Molecular and morphological characterization of the predatory mite Amblyseius largoensis (Acari: Phytoseiidae): surprising similarity between an Asian and American populations

The accurate characterization of biological control agents is a key step in control programs. Recently, Amblyseius largoensis from Thailand were introduced in Brazil to evaluate their efficiency for the control of the red palm mite, Raoiella indica. The aim of this study was to confirm their identification and to characterize the population from Thailand, comparing it to populations of the Americas and Indian Ocean islands. In addition, a population of A. largoensis from New Caledonia, Oceania, of which DNA sequences were available, was included in phylogenetic analyses. Morphometric data obtained for the population of A. largoensis from Thailand were compared to those of populations from Reunion Island and the Americas through univariate and multivariate analyses. Two DNA fragments were amplified and sequenced: the nuclear ribosomal region ITSS and the mitochondrial 12S rRNA. Haplotypes (12S rRNA) and genotypes (ITSS) were identified and phylogenetic analyses using both fragments were conducted separately and combined using maximum likelihood and the Bayesian information criterion. The integrative approach reveals morphometric and molecular variabilities among populations of A. largoensis and shows that the population identified as A. largoensis collected in Thailand, as well as that from New Caledonia, are conspecific to the populations of the Americas and Indian Ocean islands. Populations from the Americas and Asia are more related to each other than with that from the Indian Ocean islands. Hypotheses to explain this clustering are proposed. Data on the molecular intraspecific variability of this predatory mite from remote areas will be helpful for the development of molecular diagnosis.

Which molecular markers for assessing which taxonomic level? The case study of the mite family Phytoseiidae (Acari: Mesostigmata)

The use of molecular markers for resolving systematics issues has improved our knowledge of life history. However, for the taxa studied herein-the predatory mite family Phytoseiidae-molecular phylogeny is impeded by a lack of suitable markers for deeper taxonomic levels. This study aims (i) to establish DNA amplification protocols for molecular markers known to resolve supraspecific nodes in other taxa, (ii) to determine their individual performance in assessing the clustering of species, genera, tribes and subfamilies, and (iii) to characterize the additional information provided when markers are concatenated. A new phylogenetic index is proposed based on ecological concepts, considering trees as a community of nodes. New and efficient protocols for DNA amplification of six molecular markers are provided. The concatenated tree globally provides more robust and reliable information, especially for deeper nodes. However, for assessing species identification and within-genera phylogenies, the combined use of six markers does not seem necessary, underlining the need to resize experiments depending on their taxonomic objectives. Finally, this study lays the methodological foundations with which to test the present Phytoseiidae classification as the first phylogeny obtained shows incongruence with the present morphological classification.

The predatory mite Neoseiulus paspalivorus (Phytoseiidae) in Brazil: taxonomic status, reproductive compatibility and morphological and molecular variability

The predatory mite Neoseiulus paspalivorus (De Leon) is often found in association with the coconut mite, Aceria guerreronis Keifer. The identification of natural enemies is essential for the definition of biological control strategies. Therefore, the present study aimed to confirm whether the mite populations from different Northeastern Brazilian states identified as N. paspalivorus belong to the same species. This determination was accomplished through the study of morphometric variability in 33 anatomical characters and of molecular variability in two DNA fragments: Internal Transcribed Spacer (ITS) rDNA and cytochrome c oxidase subunit I (COI) mtDNA. This study also determined whether there is reproductive isolation between the two most morphologically distinct populations (Rio Grande do Norte and Paraíba). Intraspecific morphometric variability was observed among the five populations of N. paspalivorus. Despite this variability, the crosses and backcrosses of the most morphologically distinct populations did not show reproductive incompatibility. The molecular analysis indicated the absence of genetic differences among the N. paspalivorus populations for the ITS fragment. Three haplotypes were identified for the COI fragment, and the genetic distance ranged from 0 to 0.2 %. Despite the morphometric differences, the results of the molecular and biological analysis corroborate the previous identification of N. paspalivorus for all of the studied populations. The present study contributes to the systematics of Phytoseiidae predatory mites and to the biological control of A. guerreronis by the accurate identification and characterization of one of its main natural enemies along extensive areas in Brazil.

The endosymbionts Wolbachia and Cardinium and their effects in three populations of the predatory mite Neoseiulus paspalivorus

Whereas endosymbiont-induced incompatibility is known to occur in various arthropod taxa, such as spider mites, insects and isopods, it has been rarely reported in plant-inhabiting predatory mites (Acari: Phytoseiidae). Recent cross-breeding studies with the phytoseiid mite Neoseiulus paspalivorus De Leon revealed a complete post-mating reproductive isolation between specimens collected from three geographic origins-Northeast Brazil (South America), Benin and Ghana (West Africa)-even though they are morphologically similar. We carried out a study to assess to what extent these populations exhibit genetic differences and whether endosymbionts are involved in the incompatibility. First, we used the mitochondrial cytochrome oxidase I (COI) gene to assess genetic diversity among the three populations. Second, we used a PCR-based method to check for the presence of Wolbachia and/or Cardinium in these populations, and we determined their phylogenetic relationships using specific primers for Wolbachia and Cardinium 16S rDNA genes. Third, we also conducted a test using an antibiotic (tetracycline) in an attempt to eliminate the symbionts and evaluate their effects on the reproductive compatibility of their host. Based on the DNA sequences of their COI genes, specimens of the three populations appear to be genetically similar. However, the 16S rDNA gene sequences of their associated endosymbionts differed among the three populations: the Benin and Brazil populations harbour different strains of Wolbachia symbionts, whereas the Ghana population harbours Cardinium symbionts. In response to antibiotic treatment females of each of the three populations became incompatible with untreated males of their own population, similar to that observed in crossings between females from one geographic population and males from another. Compatibility was restored in crosses involving uninfected Brazil females and uninfected Benin males, whereas the reciprocal crosses remained incompatible. Cardinium symbionts seem to be essential for oviposition in the Ghana population. It is concluded that their associated bacterial symbionts are the cause of the post-mating reproductive isolation previously observed among the three geographic populations. This insight is relevant to biological control of coconut mites for which N. paspalivorus is an effective predator, because introducing one geographic strain into the population of another (e.g. in field releases or mass cultures) may cause population growth depression.

Overview of a classical biological control project directed against the red palm mite in Florida

Information is provided on the steps involved in classical biological control programs, with an outline of the steps achieved in the classical biological control of the red palm mite, Raoiella indica (Acari: Tenuipalpidae), in Florida. An overview is provided of the results and an accompanying paper by Bowman and Hoy (2012) describes the molecular analyses conducted to characterize phytoseiid predators of the red palm mite collected from Mauritius. The Mauritius phytoseiids were identified as Amblyseius largoensis, using morphological criteria, and compared to four populations of A. largoensis from Florida. The difficulties encountered in the systematics, rearing, and evaluation of the Mauritius phytoseiids are described. A method was tested for obtaining DNA from single mites without destroying the body so that voucher specimens can be maintained. Ultimately, the project was terminated due to constraints expected in obtaining permission to make releases.

Molecular discrimination of phytoseiids associated with the red palm mite Raoiella indica (Acari: Tenuipalpidae) from Mauritius and South Florida

Phytoseiid populations imported from Mauritius for evaluation for a classical biological control program in Florida, USA, were morphologically identified as Amblyseius largoensis Muma, a species associated with the red palm mite in south Florida and the Caribbean. Bayesian analysis and sequence divergences of the mitochondrial 12S rRNA and nuclear Elongation factor--I alpha (EF-Iα) genes and Neighbor-Joining analysis of High-fidelity-RAPD-PCR markers were used to discriminate between the south Florida and Mauritius populations. High-fidelity-RAPD-PCR markers in addition to Bayesian and sequence divergence analyses of the 12S rRNA sequences suggest that the Mauritius and south Florida populations are genetically different but whether these are species or population differences is unknown. The degenerate EF-Iα primers used to survey the phytoseiids amplified two different elongation factor sequences with distinct amino acid translations, the putative EF-Iα and an unknown elongation factor. Variability within the 12S gene was used to develop population-specific primers for identifying the Mauritius phytoseiids in the event they are released in south Florida.

Obtaining molecular data for all life stages of Typhlodromus (Typhlodromus) exhilaratus (Mesostigmata: Phytoseiidae): consequences for species identification

Several species of the family Phytoseiidae are known to control mite pests in many crops worldwide. However, biological control success greatly depends on the accurate identification of these predatory mites. Species diagnostics is essentially based on the morphological characters of females. Thus, when only immature stages and/or males are collected, their identification is poorly supported. Molecular tools could be of great help to overcome these difficulties, as molecular sequences are assumed to be identical for the life stage considered. However, one of the essential points is to extract a sufficient DNA amount from a single specimen of immature stages (eggs, protonymphs, deutonymphs) and males (less than 300 μm in length) to amplify and sequence DNA. The markers used were two mitochondrial DNA fragments (12S rRNA and Cytb mtDNA) and the species studied were Typhlodromus (Typhlodromus) exhilaratus and T. (T.) phialatus, two cryptic species, reported to control mite pests in crops of southern Europe and commonly found on the same plants. Despite a low quantity of DNA extracted, particularly for the egg, larva and protonymph stages, DNA was amplified and sequences were obtained from all the life stages considered with the two mtDNA fragments. Sequences from all the developmental stages of T. (T.) exhilaratus were identical and well differentiated from those of its sister-species. However, contaminations were observed especially for eggs and DNA amplified with the Cytb mt marker. Utility of the present results are discussed and protocol improvements are proposed.

Morphological, molecular and cross-breeding analysis of geographic populations of coconut-mite associated predatory mites identified as Neoseiulus baraki: evidence for cryptic species?

Surveys were conducted in Brazil, Benin and Tanzania to collect predatory mites as candidates for control of the coconut mite Aceria guerreronis Keifer, a serious pest of coconut fruits. At all locations surveyed, one of the most dominant predators on infested coconut fruits was identified as Neoseiulus baraki Athias-Henriot, based on morphological similarity with regard to taxonomically relevant characters. However, scrutiny of our own and published descriptions suggests that consistent morphological differences may exist between the Benin population and those from the other geographic origins. In this study, we combined three methods to assess whether these populations belong to one species or a few distinct, yet closely related species. First, multivariate analysis of 32 morphological characters showed that the Benin population differed from the other three populations. Second, DNA sequence analysis based on the mitochondrial cytochrome oxidase subunit I (COI) showed the same difference between these populations. Third, cross-breeding between populations was unsuccessful in all combinations. These data provide evidence for the existence of cryptic species. Subsequent morphological research showed that the Benin population can be distinguished from the others by a new character (not included in the multivariate analysis), viz. the number of teeth on the fixed digit of the female chelicera.

Isolation and characterization of polymorphic microsatellite markers in Tetranychus urticae and cross amplification in other Tetranychidae and Phytoseiidae species of economic importance

Tetranychus urticae Koch is a cosmopolitan phytophagous mite considered as the most polyphagous species among spider mites. Population genetic studies using molecular markers such as microsatellites have proven to be extremely informative to address questions about population structure, phylogeography and host preferences. The aim of this study was to increase the available molecular tools to gain insight into the genetic structure of T. urticae populations of citrus orchards, which might help in their management. Five microsatellite DNA libraries were developed using probes with the motifs CT, CTT, GT and CAC following the FIASCO protocol. Positive clones, those that included the insert with the microsatellite, were detected using the PIMA-PCR technique. Combinations of primers were designed on 22 out of 32 new microsatellites loci and their polymorphism was tested in four populations sampled along the eastern coast of Spain. Eleven successful amplifications were obtained. Cross amplification was tested in the tetranychids Aphlonobia histricina, Eutetranychus banksi, E. orientalis, Oligonychus perseae, Panonychus citri, Tetranychus evansi, T. okinawanus and T. turkestani, and the phytoseiids Amblyseius swirskii, A. cucumeris, A. andersoni, Euseius stipulatus, Neoseiulus barkeri, N. californicus, Phytoseiulus persimilis and Typhlodromus phialatus. Eight successful cross amplifications were obtained.

Morphological variation and reproductive incompatibility of three coconut-mite-associated populations of predatory mites identified as Neoseiulus paspalivorus (Acari: Phytoseiidae)

Predatory mites identified as Neoseiulus paspalivorus DeLeon (Phytoseiidae) have been considered as agents for classical biological control of the coconut mite, Aceria guerreronis Keifer (Eriophyidae), in Africa and elsewhere. Preliminary identification of geographically distinct populations as belonging to the same species (N. paspalivorus) was based on their morphological similarity. However, laboratory studies recently conducted have shown large differences in feeding behaviors and biological characteristics among individuals collected from three geographic origins: Brazil (South America), Benin and Ghana (West Africa). As morphologically similar specimens do not necessarily belong to the same species, we evaluated under laboratory conditions, reproductive compatibility between the specimens from three geographic locations to ascertain their conspecificity. Morphological measurements were also made to determine whether there is a means of discriminating between them. Inter-population crosses showed complete reproductive isolation between the three geographic populations, but interpopulation discontinuities in morphometric characters were absent. These results indicate that the tested specimens are distinct biological entities despite morphological similarity. Further molecular genetic studies are therefore proposed, including screening for endosymbionts and assessment of genetic differentiation, to determine the cause of reproductive incompatibility and to clarify the taxonomic relationship between those populations.

Integrative taxonomy demonstrates the unexpected synonymy between two predatory mite species: Cydnodromus idaeus and C. picanus (Acari:Phytoseiidae)

Species of the mite family Phytoseiidae are well known as predators of mite pests all over the world. Their identification is thus of great interest for biological control. The specimens examined in this study belong to the species Cydnodromus idaeus (described from Brazil) and C. picanus (described from Chile). They were collected together on the same plant in Argentina. These species are mainly differentiated by the presence/absence of the dorsal solenostomes (gland openings) gd2. Some morphometric differences were observed between the Argentinian specimens and the type material of C. idaeus and C. picanus; however, they were not sufficient to support a species separation. Morphological and molecular analyses with two mtDNA (12S rRNA, CytB) and a nuclear DNA (ITS) marker showed no difference between Argentinian specimens with and without the solenostome gd2. Also, molecular differentiation between these latter specimens, C. picanus and C. idaeus, was very low, suggesting that all these individuals belong to the same species. Biological experiments confirm these results, as 75% of the progeny resulting from females with gd2 had gd2 present whereas all the descendants resulting from the females without gd2 had gd2 present too. The presence/absence of this solenostome seems thus to be variable within a species and cannot be used diagnostically. We conclude that all specimens from Argentina belong to C. idaeus and that C. picanus is a junior synonym of C. idaeus. The present results were unexpected as the presence/absence of solenostomes is used in Phytoseiidae identification keys and as one of a suite of diagnostic characters for discriminating between species. The consequences of these findings for the taxonomy of Phytoseiidae are discussed.

The puzzle of DNA sequences of Phytoseiidae (Acari:Mesostigmata) in the public GenBank database

The public database GenBank is an increasingly important source of sequence data for diagnostic and phylogenetic research; however, not all deposited sequences are necessarily correctly ascribed to a source species. We considered the example of the mite family Phytoseiidae to determine how the corresponding sequences could be accurately exploited. Phytoseiidae mites are well known worldwide for their ability to control certain mite and insect pests. The number of molecular approaches, especially for diagnostic purposes, has increased over the past decade, leading to an increase in the number of sequences registered in the GenBank database. The aim of the present paper was to evaluate the validity of the DNA sequences presently assigned to Phytoseiidae species in this database. Three hundred and fifty-one sequences, corresponding to the four most frequently registered DNA fragments (ITS, COI, Cytb and 12S rRNA), were considered. DNA extraction, amplification and sequencing were performed for the fragments 12S rRNA and ITS for Amblyseius andersoni, A. swirskii, Iphiseius degenerans, Euseius ovalis, E. stipulatus, Neoseiulus cucumeris and Typhlodromus pyri, as some identifications were questionable. Numerous problems were evident based on genetic distance analyses of these sequences. First, nomenclatural problems were encountered, preventing the correct identification of the taxa sequenced in one case. Suspected misidentifications were frequent, stressing the importance of voucher specimen availability. For the 12S rRNA fragment, sequences assigned to three Phytoseiidae species were those of their prey (Astigmata), underlining the care that must be taken when manipulating the DNA of such predators (sterile conditions and specific PCR primers). Finally, sequences of two regions of the COI mtDNA were encountered, leading to alignment problems between sequences of a same gene and same species. These results are discussed in relation to responsibilities of authors in terms of taxon identification and the great utility of open access DNA sequence databases, such as GenBank, for improving taxonomic identifications and advancing scientific research.

Morphological and molecular diagnostics of Phytoseiulus persimilis and Phytoseiulus macropilis (Acari: Phytoseiidae)

This study focuses on the diagnostics of two natural enemy species, belonging to the genus Phytoseiulus in the family Phytoseiidae (sub-family Amblyseiinae): P. macropilis and P. persimilis. These two species are of primary importance in biological control all over the world. However, they are morphologically very similar and specific diagnostics is difficult. This study utilizes mitochondrial molecular markers (12S rRNA and Cytb mtDNA) to differentiate these two species. Morphological analyses showed significant differences between P. persimilis and P. macropilis for 17 morphological characters of the 32 considered. However, despite these significant differences, the ranges of all characters overlap. Only the serration of the macroseta on the basitarsus (StIV) allows the differentiation between P. persimilis and P. macropilis. Despite these small morphological differences, molecular results, for both mitochondrial DNA fragments considered (rRNA and Cytb mtDNA), showed a clear delineation between the specimens of P. macropilis and P. persimilis. This study emphasizes (i) that only one morphological character (serration of the seta StIV) clearly separates these two species, and (ii) the usefulness of an automatical molecular and simple diagnostic tool for accurate differentiation of the two species and ensure the morphological diagnostics. Further studies are proposed, including more DNA sequences especially for P. macropilis.

A DNA extraction procedure that allows mite specimens to be slide mounted: phytoseiid species evaluated as a model

Four protocols for extracting DNA from mites, using phytoseiid species as exemplars, were evaluated to determine whether the DNA obtained could be used to amplify nuclear, mitochondrial or Random Amplified Polymorphic DNA (RAPD) markers from males, females and eggs. Protocol 3 was identified as the best and this allowed High-fidelity PCR (Hf-PCR) and Hf-RAPD PCR to be used successfully; it left behind the intact body of adult mites so they could be slide mounted for morphological analyses, although the eggs had to be pricked in order to yield sufficient DNA for amplifications. Protocol 3 involved soaking intact specimens in a GuSCN buffer and using a silica matrix, which binds nucleic acids, to yield DNA for amplification. The DNA isolated could be stored up to a month, indicating that the quality was good. This DNA extraction protocol will allow researchers to collect mites, store them in 95% ethanol, and subsequently extract sufficient DNA from single adults or eggs to provide diagnostic PCR products from both nuclear and mitochondrial DNA, yet leave the bodies intact for morphological analyses.

Molecular and morphological evidence for a new species status within the genus Euseius (Acari: Phytoseiidae)

The identity of specimens belonging to the genus Euseius Wainstein, 1962 found on several trees in France is investigated. These specimens are morphologically close to Euseius stipulatus (Athias-Henriot, 1960) except for the shape of the spermatheca and the dorsal shield reticulation. The aim of the present study was to determine if these specimens belong to this latter species and if the shape of the spermatheca could be considered a reliable diagnostic character. Thirty-four characters, including idiosomal seta lengths, were measured and molecular tests (12S rDNA, COI mtDNA) were carried out. Although small, significant differences between populations of Euseius sp. were observed. The morphometric differences between E. stipulatus and Euseius sp. were very small except for the seta z2 and for the length of the ventrianal shield, as well as the length and form of the spermatheca. Molecular analyses support that Euseius sp. and E. stipulatus are two different species. Euseius sp. has been described as a new species to science in another publication under the name Euseius gallicus . Reliability of some morphological characters for species diagnosis is discussed.

Kampimodromus aberrans (Acari: Phytoseiidae) from the USA: morphological and molecular assessment of its density

Morphological measurements and a mitochondrial molecular marker (COI) were used to identity specimens reported as Kampimodromus aberrans on hazelnut in the USA. Several species and populations of this genus were studied to assist with identification. Both data types showed that specimens from the USA differed from K. aberrans from other regions. USA specimens seem to belong to the same species as Kampimodromus specimens from France on hazelnut. These mites were morphologically similar to Kampimodromus coryli and K. corylosus, which according to the original descriptions, are distinguished by the presence or absence of a tooth on the movable digit of the chelicera, with K. coryli having one tooth and K. corylosus none. As chelicerae of Kampimodromus from hazelnut in the USA and France are toothless, they are assigned to the species K. corylosus. Studies showed that morphological characters traditionally used to identify Kampimodromus species, such as setal length, are of less value than other characters that are difficult to observe, such as the numbers of solenostomes and the presence of teeth on the movable digit of the chelicerae. Some synonyms are discussed.