Low potential for evolutionary rescue from climate change in a tropical fish

Abstract

Climate change is increasing global temperatures and intensifying the frequency and severity of extreme heat waves. How organisms will cope with these changes depends on their inherent thermal tolerance, acclimation capacity, and ability for evolutionary adaptation. Yet, the potential for adaptation of upper thermal tolerance in vertebrates is largely unknown. We artificially selected offspring from wild-caught zebrafish (Danio rerio) to increase (Up-selected) or decrease (Down-selected) upper thermal tolerance over six generations. Selection to increase upper thermal tolerance was also performed on warm-acclimated fish to test whether plasticity in the form of inducible warm tolerance also evolved. Upper thermal tolerance responded to selection in the predicted directions. However, compared to the control lines, the response was stronger in the Down-selected than in the Up-selected lines in which evolution toward higher upper thermal tolerance was slow (0.04 ± 0.008 °C per generation). Furthermore, the scope for plasticity resulting from warm acclimation decreased in the Up-selected lines. These results suggest the existence of a hard limit in upper thermal tolerance. Considering the rate at which global temperatures are increasing, the observed rates of adaptation and the possible hard limit in upper thermal tolerance suggest a low potential for evolutionary rescue in tropical fish living at the edge of their thermal limits.

Interindividual plasticity in metabolic and thermal tolerance traits from populations subjected to recent anthropogenic heating

“…These data suggest that the acclimation responses are largely defined by individual performance at 12°C, with individuals that have low CT max or WAM at 12°C having greater acclimation responses. Assuming a reasonable heritability for these six traits and acclimation responses, as suggested by other studies [8,22,[35][36][37][38][39], the data presented here suggest that evolution favours the maintenance of interindividual variation in both physiological performance at a specific temperature and the magnitude of acclimation response to temperature change.…”

Sex-specific ornament evolution is a consistent feature of climatic adaptation across space and time in dragonflies

“…This h 2 is similar to the estimated mean for all adult traits in animals [h 2 = 0.247 ± 0.032 ( 25 )] and smaller than the estimated mean for melanin-based traits in insects (h 2 = 0.463 ± 0.114; see SI Appendix ). Because the capacity for rapid responses to climatic warming is often limited along other phenotypic axes [e.g., physiological tolerance ( 4 , 26 , 27 )], the modest projected responses and moderate requisite heritability of male wing melanization suggest that ornament evolution could be an important component of climatic adaptation in the coming years.…”

Marine Heatwaves Exceed Cardiac Thermal Limits of Adult Sparid Fish (Diplodus capensis, Smith 1884)

“…Based on this prediction, it appears that extreme summer water temperatures (26.8-30.0 • C) may occur 6% more of the days, shifting further into the physiological "danger zone" (mean T ARR = 28.3 • C), with daily maximum temperatures of up to 30.0 • C occurring. These findings suggest that if adult D. capensis average T ARR is fixed (hard-upper cardiac limit to thermal tolerance; Morgan et al, 2021), they may not survive this scenario, as water temperatures extend beyond the average T ARR . Furthermore, they may not be able to adapt in pace with climate warming, suggesting low potential for evolutionary rescue (Doyle et al, 2011;Klerks et al, 2019;Leeuwis et al, 2021).…”