Department of Biology

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Henrik Balslev

Local and regional palm (Arecaceae) species richness patterns and their cross-scale determinants in the western Amazon

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  • Ecoinformatics & Biodiversity

1. Local and regional patterns of plant species richness in tropical rain forests, aswell as their possible drivers, remain largely unexplored. The main hypotheses for local species richness (alpha diversity) are (i) local environmental determinism with species-saturated communities, and (ii) regional control, in which the immigration of species from the regional species pool (gamma diversity) determines how many species coexist locally. The species pool hypothesis suggests a combined influence of local and regional drivers on alpha diversity. Differences in gamma diversity may arise from divergent environmental conditions or biogeographic histories.
2. We investigated the cross-scale determinants of palm alpha and gamma diversity across the western Amazon using a large field-based data set: a census of all palm individuals in 312 transects, totalling 98 species. We used regression-based variation partitioning to understand how habitat, topography and region influence alpha diversity, and correlations to assess the importance of the present environment (climate, soil, regional topography) and history (long-term habitat stability) for average regional alpha diversity and gamma diversity, including the link between these two diversitymeasures (species pool effect).
3. Variation in alpha diversity was primarily explained by region (36%) and habitat (18%), whereas the effect of topography was negligible (1%). Within habitats, region was even more important (up to 69% explained variation). Within regions, habitat and topography covaried and had a variable but an important influence. The pure effect of topography remained ofminor importance (up to 13%).
4. Average regional alpha diversity was related to gamma diversity, precipitation seasonality and possibly long-term habitat stability. Gamma diversity was related to long-term habitat stability, and possibly current climate.
5. Synthesis. Gamma diversity strongly influenced alpha diversity, although a clear influence of local environment was also evident, notably habitat type, with a minor, more geographically variable effect of small-scale topography. Apart fromgamma diversity, the factormost strongly related to regional alpha diversity was precipitation seasonality, while gamma diversity itself was strongly linked to long-termhabitat stability. These results imply that plant species richness is contingent on both contemporary and historical factors with a strong link between local species richness and the regional species pool.

Original languageEnglish
JournalJournal of Ecology
Pages (from-to)1001–1015
Publication statusPublished - 2011

    Research areas

  • climatic stability, diversity, environmental filtering, Neotropical rain forests, plant community ecology, spatial scale, species pool effects, topography

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