DNA taxonomy and phylogeography of beetles of the Falkland Islands (Islas Malvinas)

Abstract

The Falkland biota are generally considered to be derived from the nearest continental source in Patagonian South America, yet they harbor many endemic species whose taxonomy and evolutionary history remains insufficiently understood. Comprehensive sampling of Coleoptera over two field seasons from numerous sites across the Falkland archipelago produced representatives of 55 morphologically separable species, assigned to 35 genera and 13 families of Coleoptera. Partial mitochondrial Cytochrome Oxidase subunit I and 16S ribosomal RNA genes were sequenced for 283 individuals. These sequences formed 55 clusters under a Yule-Coalescent model that largely conformed to Linnean species while deep-level phylogenetic relationships were broadly congruent with the higher level classification. Detailed analysis of the most diverse families Carabidae and Curculionidae addressed the question about the age and persistence in situ of Falkland biota, showing that separation of sister species within genera based on molecular clock estimates pre-dated the Pleistocene in all cases. Intra-specific diversity of mtDNA haplotypes and nucleotide diversity were high in most species, while intra-population variation was equally high and showed local differentiation of populations, but there was no isolation-by-distance relationship. Taken together, these observations indicate that ancient endemics are unlikely to be due to the recent establishment from a source elsewhere, but have persisted in situ. The observed patterns differ greatly from those in climatically similar areas of the Northern Hemisphere. They do not support the view that postglacial ranges of insects near the limits of former glaciations are merely the result of redistribution due to changing climate.