STUDY ON DISRUPTIVE SELECTION CAUSEING SPECIATION IN COMPLEX PREDATOR-PREY SYSTEMS

我们从多个行为学角度研究了自然界中复杂的捕食者-食饵系统的影响因素。首先，我们分析了目标物种的系统发育，发现相关物种是单系进化的。接下来是几种捕食者和捕食者在实验条件下的行为特征。例如，长裂殖吸虫大而连续的巢有利于协同防御，因为许多成虫长期集中在一起，尽管这些巢因其大小而相对容易受到捕食者的入侵。另一方面，由一只裂尾线虫雌虫重复建造的较小的、分散的巢(最多10个卵)是防止几种捕食者入侵的坚实避难所。除了上述功能外，我们发现，散落的鸟巢一旦遭到捕食，就会起到欺骗捕食者的“假人”作用。此外，在检测到巢后，它们中的大多数应该入侵巢中寻找和捕食卵。也就是说，我们指出，这些分散的空巢增加了捕食者的搜索成本(时间)，并在遭受捕食后起到了欺骗捕食者的假人的作用。因此，我们可以得出结论，这种捕食压力可能是一种破坏性的选择压力，导致了火绒鱼物种群的物种形成。在小甲虫和蚂蚁中，我们还揭示了几个相关的现象，并确定了它们的系统发育。这些成果以13份报告的形式编写，其中4份报告已被接受或出版。目前的结果有力地表明，具有不同特征的多个捕食者的捕食压力有时是导致被捕食物种通过破坏性选择形成物种的非常强大的因素。

We studied on the factors which caused complex predator-prey systems in the nature from several behavioral view points. First we analyzed the phylogenies of the target species focused on and revealed that the species concerned are monophyletic. Next the behavioral traits of several prey and predator species under experimental conditions. For example, the function of the large and continuous nests of Schizotetranychus longus Saito was beneficial to cooperative defense through the concentration of many adults over a long period, although the nests are relatively vulnerable to predatory intrusion because of their large sizes. On the other hand, the smaller, scattered nests (with at most ten eggs) constructed repeatedly by a single Schizotetranychus celarius Banks female were solid refuges that can prevent several predator species from intruding. In addition to the above function, we found that once scattered nests have suffered predation, they then function as "dummies" to delude predators. Furthermore, most of them should invade the nests to search for and feed on eggs after nest detection. Namely, we indicated that these scattered void nests increase a predators searching cost (time), then function as "dummies for deluding predators" after suffering predation. Therefore, we could conclude that such predation pressure might operate as a disruptive selection pressure which caused the speciation of the celarius species group. In small beetles and ants, we also revealed several related phenomena and determined the phylogeny of them. These results have been prepared as 13 reports of which 4 reports had been accepted or published. The other 9 are now under submission.Then, the present results strongly suggest that the predation pressure by multiple predators having various traits sometimes operate as very strong factors which cause the speciation of prey species through disruptive selection.