Parallel molecular evolution in an herbivore community.
Ying Zhen*,†, Matthew L. Aardema*, Edgar M. Medina#, Molly Schumer* and Peter Andolfatto*,†
*Department of Ecology and Evolutionary Biology and the †Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA.
#Departamento de Ciencias Biológicas, Universidad de los Andes, Bogotá, Colombia.
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Abstract
Numerous insects have independently evolved the ability to feed on plants that produce toxic secondary compounds called cardenolides and can sequester these compounds for use in their defense. We survey the protein target for cardenolides, Na+,K+-ATPase (ATPa), in 14 species that feed on cardenolide-producing plants and 15 outgroups spanning three insect orders. Despite the large number of potential targets for modulating cardenolide sensitivity, amino acid substitutions associated with hostplant specialization are highly clustered, with many parallel substitutions. Additionally, we document four independent duplications of ATPa with convergent tissue-specific expression patterns. We find that unique substitutions are disproportionately associated with recent duplications relative to parallel substitutions. Together, these findings support the notion that adaptive evolution is governed by a preference for evolutionary paths that minimize negative pleiotropy.
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