PS 84-204 - Population growth rate and variability are jointly driven by past and current resource conditions for a tide pool specialist

Friday, August 11, 2017
Exhibit Hall, Oregon Convention Center
Benjamin G. Van Allen, SIO: Marine Biology Research Division, University of California San Diego, La Jolla, CA and Jonathan B. Shurin, Ecology, Behavior and Evolution, University of California- San Diego, La Jolla, CA

Understanding the drivers of variation in population growth is a key goal of population ecology. For organisms which live in and move between discrete patches of habitat which vary in resource productivity, large changes in the resource environment can occur during an individuals lifetime. How populations will respond to these changes could depend on how individual plasticity in condition or reproductive strategies respond to changing resource conditions. We tested how the copepod Tigriopus californicus responded to four levels of environmental resource abundance after experiencing natal to adult development in relatively low or high resource availability. Since natural populations of T. californicus occur in closely linked but highly environmentally variable tide pool metapopulations, we hypothesized that that they would show high sensitivity to both past and current habitat conditions.


During colonization of novel environments which varied from very low to very high resource conditions, both the population growth rate and the amount of variation observed in population growth rate depended on both current conditions and carryover effects of colonists natal habitat. Population growth rates were higher in lower resource environments when colonists arrived from a high nutrient environment. In high resource environments, colonists from both natal environments were able to reach high population size. However, colonists from high resource environments dependably exhibited similar population growth rates, while colonists from low resource environments produced highly variable growth rates. Across 24 replicated populations in the two higher current resource levels, colonists from low nutrient conditions produced population dynamics which were nearly three fold more variable than colonists from high nutrient conditions. This significant difference in population variability is a novel but tentative result, and is likely driven by increased individual variability in colonists from low resource conditions. That differences in variation did not occur in the 24 replicated populations in lower current resource conditions suggests a context dependent interaction between the source of this individual variation and the current resource environment. High variability in population size is risky for population persistence.