[Article] 其他跳蜘的捕食壓力驅動了蟻蜘擬態螞蟻


原文標題: Salticid predation as one potential driving force of ant mimicry in jumping spiders

摘要 [原文網址]

Many spiders possess myrmecomorphy, and species of the jumping spider genus Myrmarachne exhibit nearly perfect ant mimicry. Most salticids are diurnal predators with unusually high visual acuity that prey on various arthropods, including conspecifics. In this study, we tested whether predation pressure from large jumping spiders is one possible driving force of perfect ant mimicry in jumping spiders. The results showed that small non-ant-mimicking jumping spiders were readily treated as prey by large ones (no matter whether heterospecific or conspecific) and suffered high attack and mortality rates. The size difference between small and large jumping spiders significantly affected the outcomes of predatory interactions between them: the smaller the juvenile jumping spiders, the higher the predation risk from large ones. The attack and mortality rates of ant-mimicking jumping spiders were significantly lower than those of non-ant-mimicking jumping spiders, indicating that a resemblance to ants could provide protection against salticid predation. However, results of multivariate behavioural analyses showed that the responses of large jumping spiders to ants and ant-mimicking salticids differed significantly. Results of this study indicate that predation pressure from large jumping spiders might be one selection force driving the evolution of nearly perfect myrmecomorphy in spiders and other arthropods.

這篇是由東海大學卓逸民教授率領的團隊的研究,旨在討論為何蟻蜘需要擬態螞蟻。

蟻蜘的擬態這件事其實一直以來都弄不太清楚,一來是蟻蜘不是說找就找的到,二來是每隻看到的好像都不太一樣,不太確定這些東西到底是不是不同種還是多態型;以前有人認為蟻蜘擬態螞蟻是為了要吃螞蟻,也就是攻擊型擬態(aggressive mimicry),但是根據很多人的觀察發現蟻蜘似乎也不太吃螞蟻,一些相關的報告也指出跳蜘科其實是不太攻擊螞蟻;另外也有人回到防禦性擬態的範圍下,擬態螞蟻並不是跳蜘的專利,而且擬態螞蟻似乎可以獲得某種程度的保護,因此蟻蜘的擬態或許比較跟逃避天敵有關。

有研究指出跳蜘會捕食其他大量的跳蜘(好像~30%的食性)為食物,因此蟻蜘之所以模仿螞蟻,是不是為了逃避其他跳蜘的攻擊呢?

這篇研究用了三種跳蜘做實驗

多彩扭蜘 Telamonia festiva

毛垛兜跳蛛 Ptocasius strupifer 

大蟻蛛 Myrmarachne magnus

用不同的齡期與大小讓牠們互相攻擊,結果發現蟻蜘被攻擊的次數明顯比較少,因此像螞蟻應該是有用的(細節請自行參閱內文)。

這個結果十分有趣,因為在擬態的研究中通常無法確定天敵到底是誰,這個研究提供了一個方向讓我們了解捕食者有可能就是同類型的生物,但其他脊椎動物捕食者也會取食大量的螞蟻,但這些捕食者取食的螞蟻是否與被擬態的螞蟻類群相同,而這是否會造成某種程度上擬態失效,或是促進擬態的多態性,或許可以進一步的討論。

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