Conwell, H. C. | Search bioRxiv

bioRxiv2025

Paleogenomic insight into the collapse, recovery, and management of American bison

American bison were pushed to the brink of extinction by the 20th century. This bottleneck and the fragmented nature of remnant populations pose challenges to their resilience, as does human-facilitated admixture between bison subspecies and with cattle. To contextualize current diversity, we sequenced 115 ancient and 45 modern bison genomes from across North America dating back within the last [~]20,000 years. Past bison populations were highly connected, in contrast to structured modern herds. Modern wood bison carry plains bison ancestry from 1920s translocations, while many bison lack cattle ancestry that has previously been believed to be ubiquitous. Our findings reveal the legacy of human impacts on bison in the context of modern conservation and highlight the applicability of ancient DNA for guiding wildlife restoration.

evolutionary biology↗

bioRxiv2025

Ancient DNA from shells reveals delayed genomic erosion and rapid immune adaptation in the critically endangered black abalone

Predicting the genetic consequences of population decline is a major problem in conservation genomics. Time lags following demographic bottlenecks can delay genomic erosion and make it difficult to determine a populations current and future risk, especially when pre-bottleneck genomic baselines are unavailable. Black abalone (Haliotis cracherodii) suffered a severe disease bottleneck in the 1980s, resulting in an estimated 99% population decline. However, recent work found surprisingly high genetic diversity and little population structure in current black abalone populations, raising questions of whether genomic erosion has been delayed. To investigate this, we applied ancient DNA methods to pre-bottleneck abalone shells, generating 59 whole genomes including one 34-fold coverage genome from a 1,500-year-old specimen. These data show that heterozygosity, runs of homozygosity, genetic load and population structure remained stable up to and following the bottleneck. Simulations reveal that this stability is consistent with even severe bottleneck scenarios because too few generations have lapsed since the decline. Projections suggest that future genomic erosion may be avoided even in limited recovery scenarios. Following the bottleneck we observe widespread balancing selection at genes with immune function, along with parallel increases of two inversions on separate chromosomes that are in linkage disequilibrium, where the disease bottleneck was most severe. Altogether, these findings explain why genomic change has thus far been limited, outline recovery scenarios that minimize genomic erosion, and identify loci likely that may harbor adaptive variation key to the success of future black abalone populations.

evolutionary biology↗