Comparative morphology of internal skeletal structures of the head of corbiculate bees (Apidae: Apini)

Abstract

Bees are aculeate hymenopterans, which form a taxon that comprises slightly more than 20,000 described species classified into seven families. In addition to a considerable morphological variation, a remarkable diversity of social behaviors is known to exist in bees. Several species are truly solitary; whereas various taxa exhibit some level of social organization, and groups showing a high degree of eusocial behavior (the latter is characterized by division of labor, cooperative brood care, caste differentiation, and superposition of generations). One of the most interesting groups to study the evolution of eusociality is that of corbiculate bees (Apidae: Apinae: Apini). This group is subdivided into four subtribes, three of which are eusocial. Among the four subtribes, Apina (honeybees) and Meliponina (stingless bees) comprise the so-called "advanced eusocial" groups, whereas Bombina (bumblebees) are "primitively eusocial", and Euglossina (orchid-bees) are mainly solitary, but variations exist. Phylogenetic relationships among corbiculate bees have been under intense controversy for the last three decades, thus hampering a robust understanding of evolution of eusociality in this group. Overall, most hypotheses based on morphological and behavioral data point to a clade grouping Apina and Meliponina, therefore pointing to a single origin of advanced eusocial behavior. Molecular datasets, on the other hand, consistently indicate independent origins for this behavior. Considering this, there is an urgent demand for additional morphological data that could elucidate the matter and clarify incongruences among the different data sources so far used. In this way, the main goal of this BEPE project is to execute an anatomical study of internal skeletal structures of the head of representative species of corbiculate bees using a technology only recently applied to fine morphological studies, called Confocal Laser Scanning Microscopy (CLSM). This will be accomplished using the infrastructure available at University of Copenhagen in collaboration with Dr. Lars Bjørn Vilhelmsen from the Natural History Museum of Denmark, University of Copenhagen, Denmark. Novel morphological characters generated in this study will also be incorporated with previously proposed morphological characters in the main Master's Project. This research will enable a deeper and refined understanding of complex internal anatomical clusters of the head of bees, and shed light the origin and evolution of eusocial behavior in bees. (AU)