Temperature heterogeneity correlates with intraspecific variation in physiological flexibility in a small endotherm

Abstract

Phenotypic flexibility allows individuals to reversibly modify trait values and theory predicts an individual’s relative degree of flexibility positively correlates with the environmental heterogeneity it experiences. We tested this prediction by integrating surveys of population genetic and physiological variation with thermal acclimation experiments and indices of environmental heterogeneity in the Dark-eyed Junco (Junco hyemalis) and its congeners. We combined measures of thermogenic capacity for ~300 individuals, >21,000 single nucleotide polymorphisms genotyped in 192 individuals, and laboratory acclimations replicated on five populations. We found that Junco populations: (1) differ in their thermal performance responses to temperature variation in situ; (2) exhibit intra-specific variation in their thermogenic flexibility in the laboratory that correlates with heterogeneity in their native thermal environment; and (3) harbor genetic variation that also correlates with temperature heterogeneity. These results provide comprehensive support that phenotypic flexibility corresponds with environmental heterogeneity and highlight its importance for coping with environmental change.

How thermal challenges change gene regulation in the songbird brain and gonad: Implications for sexual selection in our changing world

“…In the brain, heat exposure influenced genes regulating synaptic activity, whereas cold exposure influenced genes involved in cellular stress response, such as protein folding. Finding hot‐ and cold‐specific responses aligns with studies across a range of taxonomic groups suggesting that high and low temperatures are distinct stressors (Bellis & Denver, 2017; Sonna et al, 2002), and that variability in temperature may represent yet another selective pressure (Sheldon, 2019; Stager et al, 2021). We also found that fewer genes were differentially expressed in the cold–TNZ contrast as compared to the hot–TNZ contrast, for both the brain and the gonad, suggesting that high temperatures may impact transcriptomic responses to a greater degree than low temperatures.…”

“…In the brain, heat exposure influenced genes regulating synaptic activity, whereas cold exposure influenced genes involved in cellular stress response, such as protein folding. Finding hot-and cold-specific responses aligns with studies across a range of taxonomic groups suggesting that high and low temperatures are distinct stressors (Bellis & Denver, 2017;Sonna et al, 2002), and that variability in temperature may represent yet another selective pressure (Sheldon, 2019;Stager et al, 2021).…”

Haemosporidian infection does not alter aerobic performance in the Pink-sided Junco (Junco hyemalis mearnsi)

“…For each individual, we quantified resting metabolic rate (the minimum oxygen consumption at rest, in the dark) and summit metabolic rate (the maximum oxygen consumption under cold exposure) using open-flow respirometry. Summit metabolic rate data have been previously published (Stager et al 2021). Birds were not fasted before either measurement.…”

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

“…Previous research on vertebrates has focused on mean temperatures, rather than examining tolerance to shifts between high and low temperatures (4)(5)(6)(7)(8)(9)(10)(11). While it is clearly important to investigate the effect of mean temperatures, whether populations persist in the face of climate change depends on whether reproductive success is maintained during temperature fluctuations (12)(13)(14)(15)(16)(17)(18)(19).…”