All known records of aquatic dance flies (Empididae, Clinocerinae: 21 species; Hemerodromiinae: eight species) from the island of Corsica (France) are summarized, including previously unpublished data and data on the newly described species Chelipoda puschae Ivković, Perović & Grootaert, sp. nov. This species was collected during the “La Planète Revisitée Corsica 2019” survey and represents the first description of a new species in the genus Chelipoda from the European–Mediterranean region in more than 180 years. A key to European species of Chelipoda is provided. Including the new species, five species are recorded from Corsica for the first time: Dolichocephala malickyi Wagner, 1995, Dolichocephala oblongoguttata (Dale, 1878), Dolichocephala ocellata (Costa, 1854), Chelifera subangusta Collin, 1961, and Hemerodromia unilineata Zetterstedt, 1842. The new species is described and illustrated, and new records of aquatic dance flies from Corsica are given, with new data on 17 species in eight different genera. At present, 29 species of aquatic dance flies are known from Corsica, with 10 species endemic to the island.

Distribution, Empididae, endemicity, new species, Our Planet Reviewed expedition

The island of Corsica is situated in the Tyrrhenian Sea, about 170 km south of mainland France, about 90 km west of Italy, and separated from Sardinia by the Strait of Bonifacio. Mountains cover about two-thirds of the island, forming a single chain that runs in a north–south direction. Corsica is one of the most important centres of endemism for freshwater invertebrates in Europe (Giudicelli 1975; Ketmaier and Caccone 2013). In terms of its area of about 8700 km², the concentration of endemic species on Corsica is one of the highest in Europe, with most of the endemic species located in spring brooks and streams at higher altitudes (Giudicelli 1975).

The aquatic Empididae (Hemerodromiinae and Clinocerinae) of Corsica have previously been studied on a number of occasions (Becker et al. 1910; Vaillant 1965, 1982; Wagner 1995). Becker et al. (1910) and Vaillant (1965, 1982) described, in total, three new species of aquatic dance flies from the island. Pusch (1996) provided the most detailed study of the Clinocerinae of Corsica, describing six new species. At present 23 species of aquatic dance flies are known from Corsica (Becker et al. 1910; Vaillant 1964, 1981; Wagner 1995; Pusch 1996), with nine endemics (Yang et al. 2007).

Both larval and adult aquatic Empididae are predators, mainly feeding on smaller aquatic dipterans such as Chironomidae, Simuliidae, and Psychodidae (Vaillant 1952, 1967; Harkrider 2000; Werner and Pont 2003; Ivković et al. 2007; Ivković and Plant 2015). Adult Hemerodromiinae are easily distinguished from adult Clinocerinae by their raptorial forelegs. They live and hunt in riparian vegetation, whereas adult Clinocerinae are primarily found on the surface of emergent wet stones or in moss mats (Ivković et al. 2007; Sinclair 2008).

Distribution and biodiversity studies are crucial for an understanding of the drivers of biodiversity hotspots (Ivković and Plant 2015; Schmidt-Kloiber et al. 2017). Regional distribution and biodiversity surveys are important for defining the biogeographic distribution of certain species or genera. They also contribute to the study of the various factors that influence changes in biodiversity and that subsequently affect the species conservation status (Meyer and Wagner 2011; Ivković et al. 2013a, 2017, 2020; Shamshev and Ivković 2020).

In this paper, we present new records of aquatic dance flies from Corsica (France) and also describe a new species. Detailed distribution data are presented, all resulting from the examination of specimens collected at 26 sites, sampled during the “La Planète Revisitée Corsica 2019” survey in June 2019.

The following format is used for the distribution data: Material examined: number of males (♂) and/or females (♀), locality and location name, description of sampling site, collection date or period, collecting method (sampling site ID, see Table 1). Species recorded for the first time for Corsica (France) are indicated with “*” in front of the species names. A full list of sampling sites is given in Table 1.

Species richness and assemblage composition

So far, 29 species of aquatic empidids are recorded from Corsica, France (Table 2). New data on 16 species (12 Clinocerinae and four Hemerodromiinae) and one new hemerodromiine species, Chelipoda puschae sp. nov., were retrieved from samples collected at 26 sites during the “La Planète Revisitée Corsica” survey in June 2019 (Fig. 1; Table 1). The subfamily Clinocerinae is represented by 21 species (72%), in five genera: Clinocera Meigen (3 species), Clinocerella Engel (2 species), Dolichocephala Macquart (4 species), Kowarzia Mik (5 species), and Wiedemannia Zetterstedt (7 species). The subfamily Hemerodromiinae is represented by eight species (28%), in three genera: Chelifera Macquart (4 species), Chelipoda Macquart (3 species), and Hemerodromia Meigen (1 species) (Table 2). The clinocerine genus Wiedemannia is the most species-rich (24% of the total number of aquatic empidids on the island), followed by Kowarzia (17%) and the genera Dolichocephala (14%) and Chelifera (14%) (Fig. 6).

Figure 6. 

Species richness of aquatic Empididae genera (Diptera: Empididae, Clinocerinae, Hemerodromiinae) on Corsica (total number of species: Clinocera – 3 species; Clinocerella – 2 species; Dolichocephala – 4 species; Kowarzia – 5 species; Wiedemannia – 7 species; Chelifera – 4 species; Chelipoda – 3 species; Hemerodromia – 1 species).

The proportion of endemic species of aquatic empidids in Corsica, i.e. species that have so far only been found in Corsica and that are believed to occur only there, is 35% (10 species discussed here). In addition, Clinocerella gereckei (Wagner & Horvat, 1993) also occurs on Sardinia (Italy). Among Corsican species, 28% are widespread European species, 7% are Central European. A single South European species is recorded, Kowarzia barbatula (Mik, 1880). Dolichocephala ocellata (Costa, 1854) and Kowarzia bipunctata (Haliday, 1833) are considered European–Mediterranean (7% of species discussed here), while Dolichocephala malickyi Wagner, 1995, Wiedemannia czernyi (Bezzi, 1905), and Chelifera barbarica Vaillant, 1981 are Mediterranean species (10% of all species). Clinocera nigra Meigen, 1804 is a Western Palaearctic species and Clinocera stagnalis (Haliday, 1833) a Holarctic species (Fig. 7).

Figure 7. 

Zoogeographic classification of aquatic empidid species (Diptera, Empididae, Clinocerinae and Hemerodromiinae) currently known from Corsica.

Ten (35%) of the aquatic Empididae recorded from Corsica thus far are considered strictly endemic to the island, and slightly over 40% of the Corsican aquatic empidids are known from other parts of Europe as well (all through Europe, Central Europe, or Southern Europe). The remaining 25% of the species are either widely distributed (Holarctic, Western Palaearctic) or are confined to the Mediterranean area. We compared our list of Corsican species with the existing records of species in Becker et al. (1910), Vaillant (1965, 1982) Wagner (1995), Pusch (1996), Chvála (2012), and Yang et al. (2007). The following six species were not previously recorded from Corsica and represent the first published records: Dolichocephala malickyi Wagner, 1995, D. oblongoguttata (Dale, 1878), D. ocellata (Costa, 1854), Chelifera subangusta Collin, 1961, Hemerodromia unilineata Zetterstedt, 1842, and Chelipoda puschae Ivković, Perović & Grootaert, sp. nov. Moreover, this is the first description of a species of Chelipoda from the European–Mediterranean region for more than 180 years.

Of the two subfamilies, the Clinocerinae have a greater species richness in Europe, especially in mountainous areas (Vaillant 1982; Horvat 1995; Ivković et al. 2012, 2013a, 2013b, 2014, 2017, 2020). This agrees with the pattern observed in Corsica and might be explained by the central mountain chain on the island. Likewise, Wiedemannia represents the most speciose genus, both in Corsica and on the continent. By contrast, Chelifera is usually the second most species-rich genus (Meyer and Wagner 2011; Ivković et al. 2013a, 2013b, 2017, 2020), but in Corsica it is replaced by Kowarzia. A higher diversity of Kowarzia is usually only present in mountain regions (Ivković et al. 2014).

The aquatic Empididae fauna of Corsica is composed of exclusively Western Palaearctic taxa with the exception of Clinocera stagnalis (Haliday, 1833), which is the most widespread Holarctic clinocerine (also known from North America, North Asia, and North Africa) (Sinclair 2008). Most of the Corsican species are restricted to the Central European or Mediterranean regions. However, 10 of the species encountered in Corsica are strictly confined to the island and can therefore be termed endemic. Only five species are shared with the island of Sardinia (Wagner and Horvat 1993; Wagner 1995). We believe that the current species list is far from complete. Indeed, there has not yet been a comprehensive study of Corsica and all of its freshwater habitats. Furthermore, sampling efforts during the “La Planète Revisitée” were restricted to a short period in late spring and only samples from pan traps and sweep net collecting were examined. Some obvious genera such as Bergenstammia and Phaeobalia are currently absent from the list. Species in these genera are usually found on the continent only above 1,000 m a.s.l., and as most of Corsica is montane, it is our belief that more species, including more endemics, are likely to be found in Corsica. Most endemic freshwater insect species in Corsica are restricted to higher altitudes (500–1,900 m) (Giudicelli 1975). The influence of altitude and isolation on biodiversity processes is more marked in Corsica, with 30 peaks exceeding 2,000 m, than in, for example, Sardinia where the highest mountain is only 1,830 m. This could explain, in part, why Corsica has a seemingly higher overall species richness than Sardinia, including aquatic empidids (only nine species), even though Sardinia is almost triple the size of Corsica (Giudicelli 1975; Chvála 2012). When it comes to aquatic empidids, we have to bear in mind that they may have been collected only sporadically in Sardinia, mostly as a side catch during inventories of other aquatic groups (Wagner 1984, 1995; Wagner and Horvat 1993). Comparisons between the aquatic empidid faunas of Corsica and Sardinia must therefore be made with the utmost caution. However, the greater species richness in Trichoptera, a group with a similar ecological profile to aquatic empidid flies, also suggests a richer fauna in Corsica, with more endemic species in Corsica than in Sardinia (Giudicelli 1975). In addition, most endemics are found at higher altitudes in Corsica than at lower altitudes (Giudicelli 1975). Katmaier and Caccone (2013) have stated that Corsica is faunistically impoverished when compared to continental resources. Our results, on the contrary, suggest otherwise as the number of aquatic empidids is quite high, especially considering the limited sampling efforts. It has been assumed that most of the endemic species that now occur in Corsica have differentiated from ancestors on the Iberian Peninsula (Katmaier and Caccone 2013). In aquatic empidids, however, this might not be the case, as most of the species present are shared with Central and Southern Europe and only a minority is shared with the Iberian Peninsula, but detailed morphological and/or genetic studies could confirm or reject this assumption. It is postulated that during the Messinian Salinity Crisis, the Mediterranean Sea almost completely dried up and a number of freshwater species reached Corsica through an area of braided rivers present all over the Mediterranean and connecting Corsica to the European continent (Katmaier and Caccone 2013).

To conclude, we hope that this paper will assist in the understanding of our present-day knowledge of the aquatic empidids of Corsica and will provide a starting point for further, more detailed and comprehensive studies, as well as additional studies in Sardinia where the aquatic dance fly fauna is poorly known.

The material examined during this study was collected during the expedition “Our Planet Reviewed” – Corsica 2019–2021. This survey was organized by the Muséum national d’Histoire naturelle (MNHN) in collaboration with and funded by the Collectivité de Corse (CdC) and the Office français de la biodiversité (OFB) (previously known as the Agence française de la biodiversité – AFB). We are also grateful to the different logistic partners who assisted with field work in 2019: the communes of Alta Rocca (Serra di Scopamène, Zonza and Zicavo) and Tartagine (Olmi-Capella and Mausoléo), the Office de l’Environnement de la Corse (OCIC et CBNC), the Direction Régionale de l’Environnement de l’Aménagement, the Direction du Logement (DREAL) and the Office National des Forêts (ONF). Special thanks are due to the mayor of the village of Serra di Scopamène, Mr Jean-Paul Roccaserra; the “Communauté de Communes de l’Alta Roca” and its Écogardes provided the necessary infrastructure and invaluable support during the expedition. MP participated in the fieldwork in June 2019 and is much indebted to the leaders of the expedition, Dr Julien Touroult and Dr Olivier Pascal, and to the entire research team for the great company which made this a unique survey. We would like to thank Dr Igor Stanković for his help with the ArcGIS software and production of the map. We would like to thank Dr Adrian C. Pont for checking the English language. We are especially grateful to reviewers for improving the manuscript with their helpful comments and corrections.