"Coexistence through life history variations in an explicit patch age model"Staggs, JonA mechanistic understanding of coexistence remains a prominent challenge in ecological theory. Classical hypotheses in forest community ecology propose that disturbances and patch dynamics enable coexistence among species with life history strategies ranging from gap specialist to shade tolerant, often called “successional niche” differentiation. However, prior mathematical models have not fully delineated which life history strategies can promote coexistence under disturbance and succession. We build upon a PDE model that integrates explicit patch aging with disturbances and within-patch competitive dynamics. In particular, we incorporate the age of reproductive maturity as a life history trait. We investigate trade-offs against the age of reproductive maturity under two types of density dependence, namely on reproduction and mortality. In both cases, we identify multiple trade-offs against the age of first reproduction including offspring survival to adulthood, sensitivity of offspring survival to competition, and adult survival, that all enable coexistence. Many of the results can be derived analytically and in the less tractable cases, we conduct numerical simulations. We use the BCI census data to look in particular for the occurrence of an interspecific tradeoff between age of first reproduction and offspring survival to adulthood, which could arise from the often-reported growth-survival tradeoff in saplings among tree species that do not differ drastically in their size of reproductive maturity. Indeed we find support for this trade-off among tree species on BCI, suggesting it could play a role in competitive coexistence there. We also find our incorporation of an age of first reproduction leads to cycling in total density in some regions of parameter space (especially high reproduction). We are investigating if this is an essential feature of this addition, or if cycles disappear when the age of first reproduction is modeled as a distribution rather than as one specific value. |
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