Plasticity: how does environmental information impact individuals?

Anticipatory plasticity in spadefoot toads

I study various aspects of plasticity in spadefoot toads. Individual tadpoles within a family can develop either into an omnivore morph (small, slowly developing, eat detritus) or a carnivore morph (large, develop rapidly, eat shrimp and other tadpoles). Omnivores are favored in large, long-lasting ponds, whereas carnivores are favored in small, rapidly drying ponds.  I have found that spadefoot eggs exposed to a nutrient-rich food, shrimp, display traits at hatching that will allow them to be better competitors for this food resources when they are old enough to forage.  This anticipatory plasticity allows very early developmental stages to sense, process, and respond to environmental information. It may be common for plasticity to evolve from using information about current environments into using anticipatory cues that signal future environments.

Parental effects in spadefoot toads

I have also found evidence for a non-adaptive maternal effect in spadefoot toads. Overconditioning of animals is correlated with high offspring mortality; an effect with broad implications for captive breeding programs.

Polyphenism in a predatory rotifer

I study plasticity across generations in rotifers, Asplanchna brightwellii. These planktonic predators exhibit a small, sac-shaped form unless their mother has ingested vitamin E – then daughters are larger, humped, and presumably better at consuming large prey. Vitamin E also triggers the production of mictic females that reproduce sexually – these animals are otherwise parthenogenetic. My ongoing work describes the plasticity in this system as well as its function, ecology, and evolution.

Evaluating the “buying time” hypothesis

Polyphenism of Asplanchna brightwellii

Phenotypic plasticity allows an individual organism to adjust its phenotype in direct response to changes in its environment, but the role of plasticity in evolution remains debated. It has long been argued that plasticity may be critical for allowing a population to become established or persist in a new or changing environment. Plasticity-mediated persistence may then indirectly facilitate evolution by buying time for genetic adaptation to occur. This ‘buying time’ hypothesis likely represents the predominate route through which plasticity facilitates evolution. However, little empirical work has evaluated the hypothesis.

I use A. brightwellii as a study system to address this hypothesis. My work brings together lines of evidence through multiple experiments to address the extent to which preexistent plasticity is of utility and responsible for persistence of individuals and populations in new environments.