Impacts of gene expression plasticity on expression evolution
A growing number of studies are using transcriptomic and proteomic
surveys to address the long-standing debate on the role of plasticity in
evolution, with contrasting results favoring the alternative hypotheses
that adaptive (Fraser et al., 2014; Gleason & Burton, 2015; Li et al.,
2018; Mäkinen, Papakostas, Vøllestad, Leder, & Primmer, 2016; Scoville
& Pfrender, 2010; Shaw et al., 2014; Wang & Althoff, 2019) versus
non-adaptive (Dayan, Crawford, & Oleksiak, 2015; Ghalambor et al.,
2015; W. Ho & Zhang, 2018; Pespeni et al., 2013; Schaum, Rost, Millar,
& Collins, 2013) plasticity facilitates adaptation. We recently
proposed that non-adaptive plasticity dominates during the earliest
stages of rapid evolution, and that adaptive plasticity may contribute
to subsequent fine-tuning of phenotypes (Fischer et al., 2016a). In line
with this prediction and our previous findings, we report here that the
strong signature of non-adaptive plasticity in brain gene expression
(89% of transcripts) observed in guppy populations in the earliest
stages of adaptation to low-predation environments (Ghalambor et al.,
2015) is present but weaker in long-established low-predation
populations. Furthermore, within our data set, this signature of
non-adaptive plasticity was more apparent in the more recently diverged
Aripo lineage (80% of genes) as compared to the older Quare lineage
(65% of genes). Our findings highlight the need to explicitly consider
how plasticity relates to divergence throughout successive stages of
adaptation in order to build a more holistic understanding of the role
of plasticity in adaptation.