PhD Thesis Wolf Eiserhardt
Studies on the Ecology, Biogeography and Evolution of Palms (Arecaceae)with Focus on the Americas
On Wednesday 14 September 2011 at 13:00, Wolf Eiserhardt defended his PhD dissertation
Abstract
The palm family (Arecaceae) increasingly serves as a model system to study the ecology and evolution of tropical ecosystems. This volume covers a wide range of topics in the areas of palm community ecology, macroecology, biogeography, and phylogeny, with a focus on the bridge between ecological and evolutionary processes. These topics fall into four categories: (i) Previous empirical evidence on the factors influencing palm species distributions, community composition, and species richness was summarised in a hierarchical scale framework. The effects of different components of the abiotic environment, biotic interactions, and dispersal are integrally dependent on spatiotemporal scale. Historical, including evolutionary factors are clearly important for palm distributions and diversity. (ii) Broad-scale patterns of palm species richness and phylogenetic turnover were studied across the Americas. Richnessenvironment
relationships were found to be spatially variable; richness-water correlations decreased in strength, and richness-energy correlations increased in strength with latitude, indicating complex and systematic interactions between factors. Evolutionary history has a significant impact on continental-scale palm distributions, reflected in phylogenetic turnover among regional assemblages. A novel analytical framework was developed to separate the effects of phylogenetic niche conservatism and secular dispersal limitation. (iii) Local palm communities in the Americas were investigated in detail, beginning with a review of previous reports assessing diversity and growth-form composition. Western Amazon palm communities were analysed with newly collected field data. Habitat differences are integral in species richness, growth-form composition, and phylogenetic structure of American palm communities. Moreover, species richness is associated with climatic and biogeographic history, which also affects the phylogenetic structure of western Amazonian palm communities. (iv) The diversification history of
the New-World-endemic palm subtribe Bactridinae was studied with nuclear and plastid DNA. The resulting well-resolved and -supported phylogeny refutes, in part, previous
morphology-based classifications and phylogenetic hypotheses. Signatures of Andean uplift, and possibly Cenozoic climate change were identified from the dating of Bactridinae diversification. In summary, present day patterns of palm diversity and distributions were found to depend on both current ecological processes and the dynamics of speciation, extinction, niche evolution, and secular migration in response to past environmental change.
Wolf completed his PhD at the Ecoinformatics and Biodiversity Group, Department of Bioscience, Faculty of Science and Technology, Aarhus University.
