Any myrmecologist that spends time in the field studying ants knows from their own experience that there are a lot of spiders in most places where ants are found. With their diversity and abundance, it should not be any surprise there are spiders that feed on ants. The particulars of prey specialization and dependence on ants as prey vary with the spider species and genus, as does the range of ants of that are preyed upon.
Obligate Ant Predators
Spiders of the genus Zodarion (Araneae: Zodariidae) exclusively prey on ants. Pekár et al. (2018) studied various aspects of how these spiders prey on ants:
Zodarion species chase relatively giant and dangerous ants and overcome them by a combination of very fast attack and venom injection (Pekár, 2004a; Pekár, Šedo, Líıznarová, Korenko, & Zdráhal, 2014). The venom functions both to facilitate capture (including the reduction in prey loss due to escape) and to minimize injury to the spider, as ants can counter-attack (Pekáar, 2004b). As a result, we expect the selection for venom adaptation to be very strong and to lead to venom economy through production of very specific compounds.
Myrmecophagous or ant-eating predators have been assumed to be specialized at the family level, that is, to exploit a variety of related ant species. However, our previous studies indicated that Zodarion spiders not only failed to paralyse alternative prey (Pekár, 2004a) but possessed a high capture efficacy on a specific ant genus (e.g., Pekár, Král, & Lubin, 2005), suggesting that they are specialized on a particular subfamily or genus. It appears that ants have exerted selection on venom composition, which leads to increased capture efficacy on the focal ant species but decreased efficacy on other ant species (Pekár et al., 2005).
Data on natural diet obtained by next-generation sequencing and field observations showed that the six Zodarion species exploit different ant species. Their phylogeny, based on mitochondrial and nuclear genes, correlated with the composition of their natural prey, indicating that closely related Zodarion species specialize on similar ant species. Prey-capture parameters differed among Zodarion species suggesting preyspecific efficacy. Similarly, the venom profiles of both low and high molecular compounds differed among species. Only the profiles of low molecular compounds were correlated with capture efficacy parameters, suggesting that the venom of Zodarion spiders contains prey-specific components. Our study suggests that Iberian Zodarion spiders are specialized on particular ant species.
- Pekar, S., L. Petrakova, O. Sedo, S. Korenko, and Z. Zdrahal. 2018. Trophic niche, capture efficiency and venom profiles of six sympatric ant-eating spider species (Araneae: Zodariidae). Molecular Ecology. 27:1053-1064. doi:10.1111/mec.14485