Abstract

We present a unique perspective on the role of historical processes in community assembly by synthesizing analyses of species turnover among communities with environmental data and independent, population genetic-derived estimates of among-community dispersal. We sampled floodplain and terra firme communities of the diverse tree genus Inga (Fabaceae) across a 250-km transect in Amazonian Peru and found patterns of distance-decay in compositional similarity in both habitat types. However, conventional analyses of distance-decay masked a zone of increased species turnover present in the middle of the transect. We estimated past seed dispersal among the same communities by examining geographic plastid DNA variation for eight widespread Inga species and uncovered a population genetic break in the majority of species that is geographically coincident with the zone of increased species turnover. Analyses of these and 12 additional Inga species shared between two communities located on opposite sides of the zone showed that the populations experienced divergence 42,000-612,000 y ago. Our results suggest that the observed distance decay is the result not of environmental gradients or dispersal limitation coupled with ecological drift--as conventionally interpreted under neutral ecological theory--but rather of secondary contact between historically separated communities. Thus, even at this small spatial scale, historical processes seem to significantly impact species' distributions and community assembly. Other documented zones of increased species turnover found in the western Amazon basin or elsewhere may be related to similar historical processes.

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Authors

Dexter KG, Terborgh JW, Cunningham CW

Institution

Biology Department, University Program in Genetics and Genomics, Nicholas School of the Environment and Earth Sciences, Duke University, Durham, NC 27708, USA.

Source

Proceedings of the National Academy of Sciences of the United States of America 109:20 2012 May 15 pg 7787-92

MeSH

Base Sequence
Bayes Theorem
Biodiversity
Biota
Demography
Environment
Fabaceae
Genetic Variation
Genetics, Population
Genome, Plastid
Geography
History, Ancient
Models, Genetic
Molecular Sequence Data
Peru
Phylogeography
Principal Component Analysis
Sequence Analysis, DNA
Soil
Species Specificity
Trees
Tropical Climate

Pub Type(s)

Historical Article
Journal Article
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.

Language

eng

PubMed ID

22547831