Department of Ecology and Evolutionary Biology, Rice University, Houston, TX, 77005, USA,
Oecologia. 2013 Nov;173(3):1043-52. doi: 10.1007/s00442-013-2675-y. Epub 2013 May 14.
Climate-mediated shifts in species' phenologies are expected to alter species interactions, but predicting the consequences of this is difficult because phenological shifts may be driven by different climate factors that may or may not be correlated. Temperature could be an important factor determining effects of phenological shifts by altering species' growth rates and thereby the relative size ratios of interacting species. We tested this hypothesis by independently manipulating temperature and the relative hatching phenologies of two competing amphibian species. Relative shifts in hatching time generally altered the strength of competition, but the presence and magnitude of this effect was temperature dependent and joint effects of temperature and hatching phenology were non-additive. Species that hatched relatively early or late performed significantly better or worse, respectively, but only at higher temperatures and not at lower temperatures. As a consequence, climate-mediated shifts in hatching phenology or temperature resulted in stronger or weaker effects than expected when both factors acted in concert. Furthermore, consequences of phenological shifts were asymmetric; arriving relatively early had disproportional stronger (or weaker) effects than arriving relatively late, and this varied with species identity. However, consistent with recent theory, these seemingly idiosyncratic effects of phenological shifts could be explained by species-specific differences in growth rates across temperatures and concordant shifts in relative body size of interacting species. Our results emphasize the need to account for environmental conditions when predicting the effects of phenological shifts, and suggest that shifts in size-structured interactions can mediate the impact of climate change on natural communities.
气候引起的物候变化预计会改变物种间的相互作用，但预测这种变化的后果是困难的，因为物候变化可能是由不同的气候因素驱动的，这些因素可能相关，也可能不相关。温度可能是通过改变物种的生长率从而改变相互作用的物种的相对体型比来决定物候变化影响的一个重要因素。我们通过独立操纵两种竞争两栖物种的温度和相对孵化物候来检验这一假设。相对孵化时间的变化通常会改变竞争的强度，但这种效应的存在和大小取决于温度，并且温度和孵化物候的联合效应是非加性的。相对较早或较晚孵化的物种表现得更好或更差，但仅在较高温度下，而不是在较低温度下。因此，当两个因素协同作用时，孵化物候或温度引起的气候介导的物候变化的影响比预期的更强或更弱。此外，物候变化的后果是不对称的；相对较早到达的物种会产生不成比例的更强（或更弱）的影响，而相对较晚到达的物种则不会，而且这种影响因物种身份而异。然而，与最近的理论一致，这些物候变化的看似特殊的影响可以通过物种在不同温度下的生长率差异以及相互作用的物种的相对体型的一致变化来解释。我们的研究结果强调了在预测物候变化的影响时需要考虑环境条件，并表明大小结构相互作用的变化可以调节气候变化对自然群落的影响。
