Molecular phylogeny and biogeography of the weevil subfamily Platypodinae reveals evolutionarily conserved range patterns

Body size and sequence of host colonisation predict the presence of acoustic signalling in beetles

Acoustic communication is widespread in beetles, is often sexually dimorphic, and plays a significant role in behaviours such as premating recognition, courtship, and copulation. However, the factors that determine the presence or absence of acoustic signalling in a given species remain unclear. We examined acoustic communication in bark beetles (Scolytinae) and pinhole borers (Platypodinae), which are two speciose groups with widespread sound production capabilities. We show that body size along with the sequence of host colonisation predict the presence of acoustic communication, and report, for the first time in the animal kingdom, a size limit-1.9 mm-below which acoustic signalling ceases to be present.

The Potential of Esteya spp. for the Biocontrol of the Pinewood Nematode, Bursaphelenchus xylophilus

The pinewood nematode (PWN), Bursaphelenchus xylophilus, is the causal agent of pine wilt disease (PWD) and a quarantine organism in many countries. Managing PWD involves strict regulations and heavy contingency plans, and present climate change scenarios predict a spread of the disease. The urgent need for sustainable management strategies has led to an increasing interest in promising biocontrol agents capable of suppressing the PWN, like endoparasitic nematophagous fungi of the Esteya genus. Here, we review different aspects of the biology and ecology of these nematophagous fungi and provide future prospects.

Phylogenomic and mitogenomic data can accelerate inventorying of tropical beetles during the current biodiversity crisis

Conservation efforts must be evidence-based, so rapid and economically feasible methods should be used to quantify diversity and distribution patterns. We have attempted to overcome current impediments to the gathering of biodiversity data by using integrative phylogenomic and three mtDNA fragment analyses. As a model, we sequenced the Metriorrhynchini beetle fauna, sampled from ~700 localities in three continents. The species-rich dataset included ~6,500 terminals, ~1,850 putative species delimited at 5% uncorrected pairwise threshold, possibly ~1,000 of them unknown to science. Neither type of data could alone answer our questions on biodiversity and phylogeny. The phylogenomic backbone enabled the integrative delimitation of robustly defined natural genus-group units that will inform future research. Using constrained mtDNA analysis, we identified the spatial structure of species diversity, very high species-level endemism, and a biodiversity hotspot in New Guinea. We suggest that focused field research and subsequent laboratory and bioinformatic workflow steps would substantially accelerate the inventorying of any hyperdiverse tropical group with several thousand species. The outcome would be a scaffold for the incorporation of further data from environmental sequencing and ecological studies. The database of sequences could set a benchmark for the spatiotemporal evaluation of biodiversity, would support evidence-based conservation planning, and would provide a robust framework for systematic, biogeographic, and evolutionary studies.

Aggregation Pheromones of Weevils (Coleoptera: Curculionidae): Advances in the Identification and Potential Uses in Semiochemical-Based Pest Management Strategies

With approximately 83,000 species described, Curculionidae is the largest family of beetles, comprising more than 80% of all weevil species worldwide. Many species of Curculionidae attack a wide range of native and orchards crops, as well as globally important stored products such as grains, flour, and seeds, being responsible for significant environmental and economic losses. This work provides an overview of the research in the identification of aggregation pheromones of Curculionidae, and their potential contributions to the development of semiochemical-based pest management strategies. The synergistic effect of the host plant volatiles in the attractiveness of weevil pheromones is also briefly reported, demonstrating the important role of these additional attractants in the chemical communication of curculionids.

Origin and evolution of fungus farming in wood-boring Coleoptera - a palaeontological perspective

Insect-fungus mutualism is one of the better-studied symbiotic interactions in nature. Ambrosia fungi are an ecological assemblage of unrelated fungi that are cultivated by ambrosia beetles in their galleries as obligate food for larvae. Despite recently increased research interest, it remains unclear which ecological factors facilitated the origin of fungus farming, and how it transformed into a symbiotic relationship with obligate dependency. It is clear from phylogenetic analyses that this symbiosis evolved independently many times in several beetle and fungus lineages. However, there is a mismatch between palaeontological and phylogenetic data. Herein we review, for the first time, the ambrosia system from a palaeontological perspective. Although largely ignored, families such as Lymexylidae and Bostrichidae should be included in the list of ambrosia beetles because some of their species cultivate ambrosia fungi. The estimated origin for some groups of ambrosia fungi during the Cretaceous concurs with a known high diversity of Lymexylidae and Bostrichidae at that time. Although potentially older, the greatest radiation of various ambrosia beetle lineages occurred in the weevil subfamilies Scolytinae and Platypodinae during the Eocene. In this review we explore the evolutionary relationship between ambrosia beetles, fungi and their host trees, which is likely to have persisted for longer than previously supposed.

A new species, a new combination, and a new record of Crossotarsus Chapuis, 1865 (Coleoptera, Curculionidae, Platypodinae) from China

This study describes a new species, Crossotarsusbeaveri Lai & Wang, sp. nov., designates a new combination, C.brevis (Browne, 1975, comb. nov. from Platypus Herbst, 1793), and notes a new record, C.emorsus Beeson, 1937, from China. Genetic data from four genes indicate that the new species and C.brevis form a clade clustered with other Crossotarsus species. Molecular phylogeny and morphological characters support their taxonomic placement.

Ophiostomatalean fungi associated with wood boring beetles in South Africa including two new species

Ambrosia beetles are small wood inhabiting members of the Curculionidae that have evolved obligate symbioses with fungi. The fungal symbionts concentrate nutrients from within infested trees into a usable form for their beetle partners, which then utilize the fungi as their primary source of nutrition. Ambrosia beetle species associate with one or more primary symbiotic fungal species, but they also vector auxiliary symbionts, which may provide the beetle with developmental or ecological advantages. In this study we isolated and identified ophiostomatalean fungi associated with ambrosia beetles occurring in a native forest area in South Africa. Using a modified Bambara beetle trap, living ambrosia beetle specimens were collected and their fungal symbionts isolated. Four beetle species, three Scolytinae and one Bostrichidae, were collected. Five species of ophiostomatalean fungi were isolated from the beetles and were identified using both morphological characters and DNA sequence data. One of these species, Raffaelea sulphurea, was recorded from South Africa for the first time and two novel species were described as Ceratocystiopsis lunata sp. nov. and Raffaelea promiscua sp. nov.

First phylogenetic analysis of Dryophthorinae (Coleoptera, Curculionidae) based on structural alignment of ribosomal DNA reveals Cenozoic diversification

Dryophthorinae is an economically important, ecologically distinct, and ubiquitous monophyletic group of pantropical weevils with more than 1,200 species in 153 genera. This study provides the first comprehensive phylogeny of the group with the aim to provide insights into the process and timing of diversification of phytophagous insects, inform classification and facilitate predictions. The taxon sampling is the most extensive to date and includes representatives of all five dryophthorine tribes and all but one subtribe. The phylogeny is based on secondary structural alignment of 18S and 28S rRNA totaling 3,764 nucleotides analyzed under Bayesian and maximum likelihood inference. We used a fossil-calibrated relaxed clock model with two approaches, node-dating and fossilized birth-death models, to estimate divergence times for the subfamily. All tribes except the species-rich Rhynchophorini were found to be monophyletic, but higher support is required to ascertain the paraphyly of Rhynchophorini with more confidence. Nephius is closely related to Dryophthorini and Stromboscerini, and there is strong evidence for paraphyly of Sphenophorina. We find a large gap between the divergence of Dryophthorinae from their sister group Platypodinae in the Jurassic-Cretaceous boundary and the diversification of extant species in the Cenozoic, highlighting the role of coevolution with angiosperms in this group.

Patterns of host tree use within a lineage of saproxlic snout-less weevils (Coleoptera: Curculionidae: Scolytinae: Scolytini)

The influence of plants in the diversification of herbivorous insects, specifically those that utilize moribund and dead hosts, is little explored. Host shifts are expected because the effectiveness of toxic secondary chemicals is lessened by decay of dead plants. Feeding on dead plants also releases herbivorous insect lineages from diversifying within a particular plant lineage. Thus, phylogenetic constraints on the herbivorous insect lineage imposed by the host plants are diminished and repeated patterns of species diversification in an association with unrelated host trees is hypothesized (i.e., taxon cycle). Scolytini, a diverse weevil tribe, specialize on many different dead and moribund plant taxa as a source of food. These species and their hosts offer an opportunity to examine the association between dead host plants and the extent of phylogenetic constraints. A phylogeny of the Scolytini was reconstructed with likelihood and Bayesian analyses of DNA sequence data from nuclear (28S, CAD, ArgK) and mitochondrial (COI) genes. Ancestral host usage and geography was reconstructed using likelihood criteria and conservation of host use was tested. Results supported a monophyletic Scolytini, Ceratolepis, Loganius, and a paraphyletic Scolytus, Camptocerus and Cnemonyx. Diversification of the Scolytini generally occurred well after their host taxa diversified and suggests a sequential evolution of host use. In this scenario the beetle imposes little selection pressure on the tree but the tree provides a platform for beetle evolution. Major changes in host tree use occurred during periods of global cooling associated with changes in beetle biogeography. Diversification of beetles occurred on common and widespread hosts and there was likely a single origination of conifer-feeding from angiosperm-feeding species during the early Pliocene and a radiation of beetle species from the Palearctic to the Nearctic. Overall, the observed patterns of Scolytini host use are conserved and are similar to those expected in a taxon pulse diversification. That is, after a host switch to an unrelated tree, the beetles diversify within the host plant lineage. The need to locate an ephemeral food resource, i.e., a dying tree, likely maintains host specificity once a host shift occurs. These findings suggest that characteristics of dead and moribund host plants (e.g. secondary chemicals) influence the diversification of these saproxlic weevils despite the reduction of selection pressures.

A phylogenetic and taxonomic assessment of Afrotropical Micracidini (Coleoptera, Scolytinae) reveals a strong diversifying role for Madagascar

Afrotropical bark beetle genera in the tribe Micracidini are revised and an identification key provided. The new classification is based on phylogenetic analyses of five molecular markers (COI, EF-1α, 28S, PABP1, CAD) in combination with morphological characters. Five new genera are erected and one genus synonymized, resulting in a total of 11 valid genera: Lanurgus Eggers, 1920, Traglostus Schedl, 1938, Pseudomicracis Eggers, 1920 (=Saurotocis Wood, 1984 syn. nov.), Phloeocurus Wood, 1984, Afromicracis Schedl, 1959, Dendrochilus Schedl, 1959, Neomicracis Jordal gen. nov., Leiomicracis Jordal gen. nov., Diplotrichus Jordal gen. nov., Pseudolanurgus Jordal gen. nov., Microlanurgus Jordal gen. nov. The following new species are described to be included in the new genera: Leiomicracis aurea Jordal sp. nov., Neomicracis squamigera Jordal sp. nov., both from Tanzania, and Microlanurgus bicolor Jordal sp. nov. and Microlanurgus ater Jordal sp. nov., from Madagascar. The following new synonyms and new combinations are proposed: Afromicracis dubius (Schedl, 1950) (=Afromicracis angolensis Schedl, 1962 syn. nov.), Afromicacis elongatulus (Schedl, 1977) comb. nov.,Afromicracis jasminiae (Schedl 1957) comb. nov. (=Dendrochilus mikaniae Schedl 1957 syn. nov.), Afromicracis robustus (Schedl 1957) comb. nov. (=Dendrochilus arundinarius Schedl 1957 syn. nov., =Hypothenemus bambusae Browne, 1970 syn. nov., =Dendrochilus filum Schedl, 1977 syn. nov.) (all from Dendrochilus), Afromicracis setifer (Schedl 1957) comb. nov. (Mimiocurus), Lanurgus longipilis (Schedl, 1958) comb. nov., Lanurgus pubescens (Schedl, 1961) comb. nov. (both from Traglostus), Diplotrichus catenatus (Schedl, 1953) comb. nov.,Diplotrichus elongatus (Schedl, 1950) comb. nov.,Diplotrichus euphorbia (Schedl, 1961) comb. nov.,Diplotrichus gracilis (Schedl, 1958) comb. nov.,Diplotrichus minor (Schedl, 1950) comb. nov (=Lanurgus frontalis Schedl, 1953 syn. Nov.), Diplotrichus obesus (Schedl, 1953) comb. nov., Diplotrichus pygmaeus (Schedl, 1965) comb. nov., Diplotrichus rugosipes (Schedl, 1961) comb. nov., Diplotrichus subdepressus (Schedl, 1965) comb. nov., Diplotrichus widdringtoniae (Schedl, 1962) comb. nov. (all from Lanurgus), Diplotrichus ignotus (Schedl, 1965) comb. nov. (Pseudomicracis), Pseudolanurgus harunganae (Schedl, 1961) comb. nov. (=Lanurgus cribrellus Schedl, 1965 syn. nov.), Pseudolanurgus bugekeae (Schedl, 1957) comb. nov. (both from Pseudomicracis), Pseudolanurgus minutissimus (Schedl, 1961) comb. nov. (Lanurgus), Pseudomicracis dispar (Schedl, 1961) comb. nov., Pseudomicracis tomicoides (Schedl, 1961) comb. nov. (both from Saurotocis). The following taxa were transferred to genera in other tribes: Acanthotomicus intermedius (Schedl, 1977) comb. nov., Xylocleptes villiersi (Lepesme, 1942) comb. nov. (both from Dendrochilus); Eidophelus agnathus (Schedl, 1942) comb. nov., and Eidophelus ciliatipennis (Schedl, 1979) comb. nov. (all from Miocryphalus). The following five species were included in Karlseniusgen. nov. (Trypophloeini): Karlsenius klainedoxae (Schedl, 1957) comb. nov., Karlsenius nitidum (Schedl, 1965) comb. nov., Karlsenius nigrinum (Schedl, 1957) comb. nov., and Karlsenius attenuatus (Eggers, 1935) comb. nov. (from Miocryphalus), and Karlsenius ghanaensis (Schedl, 1977) comb. nov. (from Eidophelus). A time-tree and biogeographical analysis suggested that Madagascar was colonized only once in Micracidini, from East Africa soon after the origin of the tribe in late Cretaceous. Multiple re-colonisations from Madagascar to the mainland have contributed to further diversification of a tribe which is otherwise highly restricted in geographical distribution.

Type and distribution of sensilla in the antennae of Euplatypus parallelus (F.) (Coleoptera: Curculionidea, Platypodinae)

Euplatypus parallelus (F.) (Coleoptera: Curculionidea) is the most destructive cosmopolitan insect pest of the Platypodinae. Pheromone-based luring agents are used currently in controlling bark beetle. Antennae are the primary insect organs sensing volatiles of host trees and pheromones of pioneer males. We studied the external morphology of antennae and the type, distribution, and the number of the beetle sensilla. Our results show E. parallelus have a geniculate antenna composed of 6 segments, namely the scape, 4-segmented funicle and club. Ninety-seven percent of the antennal sensors were distributed in the club, and 3% were distributed in the scape and funicle. 6 types of sensilla on the antennae were found, including sensilla trichodea (subtypes: STI, STII and STIII), sensilla basiconica (subtypes: SBI, SBII, SBIII and SBIV), sensilla chaetica (subtypes: SChI, SChII and SChIII), as well as sensilla coeloconica, sensilla campaniform and sensilla furcatea. There was no significant difference in the type, distribution and number of sensilla in males and females. No significant difference in the shape and distribution of antennae was found between sexes, but the length of antennae and the number of SChI, SChII, STI, SBI, SBIII and SBIV were significantly larger in females than males. We revealed the external cuticular structure of the antennae in E. parallelus, which can be used to guide future electrophysiological investigations to understand the ability of this beetle to detect semiochemicals.

The Risk of Bark and Ambrosia Beetles Associated with Imported Non-Coniferous Wood and Potential Horizontal Phytosanitary Measures

Many bark and ambrosia beetle species (Coleoptera: Scolytinae and Platypodinae) are known to have spread worldwide in relation to international trade. Concerns have been expressed within the European and Mediterranean Plant Protection Organization (EPPO) about recent introductions of non-indigenous species of these groups. Regulation of the non-coniferous wood trade into many EPPO member countries is currently not sufficient to cover such risks. In 2018–2019, an EPPO study on the risk of bark and ambrosia beetles associated with imported non-coniferous wood was carried out, and the key characteristics contributing to the pest risk from introduced species were determined using expert consensus. This paper summarizes the key findings of the study, which are available in full detail on the EPPO website. The study identified biological and other risk factors and illustrated them with examples from 26 beetle species or groups of species known to be invasive or posing a threat to plant health. These representative species were classified into three categories based on known damage and level of uncertainty. In the present article, factorial discriminant analyses were used to identify features of bark and ambrosia beetle biology associated with damage caused and invasiveness. Based on the information assembled and consideration of the risk factors, it was recommended that in order to prevent the introduction of new bark and ambrosia beetles via non-coniferous wood commodities, horizontal phytosanitary measures should be adopted, irrespective of the host plant species and the origin (i.e., for all genera of non-coniferous woody plants and from all origins). Phytosanitary measures are presented here for various wood commodities.

Fine structure of mouthparts and forelegs of Euplatypus parallelus (Coleoptera: Curculionidae) with emphasis on the behavior of gallery excavation

Euplatypus parallelus (F.) (Coleoptera: Curculionidae) is one of the most invasive species of all the Platypodinae. It penetrates the xylem and oviposits in its host trees thereby weakening the trunk causing them to break under extreme conditions. Since the beetle has evolved effective drilling mouthparts enough to make wood tunnels, we used a field emission scanning electron microscopy to describe the sexual difference in mouthparts and forelegs morphology of the beetle. E. parallelus has chewing type mouthparts composed of a labrum, a pair of mandibles, a pair of maxillae, and a labium. In females, the size of maxillary palpi, submentum, prementum, and labial palpi are significantly larger than males. E. parallelus forelegs were walking type composed of procoxa, protrochanter, profemur, protibia, protarsus, and propretarsus. We observed no significant differences between the forelegs of males and females, but the procoxa of the males was slightly larger than that of females. The structural differences in mouthparts and forelegs between females and males indicated that females invest more time in gallery excavation than males. Possible functional relationships of these structures are discussed. These studies revealed the mechano-dynamic characteristics of E. parallelus and provided a theoretical basis for exploring the behavior of this beetle.

The Weevil Fauna Preserved in Burmese Amber—Snapshot of a Unique, Extinct Lineage (Coleoptera: Curculionoidea)

Only a few weevils have been described from Burmese amber, and although most have been misclassified, they show unusual and specialised characters unknown in extant weevils. In this paper, we present the results of a study of a much larger and more diverse selection of Burmese amber weevils. We prepared all amber blocks to maximise visibility of structures and examined these with high-magnification light microscopy as well as CT scanning (selected specimens). We redescribe most previously described taxa and describe 52 new species in 26 new genera, accompanied by photographs. We compare critical characters of these weevils with those of extant taxa and outline the effects of distortion on their preservation and interpretation. We conclude that only two weevil families are thus far represented in Burmese amber, Nemonychidae and a newly recognised family, Mesophyletidae, which appears closely related to Attelabidae but cannot be accommodated in this family. The geniculate antennae and long rostrum with exodont mandibles of most Mesophyletidae indicate that they were highly specialised phytophages of early angiosperms preserved in the amber, likely ovipositing in flowers or seeds. This weevil fauna appears to represent an extinct mid-Cretaceous ecosystem and fills a critical gap in the fossil record of weevils.

Monogamous sperm storage and permanent worker sterility in a long-lived ambrosia beetle

The lifetime monogamy hypothesis claims that the evolution of permanently unmated worker castes always requires maximal full-sibling relatedness to be established first. The long-lived diploid ambrosia beetle Austroplatypus incompertus (Schedl) is known to be highly social, but whether it has lifetime sterile castes has remained unclear. Here we show that the gallery systems of this beetle inside the heartwood of live Eucalyptus trees are always inhabited by a single core family, consisting of a lifetime-inseminated mother, permanently unmated daughter workers, and immatures that are always full siblings to each other and their adult caretakers. Overall sex ratios are even. Males always disperse and only survive as stored sperm, but female offspring either disperse to mate and found their own colony or assume unmated worker roles, probably surviving for many years without any reproductive potential because tarsal loss precludes later dispersal. A well-supported Platypodinae phylogeny has allowed us to infer that parental monogamy evolved before a lifetime-unmated worker caste emerged, confirming the prediction that monogamy and full-sibling relatedness are necessary conditions for the evolution of such workers. The initially very challenging but ultimately long-term stable nesting habitat in live trees appears to have provided the crucial benefit/cost factor for maintaining selection for permanently sterile workers after strict monogamy and lifetime sperm storage had become established in this curculionid coleopteran lineage.

Know your farmer: Ancient origins and multiple independent domestications of ambrosia beetle fungal cultivars

Bark and ambrosia beetles are highly specialized weevils (Curculionidae) that have established diverse symbioses with fungi, most often from the order Ophiostomatales (Ascomycota, Sordariomycetes). The two types of beetles are distinguished by their feeding habits and intimacy of interactions with their symbiotic fungi. The tree tissue diet of bark beetles is facilitated by fungi, while ambrosia beetles feed solely on fungi that they farm. The farming life history strategy requires domestication of a fungus, which the beetles consume as their sole food source. Ambrosia beetles in the subfamily Platypodinae originated in the mid-Cretaceous (119-88 Ma) and are the oldest known group of farming insects. However, attempts to resolve phylogenetic relationships and the timing of domestication events for fungal cultivars have been largely inconclusive. We sequenced the genomes of 12 ambrosia beetle fungal cultivars and bark beetle associates, including the devastating laurel wilt pathogen, Raffaelea lauricola, to estimate a robust phylogeny of the Ophiostomatales. We find evidence for contemporaneous diversification of the beetles and their associated fungi, followed by three independent domestication events of the ambrosia fungi genus Raffaelea. We estimate the first domestication of an Ophiostomatales fungus occurred ~86 Ma, 25 million years earlier than prior estimates and in close agreement with the estimated age of farming in the Platypodinae (96 Ma). Comparisons of the timing of fungal domestication events with the timing of beetle radiations support the hypothesis that the first large beetle radiations may have spread domesticated "ambrosia" fungi to other fungi-associated beetle groups, perhaps facilitating the evolution of new farming lineages.

The Ambrosia Symbiosis: From Evolutionary Ecology to Practical Management

The ambrosia beetle-fungus farming symbiosis is more heterogeneous than previously thought. There is not one but many ambrosia symbioses. Beetle-fungus specificity is clade dependent and ranges from strict to promiscuous. Each new origin has evolved a new mycangium. The most common relationship with host trees is colonization of freshly dead tissues, but there are also parasites of living trees, vectors of pathogenic fungi, and beetles living in rotten trees with a wood-decay symbiont. Most of these strategies are driven by fungal metabolism whereas beetle ecology is evolutionarily more flexible. The ambrosia lifestyle facilitated a radiation of social strategies, from fungus thieves to eusocial species to communities assembled by attraction to fungal scent. Although over 95% of the symbiotic pairs are economically harmless, there are also three types of pest damage: tree pathogen inoculation, mass accumulation on susceptible hosts, and structural damage. Beetles able to colonize live tree tissues are most likely to become invasive pests.

Genomic Mining of Phylogenetically Informative Nuclear Markers in Bark and Ambrosia Beetles

Deep level insect relationships are generally difficult to resolve, especially within taxa of the most diverse and species rich holometabolous orders. In beetles, the major diversity occurs in the Phytophaga, including charismatic groups such as leaf beetles, longhorn beetles and weevils. Bark and ambrosia beetles are wood boring weevils that contribute 12 percent of the diversity encountered in Curculionidae, one of the largest families of beetles with more than 50000 described species. Phylogenetic resolution in groups of Cretaceous age has proven particularly difficult and requires large quantity of data. In this study, we investigated 100 nuclear genes in order to select a number of markers with low evolutionary rates and high phylogenetic signal. A PCR screening using degenerate primers was applied to 26 different weevil species. We obtained sequences from 57 of the 100 targeted genes. Sequences from each nuclear marker were aligned and examined for detecting multiple copies, pseudogenes and introns. Phylogenetic informativeness (PI) and the capacity for reconstruction of previously established phylogenetic relationships were used as proxies for selecting a subset of the 57 amplified genes. Finally, we selected 16 markers suitable for large-scale phylogenetics of Scolytinae and related weevil taxa.

Globally distributed Xyleborus species reveal recurrent intercontinental dispersal in a landscape of ancient worldwide distributions

BACKGROUND

Invasive species can have devastating effects on native ecosystems and therefore impose a significant threat to human welfare. The introduction rate of invasive species has accelerated dramatically in recent times due to human activity (anthropogenic effects), with a steadily growing pool of widespread tramp species. We present an in-depth analysis of four pantropical species of Xyleborus ambrosia beetles (Xyleborus volvulus, Xyleborus perforans, Xyleborus ferrugineus, and Xyleborus affinis) with similar ecology (fungus cultivation in dead wood), reproductive biology (permanent inbreeding) and genetic system (haplodiploidy). The unique combination of reproductive traits and broad host plant usage pre-adapts these beetles for colonizing of new areas.

RESULTS

We found that all four species were broadly distributed long before human-assisted dispersal became common, and that the impact of anthropogenic effects varied among the species. For X. volvulus, X. perforans, and X. affinis there was evidence of ancient establishment in numerous regions, but also of abundant recent introductions into previously colonized areas. For X. ferrugineus, we found clear biogeographical structuring of old clades, but little evidence for recent successful introductions.

CONCLUSIONS

Our results indicate that current human-aided transoceanic dispersal has strongly affected the genetic makeup of three of the species in this study. However, current biogeographical patterns of all four species are equally, if not more strongly, influenced by ancient establishment on different continents.