Genetic diversity and mate selection in a reintroduced population of gray wolves

Abstract

The genetic composition of an individual can markedly affect its survival, reproduction, and ultimately fitness. As some wildlife populations become smaller, conserving genetic diversity will be a conservation challenge. Many imperiled species are already supported through population augmentation efforts and we often do not know if or how genetic diversity is maintained in translocated species. As a case study for understanding the maintenance of genetic diversity in augmented populations, I wanted to know if genetic diversity (i.e., observed heterozygosity) remained high in a population of gray wolves in the Rocky Mountains of the U.S. > 20 years after reintroduction. Additionally, I wanted to know if a potential mechanism for such diversity was individuals with below average genetic diversity choosing mates with above average diversity. I also asked whether there was a preference for mating with unrelated individuals. Finally, I hypothesized that mated pairs with above average heterozygosity would have increased survival of young. Ultimately, I found that females with below average heterozygosity did not choose mates with above average heterozygosity and wolves chose mates randomly with respect to genetic relatedness. Pup survival was not higher for mated pairs with above average heterozygosity in my models. The dominant variables predicting pup survival were harvest rate during their first year of life and years pairs were mated. Ultimately, genetic diversity was relatively unchanged > 20 years after reintroduction. The mechanism for maintaining such diversity does not appear related to individuals preferentially choosing more genetically diverse mates. Inbreeding avoidance, however, appears to be at least one mechanism maintaining genetic diversity in this population.

Relatedness-based mate choice and female philopatry: inbreeding trends of wolf packs in a human-dominated landscape

“…In contrast to our initial prediction, kin encounter rates among Alto Minho wolves were relatively low, and inbreeding does not seem to be recurrent, as it was mostly observed during the first sampling years. Additionally, the general assumption that wolves mate randomly with respect to relatedness outside natal packs (Ausband 2022a ; Geffen et al 2011 ) was not confirmed in Alto Minho, where we found that relatedness among breeding pairs was significantly lower than expected under random mating conditions.…”

“…We observed inbreeding in 26% of the detected breeding pairs. This indicates that inbreeding in Alto Minho is more frequent than that described for populations in less disturbed landscapes, with or without harvesting, like the Italian Apennine (3%; Caniglia et al 2014 ), the Idaho Rocky Mountains (6%; Ausband 2022a ), Yellowstone (7%; vonHoldt et al 2008 ), or southern Finland (15%; Granroth-Wilding et al 2017 ). However, the detected inbreeding rate is similar to that described for the central Idaho population before harvest (25%; Stenglein et al 2011 ).…”

“…The latter strategy related to dispersal relies on the premise that different distances or rates of dispersal between sexes promote the geographical separation of females and males born in the same area (Pusey and Packer 1987 ). Notably, in canids, inbreeding within the natal group is apparently avoided (Geffen et al 2011 ), whereas mating outside natal groups seems to occur randomly with respect to genetic, suggesting that, outside natal groups, geographical proximity of close kin is a preponderant driver of inbreeding (Ausband 2022a ; Geffen et al 2011 ). Therefore, inbreeding is of substantial conservation concern in small, isolated populations with high rates of sedentism or a predominance of short-distance dispersal, which leads to high local densities of relatives (e.g., Cockerill et al 2022 ; Viluma et al 2022 ).…”

Demographic history shapes North American gray wolf genomic diversity and informs species' conservation

“…Peterson et al (1998) used demographic models of N e for Isle Royale and estimated an N e /N ratio of 16%. Further, many wild canid species will avoid mating with relatives (Ausband, 2022;Geffen et al, 2011;Sparkman et al, 2012;vonHoldt et al, 2008), and this inbreeding avoidance mechanism will increase N e . Our estimates are comparable to those for the cooperative breeding African wild dog (Lycaon pictus) where effective population sizes are 8.7-11.3% of the census size (Marsden et al, 2012).…”