Walter Greg M, Chakraborty Avishikta, Cockerell Fiona E, Kellermann Vanessa M, Hall Matthew D, White Craig R, Sgrò Carla M
School of Natural Sciences, University of Tasmania, Hobart, Tasmania, Australia.
School of Biological Sciences, Monash University, Melbourne, Victoria, Australia.
Proc Biol Sci. 2025 Sep;292(2054):20251337. doi: 10.1098/rspb.2025.1337. Epub 2025 Sep 3.
Latitudinal clines are routinely used as evidence of adaptation across broad climatic gradients. However, if environmental variation influences the strength of latitudinal clines, then clinal patterns will be unstable, and using patterns of adaptation to predict population responses to global change will be difficult. To test whether environmental variation influences latitudinal clines, we sampled five populations of spanning 3000 km of east coast Australia, and measured stress tolerance (heat, cold and desiccation) and body size on flies that developed in six combinations of temperature (13°C, 25°C and 29°C) and diet (standard and low-calorie) treatments. We found latitudinal clines where populations further from the equator had larger wings, higher cold tolerance and lower heat tolerance. For all traits, temperature determined the strength of latitudinal clines, whereas diet had little influence. Steeper clines often emerged in warmer treatments, created by latitudinal clines in plasticity. In the warmest temperature, higher latitude populations showed larger increases in heat tolerance, larger reductions in desiccation tolerance but smaller decreases in cold tolerance. Heat tolerance was the only trait that supported the climate variability hypothesis and a trade-off between plasticity and tolerance. Environment-dependent latitudinal clines are therefore likely to determine variation in population responses to global change.
纬度渐变群经常被用作在广泛气候梯度上适应的证据。然而，如果环境变化影响纬度渐变群的强度，那么渐变模式将不稳定，并且利用适应模式来预测种群对全球变化的反应将变得困难。为了测试环境变化是否影响纬度渐变群，我们对澳大利亚东海岸绵延3000公里的五个种群进行了采样，并在六种温度（13°C、25°C和29°C）与饮食（标准和低热量）处理组合下发育的果蝇上测量了应激耐受性（热、冷和干燥）和体型。我们发现了纬度渐变群，其中离赤道较远的种群翅膀更大、耐寒性更高且耐热性更低。对于所有性状，温度决定了纬度渐变群的强度，而饮食影响很小。在较温暖的处理中，由于可塑性的纬度渐变，往往会出现更陡峭的渐变。在最温暖的温度下，高纬度种群的耐热性增加幅度更大，干燥耐受性降低幅度更大，但耐寒性降低幅度更小。耐热性是唯一支持气候变异性假说以及可塑性与耐受性之间权衡的性状。因此，依赖环境的纬度渐变群可能决定了种群对全球变化反应的差异。
