Prey‐race drives differentiation of biotypes in ant‐eating spiders

Abstract

Summary1. Disruptive natural selection resulting from specialization on different hosts is recognized as one of the most important driving forces in the diversification of herbivores and parasites. It has been proposed that a similar mechanism could apply to carnivorous predators too, although the evidence is still lacking. 2. Here, we show that the differentiation of biotypes of specialized ant-eating spiders of the genus Zodarion has probably been induced by prey-shifting. We focused on two forms of one species Z. styliferum from the Iberian Peninsula that presumably represent ecological races. We conducted geographic, ecological, venom-oriented, reproductive and genetic divergence analysis among multiple populations collected at a number of sites across Portugal and Madeira. 3. Geographic analysis revealed that the two forms occur in mosaic sympatry. Each form was found to associate in nature with a different ant species in a different habitat. Specifically, the styliferum form hunted predominantly Messor ants, and the extraneum form hunted mainly Camponotus ants. Laboratory experiments revealed that the two forms exhibit a significant preference for attacking focal ants, demonstrating higher paralysis efficiency, and also show different venom composition. Cross-mating of the two forms was significantly less likely than between pairs of the same form, suggesting moderate assortative mating. Phylogenetic analyses indicate low genetic differentiation of the two forms and parallel-repeated evolution of biotypes. 4. Adaptive prey-shifting correlated with habitat preference are at present the most valid explanations for biotype formation in Zodarion. The speciation of ant-eating Zodarion spiders thus appears to follow a scenario similar to that of host-shifting in parasites and herbivores.

Trophic specialisation in a predatory group: the case of prey‐specialised spiders (Araneae)

“…Comparative data on phylogeny, natural prey, predatory behaviour and venom composition suggest that diversification of these biotypes has probably been induced by prey‐shifting, as each form associates in nature with a different ant species. Laboratory experiments have also revealed significant preference and higher paralysis efficiency for preferred ants, and partial reproductive isolation (Pekár et al , ).…”

Is there ontogenetic shift in the capture traits of a prey‐specialized ant‐eating spider?

“…She found that wandering species had a reduced concentration of low molecular weight components in their venom relative to orb weavers and attributed the observed difference in immobilization to the mode of hunting. There is only a small amount of other indirect evidence supporting the notion that venom composition in spiders has prey‐specific properties (Jackson & Whitehouse, ; Jarman & Jackson, ; Pekár & Brabec, ; Pekár et al ., ). In the case of Z. rubidum , the venom composition may contain compounds specifically effective for the paralysis of Formicinae ants (both Formica and Lasius ) because similarly large Myrmicinae ants ( Myrmica and Tetramorium ) were paralyzed at longer latency.…”

Spatiotemporal fluctuations in natural selection acting on the gall‐parasitic aphid Tetraneura sorini

“…There are several examples in which an arthropod species genetically differentiates among local populations, as means of coping with local differences in host plant (Komatsu & Akimoto, 1995;Gandon et al, 1998;Toju, 2008) or host insects (Baba et al, 2012;Pek ar et al, 2012). Nevertheless, few studies have directly evaluated the direction and magnitude of selective pressures on the herbivore and parasite populations, as well as their spatiotemporal variability.…”