PARENT SESSION
Oral Session 14: Reptiles and Amphibians I: Salamanders and Newts.
Presiding: K McCoy
Monday, August 2, 8:00 AM to 11:30 AM, Meeting Room D 136.

Components of fitness in a tiger salamander hybrid zone.

Fitzpatrick, Benjamin^*,1, ¹ Evolution and Ecology, Davis, CA

ABSTRACT- About 50 years ago, tiger salamanders from the southwestern U.S. (Ambystoma tigrinum mavortium) were released into the range of the native California tiger salamander (A. californiense). Hybridization has lead to the formation of a hybrid swarm in the Salinas Valley. Earlier work showed that invasion success of introduced alleles is habitat-dependent. Hybrid populations breeding in perennial ponds are virtually pure introduced while neighboring seasonal ponds maintain substantial frequencies of native alleles. Here I report on factors potentially contributing to divergent selection between seasonal and perennial breeding ponds. Nonnative advantage in perennial ponds may be largely explained by their ability to use an alternative, fully aquatic paedomorphic, life-history strategy. In addition, introduced tiger salamanders tend to lay more smaller eggs while natives lay fewer larger eggs. Escape performance also varies; native larvae have the highest burst-speed velocity while recombinant hybrids have the lowest. Insect predators may be more consistently abundant in seasonal ponds, creating stronger selection on escape performance. While these factors have probably delayed the process of genetic homogenization, they are unlikely to maintain the distinctiveness of native and introduced tiger salamander lineages.

Key words: life-history, performance, hybridization, genetics