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Research Interests

I am interested in how biological diversity evolves and is maintained.  I am currently focusing on two main questions:

1.  To what extent does local adaptation play a role in speciation?

The differentiation of populations into distinct species can be the result of local adaptation pushing populations apart, can be due to drift and other neutral evolutionary processes, or most likely, a combination of both.  I am trying to understand which evolutionary forces are responsible for the diversifications of the white proteas in South Africa.  The white proteas are a small subgenus (6 species) within the genus Protea, which are endemic to the Cape Floristic Region in southwestern South Africa.  The environments in which they live vary in water and nutrient availability so I am investigating the degree to which differentiation in traits associated with their use has been associated with speciation events.  I am doing this by comparing patterns of variation in neutral genetic markers with variation in water and nutrient related traits.  I will then relate these to soil and climate characteristics of their home environments.







2.  Community assembly of the Cape flora

I became interested in the questions of how communities are assembled through a side project on Pelargonium, a diverse genus in the Cape Floristic region.  Pelargoniums vary in many ways, including leaf morphology and floral morphology, but most spectacularly in their body plans.  They range from shrubs, to subshrubs, to stem succulents to acaulescent geophytes.  They can live in close proximity to each other, sometimes within inches.  I am interested in exploring how it is that pelargoniums can share space.    Do they tend to be found near closely related species, or more distantly related species?  I, together with collaborators, am investigating this question at two scales.  The first is at the scale of the individual.  How far from each individual do we find their nearest conspecific pelargonium?  How far from each individual do we find their nearest heterospecific pelargonium?  The second scale is across western South Africa.  We will explain the degree to which the co-occurrence of species is explained by genetic distance and morphological differences between the species.  We will then be able to address the question of how community assembly processes differ at different scales.

I am also interested in exploring similar questions within the genus Protea.  The presence or absence of every protea species at 60, 000 locations in South Africa has been mapped in the Protea Atlas Project.  These data will allow us to very throughly investigate the relative importance of different community assembly processes, such as selection and competition, at a wide variety of scales, ranging from 1/4 degree radius plots to larger landscape scales.