Diapause is not selected as a bet-hedging strategy in insects: a meta-analysis of reaction norm shapes

Abstract

1Many organisms escape from lethal climatological conditions by entering a resistant resting 2 stage called diapause, and it is essential that this strategy remains optimally timed with seasonal 3 change. Climate change therefore exerts selection pressure on traits that regulate phenology, 4 which is expected to cause the evolution of mean diapause timing, but also phenotypic 5 plasticity and bet-hedging strategies. Especially the latter as a strategy to cope with 6 unpredictability is so far little considered in the context of climate change, and it is unknown 7 whether it can readily evolve. 8Contemporary patterns of phenological strategies across a geographic range may provide 9 information about their future evolvability. We thus extracted 447 diapause reaction norms 10 from 57 studies. First, we correlated mean diapause timing with mean winter onset. Then we 11 partitioned the reaction norm variance into a temporal component (phenotypic plasticity) and 12 among-offspring variance (diversified bet-hedging) and correlated this variance composition 13 with predictability of winter onset. Contrary to our expectation, mean diapause timing 14 correlated only weakly with mean winter onset, as populations at high latitudes failed to track 15 early onsets. Variance among offspring was also limited and correlated only weakly with 16 environmental predictability, indicating little scope for bet-hedging. We conclude that 17 evolutionary constraints limit the evolvability of phenological traits in a rapidly changing 18 climate. 20Anthropogenic greenhouse gas emissions change the environment at an unprecedented rate 21

Transgenerational Plasticity and Bet-Hedging: A Framework for Reaction Norm Evolution

“…The world is simultaneously changing in climate means, variability and predictability (IPCC, 2014;Lenton et al, 2017;Bathiany et al, 2018), and there are many phenomenological studies on responses to climate change (Parmesan and Yohe, 2003;Badeck et al, 2004;Cohen et al, 2018). However, only few detailed case-studies on the mechanisms of adaptation (Nussey et al, 2005;Gienapp et al, 2013;Lane et al, 2018) exist, and one cannot assume that a matching mean timing or a high level of plasticity is always adaptive (Boutin and Lane, 2014), just like one cannot assume CBH or DBH to be an optimal solution (Simons, 2011) -but one can analyze reaction norm shapes with the proposed shape parameters to decide whether it has the potential for adaptive tracking, arithmetic mean maximization, plasticity, bet-hedging or canalization (Joschinski and Bonte, 2020).…”

Diapause and bet‐hedging strategies in insects: a meta‐analysis of reaction norm shapes

“…Data and analysis scripts are available from the Dryad Digital Repository: <http://dx.doi.org/10.5061/dryad.9kd51c5d1> (Joschinski and Bonte 2021).…”

Ecological mechanism of climate‐mediated selection in a rapidly evolving invasive species

“…It is not obvious what combination of climatic factors best represent the ‘arrival of winter’ from the point of view of an organism committing to a costly alternative developmental trajectory. For example, a recent meta‐analysis found only a weak correlation in Diptera between extrapolated date of diapause entry and winter onset as arbitrarily defined by the fifth day below 10 °C after midsummer (Joschinski & Bonte 2019). Furthermore, our previous work found that relative dates of first hard frost did not correspond to relative diapause timing between two continents in an invasive mosquito (Urbanski et al .…”

“…This correlation (cline) between latitude and the seasonal timing of diapause initiation is among the most robust biogeographic patterns known, having been documented in hundreds of arthropods (Tauber et al . 1986; Danks 1987; Joschinski & Bonte 2019), and the timing of dormancy has been implicated in rapid adaptation to ongoing climate change in a wide range of taxa (Bradshaw & Holzapfel 2001, 2007; Parmesan 2006; Lavergne et al . 2010).…”