Natal habitat alters population dynamics in novel environments

Background/Question/Methods

How populations are regulated, and why we often see different population dynamics despite apparently similar environmental conditions, is vital to the understanding of natural populations and communities. Increasing evidence indicates that strong, non-genetic, effects of past environments can alter life-history traits of individuals and their offspring. Such carry – over or maternal effects could scale up to alter initial population growth trajectories and population level processes such as competition, and thereby alter long-term dynamics of natural populations. However, very few empirical tests of how carry-over effects can alter population dynamics have been conducted. An increased understanding of how intra- and inter-generation carry-over effects modify the growth and survival of populations of individual organisms will increase the predictability of natural systems and further ecological theory.

To test how carry-over effects can affect population dynamics, we manipulated habitat quality during natal development and again after “colonization” of a new habitat during the adult phase for the flour beetle Tribolium castaneum. Small groups of beetles raised in poor or high quality habitat were placed into a factorial design of either poor or high quality colonization habitats. Populations were monitored over four months during which most completed multiple generations and reached an apparent carrying capacity. Additionally, we estimated important population parameters such as larval and adult survival rates, fecundity rates, and per capita cannibalism rates.

Results/Conclusions

Both the vital rates of each population and its carrying capacity were determined by a combination of the colonizers natal habitat the subsequent colonization habitat in which populations grew. Our results show that cohort level carry-over effects operating at a colonization event can lead to significantly different carry-capacity population sizes and individual traits in multiple habitat types. These results have important implications for metapopulation theory, invasive species theory, and for conservation and wildlife management.