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Evolution of the elaborate male intromittent organ of Xiphophorus fishes
Author(s) -
Jones Julia C.,
Fruciano Carmelo,
Keller Anja,
Schartl Manfred,
Meyer Axel
Publication year - 2016
Publication title -
ecology and evolution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.17
H-Index - 63
ISSN - 2045-7758
DOI - 10.1002/ece3.2396
Subject(s) - biology , sexual selection , xiphophorus , sympatric speciation , evolutionary biology , trait , allopatric speciation , zoology , mating , natural selection , genetic algorithm , ecological speciation , ecology , selection (genetic algorithm) , gene flow , genetic variation , population , genetics , fish <actinopterygii> , fishery , demography , artificial intelligence , sociology , computer science , gene , programming language
Internally fertilizing animals show a remarkable diversity in male genital morphology that is associated with sexual selection, and these traits are thought to be evolving particularly rapidly. Male fish in some internally fertilizing species have “gonopodia,” highly modified anal fins that are putatively important for sexual selection. However, our understanding of the evolution of genital diversity remains incomplete. Contrary to the prediction that male genital traits evolve more rapidly than other traits, here we show that gonopodial traits and other nongonopodial traits exhibit similar evolutionary rates of trait change and also follow similar evolutionary models in an iconic genus of poeciliid fish ( Xiphophorus spp.). Furthermore, we find that both mating and nonmating natural selection mechanisms are unlikely to be driving the diverse Xiphophorus gonopodial morphology. Putative holdfast features of the male genital organ do not appear to be influenced by water flow, a candidate selective force in aquatic habitats. Additionally, interspecific divergence in gonopodial morphology is not significantly higher between sympatric species, than between allopatric species, suggesting that male genitals have not undergone reproductive character displacement. Slower rates of evolution in gonopodial traits compared with a subset of putatively sexually selected nongenital traits suggest that different selection mechanisms may be acting on the different trait types. Further investigations of this elaborate trait are imperative to determine whether it is ultimately an important driver of speciation.

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