Meeting Abstract

P3.75  Tuesday, Jan. 6  Decreased phenotypic plasticity in a trait undergoing extreme selection KULKARNI, SB*; MOSKALIK, CL; GOMEZ-MESTRE, I; BUCHHOLZ, DR; Univ. of Cincinnati, Cincinnati; Univ. of Cincinnati, Cincinnati; Estacion Biologica de Donana, Spain; Univ. of Cincinnati, Cincinnati kulkarsb@email.uc.edu

Directional selection can cause the mean value of a trait averaged across environments to change. However, the effect of such selection on phenotypic plasticity of the trait is not clear because plasticity and mean trait values may be controlled by different mechanisms. The spadefoot toad Scaphiopus couchii has evolved extremely short larval periods to survive highly ephemeral desert pools from ancestors using long lasting pools. To examine evolutionary change in plasticity in age and size at metamorphosis in response to pond duration, we reared individual tadpoles of Sc. couchii and its relatives Spea multiplicata and Pelobates cultripes in the lab at two water volumes and two temperatures starting at three developmental stages. All species accelerated development in the low water level treatment, but at the expense of reduced growth in Sp. multiplicata and Pb. cultripes, but not Sc. couchii. The percent increase in development rate and percent decrease in growth rate due to low water volume were greater in Spea and Pelobates compared to Scaphiopus at all stages and temperatures. Our results indicate that Sc. couchii has lower plasticity in age and size at metamorphosis in response to small water volumes compared to other two species. Nevertheless, Sc. couchii has remarkable habitat tracking in nature to achieve the largest body size possible for a given short duration pond, often leaving the pond the day before pond drying. Thus, our results do not favor the idea that ephemeral breeding ponds of Sc. couchii are predictably short thereby favoring reduced plasticity Rather, our results support the hypothesis of a mechanistic connection between regulation of larval period trait values and plastic responses to the environment.