Figure 1.
The evolution of eusociality in Apidae.
a) The Bayesian maximum clade credibility tree of Apidae [13]. Posterior probabilities are represented by the thickness of the branches. Character state assignments of the taxa used for the ancestral state reconstruction of the traditional and complex social level character and of the 5 life-history traits are shown to the right of the tree (black = solitary, yellow = social, green = primitively eusocial, blue = advanced eusocial, red = parasitic, light grey = absent, dark grey = present). The character states do not necessarily represent the state of that particular species, but how that terminal taxon was coded to represent the state(s) of the clade it represents. b) Transitions allowed between the four behavioral states in our model-based ancestral state reconstruction of the complex social level character (Sol = solitary, Soc = social, Prim = primitively eusocial, Adv = advanced eusocial, and Paras = parasitic). The model was the same for the traditional behavioral character on level of sociality, but the state social was not included. c–e) Simplified version of the corbiculate phylogeny with pie charts representing the posterior probability of the ancestral state of the node for the c) traditional social level character, d) complex social level character , and e) five life-history traits.
Table 1.
Mean and Standard error (S.E.) of the Bayes Factor tests (n = 20) comparing the harmonic mean of the likelihoods of the Bayesian ancestral state reconstruction analyses with the common ancestor of corbiculates alternatively fixed as being solitary, social, primitively eusocial, advanced eusocial, and parasitic.
Figure 2.
The antiquity of eusocial clades.
The behavioral character is mapped onto the chronogram of Apidae [13] according to the results of the Bayesian ancestral state reconstruction of the traditional social level character. Outgroup taxa used in the fossil-calibrated phylogeny have been removed from the chronogram. Black bars represent the 95% highest posterior density (HPD) on the estimated age of the eusocial clades.
Figure 3.
Estimated ages of the major eusocial insect clades.
Colored boxes indicate the time period in which the eusocial members of the clade are estimated to have originated. All estimates are based on fossil calibrated divergence time analyses except for the eusocial Vespidae, which is based on the fossil of a polistine nest from the Late Cretaceous [66]. This fossil provides a minimum age for the origin of eusocial wasps which probably originated sometime in the mid-Cretaceous [67]. Molecular studies, however, have indicated that the eusocial vespids do not form a monophyletic group and instead represent two independent eusocial lineages [84]. There is also uncertainty in the phylogenetic placement of ants relative to bees and vespids. The traditional relationships are depicted here, with ants more closely related to vespids than to bees [85], although a more recent molecular analysis suggests that ants share a more recent common ancestor with bees than vespids [86]. Termites are estimated to have originated sometime between 180 and 230 Mya [70], ants between 115 and 135 Mya [69], corbiculates 87 Mya (78 to 95 Mya), allodapines 53 Mya (41 to 65 Mya), eusocial Halictus (Halict.) 21 Mya (15 to 28 Mya) [71], eusocial Lasioglossum (Lasiogl.) 22 Mya (15 to 29 Mya) [71], and eusocial Augochlorini (Augochl.) 20 Mya (12 to 29 Mya) [71].