Seasonal sensitivity in the life history of a tropical leafwing (Anaea aidea; Nymphalidae) in a temperate climate

Seasonal climatic fluctuations affect the life history of most organisms. The tropical leafwing butterfly has a complex life cycle characterized by multiple generations within a year, distinct seasonal forms of adults, and long-lived adults. During a single year, population stage structure changes seasonally as do the probabilities of survival and growth and the amount of reproduction. We address the question: when the fates of individuals depend on both life stage and season, how do life stage transitions within each season contribute to population dynamics evaluated over the entire seasonal cycle?

We combined demographic rates estimated in the field and laboratory to construct a periodic stage-structured matrix model that encapsulates the progression of the population through each seasonal phase along with the demography within each phase. Using elasticity of the annual growth rate to demographic rates for each stage and season, we found that overwinter survival of adults has the largest overall effect on average annual dynamics. During the breeding season, reproduction and growth have the largest effect.

This research is the first application of a periodic megamatrix to model seasonal butterfly population dynamics and suggests which selection pressures maintain two distinct seasonal forms and life histories in leafwing butterflies.