Emergence of a superradiation: pselaphine rove beetles in mid‐Cretaceous amber from Myanmar and their evolutionary implications

Abstract

Pselaphinae is an exceptionally species‐rich, globally distributed subfamily of minute rove beetles (Staphylinidae), many of which are inquilines of social insects. Deducing the factors that drove pselaphine diversification and their evolutionary predisposition to inquilinism requires a reliable timescale of pselaphine cladogenesis. Pselaphinae is split into a small and highly plesiomorphic supertribe, Faronitae, and its sister group, the ‘higher Pselaphinae’ – a vast multi‐tribe clade with a more derived morphological ground plan, and which includes all known instances of inquilinism. The higher Pselaphinae is dominated by tribes with a Gondwanan taxonomic bias. However, a minority of tribes are limited to the Nearctic and Palearctic ecozones, implying a potentially older, Pangaean origin of the higher Pselaphinae as a whole. Here, I describe fossils from mid‐Cretaceous (∼99 million years old) Burmese amber that confirm the existence of crown‐group higher pselaphines on the Eurasian supercontinent prior to contact with Gondwanan landmasses. Protrichonyx rafifrons gen. et sp.n. is placed incertae sedis within the higher Pselaphinae. Boreotethys gen.n., erected for B. grimaldii sp.n. and B. arctopteryx sp.n., represents an extinct sister taxon and putative stem group of Bythinini, a Recent tribe with a primarily Holarctic distribution. The Laurasian palaeolocality of the newly described taxa implies that higher pselaphines are indeed probably of Jurassic, Pangaean extraction and that the Laurasian‐Gondwanan tribal dichotomy of this clade may have developed vicariantly following Pangaean rifting. Higher pselaphines probably predate the earliest ants. Their physically protective morphological ground plan may have been a preadaptation for myrmecophily when ants became diverse and ecologically ubiquitous, much later in the Cenozoic. This published work has been registered in ZooBank, http://zoobank.org/urn:lsid:zoobank.org:pub:36E3FE2A-B947-422D-89CA-0EF43B99C382.

Total‐evidence approach reveals an extinct lineage of Paederinae rove beetles from Cretaceous Burmese amber

“…Our study is one of the few examples in insects of applying the total‐evidence approach to resolve the position of a fossil taxon, and only the third for rove beetles. Although the other two (Parker ; Yin et al . ) successfully used the method, their molecular dataset consisted of only a short region of 28S ribosomal RNA, while ours contains six gene fragments.…”

“…The authors reconstructed the phylogeny of the subtribe Philonthina based on the total‐evidence analyses of molecular (six genes, 4471 bp) and morphological (113 characters) data, albeit without fossil taxa. Until now, the only analyses incorporating molecular data and morphological data for extant and fossil taxa were by Parker () and Yin et al . () who tested the tribal placement of Cretaceous fossil pselaphine rove beetles (Staphylinidae, Pselaphinae) based on total‐evidence analyses of one gene region (28S ribosomal RNA) and 58 morphological characters.…”

Evidence for social parasitism of early insect societies by Cretaceous rove beetles

“…Hence, the observed or inferred presence of all of these groups in the mid-Cretaceous makes it possible that Mesosymbion was not alone in targeting colonies, and that multiple aleocharine taxa were social parasites at this time. In addition, crown-group Pselaphinae—another rove beetle subfamily equally predisposed to ant and termite exploitation12—have been described from Burmese amber54. It may be that by the mid-Cretaceous, social insects already possessed a ‘bestiary' of social parasites11.…”

Ant diversity as a direct and indirect driver of pselaphine rove beetle (Coleoptera: Staphylinidae) functional diversity in tropical rainforests, Sabah, Malaysian Borneo

“…Myrmecophily, a symbiotic association with ants, is an ancient feature of ant ecology (Parker, ; Parker & Grimaldi, ) and has arisen in many arthropod groups (Kronauer & Pierce, ). However, there is an evolutionary bias toward beetles (Coleoptera), where myrmecophily is most common (Parker, ).…”

“…Pselaphines deviate from the typical staphylinid body plan in possessing a more compact, sclerotized integument that reduces abdominal flexibility. Although a relatively invariant body plan would appear to restrict their movements through the substrate, pselaphines have radiated successfully in the leaf litter, particularly in ant‐dominated tropical forest floors (Chandler, ; Parker, ; Sakchoowong et al, ).…”