Sato Yukie, Alba Juan M, Egas Martijn, Sabelis Maurice W
Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, P.O. Box 94240, 1090GE, Amsterdam, Netherlands.
Sugadaira Montane Research Center, University of Tsukuba, Ueda, Nagano, 386-2204, Japan.
Exp Appl Acarol. 2016 Nov;70(3):261-274. doi: 10.1007/s10493-016-0079-5. Epub 2016 Aug 9.
When competing with indigenous species, invasive species face a problem, because they typically start with a few colonizers. Evidently, some species succeeded, begging an answer to the question how they invade. Here, we investigate how the invasive spider mite Tetranychus evansi interacts with the indigenous species T. urticae when sharing the solanaceous host plant tomato: do they choose to live together or to avoid each other's colonies? Both species spin protective, silken webs on the leaf surfaces, under which they live in groups of con- and possibly heterospecifics. In Spain, T. evansi invaded the non-crop field where native Tetranychus species including T. urticae dominated. Moreover, T. evansi outcompetes T. urticae when released together on a tomato plant. However, molecular plant studies suggest that T. urticae benefits from the local down-regulation of tomato plant defences by T. evansi, whereas T. evansi suffers from the induction of these defences by T. urticae. Therefore, we hypothesize that T. evansi avoids leaves infested with T. urticae whereas T. urticae prefers leaves infested by T. evansi. Using wild-type tomato and a mutant lacking jasmonate-mediated anti-herbivore defences, we tested the hypothesis and found that T. evansi avoided sharing webs with T. urticae in favour of a web with conspecifics, whereas T. urticae more frequently chose to share webs with T. evansi than with conspecifics. Also, T. evansi shows higher aggregation on a tomato plant than T. urticae, irrespective of whether the mites occur on the plant together or not.
在与本土物种竞争时，入侵物种面临一个问题，因为它们通常最初只有少数几个殖民者。显然，有些物种成功了，这就引出了它们如何入侵的问题。在这里，我们研究入侵性叶螨二斑叶螨（Tetranychus evansi）与本土物种普通叶螨（T. urticae）在共享茄科寄主植物番茄时是如何相互作用的：它们是选择一起生活还是避开彼此的群体？这两个物种都会在叶面上结出保护性的丝质网，它们在网下成群生活，可能是同种或异种群体。在西班牙，二斑叶螨侵入了非农田，那里包括普通叶螨在内的本土叶螨物种占主导地位。此外，当二斑叶螨和普通叶螨一起被放置在番茄植株上时，二斑叶螨会胜过普通叶螨。然而，分子植物研究表明，普通叶螨受益于二斑叶螨对番茄植株防御的局部下调，而二斑叶螨则受到普通叶螨诱导这些防御的影响。因此，我们假设二斑叶螨会避开被普通叶螨侵染的叶子，而普通叶螨更喜欢被二斑叶螨侵染的叶子。我们使用野生型番茄和一个缺乏茉莉酸介导的抗食草动物防御的突变体来检验这个假设，结果发现二斑叶螨会避开与普通叶螨共享蛛网，而倾向于与同种叶螨共享蛛网，而普通叶螨更频繁地选择与二斑叶螨共享蛛网，而不是与同种叶螨共享。此外，无论叶螨是否一起出现在植株上，二斑叶螨在番茄植株上的聚集程度都比普通叶螨更高。
