Department of Biology, University of Victoria, Victoria, BC, V8W 2Y2, Canada.
UWA Oceans Institute and School of Biological Sciences, University of Western Australia, Crawley, WA 6009, Australia.
Ann Bot. 2024 Mar 8;133(1):61-72. doi: 10.1093/aob/mcad148.
Climate change, including gradual changes and extreme weather events, is driving widespread species losses and range shifts. These climatic changes are felt acutely in intertidal ecosystems, where many organisms live close to their thermal limits and experience the extremes of both marine and terrestrial environments. A recent series of multiyear heatwaves in the northeast Pacific Ocean might have impacted species even towards their cooler, northern range edges. Among them, the high intertidal kelp Postelsia palmaeformis has traits that could make it particularly vulnerable to climate change, but it is critically understudied.
In 2021 and 2022, we replicated in situ and aerial P. palmaeformis surveys that were conducted originally in 2006 and 2007, in order to assess the state of northern populations following recent heatwaves. Changes in P. palmaeformis distribution, extent, density and morphometrics were assessed between these two time points over three spatial scales, ranging from 250 m grid cells across the entire 167 km study region, to within grid cells and the individual patch.
We found evidence consistent with population stability at all three scales: P. palmaeformis remained present in all 250 m grid cells in the study region where it was previously found, and neither the extent within cells nor the patch density changed significantly between time points. However, there was evidence of slight distributional expansion, increased blade lengths and a shift to earlier reproductive timing.
We suggest that apparent long-term stability of P. palmaeformis might be attributable to thermal buffering near its northern range edge and from the wave-exposed coastlines it inhabits, which may have decreased the impacts of heatwaves. Our results highlight the importance of multiscale assessments when examining changes within species and populations, in addition to the importance of dispersal capability and local conditions in regulating the responses of species to climate change.
气候变化，包括渐进变化和极端天气事件，正在导致广泛的物种丧失和分布范围转移。这些气候变化在潮间带生态系统中感受最为强烈，许多生物生活在接近其热极限的地方，同时经历海洋和陆地环境的极端情况。最近在东北太平洋发生的一系列多年热浪可能已经影响到了即使在较凉爽的北部分布边缘的物种。其中，高潮间带巨藻 Postelsia palmaeformis 具有使其特别容易受到气候变化影响的特征，但它的研究严重不足。
在 2021 年和 2022 年，我们复制了最初在 2006 年和 2007 年进行的原位和航空 Postelsia palmaeformis 调查，以评估最近热浪后北部种群的状况。在这两个时间点之间，我们在三个空间尺度上评估了 P. palmaeformis 的分布、范围、密度和形态计量学的变化，范围从整个 167 公里研究区域的 250 米网格单元到网格单元内和个体斑块。
我们发现的证据与所有三个尺度上的种群稳定性一致：P. palmaeformis 仍然存在于研究区域中之前发现的所有 250 米网格单元中，并且细胞内范围和斑块密度在两个时间点之间没有显著变化。然而，有证据表明分布略有扩大、叶片长度增加以及生殖时间提前。
我们认为，P. palmaeformis 的长期稳定性可能归因于其北部分布边缘的热缓冲作用，以及它栖息的波浪暴露的海岸线，这可能减少了热浪的影响。我们的结果强调了在检查物种和种群内部变化时进行多尺度评估的重要性，以及扩散能力和局部条件在调节物种对气候变化的反应方面的重要性。
