Quantifying ecological, morphological, and genetic variation to delimit species in the coast horned lizard species complex (Phrynosoma)

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 106; no. 30; pp. 12418 - 12423
• Main Authors: Leaché, Adam D, Koo, Michelle S, Spencer, Carol L, Papenfuss, Theodore J, Fisher, Robert N, McGuire, Jimmy A
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 28.07.2009; National Acad Sciences
• Series: From the Cover
• Subjects: Animal Migration; Animal populations; Animals; Bayes Theorem; Biological Sciences; Biological taxonomies; Brain-derived neurotrophic factor; Brain-Derived Neurotrophic Factor - genetics; California; Cell Nucleus - genetics; Coasts; Conservation; Differentiation; DNA, Mitochondrial - chemistry; DNA, Mitochondrial - genetics; Ecological genetics; Ecology; Evolution; Genealogy; Genetic diversity; Genetic loci; Genetic Variation; Geography; Homeodomain Proteins - genetics; Horned lizards; Horns; Lacertilia; Lizards - anatomy & histology; Lizards - classification; Lizards - genetics; Mitochondrial DNA; Models, Genetic; Molecular Sequence Data; Morphology; Multivariate Analysis; Niches; Phrynosoma; Phrynosoma coronatum; Phylogenetics; Phylogeny; Population ecology; Population genetics; RAG1 protein; Reptiles & amphibians; Sequence Analysis, DNA; Skull; Species; Species Specificity; California; Baja California Mexico
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0906380106

Lineage separation and divergence form a temporally extended process whereby populations may diverge genetically, morphologically, or ecologically, and these contingent properties of species provide the operational criteria necessary for species delimitation. We inferred the historical process of lineage formation in the coast horned lizard (Phrynosoma coronatum) species complex by evaluating a diversity of operational species criteria, including divergence in mtDNA (98 specimens; 2,781 bp) and nuclear loci (RAG-1, 1,054 bp; BDNF 529 bp), ecological niches (11 bioclimatic variables; 285 unique localities), and cranial horn shapes (493 specimens; 16 landmarks). A phylogenetic analysis of mtDNA recovers 5 phylogeographic groups arranged latitudinally along the Baja California Peninsula and in California. The 2 southern phylogeographic groups exhibit concordance between genetic, morphological, and ecological divergence; however, differentiation is weak or absent at more recent levels defined by phylogeographic breaks in California. Interpreting these operational species criteria together suggests that there are 3 ecologically divergent and morphologically diagnosable species within the P. coronatum complex. Our 3-species taxonomic hypothesis invokes a deep coalescence event when fitting the mtDNA genealogy into the species tree, which is not unexpected for populations that have diverged recently. Although the hypothesis that the 3 phylogeographic groups distributed across California each represent distinctive species is not supported by all of the operational species criteria evaluated in this study, the conservation status of the imperiled populations represented by these genealogical units remains critical.