How much biodiversity can be supported via life-history trade-offs?

Dept/School	Department of Biology, University College London
Project Supervisor(s)	Dr D Murrell
Funding Availability	Directly Funded Project (European/UK Students Only) (Popup Window - Please disable popup blockers)
Application Deadline	18 February 2009

There is no such thing as a Darwinian Demon: an organism that maximises all aspects of fitness simply does not exist. Resource allocation in one trait (eg growth/fecundity) must be offset by diverting resources from another life-history trait (eg survival/competitive ability), and this leads to a number of life-history trade-offs that have been observed in natural and laboratory populations and communities. The theoretical literature for the potential of these trade-offs to enable the coexistence of competing species is large. Yet, a major drawback of this body of work is that almost all studies have considered only 1 trade-off in isolation, and have typically considered the coexistence of only 2 species. In contrast, most communities may have 10’s (eg grassland plants) or even 100’s (eg rainforest trees) of competing species and it remains an open question as to how many species can coexist on one trade-off. When is it possible for more than 2 species to coexist on one trade-off? Do some trade-off functions (shapes/relationships) lead to the coexistence of more species than others? Do trade-offs in some life-history traits (eg fecundity, survival, resistance to infection) lead to a greater level of biodiversity than others? Moreover, how do trade-offs interact? For n trade-offs, how many species, S, can coexist? Does S scale linearly with the number of trade-offs so that S = 2n? Or are trade-offs more powerful, so that S = n2? If it is the former, then in a tropical rainforest, where there may be 300-400 species found within a few hectares, 150-200 trade-offs would be required to explain the maintenance of biodiversity. Conversely, if trade-offs act in a non-linear way, then only 20 may be required, suggesting it may be relatively easy to empirically measure the role of trade-offs in maintaining species-rich communities. This studentship will use mathematical modelling to address these issues and ask exactly how important trade-offs might be in generating and maintaining biodiversity for competitive interactions both with and without natural enemies.

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