Genetic differentiation and taxonomy in the House Wren species group

Abstract

The current taxonomic status of the Troglodytes aedon (House Wren) species group was evaluated by examining levels and patterns of isozyme differentiation. Traditionally, three major taxonomic groups of continental House Wrens have been recognized: (1) aedon (Northern House-Wren); (2) brunneicollis (Brown-throated Wren); and (3) musculus (Southern House-Wren). The isozyme data were converted to genetic distances and analyzed using UPGMA, Distance Wagner, Fitch-Margoliash, 'minimum-evolution' and neighbor- joining algorithms. In addition, a cladistic frequency parsimony analysis (FREQPARS) was performed. All of these methods revealed that the Northern House-Wren and the Brown-throated Wren are sister taxa. There was little genetic differentiation (average Nei's D = 0.010) among the seven subspecies of the Southern House-Wren analyzed. Average genetic distances between the Southern House-Wren, the Northern House-Wren, and the Brown-throated Wren are higher than any values reported for intraspecific variation in Nearctic birds, and are comparable to levels of divergence between other Nearctic and Neotropical species. Although the current taxonomy considers the three forms members of a single species, we recommend re-elevating the three groups to species status based on the genetic differences that indicate the three are distinct evolutionary 'units.' We propose a vicariant hypothesis for the divergence of the Northern House-Wren and the Brown-throated Wren.