Abstract

How an invader responds to the novel biotic elements of a new community will affect its ability to invade. Species that are able to cope well with novel competitors might be expected to achieve greater establishment success. We compared the population-level responses of two mosquitofish species, the widespread invader Gambusia affinis and non-invasive G. geiseri to competition from each other and a non-invasive competitor. We simulated the invasion of a simplified pond community by introducing different combinations of the Gambusia spp. into communities already inhabited by a novel competitor, the red shiner Cyprenella lutrensis. We measured the effect of competition on establishment success by comparing population abundances achieved by each Gambusia species in all treatments, and examined whether the invasive and non-invasive Gambusia differed in their community impact by comparing their effects on the abundances of pond fauna. We also used N and C stable isotope analysis to compare their trophic roles. Both novel and intrageneric competition negatively affected both Gambusia spp.’s abundances, but the invasive G. affinis managed to remain more abundant than G. geiseri regardless of competition treatment. Stable isotope analysis revealed the Gambusia spp. to have similar trophic placement and showed competition to cause significant trophic shifts only in G. geiseri. A cascading effect (reduced phytoplankton abundances) was detected only when G. affinis was present. These results suggest that a higher vulnerability to novel competition along with life history traits contributes to the limited spread of G. geiseri in comparison to the widespread G. affinis.

中文翻译：

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建立成功，竞争对策以及侵入性和非侵入性Gambbusia物种的社区影响的比较

摘要

入侵者如何应对新社区的新生物元素将影响其入侵能力。能够应对新竞争者的物种有望获得更大的成功。我们比较了两种蚊鱼物种在数量级响应，广泛侵略者食蚊鱼和非侵入性G. geiseri从彼此和非侵入性的竞争对手竞争。我们通过引入Gambusia spp的不同组合来模拟简化池塘社区的入侵。进入一个已经由新型竞争者红光夜蛾Cyprnella lutrensis居住的社区。我们通过比较各种处理中的每个无形菌物种的种群数量来衡量竞争对建立成功的影响，并通过比较它们对池塘动物种群数量的影响，来检查侵入性和非侵入性无脊椎动物在社区影响方面是否有所不同。我们还使用了N和C稳定同位素分析来比较它们的营养作用。新颖的竞争和内部竞争都对Gambusia spp。的丰富度产生负面影响，但是无论采用何种竞争处理方式，侵入性G. affinis都比Ge。geiseri丰富。稳定的同位素分析显示了弹响症spp。具有相似的营养定位，并显示竞争导致仅在Geiseri菌中引起明显的营养转移。仅当存在链球菌时才检测到级联效应（浮游植物丰度降低）。这些结果表明，与广泛存在的链球菌相比，对新竞争以及生活史特征的较高易感性导致了Ge。geiseri的传播有限。