Reduced genetic diversity and isolation of remnant ocelot populations occupying a severely fragmented landscape in southern Texas

Abstract

The ocelot Leopardus pardalis has become a conservation priority in the US as a result of severe population decline and loss of habitat during the 20th century. Only two small populations remain in this country. Their short-term viability is threatened by the disappearance of dense thornshrub communities, human-caused mortality and demographic stochasticity. The influence these factors have on ocelot persistence must be considered to develop effective conservation initiatives. We therefore examined neutral genetic diversity and connectivity among ocelots in the US and northeastern Mexico using 25 autosomal microsatellites and a 395-bp segment of the mitochondrial control region. Genetic variation was lowest in the population occurring on Laguna Atascosa National Wildlife Refuge, Texas (autosomal microsatellite H E =0.399 and mtDNA-haplotype diversity= 0) and highest in northeastern Mexico (0.637 and 0.73, respectively), while intermediate on private lands in Willacy County, Texas (0.553 and 0.252, respectively). Significant genetic differentiation between the two Texas populations was observed, despite their close proximity ($30 km). Both populations were also significantly divergent from northeastern Mexico. The absence of any detectable gene flow implies that the human modified landscape of the Lower Rio Grande Valley in southern Texas acts as a strong barrier to ocelot movement, disrupting metapopulation dynamics and contributing to loss of diversity. As a consequence, continued genetic erosion among the Texas populations is expected. The lack of movement through the fragmented landscape also suggests it is unlikely ocelots will recolonize unoccupied habitat patches along the Lower Rio Grande and the delta interior where agriculture and urban land uses predominate. The continued rapid development will exacerbate this problem. These factors threaten the persistence of the Texas populations and limit their recovery. Translocations are necessary to link ocelot populations in the US.

Lack of Population Genetic Structuring in Ocelots (Leopardus pardalis) in a Fragmented Landscape

“…We did not detect clear evidence of population subdivision in our sample, despite previously reported genetic differentiation and lack of migrants in ocelot populations separated by a mere 30 km in North America [17]. Bayesian analyses revealed no meaningful subdivision between our sampled sites, while the FST analyses indicated a low (FST = 0.027-0.038) but statistically significant results.…”

“…A higher diversity was observed for Amazonian ocelots [41], whereas lower values were observed in the remaining ocelot populations from the United States [16][17][18]. It is noteworthy that the microsatellite loci employed in these previous studies were not identical to ours, and therefore this comparison should not be interpreted strictly.…”

“…Currently, skin trade is prohibited and the main threats to this species are habitat loss and fragmentation [15]. In this context, recent analyses have indicated that the ocelots in the United States and Mexico suffer with habitat loss and population isolation, with detectable genetic depletion as a consequence [16][17][18].…”

“…On the other hand, the species was found to be incapable of crossing the human-dominated matrix between protected areas in Texas, and ~30 km were enough to hinder their dispersal and to induce significant genetic differentiation [17].…”

Selecting representative microsatellite loci for genetic monitoring and analyzing genetic structure of an outbred population of orange tabby cats in China

“…Microsatellites, also referred to as short tandem repeats (STR), are useful for assessing wild and domestic cat admixtures (Driscoll et al, 2011), identifying domestic and known hybrid cats (Lecis et al, 2006), and studying the genetic differentiation between the African wild cat (Felis lybica) and the domestic cat (F. catus) in southern Africa (Wiseman et al, 2000). Microsatellite analysis has been widely used in genetic structure studies of ocelot (Janecka et al, 2011), gerbils (Du et al, 2010), and many other animals (Kim et al, 2011;Ruggeri et al, 2012). Although there have been numerous reports regarding the use of microsatellites for cat, information about microsatellite markers for monitoring the genetic structure of laboratory cat populations is limited.…”