GENETIC LEAKAGE AFTER ADAPTIVE AND NONADAPTIVE DIVERGENCE IN THE ENSATINA ESCHSCHOLTZII RING SPECIES |
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Authors: | Ricardo J. Pereira David B. Wake |
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Affiliation: | Museum of Vertebrate Zoology and Department of Integrative Biology, 3101 Valley Life Sciences Building, University of California, Berkeley, California 94720;E-mail:;CIBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, Universidade do Porto, Campus Agrário de Vairão, 4485-661 Vairão, Portugal;Departamento de Zoologia e Antropologia, Faculdade de Ciências da Universidade do Porto, 4099-002 Porto, Portugal |
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Abstract: | The salamander Ensatina eschscholtzii is an example of a ring species in which extant intermediate stages of terminal forms have a nearly continuous range, offering replicated interactions at several stages of divergence. We employ a greatly expanded allozyme database and individual-based analyses to separate the effects of divergence time and gene flow to evaluate how gradual divergence of populations around the ring contributes to the development of reproductive isolation. Despite the high degree of genetic ( D ≤ 0.39) and ecomorphological divergence observed in secondary contacts around the ring, reproductive isolation or rare hybridization is observed only at the terminus of the ring. Instead, in the secondary contacts sampled around the ring, hybrids are common and reproductively successful, enabling genetic leakage between parental genomes and the potential for genetic merger. Nevertheless, genetic admixture is geographically broad (<100 km) only in contacts between ecomorphologically similar populations (within subspecies). When divergence is accompanied by alternative patterns of adaptive divergence (between subspecies), zones of intergradation are narrower and affect populations only locally (>8 km). Diversification and consequent genetic interactions in Ensatina reveal a continuum between populations, ecological races, and species, where polytypic traits and high genetic differentiation are maintained without reproductive isolation. |
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Keywords: | Adaptive divergence gene flow hybridization polytypic species secondary contact speciation |
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