Causes and evolutionary significance of genetic convergence

Department of Ecology and Evolutionary Biology, Brown University, Providence, RI 02906, USA.
Trends in Genetics (Impact Factor: 9.92). 09/2010; 26(9):400-5. DOI: 10.1016/j.tig.2010.06.005
Source: PubMed


Convergent phenotypes provide extremely valuable systems for studying the genetics of new adaptations. Accumulating studies on this topic have reported surprising cases of convergent evolution at the molecular level, ranging from gene families being recurrently recruited to identical amino acid replacements in distant lineages. Together, these different examples of genetic convergence suggest that molecular evolution is in some cases strongly constrained by a combination of limited genetic material suitable for new functions and a restricted number of substitutions that can confer specific enzymatic properties. We discuss approaches for gaining further insights into the causes of genetic convergence and their potential contribution to our understanding of how the genetic background determines the evolvability of complex organismal traits.

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Available from: Guillaume Besnard, Oct 04, 2015
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    • "The repeated evolution of similar phenotypes in response to similar selective pressures, or convergent evolution, is a pervasive evolutionary phenomenon (Schluter, 2000; McGhee, 2011; Futuyma, 2013). Major questions remain regarding the ecological and evolutionary causes of convergence, including whether convergent evolution most often results from selection toward optimality, or from constraints on design, genetic architecture or other contingencies (Maynard Smith et al., 1985; Wake, 1991; Brakefield, 2006; Christin et al., 2010; Losos, 2011). Examining the genetic basis of convergence provides insight into these questions, because we can assume selection is relatively unconstrained when similar phenotypes are produced through diverse genetic routes and, conversely, that constraints may be important when phenotypes are determined by a limited subset of possible genetic mechanisms (Miller et al., 2006; Weinreich et al., 2006; Gompel and Prud'homme, 2009; Losos, 2011; Conte et al., 2012; Feldman et al., 2012). "
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    ABSTRACT: Convergent evolution of tetrodotoxin (TTX) resistance, at both the phenotypic and genetic levels, characterizes coevolutionary arms races between amphibians and their snake predators around the world, and reveals remarkable predictability in the process of adaptation. Here we examine the repeatability of the evolution of TTX resistance in an undescribed predator–prey relationship between TTX-bearing Eastern Newts (Notophthalmus viridescens) and Eastern Hog-nosed Snakes (Heterodon platirhinos). We found that that local newts contain levels of TTX dangerous enough to dissuade most predators, and that Eastern Hog-nosed Snakes within newt range are highly resistant to TTX. In fact, these populations of Eastern Hog-nosed Snakes are so resistant to TTX that the potential for current reciprocal selection might be limited. Unlike all other cases of TTX resistance in vertebrates, H. platirhinos lacks the adaptive amino acid substitutions in the skeletal muscle sodium channel that reduce TTX binding, suggesting that physiological resistance in Eastern Hog-nosed Snakes is conferred by an alternate genetic mechanism. Thus, phenotypic convergence in this case is not due to parallel molecular evolution, indicating that there may be more than one way for this adaptation to arise, even among closely related species.
    Heredity 10/2015; DOI:10.1038/hdy.2015.73 · 3.81 Impact Factor
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    • "On the basis of genome sequences for a total of 63 evolved populations, our aim was to address the following three questions: 1) Which trait functions, genes, and/or molecular mechanisms show patterns of convergent evolution in the resistant populations and are thus potentially adaptive (cf. Christin et al. 2010; Wake et al. 2011)? 2) Are there differences in the response to different antibiotic selection intensities (e.g., low versus high concentrations of the antibiotic combination used)? 3) What is the importance and stability of the previously observed sequence amplification (Peñ a-Miller et al. 2013) during resistance evolution, especially for the newly considered high-dosage combination treatment? "
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    ABSTRACT: Evolutionary adaptation can be extremely fast, especially in response to high selection intensities. A prime example is the surge of antibiotic resistance in bacteria. The genomic underpinnings of such rapid changes may provide information on the genetic processes that enhance fast responses and the particular trait functions under selection. Here, we use experimentally evolved Escherichia coli for a detailed dissection of the genomics of rapid antibiotic resistance evolution. Our new analyses demonstrate that amplification of a sequence region containing several known antibiotic resistance genes represents a fast genomic response mechanism under high antibiotic stress, here exerted by drug combination. In particular, higher dosage of such antibiotic combinations coincided with higher copy number of the sequence region. The amplification appears to be evolutionarily costly, since amplification levels rapidly dropped after removal of the drugs. Our results suggest that amplification is a scalable process, as copy number rapidly changes in response to the selective pressure encountered. Moreover, repeated patterns of convergent evolution were found across the experimentally evolved bacterial populations, including those with lower antibiotic selection intensities. Intriguingly, convergent evolution was identified on different organizational levels, ranging from the above sequence amplification, high variant frequencies in specific genes, prevalence of individual non-synonymous mutations to the unusual repeated occurrence of a particular synonymous mutation in Glycine codons. We conclude that constrained evolutionary trajectories underlie rapid adaptation to antibiotics. Of the identified genomic changes, sequence amplification seems to represent the most potent, albeit costly genomic response mechanism to high antibiotic stress.
    Genome Biology and Evolution 05/2014; 6(6). DOI:10.1093/gbe/evu106 · 4.23 Impact Factor
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    • "In addition to the demographic and selective factors considered above, the likelihood of genetic parallelism may be influenced by various locus specific features (reviewed in: Christin et al., 2010), including the effect size of contributing loci/alleles. Although genetic changes of large effect are expected to contribute infrequently to adaptation (Fisher, 1930; Orr, 2005), potential disadvantages of largeeffect mutations are reduced when a population resides far from the optimal phenotype (Orr, 1998, 1999; Rogers et al., 2012 and references therein). "
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    ABSTRACT: Population genetic theory predicts that effective population size and gene flow can strongly influence the levels and patterns of genetic variability, and thereby also the likelihood, pace and direction of evolutionary transformations. Given that levels and patterns of genetic variability in lakes and ponds often differ from those observed in continuous marine environments, it follows that the dynamics of adaptation and evolution in freshwater habitats are also likely to differ from those in marine habitats. Here, I explore and discuss some ideas relating to the likelihood of parallel phenotypic evolution through similar (parallel) vs different (convergent) genetic changes with particular focus on freshwater isolates. I will review and discuss the available genetic data with particular focus on freshwater fish populations, and outline possible avenues for future work in which ponds and small lakes could serve as useful model systems to study genetic parallelism and convergence, as well as molecular adaptation in general. Conservation issues related to genetics of isolated pond and lake populations are also addressed.
    Journal of limnology 05/2014; 73(s1):33-45. DOI:10.4081/jlimnol.2014.805 · 1.18 Impact Factor
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