Diet and nest resource exploitation in solitary wasps (Hymenoptera: Crabronidae): morphological, behavioural and environmental effects on species and individual specialization".
Tesi di Dottorato
Data di Pubblicazione:
2012
Citazione:
Diet and nest resource exploitation in solitary wasps (Hymenoptera: Crabronidae): morphological, behavioural and environmental effects on species and individual specialization" / L.m. Chatenoud ; tutori: F. Andrietti, C. Polidori, A. Tintori ; coordinatore: N. Saino. Universita' degli Studi di Milano, 2012 Mar 05. 22. ciclo, Anno Accademico 2009.
Abstract:
Apoid wasps of both families Crabronidae and Sphecidae (Hymenoptera) include insects that are predatory, free-living as adults and parasitoids, defenceless and immobile as larvae, and represent one of the best groups of animals to analyze for ecological topics such as diet and nest resource exploitation and their morphological, behavioural and environmental effects on species and individual specialization.
In this study 7 different species are analyzed. Two of them are members of Cerceris genus: C. rubida (Jurine, 1807) and C. arenaria (Linnaeus, 1758); the other five represent all the species of Sceliphron present in Italy: S. spirifex (Linnaeus 1758), S. caementarium (Drury 1770), S. curvatum (F. Smith 1870), S. madraspatanum tubifex (Fabricius 1781), and S. destillatorium (Illiger 1807).
Two aspects of the resources exploitation will be presented. The first (Section 1 and 2) is related to factors influencing foraging; the second (Section 3), instead, concerns wasp nesting habits.
In particular, Section 1 provides information on the evolution of prey specialization through an in-depth analysis of diet preference in the ‘generalist’ beetle-hunting wasp C. rubida.
Section 2, describes and quantifies a few factors, as wasp and prey size and weather condition, influencing foraging patterns of the digger wasp C. arenaria.
Finally, Section 3 concerns the description of mud-balls building in 5 species of Sceliphron to highlight the differences, if any, which may exist in globule formation ethology.
On the whole, the presented analysis investigate some main aspect of wasp environmental relations, for which, up to date, scanty information is available: prey selection, factors influencing wasp foraging pattern behaviour and, at last, ethological differences among species of the same genus in relation to a very stereotyped resource exploitation habit.
Throughout this thesis, particular attention was paid to statistical aspects. Distributions of data as well as inferential models have been carefully studied and chosen.
Hereafter, are briefly summarized aims and main results of the three sections listed above:
Section 1: 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 C. 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 correlated with that of their prey, accounting for the frequencies of hunted prey and the strong individual specialization for both taxa and size. However, some species were significantly over-hunted than expected and others significantly avoided by the wasps, causing an unexpected major role of prey taxon over the other explanatory variables (body size, body shape, sex, availability). This contrasts to that found in other wasp species for which prey selection is essentially based on their ecology and size or their relative abundance (opportunism). The result shows that even an apparent ‘generalist’ predator may turn out to be taxonomically specialized. One suggests that the effect of size constraints and developmental plan of prey (holometaboulous versus hemimetabolous) may have promoted either taxonomic opportunism or specialization in different lineages of apoid wasps.
Section 2: Foraging patterns of digger wasps are strongly influenced by both size and we
Tipologia IRIS:
Tesi di dottorato
Keywords:
biological traits ; resource use ; foraging ; solitary wasp ; mud ball
Elenco autori:
L.M. Chatenoud
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