A new surface gliding species of Chironomidae: An independent invasion of marine environments and its evolutionary implications

Abstract

Insects have invaded marine habitats only rarely and secondarily. Recently, we discovered a flightless dipteran species skating rapidly on the surface of seawater ponds at the Pacific coast of eastern China. Morphological analyses initially suggested an isolated position of the non‐biting midge, suggesting the erection of a new genus within Chironomini (Diptera: Chironomidae). However, an analysis of molecular data revealed that the marine species is in fact nested within the species‐rich genus Dicrotendipes. The apparent conflict between molecular and morphological data can be easily explained. It is likely that the new species has evolved a series of autapomorphic adaptations. These traits clearly distinguish the taxon from other species of the genus but do not justify the erection of a new supraspecific taxon, which would render Dicrotendipes paraphyletic. The switch to marine environments was likely a trigger for various morphological modifications resulting from increased selective pressure. Molecular data suggest that the potential speciation event occurred around 19–29 Ma, linked with a migration from freshwater to seawater ponds along the Pacific Ocean. Considering the results of our analysis, we place the flightless marine skater in the genus Dicrotendipes. All life stages of Dicrotendipes sinicus Qi & Lin sp. n. are described and illustrated, associated with larvae obtained by rearing or confirmed through association with DNA barcodes. The biology and ecology of the species are outlined based on collection data and in situ observations. Evolutionary patterns linked with repeated invasions of marine habitats are discussed.

The evolution of marine dwelling in Diptera

“…WoRMS contains an ongoing list of marine dipterans, but relies entirely upon published literature and the scientific community to self‐report ecological descriptions of species. Some groups with well‐known marine life history such as Thoracochaeta (Sphaeroceridae: Limosiinae; (Marshall, 1982 ; Hodge et al., 2017 )), Oedoparena (Dryomyzidae; (Gibson & Choong, 2021 )), Telmatogeton (Chironomidae: Telmatogetoninae; (Brodin & Andersson, 2009 ; Lorenz Simões et al., 2020 ; Nondula et al., 2004 )), Thalassomya (Chironomidae: Telmatogetoninae; (Qi et al., 2019 )), and Tanytarsus (Qi et al., 2019 ) were missing from the overall list of marine species in WoRMS. Similarly, genera like Fucellia (Anthomyiidae: Anthomyiinae; (Kaczorowska, 2005 )) and Pontomyia (Chironomidae: Chironominae; (Huang & Cheng, 2011 )) were given marine designations in WoRMS as a family but were not among the taxa examined in the fly tree of life (Wiegmann et al., 2011 ).…”

Morphology lies: a case-in-point with a new non-biting midge species from Oriental China (Diptera, Chironomidae)

“…The case is not unique in Chironomidae: the marine species Dicrotendipes sinicus Qi & Lin was suggested as a new genus within the subfamily Chironominae. However, the analysis of genetic data revealed that the marine species nested within the genus Dicrotendipes (Qi et al 2019).…”

Diversity of culicomorphan dipterans in the Eocene Kishenehn Konservat-Lagerstätte (Montana, USA) and its palaeoecological implications

“…Nevertheless, the rather unusual combination of the morphological characters of the adult males of the species indicates that they might have been surface-skimmers, as are a number of extant representatives of Chironomidae (Qi et al, 2018). Prominent characters of H. noncatafractata that point towards a surface skimming lifestyle include shortened antennae, robust and widened legs (especially femora) and relatively short wings.…”

“…These traits are exhibited by midges inhabiting the intertidal zone of the seas or living as a surface skater in hypersaline habitats (Armitage et al, 1995;Qi et al, 2018) with salinities up to 40‰ (Armitage et al, 1995;Qi et al, 2018;Shadrin et al, 2019). In the new species, these traits are less developed than in the known intertidal and marine representatives of Chironomidae, i.e., Pontomyia spp., Clunio spp., Dicrotendipes sinicus Qi and Lin, 2018 and Baeotendipes noctivagus Kieffer, 1911(Qi et al, 2018. It is therefore probable that this combination of traits indicates that adults of H. noncatafractata sp.…”