Ephemeral Habitats and Variation in Behavior and Life History: Comparisons of Sibling Salamander Species

Abstract

We examined the relationship between behavior and life history traits in larvae of a sibling species pair of salamanders (Ambystoma barbouri and Ambystoma texanum) to address the impact of differences in habitat duration. The stream pools inhabited by A. barbouri are consistently more ephemeral than the ponds used by A. texanum, and the former is known to have a shorter larval period. We reared larvae from hatching through metamorphosis in a common laboratory environment, and monitored individual activity, feeding, growth and the length of the larval period. Our first goal was to examine whether these sibling species differ in behavior and growth rates. The stream species exhibited greater overall levels of activity, and both grew and fed at higher rates than the pond species. Our second goal was to examine the benefits of increased activity in terms of feeding, growth and developmental rates. Within species, increased activity was related to increased feeding, growth and developmental rates, and feeding rate was positively related to both growth and developmental rates. Our final goal was to address the costs of activity by looking at the effects of food deprivation and temperature on activity. The results of this experiment showed that larvae of the stream species reduced their activity in response to deprivation, and reduced activity to a greater degree at higher temperatures. The activity of pond species did not differ with either temperature or food deprivation. This study suggests that differences in behavior are associated with differences in habitat duration, and that behavioral variation may influence the timing of ontogenetic niche shifts such as metamorphosis through effects on growth and developmental rates.