Consequences for conservation: population density and genetic effects on reproduction of an endangered lagomorph

Abstract

Understanding reproduction and mating systems is important for managers tasked with conserving vulnerable species. Genetic tools allow biologists to investigate reproduction and mating systems with high resolution and are particularly useful for species that are otherwise difficult to study in their natural environments. We conducted parentage analyses using 19 nuclear DNA microsatellite loci to assess the influence of population density, genetic diversity, and ancestry on reproduction, and to examine the mating system of pygmy rabbits (Brachylagus idahoensis) bred in large naturalized enclosures for the reintroduction and recovery of the endangered distinct population in central Washington, USA. Reproductive output for females and males decreased as population density and individual homozygosity increased. We identified an interaction indicating that male reproductive output decreased as genetic diversity declined at high population densities, but there was no effect at low densities. Males with high amounts (> 50%) of Washington ancestry had higher reproductive output than the other ancestry groups, while reproductive output was decreased for males with high northern Utah/Wyoming ancestry and females with high Oregon/Nevada ancestry. Females and males bred with an average of 3.8 and 3.6 mates per year, respectively, and we found no evidence of positive or negative assortative mating with regards to ancestry. Multiple paternity was confirmed in 81% of litters, and we report the first documented cases of juvenile breeding by pygmy rabbits. This study demonstrates how variation in population density, genetic diversity, and ancestry impact fitness for an endangered species being bred for conservation. Our results advance understanding of basic life history characteristics for a cryptic species that is difficult to study in the wild and provide lessons for managing populations of vulnerable species in captive and free-ranging populations.

Is promiscuity the key? Multiple paternity in the garden dormouse (Eliomys quercinus)

“…As connecting suitable habitats facilitates dispersal and promotes access to potential mating partners, which may be particularly important for populations colonizing new habitats (Power and Holman 2014;Lewis et al 2020), connecting habitats represents a key conservation measure for the garden dormouse. The results of our study should also be considered in conservation breeding programs, and in translocation and reintroduction programs of garden dormice, in order to maintain the genetic variability of these populations (Gregory et al 2012;DeMay et al 2016).…”

“…The knowledge of the mating system of a threatened species provides important information for the implementation of conservation measures (Sigg et al 2005;DeMay et al 2016;Nardelli et al 2020;Madsen et al 2023). In the studied garden dormouse population, we identified the genetic mother in 64% of the litters and in 27% of these mother juvenile pairs we were able to assign the potential fathers.…”

Monitoring a New England Cottontail Reintroduction with Noninvasive Genetic Sampling

“…Further research on cottontail densities in relation to habitat and patch characteristics is needed to establish realistic target densities for reintroductions. Further, it is unknown if success may have been greater with a single release or fewer larger releases, rather than the multiple releases – based on availability from the breeding program – of 42 individuals across 5 years; for example, it is unknown whether it would have minimized competition for occupied home ranges, stress to resident rabbits, or predator responses that may occur over time with the multiple release strategy (Hamilton et al 2010; DeMay et al 2016, 2017). Given the small amount of available habitat in the landscape for New England cottontails, continued augmentation of reintroduced populations will likely be necessary, until sufficient habitat is established in the context of a larger landscape.…”

Release of hatchery adult steelhead for angler opportunity increases potential for interactions with endemic steelhead

“…4). For example, if releases are intended to buffer the recipient population from extinction, then integration between the non-local and endemic animals is expected and desired (Griffith et al 1989, DeMay et al 2016, and therefore, harvest of the non-local animals would be detrimental to management objectives. However, if releases are for harvest enhancement, either segregation-or integrationbased management strategies could be warranted.…”