What drives ant mimicry in jumping spiders?
Aposematism is one of the primary anti-predation strategies, which generate aposematic signal to warn predators. If the aposematic signals could provide protection and have evolution significance, it is possible that such signals will be exploited by signal exploiter. A good example of such aposematic signal exploiting is Batesian mimicry. Many terrestrial arthropods mimic ants morphologically and/or behaviorally and such phenomenon is commonly seen in spiders. Jumping spiders of the genus Myrmarachne exhibit perfect ant mimicry and most species resemble ant morphology and behavior in every detail. The ant mimicry of Myrmarachne has been thought as a case of Batesian mimicry. In the past, the predation pressures from spider wasps were regarded as the major selection agent driving ant mimicry in spiders. However, results of literature survey showed that jumping spiders constituted only a small portion of wasp’s prey. Moreover, the visual acuity of spider wasp is relatively low and therefore seems insufficient for driving perfect ant mimicry in Myrmarachne. Here we demonstrate that jumping spiders themselves might be one possible cause of ant mimicry in jumping spiders. I compared the mortality rate of five types of prey (ant, ant mimicking jumping spider, heterospecific jumping spider, conspecific jumping spider and fly) when they encountered large jumping spider predator in the laboratory setting. The results showed that the mortality rate on ant-mimic jumping spider were significantly lower than those of typical jumping spiders and fly, indicating that ant mimicry can effectively enhance spiders’ survival. This study also showed that the higher the size difference between encountering jumping spiders, the higher the mortality rate of the smaller ones. We suggest that ant mimicry of jumping spiders possibly emerge at early life stage. Furthermore, the high visual acuity of jumping spider seems to be a major driving force modifying precision level of ant mimicry in jumping spiders to be better and better during the evolutionary process. Therefore, jumping spiders are potentially a major driving force of perfect ant mimicry in jumping spiders, instead of the spider wasps.
Updated: Mar-10-2014 01:22:51 (Taiwan, GMT+08:00).