Molecular systematics of short-horned lizards: biogeography and taxonomy of a widespread species complex.
We surveyed mitochondrial DNA (mtDNA) sequence variation in short-horned lizards (Phrynosoma douglasi) from throughout western North America and used these data to estimate an intraspecific phylogeny and to assess biogeographic scenarios underlying the geographic structure of lineages in this species. We sequenced 783 base pairs from 38 populations of P. douglasi and three putative outgroups (P. ditmarsi, P. orbiculare, P. platyrhinos). We detected high levels of nucleotide variation among populations and a spatial distribution of mtDNA lineages compatible with major geographic regions. The phylogenetic hypotheses best supported by the data suggest that P. douglasi, as currently described, is paraphyletic with respect to P. ditmarsi. Populations of P. douglasi from the Pacific Northwest (ID, CA, OR, WA) form a monophyletic group that is sister to the subsequent radiation of P. ditmarsi and other P. douglasi clades. These results suggest that divergences within this widespread species are fairly old. We focused on the genetic structure of populations of P. douglasi from a geographic perspective and interpreted the intraspecific phylogeny in light of geologic and climatic changes in western North America during the last 20 million years. The generally high levels of genetic variation found in these population comparisons are in accord with high levels of morphological variation in this species group; however, only in the Pacific Northwest region is there spatial congruence between these phylogenetic results and subspecific ranges based on previous morphological studies. We compared the evolutionary units delineated in this study with previously described subspecies of P. douglasi and evaluated the support (from morphology and mtDNA) for each population lineage in the phylogeny and the implications for the taxonomy of this group.
Zamudio
K R
KR
Department of Zoology, Box 351800, University of Washington, Seattle, Washington 98195, USA. zamudio@socrates.berkeley.edu
Jones
K B
KB
Ward
R H
RH
D000818:Animals; D004272:DNA, Mitochondrial / Q000235:genetics; D004777:Environment; D014644:Genetic Variation; D005828:Genetics, Population; D005843:Geography; D016013:Likelihood Functions; D008116:Lizards / Q000145:classification* / Q000235:genetics*; D009656:North America; D010802:Phylogeny
D004272:DNA, Mitochondrial