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.