Competition between Larval Rana palustris and Bufo americanus Is Not Affected by Variation in Reproductive Phenology

Abstract

Larval Rana palustris and Bufo americanus were raised in 27 experimental ponds. Each species was introduced to the ponds at seven different times relative to the time of introduction of the other species. Density of conspecifics affected the growth rates of both species. Density of Bufo affected the growth rate of Rana. Neither species responded to the relative time of introduction of the other species. Bufo that hatched and were introduced to ponds earlier had higher survival rates, longer larval periods, and emerged at small sizes than Bufo that were introduced later. They apparently responded to their own density with altered rates of growth and development. Bufo metamorphic timing may also have been influenced by changes in environmental temperature. Bufo americanus and R. palustris frequently occur in the same ponds in nature, and the eggs used in the experiment were collected from the same pond. The low level of interspecific competition may reflect coadaptation to avoid competition.