Spatial variation in coral demography using integral projection models

Background/Question/Methods

Corals have complex life-histories including sexual and asexual reproduction, fission and fusion of colonies, and alack of discrete stage structure that makes demographic modeling a particular challenge. Previous studies have usedmatrix models for coral population dynamics; however, this approach is limited by arbitrary imposition of size classesand parameter estimation requirements that increase multiplicatively with the number of size classes. In contrast,integral projection models (IPMs) use biologically meaningful, continuous functions for growth, survivorship, and fecundity as a function of size, which can be fit from data using mixed-model approaches in a likelihood framework.Here, we compare population projections for three species of coral (Montipora capitata, Porites lobata, Porites compressa) across thirteen transects around Maui (Hawaii,USA).  

Results/Conclusions

We fit individual growth, mortality, and recruitment at all sites, with site as a fixed effect, coral cover as covariate, and quadrat and year as a random effects. Spatial variation was of larger magnitude than temporal variation. We found site-specific differences in mortality and growth rate that were consistent across years and resulted in important differences in dynamics.  We discuss how spatial patterns of variation relate to local site characteristics and management regime.