A stringent test of the thermal coadaptation hypothesis in flour beetles

Halliday, William D.; Blouin‐Demers, Gabriel

doi:10.1016/j.jtherbio.2015.06.002

Cited by 12 publications

(6 citation statements)

References 54 publications

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“…Since T in equation is explicitly linked to the shape of the thermal reaction norm for fitness, predictions may vary slightly depending on which metric is used to estimate fitness. Although according to the thermal coadaptation hypothesis (Bennett, ; Blouin‐Demers, Weatherhead & McCracken, ; Halliday & Blouin‐Demers, ) all thermal reaction norms closely related to fitness should have similar shapes with similar optima, differences in the rate of change from critical thermal minimum to the optimal temperature could lead to different predictions when comparing habitats that differ in just a few degrees, such as our 25 and 30°C treatments. Future work could examine other fitness‐density functions and their ability at predicting habitat selection.…”

Section: Discussionmentioning

confidence: 99%

“…Environmental temperature is a major component of habitat suitability for ectotherms due to the powerful effects temperature exerts on all aspects of their biology (Huey, ; Blouin‐Demers & Weatherhead, ; Huey & Berrigan, ; Deutsch et al ., ; Lelièvre et al ., ; Amarasekare & Savage, ). For example in ectotherms several important processes are maximized within a narrow range of body temperatures (termed the optimal temperatures), including locomotion (Stevenson, Peterson & Tsuji, ; Blouin‐Demers & Weatherhead, ; Halliday & Blouin‐Demers, ), growth rate (Angilletta, Steury & Sears, ), energy acquisition (Bergman, ), energy assimilation (Stevenson et al ., ; Angilletta, ) and reproductive output (Berger, Walters & Gotthard, ; Halliday & Blouin‐Demers, ; Halliday & Blouin‐Demers, ; Halliday, Thomas & Blouin‐Demers, ). Moreover, temperature can modulate the density dependence of fitness, where negative density dependence is strongest at the optimal temperature and weakens as temperature deviates from the optimal temperature (Halliday & Blouin‐Demers, ; Halliday et al ., ).…”

Section: Introductionmentioning

confidence: 99%

“…If the thermal reaction norm for fitness is unknown, then proximate measures of fitness, such as fecundity, can be used to estimate the impact of temperature on fitness due to the coadaptation of thermal reaction norms for traits related to fitness (Halliday & Blouin‐Demers, ). We assume that neither R Ti nor U Ti are linear; they should follow the general shape of the thermal reaction norm for fitness in the species: a gradual increase as temperature approaches T o followed by a sharp decrease as temperature increases above T o (Angilletta, ; Bulté & Blouin‐Demers, ; Halliday & Blouin‐Demers, ). Thus, as temperature deviates from T o , fitness decreases and negative density dependence of fitness weakens (Halliday et al ., ).…”

Section: Introductionmentioning

confidence: 99%

“…Briefly, fitness was the per capita number of eggs laid over 4 days by red flour beetles at five density treatments (10, 20, 30, 40 and 50 beetles), two food treatments (0.625 and 2.5 mL of wheat flour) and three temperature treatments (20, 25 and 30°C). In red flour beetles, T o = 30°C according to multiple measures of fitness (Halliday & Blouin‐Demers, ; Halliday & Blouin‐Demers, ; Halliday et al ., ). We opted to use egg laying rate as our metric of fitness because it is easy to measure and is correlated with the number of adult offspring produced, which is a more ultimate measure of fitness (rho = 0.42 and 0.49 at 25 and 30°C, respectively, between the number of eggs laid and the number of adult offspring produced from data in Halliday et al ., ).…”

Section: Introductionmentioning

confidence: 99%

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Can temperature modify the strength of density‐dependent habitat selection in ectotherms? A test with red flour beetles

Halliday

Blouin‐Demers

2017

Journal of Zoology

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Habitat selection is an important aspect of the ecology of animals and models predict that density dependence is a strong force shaping patterns of habitat selection. In ectotherms, however, density dependence of fitness tends to weaken as temperature deviates from the species’ optimal temperature (To). This may have important implications for density‐dependent habitat selection because the underlying mechanism for density‐dependent habitat selection is density dependence in fitness. We examine how temperature can modify the predictions from isodar theory and obtain temperature‐dependent predictions for density‐dependent habitat selection. We specifically predict that the isodar's intercept will be furthest from zero and the slope will be steepest at the optimal temperature. As temperature deviates from the optimal temperature, we predict that the intercept will approach zero and the slope will approach one. We then test these predictions with experiments on habitat selection based on food abundance by red flour beetles in the laboratory. We also confirm that fitness decreases as density increases and that density dependence weakens as temperature deviates from To. In agreement with our predictions, preference for habitats with more food weakened as density dependence weakened. Our results have implications for habitat selection by ectotherms because we demonstrate that variation in environmental temperature can weaken markedly the effect of density on both fitness and habitat selection. High density may entail no fitness costs for ectotherms that cannot maintain their optimal temperature.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Can temperature modify the strength of density‐dependent habitat selection in ectotherms? A test with red flour beetles

Halliday

Blouin‐Demers

2017

Journal of Zoology

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“…; Blouin‐Demers et al. ; Halliday & Blouin‐Demers ), which suggests that the ability of individuals to find and handle food can also be optimized within a narrow range of temperatures. Moreover, the intensity of intraspecific competition in ectotherms can be temperature dependent (Halliday & Blouin‐Demers ; Halliday et al.…”

Section: Introductionmentioning

confidence: 99%

Density‐Dependent Foraging and Interference Competition by Common Gartersnakes are Temperature Dependent

Halliday

Blouin‐Demers

2016

Ethology

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The ideal free distribution (IFD) predicts that optimal foragers will select foraging patches to maximize food rewards and that groups of foragers should thus be distributed between food patches in proportion to the availability of food in those patches. Because many of the underlying mechanisms of foraging are temperature dependent in ectotherms, the distribution of ectothermic foragers between food patches may similarly depend on temperature because the difference in fitness rewards between these patches may change with temperature. We tested the hypothesis that the distribution of Common Gartersnakes (Thamnophis sirtalis) between food patches can be explained by an IFD, but that conformance to an IFD weakens as temperature departs from the optimal temperature because fitness rewards, interference competition and the number of individuals foraging are highest at the optimal temperature. First, we determined the optimal temperature for foraging. Second, we examined group foraging at three temperatures and three density treatments. Search time was optimized at 27°C, handling time at 29°C and digestion time at 32°C. Gartersnakes did not match an IFD at any temperature, but their distribution did change with temperature: snakes at 20°C and at 30°C selected both food patches equally, while snakes at 25°C selected the low food patch more at low density and the high food patch more at high density. Food consumption and competition increased with temperature, and handling time decreased with temperature. Temperature therefore had a strong impact on foraging, but did not affect the IFD. Future work should examine temperature‐dependent foraging in ectotherms that are known to match an IFD.

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