Abstract
Accurate morphological ant mimicry by Myrmarachne jumping spiders confers strong protective benefits against predators. However, it has been hypothesized that the slender and constricted ant-like appearance imposes costs on the hunting ability because their jumping power to capture prey is obtained from hydraulic pressure in their bodies. This hypothesis remains to be sufficiently investigated. We compared the jumping and prey-capture abilities of seven Myrmarachne species and non-myrmecomorphic salticids collected from tropical forests in Malaysian Borneo and northeastern Thailand. We found that the mimics had significantly reduced abilities compared with the non-mimics. The analysis using geometric morphometric techniques revealed that the reduced abilities were strongly associated with the morphological traits for ant mimicry and relatively lower abilities were found in Myrmarachne species with a more narrowed form. These results support the hypothesis that the jumping ability to capture prey is constrained by the morphological mimicry and provide a new insight into understanding the evolutionary costs of accurate mimicry.
Highlights
Morphological ant mimicry is widespread in s piders[1]
We used geometric morphometric techniques to quantify the body shapes of Myrmarachne spiders and test the hypothesis that a reduction in the jumping proficiency is associated with the shape adaptations related to ant mimicry
Canonical variate analysis (CVA) of the body shape of the seven Myrmarachne species (M. acromegalis, M. cornuta, M. hashimotoi, M. malayana, M. maxillosa, M. melanocephala, and M. plataleoides) and non-myrmecomorphic spiders showed that the CVA1 axis clearly distinguished the mimics from non-mimics (Fig. 2a)
Summary
Morphological ant mimicry is widespread in s piders[1]. Ants possess species-specific combinations of strong defensive traits, including powerful mouthparts and stings, chemical defenses, general aggressiveness, and nest-materecruiting ability[2]. Some of the most striking examples of morphological ant mimicry are found in the Myrmarachne, the largest genus of jumping spiders (Salticidae) with more than 200 species[3,4,5]. Because each Myrmarachne species morphologically mimics the characteristics of a particular species or genus of an ant, the variations in the jumping abilities are expected to be associated with the variations in their ant-mimetic morphological traits. We used geometric morphometric techniques (an approach that provides a mathematical description of biological forms) to quantify the body shapes of Myrmarachne spiders and test the hypothesis that a reduction in the jumping proficiency is associated with the shape adaptations related to ant mimicry. This study, for the first time, provides quantitative evidence to show that the accurate resemblance of Myrmarachne spiders to ants is likely to constrain their jumping ability for catching prey. Our findings provide novel insights to further our understanding of the evolution and maintenance of accurate mimicry in ant-mimetic jumping spiders
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