Paraphyly of the subgenus Micronecta (Micronecta) Kirkaldy, 1897 (Hemiptera: Heteroptera: Micronectidae) based on mitochondrial genomes and nuclear rDNAs

The genus Micronecta Kirkaldy, 1897 is the most species-rich genus in the family Micronectidae, containing more than 160 species. Micronecta is currently divided into 11 subgenera, five of which are monotypic. Moreover, the subgenus Micronecta is an empirical mixture group. The definitions of some subgenera were based on only a few aberrant morphological features, which are specializations with few phylogenetic significances. The relationship between these subgenera remains unclear. In this study, we newly sequenced mitochondrial genomes (mitogenomes) and nuclear rDNAs (nrDNAs) for 13 Micronecta species, representing seven subgenera, and those for ten other water bugs. Our phylogenetic analyses showed that the subgenus Lundbladella represents the sister group to all other studied subgenera of Micronecta. The subgenus Unguinecta was the sister group to the clade that contains Dichaetonecta and Sigmonecta. More importantly, the subgenus Micronecta represents a paraphyletic group, which further forms a monophyletic group together with the subgenera Basileonecta and Ctenonecta. This is for the first time that the phylogeny of the genus Micronecta was investigated based on molecular data and the paraphyly of the subgenus Micronecta was revealed. Such evidence suggested the necessity of the revision of the taxonomic system of the genus in the future, and may also serve as a reference for the delimitation of subgeneric characters.