Testing taxon tenacity of tortoises: evidence for a geographical selection gradient at a secondary contact zone

Ecology and Evolution
By: , and 

Links

Abstract

We examined a secondary contact zone between two species of desert tortoise, Gopherus agassizii and G. morafkai. The taxa were isolated from a common ancestor during the formation of the Colorado River (4-8 mya) and are a classic example of allopatric speciation. However, an anomalous population of G. agassizii comes into secondary contact with G. morafkai east of the Colorado River in the Black Mountains of Arizona and provides an opportunity to examine reinforcement of species' boundaries under natural conditions. We sampled 234 tortoises representing G. agassizii in California (n = 103), G. morafkai in Arizona (n = 78), and 53 individuals of undetermined assignment in the contact zone including and surrounding the Black Mountains. We genotyped individuals for 25 STR loci and determined maternal lineage using mtDNA sequence data. We performed multilocus genetic clustering analyses and used multiple statistical methods to detect levels of hybridization. We tested hypotheses about habitat use between G. agassizii and G. morafkai in the region where they co-occur using habitat suitability models. Gopherus agassizii and G. morafkai maintain independent taxonomic identities likely due to ecological niche partitioning, and the maintenance of the hybrid zone is best described by a geographical selection gradient model.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Testing taxon tenacity of tortoises: evidence for a geographical selection gradient at a secondary contact zone
Series title Ecology and Evolution
DOI 10.1002/ece3.1500
Volume 5
Issue 10
Year Published 2015
Language English
Publisher Blackwell Pub. Ltd.
Publisher location Oxford
Contributing office(s) Western Ecological Research Center
Description 20 p.
First page 2095
Last page 2114
Online Only (Y/N) N
Additional Online Files (Y/N) N