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We integrated phylogenetic, biogeographic and palaeontological data to reconstruct the evolutionary history of the cuckoo wasps. We propose a phylogenetic hypothesis based on a comprehensive morphological study resulting in 300 characters coded for both living and extinct species. Phylogenetic relationships and divergence time estimation were simultaneously inferred in a Bayesian tip-dating framework, applying a relaxed morphological clock. Results unequivocally indicate Chrysididae to be monophyletic, as well as all traditionally recognized subfamilies and tribes. Within the Chrysidinae, Elampini was placed as the sister-group of the other three chrysidine tribes, with Parnopini as sister to the clade including Allocoeliini and Chrysidini. Dating analysis indicates that the major lineages started to differentiate around 130 Mya during the Early Cretaceous. The clades recognized as subfamilies started differentiating during the Palaeogene and the Neogene. Our results reveal an intricate process on the geographic evolution of chrysidid wasps and dispute previous ideas that Cretaceous-old splits in their early history could be associated with vicariant events related to the breakup between Africa and South America. The present-day southern disjunctions of some groups are interpreted as the outcome of more recent dispersals and extinctions of representatives from Nearctic and Palaearctic faunas during the Neogene, when northern continents became significantly colder. [ABSTRACT FROM AUTHOR]

Complex internal skeletal structures, despite their potential as rich sources of phylogenetic information, are still poorly described and used in comparative studies of insects in general, and bees in particular. In this study we present the results of a comprehensive investigation of the internal structures of the mesosoma of bees (e.g. prosternum, propleuron, mesofurca/metafurca and mesophragma); a comparative study was undertaken for bees in general with special emphasis on the tribe Apini. Phylogenetically informative characters are defined and the morphological terminology used for bees is standardized to that used for other Hymenoptera. The potential of these morphological complexes as sources of phylogenetic information was evaluated contrasting the data obtained here with alternative scenarios for corbiculate phylogeny and a phylogenetic analysis was performed. The prosternum possessed the largest number of unambiguous character state changes - nine transformations in the most parsimonious scenario. The changes include the produced lateral processes of the prosternum, absence of the profurcal pit, constriction between the basisternum and the furcasternum, and absence of pubescence on the surface of the basisternum. On the other hand, considerable homoplasy was observed particularly for the characters from the propleuron and mesofurca/metafurca. This may be the consequence of a long morphological branch separating Apini from the remaining apids or a rapid diversification of the corbiculate lineages. In this context, the inclusion of fossil information and use of new technologies for phenotypic studies can open new windows for future comparative morphological studies in bees. [ABSTRACT FROM AUTHOR]