Kersch-Becker Mônica F, Grisolia Bruno B, Campos Maria J O, Romero Gustavo Q
Department of Animal Biology, University of Campinas (UNICAMP), Campinas, SP, 13083-970, Brazil.
Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL, 35487, USA.
Oecologia. 2018 Sep;188(1):213-222. doi: 10.1007/s00442-018-4170-y. Epub 2018 Jun 4.
The strength and outcome of mutualistic interactions can be highly dependent on the combination of traits of the species involved. Distinct foraging strategies (e.g., hunting mode) of mutualistic predators may cause predator-prey interactions to vary, potentially affecting the strength of trophic cascades. We evaluate the causes of variation in the strength of spider-plant mutualisms by focusing on contrasting hunting modes of two spiders: an actively hunting lynx spider (Peucetia sp.) and a sit-and-wait crab spider (Misumenops argenteus). We manipulated spider species composition by assigning each plant to one of the following treatments: (1) no spiders; (2) sit-and-wait spiders only; (3) actively hunting spiders only; (4) actively hunting + sit-and-wait spiders. We then examined the independent and interactive effects of spider species on floral herbivory and fitness of the glandular trichome-bearing plant, Trichogoniopsis adenantha (Asteraceae). Both spider species increased plant fitness by suppressing herbivores and increasing ovary fertilization, but the overall net benefit of spiders was contingent on spider hunting mode. Sit-and-wait spiders promoted stronger positive cascading effects compared to actively hunting spiders. The combination of spider species suppressed herbivores in an additive manner; their combined impact on plant fitness, however, was lower than expected, suggesting that the inter-specific interaction between spiders is slightly antagonistic. Thus, both spider species combined weakened the strength of this spider-plant mutualism. Our findings offer a general framework for understanding the critical role of predator foraging mode in trophic cascades.
互利共生相互作用的强度和结果可能高度依赖于所涉及物种的性状组合。互利共生捕食者不同的觅食策略（如捕猎方式）可能导致捕食者与猎物之间的相互作用发生变化，进而可能影响营养级联的强度。我们通过关注两种蜘蛛截然不同的捕猎方式来评估蜘蛛与植物互利共生强度变化的原因：一种是积极捕猎的猞猁蛛（Peucetia sp.）和一种坐等型的蟹蛛（Misumenops argenteus）。我们通过将每株植物分配到以下处理之一来操纵蜘蛛物种组成：（1）无蜘蛛；（2）仅坐等型蜘蛛；（3）仅积极捕猎型蜘蛛；（4）积极捕猎型 + 坐等型蜘蛛。然后，我们研究了蜘蛛物种对具腺毛植物Trichogoniopsis adenantha（菊科）的花部食草动物和适合度的独立和交互作用。两种蜘蛛都通过抑制食草动物和增加子房受精来提高植物适合度，但蜘蛛的总体净效益取决于蜘蛛的捕猎方式。与积极捕猎型蜘蛛相比，坐等型蜘蛛促进了更强的正向级联效应。蜘蛛物种的组合以累加方式抑制了食草动物；然而，它们对植物适合度的综合影响低于预期，这表明蜘蛛之间的种间相互作用略有拮抗。因此，两种蜘蛛组合削弱了这种蜘蛛与植物互利共生的强度。我们的研究结果为理解捕食者觅食方式在营养级联中的关键作用提供了一个总体框架。
