Sexual behaviour of the Black Mountain dusky salamander (Desmognathus welteri), and the evolutionary history of courtship in the Desmognathinae

Abstract

Plethodontid salamanders of the North American subfamily Desmognathinae offer excellent opportunities for an integrative understanding of the form, functions and phylogeny of sexual behaviour patterns. The first description of courtship in the Black Mountain dusky salamander Desmognathus welteri is presented. Once oriented toward their partners, males produce multiple tactile, visual and chemical stimuli that probably function to stimulate, or ‘persuade’, females to mate. Persuasion is accomplished by behaviour patterns that include head rubbing, butterfly, pulling and snapping, and perhaps nudging and tail undulation. Sperm transfer is indirect by a spermatophore that is deposited on the substrate during a sequence of behaviour patterns involving both sexes known as tail-straddling walk. Fine-scale synchronization and orientation of partners at this time is crucial for successful insemination. The evolutionary histories of eight sexual behaviour patterns for 19 taxa of desmognathine salamanders are then reconstructed. Our phyloethological analyses suggest that the courtship of desmognathines consists of a mosaic of ancestral (plesiomorphic) and derived (apomorphic) behavioural traits. The greatest variation among taxa involves behaviour patterns that are exhibited early in sexual encounters as, or shortly after, males orient toward females. Behaviour patterns that occur at closer range and most obviously are persuasive in function show less variation among taxa, and those that lead to sperm transfer (tail-straddling walk) are invariant. While our phyloethological analyses reveal aspects of the evolutionary history of behavioural form in the Desmognathinae, further work is needed before thorough analyses of behavioural functions can be conducted.