Taxon-biased diet preference in the ‘generalist’ beetle-hunting wasp Cerceris rubida provides insights on the evolution of prey specialization in apoid wasps

Abstract

Opportunism and specialization appear to be widespread in apoid wasps, although the factors affecting the diet preference (and thus explaining the degree of specialization) are still largely unknown. Four hypotheses that stressed the importance of the size, sex, habitat, and taxonomic identity of prey of the beetle-hunting digger wasp, Cerceris rubida, were formulated and tested. The wasp population hunted for phytophagous beetles belonging to abundant families around the wasp nesting site. In practice, the prey appeared to be hunted only in two cultivated fields, thus habitat accounted for a majority of the observed diet. The size of wasps was furthermore correlated with the size of their prey, and thus this also accounted for the frequencies of hunted prey and the strong individual specialization for both taxa and size. However, in the exploited habitat, some species were significantly over-hunted than expected and some other significantly avoided by the wasps, causing an unexpected major role of prey taxon on the probability of being hunted, over the other explanatory variables (body size, body shape, sex, availability). This contrasts to that found in other wasp species, which appear to select prey basing essentially on their ecology and size or their relative abundance (opportunism). The results obtained in the present study show that even an apparent 'generalist' predator may turn out to be taxonomically specialized. Together with a re-evaluation of previous studies, our results further suggest that the effect of size constraints and the developmental plan of prey (holometaboulous versus hemimetabolous) may have promoted either taxonomic opportunism or specialization in different lineages of apoid wasps.

Food load manipulation ability shapes flight morphology in females of central-place foraging Hymenoptera

“…In a simple model, Polidori et al [45] predicted that wasp species hunting for hemimetabolous prey can be so affected by the body growth of their preferred prey during the course of the breeding season that they may be forced to shift to different prey species at a certain point. Later, a study on the orthopteran-hunting wasp, Stizus continuus , confirmed this prediction [46].…”

Does prey mobility affect niche width and individual specialization in hunting wasps? A network‐based analysis

“…However, for three species ( C. rubida, S. continuus and P. sanbornii ) availability was estimated in the original papers from which we obtained the data. In P. sanbornii , environmental collection of potential prey gave, in three years, about 1500 individuals (thus on average about 500 per year) (Stubblefield et al 1993); on the contrary, for C. rubida and S. continuus (I and II), such values (in one year) were about 300–400 individuals (Polidori et al 2010, Santoro et al 2011). Thus, apparently availability may be somehow greater (500 vs 400 items in a year) for HMp wasps than for WMp wasps.…”

Nest-based information transfer and foraging activation in the common wasp (Vespula vulgaris)

“…Individual specialization in solitary wasps is driven by many factors, including predator/ prey size relationships (Polidori et al 2010), prey mobility (Polidori et al 2013), abundance (Santoro et al 2011) and nest-nest distance (Polidori et al 2012). The ultimate availability of the resources and the inter-individual information flow, together with the underlying learning processes involved, can be key for explaining individual foraging patterns both in a solitary and a social context.…”