Does evolution go where plasticity leads? New paper by Radersma et al. in Evo Letters.
20 June 2020
Tobias Uller writes:
West-Eberhard famously suggested that plasticity ‘takes the lead’ in adaptive evolution. But how can you tell if you are not there to see it happen? In a new paper in Evolution Letters, we show one way to tackle the problem. We figured that we can look for signatures of plasticity by comparing the magnitude and direction of plastic responses to the environment with how locally adapted populations differ.
The literature on plant local adaptation is full of reciprocal transplant experiments that record both plasticity and adaptive divergence. We therefore used such data to test a number of hypotheses – and here is what we found:
First, the ancestral plastic response was generally well aligned with the difference between locally adapted phenotypes, making plasticity appear to ‘take the lead’ in adaptive evolution. Or – if you prefer – the plastic response of ancestors left a signature in the locally adapted phenotypes of descendants.
Second, plastic responses were sometimes more extreme than the locally adapted phenotypes. This can give the false impression that plasticity and evolutionary adaptation oppose each other: in fact, truly maladaptive plasticity was rare.
Third, although the signature of plasticity generally persists during local adaptation, genetic evolution modified trait combinations independently of plasticity.
We learnt a lot during this study. Perhaps the most important message is that we are a long way from understanding the relationship between plasticity and evolution – largely because very few studies are actually designed to test if evolution goes where plasticity leads.
Hopefully this paper shows not just that this is a hypothesis that can be tested, but also help to clarify what kind of data that we need.