Spatial and temporal variation in climate and conflict explains 35 years of developmental plasticity in a polyphenism

Environmental variation regulates the selective mechanisms acting on developmental plasticity and phenotypic expression. Animals with complex life cycles exhibit a great deal of developmental plasticity associated with fitness tradeoffs mediated by spatiotemporal variation. The objective of our study was to uncover the spatial (across seven natal ponds) and temporal (across 35 years) variation in developmental plasticity of 692 Arizona tiger salamanders Ambystoma mavortium nebulosum using lifetime mark–recapture data. Specifically, we evaluated spatiotemporal variation in the developmental plasticity of the following fitness‐related traits: 1) size‐at‐age relationships for larval growth, 2) larval body size, 3) adult phenotypic expression (i.e. aquatic versus terrestrial morphs), and 4) adult age at first reproduction. The spatial variation in developmental plasticity of all four traits was closely correlated with environmental gradients of mortality risk associated with hydroperiod, microclimate, and conspecific conflict (competition and predation). Developmental plasticity also varied temporally, as both phenotypes reproduced at older ages during earlier cohorts with colder temperatures and heavier snowpacks (1988–1997) compared with mid‐ (1998–2007) and late (2008–2014) cohorts of warmer temperatures and lighter snowpacks. Our results provide novel insight into how spatial and temporal processes jointly explain the maintenance of developmental plasticity and highlight the value of long‐term studies of natural populations.