Environment Analysis and Management Unit "Guido Tosi Research Group", Department of Theoretical and Applied Sciences, Università degli Studi dell'Insubria, Varese, Italy.
Department of Biology, University of Antwerp, Wilrijk, Belgium.
J Anim Ecol. 2020 Jul;89(7):1559-1569. doi: 10.1111/1365-2656.13219. Epub 2020 Apr 14.
Understanding the effects of invasive alien species (IAS) on native host-parasite relationships is of importance for enhancing ecological theory and IAS management. When IAS and their parasite(s) invade a guild, the effects of interspecific resource competition and/or parasite-mediated competition can alter existing native host-parasite relationships and the dependent biological traits such as native species' behaviour. We used a natural experiment of populations of native red squirrels Sciurus vulgaris that were colonized by the alien grey squirrel Sciurus carolinensis, comparing repeated measurements of red squirrel parasite infection and personality with those taken in sites where only the native species occurred. We explored two alternative hypotheses: (a) individual differences in personality traits (activity and/or sociability) of native red squirrel positively affect the probability of macroparasite spillover and thus the likelihood to acquire the alien's parasitic helminth Strongyloides robustus; (b) the combined effects of grey squirrel presence and parasite infection result in a reduction of costly personality traits (activity and/or exploration). Using data from 323 arena tests across three experimental (native species and IAS) and three control sites (only native species), we found negative correlations between native species' activity and infection with S. robustus in the sites invaded by the alien species. Activity was also negatively correlated with infection by its native helminth Trypanoxyuris sciuri but only when grey squirrels were present, while in the red-only sites there was no relationship of T. sciuri infection with any of the personality traits. Moreover, individuals that acquired S. robustus during the study reduced their activity after infection, while this was not the case for animals that remained uninfected. Our results show that parasite-mediated competition is costly, reducing activity in individuals of the native species, and altering the native host-native parasite relationships.
了解入侵外来物种 (IAS) 对本地宿主-寄生虫关系的影响对于增强生态理论和 IAS 管理至关重要。当 IAS 及其寄生虫入侵一个类群时，种间资源竞争和/或寄生虫介导的竞争的影响可以改变现有的本地宿主-寄生虫关系以及依赖于生物特征，例如本地物种的行为。我们利用本地红松鼠 Sciurus vulgaris 种群被外来灰松鼠 Sciurus carolinensis 殖民的自然实验，比较了在只有本地物种存在的地点和那些发生的地点对红松鼠寄生虫感染和个性的重复测量。我们探索了两种替代假设：(a) 本地红松鼠个性特征（活动和/或社交性）的个体差异会积极影响宏观寄生虫溢出的概率，从而增加获得外来寄生虫 Strongyloides robustus 的可能性；(b) 灰松鼠存在和寄生虫感染的综合影响导致代价高昂的个性特征（活动和/或探索）减少。使用来自三个实验（本地物种和 IAS）和三个对照地点（只有本地物种）的 323 个竞技场测试的数据，我们发现，在被外来物种入侵的地点，本地物种的活动与感染 S. robustus 之间存在负相关关系。活动也与感染其本地寄生虫 Trypanoxyuris sciuri 呈负相关，但仅在灰松鼠存在时才如此，而在仅存在红松鼠的地点，T. sciuri 感染与任何个性特征都没有关系。此外，在研究期间获得 S. robustus 的个体在感染后活动减少，而未感染的动物则没有这种情况。我们的结果表明，寄生虫介导的竞争是有代价的，它会降低本地物种个体的活动能力，并改变本地宿主-本地寄生虫关系。
