| Abstract: |
| Size-structure is thought to be a critical feature of biological populations but its incorporation into ecological theory of competition is so far limited. Growing taller, especially for a tree, can mean access to resources otherwise blocked, and hence strategy variation related to how quickly an individual may grow, or the maximum size it may reach, or at what height or how much it reproduces, has the potential to create coexistence opportunities. Existing studies have only explored competitive coexistence of population structured by such hierarchical size effects to a limited degree. Particularly pressing is delineating which aspects of demography must negatively depend on the density of taller individuals to create niche differentiation opportunities, and which specific life history variation across species is involved in those niche opportunities. Here we investigate a variety of cases of a simple partial differential equation model of competition with continuous size structure to gain insight into these. We find that a negative dependence of the production of offspring on the density of taller individuals creates the opportunity for competitive coexistence, while negative density-dependence of recruitment, which acts equally on all recruiting individuals (who are smaller than all established individuals) does not. Work on density-dependent mortality is still in progress. |
|