Introgression across evolutionary scales suggests reticulation contributes to Amazonian tree diversity

Hybridization has the potential to generate or homogenize biodiversity and is a particularly common phenomenon in plants, with an estimated 25% of plant species undergoing interspecific gene flow. However, hybridization in Amazonia's megadiverse tree flora was assumed to be extremely rare despi...

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Bibliographic Details
Published in:Molecular ecology 2020-11, Vol.29 (21), p.4170-4185
Main Authors: Schley, Rowan J., Pennington, R. Toby, Pérez‐Escobar, Oscar Alejandro, Helmstetter, Andrew J., Estrella, Manuel, Larridon, Isabel, Sabino Kikuchi, Izai Alberto Bruno, Barraclough, Timothy G., Forest, Félix, Klitgård, Bente
Format: Article
Language:English
Subjects:
Angiosperms
Biodiversity
Flora
Gene flow
Genomes
Genotypes
Hybridization
Interspecific
Loci
phylogenomics
Phylogeny
Plant diversity
population genomics
rainforest
speciation
Species
Sympatric populations
Sympatry
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Summary:Hybridization has the potential to generate or homogenize biodiversity and is a particularly common phenomenon in plants, with an estimated 25% of plant species undergoing interspecific gene flow. However, hybridization in Amazonia's megadiverse tree flora was assumed to be extremely rare despite extensive sympatry between closely related species, and its role in diversification remains enigmatic because it has not yet been examined empirically. Using members of a dominant Amazonian tree family (Brownea, Fabaceae) as a model to address this knowledge gap, our study recovered extensive evidence of hybridization among multiple lineages across phylogenetic scales. More specifically, using targeted sequence capture our results uncovered several historical introgression events between Brownea lineages and indicated that gene tree incongruence in Brownea is best explained by reticulation, rather than solely by incomplete lineage sorting. Furthermore, investigation of recent hybridization using ~19,000 ddRAD loci recovered a high degree of shared variation between two Brownea species that co‐occur in the Ecuadorian Amazon. Our analyses also showed that these sympatric lineages exhibit homogeneous rates of introgression among loci relative to the genome‐wide average, implying a lack of selection against hybrid genotypes and persistent hybridization. Our results demonstrate that gene flow between multiple Amazonian tree species has occurred across temporal scales, and contrasts with the prevailing view of hybridization's rarity in Amazonia. Overall, our results provide novel evidence that reticulate evolution influenced diversification in part of the Amazonian tree flora, which is the most diverse on Earth.
ISSN:0962-1083
1365-294X
DOI:10.1111/mec.15616