Pallarés Susana, Carbonell José Antonio, Picazo Félix, Bilton David T, Millán Andrés, Abellán Pedro
Department of Zoology, University of Seville, Seville, Spain.
Department of Ecology and Hydrology, University of Murcia, Murcia, Spain.
Insect Sci. 2025 Aug;32(4):1453-1465. doi: 10.1111/1744-7917.13466. Epub 2024 Nov 25.
Species distributed across wide elevational gradients are likely to experience local thermal adaptation and exhibit high thermal plasticity, as these gradients are characterised by steep environmental changes over short geographic distances (i.e., strong selection differentials). The prevalence of adaptive intraspecific variation in thermal tolerance with elevation remains unclear, however, particularly in freshwater taxa. We explored variation in upper and lower thermal limits and acclimation capacity among Iberian populations of adults of the widespread water beetle Agabus bipustulatus (Dytiscidae) across a 2000 m elevational gradient, from lowland to alpine areas. Since mean and extreme temperatures decline with elevation, we predicted that populations at higher elevations will show lower heat tolerance and higher cold tolerance than lowland ones. We also explored whether acclimation capacity is positively related with climatic variability across elevations. We found significant variation in thermal limits between populations of A. bipustulatus, but no evidence of local adaptation to different thermal conditions across the altitudinal gradient, as relationships between thermal limits and elevation or climatic variables were largely nonsignificant. Furthermore, plasticities of both upper and lower thermal limits were consistently low in all populations. These results suggest thermal niche conservatism in this species, likely due to gene flow counteracting the effects of divergent selection, or adaptations in other traits that buffer exposure to climate extremes. The limited adaptive potential and plasticity of thermal tolerance observed in A. bipustulatus suggest that even generalist species, distributed across wide environmental gradients, may have limited resilience to global warming.
分布在较宽海拔梯度范围内的物种很可能经历局部热适应并表现出高热可塑性，因为这些梯度的特征是在短地理距离内环境变化剧烈（即强大的选择差异）。然而，热耐受性的适应性种内变异随海拔的普遍程度仍不清楚，尤其是在淡水类群中。我们研究了广泛分布的水甲虫Agabus bipustulatus（龙虱科）成虫在从低地到高山地区2000米海拔梯度范围内伊比利亚种群的热上限和下限以及驯化能力的变化。由于平均温度和极端温度随海拔下降，我们预测高海拔种群的耐热性将低于低地种群，而耐寒性则高于低地种群。我们还探讨了驯化能力是否与不同海拔的气候变异性呈正相关。我们发现Agabus bipustulatus种群之间的热限存在显著差异，但没有证据表明在整个海拔梯度上对不同热条件存在局部适应，因为热限与海拔或气候变量之间的关系大多不显著。此外，所有种群的热上限和下限的可塑性一直都很低。这些结果表明该物种存在热生态位保守性，可能是由于基因流动抵消了趋异选择的影响，或者是其他性状的适应缓冲了极端气候暴露。在Agabus bipustulatus中观察到的热耐受性有限的适应潜力和可塑性表明，即使是分布在广泛环境梯度中的广适性物种，对全球变暖的适应能力也可能有限。
