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The sexual behavior of the North American plethodontid salamander, Desmognathus ocoee, was studied to determine whether courtship displays by males evolve through sexual selection of the females. The mating success for individual males varied from 14% to 69% relative to multiple potential mates for different encounters. The males' abilities to arouse or convince females to copulate were proposed to account for the differences in male mating success rates.

A comprehensive phylogeny for 45 extant species of eastern Plethodon based on DNA sequences of mitochondrial and nuclear genes is presented to examine rates and patterns of diversification and hybridization. Rapid diversification is seen within the glutinosus species group suggesting that the origin of species and the evolution of intrinsic reproductive isolating mechanisms may be decoupled in some cases and extensive hybridization may be a consequence rather than a cause of rapid diversification.

In experiments with red-backed salamanders, Plethodon cinereus, males were more aggressive toward and kept farther away from female partners that were socially polyandrous than those that were socially monogamous, regardless of the courtship season. It appeared that males tried to manipulate female partners into social monogamy by becoming more aggressive toward socially polyandrous partners. Includes tables.

Pheromones are chemosensory cues transmitted among members of the same species that elicit changes in reproductive behavior and physiology: Nonvolatile pheromones are detected by sensory neurons of the vomeronasal organ (VNO) and evidence suggests that sex steroid hormones modulate the responsiveness of the VNO to pheromones (Toyoda & Kikuyama, 2000). We tested whether testosterone affects male behavioral responses to pheromones as well as detection of pheromones by the sensory neurons of the VNO in Plethodon shermani, a terrestrial salamander for which specific pheromones have been behaviorally and molecularly characterized. Males were given implants that were blank or contained testosterone propionate (TP). Levels of nose tapping, a behavior specialized to deliver non-volatile pheromones to the VNO, were increased in TP-implanted males as compared to blank-implanted males. Preference for a substrate marked by females was increased in TP-implanted males relative to blank-implanted males. Finally, responsiveness of male VNO sensory neurons to pheromones in male mental gland extract was examined using agmatine uptake as marker of neuronal activation. Pheromones in male mental gland extract had previously been shown to activate VNO sensory neurons in females (Wirsig-Wiechmann et al., 2002). Here, using males, we found that more VNO sensory neurons were activated by application of male mentill gland extract compared to saline controls, although there was no effect of testosterone treatment. Our findings indicate that testosterone increases male behavioral responses to pheromones, but that it does not increase VNO sensory neuron response to pheromones contained in male mental gland extract. Future studies will examine testosterone modulation of VNO responsiveness to other sources of pheromones such as female body rinses.