Mutualism, hybrid inviability and speciation in a tropical ant-plant

Although biotic interactions are particularly intricate in the tropics, few studies have examined whether divergent adaptations to biotic interactions lead to speciation in tropical organisms. Ant-plant mutualisms are widespread in the tropics. Within Leonardoxa africana, two subspecies present cont...

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Bibliographic Details
Published in:Journal of evolutionary biology 2008-07, Vol.21 (4), p.1133-1143
Main Authors: LÉOTARD, G, SALTMARSH, A, KJELLBERG, F, MCKEY, D
Format: Article
Language:English
Subjects:
Adaptation
Animals
Ants - physiology
Botany
Cameroon
ecological speciation
Evolutionary biology
Fabaceae - classification
Fabaceae - genetics
Fabaceae - growth & development
Fabaceae - physiology
Formicidae
Genetic Speciation
Genetics
Hybridization
Hybridization, Genetic - genetics
Insects
Leonardoxa
Microsatellite Repeats - genetics
null alleles
Phenotype
plant defences
rain forests
rainforest
Symbiosis - physiology
sympatry
Tropical Climate
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Summary:Although biotic interactions are particularly intricate in the tropics, few studies have examined whether divergent adaptations to biotic interactions lead to speciation in tropical organisms. Ant-plant mutualisms are widespread in the tropics. Within Leonardoxa africana, two subspecies present contrasting defences against herbivores. Young leaves of subsp. africana are defended by mutualistic ants, whereas subsp. gracilicaulis satiates herbivores by synchronized leaf production. Subsp. africana possesses hollow internodes and many large foliar nectaries, housing and feeding ants. We detected no genetic introgression between the two subspecies in the contact zone between them. F1 hybrids were present. They were intermediate in phenotype, expressing reduced, nonfunctional but costly myrmecophilic traits. However, they suffered more herbivory than their parents. Hybrids remained small, failing to reach reproductive size, probably due to their maladapted defence phenotype. Hence, there could be a direct link between adaptation to mutualism and reproductive isolation: biotic interactions could be a driver of tropical diversity.
ISSN:1010-061X
1420-9101
DOI:10.1111/j.1420-9101.2008.01521.x