Noninvasive Sampling Reveals Short-Term Genetic Rescue in an Insular Red Fox Population

Abstract

Genetic factors in the decline of small populations are extremely difficult to study in nature. We leveraged a natural experiment to investigate evidence of inbreeding depression and genetic rescue in a remnant population of subalpine-specialized Sierra Nevada red foxes (Vulpes vulpes necator) using noninvasive genetic monitoring during 2010–2017. Only 7 individuals were detected in the first 2 years. These individuals assigned genetically to the historical population and exhibited genetic hallmarks of inbreeding and no evidence of reproduction. Two years into the study, we detected 2 first-generation immigrant males from a recently expanding population of red foxes in the Great Basin Desert. Through annual resampling of individuals (634 red fox DNA samples, 41 individuals) and molecular reconstruction of pedigrees, we documented 1–3 litters/year for 5 years, all descended directly or indirectly from matings involving immigrant foxes. The observed heterozygosity and allelic richness of the population nearly doubled in 2 years. Abundance increased, indicative of a rapidly expanding population. Throughout the study, adult survival was high. Restoration of gene flow apparently improved the demographic trajectory of this population in the short term. Whether these benefits continue in the longer term could depend on numerous factors, such as maintenance of any locally adapted alleles. This study highlights the value of noninvasive genetic monitoring to assess rapidly shifting conditions in small populations. Uncertainties about the longer-term trajectory of this population underscore the need to continue monitoring and to research potential for both negative and positive aspects of continued genetic infusion.

Vital rates of two small populations of brown bears in Canada and range‐wide relationship between population size and trend

“…The random fluctuations in birth and death events have very little effect on population growth in large populations; however, in small populations, simultaneous “bad luck” among few individuals can cause the population to decline to zero (Engen & Sæther, 1998). Fortunately, inbreeding and loss of genetic diversity are potentially reversible by restoring gene flow via augmentation or natural immigration (Åkesson et al., 2016; Poirier et al., 2019; Quinn et al., 2019; van de Kerk et al., 2019; Yumnam et al., 2014). An example is the genetic restoration of the Florida panthers ( Puma concolor coryi ) from population augmentation (Johnson et al., 2010) that increased survival of first generation admixed panthers in all age classes (van de Kerk et al., 2019).…”

Vital rates of two small populations of brown bears in Canada and range-wide relationship between population size and trend

“…The random fluctuations in birth and death events have very little effect on population growth in large populations; however, in small populations, simultaneous "bad luck" among few individuals can cause the population to decline to zero (Engen & Saether, 1998). Fortunately, inbreeding and loss of genetic diversity are potentially reversible by restoring gene flow via augmentation or natural immigration (Åkesson et al, 2016;Poirier et al, 2019;Quinn et al, 2019;van de Kerk et al, 2019;Yumnam et al, 2014). An example is the genetic restoration of the Florida panthers (Puma concolor coryi) from population augmentation (Johnson et al, 2010) that increased survival of first generation admixed panthers in all age classes (van de Kerk et al, 2019).…”

Multiscale landscape genetics of American marten at their southern range periphery

“…Population persistence in areas where species are patchily distributed is positively influenced by connectivity and exchange of individuals between patches (Beier and Noss 1998;Haddad et al 2003;Whiteley et al 2015). Connectivity reduces the probability of extinction from stochastic events, provides rescue effects following local extirpations, and increases genetic diversity within populations, which can reduce the likelihood of inbreeding depression (Hanski 1997;Quinn et al 2019). For species affected by habitat fragmentation, identifying and protecting corridors that facilitate dispersal and gene flow between disjunct populations is a conservation priority (Tischendorf and Fahrig 2000).…”