| 英文摘要: | 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. |