Improving phylogenetic resolution in rove beetle systematics via rigorous study of fossils

Publication Type:Conference Paper
Year of Publication:2016
Authors:D. Żyła, Solodovnikov A.
Conference Name:The 7th International Conference on Fossil Insects, Arthropods and Amber
Date Published:26/04/2016
Publisher:Siri Scientific Press
Conference Location:National Museum of Scotland, Edinburgh

With more than 60,000 described species, rove beetles (Coleoptera: Staphylinidae) are an outstanding example of mega-diversity. With the short elytra leaving their abdomen exposed and flexible, they are well adapted to cryptic microhabitats in nearly all possible terrestrial habitats. The family is divided into four groups of subfamilies that supposedly represent monophyletic lineages. The largest of them, the Staphylinine-group, consists of nine subfamilies, and includes Steninae, one of the most striking examples of the evolutionary mega radiation.Steninae comprise more than 2700 species organised in two extant genera, the mega-diverse Stenus Latreille, 1797 and much less species-rich Dianous Leach, 1819. With ~2500 described species, Stenus is among the most diverse genera of organisms but is also fairly conservative in its morphology. Due to lacking robust phylogenetic study, nothing is known about how, when and why Steninae radiated to become the mega-diverse group we see today. Usually Steninae has been considered to be closely related to the subfamily Euaesthetinae, but their placement within the Staphylinine-group still remains controversial. However, neither morphology has ever been combined with molecular data in a phylogenetic analysis, nor has the fossil record been used for such inferrence. The latter, however, is crucial since the combination of phylogenetic signals preserved in recent species with palaeontological data is the most effective way to explore the history of a given organismal group, especially deep divergencies. So far, only two species of Mesozoic Stenus have been described, and all other known fossils of Steninae come from the Cenozoic deposits (Cai et al., 2014). Although not very abundant, all these fossils are of great significance for understanding the origin and early diversification of this lineage. Here, we present a new extinct genus of Steninae notably different from all extant members of this subfamily. The studied material consists of 15 specimens from one piece of Burmese amber (Late Cretaceous, earliest Cenomanian) that belong to at least two extinct species. Our new finding is discussed in the context of a possible scenario for the early evolution of Steninae prior to their modern radiation, and in terms of the possible sister-group relationships of this subfamily within the Staphylinine-group.

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