Sebastián-González Esther, Moleón Marcos, Gibert Jean P, Botella Francisco, Mateo-Tomás Patricia, Olea Pedro P, Guimarães Paulo R, Sánchez-Zapata José A
Ecology. 2016 Jan;97(1):95-105. doi: 10.1890/15-0212.1.
Disentangling the processes that shape the organization of ecological assemblages and its implications for species coexistence is one of the foremost challenges of ecology. Although insightful advances have recently related community composition and structure with species coexistence in mutualistic and antagonistic networks, little is known regarding other species assemblages, such as those of scavengers exploiting carrion. Here we studied seven assemblages of scavengers feeding on ungulate carcasses in mainland Spain. We used dynamical models to investigate if community composition, species richness and structure (nestedness) affect species coexistence at carcasses. Scavenging networks showed a nested pattern in sites where highly efficient, obligate scavengers (i.e., vultures) were present and a non-nested pattern everywhere else. Griffon Vulture (Gyps fulvus) and certain meso-facultative mammalian scavengers (i.e., red fox, Vulpes vulpes, and stone marten, Martes foina) were the main species contributing to nestedness. Assemblages with vultures were also the richest ones in species. Nested species-rich assemblages with vulture presence were associated with high carcass consumption rates, indicating higher interspecific competition at the local scale. However, the proportion of species stopping the consumption of carrion (as derived from the competitive dynamic model) stabilized at high richness and nestedness levels. This suggests that high species richness and nestedness may characterize scavenging networks that are robust to high levels of interspecific competition for carrion. Some facilitative interactions driven by vultures and major facultative scavengers could be behind these observations. Our findings are relevant for understanding species' coexistence in highly competitive systems.
理清塑造生态群落组织的过程及其对物种共存的影响是生态学面临的首要挑战之一。尽管最近有一些有见地的进展将群落组成和结构与互利共生和拮抗网络中的物种共存联系起来，但对于其他物种组合，如以腐肉为食的食腐动物组合，我们知之甚少。在这里，我们研究了西班牙大陆以有蹄类动物尸体为食的七个食腐动物组合。我们使用动态模型来研究群落组成、物种丰富度和结构（嵌套性）是否会影响尸体上物种的共存。食腐网络在有高效的专性食腐动物（即秃鹫）的地点呈现出嵌套模式，而在其他所有地方则呈现非嵌套模式。兀鹫（Gyps fulvus）和某些中型兼性哺乳动物食腐动物（即赤狐，Vulpes vulpes，和石貂，Martes foina）是导致嵌套性的主要物种。有秃鹫的组合在物种方面也是最丰富的。有秃鹫存在的嵌套物种丰富组合与高尸体消耗率相关，表明在局部尺度上种间竞争更高。然而，停止食用腐肉的物种比例（由竞争动态模型得出）在高丰富度和嵌套性水平上趋于稳定。这表明高物种丰富度和嵌套性可能是食腐网络的特征，这些网络对腐肉的高水平种间竞争具有鲁棒性。由秃鹫和主要兼性食腐动物驱动的一些促进性相互作用可能是这些观察结果的背后原因。我们的发现对于理解高度竞争系统中的物种共存具有重要意义。
