Diversity and Conservation Genetics of the Mexican Beaded Lizard (Heloderma horridum)

Abstract

The Mexican beaded lizard (Heloderma horridum), one of only two venomous lizards in the world, is distributed throughout central and western Mexico. There are four currently recognized subspecies including: H. h. horridum, H. h. charlesbogerti, H. h. alvarezi, and H. h. exasperatum and all are now considered threatened. Due to the lack of verifiable locality data and ambiguities in diagnostic characters, it is often difficult to determine subspecific identity among captive individuals. Because uncertainties exist, genetic analyses of mitochondrial DNA (mtDNA) and nuclear microsatellites were used to define the patterns of genetic variation and population structure for the captive populations of H. horridum in order to make a genetically effective management program. Both categories of markers revealed a high level of genetic differentiation indicating significant population structure. All phylogenetic results converge toward a similar evolutionary hypothesis, with five mtDNA groups present among two major clades. Clustering obtained from microsatellites is not congruent with the mtDNA phylogenies, but is consistent with the unification of the subspecies H. h. charlesbogerti and H. h. alvarezi. The most conservative management plan would be to preserve six populations of H. horridum until the taxonomy can be revised.