations present at higher altitudes and the other four populations at sea level. The data, together with the outcomes from different cluster analyses, identify a genetic diversity pattern that overlaps with the distribution of the known morphotypes in the Brazilian area.
Collapse
|
22
|
Abstract
The draft genome sequence of Italian specimens of the Asian tiger mosquito Aedes (Stegomyia) albopictus (Diptera: Culicidae) was determined using a standard NGS (next generation sequencing) approach. The size of the assembled genome is comparable to that of Aedes aegypti; the two mosquitoes are also similar as far as the high content of repetitive DNA is concerned, most of which is made up of transposable elements. Although, based on BUSCO (Benchmarking Universal Single-Copy Orthologues) analysis, the genome assembly reported here contains more than 99% of protein-coding genes, several of those are expected to be represented in the assembly in a fragmented state. We also present here the annotation of several families of genes (tRNA genes, miRNA genes, the sialome, genes involved in chromatin condensation, sex determination genes, odorant binding proteins and odorant receptors). These analyses confirm that the assembly can be used for the study of the biology of this invasive vector of disease.
Collapse
|
23
|
Molecular markers for analyses of intraspecific genetic diversity in the Asian Tiger mosquito, Aedes albopictus. Parasit Vectors 2015; 8:188. [PMID: 25890257 PMCID: PMC4404008 DOI: 10.1186/s13071-015-0794-5] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Accepted: 03/10/2015] [Indexed: 02/08/2023] Open
Abstract
Background The dramatic worldwide expansion of Aedes albopictus (the Asian tiger mosquito) and its vector competence for numerous arboviruses represent a growing threat to public health security. Molecular markers are crucially needed for tracking the rapid spread of this mosquito and to obtain a deeper knowledge of population structure. This is a fundamental requirement for the development of strict monitoring protocols and for the improvement of sustainable control measures. Methods Wild population samples from putative source areas and from newly colonised regions were analysed for variability at the ribosomal DNA internal transcribed spacer 2 (ITS2). Moreover, a new set of 23 microsatellite markers (SSR) was developed. Sixteen of these SSRs were tested in an ancestral (Thailand) and two adventive Italian populations. Results Seventy-six ITS2 sequences representing 52 unique haplotypes were identified, and AMOVA indicated that most of their variation occurred within individuals (74.36%), while only about 8% was detected among populations. Spatial analyses of molecular variance revealed that haplotype genetic similarity was not related to the geographic proximity of populations and the haplotype phylogeny clearly indicated that highly related sequences were distributed across populations from different geographical regions. The SSR markers displayed a high level of polymorphism both in the ancestral and in adventive populations, and FST estimates suggested the absence of great differentiation. The ancestral nature of the Thai population was corroborated by its higher level of variability. Conclusions The two types of genetic markers here implemented revealed the distribution of genetic diversity within and between populations and provide clues on the dispersion dynamics of this species. It appears that the diffusion of this mosquito does not conform to a progressive expansion from the native Asian source area, but to a relatively recent and chaotic propagule distribution mediated by human activities. Under this scenario, multiple introductions and admixture events probably play an important role in maintaining the genetic diversity and in avoiding bottleneck effects. The polymorphic SSR markers here implemented will provide an important tool for reconstructing the routes of invasion followed by this mosquito.
Collapse
|
24
|
Microsatellite markers from the 'South American fruit fly' Anastrepha fraterculus: a valuable tool for population genetic analysis and SIT applications. BMC Genet 2014; 15 Suppl 2:S13. [PMID: 25471285 PMCID: PMC4255783 DOI: 10.1186/1471-2156-15-s2-s13] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Background Anastrepha fraterculus Wiedemann is a horticultural pest which causes significant economic losses in the fruit-producing areas of the American continent and limits the access of products to international markets. The use of environmentally friendly control strategies against this pest is constrained due to the limited knowledge of its population structure. Results We developed microsatellite markers for A. fraterculus from four genomic libraries, which were enriched in CA, CAA, GA and CAT microsatellite motifs. Fifty microsatellite regions were evaluated and 14 loci were selected for population genetics studies. Genotypes of 122 individuals sampled from four A. fraterculus populations were analyzed. The level of polymorphism ranged from three to 13 alleles per locus and the mean expected heterozygosity ranged from 0.60 to 0.64. Comparison between allelic and genotypic frequencies showed significant differences among all pairs of populations. Conclusions This novel set of microsatellite markers provides valuable information for the description of genetic variability and population structure of wild populations and laboratory strains of A. fraterculus. This information will be used to identify and characterize candidate strains suitable to implement effective pest control strategies and might represent a first step towards having a more comprehensive knowledge about the genetics of this pest.
Collapse
|
25
|
The oriental fruitfly Bactrocera dorsalis s.s. in East Asia: disentangling the different forces promoting the invasion and shaping the genetic make-up of populations. Genetica 2014; 142:201-13. [PMID: 24816716 DOI: 10.1007/s10709-014-9767-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2013] [Accepted: 05/02/2014] [Indexed: 11/30/2022]
Abstract
The Oriental fruit fly, Bactrocera dorsalis sensu stricto, is one of the most economically destructive pests of fruits and vegetables especially in East Asia. Based on its phytophagous life style, this species dispersed with the diffusion and implementation of agriculture, while globalization allowed it to establish adventive populations in different tropical and subtropical areas of the world. We used nine SSR loci over twelve samples collected across East Asia, i.e. an area that, in relatively few years, has become a theatre of intensive agriculture and a lively fruit trade. Our aim is to disentangle the different forces that have affected the invasion pattern and shaped the genetic make-up of populations of this fruit fly. Our data suggest that the considered samples probably represent well established populations in terms of genetic variability and population structuring. The human influence on the genetic shape of populations and diffusion is evident, but factors such as breeding/habitat size and life history traits of the species may have determined the post introduction phases and expansion. In East Asia the origin of diffusion can most probably be allocated in the oriental coastal provinces of China, from where this fruit fly spread into Southeast Asia. The spread of this species deserves attention for the development and implementation of risk assessment and control measures.
Collapse
|
26
|
Identification of pheromone components and their binding affinity to the odorant binding protein CcapOBP83a-2 of the Mediterranean fruit fly, Ceratitis capitata. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2014; 48:51-62. [PMID: 24607850 PMCID: PMC4003389 DOI: 10.1016/j.ibmb.2014.02.005] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2013] [Revised: 02/17/2014] [Accepted: 02/18/2014] [Indexed: 05/27/2023]
Abstract
The Mediterranean fruit fly (or medfly), Ceratitis capitata (Wiedemann; Diptera: Tephritidae), is a serious pest of agriculture worldwide, displaying a very wide larval host range with more than 250 different species of fruit and vegetables. Olfaction plays a key role in the invasive potential of this species. Unfortunately, the pheromone communication system of the medfly is complex and still not well established. In this study, we report the isolation of chemicals emitted by sexually mature individuals during the "calling" period and the electrophysiological responses that these compounds elicit on the antennae of male and female flies. Fifteen compounds with electrophysiological activity were isolated and identified in male emissions by gas chromatography coupled to electroantennography (GC-EAG). Within the group of 15 identified compounds, 11 elicited a response in antennae of both sexes, whilst 4 elicited a response only in female antennae. The binding affinity of these compounds, plus 4 additional compounds known to be behaviourally active from other studies, was measured using C. capitata OBP, CcapOBP83a-2. This OBP has a high homology to Drosophila melanogaster OBPs OS-E and OS-F, which are associated with trichoid sensilla and co-expressed with the well-studied Drosophila pheromone binding protein LUSH. The results provide evidence of involvement of CcapOBP83a-2 in the medfly's odorant perception and its wider specificity for (E,E)-α-farnesene, one of the five major compounds in medfly male pheromone emission. This represents the first step in the clarification of the C. capitata and pheromone reception pathway, and a starting point for further studies aimed towards the creation of new powerful attractants or repellents applicable in the actual control strategies.
Collapse
|
27
|
Sniffing out chemosensory genes from the Mediterranean fruit fly, Ceratitis capitata. PLoS One 2014; 9:e85523. [PMID: 24416419 PMCID: PMC3885724 DOI: 10.1371/journal.pone.0085523] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2013] [Accepted: 11/27/2013] [Indexed: 11/18/2022] Open
Abstract
The Mediterranean fruit fly, Ceratitis capitata (medfly), is an extremely invasive agricultural pest due to its extremely wide host range and its ability to adapt to a broad range of climatic conditions and habitats. Chemosensory behaviour plays an important role in many crucial stages in the life of this insect, such as the detection of pheromone cues during mate pursuit and odorants during host plant localisation. Thus, the analysis of the chemosensory gene repertoire is an important step for the interpretation of the biology of this species and consequently its invasive potential. Moreover, these genes may represent ideal targets for the development of novel, effective control methods and pest population monitoring systems. Expressed sequence tag libraries from C. capitata adult heads, embryos, male accessory glands and testes were screened for sequences encoding putative odorant binding proteins (OBPs). A total of seventeen putative OBP transcripts were identified, corresponding to 13 Classic, three Minus-C and one Plus-C subfamily OBPs. The tissue distributions of the OBP transcripts were assessed by RT-PCR and a subset of five genes with predicted proteins sharing high sequence similarities and close phylogenetic affinities to Drosophila melanogaster pheromone binding protein related proteins (PBPRPs) were characterised in greater detail. Real Time quantitative PCR was used to assess the effects of maturation, mating and time of day on the transcript abundances of the putative PBPRP genes in the principal olfactory organs, the antennae, in males and females. The results of the present study have facilitated the annotation of OBP genes in the recently released medfly genome sequence and represent a significant contribution to the characterisation of the medfly chemosensory repertoire. The identification of these medfly OBPs/PBPRPs permitted evolutionary and functional comparisons with homologous sequences from other tephritids of the genera Bactrocera and Rhagoletis.
Collapse
|
28
|
The invasive mosquito species Aedes albopictus: current knowledge and future perspectives. Trends Parasitol 2013; 29:460-8. [PMID: 23916878 PMCID: PMC3777778 DOI: 10.1016/j.pt.2013.07.003] [Citation(s) in RCA: 363] [Impact Index Per Article: 33.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2013] [Revised: 07/05/2013] [Accepted: 07/08/2013] [Indexed: 01/27/2023]
Abstract
One of the most dynamic events in public health is being mediated by the global spread of the invasive mosquito Aedes albopictus. Its rapid expansion and vectorial capacity for various arboviruses affect an increasingly larger proportion of the world population. Responses to the challenges of controlling this vector are expected to be enhanced by an increased knowledge of its biology, ecology, and vector competence. Details of population genetics and structure will allow following, and possibly predicting, the geographical and temporal dynamics of its expansion, and will inform the practical operations of control programs. Experts are now coming together to describe the history, characterize the present circumstances, and collaborate on future efforts to understand and mitigate this emerging public health threat.
Collapse
|
29
|
Transcriptional profiles of mating-responsive genes from testes and male accessory glands of the Mediterranean fruit fly, Ceratitis capitata. PLoS One 2012; 7:e46812. [PMID: 23071645 PMCID: PMC3469604 DOI: 10.1371/journal.pone.0046812] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2012] [Accepted: 09/05/2012] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Insect seminal fluid is a complex mixture of proteins, carbohydrates and lipids, produced in the male reproductive tract. This seminal fluid is transferred together with the spermatozoa during mating and induces post-mating changes in the female. Molecular characterization of seminal fluid proteins in the Mediterranean fruit fly, Ceratitis capitata, is limited, although studies suggest that some of these proteins are biologically active. METHODOLOGY/PRINCIPAL FINDINGS We report on the functional annotation of 5914 high quality expressed sequence tags (ESTs) from the testes and male accessory glands, to identify transcripts encoding putative secreted peptides that might elicit post-mating responses in females. The ESTs were assembled into 3344 contigs, of which over 33% produced no hits against the nr database, and thus may represent novel or rapidly evolving sequences. Extraction of the coding sequences resulted in a total of 3371 putative peptides. The annotated dataset is available as a hyperlinked spreadsheet. Four hundred peptides were identified with putative secretory activity, including odorant binding proteins, protease inhibitor domain-containing peptides, antigen 5 proteins, mucins, and immunity-related sequences. Quantitative RT-PCR-based analyses of a subset of putative secretory protein-encoding transcripts from accessory glands indicated changes in their abundance after one or more copulations when compared to virgin males of the same age. These changes in abundance, particularly evident after the third mating, may be related to the requirement to replenish proteins to be transferred to the female. CONCLUSIONS/SIGNIFICANCE We have developed the first large-scale dataset for novel studies on functions and processes associated with the reproductive biology of Ceratitis capitata. The identified genes may help study genome evolution, in light of the high adaptive potential of the medfly. In addition, studies of male recovery dynamics in terms of accessory gland gene expression profiles and correlated remating inhibition mechanisms may permit the improvement of pest management approaches.
Collapse
|
30
|
A new threat looming over the Mediterranean basin: emergence of viral diseases transmitted by Aedes albopictus mosquitoes. PLoS Negl Trop Dis 2012; 6:e1836. [PMID: 23029593 PMCID: PMC3459824 DOI: 10.1371/journal.pntd.0001836] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
|
31
|
Transcriptome profiling of sexual maturation and mating in the Mediterranean fruit fly, Ceratitis capitata. PLoS One 2012; 7:e30857. [PMID: 22303464 PMCID: PMC3267753 DOI: 10.1371/journal.pone.0030857] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2011] [Accepted: 12/22/2011] [Indexed: 12/26/2022] Open
Abstract
Sexual maturation and mating in insects are generally accompanied by major physiological and behavioural changes. Many of these changes are related to the need to locate a mate and subsequently, in the case of females, to switch from mate searching to oviposition behaviour. The prodigious reproductive capacity of the Mediterranean fruit fly, Ceratitis capitata, is one of the factors that has led to its success as an invasive pest species. To identify the molecular changes related to maturation and mating status in male and female medfly, a microarray-based gene expression approach was used to compare the head transcriptomes of sexually immature, mature virgin, and mated individuals. Attention was focused on the changes in abundance of transcripts related to reproduction, behaviour, sensory perception of chemical stimulus, and immune system processes. Broad transcriptional changes were recorded during female maturation, while post-mating transcriptional changes in females were, by contrast, modest. In male medfly, transcriptional changes were consistent both during maturation and as a consequence of mating. Of particular note was the lack of the mating-induced immune responses that have been recorded for Drosophila melanogaster, that may be due to the different reproductive strategies of these species. This study, in addition to increasing our understanding of the molecular machinery behind maturation and mating in the medfly, has identified important gene targets that might be useful in the future management of this pest.
Collapse
|
32
|
Interchromosomal duplications on the Bactrocera oleae Y chromosome imply a distinct evolutionary origin of the sex chromosomes compared to Drosophila. PLoS One 2011; 6:e17747. [PMID: 21408187 PMCID: PMC3049792 DOI: 10.1371/journal.pone.0017747] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2010] [Accepted: 02/11/2011] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Diptera have an extraordinary variety of sex determination mechanisms, and Drosophila melanogaster is the paradigm for this group. However, the Drosophila sex determination pathway is only partially conserved and the family Tephritidae affords an interesting example. The tephritid Y chromosome is postulated to be necessary to determine male development. Characterization of Y sequences, apart from elucidating the nature of the male determining factor, is also important to understand the evolutionary history of sex chromosomes within the Tephritidae. We studied the Y sequences from the olive fly, Bactrocera oleae. Its Y chromosome is minute and highly heterochromatic, and displays high heteromorphism with the X chromosome. METHODOLOGY/PRINCIPAL FINDINGS A combined Representational Difference Analysis (RDA) and fluorescence in-situ hybridization (FISH) approach was used to investigate the Y chromosome to derive information on its sequence content. The Y chromosome is strewn with repetitive DNA sequences, the majority of which are also interdispersed in the pericentromeric regions of the autosomes. The Y chromosome appears to have accumulated small and large repetitive interchromosomal duplications. The large interchromosomal duplications harbour an importin-4-like gene fragment. Apart from these importin-4-like sequences, the other Y repetitive sequences are not shared with the X chromosome, suggesting molecular differentiation of these two chromosomes. Moreover, as the identified Y sequences were not detected on the Y chromosomes of closely related tephritids, we can infer divergence in the repetitive nature of their sequence contents. CONCLUSIONS/SIGNIFICANCE The identification of Y-linked sequences may tell us much about the repetitive nature, the origin and the evolution of Y chromosomes. We hypothesize how these repetitive sequences accumulated and were maintained on the Y chromosome during its evolutionary history. Our data reinforce the idea that the sex chromosomes of the Tephritidae may have distinct evolutionary origins with respect to those of the Drosophilidae and other Dipteran families.
Collapse
|
33
|
Sperm storage and use in polyandrous females of the globally invasive fruitfly, Ceratitis capitata. JOURNAL OF INSECT PHYSIOLOGY 2010; 56:1542-1551. [PMID: 20466005 DOI: 10.1016/j.jinsphys.2010.05.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2010] [Revised: 05/04/2010] [Accepted: 05/04/2010] [Indexed: 05/29/2023]
Abstract
The medfly, Ceratitis capitata, is an invasive species in which polyandry, associated with sperm precedence, is a common behaviour in the wild. In this species, characterized by internal fertilization, we disclose how the sperm from two males are stored in the female storage organs and how they are used in terms of paternity outcome. The experiments were designed to furnish comparable and unbiased estimates of sperm numbers and progeny in twice-mated females. Results are incorporated in a model through which it is possible to relate the amount of stored sperm with the progeny of twice-mated females. The results show that polyandrous medfly females conserve equal amounts of sperm from the two males to fertilize their eggs. However, we observed a clear advantage of the second male's sperm in siring progeny, which interestingly decreases in favor of the first male as ovipositions progress. The results enable us to exclude differential sperm mortality and suggest that it is the mechanics governing the storage organs which causes the initial, but decreasing second male sperm precedence during the female reproductive life. These outcomes allow us to correlate sperm use in polyandrous females with the mating strategies and invasiveness of this fly.
Collapse
|
34
|
Safe and fit genetically modified insects for pest control: from lab to field applications. Genetica 2010; 139:41-52. [PMID: 20725766 DOI: 10.1007/s10709-010-9483-7] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2009] [Accepted: 08/07/2010] [Indexed: 01/10/2023]
Abstract
Insect transgenesis is continuously being improved to increase the efficacy of population suppression and replacement strategies directed to the control of insect species of economic and sanitary interest. An essential prerequisite for the success of both pest control applications is that the fitness of the transformant individuals is not impaired, so that, once released in the field, they can efficiently compete with or even out-compete their wild-type counterparts for matings in order to reduce the population size, or to spread desirable genes into the target population. Recent research has shown that the production of fit and competitive transformants can now be achieved and that transgenes may not necessarily confer a fitness cost. In this article we review the most recent published results of the fitness assessment of different transgenic insect lines and underline the necessity to fulfill key requirements of ecological safety. Fitness evaluation studies performed in field cages and medium/large-scale rearing will validate the present encouraging laboratory results, giving an indication of the performance of the transgenic insect genotype after release in pest control programmes.
Collapse
|
35
|
Sex and the single embryo: early deveiopment in the Mediterranean fruit fly, Ceratitis capitata. BMC DEVELOPMENTAL BIOLOGY 2010; 10:12. [PMID: 20102629 PMCID: PMC2826288 DOI: 10.1186/1471-213x-10-12] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/24/2009] [Accepted: 01/26/2010] [Indexed: 01/17/2023]
Abstract
Background In embryos the maternal-to-zygotic transition (MTZ) integrates post-transcriptional regulation of maternal transcripts with transcriptional activation of the zygotic genome. Although the molecular mechanisms underlying this event are being clarified in Drosophila melanogaster, little is know about the embryogenic processes in other insect species. The recent publication of expressed sequence tags (ESTs) from embryos of the global pest species Ceratitis capitata (medfly) has enabled the investigation of embryogenesis in this species and has allowed a comparison of the embryogenic processes in these two related dipteran species, C. capitata and D. melanogaster, that shared a common ancestor 80-100 mya. Results Using a novel PCR-based sexing method, which takes advantage of a putative LTR retrotransposon MITE insertion on the medfly Y chromosome, the transcriptomes of individual early male and female embryos were analysed using RT-PCR. This study is focused on two crucial aspects of the onset of embryonic development: sex determination and cellular blastoderm formation. Together with the three known medfly genes (Cctransformer, Cctransformer2 and Ccdoublesex), the expression patterns of other medfly genes that are similar to the D. melanogaster sex-determination genes (sisterlessA, groucho, deadpan, Sex-lethal, female lethal d, sans fille and intersex) and four cellular blastoderm formation genes (Rho1, spaghetti squash, slow-as-molasses and serendipity-α) were analyzed, allowing us to sketch a preliminary outline of the embryonic process in the medfly. Furthermore, a putative homologue of the Zelda gene has been considered, which in D. melanogaster encodes a DNA-binding factor responsible for the maternal-to-zygotic transition. Conclusions Our novel sexing method facilitates the study of i) when the MTZ transition occurs in males and females of C. capitata, ii) when and how the maternal information of "female-development" is reprogrammed in the embryos and iii) similarities and differences in the regulation of gene expression in C. capitata and D. melanogaster. We suggest a new model for the onset of the sex determination cascade in the medfly: the maternally inherited Cctra transcripts in the female embryos are insufficient to produce enough active protein to inhibit the male mode of Cctra splicing. The slow rate of development and the inefficiency of the splicing mechanism in the pre-cellular blastoderm facilitates the male-determining factor (M) activity, which probably acts by inhibiting CcTRA protein activity.
Collapse
|
36
|
Uncovering the tracks of a recent and rapid invasion: the case of the fruit fly pest Bactrocera invadens (Diptera: Tephritidae) in Africa. Mol Ecol 2009; 18:4798-810. [PMID: 19821903 DOI: 10.1111/j.1365-294x.2009.04391.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Phytophagous insects of the genus Bactrocera are among the most economically important invasive fruit fly pests. In 2003, an unknown Bactrocera species was found in Kenya. First identified as an 'aberrant form' of the Asian B. dorsalis complex, it was later recognized as a new species, Bactrocera invadens. Within 2 years of its discovery, the species was recorded in several African countries, becoming an important quarantine pest. As this invasive fly was discovered only recently, no data are available on its invasion pattern in Africa. This pilot study attempts to infer from genetic data the dynamic aspects of the African invasion of this pest. Using microsatellite markers, we evaluated the level of genetic diversity and the extent of common ancestry among several African populations collected across the invaded areas. A sample from the Asian Sri Lankan population was analysed to confirm the Asian origin of this pest. Genetic data cast no doubt that Sri Lanka belongs to the native range, but only a small percentage of its genotypes can be found in Africa. African populations display relatively high levels of genetic diversity associated with limited geographical structure and no genetic footprints of bottlenecks. These features are indicative of processes of rapid population growth and expansion with possible multiple introductions. In the span of relatively few years, the African invasion registered the presence of at least two uncorrelated outbreaks, both starting from the East. The results of the analyses support that invasion started in East Africa, where B. invadens was initially isolated.
Collapse
|
37
|
|
38
|
Gene discovery in an invasive tephritid model pest species, the Mediterranean fruit fly, Ceratitis capitata. BMC Genomics 2008; 9:243. [PMID: 18500975 PMCID: PMC2427042 DOI: 10.1186/1471-2164-9-243] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2008] [Accepted: 05/23/2008] [Indexed: 12/02/2022] Open
Abstract
Background The medfly, Ceratitis capitata, is a highly invasive agricultural pest that has become a model insect for the development of biological control programs. Despite research into the behavior and classical and population genetics of this organism, the quantity of sequence data available is limited. We have utilized an expressed sequence tag (EST) approach to obtain detailed information on transcriptome signatures that relate to a variety of physiological systems in the medfly; this information emphasizes on reproduction, sex determination, and chemosensory perception, since the study was based on normalized cDNA libraries from embryos and adult heads. Results A total of 21,253 high-quality ESTs were obtained from the embryo and head libraries. Clustering analyses performed separately for each library resulted in 5201 embryo and 6684 head transcripts. Considering an estimated 19% overlap in the transcriptomes of the two libraries, they represent about 9614 unique transcripts involved in a wide range of biological processes and molecular functions. Of particular interest are the sequences that share homology with Drosophila genes involved in sex determination, olfaction, and reproductive behavior. The medfly transformer2 (tra2) homolog was identified among the embryonic sequences, and its genomic organization and expression were characterized. Conclusion The sequences obtained in this study represent the first major dataset of expressed genes in a tephritid species of agricultural importance. This resource provides essential information to support the investigation of numerous questions regarding the biology of the medfly and other related species and also constitutes an invaluable tool for the annotation of complete genome sequences. Our study has revealed intriguing findings regarding the transcript regulation of tra2 and other sex determination genes, as well as insights into the comparative genomics of genes implicated in chemosensory reception and reproduction.
Collapse
|
39
|
Highly similar piggyBac transposase-like sequences from various Bactrocera (Diptera, Tephritidae) species. INSECT MOLECULAR BIOLOGY 2007; 16:645-50. [PMID: 17714464 DOI: 10.1111/j.1365-2583.2007.00756.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
The piggyBac transposable element is currently the vector of choice for transgenesis, enhancer trapping, gene discovery and gene function determination in both insects and mammals. However, the recent discovery of sequences with similarity to piggyBac in a wide diversity of organisms suggests that piggyBac may be horizontally transferred to distantly related species. This has raised concern on the wide-range application of piggyBac-based transformation vectors and their stability. In this paper, the presence of sequences homologous to the piggyBac transposase was investigated in 17 species belonging to six genera within the Tephritidae family, including many pest species for which transformation has already been achieved. piggyBac-like sequences, with a high degree of similarity to the original Trichoplusia ni transposase sequence were identified only in six species of the Bactrocera genus.
Collapse
|
40
|
Inferences on the population structure and colonization process of the invasive oriental fruit fly,Bactrocera dorsalis(Hendel). Mol Ecol 2007; 16:3522-32. [PMID: 17845427 DOI: 10.1111/j.1365-294x.2007.03409.x] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The phytophagous insects of the Tephritidae family offer different case histories of successful invasions. An example is Bactrocera dorsalis sensu stricto, the oriental fruit fly which has been recognized as a key pest of Asia and the Pacific. It is known to have the potential to establish adventive populations in various tropical and subtropical areas. Despite the economic risk associated with a putative stable presence of this fly, the genetic aspects of its invasion process have remained relatively unexplored. Using microsatellite markers we have investigated the population structure and genetic variability in 14 geographical populations across the four areas of the actual species range: Far East Asia, South Asia, Southeast Asia and the Pacific Area. Results of clustering and admixture, associated with phylogenetic and migration analyses, were used to evaluate the changes in population genetic structure that this species underwent during its invasion process and establishment in the different areas. The colonization process of this fly is associated with a relatively stable population demographic structure, especially in an unfragmented habitat, rich in intensive cultivation such as in Southeast Asia. In this area, the results suggest a lively demographic history, characterized by evolutionary recent demographic expansions and no recent bottlenecks. Cases of genetic isolation attributable to geographical factors, fragmented habitats and/or fruit trade restrictions were observed in Bangladesh, Myanmar and Hawaii. Regarding the pattern of invasion, the overall genetic profile of the considered populations suggests a western orientated migration route from China to the West.
Collapse
|
41
|
Diffusion of the Nearctic leafhopper Scaphoideus titanus Ball in Europe: a consequence of human trading activity. Genetica 2007; 131:275-85. [PMID: 17242963 DOI: 10.1007/s10709-006-9137-y] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2006] [Accepted: 12/22/2006] [Indexed: 10/23/2022]
Abstract
Scaphoideus titanus Ball is a Nearctic leafhopper that was introduced for the first time in Europe probably at the beginning of the 20th century. In Europe, this species is a specialist on cultivated grapevines and is of great economic importance as the vector of Flavescence dorée (FD), a Grapevine Yellows disease caused by Candidatus Phytoplasma vitis. The Random Amplified Polymorphic DNA (RAPD) technique was employed to obtain genetic information about the diffusion and the structure of S. titanus populations. Two American and 14 European populations were analysed. A total of 188 reproducible bands, obtained from three arbitrary primers, were considered to assess the amount and the pattern of genetic variation within and among leafhopper populations. American populations showed high levels of intra-population polymorphism and dissimilarity and appeared to be the most isolated of all the tested samples. The results confirm the historical role of American samples as the sources for the more recently founded European populations. RAPD analyses revealed a weak genetic structure of European samples that could probably be explained invoking the human role in their diffusion. The non-natural spreading of S. titanus across Europe is in fact attributable to the exchange of grapevine canes and grafts carrying eggs that the insect laid under the bark to overwinter.
Collapse
|
42
|
Globalization and fruitfly invasion and expansion: the medfly paradigm. Genetica 2006; 131:1-9. [PMID: 17111234 DOI: 10.1007/s10709-006-9117-2] [Citation(s) in RCA: 145] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2006] [Accepted: 10/12/2006] [Indexed: 11/29/2022]
Abstract
The phytophagous insects of the Tephritidae family commonly referred to as "true fruit flies" offer different case histories of successful invasions. Mankind has played an important role in altering the distributions of some of the more polyphagous and oligophagous species. However, the question arises why only a few species have become major invaders. The understanding of traits underlying adaptation in different environments is a major topic in invasion biology. Being generalists or specialists, along the K-r gradient of the growth curve, make a difference in term of food resources exploitation and interspecies competition and displacement. The species of the genus Ceratitis are good examples of r-strategists. The genetic and biological data of the most notorious Ceratitis species, the Mediterranean fruit fly Ceratitis capitata (medfly), are reviewed to investigate the traits and behaviours that make the medfly an important invader. It can be learnt from medfly, that invasions in a modern global trade network tend to be due to multiple introductions. This fact allows a maintenance or enhancement of genetic variability in the adventive populations, which in turn increases their potential invasiveness. Our current knowledge of the medfly genome opens the way for future studies on functional genomics.
Collapse
|
43
|
Is polyandry a common event among wild populations of the pest Ceratitis capitata? JOURNAL OF ECONOMIC ENTOMOLOGY 2006; 99:1420-9. [PMID: 16937701 DOI: 10.1603/0022-0493-99.4.1420] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
In many insect species, females can mate more than once and store sperm from more than one male. An assessment and understanding of polyandry in the field can be important for pest species with a high colonization potential, such as the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), which is also highly polyphagous and among the most destructive agricultural insects. The use of polymorphic microsatellite markers, combined with different statistical approaches, provides evidence that polyandry occurs in two C. capitata natural populations, one population from the Greek island of Chios and one population from Rehovot, in Israel. The observed different level of polyandry is discussed in relation to the genetic diversity, seasonality, and demography of the two populations. When polyandry is present, paternity analysis also indicates that one male, presumably the last, tends to sire most of the progeny. Polyandry and paternity skew may have important implications for the evolution of the species, in terms of maintenance of the genetic variability. Moreover, these aspects of the mating behavior, i.e., remating frequency and paternity skew, may locally affect the sterile insect technique, the most commonly applied control strategy against C. capitata.
Collapse
|
44
|
Genomic organization and functional characterization of the alcohol dehydrogenase locus of Ceratitis capitata (Medfly). INSECT MOLECULAR BIOLOGY 2006; 15:259-68. [PMID: 16756545 DOI: 10.1111/j.1365-2583.2006.00642.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Approximately 30 kb of genomic DNA enclosing the Adh locus from the medfly, Ceratitis capitata have been cloned and about 15 kb has been structurally and functionally characterized. The locus consists of two genes, Adh-1 and Adh-2, separated by an intergenic region, which is polymorphic in size ranging from approximately 6.4 kb to 8.1 kb. Both genes consist of three exons and two introns. The introns are below 200 bp in size, except the 1st intron of Adh-1, which is unexpectedly long, variable in size and contains a deleted mariner-like element (postdoc). The two genes are transcribed in different orientations. The Adh-2 gene shows the typical pattern of transcription seen in the homologous genes of Drosophilidae presenting high levels of expression in the fat body, gut and ovaries. The Adh-1 gene is only expressed in the body muscle tissues of embryos, larvae and adult flies, raising the question of what its biological function may be. A DNA fragment containing bases -102 to -1666 relative to the first base of the initiating ATG of Adh-1 is sufficient to drive the expression of a reporter gene in body muscles of Drosophila melanogaster embryos, larvae and adult flies. The study provides further insights into the evolution of the Adh genes of higher diptera.
Collapse
|
45
|
Phylogeny of the subgenus Culicoides and related species in Italy, inferred from internal transcribed spacer 2 ribosomal DNA sequences. MEDICAL AND VETERINARY ENTOMOLOGY 2006; 20:229-38. [PMID: 16796616 DOI: 10.1111/j.1365-2915.2006.00620.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Biting midges of the genus Culicoides (Diptera: Ceratopogonidae) include vectors for the economically important animal diseases, bluetongue (BT) and African horse sickness (AHS). In the Mediterranean Basin, these diseases are transmitted by four species of Culicoides: the first three belong in the subgenus Avaritia Fox and are Culicoides imicola Kieffer, Culicoides obsoletus (Meigen) and Culicoides scoticus Downes and Kettle; the fourth is Culicoides pulicaris (Linnaeus) in the subgenus Culicoides Latreille. In the Palaearctic Region, this subgenus (usually referred to as the C. pulicaris group) now includes a loose miscellany of some 50 taxa. The lack of clarity surrounding its taxonomy stimulated the present morphological and molecular study of 11 species collected in Italy. Phylogenetic analysis of nuclear ribosomal DNA internal transcribed spacer 2 (ITS2) sequence variation demonstrated a high degree of divergence. These results, combined with those from a parallel morphological study, disclosed: (1) that some previously described taxa should be resurrected from synonymy; (2) that there are new species to be described; (3) that the subgenus Culicoides (as currently employed) is a polyphyletic assemblage of four lineages - the subgenus Culicoides sensu stricto, the subgenus Silvicola Mirzaeva and Isaev, the subgenus Hoffmania Fox and the hitherto unrecognized Fagineus species complex. Each is discussed briefly (but not defined) and its constituent Palaearctic taxa listed. Strong congruence between morphological and molecular data holds promise for resolving many of the difficult taxonomic issues plaguing the accurate identification of vector Culicoides around the world.
Collapse
|
46
|
Abstract
A hobo-related sequence, Cchobo, with high similarity to the Drosophila melanogaster HFL1 and hobo108 elements was isolated from the medfly. Thirteen PCR-derived clones, which share 97.9-100% DNA identity, were sequenced, seven of which do not show frame-shift or stop codon mutations in their conceptual translations. The consensus sequence has 99.7% DNA identity with the D. melanogaster hobo element HFLI. In a phylogenetic analysis with other hobo-related elements, Cchobo clusters with the HFL1 and hobo108 elements from D. melanogaster and hobo-related elements from D. simulans, D. mauritiana and Mamestra brassicae. These elements may have undergone horizontal transfer in the recent past. The genomic distribution of Cchobo was studied by FISH to mitotic and polytene chromosomes, which revealed that Cchobo is distributed within both the heterochromatin and euchromatin. Intra- and interstrain polymorphisms were detected both at euchromatic and heterochromatic sites. These findings suggest that active copies of the element may be present in the medfly genome.
Collapse
|
47
|
Abstract
As a result of their rapid expansion and large larval host range, true fruit flies are among the world's most important agricultural pest species. Among them, Ceratitis capitata has become a model organism for studies on colonization and invasion processes. The genetic aspects of the medfly invasion process have already been analysed throughout its range, with the exception of Australia. Bioinvasion into Australia is an old event: medfly were first captured in Australia in 1895, near Perth. After briefly appearing in Tasmania and the eastern states of mainland Australia, medfly had disappeared from these areas by the 1940s. Currently, they are confined to the western coastal region. South Australia seems to be protected from medfly infestations both by the presence of an inhospitable barrier separating it from the west and by the limited number of transport routes. However, numerous medfly outbreaks have occurred since 1946, mainly near Adelaide. Allele frequency data at 10 simple sequence repeat loci were used to study the genetic structure of Australian medflies, to infer the historical pattern of invasion and the origin of the recent outbreaks. The combination of phylogeographical analysis and Bayesian tests showed that colonization of Australia was a secondary colonization event from the Mediterranean basin and that Australian medflies were unlikely to be the source for the initial Hawaiian invasion. Within Australia, the Perth area acted as the core range and was the source for medfly bioinvasion in both Western and South Australia. Incipient differentiation, as a result of habitat fragmentation, was detected in some localized areas at the periphery of the core range.
Collapse
|
48
|
The taxonomy of Culicoides vector complexes - unfinished business. VETERINARIA ITALIANA 2004; 40:151-159. [PMID: 20419654] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
The thirty species of Culicoides biting midges that play a greater or lesser role in the transmission of bluetongue (BT) disease in the pantropical regions of the world are listed. Where known, each species is assigned to its correct subgenus and species complex. In the Mediterranean region there are four species of Culicoides involved in the transmission of BT and belong in the subgenera Avaritia Fox, 1955 (three species) and Culicoides Latreille, 1809 (one species). Using both morphological and molecular second internal transcribed spacer (ITS2) sequence data, the authors reappraise the taxonomy of these four species and their congeners. A total of 56 populations of Culicoides collected from across Italy and representing 17 species (18 including the outgroup taxon C. imicola Kieffer, 1913) were analysed. The findings revealed the following: C. imicola is the only species of the Imicola Complex (subgenus Avaritia) to occur in the Mediterranean region. In Europe the subgenera Avaritia and Culicoides (usually, but not quite correctly, equated with the C. obsoletus and C. pulicaris groups, respectively) are both polyphyletic, each comprising three or more species complexes (including a hitherto unknown complex). About half the species studied could not be identified with certainty; furthermore, the results indicate that at least three previously described species of Palaearctic Culicoides should be resurrected from synonymy. Finally, a high level of taxonomic congruence occurred between the morphological and the molecular data. One of the 'new' vector species, C. pulicaris, was described by the father of taxonomy, Carl Linnaeus, in 1758, but today, almost 250 years later, no monograph has appeared that treats the Culicoides fauna of the northern hemisphere as a whole. At a time when such economically important livestock diseases as BT are affecting ever larger areas of Europe, it would seem appropriate to commence the production of such a monograph to aid in the field identification of vector Culicoides. This 'unfinished business' might best be achieved through a collaborative network embracing all ceratopogonid specialists currently active in both the Palaearctic and Nearctic faunal realms.
Collapse
|
49
|
Molecular Basis of the Size Polymorphism of the First Intron of theAdh-1 Gene of the Mediterranean Fruit Fly, Ceratitis capitata. J Mol Evol 2004; 58:732-42. [PMID: 15461430 DOI: 10.1007/s00239-004-2596-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The first intron of the gene encoding one of the alcohol dehydrogenase isoenzymes (ADH-1) in Ceratitis capitata is highly polymorphic in size. Five size variants of this intron were isolated from different strains and populations and characterized. Restriction map and sequence analysis showed that the intron size polymorphism is due to the presence or absence of (a) a copy of a defective mariner-like element, postdoc; (b) an approximately 550-bp 3' indel which exhibits no similarity to any known sequence; and (c) a central duplication of 704 bp consisting of part of the 3' end of the postdoc element, the region between postdoc and the 3' indel, and the first 20 bp of the 3' indel. The homologous Adh-1 intron was amplified from the congeneric species, Ceratitis rosa, in order to obtain an outgroup for comparative and phylogenetic analyses. The C. rosa introns were polymorphic in size, ranging from about 1100 to 2000 bp, the major difference between them being the presence or absence of a mariner-like element Crmar2, unrelated to the postdoc element. Phylogenetic analysis suggests that the shorter intron variants in C. capitata may represent the ancestral form of the intron, the longest variants apparently being the most recent.
Collapse
|
50
|
Population genetics of the potentially invasive African fruit fly species, Ceratitis rosa and Ceratitis fasciventris (Diptera: Tephritidae). Mol Ecol 2004; 13:683-95. [PMID: 14871371 DOI: 10.1046/j.1365-294x.2004.02105.x] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
A set of 10 microsatellite markers was used to survey the levels of genetic variability and to analyse the genetic aspects of the population dynamics of two potentially invasive pest fruit fly species, Ceratitis rosa and C. fasciventris, in Africa. The loci were derived from the closely related species, C. capitata. The degree of microsatellite polymorphism in C. rosa and C. fasciventris was extensive and comparable to that of C. capitata. In C. rosa, the evolution of microsatellite polymorphism in its distribution area reflects the colonization history of this species. The mainland populations are more polymorphic than the island populations. Low levels of differentiation were found within the Africa mainland area, while greater levels of differentiation affect the islands. Ceratitis fasciventris is a central-east African species. The microsatellite data over the Uganda/Kenya spatial scale suggest a recent expansion and possibly continuing gene flow within this area. The microsatellite variability data from C. rosa and C. fasciventris, together with those of C. capitata, support the hypothesis of an east African origin of the Ceratitis spp.
Collapse
|