Sheridan Jennifer A, Caruso Nicholas M, Apodaca Joseph J, Rissler Leslie J
Department of Biological Sciences University of Alabama Tuscaloosa AL USA.
Division of Science Yale-N US College Singapore.
Ecol Evol. 2017 Dec 23;8(2):1316-1327. doi: 10.1002/ece3.3636. eCollection 2018 Jan.
Changes in body size and breeding phenology have been identified as two major ecological consequences of climate change, yet it remains unclear whether climate acts directly or indirectly on these variables. To better understand the relationship between climate and ecological changes, it is necessary to determine environmental predictors of both size and phenology using data from prior to the onset of rapid climate warming, and then to examine spatially explicit changes in climate, size, and phenology, not just general spatial and temporal trends. We used 100 years of natural history collection data for the wood frog, with a range >9 million km, and spatially explicit environmental data to determine the best predictors of size and phenology prior to rapid climate warming (1901-1960). We then tested how closely size and phenology changes predicted by those environmental variables reflected actual changes from 1961 to 2000. Size, phenology, and climate all changed as expected (smaller, earlier, and warmer, respectively) at broad spatial scales across the entire study range. However, while spatially explicit changes in climate variables accurately predicted changes in phenology, they did not accurately predict size changes during recent climate change (1961-2000), contrary to expectations from numerous recent studies. Our results suggest that changes in climate are directly linked to observed phenological shifts. However, the mechanisms driving observed body size changes are yet to be determined, given the less straightforward relationship between size and climate factors examined in this study. We recommend that caution be used in "space-for-time" studies where measures of a species' traits at lower latitudes or elevations are considered representative of those under future projected climate conditions. Future studies should aim to determine mechanisms driving trends in phenology and body size, as well as the impact of climate on population density, which may influence body size.
体型变化和繁殖物候被认为是气候变化的两个主要生态后果，然而气候对这些变量的影响是直接的还是间接的仍不清楚。为了更好地理解气候与生态变化之间的关系，有必要利用快速气候变暖开始之前的数据来确定体型和物候的环境预测因子，然后研究气候、体型和物候在空间上的具体变化，而不仅仅是一般的时空趋势。我们使用了100年的林蛙自然历史收集数据（范围超过900万平方公里）以及空间明确的环境数据，来确定快速气候变暖之前（1901 - 1960年）体型和物候的最佳预测因子。然后我们测试了由这些环境变量预测的体型和物候变化与1961年至2000年的实际变化的吻合程度。在整个研究范围内的广泛空间尺度上，体型、物候和气候都如预期那样发生了变化（分别是变小、提前和变暖）。然而，尽管气候变量在空间上的具体变化准确地预测了物候变化，但它们并未准确预测近期气候变化期间（1961 - 2000年）的体型变化，这与近期众多研究的预期相反。我们的结果表明，气候的变化与观察到的物候变化直接相关。然而，鉴于本研究中体型与气候因素之间的关系并非那么直接，驱动观察到的体型变化的机制尚待确定。我们建议在“空间换时间”研究中要谨慎，即在这些研究中，低纬度或低海拔地区物种特征的测量结果被视为未来预测气候条件下的代表性特征。未来的研究应旨在确定驱动物候和体型趋势的机制，以及气候对种群密度的影响，而种群密度可能会影响体型。
