Comparative morphology of the mandibles and head structures of corbiculate bees (Hymenoptera: Apidae: Apini)

Abstract

Phylogenetic relationships of corbiculate bees have been a well-known focus of controversies over the past 30 years. The majority of the morphological datasets support the monophyly of Apina + Meliponina, whereas molecular datasets recover Meliponina as sister to Bombina. This issue is especially critical to the proper understanding of the evolution of clusters of traits that define the corbiculate eusocial behaviour. This work provides a description and discussion on characters of the head capsule, mandibles and sitophore of bees. Thirty-three characters are proposed and optimized within concurrent phylogenetic hypotheses for corbiculate bees, which results in seven derived character-states supporting the monophyly of the Apina + Meliponina + Bombina and nine supporting the Apina + Meliponina clades. Although some striking synapomorphies (e.g. tentorial bridge, pleurostomal condyle, hypopharyngeal lobe) support the former clade, most characters supporting the latter (i.e. Apina + Meliponina) were losses/reductions. Moreover, two previously undescribed character transformations on hypostoma and sitophore favour the Bombina + Meliponina clade. Internal head capsule characters are useful for phylogenetic analysis in comparative studies of bees, and corbiculate bees in particular, when efforts are made to solve the 'corbiculate controversy'. An attempt is made to standardize the current terminology used for bees and for other Hymenoptera.

Stingless bees in Miocene amber of southeastern China (Hymenoptera: Apidae)

“…The closest relative of the Melikertini + Meliponini clade remains somewhat controversial. Many analyses based on diverse data support the highly eusocial Apini as sister, along with the concomitant reconstruction of a single origin of highly eusocial behavior among corbiculate bees (e.g., Roig-Alsina & Michener, 1993;Schultz et al, 1999Schultz et al, , 2001Engel, 2001b;Noll, 2002;Cardinal & Packer, 2007;Canevazzi & Noll, 2015;Porto et al, 2016Porto et al, , 2017Noll et al, in press). Nonetheless, some analyses suggest that meliponines are more closely related to the primitively eusocial bumble bees, with Apis Linnaeus clustering with the orchid bees or as sister to Meliponini + Engel & al.…”

The relevance of the mesosomal internal structures to the phylogeny of Augochlorini bees (Hymenoptera: Halictinae)

“…For morphological data, recent examples come from internal morphology. Zimmermann and Vilhelmsen () found evidence from internal head anatomy to support a new hypothesis for the sister group of Aculeata, Porto, Almeida and Vilhelmsen () and Porto, Vilhelmsen and Almeida () studied head and mesosoma internal morphology to infer the relationships of corbiculate bees.…”

A primitive honey bee from the Middle Miocene deposits of southeastern Yunnan, China (Hymenoptera, Apidae)

“…The putatively basalmost tribe of corbiculate bees, the Euglossini (orchid bees), are solitary or communal, with a few examples of primitive eusocial behavior in some species (Boff et al 2015; Andrade et al 2016). Relationships among these tribes have been controversial, although most evidence converges on a Darwinian null-hypothesis supporting a single origin of eusociality in the common ancestor of Bombini + Meliponini + Apini, and a single origin of the highly eusocial grade in the common ancestor of Meliponini + Apini (Michener 1990; Schultz et al 1999, 2001; Engel 2001a; Noll 2002; Cardinal and Packer 2007; Canevazzi and Noll 2015; Porto et al 2016, in press). Alternatively, some molecular evidence has placed meliponines as sister to bombines (e.g., Cameron and Mardulyn 2001; Kawakita et al 2008; Rodriguez-Serrano et al 2012), although in the most recent such analysis data from Euglossini were excluded (Kwong et al 2017), and the potential impact of excluding one of the four surviving corbiculate tribes for driving spurious results has not been explored.…”