The influence of abiotic and biotic environmental factors at high elevation on the life cycle of a facultatively paedomorphic salamander

WCU Author/Contributor (non-WCU co-authors, if there are any, appear on document)
Elijah Carl Whilte (Creator)
Western Carolina University (WCU )
Web Site:
Joseph Pechmann

Abstract: Environmentally cued polymorphisms are excellent models for studying the origins of phenotypicplasticity. Facultative paedomorphosis in salamanders is a form of discrete phenotypic plasticity in whichaquatic larvae respond to environmental cues by either metamorphosing into a terrestrial subadult(complex life cycle) or maturing as a paedomorph in the aquatic larval body form (simple life cycle).There are two proposed selective mechanisms for the maintenance of paedomorphosis in salamanders: (1)“paedomorph advantage” (PA), in which a favorable aquatic habitat offers greater fitness to largerindividuals than the terrestrial habitat and smaller individuals metamorphose to escape competition and(2) “best of a bad lot” (BBL), in which small individuals maximize fitness in a growth-limitingenvironment by forgoing metamorphosis thereby allowing reproduction during the first breeding seasonand large individuals metamorphose to escape the suboptimal aquatic habitat. In this study, I examinedthe influence of abiotic and biotic factors on the life cycles of a facultatively paedomorphic salamander,Ambystoma talpoideum, at the highest elevation within its range in the southern Appalachian Mountainsin western North Carolina. This species has been studied extensively at low elevations, but the selectivefactors of the environment may be different at high elevations. This study consisted of three parts: (1)field surveys to characterize the breeding phenology and population structure, (2) a mesocosm experimentmanipulating temperature to determine the selective mechanism of facultative paedomorphosis in thesepopulations, and (3) aggression trials between metamorphic A. talpoideum and a fully terrestrial salamander endemic to this region to explore the potential for competitive exclusion of metamorphic A.talpoideum in the terrestrial environment. Field surveys revealed that these high-elevation populations aremajority paedomorphic, and paedomorphs can breed after metamorphs have left the wetland. Whiletemperature did not have an effect on the final body size of larvae in the mesocosm experiment, densitydid. No individuals metamorphosed before the first breeding season, but some metamorphosed thefollowing spring. Individuals that grew to a larger body size were more likely to metamorphose, whichsupports the BBL selective mechanism for facultative paedomorphosis in these populations. Aggressiontrials found low levels of aggression between metamorphic A. talpoideum and the fully terrestrialsalamander, Plethodon shermani. This might be because these two species inhabit different spatial nichesas they use burrows at different depths. This study suggests that facultative paedomorphosis can havedifferent adaptive mechanisms under a different regime of environmental conditions.

Additional Information

Language: English
Date: 2016
Ambystoma talpoideum, best of a bad lot, geographic variation, interspecific competition, phenotypic plasticity, polyphenism
Salamanders -- Morphogenesis -- North Carolina, Western
Morphology -- Environmental aspects
Salamanders -- Life cycles -- North Carolina, Western
Ambystoma -- North Carolina, Western

Email this document to