EVIDENCE OF CONSTRAINED PHENOTYPIC EVOLUTION IN A CRYPTIC SPECIES COMPLEX OF AGAMID LIZARDS

• Published in: Evolution Vol. 65; no. 4; pp. 976 - 992
• Main Authors: Smith, Katie L., Harmon, Luke J., Shoo, Luke P., Melville, Jane
• Format: Journal Article
• Language: English
• Published: Malden, USA Blackwell Publishing Inc 01.04.2011; Wiley Subscription Services, Inc; Oxford University Press
• Subjects: Agamidae; Animals; Base Sequence; Bayes Theorem; Biological Evolution; Biological taxonomies; Body Weights and Measures; Conservation; Datasets; Divergent evolution; DNA, Mitochondrial - genetics; Ecological genetics; Ecological modeling; Ecosystem; Evolution; Evolutionary genetics; Genes; Genes, RAG-1 - genetics; Genotype & phenotype; Geography; Likelihood Functions; Lizards; Lizards - anatomy & histology; Models, Biological; Molecular Sequence Data; morphological evolution; morphological stasis; nonadaptive; Northern Territory; Phenotype; Phylogenetics; Phylogeny; Queensland; Reptiles & amphibians; Sequence Analysis, DNA; Species Specificity; Western Australia; Western Australia; Northern Territory; Queensland
• ISSN: 0014-3820; 1558-5646
• DOI: 10.1111/j.1558-5646.2010.01211.x

Lineages that exhibit little morphological change over time provide a unique opportunity to explore whether nonadaptive or adaptive processes explain the conservation of morphology over evolutionary time scales. We provide the most comprehensive evaluation to date of the evolutionary processes leading to morphological similarity among species in a cryptic species complex, incorporating two agamid lizard species (Diporiphora magna and D. bilineata). Phylogenetic analysis of mitochondrial (ND2) and nuclear (RAG-1) gene regions revealed the existence of eight deeply divergent clades. Analysis of morphological data confirmed the presence of cryptic species among these clades. Alternative evolutionary hypotheses for the morphological similarity of species were tested using a combination of phylogenetic, morphological, and ecological data. Likelihood model testing of morphological data suggested a history of constrained phenotypic evolution where lineages have a tendency to return to their medial state, whereas ecological data showed support for both Brownian motion and constrained evolution. Thus, there was an overriding signature of constrained evolution influencing morphological divergence between clades. Our study illustrates the utility of using a combination of phylogenetic, morphological, and ecological data to investigate evolutionary mechanisms maintaining cryptic species.