Brood care and social evolution in termites

Abstract

Cooperative brood care is assumed to be the common driving factor leading to sociality. While this seems to be true for social Hymenoptera and many cooperatively breeding vertebrates, the importance of brood care for the evolution of eusociality in termites is unclear. A first step in elucidating this problem is an assessment of the ancestral condition in termites. We investigated this by determining the overall level of brood care behaviour across four termite species that cover the phylogenetic diversity of the lower termites. Brood care was low in the three species (all from different families) that had an ancestral wood-dwelling lifestyle of living in a single piece of wood that serves as food and shelter. In the fourth species, a lower termite that evolved outside foraging, brood care was more common. Together with data for higher termites, this suggests that brood care in termites only becomes important when switching from a wood-dwelling to a foraging lifestyle. These results imply that early social evolution in termites was driven by benefits of increased defence, while eusociality in Hymenoptera and cooperative breeding in birds and mammals are primarily based on brood care.

Molecular traces of alternative social organization in a termite genome

“…This difference may have evolved as a result of very different nesting behaviours. While Hymenoptera forage away from their nests, encountering a variety of odorants, including those from non-nestmate conspecifics, many of the basal termites, including Z. nevadensis, live their entire lives within a single log 61 . Most of the ants and the honey bee show sophisticated communication behaviour and nestmate recognition, and have an expanded number of ORs relative to Z. nevadensis.…”

“…We would not expect that all termites have fewer ORs. The 'higher' termites, much like ants, have a more sophisticated division of labour, forage outside their nest and exhibit recruitment behaviour 61 . We predict that these species would show an increase in OR genes compared with Z. nevadensis, assuming the expansion of ORs is indicative of communication ability.…”

Beyond promiscuity: mate-choice commitments in social breeding

“…Further work will be needed to clarify the constraints that prevented the foraging Mastotermitidae and Hodotermididae from carving out their own major eusocial niche space comparable to the Termitidae. That non-foraging lower termites are essentially cooperative breeders (albeit with a differentiated soldier caste, see §3b) has recently been underlined by evidence that larvae and nymphs of several genera provide little indirectfitness-driven brood care, but rely on the likelihood of later advancement to breeder status, either in the same nest or after dispersal to find a mate and found a new colony [120][121][122], not unlike the Polistes wasps discussed above. Few species have been investigated, but it appears that these lower termites still have some sperm motility, consistent with experiencing a non-zero probability of promiscuity later in life [71,123 -125].…”

“…The basal termite lineages have strictly monogamous colony founding, but face competition later in life from rstb.royalsocietypublishing.org Phil Trans R Soc B 368: 20120050 conspecific founding pairs colonizing the same log [120,122,123]. As the full-sibling larvae of these founding pairs start eating out cavities and gallery systems, colonies are bound to meet and compete for feeding and nesting resources.…”

Neotenic reproductives influence worker caste differentiation in the termite Reticulitermes speratus (Isoptera; Rhinotermitidae)

“…Stomodeal trophallaxis is thought to be important in caste determination in other termite species (Lüscher, 1961;Korb et al, 2012). We observed stomodeal trophallaxis and grooming among workers, larvae, and all forms of neotenics with the exception of male ergatoids (data not shown).…”