Lack of phenological shift leads to increased camouflage mismatch in mountain hares

Understanding whether organisms will be able to adapt to human-induced
stressors currently endangering their existence is an urgent priority.
Globally, multiple species moult from a dark summer to white winter coat
to maintain camouflage against snowy landscapes. Decreasing snow cover
duration due to climate change is increasing mismatch in seasonal
camouflage. To directly test for adaptive responses to recent changes in
snow cover, we repeated historical (1950s) field studies of moult
phenology in mountain hares (Lepus timidus) in Scotland. We found little
evidence that population moult phenology has shifted to align seasonal
coat colour with shorter snow seasons, or that phenotypic plasticity
prevented increases in camouflage mismatch. The lack of responses resulted
in 35 additional days of mismatch between 1950 and 2016. We emphasize the
potential role of weak directional selection pressure and low genetic
variability in shaping the scope for adaptive responses to anthropogenic
stressors.

探明生物能否适应当前威胁其生存的人为诱导胁迫因子（human-induced stressors），是一项亟待解决的核心议题。全球范围内，诸多物种会在夏季拥有深色被毛，冬季换为白色被毛，以此在积雪景观中维持保护色（camouflage）伪装。气候变化导致的积雪覆盖时长缩减，正不断加剧季节性保护色错配问题。为直接验证物种对积雪覆盖近期变化的适应性响应，我们重复开展了1950年代针对苏格兰山地野兔（*Lepus timidus*）换毛物候（moult phenology）的历史性野外研究。研究发现，几乎没有证据表明种群换毛物候发生了偏移，以让季节性被毛颜色与更短的积雪季相匹配；也没有证据显示表型可塑性（phenotypic plasticity）能够抑制保护色错配程度的加剧。1950年至2016年间，这种无适应性响应的状况导致错配天数额外增加了35天。本研究着重指出，较弱的定向选择压力与低遗传变异性，可能是制约物种对人为胁迫因子（anthropogenic stressors）产生适应性响应的关键潜在因素。