Abstract
In predators an ontogenetic trophic shift includes change from small to large prey of several different taxa. In myrmecophagous predators that are also mimics of ants, the ontogenetic trophic shift should be accompanied by a parallel mimetic change. Our aim was to test whether ant-eating jumping spider, Mexcala elegans, is myrmecomorphic throughout their ontogenetic development, and whether there is an ontogenetic shift in realised trophic niche and their mimetic models. We performed field observations on the association of Mexcala with ant species and investigated the natural prey of the ontogenetic classes by means of molecular methods. Then we measured the mimetic similarity of ontogenetic morphs to putative mimetic models. We found Mexcala is an inaccurate mimic of ants both in the juvenile and adult stages. During ontogenesis it shifts mimetic models. The mimetic similarity was rather superficial, so an average bird predator should distinguish spiders from ants based on colouration. The realised trophic niche was narrow, composed mainly of ants of different species. There was no significant difference in the prey composition between ontogenetic stages. Females were more stenophagous than juveniles. We conclude that Mexcala is an ant-eating specialist that reduces its prey spectrum and shifts ant models during ontogenesis.
Highlights
In predators an ontogenetic trophic shift includes change from small to large prey of several different taxa
As predators grow in size during ontogenesis they are able to accomplish an ontogenetic shift in prey preference by selecting prey of a larger size
Among all the ant species co-occurring with Mexcala spiders, only three ant species had a similar colouration: C. cinctellus ants, which were black with golden or silver-shining gaster; Cataulacus ants, which were uniformly black; and Polyrhachis schistacea (Gerstäcker) ants, which were silver-shining grey
Summary
In predators an ontogenetic trophic shift includes change from small to large prey of several different taxa. Our aim was to test whether ant-eating jumping spider, Mexcala elegans, is myrmecomorphic throughout their ontogenetic development, and whether there is an ontogenetic shift in realised trophic niche and their mimetic models. We found Mexcala is an inaccurate mimic of ants both in the juvenile and adult stages A very few trophic specialists use their prey species for a defence This is the case in predators feeding on ants, which are their Batesian mimics (i.e. myrmecomorphy). The predator’s early ontogenetic stages are not or are only poorly myrmecomorphic This is the case in juveniles of both Aphantochilus and Zodarion spiders, whose early instars captured the same ant species as adult individuals, their mimetic similarity to their prey is rather poor[13]. The colouration may have important implication on its foraging and defensive strategy
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