Ineffective crypsis in a crab spider: a prey community perspective
Ineffective crypsis in a crab spider: a prey community perspective
复制标题
DOI：
10.1098/rspb.2009.1632
复制
发表时间：
2010-03-07
影响因子：
4.7
通讯作者：
Bacher, Sven
中科院分区：
文献类型：
--
作者：
Brechbuehl, Rolf;Casas, Jerome;Bacher, Sven
隐秘的颜色被认为对捕食者有利，因为它会增加与粗心猎物的遭遇率。然而，这一假设很少被实地研究过。这项研究的目的是量化伏击掠食者在野外的遭遇率和捕获成功率，作为其与背景颜色匹配程度的函数。我们使用了蟹蛛 Misumena vatia，它的体色不同，因此可以匹配它所捕猎的花朵的颜色。我们使用完整的因子设计进行了现场操作实验，产生了蟹蛛和花朵的六种不同颜色组合，其颜色匹配程度不同。当我们不断拍摄蜘蛛的觅食活动时，丰富多样的自然昆虫会造访花朵。这使我们能够测试隐秘、蜘蛛回避和花朵吸引游客的假设，这三个假设都得到了先前研究的支持。不同群体的花客要么避开与颜色无关的蟹蛛，如独居蜂和食蚜蝇，要么忽视它们，如大黄蜂和蜜蜂。此外，与视觉上明显的蜘蛛相比，颜色匹配的蜘蛛并没有更高的遭遇率和捕获成功率。因此，我们的结果支持蜘蛛回避假说，拒绝了其他两个假说，并发现了第四种行为：对捕食者漠不关心。由于赏花者的反应不同，因此必须采用社区方法来了解通才捕食者背景颜色匹配的功能。我们讨论了与猎物的体型和社会性以及捕食者颜色变化的功能意义相关的结果。
Cryptic coloration is assumed to be beneficial to predators because of an increased encounter rate with unwary prey. This hypothesis is, however, very rarely, if ever, studied in the field. The aim of this study was to quantify the encounter rate and capture success of an ambush predator, in the field, as a function of its level of colour-matching with the background. We used the crab spider Misumena vatia, which varies its body colour and can thereby match the colour of the flower it hunts upon. We carried out a manipulative field experiment using a complete factorial design resulting in six different colour combinations of crab spiders and flowers differing in their degree of colour-matching. A rich and diverse set of naturally occurring insects visited the flowers while we continuously video-recorded the spider's foraging activity. This enabled us to test the crypsis, the spider avoidance and the flower visitor attraction hypotheses, all three supported by previous studies. Flower visitors of different groups either avoided crab spiders independent of colour-matching, such as solitary bees and syrphid flies, or ignored them, such as bumble-bees and honeybees. Moreover, colour-matched spiders did not have a higher encounter rate and capture success compared to the visually apparent ones. Thus, our results support the spider avoidance hypothesis, reject the two other hypotheses and uncovered a fourth behaviour: indifference to predators. Because flower visitors reacted differently, a community approach is mandatory in order to understand the function of background colour-matching in generalist predators. We discuss our results in relation to the size and sociality of the prey and in relation to the functional significance of colour change in this predator.