TY - JOUR
T1 - Genetics, morphology, and ecological niche modeling do not support the subspecies status of the endangered Southwestern Willow Flycatcher (Empidonax traillii extimus)
AU - Zink, Robert M.
N1 - Publisher Copyright:
© 2015 Cooper Ornithological Society.
PY - 2015/2/1
Y1 - 2015/2/1
N2 - The Willow Flycatcher (Empidonax traillii) breeds throughout much of the United States, northwestern Mexico, and southeastern and southwestern Canada. A subspecies found in the southwestern United States and northwestern Mexico, E. t. extimus (Southwestern Willow Flycatcher), is listed as endangered under the U.S. Endangered Species Act (ESA). This subspecies was described in 1948, based on comparisons of a few external morphological characters from an unstated number of specimens and localities, although it was excluded from the last official list of subspecies by the American Ornithologists' Union. Like most avian subspecies, its validity has not been tested with modern morphological or genetic methods. Recent assessments of the subspecies have assumed it to be a distinct taxon, and some authors have limited their comparisons to E. t. extimus versus E. t. adastus (the subspecies immediately to the north of E. t. extimus), excluding comparison to western (E. t. brewsteri) and eastern (E. t. traillii) subspecies. To test subspecies limits, I reanalyzed available quantitative data on plumage coloration, and genetic variation in mitochondrial DNA and nuclear loci, and found no support for the distinctiveness of the Southwestern Willow Flycatcher. A test of niche divergence suggested that the Southwestern Willow Flycatcher does not have a significantly different climatic niche from its nearest geographic neighbor, E. t. adastus. I suggest that the Willow Flycatchers of the Southwest represent peripheral populations of an otherwise widespread species that do not merit subspecific recognition, and are therefore inappropriately listed as endangered under the ESA.
AB - The Willow Flycatcher (Empidonax traillii) breeds throughout much of the United States, northwestern Mexico, and southeastern and southwestern Canada. A subspecies found in the southwestern United States and northwestern Mexico, E. t. extimus (Southwestern Willow Flycatcher), is listed as endangered under the U.S. Endangered Species Act (ESA). This subspecies was described in 1948, based on comparisons of a few external morphological characters from an unstated number of specimens and localities, although it was excluded from the last official list of subspecies by the American Ornithologists' Union. Like most avian subspecies, its validity has not been tested with modern morphological or genetic methods. Recent assessments of the subspecies have assumed it to be a distinct taxon, and some authors have limited their comparisons to E. t. extimus versus E. t. adastus (the subspecies immediately to the north of E. t. extimus), excluding comparison to western (E. t. brewsteri) and eastern (E. t. traillii) subspecies. To test subspecies limits, I reanalyzed available quantitative data on plumage coloration, and genetic variation in mitochondrial DNA and nuclear loci, and found no support for the distinctiveness of the Southwestern Willow Flycatcher. A test of niche divergence suggested that the Southwestern Willow Flycatcher does not have a significantly different climatic niche from its nearest geographic neighbor, E. t. adastus. I suggest that the Willow Flycatchers of the Southwest represent peripheral populations of an otherwise widespread species that do not merit subspecific recognition, and are therefore inappropriately listed as endangered under the ESA.
KW - Endangered Species Act
KW - Mitochondrial DNA
KW - Niche modeling
KW - Plumage coloration
KW - Subspecies
KW - Willow Flycatcher
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U2 - 10.1650/CONDOR-14-27.1
DO - 10.1650/CONDOR-14-27.1
M3 - Article
AN - SCOPUS:84921533538
SN - 0010-5422
VL - 117
SP - 76
EP - 86
JO - Condor
JF - Condor
IS - 1
ER -