back

Systematics of the weevil subfamilies Scolytinae and Platypodinae (bark and timber beetles):
The project aims towards a predictive classification of Scolytinae and Platypodinae at the tribal level. These groups have not yet been analysed phylogenetically in sufficient detail, and high levels of tribal polyphyly are expected (c.f. Farrell et al, 2001). Tribal and generic monophyly, the relationship of Platypodinae to Scolytinae, and the relationship of these within the larger group of true weevils (Curculionidae) will be tested using large numbers of described and new morphological characters, and several nuclear DNA gene fragments from EF-1alpha, Histone-H3, 28S and CAD. A stable and predictive classification will further enable tests on various hypotheses related to the evolution of breeding in dead wood, including morphological modifications to the wood-boring habit, the evolutionary origins of fungal symbiosis, and the evolutionary dynamics of host-plant and host-tissue exploitation. In collaboration with Anthony Cognato and Brian Farrell.


Genetic diversity and speciation in ancient inbreeding lineages:
Genetic diversity drives evolution. Processes which erode genetic variation, such as self-fertilization and sibling mating, are therefore expected to reduce the long-term survival of inbred lineages. Paradoxically, we do find ancient, species-rich lineages in nature which have been inbreeding for millions of years. What sorts of population genetic processes facilitate and maintain sufficient genetic diversity in such lineages? How can closely inbred populations maintain genetic variability sufficient to foster genetic and ecological divergence that ultimately results in new species? Answers will address a central question of population genetics: how much genetic variation within or between populations is adaptive in coping with new environmental challenges? This project seeks to elucidate patterns of genetic diversity, population subdivision and speciation in nine different widespread bark beetle species (Curculionidae: Scolytinae) that regularly inbreed by within-family mating. The project is novel in including many species in one comparative study, enabling us to distinguish ecological idiosyncrasies from the genetic processes related to inbreeding. An ancient origin for inbreeding in at least two bark beetle clades strengthens this study further by removing the confusing effects of a recent origin of inbreeding, allowing us to focus instead on the long-term evolutionary effects of inbreeding on lineage survival and proliferation. Reconstructing genealogies using mitochondrial and nuclear DNA allows direct comparison of genetic diversity between ecologically similar inbreeding and outbreeding species. Our results will furthermore shed light on the general problem of identifying cryptic lineages, and how deep divergence between cryptic lineages may complicate species identification in a DNA barcoding framework


Inferring species boundaries and historical assembly of ecologically similar bark beetle complexes in Scandinavia:
Parallel colonisation of Scandinavian forests after the last glacial cycle has led to several examples of ecologically similar species of closely related bark beetles that utilise the same host plant. This project investigate five such species complexes that contain species or subspecies with unclear morphological differences. Based on nuclear and mitochondrial DNA sequences, genealogical histories will be reconstructed for each complex to identify correct species boundaries, the level of gene flow between morphs, and to reconstruct the colonization routes and historical assembly of the Scandinavian members of each species complex. Target groups are the Hylastes ater complex (3 spp), the Hylastes attenuatus complex (4-6 spp), the Polygraphus poligraphus complex (3-5 spp), the Dryocoetes autographus complex, and the Crypturgus cinereus and pusillus complexes (2-6 spp).

Molecular identification of Scandinavian bark beetles using on-line DNA-sequence databases:
Many bark beetles of the weevil subfamily Scolytinae are difficult to identify correctly based on morphological characters. Short sequences of Cytochrome Oxidase I and Elongation Factor 1-alpha are used to identify individuals to species based on sequence similarity measures and Neighbour Joining clustering techniques. One particular advantage of this method is the possibility for identifying damaged specimens, or larval stages of little diagnostic value. The database will be available on-line (Hosted by Howard Ross, Bioinformatics institute, Auckland University), where blasting of sequences from unidentified individuals group with their closest match. However, several species complexes exist in the Palearctic that may not be readily identified by a simple string of DNA bases alone. These taxa will be dealt with in a separate project (see next).

Application of phylogeographical tools in reconstructing the historical assembly of component communities - Aphanarthrum bark beetles on Euphorbia plants in the Canary Islands:

Phylogeography of widespread tube worms associated with fouling on ships (with PhD student Toril Moen):