Sex differences in the genetic architecture of lifespan in a seed beetle: extreme inbreeding extends male lifespan

<p>Abstract</p> <p>Background</p> <p>Sex differences in lifespan are ubiquitous throughout the animal kingdom but the causes underlying this phenomenon remain poorly understood. Several explanations based on asymmetrical inheritance patterns (sex chromosomes or mitochondrial DNA) have been proposed, but these ideas have rarely been tested experimentally. Alternatively, sexual dimorphism in lifespan could result from sex-specific selection, caused by fundamental differences in how males and females optimize their fitness by allocating resources into current and future reproduction.</p> <p>Results</p> <p>Here we used sex-specific responses to inbreeding to study the genetic architecture of lifespan and mortality rates in <it>Callosobruchus maculatus</it>, a seed beetle that shows sexual dimorphism in lifespan. Two independent assays revealed opposing sex-specific responses to inbreeding. The combined data set showed that inbred males live longer than outbred males, while females show the opposite pattern. Both sexes suffered reduced fitness measured as lifetime reproductive success as a result of inbreeding.</p> <p>Conclusion</p> <p>No model based on asymmetrical inheritance can explain increased male lifespan in response to inbreeding. Our results are however compatible with models based on sex-specific selection on reproductive strategies. We therefore suggest that sex-specific differences in lifespan in this species primarily result from sexually divergent selection.</p

Population genomics of the muskox' resilience in the near absence of genetic variation

DATA AVAILABILITY STATEMENT : Raw sequence reads are deposited in the European Nucleotide Archive under study accession ID: PRJEB64293. Scripts used in the analyses are available at https://github.com/patriciapecnerova/muskox_popgenomicsGenomic studies of species threatened by extinction are providing crucial information about evolutionary mechanisms and genetic consequences of population declines and bottlenecks. However, to understand how species avoid the extinction vortex, insights can be drawn by studying species that thrive despite past declines. Here, we studied the population genomics of the muskox (Ovibos moschatus), an Ice Age relict that was at the brink of extinction for thousands of years at the end of the Pleistocene yet appears to be thriving today. We analysed 108 whole genomes, including present-day individuals representing the current native range of both muskox subspecies, the white-faced and the barren-ground muskox (O. moschatus wardi and O. moschatus moschatus) and a ~21,000-year-old ancient individual from Siberia. We found that the muskox' demographic history was profoundly shaped by past climate changes and post-glacial re-colonizations. In particular, the white-faced muskox has the lowest genome-wide heterozygosity recorded in an ungulate. Yet, there is no evidence of inbreeding depression in native muskox populations. We hypothesize that this can be explained by the effect of long-term gradual population declines that allowed for purging of strongly deleterious mutations. This study provides insights into how species with a history of population bottlenecks, small population sizes and low genetic diversity survive against all odds.Carlsbergfondet and Danmarks Frie Forskningsfond.http://www.wileyonlinelibrary.com/journal/mec2024-11-16hj2024Mammal Research InstituteZoology and EntomologyNon