ABSTRACT

Populations within the same species range edge may experience contrasting local conditions and exhibit diverse levels of environmental tolerance. This heterogeneity within a range boundary has seldom been considered in studies forecasting the impact of anthropogenic habitat alteration and climate change on species distributions. Moreover, any ecological prediction under changing environmental conditions requires a good understanding of the combined responses of organisms to multiple stressors, in particular the effects on key life cycle stages of species. The intertidal seaweed Fucus serratus is a dominant species on northern Atlantic shores and whose southern limit is in the NW Iberian Peninsula. We examined how early developmental stages of southern-edge populations of this foundation alga responded to the combined effects of environmental stressors, including salinity and aerial and seawater temperature. Four populations from two different areas of the NW Iberian coast were considered: two populations from open shores on the northern coast and two populations from the western rias on the Atlantic coast. The study findings revealed inter-population variability in the response to heat stress, with greater survival of germlings from the northern populations than those from western rias. Environmental conditions are still more benign within western rias, under the influence of strong summer upwelling events. The results also suggest the key role of aerial thermal stress in determining the southern limit of distribution of the target species. The future of these heterogeneous edge populations from NW Iberian Peninsula depends on trends in climate change and the ability of populations to cope with these. Environmental changes may already be occurring at rates that exceed the plastic and adaptive potential of edge populations in N Spain, while the future of western rias as climate refugia for this and other foundation alga is also uncertain.

摘要

同一物种分布范围内的种群可能会经历不同的当地条件，并表现出不同程度的环境耐受性。在预测人为栖息地改变和气候变化对物种分布的影响的研究中很少考虑范围边界内的这种异质性。此外，在不断变化的环境条件下进行任何生态预测都需要很好地了解生物体对多种压力的综合反应，尤其是对物种关键生命周期阶段的影响。潮间带海藻Fucus serratus是北大西洋沿岸的优势种，其南界在伊比利亚半岛西北部。我们研究了这种基础藻类南部边缘种群的早期发育阶段如何对环境压力因素的综合影响做出反应，包括盐度、空气和海水温度。考虑了来自伊比利亚西海岸两个不同地区的四个种群：两个种群来自北部海岸的开阔海岸，两个种群来自大西洋沿岸的西部里亚斯。研究结果揭示了对热应激反应的种群间变异性，北方种群的幼苗比西方里亚斯种群的存活率更高。在强烈的夏季上升流事件的影响下，西部里亚斯的环境条件仍然更加温和。结果还表明空气热应力在确定目标物种分布的南限方面的关键作用。这些来自伊比利亚半岛西北部的异质边缘种群的未来取决于气候变化的趋势以及种群应对这些变化的能力。环境变化的发生速度可能已经超过了西班牙北部边缘种群的可塑性和适应潜力，而西里亚斯作为这种藻类和其他基础藻类的气候避难所的未来也不确定。