Meeting Abstract

36.8  Thursday, Jan. 5  Developmental plasticity and the origin of novel forms: Unveiling of cryptic genetic variation via ‘use and disuse’ PALMER, A. Richard; University of Alberta rich.palmer@ualberta.ca

Natural selection eliminates phenotypic variation from populations, generation after generation … an observation that haunted Darwin. So, how does new phenotypic variation arise, and is it always random with respect to fitness? Repeated behavioral responses to a novel environment — particularly those that are learned — are typically advantageous. If those behaviors yield more extreme or novel morphological variants via developmental plasticity, then previously cryptic genetic variation may be exposed to natural selection. Significantly, because the mean phenotypic effect of ‘use and disuse’ is also typically favorable, previously cryptic genetic variation can be transformed into phenotypic variation that is both visible to selection and biased in an adaptive direction. Therefore, use-induced developmental plasticity in a real sense “creates” new phenotypic variation that is non-random with respect to fitness, in contrast to the random phenotypic effects of mutation, recombination and ‘direct effects’ of environment (stress, nutrition). Furthermore, intermediate levels of developmental plasticity may enhance the ‘detection’ of cryptic genetic variation in organisms the same way that intermediate levels of noise enhances signal detection in signal-detection systems via ‘stochastic resonance’. I will present a) a simple, general model illustrating how cryptic genetic variation may be exposed to selection by developmentally plastic responses that alter trait performance in response to ‘use and disuse’, and b) a more detailed model of, and evidence for, a positive feedback loop between learning (handed behavior) and morphological plasticity (use-induced morphological asymmetry) that may rapidly generate novel, functionally and evolutionarily significant phenotypic variation.