Exploring Temperature Mediated Interspecific Competition & Predation as a Mechanism of Elevation Range Limits

温度被认为是影响生物地理分布的主要环境因素之一。然而令人费解的是，一个物种能够生存的温度范围，也就是它的耐热性，通常要大于它们所处地理区域的温度范围。解释这种差异的一个常见假设是，物种之间的相互作用，如竞争、捕食和寄生，限制了生物可以占据的环境范围。这对恒温动物（冷血动物）尤其重要，因为体温、生理功能、行为和性能都是由环境温度决定的。因此，当热耐受性不同的物种相遇时，温度可能间接影响物种的相互作用。因此，温度可能间接影响生活在不同温度制度地区的生态群落中哪些物种会聚集在一起，但这些影响是如何起作用的尚不清楚。研究人员试图通过测试温度对温带和热带水生昆虫群落中竞争和捕食相互作用的影响来解决这个问题。这项工作将测试长期存在的生态问题，即温度如何直接影响物种相互作用的结果，并间接影响地理范围边界和群落组成。研究人员的目的是研究竞争和捕食是如何独立地和与温度相互作用来解释海拔范围大小的变化的。首先，将通过实验模拟向上和向下的海拔范围扩展，测试温度如何独立和共同影响近亲间种间竞争的结果。其次，将采用类似的实验室方法来观察在高海拔和低海拔地区发现的常见石蝇捕食蜉蝣的结果。这些实验将在重复控制的实验室环境中进行，使用来自美国科罗拉多州（温带）和厄瓜多尔Papallacta（热带）的亲缘关系密切的贝伊德蜉蝣。鉴于温带蜉蝣具有相似的广泛的热耐受性，物种之间的不对称竞争或对石蝇捕食的不同脆弱性预计会限制海拔范围的向上或向下扩展。相比之下，“局部适应”的热带蜉蝣预计将被限制在各自的范围内，因为它们的热耐受性很窄，而且任何生物相互作用都预计会加剧在其原生范围外温度下性能下降的影响。

Temperature is thought to be one of the main environmental factors shaping the geographic distributions of organisms. Yet puzzlingly, the range of temperatures a species can survive, called its thermal tolerance, is often greater than the range of temperatures found across the geographic areas they occupy. A common hypothesis to explain this discrepancy is that species interactions like competition, predation and parasitism constrain the range of environments organisms can occupy. This may be particularly important for ectothermic animals (cold blooded animals), because body temperature, physiological function, behavior, and performance are determined by environmental temperatures. Therefore, temperature may indirectly influence species interactions when species that differ in their thermal tolerance meet. As a result temperature could indirectly influence which species are found together in ecological communities living in regions with different temperature regimes, but how these influences work is not yet well understood. The researchers seek to address this question by testing the effect of temperature on competitive and predatory interactions, in temperate and tropical communities of aquatic insects. This work will test long-standing ecological questions on how temperature directly shapes the outcome of species interactions, and indirectly shapes geographic range boundaries and community composition. The researchers aim to investigate how competition and predation, independently and in interactions with temperature, explain variation in elevation range size. First, upward and downward elevation range expansions will be experimentally simulated by testing how temperature independently and jointly influences the outcome of interspecific competition between close mayfly relatives. Second, a similar laboratory approach will be employed to look at the outcome of predation of mayflies by common stonefly predators found at high and low elevations. These experiments will be carried out in a replicated controlled laboratory setting, using closely related Baetid mayflies from Colorado, USA (temperate), and from Papallacta, Ecuador (tropical). Given the similar, broad thermal tolerances of temperate mayflies, either asymmetric competition between species or differential vulnerability to predation by stoneflies is predicted to limit upward or downward expansion of elevation ranges. In contrast, the "locally adapted" tropical mayflies are predicted to be restricted to their respective ranges because of their narrow thermal tolerances, and any biotic interactions are predicted to exacerbate the effects of reduced performance at temperatures outside their native range.