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     In class we most recently discussed how phenotypes may be lost or gained over time, the potential role of genetic accommodation in shaping genotypes, and how plasticity may be another driver in natural selection through adaptation. I looked into this a little further and found two different theories of adaptive evolution pertaining to phenotypic plasticity. These were described as "gene leading" and "gene following" approaches by Ghalambor and colleagues. Gene leading is the typical thought of evolution as the process of change in allele frequencies over time, which would shape traits that are plastic and environmentally induced variation is not heritable and actually slows the rate of adaptive evolution. Gene following is the idea that environmentally induced and weak genetic control of phenotypic variation becomes established in a population and results in genetic assimilation of a trait so that the need for environmental cues are not required. 

    The later approach argues that environmentally induced phenotypic plasticity can result in genetic changes over time. This got me wondering about an interesting variation in reproduction strategies of mole salamanders (Ambystoma talpoideum) where Atlantic coastal plain populations lay their eggs singly under vegetation in a pond while Gulf coast populations lay them in small masses around twigs. Dean Croshaw found that  A. talpoideum eggs had higher rates of mortality when touching other conspecific eggs. Furthermore, mortality of eggs increased if neighboring eggs were dead vs. neighboring eggs being alive. This is likely a result of water molds transferring from one egg to another.  I bring this example up because I wonder if this difference in reproductive strategy may be a result of traits that were once plastic across the species' range and has now become conserved along with genetic distinctions between the Atlantic and Gulf coast populations. 


GHALAMBOR, C.K., McKAY, J.K., CARROLL, S.P. and REZNICK, D.N. (2007), Adaptive versus non‐adaptive phenotypic plasticity and the potential for contemporary adaptation in new environments. Functional Ecology, 21: 394-407

Singly laid mole salamander (Ambystoma talpoideum) eggs resist mortality from water mold infection Author(s): Dean A. Croshaw Source: Behaviour , 2014, Vol. 151, No. 1 (2014), pp. 125-136

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