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Historical effects on beta diversity and community assembly in Amazonian trees
Kyle G Dexter1, John W Terborgh, Clifford W Cunningham
1Biology Department, University Program in Genetics and Genomics, Nicholas School of the Environment and Earth Sciences, Duke University, Durham, NC 27708, USA.
Summary
Historical processes, not environmental factors, shape Amazonian tree communities. Secondary contact between historically separated Inga tree populations explains species turnover, revealing the significant impact of past events on current distributions.
Area of Science:
- Ecology
- Evolutionary Biology
- Genetics
Background:
- Community assembly is traditionally explained by environmental gradients and dispersal limitation.
- Neutral ecological theory posits that species distributions result from dispersal, speciation, and ecological drift.
- Understanding historical influences on community structure is crucial for ecological and evolutionary insights.
Observation:
- A 250-km transect in Amazonian Peru revealed distance-decay patterns in Inga tree communities.
- A zone of increased species turnover was identified within the transect, masked by conventional analyses.
- Population genetic data indicated a significant genetic break in multiple Inga species within this zone.
Findings:
- Geographic plastid DNA variation in eight widespread Inga species showed a population genetic break.
- This genetic break coincided geographically with the zone of increased species turnover.
- Divergence times for populations on either side of the zone ranged from 42,000 to 612,000 years ago.
Implications:
- The observed distance decay is attributed to secondary contact between historically separated Inga communities, not environmental factors.
- Historical processes significantly influence species distributions and community assembly, even at small spatial scales.
- Similar historical processes may explain other zones of increased species turnover in the Amazon basin and beyond.
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