A preliminary survey of the non-biting midges (Diptera: Chironomidae) of the Dominican Republic

Chironomidae (Diptera) are among the most di verse and widespread aquatic insects, with roughly 5,500 described species. However, prior to the pre sent work, no species of Chironomidae had been documented from the island of Hispaniola. Collec tions of non-biting midges, with emphasis on the lotic fauna, were made in the Dominican Republic during July of 2015. In total, 578 specimens be longing to 27 genera and at least 44 species within the subfamilies Chironominae (20 taxa), Ortho cladiinae (16 taxa) and Tanypodinae (8 taxa) were found. The subfamilies Chironominae and Ortho cladiinae predominated. Polypedilum was the most widespread and diverse genus of Chironominae. Metriocnemus were collected in bromeliad tanks. The chironomid fauna in Dominican Republic in cludes multiple genera with worldwide distribu tions, including Holarctic and Neotropical compo -nents.


Introduction
Non-biting midges, belonging to the family Chironomidae (Diptera), are the most widely distributed free-living holometabolous insects (Ferrington 2008). The immature stages of most species occur in freshwater, but numerous terrestrial or marine species are known (Saether and Ekrem 2003). The adult life stage of chironomids is short, and most of the lifespan is spent as a larva. The great species and habitat diversity makes this family not only a valuable indicator species for lentic and lotic aquatic ecosystems, but also a most interesting group for phylogenetic and biogeographical analyses (Silva and Ekrem 2015). However, in order to obtain the most biologically informative data, it is crucial to determine taxa to species, since within a single genus, species may respond in a different way to environmental changes (Lenat and Resh 2001). Usually, the lack of descriptions and keys to a local fauna prevents species identifications, or workers choose to overlook the Chironomidae in favor of groups (e.g. Ephemeroptera, Plecoptera, Trichoptera) that are more restricted in number and diversity (Spies et al. 2009).
Approximately 900 chironomid species are recognized from the Neotropical region (M. Spies, personal communication). This number has been increasing in recent years thanks to intense taxonomic work being done, particularly in Brazil (e.g. Andersen and Pinho 2014, Andersen et al. 2015, Silva et al. 2014a,b, Siri and Donato 2015. Regarding Central America and the Caribbean, the chironomid fauna remains poorly known. No list of Chironomidae in Dominican Republic has been published so far and our knowledge consists basically of fossil records (Grund 2004, 2006, Perez-Gelabert 2008. Recent fauna have been sparsely mentioned by some authors. Margalef (1986), investigating the limnology of Lake Enriquillo in Dominican Republic, documented some chironomid larvae, identified only to family. Moreover, Perez-Gelabert (2008) compiled a checklist of arthropods of Hispaniola, which included chironomid species in amber and only one recent species, Chironomus redeuns Walker, considered a nomen dubium by Spies and Reiss (1996). In this context, the goal of our study was to provide data on the Chironomidae of the Dominican Republic, in order to contribute to the overall knowledge of Caribbean fauna.

Study area
Hispaniola ( Fig. 1) is the second largest island (76,480 km 2 ) in the archipelago of the Greater Antilles, Caribbean Region. It is centrally located in the Caribbean basin just south of the Tropic of Cancer at 17º40' and 19º56' North latitude and 68º20' and 72º01' West longitude. This natural geographic unit is shared by two countries with different languages and cultures, Haiti on the western one third (27,750 km 2 ) and the Dominican Repub-lic on the eastern two thirds (48,730 km 2 ) (Perez-Gelabert 2008). The Dominican shores are washed by the Caribbean to the south and the Atlantic Ocean to the north. It has a varied terrain comprising rainforest, savannah and highlands, including Pico Duarte which, at about 3100 m elevation, is the Caribbean's tallest mountain. Climate in the Dominican Republic is tropical maritime, ranging from 18 to 32°C, with relatively high humidity. Mean annual precipitation along the southeastern coast around Santo Domingo is 1,400 mm with a distinct wet season from May to October. The island has some large saline or hypersaline inland lakes. There are several smaller islands and cays that are part of the Dominican territory. A complex topography and variety of local weather patterns generate numerous microhabitats, which support a rich flora and fauna with significant numbers of endemic species (Perez-Gelabert 2008).

Collection and identification
Collections were made at 13 localities in July 2015 (Table 1, Fig. 1). Most were lotic environments, ranging from small springs to large rivers, at elevations from 20 to 2,250 m above sea level. The main emphasis was on adult sampling, collected with a sweep net near aquatic systems. Dipnets (20 cm dia, 250 μm mesh) were used to collect immatures at some localities. Samples were also taken by aspiration of the water and organisms from the central tank of bromeliads. All samples were field-preserved using 96% ethanol. In the laboratory, after initial sorting and identification, representatives of every taxon in each sample were slide mounted in Euparal for species identification following the procedure outlined by Pinder (1983Pinder ( , 1986Pinder ( , 1989. Voucher specimens will be deposited in the Museum of Comparative Zoology at Harvard University.

Results
In total, 578 representatives of three subfamilies were collected (Table 2). Twenty-seven genera have been identified, containing at least 44 species. At least two additional orthoclad species could not be assigned to any described genera. Chironominae and Orthocladiinae predominated in all samples. Tanypodinae were often sampled, but rarely in large numbers. Chironomini was represented by at least 10 genera, but species diversity was low. Except for Polypedilum, no genus was represented by more than two species. The most widespread Chironomini were Polypedilum (Asheum) beckae (Sublette) and other Polypedilum spp. Polypedilum is one of the largest chironomid genera containing about 440 described species (Saether et al. 2010). Larvae of Polypedilum occur in virtually all kinds of still and flowing waters. A few species are also found in bromeliad tanks

Discussion
At the generic level the chironomid fauna in Dominican Republic includes multiple genera with worldwide distributions with Holarctic and Neotropical components. The Neotropical component is typically an extension of the warm adapted fauna of lowland South America (Watson and Heyn 1992). At the level of species it is possible to infer that Compterosmittia croizati, known from Brazil and Venezuela (Mendes et al. 2004) and Parachironomus yanomami described from Brazil (Spies et al. 1994)  Assuming the limited duration and extension of our study, this species richness documented here is probably lower than the true richness of chironomid fauna in the Dominican Republic. Comparing our results with Ferrington et al. (1993), who sampled in a mountain stream during one year in the neighbouring island of Puerto Rico, we could expect that some species of the following genera are still found in streams of the Dominican Republic: Ablabesmyia, Corynoneura, Djalmabatista, Larsia, Paratendipes, Rheotanytarsus, Skutzia and Thienemanniella. Additional orthoclad genera were found on Saint Vincent by : Bryophaenocladius, Eurycnemus, Onconeura, Paraphaenocladius and Smittia. A study performed by Anderson et al. (2014) on San Salvador Island (Bahamas) identified only 12 chironomid species. The authors suggested that low diversity might occur on individual islands, with a much larger collective community in the Bahamas as a whole. According to Bass (2003), other important factors influencing the diversity of freshwater macroinvertebrate communities on Caribbean islands probably include climate and island dispersal capabilities or limitations of specific populations.
Although our results document a relatively small chironomid community in the Dominican Republic, we believe that collections in different periods (including both the rainy and dry seasons) and broadening the variety of sampling habitats and geographic area will reveal much greater diversity than currently detected. While recent years have seen increased activity concerning the chironomid fauna in the Neotropical region, the knowledge of the diversity and taxonomy as well as biogeography and phylogeny, especially in the Central America and Caribbean region, remains fragmentary. Thus, additional inventories are required to discover and analyse possible areas of endemism in the Greater Antilles archipelago. The present study contributes to the knowledge of chironomid fauna in the Dominican Republic and will hopefully motivate further studies in the area.