GENETIC DIFFERENTIATION AND TAXONOMY IN THE HOUSE-WREN SPECIES GROUP

The current taxonomic status of the Troglodytes aedon (House Wren) spe cies group was evaluated by examining levels and patterns of isozyme d ifferentiation. Traditionally, three major taxonomic groups of contine ntal 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-evo lution'' and neighbor-joining algorithms. In addition, a cladistic fre quency parsimony analysis (FREQPARS) was performed. All of these metho ds revealed that the Northern House-Wren and the Brown-throated Wren a re sister taxa. There was little genetic differentiation (average Nei' s D = 0.010) among the seven subspecies of the Southern House-Wren ana lyzed. Average genetic distances between the Southern House-Wren, the Northern House-Wren, and the Brown-throated Wren are higher than any v alues reported for intraspecific variation in Nearctic birds, and are comparable to levels of divergence between other Nearctic and Neotropi cal species. Although the current taxonomy considers the three forms m embers 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 hypo thesis for the divergence of the Northern House-Wren and the Brown-thr oated Wren.