Biology subjects

Rosel, P. E.

Publications and source records attributed to Rosel, P. E..

5 recordsLinked to original sources

bioRxiv2026

Long-term isolation and introgression shape the genomic distinctiveness of Rice's Whale

Species complex demographic history, including population size changes, isolation and gene flow, shapes patterns of genetic variation and deleterious load. In small and declining populations, understanding these processes is critical for predicting inbreeding depression and extinction risk. The Rices whale (Balaenoptera ricei) is a newly described baleen whale species resident to the heavily industrialized Gulf of Mexico, with a current abundance estimate of 51 (95 % CI: 20-130) individuals, making it one of the most endangered baleen whales globally. Using whole-genome sequences from 25 individuals, we reconstructed the evolutionary and demographic history of Rices whale and assessed its genomic health. Our analyses reinforce its distinctiveness from Brydes whales, and suggest that Rices whale has persisted as a small and isolated population in the Gulf of Mexico for tens of thousands of years. Despite its long-term small effective population size, genomes show modest impacts of inbreeding, including few long runs of homozygosity. We detected a distinct pulse of introgression [~]350 years ago from a Brydes whale-like lineage that resulted in windows of elevated heterozygosity in Rices whale, though it did not alter the burden of deleterious variation. Forward simulations indicate that a recent population collapse to [~]100 breeding individuals places the species at high risk of future inbreeding and genomic erosion unless population growth occurs. These findings highlight that while gene flow can increase genetic diversity, demographic recovery is essential to mitigate long-term genomic risks, underscoring the importance of management actions that promote sustained population growth.

genomics↗

bioRxiv2025

Mitochondrial structure despite nuclear panmixia: sex-specific dispersal dictates population structure in sperm whales

Marine mammals have high potential for dispersal, yet behavioral or environmental constraints can limit gene flow. This is true for the endangered sperm whale, Physeter macrocephalus, which has a global distribution and long-distance migrations. While previous studies revealed mitochondrial population structure with weak nuclear structure globally, genomic approaches examining this pattern have been limited. Understanding connectivity is critical for the management of this species due to population declines relative to pre-whaling, recent impacts from the Deepwater Horizon oil spill, and ongoing threats from anthropogenic sound. We investigated the connectivity between two regions, the U.S. Gulf of America (Mexico) and western North Atlantic Ocean, using reduced representation genomics and mitochondrial control region sequencing of 73 sperm whales. We found that relatedness decreased with geographic distance, likely due to the presence of familial structure. Nuclear markers showed no population structure (FST = 0.001-0.008), while mitochondrial structure was high (FST = 0.36-0.65), consistent with male-biased dispersal and female philopatry. Across all samples, genetic diversity (nuclear: 0.0014; mitochondrial: 0.0017) and effective population size (Ne=460) were low. Given this low diversity and evidence for the partitioning of genetic variation, we recommend managers treat these two regions as distinct in order to preserve existing variation and promote resilience of this species. These results show that despite the increased power of a genomic approach, it is essential to consider the biology of the species at hand and leverage both mitochondrial and nuclear markers to understand the genetic structure of threatened species.

evolutionary biology↗

bioRxiv2022

Ancient dolphin genomes reveal rapid repeated adaptation to coastal waters

Parallel evolution provides among the strongest evidence of the role of natural selection in shaping adaptation to the local environment. Yet, the chronology, mode and tempo of the process of parallel evolution remains broadly debated and discussed in the field of evolutionary biology. In this study, we harness the temporal resolution of paleogenomics to understand the tempo and independence of parallel coastal ecotype adaptation in common bottlenose dolphins (Tursiops truncatus). For this, we generated whole genome resequencing data from subfossil dolphins (8,610-5,626 years BP) originating from around the formation time of new coastal habitat and compared them with data from contemporary populations. Genomic data revealed a shift in genetic affinity, with the oldest ancient sample being closer to the pelagic populations, while the younger samples had intermediate ancestry that showed greater affinity with the local contemporary coastal populations. We found coastal-associated genotypes in the genome of our highest coverage ancient sample, SP1060, providing rare evidence of rapid adaptation from standing genetic variation. Lastly, using admixture graph analyses, we found a reticulate evolutionary history between pelagic and coastal populations. Ancestral gene flow from coastal populations was the probable source of standing genetic variation present in the pelagic populations that enabled rapid adaptation to newly emerged coastal habitat. The genetic response to past climatic warming provides an understanding of how bottlenose dolphins will respond to ongoing directional climate change and shifting coastlines.

evolutionary biology↗

bioRxiv2020

No leading-edge effect in North Atlantic harbor porpoises: Evolutionary and conservation implications

Understanding a species response to past environmental changes can help forecast how they will cope with ongoing climate changes. Harbor porpoises are widely distributed in the North Atlantic and were deeply impacted by the Pleistocene changes with the split of three sub-species. Despite major impacts of fisheries on natural populations, little is known about population connectivity and dispersal, how they reacted to the Pleistocene changes and how they will evolve in the future. Here, we used phylogenetics, population genetics, and predictive habitat modelling to investigate population structure and phylogeographic history of the North Atlantic porpoises. A total of 925 porpoises were characterized at 10 microsatellite loci and one-quarter of the mitogenome (mtDNA). A highly divergent mtDNA lineage was uncovered in one porpoise off Western Greenland, suggesting that a cryptic group may occur and could belong to a recently discovered mesopelagic ecotype off Greenland. Aside from it and the southern sub-species, spatial genetic variation showed that porpoises from both sides of the North Atlantic form a continuous system belonging to the same subspecies (Phocoena phocoena phoceona). Yet, we identified important departures from random mating and restricted intergenerational dispersal forming a highly significant isolation-by-distance (IBD) at both mtDNA and nuclear markers. A ten times stronger IBD at mtDNA compared to nuclear loci supported previous evidence of female philopatry. Together with the lack of spatial trends in genetic diversity, this IBD suggests that migration-drift equilibrium has been reached, erasing any genetic signal of a leading-edge effect that accompanied the predicted recolonization of the northern habitats freed from Pleistocene ice. These results illuminate the processes shaping porpoise population structure and provide a framework for designing conservation strategies and forecasting future population evolution.

evolutionary biology↗

bioRxiv2020

Selection on ancestral genetic variation fuels parallel ecotype formation in bottlenose dolphins

What are the mechanisms that allow species to extend their ranges and adapt to the novel environmental conditions they find in the newly available habitat? The study of parallel adaptation of pairs of populations to similar environments can provide great insights into this question. Here, we test for parallel evolution driven by niche specialization in a highly social marine mammal, the common bottlenose dolphin, Tursiops truncatus, and investigate the origins of the genetic variation driving local adaptation. Coastal ecotypes of common bottlenose dolphins have recurrently emerged in multiple regions of the world from pelagic ecotype populations, when novel habitat became available. Analyzing the whole genomes of 57 individuals using comparative population genomics approaches, we found that coastal ecotype evolution was relatively independent between the Atlantic and Pacific, but related between different regions within the Atlantic. We show that parallel adaptation to coastal habitat was facilitated by repeated selection on ancient alleles present as standing genetic variation in the pelagic populations. Genes under parallel adaptation to coastal habitats have roles in cognitive abilities and feeding. Therefore, parallel adaptation in long-lived social species may be driven by a combination of ecological opportunities, selection acting on ancient variants, and stable behavioural transmission of ecological specialisations. Tried and tested genetic variation that has been subject to repeated bouts of selection, may promote linked adaptive variants with minimal pleiotropic effects, thereby facilitating their persistence at low frequency in source populations and enabling parallel evolution.

evolutionary biology↗