New paper on stage-structured neutral biodiversity models published in Oikos

Many populations in the natural world exhibit pronounced stage structure, with individuals at different life stages having different survival and reproduction rates. Although there is a large literature on stage-structured models for single populations, stage structure has been less well studied in models of entire ecological communities. In our new paper, just published in Oikos, we explored the effect of allowing separate juvenile and adult stages on the dynamics of neutral biodiversity models.

We tested whether the addition of stage structure could fix known problems with spatial neutral models’ ability to fit cross-scale patterns of biodiversity in tropical forest tree communities. It could not, but our investigations led to useful mathematical results and new intuitions that have broad relevance for community ecology.

One particularly surprising result was that the presence of a juvenile stage, in which individuals cannot produce offspring, can substantially increase the biodiversity of the system. This occurs because it effectively increases the length of the historical time interval from which the parents of the current crop of individuals are sampled. The result likely applies beyond neutral models and to ecological communities in the real world.

The model predicts an almost linear increase in species richness as the ratio of juvenile to adult stage length increases (this is for a contiguous sample of 1 million individuals from an infinite landscape, with a per-capita speciation rate of 10-6 and a dispersal standard deviation equal to ten times the spacing between adults).

Chisholm, R. A. & T. Fung. Adding stage-structure to a spatial neutral model: implications for explaining local and regional patterns of biodiversity. (In press.) Oikos