Ongoing climate change is shifting the geographic distributions of some species, potentially imposing rapid changes in local community structure and ecosystem functioning. Besides changes in population level inter-specific interactions, such range shifts may also cause changes in functional structure within the host assemblages, which can result in losses or gains in ecosystem functions. Since consumer-resource dynamics are central to community regulation, functional reorganization driven by introduction of new consumer species can have large consequences on ecosystem functions. Here we experimentally examine the extent to which the recent poleward range expansion of the intertidal grazer limpet Scurria viridula along the coast of Chile has altered the role of the resident congeneric limpet S. zebrina, and whether the net collective impacts, and functional structure, of the entire herbivore guild have been modified by the introduction of this new member. We examined the functional role of Scurria species in controlling ephemeral algal cover, bare rock availability, species richness and diversity, and compared the effects in the region of range overlap against their respective 'native' abutted ranges. Experiments showed depression of per capita effects of the range-expanded species within the region of overlap, suggesting environmental conditions negatively affect individual performance. In contrast, effects of S. zebrina were commonly invariant at its range edge. When comparing single species versus polycultures, effects on bare rock cover were altered by the presence of the other Scurria species, suggesting competition between Scurria species. Importantly, although the magnitude of S. viridula effects at the range overlap was reduced, its addition to the herbivore guild seems to complement and intensify the role of the guild in reducing green algal cover, species richness and increasing bare space provision. Our study thus highlights that range expansion of an herbivore can modify the functional guild structure in the recipient community. It also highlights the complexity of predicting how functional structure may change in the face of natural or human-induced range expansions. There is a need for more field-based examination of regional functional compensation, complementarity or inhibition before we can construct a conceptual framework to anticipate the consequences of species range expansions.

中文翻译：

---

由范围扩展引起的功能冗余消费者的新出现改变了社区结构

持续的气候变化正在改变一些物种的地理分布，可能会导致当地社区结构和生态系统功能发生快速变化。除了种群水平种间相互作用的变化，这种范围的变化也可能导致宿主组合内功能结构的变化，这可能导致生态系统功能的损失或增加。由于消费者资源动态是社区监管的核心，引入新的消费者物种驱动的功能重组会对生态系统功能产生重大影响。在这里，我们实验性地研究了智利海岸最近潮间带食草动物帽贝 Scurria viridula 的极地范围扩张改变了常驻同类帽贝 S. zebrina 的作用的程度，以及净集体影响是否，引入这个新成员后，整个食草动物公会的功能结构都发生了变化。我们研究了 Scurria 物种在控制短暂藻类覆盖、裸岩可用性、物种丰富度和多样性方面的功能作用，并比较了范围重叠区域与其各自“原生”邻接范围的影响。实验表明，重叠区域内范围扩大物种的人均效应降低，表明环境条件对个体表现产生负面影响。相比之下，S. zebrina 的影响在其范围边缘通常是不变的。当比较单一物种与混养时，其他 Scurria 物种的存在改变了对裸岩覆盖的影响，表明 Scurria 物种之间存在竞争。重要的，尽管 S. viridula 对范围重叠的影响程度有所降低，但它加入食草动物协会似乎补充和加强了该协会在减少绿藻覆盖、物种丰富度和增加裸露空间方面的作用。因此，我们的研究强调，食草动物的范围扩展可以改变接受者社区的功能行会结构。它还强调了预测功能结构在面对自然或人为引起的范围扩展时如何变化的复杂性。在我们构建一个概念框架来预测物种范围扩展的后果之前，需要对区域功能补偿、互补或抑制进行更多的实地考察。它加入食草动物协会似乎补充和加强了该协会在减少绿藻覆盖、物种丰富度和增加裸露空间方面的作用。因此，我们的研究强调，食草动物的范围扩展可以改变接受者社区的功能行会结构。它还强调了预测功能结构在面对自然或人为引起的范围扩展时如何变化的复杂性。在我们构建一个概念框架来预测物种范围扩展的后果之前，需要对区域功能补偿、互补或抑制进行更多的实地考察。它加入食草动物协会似乎补充和加强了该协会在减少绿藻覆盖、物种丰富度和增加裸露空间方面的作用。因此，我们的研究强调，食草动物的范围扩展可以改变接受者社区的功能行会结构。它还强调了预测功能结构在面对自然或人为引起的范围扩展时如何变化的复杂性。在我们构建一个概念框架来预测物种范围扩展的后果之前，需要对区域功能补偿、互补或抑制进行更多的实地考察。因此，我们的研究强调，食草动物的范围扩展可以改变接受者社区的功能行会结构。它还强调了预测功能结构在面对自然或人为引起的范围扩展时如何变化的复杂性。在我们构建一个概念框架来预测物种范围扩展的后果之前，需要对区域功能补偿、互补或抑制进行更多的实地考察。因此，我们的研究强调，食草动物的范围扩展可以改变接受者社区的功能行会结构。它还强调了预测功能结构在面对自然或人为引起的范围扩展时如何变化的复杂性。在我们构建一个概念框架来预测物种范围扩展的后果之前，需要对区域功能补偿、互补或抑制进行更多的实地考察。