Abstract
Urban development has major impacts on connectivity among wildlife populations and is thus likely an important factor shaping pathogen transmission in wildlife. However, most investigations of wildlife diseases in urban areas focus on prevalence and infection risk rather than potential effects of urbanization on transmission itself. Feline immunodeficiency virus (FIV) is a directly transmitted retrovirus that infects many felid species and can be used as a model for studying pathogen transmission at landscape scales. We investigated phylogenetic relationships among FIV isolates sampled from five bobcat (Lynx rufus) populations in coastal southern California that appear isolated due to major highways and dense urban development. Divergence dates among FIV phylogenetic lineages in several cases reflected historical urban growth and construction of major highways. We found strong FIV phylogeographic structure among three host populations north‐west of Los Angeles, largely coincident with host genetic structure. In contrast, relatively little FIV phylogeographic structure existed among two genetically distinct host populations south‐east of Los Angeles. Rates of FIV transfer among host populations did not vary significantly, with the lack of phylogenetic structure south‐east of Los Angeles unlikely to reflect frequent contemporary transmission among populations. Our results indicate that major barriers to host gene flow can also act as barriers to pathogen spread, suggesting potentially reduced susceptibility of fragmented populations to novel directly transmitted pathogens. Infrequent exchange of FIV among host populations suggests that populations would best be managed as distinct units in the event of a severe disease outbreak. Phylogeographic inference of pathogen transmission is useful for estimating the ability of geographic barriers to constrain disease spread and can provide insights into contemporary and historical drivers of host population connectivity.
Highlights
Urban development is a dominant factor influencing wildlife abundance, changes the nature and frequency of both intra- and interspecific interactions, and leads to reduced connectivity among populations (Bierwagen, 2007; Crooks, Riley, Gehrt, Gosselink, & Deelen, 2010; Shochat et al, 2010)
We identified a total of 73 Feline immunodeficiency virus (FIV)-positive bobcats, using both blood and tissue samples, which we included in FIVLru genetic analysis below
We found distinct differences in FIVLru phylogenetic structure among populations in different regions in coastal southern California
Summary
Urban development is a dominant factor influencing wildlife abundance, changes the nature and frequency of both intra- and interspecific interactions, and leads to reduced connectivity among populations (Bierwagen, 2007; Crooks, Riley, Gehrt, Gosselink, & Deelen, 2010; Shochat et al, 2010). | 1808 distinct bobcat populations exist north-west and south-east of Los Angeles, California, with major freeways and large urban areas forming the primary barriers to gene flow (Lee et al, 2012; Poessel et al, 2014; Riley et al, 2006; Ruell et al, 2012; Serieys, Lea, Pollinger, Riley, & Wayne, 2015) Increasing urbanization in this region is generally further reducing connectivity within populations (Kozakiewicz et al, 2019). Despite evidence for FIVLru transmission across Interstate 5, FIVLru genetic diversity and evolutionary rates differed among populations (Fountain-Jones, Craft, et al, 2017a), which may point to varying patterns of selection These prior genetic studies on bobcats and their pathogens have focused on a small region of southern California, on a single barrier and on a relatively small number of samples. This study provides novel insights into host and pathogen connectivity with respect to major urban barriers
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