Genetic Structure of the North American Porcupine (Erethizon dorsatum) Across Western Texas

The North American porcupine (Erethizon dorsatum) is a highly mobile, generalist species with an extensive geographical distribution in North America. The porcupine was first documented in southwestern Texas in the early 20th century, but today occurs in most of the western two-thirds of the state. This species is relatively unstudied within the Great Plains ecoregion of North America, with no genetic studies having been conducted for this species in Texas. The objectives of this study were to describe population genetic metrics of porcupines across 3 ecoregions in western Texas by examining variation in 17 polymorphic microsatellites, and to confirm the applicability of the zinc finger protein sequencing method to identify sex in a population of North American porcupines.
Tissue samples from 106 porcupines were collected from the High Plains, Rolling Plains, and Edwards Plateau ecoregions of western Texas. Sex was accurately identified for 92 porcupine tissue samples by directly sequencing a short portion (195 base pairs) of the zinc finger protein gene. Sixteen base pair substitutions between Zfx and Zfy chromosomes denoted the sex of individuals; heterozygous sequence for males (Zfx and Zfy), homozygous sequence for females (Zfx only). All anatomically confirmed samples were correctly assigned to the known sex based on the generated sequence data: 51 male and 41 female. Porcupines were genotyped for 17 polymorphic loci to estimate genetic variation and population structure. The variation in multilocus microsatellite genotypes for 100 porcupines support minimal genetic structure throughout the study area. Overall expected heterozygosity (HE = 0.8327) exceeded observed heterozygosity (HO = 0.7748). I observed moderate genetic variation with little population structure (K = 1). An overall FST = 0.0022 detected little to no divergence. STRUCTURE and Detrended Correspondence Analysis illustrated a primary genetic cluster with minimal grouping by ecoregion. An overall GST value of 0.0019 was obtained for porcupines across all ecoregions, suggesting that panmixia may be widespread throughout western Texas due to low variation of allele frequencies. This research reveals that porcupines throughout western Texas are indeed vagile. The lack of population structure found in western Texas is likely the result of the relatively short life history and recent arrival of this highly mobile species within the state of Texas. The moderate genetic diversity reflects porcupine’s wide use of habitat throughout the western portion of the state. This knowledge is beneficial in the management of this species, considered a pest by some, and to the overall understanding of the porcupine.