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Individual variation in energetics, environment, and genetics can influence population-level processes. However, it is often assumed that locally measured thermal and bioenergetic responses apply among broadly related species. Even closely related taxa may differ in the thermal sensitivity of performance, which in turn influences population persistence, population vital rates, and the ability to respond to environmental changes. The objectives of this project were to quantify the thermal sensitivity of digestive physiology in an Sceloporus lizards, to compare closely related, but geographically distinct, populations. Sceloporus lizards are a model organism, as they are known to exhibit thermally dependent physiologies and are geographically widespread. Digestive passage time, food consumption, fecal and urate production, metabolizable energy intake (MEI), and assimilated energy (AE) were compared for Sceloporus consobrinus in Arkansas and S. undulatus in South Carolina and New Jersey. Published data were acquired for NJ and SC lizards, while original data were collected for S. consobrinus. Comparisons of digestion among populations were made at 30 ◦C, 33 ◦C, or 36 ◦C. Results suggest that digestive physiology differs among populations, with S. consobrinus being more efficient at warmer temperatures. In contrast, NJ and SC lizards had quicker passage times and lower fecal and urate production at 30 ◦C in comparison to AR. The results of the current study exemplify how closely related organisms can differ in thermal sensitivity of performance. Such data are important for understanding how individual-level processes can vary in response to climate, with implications for understanding variation in physiological traits across the range of Sceloporus lizards.
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Population‐level variation of digestive physiology costs of mounting an immune response in damselflies
1. Trade‐offs are often predicted to occur between energetically costly activities, such as somatic growth and eliciting immune responses to parasites. Although parasitism frequently reduces growth via lowered consumption, it remains unclear if the energetic demands of generating immune responses also affect the digestive physiological processes necessary for growth. Moreover, as local environmental conditions affect energetic investment towards growth and immune responses, the extent of any digestive–immune response trade‐offs may vary among populations and not be fixed at the species‐level. 2. To test these ideas, melanisation – a general innate immune response – was first induced in damselfly larvae (Enallagma vesperum) from two populations. The study then quantified growth and consumption rates, assimilation and production efficiencies, and daily metabolic rates to determine if digestive–immune response trade‐offs were present and, if so, whether they differed between populations. 3. There was no evidence of any trade‐offs between immune responses and digestive physiology components in either population. However, the results did show that populations differentially allocated energy towards different digestive physiology components after an immune response was elicited: one population increased their relative consumption and daily metabolic rates, while the other population had lower assimilation efficiencies and consumption rates. 4. Although researchers lack a mechanistic understanding of the observed population‐level differences, these results suggest that accounting for population‐level variation in digestive physiology and immune responses is critical to inferences about how immunological defences to parasitism may affect the ability for organisms to both acquire and utilise resources.
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- PAR ID:
- 10457757
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Ecological Entomology
- Volume:
- 45
- Issue:
- 3
- ISSN:
- 0307-6946
- Format(s):
- Medium: X Size: p. 635-643
- Size(s):
- p. 635-643
- Sponsoring Org:
- National Science Foundation
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