Termite colonies from mid-Cretaceous Myanmar demonstrate their early eusocial lifestyle in damp wood

Abstract

Insect eusociality is characterized by cooperative brood care, reproductive division of labour and multiple generations of adults within a colony. The morphological specializations of the different termite castes from Burmese amber were recently reported, indicating the termites possessed advanced sociality in the mid-Cretaceous. Unfortunately, all the reported Cretaceous termites are individually preserved, which does not cover the behaviours of the cooperative brood care and multiple generations of adults in the nests of the Cretaceous termites. Herein, we report three eusocial aggregations from colonies of the oldest known Stolotermitidae, Cosmotermesgen. nov., in 100 Ma mid-Cretaceous Burmese amber. One large aggregation, comprising 8 soldiers, 56 workers/pseudergates and 25 immatures of different instars, additionally presents the behaviours of cooperative brood care and overlapping generations. Furthermore, taphonomic evidence indicates Cosmotermes most probably dwelled in damp/rotting wood, which provides a broader horizon of the early societies and ecology of the eusocial Cosmotermes.

Growth and miniaturization among alvarezsauroid dinosaurs

“…37 Morphological specializations of the different termite castes and even large eusocial aggregations of termites were recently reported in mid-Cretaceous Burmese amber, revealing an unanticipated flourishing of eusocial termite societies then. 38,39 These prosperous termite colonies from the mid-to Late Cretaceous might have made an obligate myrmecophagous ecological niche possible. Earlier macroevolutionary studies of dinosaurs rarely exhibited cases of coevolution and ecological interaction during the KTR.…”

“…According to recent fossil and molecular studies, the eusocial insects are mostly recognized as emerging during the latter half of the Mesozoic. 39 The fossil record shows that termites started an early radiation in the Early Cretaceous, 38,39 and molecular dates for the most recent common ancestor of ants ranges from 115-135 Mya. [61][62][63] The time of emergence of eusocial insects corresponds with the miniaturisation recognized by our analyses, supporting our hypothesis of a dietary shift as a specific ecological driver for miniaturization of alvarezsauroids.…”

New species of Hybristodryinus Engel (Hymenoptera, Dryinidae) from mid-Cretaceous amber of northern Myanmar, with notes on their possible hosts

“…Mid-Cretaceous Kachin (Myanmar) amber (about 99 Ma) is the famous Burmese amber (Lin et al 2019;Cao et al 2020;Zhao et al 2020), different from the recently discovered Campanian Tilin amber (Zheng et al 2018) and Albian Hkamti amber (Xing and Qiu 2020). Dryinidae from Burmese amber are not common.…”

Revising dating estimates and the antiquity of eusociality in termites using the fossilized birth–death process

“…Three nodes were assigned offset exponential priors: the root of the tree (minimum age: 225 Ma, mean age: 270 Ma), Blattodea (150, 225 Ma), and Isoptera (137, 150 Ma). Those ages were set according to the latest studies (Bourguignon et al ., 2015, 2018; Legendre et al ., 2015; Engel et al ., 2016; Bucek et al ., 2019; Evangelista et al ., 2019; Zhao et al ., 2020a; more details in Appendix S3).…”

“…The spectacular evolutionary and ecological success of termites is mostly attributed to their highly integrated eusocial system, defined by cooperative brood care, overlapping generations within a colony and the division of labour into reproductive and non‐reproductive castes (Lin & Michener, 1972; Wilson, 1971, 1975; Wilson & Hölldobler, 2005). Termites are regarded as the first animals that have evolved eusociality (Grimaldi & Engel, 2005; Legendre & Condamine, 2018; Barden & Engel, 2020; Zhao et al ., 2020b) because they show the oldest record of morphologically specialized soldiers (Engel et al ., 2016; Zhao et al ., 2019, 2020a), although the discoveries of Cretaceous ant fossils have questioned this assertion ( e.g . Perrichot, 2019).…”