Field studies in the southeast Asian tropics of northwestern Thailand on the ecomorphological radiation of the rove beetle subfamily Steninae (Coleoptera Staphylinidae)

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The Steninae is a subfamily within the Staphylinidae (rove beetles), containing only two genera, i.e. Stenus (> 2600 species) and Dianous (> 200 species). Adult Stenus beetles are optically oriented predators of springtails and other small arthropods. The most obvious autapomorphic character defining Stenus is a protruding elongated lower lip (labium) with the terminally located paraglossae being modified into sticky pads. This exceptional adhesive prey-capture apparatus can be rapidly protruded towards the prey. In Dianous, the proposed sister group of Stenus, the labium is not specially elongated and does not form an adhesive prey-capture apparatus. Accordingly, Dianous beetles catch their prey solely using their mandibles. Steninae beetles prefer moist habitats, where they inhabit waterside environments or the moist litter and humus layer in tropical forests.In order to develop a more comprehensive understanding of the ecological radiation that has occurred in the megadiverse Steninae, ecomorphological studies on this taxon shall be performed in the Southeast Asian tropics of northern Thailand. During a three months research stay at the entomology lab and collection of the Queen Sirikit Botanic Garden in Chiang Mai, field studies along an elevation gradient in the mountain forest of Doi Inthanon shall be performed to evaluate the ecomorphological diversity and the community structure of tropical Steninae. Since the ecology of tropical Steninae is largely unknown, these studies will provide fresh ecological, morphological, and behavioral data that can be used in further analyses of the ecomorphological radiation and niche evolution of this taxon. Focusing on the largely neglected genus Dianous, whose center of distribution is in the mountain areas between the Palaearctic and the Oriental regions south of 31° northern latitude (Indochina Peninsula and southern slopes of the Himalaya), this research is aimed at contributing to the remaining open question as to whether Stenus is paraphyletic with respect to Dianous and whether the diversity of ecomorphs observed in Dianous has arisen via a process of iterative convergent ecological radiation, which means that species flocks are produced not by single but by multiple adaptive radiations, whereupon subclades radiate across similar ecomorphs related to similar adaptive zones. A special interest will be to investigate the way that Dianous species, lacking a protrudible elongated stick-capture apparatus, capture their prey and interact with characteristic requisites of their habitat. The ecological and behavioral comparison of Dianous with Stenus species will provide important insights into the ecological consequences of the absence of an elongated adhesive prey-capture apparatus in Dianous and show to what extent the ecomorphological diversity of Stenus is actually repeatable in a convergent manner without such a specialized prey-capture device.