Underappreciated Consequences of Phenotypic Plasticity for Ecological Speciation

Abstract

Phenotypic plasticity was once seen primarily as a constraint on adaptive evolution or merely a nuisance by geneticists. However, some biologists promote plasticity as a source of novelty and a factor in evolution on par with mutation, drift, gene flow, and selection. These claims are controversial and largely untested, but progress has been made on more modest questions about effects of plasticity on local adaptation (the first component of ecological speciation). Adaptive phenotypic plasticity can be a buffer against divergent selection. It can also facilitate colonization of new niches and rapid divergent evolution. The influence of nonadaptive plasticity has been underappreciated. Non-adaptive plasticity, too can interact with selection to promote or inhibit genetic differentiation. Finally, phenotypic plasticity of reproductive characters might directly influence evolution of reproductive isolation (the second component of ecological speciation). Plasticity can cause assortative mating, but its influence on gene flow ultimately depends on maintenance of environmental similarity between parents and offspring. Examples of plasticity influencing mating and habitat choice suggest that this, too, might be an underappreciated factor in speciation. Plasticity is an important consideration for studies of speciation in nature, and this topic promises fertile ground for integrating developmental biology with ecology and evolution.

Island colonisation and the evolutionary rates of body size in insular neonate snakes

“…Body size shifts were nevertheless shown to occur rapidly (that is, from a few decades up to several thousands of years) following colonisation in mammals (Millien, 2006), birds (Mathys and Lockwood, 2011) and reptiles (Aubret and Shine, 2007;Herrel et al, 2008). Further, although many forms of plastic responses, including altered behaviours, feeding strategies and defence mechanisms, were invoked in the successful colonisation of new environments (including islands; Ehrlich, 1989;Stearns, 1989;Via et al, 1995;Holway and Suarez, 1999;Pigliucci and Murren, 2003;West-Eberhard, 2003;Aubret et al, 2004a, b;Yeh and Price, 2004;Fitzpatrick, 2012), the idea that adaptive plasticity may also alter rates of evolution remains very much debated, perhaps because empirical support is scarce (Hinton and Nowlan, 1987;Ancel, 2000;Price et al, 2003;Yeh and Price, 2004;Borenstein et al, 2006;Anderson et al, 2012).…”

Effects of dispersal plasticity on population divergence and speciation

“…However, as Thibert-Plante and Hendry (2011) and Fitzpatrick (2012) point out, we have explored little of the evolutionary consequences of this plasticity. Different theoretical models seem to reach different conclusions about whether plasticity in the decision to disperse increases or decreases population divergence relative to random dispersal.…”

“…Several recent reviews highlight the role of phenotypic plasticity in promoting population divergence and speciation (Schlichting, 2004;Grether, 2005;Crispo, 2007;Ghalambor et al, 2007;Fitzpatrick, 2012). The growing interest in phenotypic plasticity reflects the general shift from an assumption that plasticity always inhibits evolutionary change (summarized in Schlichting and Pigliucci, 1998) to one that plasticity can accelerate change (Schlichting and Pigliucci, 1998;West-Eberhard, 1989, 2003.…”

“…Finally, following local adaptation, does plasticity affect mate choice (for example, Price et al, 2003;Craig et al, 2005;Edelaar et al, 2008;Deere et al, 2012) thus promoting speciation (for example, Edelaar et al, 2008;Havens and Etges, 2013)? However, as Thibert-Plante and Hendry (2011) and Fitzpatrick (2012) have pointed out, the start of this process, which is migration to the new habitat, has been largely neglected. These authors emphasize how timing of dispersal can interact with plasticity to enhance or limit population divergence.…”

“…Finally, I discuss potential approaches for testing the effects dispersal plasticity. Because effects of timing in dispersal have been considered in detail elsewhere (Thibert-Plante and Hendry, 2011;Fitzpatrick, 2012), I confine my discussion to plasticity in whether to disperse and where to settle only. leave the natal patch, movement between patches and the decision on where to settle (Lidicker and Stenseth, 1992).…”