Low-cost cross-taxon enrichment of mitochondrial DNA using in-house synthesised RNA probes

Lions and brown bears colonized North America in multiple synchronous waves of dispersal across the Bering Land Bridge

The Bering Land Bridge connecting North America and Eurasia was periodically exposed and inundated by oscillating sea levels during the Pleistocene glacial cycles. This land connection allowed the intermittent dispersal of animals, including humans, between Western Beringia (far northeast Asia) and Eastern Beringia (northwest North America), changing the faunal community composition of both continents. The Pleistocene glacial cycles also had profound impacts on temperature, precipitation and vegetation, impacting faunal community structure and demography. While these palaeoenvironmental impacts have been studied in many large herbivores from Beringia (e.g., bison, mammoths, horses), the Pleistocene population dynamics of the diverse guild of carnivorans present in the region are less well understood, due to their lower abundances. In this study, we analyse mitochondrial genome data from ancient brown bears (Ursus arctos; n = 103) and lions (Panthera spp.; n = 39), two megafaunal carnivorans that dispersed into North America during the Pleistocene. Our results reveal striking synchronicity in the population dynamics of Beringian lions and brown bears, with multiple waves of dispersal across the Bering Land Bridge coinciding with glacial periods of low sea levels, as well as synchronous local extinctions in Eastern Beringia during Marine Isotope Stage 3. The evolutionary histories of these two taxa underline the crucial biogeographical role of the Bering Land Bridge in the distribution, turnover and maintenance of megafaunal populations in North America.

Recovery of chloroplast genomes from medieval millet grains excavated from the Areni-1 cave in southern Armenia

Panicum miliaceum L. was domesticated in northern China at least 7000 years ago and was subsequentially adopted in many areas throughout Eurasia. One such locale is Areni-1 an archaeological cave site in Southern Armenia, where vast quantities archaeobotanical material were well preserved via desiccation. The rich botanical material found at Areni-1 includes P. miliaceum grains that were identified morphologically and¹⁴C dated to the medieval period (873 ± 36 CE and 1118 ± 35 CE). To investigate the demographic and evolutionary history of the Areni-1 millet, we used ancient DNA extraction, hybridization capture enrichment, and high throughput sequencing to assemble three chloroplast genomes from the medieval grains and then compared these sequences to 50 modern P. miliaceum chloroplast genomes. Overall, the chloroplast genomes contained a low amount of diversity with domesticated accessions separated by a maximum of 5 SNPs and little inference on demography could be made. However, in phylogenies the chloroplast genomes separated into two clades, similar to what has been reported for nuclear DNA from P. miliaceum. The chloroplast genomes of two wild (undomesticated) accessions of P. miliaceum contained a relatively large number of variants, 11 SNPs, not found in the domesticated accessions. These results demonstrate that P. miliaceum grains from archaeological sites can preserve DNA for at least 1000 years and serve as a genetic resource to study the domestication of this cereal crop.

Ancestral mitogenome capture of the Southeast Asian banded linsang

Utilising a reconstructed ancestral mitochondrial genome of a clade to design hybridisation capture baits can provide the opportunity for recovering mitochondrial sequences from all its descendent and even sister lineages. This approach is useful for taxa with no extant close relatives, as is often the case for rare or extinct species, and is a viable approach for the analysis of historical museum specimens. Asiatic linsangs (genus Prionodon) exemplify this situation, being rare Southeast Asian carnivores for which little molecular data is available. Using ancestral capture we recover partial mitochondrial genome sequences for seven banded linsangs (P. linsang) from historical specimens, representing the first intraspecific genetic dataset for this species. We additionally assemble a high quality mitogenome for the banded linsang using shotgun sequencing for time-calibrated phylogenetic analysis. This reveals a deep divergence between the two Asiatic linsang species (P. linsang, P. pardicolor), with an estimated divergence of ~12 million years (Ma). Although our sample size precludes any robust interpretation of the population structure of the banded linsang, we recover two distinct matrilines with an estimated tMRCA of ~1 Ma. Our results can be used as a basis for further investigation of the Asiatic linsangs, and further demonstrate the utility of ancestral capture for studying divergent taxa without close relatives.

Rediscovering an old foe: Optimised molecular methods for DNA extraction and sequencing applications for fungarium specimens of powdery mildew (Erysiphales)

The purpose of this study was to identify a reliable DNA extraction protocol to use on 25-year-old powdery mildew specimens from the reference collection VPRI in order to produce high quality sequences suitable to address taxonomic phylogenetic questions. We tested 13 extraction protocols and two library preparation kits and found the combination of the E.Z.N.A.® Forensic DNA kit for DNA extraction and the NuGen Ovation® Ultralow System library preparation kit was the most suitable for this purpose.