Quantifying the importance of niches to tree species coexistence in a tropical forest
06 / 2011 - onbekend
Long-standing ecological theory states that, in order to coexist, species must differ in some way in their niches. However, a growing body of recent theoretical work has shown that community patterns can often be replicated by neutral models in which all species and individuals are identical. This has spurred an ongoing debate on the importance of niches to the maintenance of species diversity, above all in high-diversity plant communities such as tropical forests. Here, we propose to quantify the importance of niche differences to species coexistence in a tropical tree community on Barro Colorado Island, Panama, by applying new theoretical tools to a large demography dataset of 60 coexisting tree species spanning 30 years. Using the latest generation of population models that capture all life cycle stages (Integral Projection Models), population growth rates will be calculated as a function of tree density, habitat, and census interval. A positive population growth rate when rare is considered a fundamental coexistence criterion. Such invasion growth rates are examined for a suite of alternative models that include or omit various niche mechanisms and thereby assess which processes at which life stages contribute most to species coexistence. Our study will be the first to integrate niche processes that have hitherto been studied in isolation, and thus provides novel insight into the forces maintaining diversity in a species-rich ecosystem. This understanding will help us project the future of tropical forests under different scenarios of climate change, and thus develop better strategies for sustaining these biodiverse ecosystems.