Filling ephemeral ponds affects development and phenotypic expression in Ambystoma talpoideum

Abstract

Abstract Populations and communities are often greatly affected by disturbances and variation in abiotic habitat conditions. Many of these effects are contingent on relatively predictable, yet still variable, environmental conditions that drive the life history strategies and development pathways of organisms in those habitats. However, much focus has been placed on aspects of such changes that cause mortality or movement from patches, whereas a multitude of outcomes can occur in natural systems. In lentic freshwater habitats, hydroperiod is a defining environmental characteristic, with temporary ponds supporting distinct communities of organisms with complex life cycles and plastic developmental trajectories. Little consideration has been given to the effects of refilling of ponds with variable hydroperiods, as lengthening the hydroperiod can extend the time organisms spend in their aquatic stages, allowing for the acquisition of more resources. We hypothesised that increasing the volume of small ponds and adding competitors (Ambystoma maculatum) at the time of filling would interactively affect the development and phenotypic expression of Ambystoma talpoideum. We introduced larval A. talpoideum to experimental mesocosms and manipulated water level (small, low volume mesocosms; filled, full mesocosms) and the addition of competitors (A. maculatum) at the time of filling in a 2 × 2 factorial design. We found that low volume mesocosms were dominated by metamorphs, while filling resulted in a more even mix of metamorphs, larvae and paedomorphs in full mesocosms. Filling resulted in larger metamorphs and paedomorphs, but did not affect larvae, whereas addition of A. maculatum shortened the larval period of metamorphs. We provide evidence that changes in abiotic habitat conditions, such as variation in the volume of ponds, can shift the development and phenotype of organisms. This plasticity may allow species to ensure the success of populations under both improvement and deterioration of environmental conditions. Hence, phenotypes like paedomorphic A. talpoideum can breed sooner than metamorphs, theoretically maximising the fitness of both individuals and populations.