Corbiculate Bees (Hymenoptera: Apidae): Exploring the Limits of Morphological Data to Solve a Hard Phylogenetic Problem

Corbiculate bees comprise a distinctive radiation of animals including many familiar species, such as honey bees and bumble bees. The group exhibits a broad variety of morphologies and behaviors, including solitary, social, and cleptoparasitic lifestyles. Since corbiculate bees play a critical role for the interpretation of eusocial behaviors, understanding their phylogeny is crucial to explain patterns and mechanisms of social evolution. Despite advances to unveil corbiculate relationships employing genomic data, the drivers of conflict between molecular and morphological hypotheses are still not fully understood. Morphological datasets favor a single origin for highly eusocial behaviors (i.e., Apini + Meliponini) whereas molecular datasets favor other scenarios (e.g., Bombini + Meliponini). Explanations for this incongruence have been suggested, including quality, quantity, and source of data or methodological issues. In this work we tackled this problem by generating the most extensive morphological dataset for the corbiculate bee species by exploring characters from all body regions, including external and internal adult skeletal anatomy. We produced a matrix with 289 characters for 53 taxa of Apidae, including 24 corbiculate bees. We explored different analyses and optimality criteria including extended implied weights parsimony and two partitioning schemes for Bayesian inferences. We contrasted hypotheses with Bayesian topological tests and conducted analyses to investigate if characters were prone to concerted convergence. Our results are congruent with the conclusions of previous studies based on morphology, recovering Apini sister to Meliponini and both of them together sister to Bombini. Finally, we provide our interpretations on the corbiculate controversy and provide a conciliatory scenario about this issue.

Relationships within the Australo-Papuan Fairy-wrens (Aves : Malurinae) : an Evaluation of the Utility of Allozyme Data

Allozyme variation at 39 presumptive loci was screened across 180 specimens representing 18 species of Australo-Papuan fairy-wrens (Maluridae). The results identified two major clusters within Malurus. One comprised M. cyaneus, M. splendens, M. coronatus, M. melanocephalus, M. leucopterus and M. alboscapulatus. The other comprisedM. lamberti, M. amabilis, M. pulcherrimus and M. elegans. M. grayi and M. cyanocephalus were variously associated with these two assemblages. Most analyses aligned Clytomias with Malurus relative to Stipiturus. The findings from the present study indicate that allozyme data are well suited to phylogenetic inference whether analysed as distances or as discrete characters, provided that only relatively robust branches are accepted. When only such branches were considered there was complete congruence between the analyses. Nevertheless, congruence per se between analyses was not necessarily a reflection of robust branching patterns, as illustrated by the position of Clytomias. Of analyses with discrete characters, those that treated loci as characters and the commonest allele as the state appeared to be a particularly effective approach, provided that the distribution of discarded alleles in the initial topology is considered a posteriori. The allozyme data confirmed several previously accepted lineages, and identified surprising new links between several taxa as well. These links were supported biogeographically and, in some aspects, morphologically. Those phylogenetic nodes that were poorly resolved can now be tested by more sensitive DNA-based approaches. By using allozymes to establish robust clades and then to identify areas in need of further resolution, DNA-based studies can be focused better on phylogenetic problem areas, thereby promoting more efficient use of time and resources.