Shaping intraspecific variation: Development,ecology and the evolution of morphology and life history variation in tiger salamanders |
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Authors: | James P Collins Kim E Zerba Michael J Sredl |
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Institution: | (1) Department of Zoology, Arizona State University, 85287-1501 Tempe, AZ, USA;(2) Department of Human Genetics, University of Michigan, 48109 Ann Arbor, MI, USA;(3) Nongame Branch, Arizona Game and Fish Department, 221 West Greenway Road, 85023-4312 Phoenix, AZ, USA |
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Abstract: | The tiger salamander,Ambystoma tigrinum, is a geographically widespread, morphologically variable, polytipic species. It is among the most variable species of salamanders
in morphology and life history with two larval morphs (typical and cannibal) and three adult morphs (metamorphosed, typical
branchiate, cannibal branchiate) that vary in frequency between subspecies and between populations within subspecies. We report
morphometric evidence suggesting that branchiate cannibals arose through intraspecific change in the onset or timing of development
resulting in the wider head and hypertrophied tooth-bearing skull bones characteristic of this phenotype. We also quantified
bilateral symmetry of gill raker counts and abnormalities, then evaluated fluctuating asymmetry as a measure of the developmental
stability of each morph. There was a significant interaction between fluctuating asymmetry of developmental abnormalities
in cannibals and typicals and the locality where they were collected, suggesting that relative stability of each phenotype
could vary among populations. While altered timing of developmental events appears to have a role in the evolution and maintenance
of morphs, novel phenotypes persist only under favorable ecological conditions. Predictability of the aquatic habitat, genetic
variation, kinship, body size, intraspecific competition and predation all affect expression and survival of the morphs inA. tigrinum. This taxon provides an excellent model for understanding the diversity and complexity of developmental and ecological variables
controlling the evolution and maintenance of novel phenotypes. |
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Keywords: | fluctuating asymmetry heterochrony intraspecific morphology polymorphism |
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