Priority effects and desert anuran communities

Abstract

The roles of priority effects and predation in structuring anuran communities have not been considered important in desert environments characterized by highly ephemeral pools and anuran species that breed synchronously. Predation is one mechanism that can set the stage for priority effects to be important, especially in ephemeral pools where resources are limiting and densities are high. We observed oophagy by Scaphiopus couchii Baird, 1854 on eggs of Bufo speciosus Girard, 1854 in the field and conducted laboratory experiments to test the hypothesis that S. couchii tadpoles would reduce B. speciosus survivorship via predation. Three-day-old S. couchii tadpoles reduced hatching success of B. speciosus eggs by nearly 90%. When S. couchii and B. speciosus eggs were laid the same day, S. couchii tadpoles reduced B. speciosus egg survivorship by 56%. Our results indicate that priority effects and predation may play an important role in influencing species composition of anuran assemblages in desert regions. Our study provides more support for the need to reevaluate the current paradigm in aquatic ecology that suggests predation does not play a role in structuring community assemblages in highly ephemeral pools.