Adaptation to Temperate Environments

研究人员关注的是影响植物或动物物种入侵北美温带并持续存在的能力的因素。 向北方纬度逐渐扩展的范围应该包括两个独立的温度适应：（a）冬季寒冷的持续时间和强度，以及（B）季节事件的时间，即，使生长、发育和繁殖适应可利用的生长季节。 在这个提议中，研究人员明确测试了这两种适应北美东部和中部气候梯度的温度的相对重要性。 在关于温度如何与生物生态学相关的各种研究中，通常假设环境温度直接限制了范围扩展，并且范围扩展是由于耐寒性的适应性修改而发生的。 研究人员认为，通常会发生相反的过程：耐寒性的适应性改变发生在种群建立良好之后，以及种群的季节性发育和冬眠适应了当地的季节循环之后。研究人员将以猪笼草蚊子为模式生物，通过实验来研究这一命题;他们将检验一个具体的假设，即从墨西哥湾到加拿大的这一物种的适应性是由于影响季节性发育和冬眠时间的适应性，而不是由于影响耐寒性的适应性。这些实验对全球变暖有重要意义。 关于全球变暖的讨论仅限于气温持续时间和强度对动植物生存的直接影响。 然而，对季节性变化的适应在某些生物中可以非常迅速地进化。 当面临全球气候变化时，生物体可能不需要直接面对极端温度;相反，它们可能只是通过改变季节性生命史中重要事件的时间来逃避这些极端温度。 研究人员试图确定栖息地温度变化的直接影响是否最有可能影响动物的健康，或者季节长度的间接影响是否会影响健康并最终影响生存。

Bradshaw9806278The investigators are concerned with factors that affect the ability of plant or animal species to invade and persist in the temperate zone of North America. Range expansion into progressively more northern latitudes should involve two separate adaptations to temperature (a) to the duration and intensity of winter cold and (b) to the timing of seasonal events, i.e., the "fitting" of growth, development, and reproduction into the available growing season. In this proposal, the investigators test explicitly for the relative importance of these two sources of adaptation to temperature over the climatic gradient of eastern and central North America. In a wide variety of studies on how temperature relates to the ecology of organisms, it is usually assumed that environmental temperatures limit range expansion directly, and that range expansion occurs because of adaptive modification of cold tolerance. The investigators argue that the opposite process usually occurs: adaptive modification in cold tolerance takes place after populations are well-established and after the seasonal development and hibernation of populations has adapted to the local seasonal cycle. The investigators will pursue this proposition experimentally, using the pitcher-plant mosquito as our model organism; they will test the specific hypothesis that fitness of this species from the Gulf of Mexico to Canada is due to adaptations that affect the timing of seasonal development and hibernation and not due to adaptations that affect cold-tolerance. These experiments have important implications for global warming. Discussions ofglobal warming are limited to the direct effects of the duration and intensity of temperatures on plant and animal survival. However, adaptation to changes in seasonality can evolve very rapidly in some organisms. When facing global climate change, organisms may not need to confront the extreme temperatures directly; rather they may simply evade these extremes by modifying the timing of important events in the seasonal life history. The investigators seek to determine whether it is the direct effect of change in habitat temperature that is most likely to impact animal fitness, or whether it is the indirect effect of season length that affects fitness and, ultimately, survival.