The phylogenetic relationships among selected species and genera of Mesoveliidae (Insecta: Hemiptera: Heteroptera: Gerromorpha) were investigated in a parsimony analysis of 2858 bp of DNA sequence data from the genes encoding COI + II, 16S rRNA and 28S rRNA. The resulting phylogeny showed that

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The phylogenetic relationships among selected species and genera of Gerrinae (Heteroptera: Gerridae) were investigated in a parsimony analysis of 2268 bp o f D N A sequence data from the genes encoding C O I + I1, 16S rRNA and 28S rRNA. The taxa represented 12 of 15 recognized genera of Gerrinae and with outgroup taxa from all other subfamilies of Gerridae, including three of five recognized genera of Eotrechinae, which is considered the sister-group of Gerrinae. The resulting phylogeny shows that Gerrinae is not monophyletic, since a clade comprising Gerris, Aquarius, Limnoporus, Tachygerris, Eurygerris and Gigantometra is more closely related to representatives of the subfamily Eotrechinae than to a clade comprising Limnogonus, Neogerris, Limnometra, Tenagogerris and Tenagogonus. The two currendy recognized gerrine tribes, Tachygerrini and Gerrini, were also paraphyletic, since Eurygerris was sister-group to Gigantometra, while Tachygerris was sister-group to Limnoporus + Aquarius + Gerris. Limnogonus and Neogerris were found to be strongly supported sister-taxa, and their sister-group was a clade comprising Limnometra, Tenagogerris and Tenagogonus, none o f which were monophyletic. Finally, Aquarius chilensis (Berg, 1881) was sister-group to a clade comprising Aquarius amplus (Drake & Harris, 1938), A. remigis (Say, 1832) and A. remigoides (Gallant & Fairbaim, 1993), recognized as the A. remigis species group, and the entire clade was sister-group to Gerris. Based on the phylogenetic reconstruction, we oudine possible diagnostic character combinations for a future revision o f the Gerrinae and discuss the fossil record. While some of the relationships reinstate earlier ideas, e.g., Limnogonus and Neogerris being sister groups, many others are poorly supported and poorly diagnosed, and therefore, we retain from drawing taxonomic conclusions until data is available from the remaining genera, which can support a future generic revision of the Gerrinae. The updated checklist o f species assigned to the subfamily is there fore based on the established taxonomy.

Abstract. The present study provides new data on the morphology and distribution of the labial tip sensilla of 41 species of 20 gerromorphan (sub)families (Heteroptera: Gerromorpha) obtained using a scanning electron microscope. There are eleven morphologically distinct types of sensilla on the tip of the labium: four types of basiconic uniporous sensilla, two types of plate sensilla, one type of peg uniporous sensilla, peg-in-pit sensilla, dome-shaped sensilla, placoid multiporous sensilla and elongated placoid multiporous subapical sensilla. Based on their external structure, it is likely that these sensilla are thermo-hygrosensitive, chemosensitive and mechanochemosensitive. There are three different designs of sensilla in the Gerromorpha: the basic design occurs in Mesoveliidae and Hebridae; the intermediate one is typical of Hydrometridae and Hermatobatidae, and the most specialized design in Macroveliidae, Veliidae and Gerridae. No new synapomorphies for Gerromorpha were identified in terms of the labial tip sensilla, multi-peg structures and shape of the labial tip, but eleven new diagnostic characters are recorded for clades currently recognized in this infraorder. One synapomorphy is recorded for Hydrometridae + Hermatobatidae + Macroveliidae + Veliidae + Gerridae; five for Macroveliidae + Veliidae + Gerridae; one for Veliidae + Gerridae; and one for Gerridae alone. Within Gerridae, one possible autapomorphy is recorded for Trepobatinae, and two possible autapomorphies for Rhagadotarsinae. We also record a possible autapomorphy for Cylindrostethinae, which indicates that this taxon is monophyletic, as is indicated by other morphological characters. Finally, we record one putative diagnostic character for Macroveliidae + Veliidae, two families that are otherwise not considered sister groups. This new set of characters based on features of the mouthparts of gerromorphan bugs might provide new insights into the cladogenesis of the infraorder.

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