Guélat Jérôme, Jaquiéry Julie, Berset-Brändli Laura, Pellegrini Ester, Moresi Ruben, Broquet Thomas, Hirzel Alexandre H, Perrin Nicolas
Department of Ecology and Evolution, University of Lausanne, CH-1015 Lausanne, Switzerland.
Ecology. 2008 Jul;89(7):2033-42. doi: 10.1890/07-0905.1.
Recent developments in metacommunity theory have raised awareness that processes occurring at regional scales might interfere with local dynamics and affect conditions for the local coexistence of competing species. Four main paradigms are recognized in this context (namely, neutral, patch-dynamics, species-sorting, and mass-effect), which differ according to the role assigned to ecological or life-history differences among competing species, as well as to the relative time scale of regional vs. local dynamics. We investigated the patterns of regional and local coexistence of two species of shrews (Crocidura russula and Sorex coronatus) sharing a similar diet (generalist insectivores) over four generations, in a spatially structured habitat at the altitudinal limit of their distributions. Local populations were small, and regional dynamics were strong, with high rates of extinction and recolonization. Niche analysis revealed significant habitat differentiation on a few important variables, including temperature and availability of winter resting sites. In sites suitable for both species, we found instances of local coexistence with no evidence of competitive exclusion. Patterns of temporal succession did not differ from random, with no suggestion of a colonization-competition trade-off. Altogether, our data provide support for the mass-effect paradigm, where regional coexistence is mediated by specialization on different habitat types, and local coexistence by rescue effects from source sites. The strong regional dynamics and demographic stochasticity, together with high dispersal rates, presumably contributed to mass effects by overriding local differences in specific competitive abilities.
群落理论的最新进展使人们认识到，区域尺度上发生的过程可能会干扰局部动态，并影响竞争物种在局部共存的条件。在这种情况下，有四种主要范式（即中性、斑块动态、物种分选和质量效应），它们根据竞争物种之间生态或生活史差异所起的作用，以及区域与局部动态的相对时间尺度而有所不同。我们在两种鼩鼱（赤齿鼩鼱和冠鼩鼱）分布的海拔极限处的一个空间结构化栖息地中，对它们四代的区域和局部共存模式进行了调查，这两种鼩鼱有着相似的饮食（广食性食虫动物）。局部种群规模较小，区域动态较强，灭绝和重新定殖率较高。生态位分析揭示了在一些重要变量上存在显著的栖息地分化，包括温度和冬季栖息场所的可用性。在适合这两个物种的地点，我们发现了局部共存的实例，没有竞争排斥的证据。时间演替模式与随机模式没有差异，没有显示出定殖 - 竞争权衡的迹象。总体而言，我们的数据为质量效应范式提供了支持，其中区域共存是由对不同栖息地类型的特化介导的，而局部共存是由源地的救援效应介导的。强烈的区域动态和种群统计随机性，加上高扩散率，可能通过超越特定竞争能力的局部差异而促成了质量效应。
