Paedomorphosis in Relation to Rates of Morphological and Molecular Evolution in the Salamander Aneides flavipunctatus (Amphibia, Plethodontidae)

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Abstract
Rates of morphological evolution among populations of the salamander A. flavipunctatus were analyzed using phylogenetic inferences drawn from protein comparisons. Protein evolution appears to proceed at a relatively constant rate in A. flavipunctatus. The protein comparisons indicate a high level of genetic subdivision among populations. Many populations probably evolved in relative isolation since the Late Pliocene or Pleistocene epochs. Morphological evolution within these populations has proceeded at highly variable rates. Populations from the humid redwood belt of central Mendocino and Sonoma counties [California, USA] appear to have changed least from the ancestral morphology. Rates of morphological change also have been relatively low in the Shasta and Santa Cruz [California, USA] isolates. Very rapid changes are indicated for populations from the northwestern portion of the species range; these changes are the result of pedomorphosis and phylogenetic analysis suggests that the morphology observed in these populations evolved independently at least 2 times. Previous studies indicate that retention of juvenile coloration patterns in the northwestern populations offers crypsis on the substrates used by A. flavipunctatus in this portion of its range. A genetic change altering growth rate may have allowed rapid responses of these populations to selection for cryptic coloration, simultaneously altering many other aspects of morphology. Genetic variation allowing developmental plasticity may be important in providing salamander populations with the evolutionary potential for adaptation to changing conditions.