Department of Conservation Biology, Estación Biológica de Doñana (CSIC), Avda Américo Vespucio s/n, 41092 Sevilla, Spain Area de Ecología, Universidad Miguel Hernández, 03202 Elche, Alicante, Spain.
Conserv Biol. 2010 Oct;24(5):1230-8. doi: 10.1111/j.1523-1739.2010.01483.x.
Invasions of non-native species are one of the major causes of losses of native species. In some cases, however, non-natives may also have positive effects on native species. We investigated the potential facilitative effects of the North American red swamp crayfish (Procambarus clarkii) on the community of predators in southwestern Spain. To do so, we examined the diets of predators in the area and their population trends since introduction of the crayfish. Most predator species consumed red swamp crayfish, which sometimes occurred in over 50% of their diet samples. Moreover, the abundance of species preying on crayfish increased significantly in the area as opposed to the abundance of herbivores and to predator populations in other areas of Europe, where those predators are even considered threatened. Thus, we report the first case in which one non-native species is both beneficial because it provides prey for threatened species and detrimental because it can drive species at lower trophic levels to extinction. Increases in predator numbers that are associated with non-native species of prey, especially when some of these predators are also invasive non-natives, may increase levels of predation on other species and produce cascading effects that threaten native biota at longer temporal and larger spatial scales. Future management plans should include the complexity of interactions between invasive non-natives and the entire native community, the feasibility of successful removal of non-native species, and the potential social and economic interests in the area.
非本地物种的入侵是本地物种丧失的主要原因之一。然而，在某些情况下，非本地物种也可能对本地物种产生积极影响。我们研究了北美红沼泽小龙虾（Procambarus clarkii）对西班牙西南部捕食者群落的潜在促进作用。为此，我们检查了该地区捕食者的饮食及其自小龙虾引入以来的种群趋势。大多数捕食者物种都捕食红沼泽小龙虾，其在饮食样本中有时会占到 50%以上。此外，该地区捕食小龙虾的物种数量显著增加，而欧洲其他地区的食草动物和捕食者种群数量却在减少，在这些地区，这些捕食者甚至被认为受到威胁。因此，我们报告了首例非本地物种既有益（因为它为受威胁物种提供了猎物）又有害（因为它可能导致较低营养级别的物种灭绝）的情况。与猎物的外来物种相关的捕食者数量的增加，特别是当这些捕食者中的一些也是入侵的外来物种时，可能会增加对其他物种的捕食压力，并产生级联效应，从而威胁到更长时间和更大空间尺度上的本地生物群。未来的管理计划应包括入侵外来物种与整个本地群落之间相互作用的复杂性、成功去除非本地物种的可行性以及该地区的潜在社会和经济利益。
