Predator-Induced Defenses in Five Species of Larval Ambystoma
While predator-induced plasticity has been demonstrated in a wide range of organisms, relatively few data exist to compare differences among species. In studies of predator-induced plasticity in amphibians, larval anurans have been widely examined, but there are fewer data for larval salamanders. We sought to examine morphological and behavioral defenses in larvae of five species of Ambystoma salamanders. We raised five species of larval mole salamanders (A. barbouri, A. gracile, A. laterale, A. maculatum, A. tigrinum) in separate lab experiments and exposed them to predator cues from larval dragonflies (Anax junius). Salamanders did not vary in their refuge use during the experiment, but A. gracile, A. laterale, and A. tigrinum reduced their activity in the presence of predators early in development. Dragonfly cues induced relatively few morphological changes across species: A. barbouri developed relatively large heads and deep tails, A. gracile and A. laterale developed relatively shorter heads, and A. maculatum developed relatively wider heads and shorter tails. Our results suggest that behavioral and morphological defenses in Ambystoma are highly variable among species and they appear to be less plastic than tadpoles and other salamander species.
Activity for five species of Ambystoma salamanders in the presence (closed circles) and absence (open circles) of aeshnid predator cues. Values are the grand means±SE of behavioral assays averaged across three binary observations (moving = 1, not moving = 0) for each individual on each of days 7, 14, 21, and 28. Asterisks indicate significant responses to predator cues (before Bonferroni correction).
Refuge use (mean±SE) for five species of Ambystoma salamanders in the presence (closed circles) and absence (open circles) of aeshnid predator cues. Values are the grand means±SE of behavioral assays averaged across three binary observations (using refuge = 1, out of refuge = 0) for each individual on each of days 7, 14, 21, and 28. Asterisks indicate significant responses to predator cues.
Morphological variables for five species of Ambystoma salamanders in the presence (closed circles) and absence (open circles) of aeshnid predator cues. Values are mass-independent treatment means±SE of animals measured at the end of the experiment on day 28. Asterisks indicate significant responses to predator cues.