Response of fowler's toad (Anaxyrus fowleri) to competition and hydroperiod in the presence of the invasive coastal plain toad (Incilius nebulifer)

摘要

Fowler's Toad (Anaxyrus fowleri) was historically abundant and widespread in various habitats, including urban and agricultural areas, in southern Louisiana. Coincident with intense anthropogenic disturbance, the abundance of the Coastal Plain Toad (Incilius nebulifer) has increased significantly in degraded habitats. Subsequently, A. fowleri is found only in forested areas near permanent water bodies that are not preferred breeding habitat of I. nebulifer. We hypothesized that larval competition with I. nebulifer, a species that breeds in extremely ephemeral habitat commonly found in disturbed areas, contributed to A. fowleri's decline. We raised tadpoles in intra-and interspecific competition in artificial ponds under simulated permanent and temporary breeding habitat conditions. Competition with I. nebulifer tadpoles, but not pond drying, resulted in a decrease in body size measures and a lower rate of survival to metamorphosis for A. fowleri tadpoles. Incilius nebulifer tadpoles were slightly larger in drying than in permanent ponds and were larger and had a higher rate of survival to metamorphosis in interspecific tanks than in intraspecific tanks, suggesting that it is easier for I. nebulifer to outcompete other species than conspecifics. The Coastal Plain Toad's superior competitive ability in temporary breeding sites may have resulted in ecological displacement and is potentially contributing to a decline of regionally sympatric populations of Fowler's Toad in degraded landscapes.