Department of Ecology and Evolutionary Biology, University of Toronto, 25 Harbord Street, Toronto, Ontario M5S 3G5, Canada.
Ecology. 2010 Feb;91(2):431-40. doi: 10.1890/09-0099.1.
Climate change is expected to alter patterns of species co-occurrence, in both space and time. Species-specific shifts in reproductive phenology may alter the assemblages of plant species in flower at any given time during the growing season. Temporal overlap in the flowering periods (co-flowering) of animal-pollinated species may influence reproductive success if competitive or facilitative interactions between plant species affect pollinator services. We used a 33-year data set on flowering phenology in subalpine meadows in Colorado, USA, to determine whether interannual variation in snowmelt date, which marks the start of the growing season, affected co-flowering patterns. For two of four species considered, we found a significant relationship between snowmelt timing and composition of the assemblage of co-flowering plants. In years of early snowmelt, Lathyrus lanszwertii var. leucanthus (Fabaceae), the species we investigated in most detail, tended to overlap with earlier-flowering species and with fewer species overall. In particular, overlap with the flowering period of Lupinus polyphyllus var. prunophilus, with which Lathyrus leucanthus shares pollinators, was significantly reduced in early-snowmelt years. The observed association between timing of snowmelt and patterns of flowering overlap could not have been predicted simply by examining temporal trends in the dates of peak flowering of the dominant species in the community, as peak flowering dates have largely shifted in parallel with respect to snowmelt date. However, subtle interspecific differences in responsiveness of flowering time, duration, and intensity to interannual climate variation have likely contributed to the observed relationship. Although much of the year-to-year variation in flowering overlap remains unexplained by snowmelt date, our finding of a measurable signal of climate variation suggests that future climate change may lead to altered competitive environments for these wildflower species.
预计气候变化将改变物种共存的模式，无论是在空间上还是时间上。物种特有繁殖物候期的变化可能会改变在生长季节的任何特定时间开花的植物物种组合。传粉动物物种开花期（共同开花）的时间重叠如果植物物种之间的竞争或促进作用影响传粉者服务，可能会影响繁殖成功。我们使用了美国科罗拉多州亚高山草甸 33 年的开花物候数据，以确定雪融日期（标志着生长季节开始）的年际变化是否会影响共同开花模式。对于我们考虑的四个物种中的两个，我们发现雪融时间与共同开花植物组合的组成之间存在显著关系。在雪融较早的年份中，Lathyrus lanszwertii var. leucanthus（豆科），我们研究最详细的物种，往往与更早开花的物种重叠，总体上与较少的物种重叠。特别是，与 Lathyrus leucanthus 共享传粉者的 Lupinus polyphyllus var. prunophilus 的开花期重叠在雪融较早的年份中显著减少。雪融时间与开花重叠模式之间的观察到的关联不能仅仅通过检查群落中优势物种的开花高峰期日期的时间趋势来预测，因为开花高峰期日期已经在很大程度上与雪融日期平行变化。然而，开花时间、持续时间和强度对年际气候变化的响应的细微种间差异可能促成了观察到的关系。尽管开花重叠的大部分年际变化仍无法用雪融日期来解释，但我们发现气候变化的可测量信号表明，未来的气候变化可能会改变这些野花物种的竞争环境。
