On the evolution of adult head structures and the phylogeny of Hydraenidae (Coleoptera, Staphyliniformia)

Abstract

External and internal head structures of adults of Orchymontiinae, Prosthetopinae, Hydraeninae and Ochthebiinae were studied and those of Ochthebius semisericeus and Limnebius truncatellus are described in detail. The results are evaluated with respect to their relevance for a reconstruction of hydraenid phylogeny and also compared with structural features found in adults of other staphyliniform families. The monophyly of Hydraenidae is supported by the presence of a plate-like, trilobed premento-hypopharyngeal extension, an unusual origin of m. tentoriohypopharyngalis, dorsal tentorial arms firmly fused with the head capsule, modified basal antennomeres, and palpigers connected by a transverse sclerotized bar. Orchymontiinae are monophyletic and the basal sister group of the remaining Hydraenidae. The presence of a ventral transverse genal bulge and of a pubescent antennal club with more than two antennomeres (reversal in some prosthetopines: e.g. Mesoceration abstrictum) are possible apomorphies of Hydraenidae excluding Orchymontiinae. Prosthetopinae are probably monophyletic and the sister group of Ochthebiinae + Hydraeninae. The latter clade is characterized by a distinct cupula formed by antennomere VI, a loose five-segmented pubescent antennal club, and a modified antennal musculature. The presence of an unusual tentorio-pharyngeal dilator is a shared derived feature of Ochthebiinae and the genus Davidraena. The monophyly of Ochthebiinae was confirmed and Ochtheosus is the sister group of the remaining ochthebiine genera, which are characterized by a perforated wall-like structure formed by the posterior tentorial arms. The absence of this tentorial modification and the fimbriate galea are plesiomorphies retained in Ochtheosus. Calobius differs strongly from other subgenera of Ochthebius and a generic status may be appropriate. The monophyly of Hydraeninae is not supported. Hydraena was confirmed as a clade and Laeliaena and Limnebius are sister groups. The latter genus is characterized by several autapomorphies. The basal position of Orchymontiinae and Prosthetopinae suggests a Gondwanan origin of Hydraenidae and a primary preference for life in running water. Important evolutionary changes of head structures are complex transformations of the antennae and related structures. Yet, the use of the antennae as accessory breathing organs is not a groundplan feature of the family. The results of this study strengthen the case of staphylinoid affinities of Hydraenidae.

Description of the larval stages of Gymnochthebius jensenhaarupi and phylogenetic analysis of the relationships with other species of the subfamily Ochthebiinae (Coleoptera: Hydraenidae)

“…In this sense, larval morphology is consistent with recent studies based on adult morphology (Beutel et al, 2003;Perkins, 1997).…”

“…The present analysis suggests that members of this clade have accumulated a high number of apomorphic character states during the evolution of the subfamily Ochthebiinae (five larval characters). Both this close relation and their derived placement within Ochthebiinae, has been suggested previously in other studies dealing with both adult (Perkins, 1997;Beutel et al, 2003) and larval morphology (Delgado & Soler, 1996a). Our results reinforce these ideas, but conflict with the taxonomic status given by Perkins (1997) to these subgenera.…”

“…The larva of Limnebius cordobanus d'Orchymont, 1938 (Delgado & Soler, 1997c) was used as the outgroup. Since the monophyly of the ingroup is not in doubt (Beutel et al, 2003, Perkins, 1997 we used only one outgroup. However, several character comparisons were made with the larvae of Hydraena hernandoi Fresneda & Lagar, 1990 (Delgado & Soler, 1996b) and Podaena latipalpis Ordish, 1984 (Delgado & Palma, 2004).…”

“…Hansen (1991) pointed out morphological similarities between adults of Gymnochthebius and Aulacochthebius Kuwert, 1887, but it was Perkins (1997) who explicitly postulated a close phylogenetic relationship between both genera (along with Gymnanthelinus Perkins, 1997) in a lineage comprising also the genera Ochthebius, Hughleechia Perkins, 1981 andMicragasma Sahlberg, 1900 within the subfamily Ochthebiinae. Unfortunately, this close phylogenetic relationships could not be tested in Beutel et al (2003) since these authors did not include Aulacochthebius in their cladistic study.…”

Molecular and morphological evidence of a new sibling species ofCalobius(Coleoptera: Hydraenidae) of theC. quadricolliscomplex from peninsular Italy

“…is the second largest genus within Hydraenidae, and includes nearly 400 species worldwide (Hansen 1991). The small western Palaearctic subgenus Calobius (Wollaston 1854) was the object of a series of recent discussions, considering this group as either a distinct separate genus or subgenus (Jäch 1993(Jäch , 2004Delgado & Soler 1997;Perkins 1997;Beutel et al 2003). The taxonomic position of Calobius will be discussed in a paper to follow, where other relevant morphological apomorphic characters as well as molecular data will be presented (Audisio et al unpublished data).…”