Ancient hybridization and subsequent mitochondrial capture in ground squirrels (genus Ictidomys)
Occasional papers / Museum of Texas Tech University, number 331.
Thompson, Cody W.
Bradley, Robert D.
Stangl, Frederick B., Jr.,
Texas Tech University. Museum,
Texas Tech University. Natural Science Research Laboratory.
Lubbock, TX :Museum of Texas Tech University,
"Texas Tech University, Natural Science Research Laboratory."
"16 June 2015."
The sister species Ictidomys parvidens and I. tridecemlineatus exhibit hybridization in southeastern New Mexico and western Texas. Presumably, hybridization was due to secondary contact as a result of recent anthropogenic changes to the landscape. However, recent phylogenetic studies of Spermophilus, which previously included Ictidomys, indicated the possibility of widespread introgression due to paraphyly of haploytypes in the mitochondrial cytochrome-b (Cytb) gene. Samples of Ictidomys were obtained from 38 populations (N = 211) in the presumed zone of sympatry, as well as samples from 58 populations (N = 208) throughout the distribution of both sister species. DNA sequences from the Cytb gene (N = 419) and the Y-linked structural maintenance of chromosomes (SmcY) gene (N = 129) were used to determine the origin of paraphyly among Cytb haplotypes. In addition, divergence date estimates were calculated to determine the association between hybridization and climate oscillations. Analyses of Cytb sequences indicated a unique mitochondrial haplotype in both parental types and putative hybrids within the zone of sympatry but provided no evidence of contemporary mitochondrial introgression. However, analyses of the SmcY gene supported contemporary hybridization at six localities. These data, along with estimates of time since divergence, suggested an ancient hybridization event during the Pleistocene, followed by capture of the I. tridecemlineatus mitochrondrial haplotype by I. parvidens. Glacial oscillations during this period of time would have provided multiple opportunities for sympatry between these two species, increasing the potential for ancient hybridization. Whether contemporary hybridization is the result of a recent warming climate or an ancillary effect of anthropogenic habitat alterations is yet to be determined.
AS36 .T4955 no.331
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