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 lineage s 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 f oster 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 challenge s? 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 co mplicate species identification in a DNA barcoding framework.