General Research Interests and Experience
My research focuses on understanding patterns of plant species diversity in the Neotropics, particularly in the Andes, and investigation of the historical processes that have shaped plant distributions. This involves laboratory work to assemble extensive DNA sequence data sets, fieldwork (Argentina, Bolivia, Peru, and Belize), and traditional herbarium taxonomy (Amicia and Mimosa, Leguminosae) and species identifications (general Neotropical).
Current Project - Evolution of Species Diversity
The aim of my D.Phil. project is to understand the origins and historical assembly of the unique plant diversity in Andean seasonally dry tropical forests (SDTF). These forests, although not as species-rich as Neotrpical rain forests, are especially rich in narrowly-restricted endemics with c. 46 % endemism for woody plants in some inter-Andean valleys, but the origins of this high endemism remain poorly understood.
One of the main questions I am looking at is the role of geographic isolation and dispersal limitation in generating high endemic species diversity. Dry forests are markedly disjunct in their distribution in the Andes, with isolated patches scattered in the inter-Andean valleys from Colombia to Northern Argentina, and this suggests that geographic isolation in terms of dispersal limitation might have played a major role in species diversification in similar ways to many isolated oceanic island systems.
I am using DNA sequence data to reconstruct densely sampled phylogenies for three study groups, Amicia, Mimosa (Leguminosae) and Tecoma (Bignoniaceae), and molecular dating methods in conjunction with fossil data to date these phylogenies. Results show clearly that endemic species diversity in Andean SDTF started accumulating during the early stages of Andean uplift c. 10-15 million years ago, and that individual species found in these dry forests can be as old as 16 million years (My). The relative antiquity of Andean SDTF lineages and species stands in stark contrast to other Andean biomes such as páramos which are dominated by more recent, 2-4 My old and in some cases, very rapidly diversifying clades. This suggests that the Andean biodiversity hotspot is complex and highly heterogeneous in its assembly.
In terms of plant diversity, Andean SDTFs harbour levels of unique diversity exceeding the Galapagos Islands which have 43 % endemism in their vascular plant flora. As yet, no formal protected areas of dry forest have been established exist in these inter-Andean valleys of Peru where highest plant endemism is found. We aim to highlight the conservation value of the endemic species diversity of these dry forests via a better understanding of their species diversity and evolutionary history.
Previous Work - Neotropical Gingers
My previous research focused on diversification of the tropical amphi-Atlantic genus Renealmia (Zingiberaceae) that spans Africa and the Neotropics. Renealmia is the only genus of the ginger family (Zingiberaceae) native to Central and South America, with most of the species diversity in Zingiberaceae in south-east Asia. Molecular data revealed patterns of recent diversification in Renealmia on both sides of the Atlantic, but especially so in the more species-rich Neotropics. The phylogeny also suggests that Renealmia has attained its amphi-Atlantic distribution by long-distance oceanic dispersal from Africa to South America during the Miocene (8-28 million years ago). The diversification of Renealmia in Africa and the Neotropics can be used to test Gentry's assertion that the disparity of plant species diversity between Africa and the Neotropics lies in an excess of neotropical speciation rather than African extinction. The results of our study indicate that this is indeed the case, but increased taxon sampling and species-level resolution in the Reanalmia phylogeny are needed to further explore this question.
Särkinen, T.E., Newman, M.F., Maas, P.J.M., Maas, H., Poulsen, A.D., Harris, D.J., Richardson, J.E., Clark, A., Hollingsworth, M.L., Pennington, R.T. 2007. Recent oceanic long-distance dispersal and divergence in the amphi-Atlantic rain forest genus Renealmia L.f. (Zingiberaceae). Molecular Phylogenetics and Evolution 44: 968-980.