A phylogenetic analysis of Adephaga is presented. It is based on 148 morphological characters of adults and larvae and focussed on a placement of the recently described Meruidae, and the genus-level phylogeny of the smaller aquatic families Gyrinidae, Haliplidae and Noteridae. We found a sister group relationship between Gyrinidae and the remaining adephagan families, as was found in previous studies using morphology. Haliplidae are either the sister group of Dytiscoidea or the sister group of a clade comprising Geadephaga and the dytiscoid families. Trachypachidae was placed as the sister group of the rhysodid-carabid clade or of Dytiscoidea. The monophyly of Dytiscoidea including Meru is well supported. Autapomorphies are the extensive metathoracic intercoxal septum, the origin of the metafurca from this structure, the loss of Mm. furcacoxalis anterior and posterior, and possibly the presence of an elongated subcubital setal binding patch. Meruidae was placed as sister group of the Noteridae. Synapomorphies are the absence of the transverse ridge of the metaventrite, the fusion of abdominal segments III and IV, the shape of the strongly asymmetric parameres, and the enlargement of antennomeres 5, 7 and 9. The Meru-noterid clade is the sister group of the remaining Dytiscoidea. The exact position of Aspidytes within this clade remains ambiguous: it is either the sister group of Amphizoidae or the sister group of a clade comprising this family and Hygrobiidae + Dytiscidae. The sister group relationship between Spanglerogyrinae and Gyrininae was strongly supported. The two included genera of Gyrinini form a clade, and Enhydrini are the sister group of a monophylum comprising the remaining Enhydrini and Orectochilini. A branching pattern (Peltodytes + (Brychius + Haliplus)) within Haliplidae was confirmed. Algophilus, Apteraliplus and the Haliplus-subgenus Liaphlus form a clade. The generic status of the two former taxa is unjustified. The Phreatodytinae are the sister group of Noterinae, and Notomicrus (+ Speonoterus), Hydrocoptus, and Pronoterus branch off successively within this subfamily. The search for the larvae of Meru and a combined analysis of morphological and molecular data should have high priority.
No abstract
Abstract. An unknown beetle collected in the Territorio Federal Amazonas, Venezuela, and designated as belonging to a new family, is described (as Meru phyllisae gen.n., sp.n.) and illustrated by line drawings and scanning electron micrographs. The new family, Meruidae, is diagnosed and assigned to the suborder Adephaga with a discussion of some characters and likely phylogenetic affinities. With a body length of 0.85-0.9 mm, M. phyllisae is the smallest known member of aquatic Adephaga. Based on the observed skeletal and behavioural characters to date, the taxon appears to represent the sister clade to the remaining families of Dytiscoidea, but also has features suggesting a close relationship among Noteridae and/or Haliplidae. A description and photographs of the habitat are included, with a list of other associated water beetle taxa. Some observations on the behaviour of captive beetles are given. The minute 'comb-clawed cascade beetles' are known only from the type locality, El Toboga´n, where streams flow among exposed areas of bedrock in the geologically ancient Guyana Shield region.
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