Genetic diversity and genetic structure of an endemic Mexican Dusky Rattlesnake (Crotalus triseriatus) in a highly modified agricultural landscape: implications for conservation

Abstract

It is necessary to determine genetic diversity of fragmented populations in highly modified landscapes to understand how populations respond to land-use change. This information will help guide future conservation and management strategies. We conducted a population genetic study on an endemic Mexican Dusky Rattlesnake (Crotalus triseriatus) in a highly modified landscape near the Toluca metropolitan area, in order to provide crucial information for the conservation of this species. There was medium levels of genetic diversity, with a few alleles and genotypes. We identified three genetically differentiated clusters, likely as a result of different habitat cover type. We also found evidence of an ancestral genetic bottleneck and medium values of effective population size. Inbreeding coefficients were low and there was a moderate gene flow. Our results can be used as a basis for future research and C. triseriatus conservation efforts, particularly considering that the Trans-Mexican Volcanic Belt is heavily impacted by destructive land-use practices.

Potential distribution and habitat connectivity of Crotalus triseriatus in Central Mexico

“…Although there are stable populations in the agriculture fields, large rattlesnakes have insufficient refuges and a variety of vegetation cover to allow the exploita-tion of thermal gradients (Blouin-Demers and Weatherhead 2001;Hoss et al 2010;Sunny et al 2015). This lack of vegetation limits the growth of rattlesnakes (Mociño-Deloya et al 2014).…”

“…It is also important that populations are not isolated in small patches of habitat (Frankham et al 2005). The populations that are isolated in patches of agriculture with low levels of landscape connectivity break the natural dynamics of the rattlesnake's metapopulations (Sunny et al 2015), increasing the loss of alleles and genetic variability through genetic drift and the increased possibility of inbreeding can translate to lower fitness of the individuals in the population, which can lead to increased population susceptibility to disease (Frankham et al 2005;Townsend et al 2009;Rulon et al 2011) and the proliferation of fungal pathogens (Jacobson et al 2000;Paré et al 2003;Rajeev et al 2009), including some that cause widespread mortality in free-ranging rattlesnakes populations (Cheatwood et al 2003), thereby increasing the extinction risk (Newman and Tallmon 2001).…”

“…This species is diurnally active and is mainly found in Pinus-Quercus forests, grasslands and agricultural areas (Canseco-Márquez and Mendoza-Quijano 2007;Fernández-Badillo et al 2011). It is classified as Least Concern on the IUCN Red List due to its wide distribution and presumed large population, but this assignment may be due to a lack of knowledge on the natural history of the species (Canseco-Márquez and Mendoza-Quijano 2007;Bryson et al 2014;Sunny et al 2015). The few ecological studies on this species are very basic, only reporting localities of presence, types of habitat where the species was found, size of the snakes and diet of the species.…”

Genetic structure and diversity in an isolated population of an endemic mole salamander (Ambystoma rivulare Taylor, 1940) of central Mexico

“…Two loci (At 52.10 and At 52.115) showed significant deviation from HWE because of a heterozygote deficiency. These deviations are common in threatened species with fragmented and isolated populations (Degne et al 2007;Spear and Storfer 2010;Parra-Olea et al 2012;Sunny et al 2014aSunny et al , 2015Percino-Daniel et al 2016). Analyses showed low levels of inbreeding and no presence of null alleles.…”

“…Additionally, this species is found in one of the most fragmented and disturbed areas of Mexico, where the environment has been heavily impacted by agriculture and urban settlements. In fact, some of the largest metropolitan areas in Mexico are in the distribution range of A. rivulare (CONAPO 2010;Bryson et al 2014;Sunny et al 2015).…”