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Mutualism, hybrid inviability and speciation in a tropical ant–plant
Author(s) -
LÉOTARD G.,
SALTMARSH A.,
KJELLBERG F.,
MCKEY D.
Publication year - 2008
Publication title -
journal of evolutionary biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.289
H-Index - 128
eISSN - 1420-9101
pISSN - 1010-061X
DOI - 10.1111/j.1420-9101.2008.01521.x
Subject(s) - biology , mutualism (biology) , herbivore , myrmecophyte , ecology , introgression , reproductive isolation , nectar , incipient speciation , subspecies , adaptation (eye) , hybrid zone , coevolution , hybrid , botany , genetic variation , gene flow , population , gene , pollen , biochemistry , demography , neuroscience , sociology
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.