Stress hormone receptors change as range expansion progresses in house sparrows

As ranges expand, individuals encounter different environments at the periphery than at the centre of the range. Previously, we have shown that glucocorticoids (GCs) vary with range expansion: individuals at the range edge release more GCs in response to restraint. Here, we measured hippocampal mRNA expression of GC receptors (mineralocorticoid, MR and glucocorticoid, GR) in eight house sparrow (Passer domesticus) populations varying in age. We found that individuals closest to the range edge had the lowest expression of MR relative to GR; in all likelihood, this relationship was driven by a marginal reduction of MR mRNA at the range edge. Reduced MR (relative to GR) might allow enhanced GC binding to GR, the lower affinity receptor that would enhance a rapid physiological and behavioural response to stressors. The insights gained from this study are not only enlightening to introduced species, but may also predict how certain species will react as their ranges shift owing to anthropoge...

随着物种分布范围持续扩张，个体在分布范围外围所遭遇的环境与中心区域存在显著差异。此前本团队的研究已证实，糖皮质激素（glucocorticoids, GCs）的水平会随分布范围扩张发生动态变化：分布范围边缘的个体在受到束缚应激时，会释放更多的GCs。本研究针对8个拓殖时长各异的家麻雀（Passer domesticus）种群，检测了其海马体中两类糖皮质激素受体——盐皮质激素受体（mineralocorticoid, MR）与糖皮质激素受体（glucocorticoid, GR）——的mRNA表达水平。研究结果显示，距离分布范围边缘越近的个体，其MR相较于GR的表达水平越低；该关联大概率由分布范围边缘处MR mRNA水平的小幅下调所驱动。相较于GR，MR表达水平的降低或许可增强GCs与GR的结合能力：GR作为低亲和力受体，其介导的应激生理与行为响应会更为迅速。本研究获得的见解不仅可为外来引入物种的相关研究提供新思路，或还可预测部分物种在因anthropoge（原文未完整拼写）导致其分布范围变迁时的响应模式。