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511.
Devin L. Johnson Michael T. Henderson Alastair Franke George J. F. Swan Robbie A. McDonald David L. Anderson Travis L. Booms Cory T. Williams 《Ecology and evolution》2023,13(1):e9709
- Stable isotope mixing models (SIMMs) are widely used for characterizing wild animal diets. Such models rely upon using accurate trophic discrimination factors (TDFs) to account for the digestion, incorporation, and assimilation of food. Existing methods to calculate TDFs rely on controlled feeding trials that are time-consuming, often impractical for the study taxon, and may not reflect natural variability of TDFs present in wild populations.
- We present TDFCAM as an alternative approach to estimating TDFs in wild populations, by using high-precision diet estimates from a secondary methodological source—in this case nest cameras—in lieu of controlled feeding trials, and provide a framework for how and when it should be applied.
- In this study, we evaluate the TDFCAM approach in three datasets gathered on wild raptor nestlings (gyrfalcons Falco rusticolus; peregrine falcons Falco perigrinus; common buzzards Buteo buteo) comprising contemporaneous δ13C & δ15N stable isotope data and high-quality nest camera dietary data. We formulate Bayesian SIMMs (BSIMMs) incorporating TDFs from TDFCAM and analyze their agreement with nest camera data, comparing model performance with those based on other relevant TDFs. Additionally, we perform sensitivity analyses to characterize TDFCAM variability, and identify ecological and physiological factors contributing to that variability in wild populations.
- Across species and tissue types, BSIMMs incorporating a TDFCAM outperformed any other TDF tested, producing reliable population-level estimates of diet composition. We demonstrate that applying this approach even with a relatively low sample size (n < 10 individuals) produced more accurate estimates of trophic discrimination than a controlled feeding study conducted on the same species. Between-individual variability in TDFCAM estimates for ∆13C & ∆15 N increased with analytical imprecision in the source dietary data (nest cameras) but was also explained by natural variables in the study population (e.g., nestling nutritional/growth status and dietary composition).
- TDFCAM is an effective method of estimating trophic discrimination in wild animal populations. Here, we use nest cameras as source dietary data, but this approach is applicable to any high-accuracy method of measuring diet, so long as diet can be monitored over an interval contemporaneous with a tissue's isotopic turnover rate.
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Timothy J. Greives Susannah S. French Devin A. Zysling Nicholas W. Garcia Gregory E. Demas 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2010,180(2):267-277
Seasonal variation in behavior and physiology, including changes in immune function, are common. This variability is elicited
by changes in photoperiod and often covaries with fluctuations in both energy reserves and reproductive state. It is unclear,
however, whether changes in either variable alone drive seasonal changes in immunity. We investigated the relative contributions
of reproduction and energy balance to changes in immune function. To accomplish this, we uncoupled seasonal changes in reproduction
from those related to energy balance via daily injections of N-methyl-d-aspartate (NMDA) in Siberian hamsters (Phodopus sungorus). NMDA is a glutamatergic agonist that blocks short day-induced gonadal regression, while leaving short-day declines in body
mass unaffected. In Experiment 1, we examined the effect of differing doses of NMDA on testosterone production as a proxy
for NMDA effects on reproduction; a dose-dependent rise in testosterone was observed. In Experiment 2, animals were maintained
on long or short days and received daily injections of NMDA. After 8 weeks, all animals underwent a humoral immune challenge.
Short-day animals receiving daily injections of NMDA maintained long day-like gonads; however, contrary to our predictions,
no trade-off between reproduction or energy balance and immune function was observed. Unexpectedly, NMDA treatment increased
immunoglobulin levels in all groups, suggesting that NMDA may provide an immunomodulatory signal, presumably through actions
on peripheral glutamate receptors. These results support a previous finding that NMDA blocks reproductive regression. In addition,
these findings demonstrate a general immunoenhancing effect of NMDA that appears independent of changes in reproductive or
energetic state of the animal. 相似文献
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Fish biogeography in the “Lost World” of the Guiana Shield: Phylogeography of the weakly electric knifefish Gymnotus carapo (Teleostei: Gymnotidae) 下载免费PDF全文
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