Coalescent analyses show isolation without migration in two closely related tropical orioles: the case of Icterus graduacauda and Icterus chrysater

• Published in: Ecology and evolution Vol. 3; no. 13; pp. 4377 - 4387
• Main Authors: Cortés‐Rodríguez, Nandadevi, Jacobsen, Frode, Hernandez‐Baños, Blanca E., Navarro‐Siguenza, Adolfo G., Peters, Jeffrey L., Omland, Kevin E.
• Format: Journal Article
• Language: English
• Published: England John Wiley & Sons, Inc 01.11.2013; Blackwell Publishing Ltd
• Subjects: Biogeography; Birds; Climate change; coalescent; Deoxyribonucleic acid; Dispersal; Divergence; DNA; Ecological effects; Gene flow; Genes; Highlands; Icterus; Icterus graduacauda; Introns; Isolation with Migration; Isthmus of Tehuantepec; Lowlands; Migration; Mitochondria; Mitochondrial DNA; multilocus; Museums; Natural history; Occupancy; Original Research; Pleistocene; Population; Variation; Western Hemisphere; South America; Mexico; Panama; ASW, South America; Mexico, Oaxaca, Isthmus of Tehuantepec; Isolation with Migration; multilocus; Icterus; Isthmus of Tehuantepec; coalescent
• ISSN: 2045-7758; 2045-7758
• DOI: 10.1002/ece3.768

The Isthmus of Tehuantepec has played an important role in shaping the avian diversity of Mexico, as well as the rest of the Western Hemisphere. It has been both a barrier and a land connector between North and South America for many groups of birds. Furthermore, climatic change over the Pleistocene has resulted in ecological fluctuations that led to periods of connection and isolation of the highlands in this area. Here we studied the divergence of two species of orioles whose distribution in the highlands is separated by the lowlands of the Isthmus of Tehuantepec: Icterus graduacauda (west of the Isthmus) and Icterus chrysater (east of the Isthmus). We sequenced multiple loci (one mitochondrial gene and six nuclear introns) and performed coalescent analyses (Isolation with Migration) to test whether their divergence resulted from prior occupancy of the ancestral area followed by a vicariant event or recent dispersal from one side or the other of this Isthmus. Results strongly indicate a vicariant event roughly 300,000 years ago in the Pleistocene followed by little or no gene flow. Both mitochondrial and nuclear genes show that the Isthmus of Tehuantepec is a strong barrier to gene flow. Thus, these two species appear to not exchange genes despite their recent divergence and the close geographic proximity of their ranges. The use pf coalescent analyses to study the divergence of two closely related species of orioles found no recent gene flow despite their current geographic distribution. This paper examines on divergence between two closely related oriole species whose distribution in the highlands of SE Mexico is separated by the lowlands of the Isthmus of Tehuantepec. Icterus graduacauda is found west of the Isthmus and Icterus chrysater is found east of the Isthmus. We performed coalescent analysis of multiple loci using the program Isolation with Migration. We found that these species diverged roughly 300,000 years ago as a result of a vicariant event. In addition, there is no evidence that these two species currently exchange genes despite their recent divergence and their geographic proximity.