Article

Arendt J, Reznick D.. Convergence and parallelism reconsidered: what have we learned about the genetics of adaptation? Trends Ecol Evol 23: 26-32

Department of Biology, University of California - Riverside, 900 University Avenue, Riverside CA 92521, USA. <>
Trends in Ecology & Evolution (Impact Factor: 16.2). 02/2008; 23(1):26-32. DOI: 10.1016/j.tree.2007.09.011
Source: PubMed

ABSTRACT

Biologists often distinguish 'convergent' from 'parallel' evolution. This distinction usually assumes that when a given phenotype evolves, the underlying genetic mechanisms are different in distantly related species (convergent) but similar in closely related species (parallel). However, several examples show that the same phenotype might evolve among populations within a species by changes in different genes. Conversely, similar phenotypes might evolve in distantly related species by changes in the same gene. We thus argue that the distinction between 'convergent' and 'parallel' evolution is a false dichotomy, at best representing ends of a continuum. We can simplify our vocabulary; all instances of the independent evolution of a given phenotype can be described with a single term - convergent.

Download full-text

Full-text

Available from: Jeff Arendt
  • Source
    • "As a matter of fact, the character displacement hypothesis implies that allopatric populations of potential competitors may show convergence in niche requirements . If their parallel adaptation also lead to convergence in growth performance (approaching the same fitness peak on an adaptive landscape;Fong, Joyce &amp; Palsson 2005;Arendt &amp; Reznick 2008), they may become ecologically equivalent and, on secondary contacts, form 'neutral communities'. Here, we report an experiment that addresses how evolution of species in sympatry or allopatry affects both stabilizing and equalizing forces that determine coexistence in a microbial system. "

    Full-text · Article · Nov 2015 · Functional Ecology
  • Source
    • "This requires an in-depth knowledge of their genetic basis. A recent upsurge of interest thus centres on the question of whether or not repeated instances of phenotypic evolution or adaptations to the same environment share the same genetic basis (Elmer & Meyer 2011; Stern & Orgogozo 2009; Arendt & Reznick 2007; Jones et al. 2012; Soria-Carrasco et al. 2014). To a certain extent, this seems to be the case, even though most studies pursuing this question employed a candidate gene approach (reviewed, e.g., in Stern 2013; Gompel & Prud&apos;homme 2009). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Replicated ecological gradients are prime systems to study processes of molecular evolution underlying ecological divergence. Here, we investigated the repeated adaptation of the neotropical fish Poecilia mexicana to habitats containing toxic hydrogen sulphide (H2S) and compared two population pairs of sulphide-adapted and ancestral fish by sequencing population pools of >200 individuals (Pool-Seq). We inferred the evolutionary processes shaping divergence and tested the hypothesis of increase of parallelism from SNPs to molecular pathways. Coalescence analyses showed that the divergence occurred in the face of substantial bidirectional gene flow. Population divergence involved many short, widely dispersed regions across the genome. Analyses of allele fre- quency spectra suggest that differentiation at most loci was driven by divergent selection, followed by a selection-mediated reduction of gene flow. Reconstructing allelic state changes suggested that selection acted mainly upon de novo mutations in the sulphide-adapted populations. Using a corrected Jaccard index to quantify parallel evolution, we found a negligible proportion of statistically significant parallel evolution of Jcorr = 0.0032 at the level of SNPs, divergent genome regions (Jcorr = 0.0061) and genes therein (Jcorr = 0.0091). At the level of metabolic pathways, the overlap was Jcorr = 0.2545, indicating increasing parallelism with increasing level of biological integration. The majority of pathways contained positively selected genes in both sulphide populations. Hence, adaptation to sulphidic habitats necessitated adjustments throughout the gen- ome. The largely unique evolutionary trajectories may be explained by a high proportion of de novo mutations driving the divergence. Our findings favour Gould’s view that evolution is often the unrepeatable result of stochastic events with highly contingent effects.
    Full-text · Article · Oct 2015 · Molecular Ecology
  • Source
    • "The genetic basis of phenotypic novelty is a major unresolved question in evolutionary biology (Beldade and Brakefield 2002; Wray et al. 2003; Hahn et al. 2007; Arendt and Reznick 2008; Conant and Wolfe 2008; Stern and Orgogozo 2008). Understanding the processes that give rise to major phenotypic shifts has also generated considerable disagreement (Hoekstra and Coyne 2007; Mitchell-Olds et al. 2007; Halligan et al. 2013; Parker et al. 2014). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Whether coding or regulatory sequence change is more important to the evolution of phenotypic novelty is one of biology's major unresolved questions. The field of evo-devo has shown that in early development changes to regulatory regions are the dominant mode of genetic change, but whether this extends to the evolution of novel phenotypes in the adult organism is unclear. Here we conduct ten RNA-Seq experiments across both novel and conserved tissues in the honey bee to determine to what extent post-developmental novelty is based on changes to the coding regions of genes. We make several discoveries. First, we show that with respect to novel physiological functions in the adult animal, positively selected tissue-specific genes of high expression underlie novelty by conferring specialized cellular functions. Such genes are often, but not always taxonomically restricted genes (TRGs). We further show that positively selected genes, whether TRGs or conserved genes, are the least connected genes within gene expression networks. Overall, this work suggests that the evo-devo paradigm is limited, and that the evolution of novelty, post-development, follows additional rules. Specifically, evo-devo stresses that high network connectedness (repeated use of the same gene in many contexts) constrains coding sequence change as it would lead to negative pleiotropic effects. Here we show that in the adult animal, the converse is true: genes with low network connectedness (TRGs and tissue-specific conserved genes) underlie novel phenotypes by rapidly changing coding sequence to perform new specialized functions.
    Full-text · Article · Oct 2015 · Molecular Biology and Evolution
Show more