Early Evolution of Specialized Termitophily in Cretaceous Rove Beetles

Abstract

Termitophiles, symbionts that live in termite nests, include a wide range of morphologically and behaviorally specialized organisms. Complex adaptive mechanisms permit these animals to integrate into societies and to exploit their controlled physical conditions and plentiful resources, as well as to garner protection inside termite nests. An understanding of the early evolution of termitophily is challenging owing to a scarcity of fossil termitophiles, with all known reliable records occurring from the Miocene (approximately 19 million years ago [mya]) [1-6], and an equivocal termitophile belonging to the largely free-living Mesoporini from the mid-Cretaceous [7]. Here we report the oldest, morphologically specialized, and obligate termitophiles from mid-Cretaceous Burmese amber (99 mya). Cretotrichopsenius burmiticus gen. et sp. nov. belongs to Trichopseniini, a group of distinctive termitophilous aleocharine rove beetles, all of which possess specialized swollen or horseshoe-crab-shaped body plans. Cretotrichopsenius display the protective horseshoe-crab-shaped body form typical of many modern termitophiles, with concealed head and antennae and strong posteriorly directed abdominal setae. Cretotrichopsenius represent the earliest definitive termitophiles, shedding light on host associations in the early evolution of termite societies. The fossil reveals that ancient termite societies were quickly invaded by beetles and by multiple independent lineages of social parasites over the subsequent eons.

Termitariophily: expanding the concept of termitophily in a physogastric rove beetle (Coleoptera: Staphylinidae)

“…Moreover, Corotocini, being part of the 'higher' Aleocharinae, would have a limuloid stock among their early ancestors (Yamamoto et al, 2016;Cai et al, 2017). Moreover, Corotocini, being part of the 'higher' Aleocharinae, would have a limuloid stock among their early ancestors (Yamamoto et al, 2016;Cai et al, 2017).…”

“…In spite of the disproportionate number of examples of termitophilic species among Staphylinidae: Aleocharinae, the evolution of this type of symbiosis in these beetles remains elusive (Kanao et al, 2016;Yamamoto et al, 2016;Cai et al, 2017;Yamamoto et al, 2017). Within Aleocharinae, the tribe Corotocini stands as the largest and most specialized tribe, originating in the Neotropics in close association with Termitidae: Nasutitermitinae termites (Seevers, 1957;Jacobson, 1985).…”

“…Limuloid and physogastric body plans are the principal preadaptive ecomorphs allowing termitophily in Aleocharinae beetles (Cai et al, 2017). It seems non-contentious that the earliest 'higher' group Aleocharinae beetles (which includes Corotocini) are from the Paleogene: Eocene, c. 45 million years ago (mya), whereas the earliest Termitidae termites (in which Nasutitermitinae: Constrictotermes are included), are from the transition between the Paleogene: Paleocene and the Paleogene: Eocene, c. 55 mya (Engel et al, 2009;Cai et al, 2017).…”

“…On the other hand, by constraining mobility (Cai et al, 2017) physogastry compromises swift manoeuvring to escape predators and prolonged locomotion to find food and mates. After all, a mere enlargement of the abdomen via fat body accumulation (as opposed to via pregnancy) would potentially suffice as a disguise to enhance termite-beetle interactions or to defend beetles against their predators.…”

“…After all, a mere enlargement of the abdomen via fat body accumulation (as opposed to via pregnancy) would potentially suffice as a disguise to enhance termite-beetle interactions or to defend beetles against their predators. On the other hand, by constraining mobility (Cai et al, 2017) physogastry compromises swift manoeuvring to escape predators and prolonged locomotion to find food and mates. Thus, physogastric individuals would be advantaged in a sheltered and enclosed environment where predation risks are diminished, and nutritional and mating resources are predictable.…”