Selection towards different adaptive optima drove the early diversification of locomotor phenotypes in the radiation of Neotropical geophagine cichlids

BMC Evolutionary Biology

Research Article

Jessica H Arbour¹  Viviana Astudillo-Clavijo¹  Hernán López-Fernández² 

[1] Department of Ecology and Evolutionary Biology, University of Toronto, 25 Wilcocks St, M5S 3B2, Toronto, Ontario, Canada;Department of Ecology and Evolutionary Biology, University of Toronto, 25 Wilcocks St, M5S 3B2, Toronto, Ontario, Canada;Department of Natural History, Royal Ontario Museum, 100 Queen’s Park, M5S 2C6, Toronto, Ontario, Canada;

关键词: Cichlid;    Locomotor morphology;    Adaptive landscape;    Adaptive peak;    Early burst;    Functional diversity;    Comparative methods;   

DOI  :  10.1186/s12862-015-0348-7

 received in 2014-09-25, accepted in 2015-04-13,  发布年份 2015

来源: Springer

【 摘 要 】

BackgroundSimpson envisaged a conceptual model of adaptive radiation in which lineages diversify into “adaptive zones” within a macroevolutionary adaptive landscape. However, only a handful of studies have empirically investigated this adaptive landscape and its consequences for our interpretation of the underlying mechanisms of phenotypic evolution. In fish radiations the evolution of locomotor phenotypes may represent an important dimension of ecomorphological diversification given the implications of locomotion for feeding and habitat use. Neotropical geophagine cichlids represent a newly identified adaptive radiation and provide a useful system for studying patterns of locomotor diversification and the implications of selective constraints on phenotypic divergence in general.ResultsWe use multivariate ordination, models of phenotypic evolution and posterior predictive approaches to investigate the macroevolutionary adaptive landscape and test for evidence of early divergence of locomotor phenotypes in Geophagini. The evolution of locomotor phenotypes was characterized by selection towards at least two distinct adaptive peaks and the early divergence of modern morphological disparity. One adaptive peak included the benthic and epibenthic invertivores and was characterized by fishes with deep, laterally compressed bodies that optimize precise, slow-swimming manoeuvres. The second adaptive peak resulted from a shift in adaptive optima in the species-rich ram-feeding/rheophilic Crenicichla-Teleocichla clade and was characterized by species with streamlined bodies that optimize fast starts and rapid manoeuvres. Evolutionary models and posterior predictive approaches favoured an early shift to a new adaptive peak over decreasing rates of evolution as the underlying process driving the early divergence of locomotor phenotypes.ConclusionsThe influence of multiple adaptive peaks on the divergence of locomotor phenotypes in Geophagini is compatible with the expectations of an ecologically driven adaptive radiation. This study confirms that the diversification of locomotor phenotypes represents an important dimension of phenotypic evolution in the geophagine adaptive radiation. It also suggests that the commonly observed early burst of phenotypic evolution during adaptive radiations may be better explained by the concentration of shifts to new adaptive peaks deep in the phylogeny rather than overall decreasing rates of evolution.

【 授权许可】

CC BY   
© Astudillo-Clavijo et al.; licensee BioMed Central. 2015