An analysis of bone fragments in a high latitude cave using aDNA and paleozoology to assess biodiversity and phylogeny

Sammanfattning

The Pleistocene was a period of glacial-interglacial cycles that shaped the distribution andevolutionary history of many taxa. Biodiversity assessments and aDNA analysis from bonefragments are useful methods to gain information on a species’ past distribution and populationdynamics. However, fossil records predating the Last Glacial Maximum (LGM) in high latitudes arescarce due to glacial erosion and the flushing of sediments. A bone assemblage found in a highlatitude cave in northern Norway presents a unique opportunity to research faunal biodiversityand biogeography in this region. Bulk-bone metabarcoding (BBM) and traditional paleozoologymethods were employed to recover taxa and assess biodiversity. BBM yielded the highest numberof taxa, though paleozoological methods captured taxa not represented with BBM. We recoveredthe highest number of taxa when both methods are combined. The faunal taxa recovered areindicative of colder and drier conditions, providing an example of faunal complexes as ecologicalindicators from which we can infer past environmental conditions. Paleozoological quantitativemethods such as the NISP and MNI were employed to inspect taxa abundance and sampleselection for shotgun sequencing. In general, the class Mammalia was the most abundant, and theorder Rodentia the most represented. Using MNI calculations, we selected the M2 molar to identify5 different Dicrostonyx torquatus individuals, and 5 more potential specimens were selected basedon different layers and quadrants to maximize the probability of obtaining different individuals.The DNA libraries were unsuccessful, and coverage was low (<0.5X). However, two D. torquatussamples excavated in 2021 had sufficient coverage (2X and 9X) for further analyses. With additionalD. torquatus data supplied by Lord et al. (2022), I reconstructed a phylogenetic tree to inspectdivergence time and biogeography. By combining dating methods such as OSL, radiocarbon datingand phylogenetic dating, we can conclude that our D. torquatus samples diverged more than 90.8ka BP, but are younger than 100 ka BP. As Dicrostonyx torquatus had not been documented inNorway before, these findings are noteworthy and further increase our knowledge on this species’past distribution and evolutionary history.