Biology subjects

Michael Hofreiter

Publications and source records attributed to Michael Hofreiter.

4 recordsLinked to original sources

bioRxiv2016

Massive influence of DNA isolation and library preparation approaches on palaeogenomic sequencing data

The ability to access genomic information from ancient samples has provided many important biological insights. Generating such palaeogenomic data requires specialised methodologies, and a variety of procedures for all stages of sample preparation have been proposed. However, the specific effects and biases introduced by alternative laboratory procedures is insufficiently understood. Here, we investigate the effects of three DNA isolation and two library preparation protocols on palaeogenomic data obtained from four Pleistocene subfossil bones. We find that alternative methodologies can significantly and substantially affect total DNA yield, the mean length and length distribution of recovered fragments, nucleotide composition, and the total amount of usable data generated. Furthermore, we also detect significant interaction effects between these stages of sample preparation on many of these factors. Effects and biases introduced in the laboratory can be sufficient to confound estimates of DNA degradation, sample authenticity and genomic GC content, and likely also estimates of genetic diversity and population structure. Future palaeogenomic studies need to carefully consider the effects of laboratory procedures during both experimental design and data analysis, particularly when studies involve multiple datasets generated using a mixture of methodologies.

Genomics↗

bioRxiv2016

Complex admixture preceded and followed the extinction of wisent in the wild

Retracing complex population processes that precede extreme bottlenecks may be impossible using data from living individuals. The wisent (Bison bonasus), Europes largest terrestrial mammal, exemplifies such a population history, having gone extinct in the wild but subsequently restored by captive breeding efforts. Using low coverage genomic data from modern and historical individuals, we investigate population processes occurring before and after this extinction. Analysis of aligned genomes supports the division of wisent into two previously recognised subspecies, but almost half of the genomic alignment contradicts this population history as a result of incomplete lineage sorting and admixture. Admixture between subspecies populations occurred prior to extinction and subsequently during the captive breeding program. Admixture with the Bos cattle lineage is also widespread but results from ancient events rather than recent hybridisation with domestics. Our study demonstrates the huge potential of historical genomes for both studying evolutionary histories and for guiding conservation strategies.

Genomics↗

bioRxiv2016

The genetics of an early Neolithic pastoralist from the Zagros, Iran

The agricultural transition profoundly changed human societies. We sequenced and analysed the first genome (1.39x) of an early Neolithic woman from Ganj Dareh, in the Zagros Mountains of Iran, a site with early evidence for an economy based on goat herding,ca. 10,000 BP. We show that Western Iran was inhabited by a population genetically most similar to hunter-gatherers from the Caucasus, but distinct from the Neolithic Anatolian people who later brought food production into Europe. The inhabitants of Ganj Dareh made little direct genetic contribution to modern European populations, suggesting they were somewhat isolated from other populations in the region. Runs of homozygosity are of a similar length to those from Neolithic Anatolians, and shorter than those of Caucasus and Western Hunter-Gatherers, suggesting that the inhabitants of Ganj Dareh did not undergo the large population bottleneck suffered by their northern neighbours. While some degree of cultural diffusion between Anatolia, Western Iran and other neighbouring regions is possible, the genetic dissimilarity of early Anatolian farmers and the inhabitants of Ganj Dareh supports a model in which Neolithic societies in these areas were distinct.

Genetics↗

bioRxiv2016

Ancient DNA reveals differences in behaviour and sociality between brown bears and extinct cave bears.

Ancient DNA studies have revolutionised the study of extinct species and populations, providing insights on phylogeny, phylogeography, admixture and demographic history. However, inferences on behaviour and sociality have been far less frequent. Here, we investigate the complete mitochondrial genomes of extinct Late Pleistocene cave bears and middle Holocene brown bears that each inhabited multiple geographically proximate caves in northern Spain. In cave bears, we find that, although most caves were occupied simultaneously, each cave almost exclusively contains a unique lineage of closely related haplotypes. This remarkable pattern suggests extreme fidelity to their birth site in cave bears, best described as homing behaviour, and that cave bears formed stable maternal social groups at least for hibernation. In contrast, brown bears do not show any strong association of mitochondrial lineage and cave, suggesting that these two closely related species differed in aspects of their behaviour and sociality. This difference is likely to have contributed to cave bear extinction, which occurred at a time in which competition for caves between bears and humans was likely intense and the ability to rapidly colonise new hibernation sites would have been crucial for the survival of a species so dependent on caves for hibernation as cave bears. Our study demonstrates the potential of ancient DNA to uncover patterns of behaviour and sociality in ancient species and populations, even those that went extinct many tens of thousands of years ago.

Animal Behavior and Cognition↗