Population Variation in Survival and Metamorphosis of Larval Salamanders (Ambystoma maculatum) in the Presence and Absence of Fish Predation

Our objectives were to determine if larval spotted salamanders, Ambystoma maculatum, derived from four populations, differed in growth, survival, activity, and metamorphosis, and if these populations responded differently to predation pressure. Using a 4 x 2 randomized block design, equal numbers of larvae from these populations were reared in artificial pools in the presence and absence of a natural predator, the bluegill sunfish, (Lepomis macrochirus.). Population source was a prominent factor in the observed differences in larval survival, metamorphosis, and activity. Fish presence significantly decreased larval growth and activity, as well as pool resource density, but did not affect larval survival or metamorphosis. No interactions were revealed between population source and fish presence indicating each factor acts independently. Our results suggest that historical environmental differences among aquatic habitats may have influenced the interpopulational differences in larval survival, metamorphosis, and activity. If these life history traits have a heritable genetic basis, and gene flow among populations is low, genetic differentiation among populations may result. Significant differences among populations in our artifical pond experiment indicate that such differentiation is possible.