Evolutionary trade-offs between heat and cold tolerance limit responses to fluctuating climates

Abstract

The evolutionary potential of species to cope with short-term temperature fluctuations during reproduction is critical to predicting responses to future climate change. Despite this, vertebrate research has focused on reproduction under high or low temperatures in relatively stable temperate climates. Here, we characterize the genetic basis of reproductive thermal tolerance to temperature fluctuations in the ostrich that lives in tropical and sub-tropical Africa. Both heat and cold tolerance are under selection and heritable, indicating that evolutionary responses to mean temperature change are possible. However, a negative, genetic correlation between heat and cold tolerance limits the potential for adaptation to fluctuating temperatures. Genetic constraints between heat and cold tolerance appears a crucial, yet underappreciated, factor influencing responses to climate change.One-sentence summaryReproductive success in fluctuating climates is constrained by a negative genetic correlation between heat and cold tolerance

Thermoregulatory consequences of growing up during a heatwave or a cold snap in Japanese quail

“…Thus, we found no evidence for a trade-off between heat-and cold-acclimation at the level of thermoregulation. While such a trade-off might be perceived as intuitive and sometimes occurs at the organismal level (Shou et al, 2022), it need not be expected on regulatory grounds where thermogenesis and thermolysis are not physiologically linked. Nonetheless, we found that coldacclimated birds had higher baseline (i.e., non-heat-induced) EWL than control birds (Fig.…”

Heritable variation in thermoregulation is associated with reproductive success in the world’s largest bird

“…Larger bodies have a higher thermal inertia and slower rate of body temperature change compared to small bodies (Bogert, 1949;Angiletta, 2009). Thermal inertia can help maintain body temperatures during cold conditions, but it can also increase physiological stress under sustained heat, jeopardising survival and reproduction (Hurley et al, 2018;Sales et al, 2018;Bourne et al, 2020;Parratt et al, 2021;Schou et al, 2021Schou et al, , 2022.…”

“…Estimating additive genetic variance in thermoregulation, and its relationship to fitness, requires measuring these traits across hundreds of individuals of known pedigree. To do this we studied a captive population of ostriches in the Klein Karoo region of South Africa, where a large number of individuals have been reared in a semi-natural environment over 25-years to produce a large nine-generation pedigree (Schou et al, 2021(Schou et al, , 2022. To quantify thermoregulation, we used thermal imaging (infrared camera technology) as this technique allows the surface temperature of hundreds of individuals to be non-invasively measured (Tattersall & Cadena, 2010).…”

“…Combining our thermal image data with daily measurements of reproductive success and pedigree information, we test: (1) if head temperatures are regulated by blood circulating around the surface of the neck (Fig. 1B), and if the neck could thus serve as a so called 'thermal radiator' as shown for other morphological traits in other animal species (Tattersall et al, 2009;Weissenböck et al, 2010;Darnell & Munguia, 2011); (2) if variation in the efficiency of head thermoregulation influences female reproductive success, which is highly sensitive to temperature (Schou et al, 2021(Schou et al, , 2022; (3) if there is genetic variation in the efficiency of head thermoregulation; and (4) if populations originating from regions with different climatic regimes have evolved different head thermoregulatory capacities.…”

“…Larger bodies have a higher thermal inertia and slower rate of body temperature change compared to small bodies (Bogert, 1949; Angiletta, 2009). Thermal inertia can help maintain body temperatures during cold conditions, but it can also increase physiological stress under sustained heat, jeopardising survival and reproduction (Hurley et al , 2018; Sales et al , 2018; Bourne et al , 2020; Parratt et al , 2021; Schou et al , 2021, 2022). Large animals are also expected to be particularly vulnerable to changing climates because their rate of adaptative evolution is potentially limited by longer generation times and lower population sizes (Cardillo et al , 2005; Atwood et al , 2020).…”