Loss of genetic diversity among ocelots in the United States during the 20th century linked to human induced population reductions

Abstract

Ocelots (Leopardus pardalis) in the United States currently exhibit low levels of genetic diversity. One hypothesis for this observation is that habitat fragmentation, resulting from human induced changes in the landscape during the 20(th) century, created island populations with highly reduced gene flow and increased genetic drift and inbreeding. In an effort to investigate this, we used a portion of the mitochondrial control region and 11 autosomal microsatellite loci to examine historical levels of genetic diversity and infer temporal changes in ocelot populations between 1853 and 2005. Levels of genetic diversity were higher in historical ocelot populations than in extant populations from Texas. The earliest documented loss of mitochondrial haplotype diversity occurred at Laguna Atascosa National Wildlife Refuge. The second extant population inhabiting private lands in Willacy County retained higher levels of genetic diversity through the 1990s, but subsequently lost diversity over the next decade. A similar pattern was observed for autosomal microsatellite loci. This supports the argument that low levels of genetic diversity in Texas are related to human induced population reductions and fragmentation, both of which threaten the remaining ocelots in the United States. At this time, the best means of mitigating the continued erosion of genetic variation are translocation of individuals either from larger populations in Mexico to Texas, or between the Texas populations.

Figure 1. Map showing primary localities examined during this study, the dates samples were collected, and the number of samples.

Contemporary populations are identified with solid dots and the localities where museum specimens originated are underlined and marked with a star.

Figure 2. The minimum spanning network representing the most parsimonious mutation pathway between 6 ocelot haplotypes observed in Texas and northeastern Mexico.

Each hatch mark represents a single nucleotide point mutation. The populations in which haplotypes were observed are noted; CA = Cameron, WI = Willacy, LE = Los Ebanos, Mexico, TX = historical Texas samples. Haplotypes represented with shaded circles were observed only in museum samples originating in Texas prior to 1956.

Figure 3. Temporal changes in microsatellite diversity of 11 loci within ocelot populations in Texas and northeastern Mexico.

Willacy and Cameron are counties in Texas and Los Ebanos is a ranch in Mexico. Historical ocelot populations were sampled using museum specimens that originated in the Texas region.