The Biarzo case in northern Italy: is the temporal dynamic of swine mitochondrial DNA lineages in Europe related to domestication?

Genetically-based reconstructions of the history of pig domestication in Europe are based on two major pillars: 1) the temporal changes of mitochondrial DNA lineages are related to domestication; 2) Near Eastern haplotypes which appeared and then disappeared in some sites across Europe are genetic markers of the first Near Eastern domestic pigs. We typed a small but informative fragment of the mitochondrial DNA in 23 Sus scrofa samples from a site in north eastern Italy (Biarzo shelter) which provides a continuous record across a ≈6,000 year time frame from the Upper Palaeolithic to the Neolithic. We additionally carried out several radiocarbon dating. We found that a rapid mitochondrial DNA turnover occurred during the Mesolithic, suggesting that substantial changes in the composition of pig mitochondrial lineages can occur naturally across few millennia independently of domestication processes. Moreover, so-called Near Eastern haplotypes were present here at least two millennia before the arrival of Neolithic package in the same area. Consequently, we recommend a re-evaluation of the previous idea that Neolithic farmers introduced pigs domesticated in the Near East, and that Mesolithic communities acquired domestic pigs via cultural exchanges, to include the possibility of a more parsimonious hypothesis of local domestication in Europe.

Phylogenetics of the pademelons (Macropodidae: Thylogale) and historical biogeography of the Australo-Papuan region.

Australia and New Guinea share a common biogeographical history and unique vertebrate fauna. Investigation of genetic relationships among the wet forest-restricted pademelons (Macropodidae: Thylogale) provides insight into the historical connections between the two regions and the evolution of the Australasian marsupial fauna. Molecular phylogenetic relationships among Thylogale species were analysed using mitochondrial (12S rRNA and cytochrome b) and nuclear (omega-globin intron) sequence data with Bayesian and maximum likelihood methods. Australian species were resolved as well-supported, monophyletic clades, whereas endemic New Guinean species did not form clades consistent with current morphological taxonomy. Estimates of divergence using a Bayesian relaxed molecular clock model with standard mammalian nucleotide substitution rates indicated radiation of the genus in Australia in the mid to late Miocene. Persistence of Australian species of Thylogale in both southern temperate and northern tropical forests throughout the drying of the Australian continent can be attributed to their having a greater dietary flexibility than other browsing forest macropods. Divergence of the endemic New Guinean lineage occurred in the late Miocene to early Pliocene, indicating the presence of a partially forested landbridge connecting Australia and New Guinea during the Miocene. Mid-Pleistocene divergence between subspecies of the trans-Torresian T. stigmatica implies gene flow during glacial maxima between forest populations in the southern lowlands of New Guinea and the northern Cape York region of Australia. Complex structuring and relatively limited differentiation among populations of the endemic New Guinean species appears to have been influenced by the uplift of land and climate-induced redistribution of forest habitats during the late Pliocene and Pleistocene period. This is in strong contrast to the long evolutionary history and comparatively deep genetic divergence of Thylogale species in Australia. Further evaluation of the species status of the New Guinean Thylogale using more informative nuclear markers and extensive sampling is required.

Response of a southern temperate marsupial, the Tasmanian pademelon (Thylogale billardierii), to historical and contemporary forest fragmentation.

Despite only limited Pleistocene glacial activity in the southern hemisphere, temperate forest species experienced complex distributional changes resulting from the combined effects of glaciation, sea level change and increased aridity. The effects of these historical processes on population genetic structure are now overlain by the effects of contemporary habitat modification. In this study, 10 microsatellites and 629 bp of the mitochondrial control region were used to assess the effects of historical forest fragmentation and recent anthropogenic habitat change on the broad-scale population genetic structuring of a southern temperate marsupial, the Tasmanian pademelon. A total of 200 individuals were sampled from seven sites across Tasmania and two islands in Bass Strait. High mitochondrial and nuclear genetic diversity indicated the maintenance of large historical population sizes. There was weak phylogeographical structuring of haplotypes, although all King Island haplotypes and three Tasmanian haplotypes formed a divergent clade implying the mid-Pleistocene isolation of a far northwestern population. Both the mitochondrial and nuclear data indicated a division of Tasmanian populations into eastern and western regions. This was consistent with a historical barrier resulting from increased aridity in the lowland 'midlands' region during glacial periods, and with a contemporary barrier resulting from recent habitat modification in that region. In Tasmania, gene flow appears to have been relatively unrestricted during glacial maxima in the west, while in the east there was evidence for historical expansion from at least one large glacial refuge and recolonization of Flinders Island.