Madliger Christine L, Love Oliver P
Department of Biological Sciences , University of Windsor , 401 Sunset Avenue , Windsor , Ontario , Canada N9B 3P4.
Department of Biological Sciences, University of Windsor, 401 Sunset Avenue, Windsor, Ontario, CanadaN9B 3P4; Great Lakes Institute for Environmental Research, University of Windsor, 401 Sunset Avenue, Windsor, Ontario, CanadaN9B 3P4.
Conserv Physiol. 2016 Oct 15;4(1):cow048. doi: 10.1093/conphys/cow048. eCollection 2016.
Labile physiological variables, such as stress hormones [i.e. glucocorticoids (GCs)], allow individuals to react to perturbations in their environment and may therefore reflect the effect of disturbances or positive conservation initiatives in advance of population-level demographic measures. Although the application of GCs as conservation biomarkers has been of extensive interest, few studies have explicitly investigated whether baseline GC concentrations respond to disturbances consistently across individuals. However, confirmation of consistent responses is of paramount importance to assessing the ease of use of GCs in natural systems and to making valid interpretations regarding population-level change (or lack of change) in GC concentrations. We investigated whether free-ranging female tree swallows () display individually specific changes in baseline glucocorticoid concentrations naturally over the breeding season (from incubation to offspring provisioning) and in response to a manipulation of foraging profitability (representing a decrease in access to food resources). We show that baseline GC concentrations are repeatable within individuals over reproduction in natural conditions. However, in response to a reduction in foraging ability, baseline GC concentrations increase at the population level but are not repeatable within individuals, indicating a high level of within-individual variation. Overall, we suggest that baseline GCs measured on a subset of individuals may not provide a representative indication of responses to environmental change at the population level, and multiple within-individual measures may be necessary to determine the fitness correlates of GC concentrations. Further validation should be completed across a variety of taxa and life-history stages. Moving beyond a traditional cross-sectional approach by incorporating repeated-measures methods will be necessary to assess the suitability of baseline GCs as biomarkers of environmental change and population persistence, particularly from a logistical and ease-of-use perspective for conservation managers.
不稳定的生理变量，如应激激素[即糖皮质激素（GCs）]，使个体能够对环境扰动做出反应，因此可能在种群水平的人口统计学指标之前反映干扰或积极保护举措的影响。尽管将GCs用作保护生物标志物备受广泛关注，但很少有研究明确调查基线GC浓度在个体间对干扰的反应是否一致。然而，确认一致的反应对于评估GCs在自然系统中的易用性以及对GC浓度的种群水平变化（或缺乏变化）做出有效解释至关重要。我们调查了自由放养的雌性树燕（）在繁殖季节（从孵化到育雏）自然状态下以及对觅食收益操纵（代表食物资源获取减少）的反应中，基线糖皮质激素浓度是否表现出个体特异性变化。我们发现，在自然条件下，个体在繁殖过程中基线GC浓度具有重复性。然而，在觅食能力下降时，基线GC浓度在种群水平上升高，但在个体内不具有重复性，这表明个体内存在高度变异性。总体而言，我们认为对一部分个体测量的基线GCs可能无法代表种群水平对环境变化的反应，可能需要多次个体内测量来确定GC浓度与适应性的相关性。应在各种分类群和生活史阶段完成进一步验证。超越传统的横断面方法，采用重复测量方法对于评估基线GCs作为环境变化和种群持续性生物标志物的适用性是必要的，特别是从保护管理者的后勤和易用性角度来看。
