Landscape genetics of the nonnative red fox of California

Abstract

Invasive mammalian carnivores contribute disproportionately to declines in global biodiversity. In California, nonnative red foxes (Vulpes vulpes) have significantly impacted endangered ground‐nesting birds and native canids. These foxes derive primarily from captive‐reared animals associated with the fur‐farming industry. Over the past five decades, the cumulative area occupied by nonnative red fox increased to cover much of central and southern California. We used a landscape‐genetic approach involving mitochondrial DNA (mtDNA) sequences and 13 microsatellites of 402 nonnative red foxes removed in predator control programs to investigate source populations, contemporary connectivity, and metapopulation dynamics. Both markers indicated high population structuring consistent with origins from multiple introductions and low subsequent gene flow. Landscape‐genetic modeling indicated that population connectivity was especially low among coastal sampling sites surrounded by mountainous wildlands but somewhat higher through topographically flat, urban and agricultural landscapes. The genetic composition of populations tended to be stable for multiple generations, indicating a degree of demographic resilience to predator removal programs. However, in two sites where intensive predator control reduced fox abundance, we observed increases in immigration, suggesting potential for recolonization to counter eradication attempts. These findings, along with continued genetic monitoring, can help guide localized management of foxes by identifying points of introductions and routes of spread and evaluating the relative importance of reproduction and immigration in maintaining populations. More generally, the study illustrates the utility of a landscape‐genetic approach for understanding invasion dynamics and metapopulation structure of one of the world's most destructive invasive mammals, the red fox.

Admixture analyses and phylogeographic relationships reveal complete genetic distinctiveness of Polish farm and wild red foxes (Vulpes vulpes) and the North American origin of farm‐bred individuals

“…Table shows six concatenated haplotypes found only in farm foxes along with 19 concatenated haplotypes found only in wild foxes. All six concatenated haplotypes or cytochrome b and D‐loop fragments separately (A, E, F, 9, 17, 67, 86) observed in farm foxes were previously reported to be of North American origin (Aubry et al., ; Lounsberry et al., ; Perrine et al., ; Sacks, Brazeal, & Lewis, ). The most common concatenated haplotype found in the farm foxes (E‐86, n = 19) was previously found in farm foxes (Statham et al., , ) and in a population from the eastern U.S. (Kasprowicz et al., ).…”

“…(), the haplotypes classified as basal to the Nearctic clade (red foxes of North American origin) and those classified as basal to the Holarctic clade (including red foxes of European origin) were only observed in the farm‐ and wild red foxes, respectively, that we studied. A few other phylogenetic and phylogeographic studies of local red fox populations (Akins, Aubry, & Sacks, ; Merson et al., ; Sacks et al., ; Statham et al., , ), may also provide indirect support for the hypothesis that the source of the genetic variation in red foxes kept on Polish fur farms lies in North America. In particular, studies that dealt with genetic introgression from farm foxes into wild ones provided valuable information (Horecka et al., ; Kasprowicz et al., ; Lounsberry et al., ).…”

Genetic patterns across an invasion's history: a test of change versus stasis for the Eurasian round goby in North America

“…In another case of genetic stasis, invasive populations of red fox Vulpes vulpes in California showed no significant changes over several generations, except in those that were culled (Sacks et al . ). Also similar to the round goby, zebra and quagga mussel populations exhibited pronounced divergences across their exotic North American ranges, with some populations changing significantly over their temporal courses yet remaining distinctive (Brown & Stepien ; Stepien et al .…”

Gene flow and genetic drift in urban environments

“…For example, three lizard species sampled from the same urban locales experienced roads as barriers to gene flow, with the association between genetic resistance (caused by roads) and genetic distance varying from r 2 = 0.09 to 0.16 (Delaney, Riley, & Fisher, ). While those associations were significant, they were weak compared with genetic differentiation among red fox ( Vulpes vulpes Linnaeus) populations, which experienced the urban landscape as a barrier to gene flow, with a significant association between genetic distance and resistance (caused by land‐use) with an r 2 = 0.42 (Sacks, Brazeal, & Lewis, ). Six other studies found that urban land‐use facilitated gene flow between populations, whereas only two studies found no statistical evidence for urban or natural barriers to gene flow (Gortat et al, , ).…”