DNA sequence and RFLP data reflect geographical spread and relationships of Amylostereum areolatum and its insect vectors

Multilocus Genotyping and Intergenic Spacer Single Nucleotide Polymorphisms of Amylostereum areolatum (Russulales: Amylostereacea) Symbionts of Native and Non-Native Sirex Species

Sirex noctilio along with its mutualistic fungal symbiont, Amylostereum areolatum (a white rot fungus), is an invasive pest that causes excessive damage to Pinus plantations in Northeast China. In 2015, S. noctilio were found to attack Pinus sylvestris var. mongolica, and often share larval habitat with the native woodwasp, S. nitobei. The objective of this study was to determine the possible origin(s) of the introduced pest complex in China and analyse the genetic diversity between A. areolatum isolated from invasive S. noctilio, native S. nitobei and other woodwasps collected from Europe (native range) and other countries. Phylogenetic analyses were performed using the intergenic spacer (IGS) dataset and the combined 4-locus dataset (the internal transcribed spacer region (ITS), translation elongation factor alpha 1 (tef1), DNA-directed ribosomal polymerase II (RPB2), and mitochondrial small subunit (mtSSU)) of three Amylostereum taxa. The multilocus genotyping of nuclear ribosomal regions and protein coding genes revealed at least three distinct multilocus genotypes (MLGs) of the fungus associated with invasive S. noctilio populations in Northeast China, which may have come from North America or Europe. The IGS region of A. areolatum carried by S. noctilio from China was designated type B1D2. Our results showed a lack of fidelity (the paradigm of obligate fidelity to a single fungus per wasp species) between woodwasp hosts and A. areolatum. We found that the native S. nitobei predominantly carried A. areolatum IGS-D2, but a low percentage of females instead carried A. areolatum IGS-B1D2 (MLG A13), which was presumably due to horizontal transmission from S. noctilio, during the sequential use of the same wood for larval development. The precise identification of the A. areolatum genotypes provides valuable insight into co-evolution between Siricidae and their symbionts, as well as understanding of the geographical origin and history of both Sirex species and their associated fungi.

The balance of trade in alien species between South Africa and the rest of Africa

Background: Alien organisms are not only introduced from one biogeographical region to another but also spread within regions. As South Africa shares land borders with six countries, multiple opportunities exist for the transfer of alien species between South Africa and other African countries; however, the direction and importance of intra-regional spread is unclear. Objectives: The aim of this study was to gain a greater understanding of the introduction of alien species into Africa and the spread of species between South Africa and other African countries. Method: We developed scenarios that describe the routes by which alien species are introduced to and spread within Africa and present case studies for each. Using data from literature sources and databases, the relative importance of each scenario for alien birds and insect pests of eucalypts was determined, and the direction and importance of intra-regional spread was assessed. Results: Alien species from many taxonomic groups have, through various routes, been introduced to and spread within Africa. For birds and eucalypt insect pests, the number of species spreading in the region has recently increased, with South Africa being a major recipient of birds (14 species received and 5 donated) and a major donor of eucalypt insect pests (1 species received and 10 donated). For both groups, many introduced species have not yet spread in the region. Conclusion: The intra-regional spread of alien species in Africa represents an important and possibly increasing threat to biosecurity. To address this threat, we propose a framework that details how African countries could cooperate and develop a coordinated response to alien species introductions.

Proteomic analysis of the venom and venom sac of the woodwasp, Sirex noctilio - Towards understanding its biological impact

The European horntail woodwasp, Sirex noctilio, is an invasive insect that attacks conifer hosts, particularly Pinus species. Venom injected by female S. noctilio, together with its symbiotic fungus, damages the normal physiology of Pinus, leading to death of the tree. To identify the proteinaceous components in the venom and uncover the interplay between venom proteins and tree proteins, clarification of the overall profile of proteins produced in the venom gland apparatus was carried out in this work. The venom sac proteome utilised in-solution digested in either a natural or deglycosylated state, prior to nanoHPLC LTQ-Orbitrap under CID/ETD mode. Here, we report the identification of 1454 and 1225 proteins in venom and sac, respectively, with 410 mutual proteins. Approximately 90 proteins were predicted to be secretory, of which 8 have features characteristic of toxins. Chemosensory binding proteins were also identified. Gene ontology and KEGG pathway analysis were employed to predict the protein functions and biological pathways in venom and sac. Protein-protein interaction (PPI) analysis suggested that one-step responses represent the majority of the Sirex-Pinus PPIs, and the proteins representing network hub nodes could be of importance for the development of pest management strategies.

SIGNIFICANCE

The woodwasp Sirex noctilio is an invasive species in many parts of the world, including Australia and North America, where it is considered within the top 10 most serious forest insects. Where they have been introduced, the female woodwasps attack living pine trees, causing significant economic losses. Central to this destruction is the woodwasp's life cycle requirement to bore a hole to deposit eggs and a toxic mucus that disables the tree's network for transporting water and nutrients, yet aids in larval survival. Here we specifically examine the mucus gland apparatus and its contents, revealing the protein components that together with 'noctilisin' facilitate this complex association. The identification of chemosensory binding proteins further supports a role for the woodwasp ovipositor as an instrument for early stages of host tree selection. These findings could provide important clues towards the development of novel control tools against this pest.

Sirex woodwasp: a model for evolving management paradigms of invasive forest pests

The Sirex woodwasp, Sirex noctilio, and its fungal mutualist, Amylostereum areolatum, together constitute one of the most damaging invasive pests of pine. Despite a century of research and well-established management programs, control remains unpredictable and spread continues to new areas. Variable success in managing this pest has been influenced by complex invasion patterns, the multilayered nature of biological interactions, the varying local ecologies, and microevolutionary population processes in both the biocontrol organisms and in the wasps. Recent research findings are challenging the historical perspectives on methods to manage the Sirex woodwasp, calling for management programs to incorporate the variable local dynamics affecting this pest complex. In this regard, the Sirex woodwasp provides a superb model to illustrate the need for a different approach to develop efficient and sustainable management tools to deal with the growing and global nature of pest invasions in forests and plantations.

Fidelity among Sirex woodwasps and their fungal symbionts

We report that associations between mutualistic fungi and their economically and ecologically important woodwasp hosts are not always specific as was previously assumed. Woodwasps in the genus Sirex engage in obligate nutritional ectosymbioses with two species of Amylostereum, a homobasid\iomycete genus of white rot fungi. In the present study, the Amylostereum species and genotypes associated with three species of Sirex native to eastern North America and one relatively recent invasive Sirex from Europe were investigated by comparing intergenic spacer regions (IGS). Sirex spp. were sampled over 6 years from 23 sites in six US states, ranging from Maine in the northeast to Louisiana in the southeast, to obtain samples of Amylostereum from mycangia of adult females. Two of the native Sirex species (Sirex nigricornis and Sirex nitidus) were associated with either Amylostereum chailletii or Amylostereum areolatum, refuting the hypothesis of strict species-specific relationships. However, the invasive Sirex noctilio and the native Sirex cyaneus were each collected with only A. areolatum or A. chailletii, respectively, although S. noctilio was associated with two different IGS genotypes of A. areolatum and S. cyaneus occurs sympatrically with the other native Sirex. In Pinus, the preferred host tree of S. nigricornis and S. noctilio, these species co-occurred in 25.9 % of trees sampled, and horizontal transmission of fungal strains from S. noctilio to S. nigricornis was documented, although only in one tree. The extent that further spread and establishment of S. noctilio will alter the composition of symbionts carried by native Sirex is unknown but will depend in part on the degree of flexibility in these host-symbiont associations.

Retracing the routes of introduction of invasive species: the case of the Sirex noctilio woodwasp

Understanding the evolutionary histories of invasive species is critical to adopt appropriate management strategies, but this process can be exceedingly complex to unravel. As illustrated in this study of the worldwide invasion of the woodwasp Sirex noctilio, population genetic analyses using coalescent-based scenario testing together with Bayesian clustering and historical records provide opportunities to address this problem. The pest spread from its native Eurasian range to the Southern Hemisphere in the 1900s and recently to Northern America, where it poses economic and potentially ecological threats to planted and native Pinus spp. To investigate the origins and pathways of invasion, samples from five continents were analysed using microsatellite and sequence data. The results of clustering analysis and scenario testing suggest that the invasion history is much more complex than previously believed, with most of the populations being admixtures resulting from independent introductions from Europe and subsequent spread among the invaded areas. Clustering analyses revealed two major source gene pools, one of which the scenario testing suggests is an as yet unsampled source. Results also shed light on the microevolutionary processes occurring during introductions, and showed that only few specimens gave rise to some of the populations. Analyses of microsatellites using clustering and scenario testing considered against historical data drastically altered our understanding of the invasion history of S. noctilio and will have important implications for the strategies employed to fight its spread. This study illustrates the value of combining clustering and ABC methods in a comprehensive framework to dissect the complex patterns of spread of global invaders.

Putative origin of clonal lineages of Amylostereum areolatum, the fungal symbiont associated with Sirex noctilio, retrieved from Pinus sylvestris, in eastern Canada

The Eurasian Sirex noctilio-Amylostereum areolatum complex was discovered and has become established close to the North American Great Lakes in the 2000s. This invasive forest insect pest represents a very high risk to native and exotic pines in North America. We investigated the geographical origin of clonal lineages of the fungal symbiont A. areolatum in the recently pest-colonized eastern Canadian region by analyzing mitochondrial and nuclear sequence variations and comparing the genetic diversity of a worldwide collection of fungal symbionts among six countries where the Sirex complex is native and four countries from which the insect-fungal complex has been introduced. In total, 102 isolates were analyzed. While 12 multilocus genotypes (MLGs) are observed in the areas where S. noctilio is native, only two MLGs are retrieved from areas where S. noctilio is not native, indicating the wide spread of clonal lineages in the introduced fungal symbiont of S. noctilio. MLG2 comprises 26% of the Canadian isolates and is also observed in Chile and South Africa, where the insect-fungal complex has also been introduced. MLG3 comprises 74% of the Canadian isolates and is also observed in the USA, but nowhere else in our worldwide collection. Thus, at least one of the Canadian clonal lineages shares a common origin with A. areolatum isolates from the Southern Hemisphere. The source of the second clonal lineage is still unknown, but phylogenetic analyses show that MLG3 is isolated. More extended sampling is necessary to determine the origin of this fungal clonal lineage and investigate its probable symbiotic association with native North American Sirex.

Intraspecific variation and population structure of the German cockroach, Blattella germanica, revealed with RFLP analysis of the non-transcribed spacer region of ribosomal DNA

Little information is available on genetic variation within and between populations of pest cockroaches. In this study, intraspecific HindIII polymorphism was investigated in the German cockroach, Blattella germanica (Linnaeus) (Dictyoptera, Blattaria: Blattellidae), using restriction fragment length polymorphisms (RFLP) of the non-transcribed spacer (NTS) region of ribosomal DNA (rDNA). Individual male insects were collected from infestations at three different pig farms. Each population was characterized by HindIII restriction fragment frequencies and haplotype (a particular X-chromosome pattern) frequencies. The inheritance of the X-chromosome HindIII rDNA patterns over 12 generations (3 years) follows Mendelian patterns, and the stability of this polymorphic marker indicates infrequent genetic recombination of variable sites. Although pairwise genetic distance measures were uncorrelated with geographical distance, the pattern of genetic differentiation of the three cockroach populations suggests that human-mediated transport of cockroaches is an important force in shaping the population genetic structure of cockroach infestations, at least at the regional scale of 10-100 km. Sequence variation in the ribosomal NTS is a useful marker, and RFLP of rDNA is a simple, robust and reproducible technique for differentiating recently diverged cockroach populations.

Daldinia decipiens and Entonaema cinnabarina as fungal symbionts of Xiphydria wood wasps

The identity of symbiotic fungi associated with the Xiphydria spp. wood wasps was investigated using DNA analysis. The fungi were isolated from the mycangia of adult females of X. camelus, X. prolongata and X. longicollis reared from colonized logs of Alnus glutinosa, Salix alba and Quercus robur, respectively. Sequences of rDNA and beta-tubulin were obtained. Phylogenetic analysis based on the NJ method showed that the isolates from X. camelus clustered with Daldinia decipiens, whereas those of X. prolongata belonged to Entonaema cinnabarina. In X. longicollis, both symbiotic fungi (D. decipiens and E. cinnabarina) have been found. Morphological characteristics of the anamorphs are presented. In cultures of D. decipiens, sympodial holoblastic, as well as annelidic, conidiation was observed. So far, fruit bodies of D. decipiens have only been recorded from Betula spp. whereas the host spectrum of its wasp vectors covers predominantly oaks and alders. Fruiting bodies of E. cinnabarina do not occur in Central Europe. This is the first report of Entonaema as a symbiotic fungus of siricid wood wasps.

Identification of Chinese medicinal fungus Cordyceps sinensis by PCR-single-stranded conformation polymorphism and phylogenetic relationship

Fungi belonging to the Cordyceps species have long been used as food and herbal medicines in Asia and are especially popular as commercially available powdered supplements. Despite this acceptance and use, little is known of the phylogenetic relationships of the genus. Presently, the neighbor-joining method based on the ITS1, 5.8S rRNA, and ITS2 regions was used to construct a phylogenetic tree of 17 Cordyceps isolates. Five major groups were evident. Cordyceps sinensis was less closely related to 15 Cordyceps species but shared a closer relationship with Cordyceps agriota. PCR-single-stranded conformational polymorphism was applied to differentiate seven Cordyceps isolates: five were different from those used to construct the phylogenetic tree, based on differences in the internal spacer 2 (ITS2). The length of ITS2, amplified by primers 5.8SR and ITS4, vary between 334 and 400 bp. This segment could be used for intraspecies classification or detection of mutations and represents potential novel means of identification of this fungal genus in herbal medicines and in quality control applications in the fermentation industry.

Restriction mapping of the IGS region in Alternaria spp. reveals variable and conserved domains

Accurate identification of Alternaria spp. is dependent upon the production of diagnostic morphological characters under defined cultural conditions and the proper assessment of character variation. This process is often compromised by variation in laboratory facilities and technical expertise. To assist taxon identification and phylogenetic studies, restriction site information from the intergenic spacer (IGS) region of nuclear rDNA was evaluated. Restriction maps were constructed from 15 species of Alternaria and Stemphylium botryosum (telemorph Pleospora herbarum) for 11 restriction enzymes using a new method for restriction mapping based on differential priming of IGS amplicons. IGS fragment size varied among species from 2.2-3.9 kb. Based upon restriction site homology among closely-related and more distantly related species, the IGS region could be divided into conserved and variable domains. The conserved domain was approximately 0.75 kb in size and was located at the 3' end of the IGS region. Restriction site homology within this region was very high, especially among closely related taxa. The remainder of the region comprised the variable domain, which encompassed considerable differences in size and restriction sites among taxa. The presence or absence of restriction sites among taxa was analyzed using methods of neighbor-joining. Phylogenetic relationships based on this method were concordant with those previously resolved based upon other methods and other genomic regions.