Data from: Conflict between biotic and climatic selective pressures acting on an extended phenotype in a subarctic, but not temperate, environment

Climatic selective pressures are thought to dominate biotic selective pressures at higher latitudes. However, few studies have experimentally tested how these selective pressures differentially act on traits across latitudes because traits can rarely be manipulated independently of the organism in nature. We overcame this challenge by using an extended phenotype—active bird nests—and conducted reciprocal transplant experiments between a subarctic and temperate site, separated by 14° of latitude. At the subarctic site, biotic selective pressures (nest predation) favoured smaller, non-local temperate nests, whereas climatic selective pressures (temperature) favoured larger local nests, particularly at colder temperatures. By contrast, at the temperate site, climatic and biotic selective pressures acted similarly on temperate and subarctic nests. Our results illustrate a functional trade-off in the subarctic between nest morphologies favoured by biotic versus climatic selective pressures, with climate favouring local nest morphologies. At our temperate site, however, allocative trade-offs in the time and effort devoted to nest construction favour smaller, local nests. Our findings illustrate a conflict between biotic and climatic selective pressures at the northern extremes of a species geographical range, and suggest that trade-offs between trait function and trait elaboration act differentially across latitude to create broad geographic variation in traits.学界普遍认为，在高纬度地区，气候选择压力相较于生物选择压力占据主导地位。然而，鲜有研究通过实验探究这两类选择压力如何沿纬度梯度对性状产生差异化作用——这是因为在自然环境中，性状很难脱离生物体本身被独立操控。本研究通过利用拓展表型（extended phenotype）——活动鸟巢——克服了这一难题，并在纬度间隔14°的亚北极与温带两个样地间开展了互易移植实验。在亚北极样地，生物选择压力（巢捕食作用）倾向于选择更小的非本地温带鸟巢，而气候选择压力（温度）则青睐更大的本地鸟巢，这一效应在温度更低的环境中尤为显著。与之形成对比的是，在温带样地，气候与生物选择压力对温带与亚北极鸟巢的作用效果并无显著差异。本研究结果表明，在亚北极地区，生物与气候选择压力所青睐的鸟巢形态间存在功能权衡：气候选择压力更青睐本地鸟巢形态。而在温带样地，受限于筑巢所需的时间与精力分配权衡，当地种群更倾向于构建更小的本地鸟巢。本研究结果揭示了物种分布范围最北端区域内，生物与气候选择压力间的冲突，并表明性状功能与性状特化之间的权衡会沿纬度梯度产生差异化作用，最终造就了性状的广泛地理变异。