Death of an order: a comprehensive molecular phylogenetic study confirms that termites are eusocial cockroaches

Abstract

Termites are instantly recognizable mound-builders and house-eaters: their complex social lifestyles have made them incredibly successful throughout the tropics. Although known as 'white ants', they are not ants and their relationships with other insects remain unclear. Our molecular phylogenetic analyses, the most comprehensive yet attempted, show that termites are social cockroaches, no longer meriting being classified as a separate order (Isoptera) from the cockroaches (Blattodea). Instead, we propose that they should be treated as a family (Termitidae) of cockroaches. It is surprising to find that a group of wood-feeding cockroaches has evolved full sociality, as other ecologically dominant fully social insects (e.g. ants, social bees and social wasps) have evolved from solitary predatory wasps.

Figure 1

Topology of Bayesian majority rules consensus tree of 2501 trees. Red branch indicates position of Cryptocercus, blue branches indicate termite lineage. Numbers under the branches indicate posterior probabilities (i.e. the proportion of the 2501 sampled trees that contain the node) for key nodes. Names of major clades (e.g. superfamilies) are provisional.

Figure 2

Simplified phylogenetic tree showing major evolutionary transitions within ancestral forms leading to the termites. 1, ootheca formed from secretions of the asymmetrical accessory glands; 2, ootheca formed internally in vestibulum, keel pointing upwards until deposited; 3, wood -feeding, unique hypermastigid and oxymonad gut flagellate assemblages, biparental care, proctodeal trophallaxis; and 4, male genitalia bilaterally symmetrical and much reduced, sperm immotile or weakly motile, true soldier caste, overlapping generations with reproductive division of labour (‘eusociality’).