Plasticity, diversified bet-hedging, and robustness: what does it mean to be unstable?

Sanjana Venkatesh and Alexander G Little

Department of Biology, McMaster University, Canada

Plasticity and diversified bet-hedging (DBH) are strategies that arguably invoke instability by design to promote phenotypic flexibility in early development. Canalization and robustness, on the other hand, represent buffering against early environmental inputs and developmental noise to promote genetically fixed traits. While often thought to stem from mutually distinct underlying processes, we propose that these strategies may be more mechanistically linked than previously considered. Here, we review the literature to highlight potential mechanistic overlaps between developmental plasticity, DBH and robustness. We also use clonal lines of starlet anemones, Nematostella vectensis, to empirically test whether inter- and intra-genotype variability in early development reflects interactions between plasticity, DBH and robustness. For instance, we predict that diversified bet-hedging may itself represent a developmentally plastic strategy, where some genotypes promote more stochastic developmental trajectories in uncertain environments. We also predict that genotypes may bet-hedge in uncertain environments by deploying stochastic variability in the capacity for plasticity. Isogenic lines of Nematostella are an ideal system to test these questions because the development of individual genotypes can be repeated many times both within and across developmental treatments. Differences in canalization and robustness can thereby provide comparative developmental contexts not possible in most animal models. Understanding robustness and canalization of plastic and DBH strategies is crucial to interpret how population mean trait values respond to environmental perturbations and test whether plasticity carries intrinsic costs.