Ecological separation in a polymorphic terrestrial salamander

When studying speciation, researchers commonly examine reproductive isolation in recently diverged populations.  Polymorphic species provide an opportunity to examine the role of reproductive isolation in populations that may be in the process of divergence.  We examined a polymorphic population of terrestrial salamanders (Plethodon cinereus) for evidence of sympatric ecological separation by color morphology.  Recent studies have correlated temperature and climate with color morphology in this species, but no studies have looked at differences in diet or mate choice between color morphs.  We used artificial cover objects to monitor salamander diet, mating preference and surface activity over a two year period.  We detected differences in diet and mate preference between striped and unstriped color morphs.  The diets of striped individuals were significantly more diverse and were made up of more profitable prey than the diets of unstriped salamanders.  Opposite sex pairs tended to be made up of individuals of the same color morph and striped males were able to attract larger females than were unstriped males. We corroborate findings of earlier studies suggesting that the unstriped form is adapted to warmer conditions.  Unstriped individuals were the first to withdraw from the forest floor as temperatures fell in late fall and they tended to be found at warmer temperatures than did striped salamanders.  We conclude that the two color morphs exhibit some degree of ecological separation and tend to mate assortatively, but are unlikely to be undergoing divergence given the observed frequency of intermorph pairings.