Mosquito Distribution in Northwestern Russia: Species of the Genera Anopheles Meigen, Coquillettidia Dyar, Culex L., and Culiseta Felt (Diptera, Culicidae)

Records of 16 species of the mosquito genera Anopheles, Coquillettidia, Culex, and Culiseta (Diptera: Culicidae) in Northwestern Russia are mapped. The values of the sum of active temperatures above 0°C were shown to correlate with the position of the northern range boundaries of mosquito species, according to which 16 species were included in 4 distribution groups.

In this article we continue the study of bloodsucking insects in NWR, which has been carried out at the Zoological Institute of the Russian Academy of Sciences (ZIN) since 2005. First, we made a general outline of the regional faunas of mosquitoes, blackflies (Simuliidae), horseflies (Tabanidae), and biting midges (Ceratopogonidae) (Medvedev et al., 2007); then mosquito distribution was considered in greater detail (Aibulatov and Khalin, 2019;Aibulatov et al., 2020;Aibulatov, 2020, 2021).
During further analysis of the northern range boundaries we have mapped the records of 16 mosquito species of the genera Anopheles, Coquillettidia Dyar, 1905, Culex, andCuliseta Felt, 1904 in the whole territory of NWR. In this article we examine all the species of Culicidae present in the NWR fauna, with the exception of Aedes species. We use our earlier data ), e.g., the results of identification of the material collected by S.V. Aibulatov and A.V. Khalin and revision of the ZIN collection. In addition, it includes analysis of additional literature for some regions of NWR.
The coordinates of the collection localities of each species were entered in a *.shp file and analyzed using an ArcGIS 10 software. In addition, the file included data on the source of information: our collections, ZIN collection, and literature data. The geographic information system (GIS) is useful for analysis of the records of bloodsucking insect species and description of their geographic distribution. For instance, the mapped species records can be combined with various thematic maps (e.g., climatic ones), containing the original parameters in the given points of the territory or interpolated results based on analysis of the distribution of factors. In this way, the known collection localities of a given species can be used to extrapolate its range boundaries in the region.
Mosquitoes are poikilothermic animals whose metabolism and phenology directly depend on the environmental conditions; therefore, they can exist only within a certain range of environmental factors. In the article, the records of mosquito species were related to a climatic parameter, the sum of active temperatures above 0°C (SAT) 3 . The benefis of using SAT in the study of mosquito distribution had been noted earlier (e.g., Yasyukevich et al., 2017Yasyukevich et al., , 2019. Various climatic parameters are considered when predicting the changes in the distribution of agents of transmissible diseases and of their vectors (Pavlovsky, 1964;Korenberg, 1975). In medical entomology and practical epidemiology, thermal parameters are used to control malaria and other diseases in a given territory (Beklemishev et al., 1949;Moshkovsky and Rashina, 1951). The pest control measures in agriculture is determined by the thermal parameters of insect pest development (Popova and Popov, 2013).
In this research we used the free data on the main climatic factors available at the AgroAtlas web site (Afonin et al., 2008) in order to characterize the mosquito distribution in NWR in relation to the environmental parameters. The records of mosquito species close to the northern boundaries of their ranges were compared with the SAT values of the corresponding territories, and the results were used to extrapolate the northern distribution boundaries of 16 species of Culicidae within NWR. We used the SAT values for areas of 100 km 2 , obtained from the AgroAtlas web site (Afonin et al., 2008). The SAT values were color coded from green to red (see map legend in Fig. 2).
Below, the records of 16 mosquito species are plotted on the map of NWR with SAT values. The source of information is indicated for each species: our collections, the ZIN material or literature data.
The northernmost records of mosquito species within NWR, including the exact collection localities and their coordinates, were considered in our earlier paper (Khalin and Aibulatov, 2021). The records of mosquitoes from the territories with the minimal SAT values are listed in Table 1. The number of such records given for each species reflects the current level of knowledge of its distribution. A single locality corresponding to the territory with the lowest SAT value is given in some cases: Anopheles atroparvus, Culiseta fumipennis, and C. annulata. For most species, two localities are given, in the western and the eastern parts of NWR. For example, such localities for Anopheles beklemishevi are RK in the west and Komi in the east of NWR. For the species whose distribution is somewhat better known, three localities are listed in order to describe the northern range boundary more correctly; for example, the localities of Anopheles claviger are SPb (western part), VP (central part), and Komi (eastern part). Some records of species are considered by us to be doubtful; they are marked with asterisks (*) and discussed in the corresponding Note sections.
Maps of NWR showing the collection localities of the 16 mosquito species are given below. For each species, the examined material (our collections and the ZIN collection) is listed when present, its distribution in NWR and adjacent territories is characterized, and references to the sources of data are provided. In addition, the distribution of each species outside NWR is briefly described based on the literature data (Gutsevich et al., 1970;Khalin and Gornostaeva, 2008;Becker et al., 2010). The records for Belarus are based on the data of Suslo (2019); those in Europe 4 are based on the data of Robert and co-authors (Robert et al., 2019). The distribution of Culiseta species in Russia outside NWR is based on the data of Maslov (1967).
European Russia, Siberia. Europe (ranging northward to the UK, Belgium, and Denmark); Belarus, Ukraine, Moldova, Middle Asia, Northeast China.
Note. The only specimen studied by us is a head preparation of a female mosquito identified earlier by A.V. Gutsevich. We cannot confirm this identification. It is possible that the female was reared from an egg identified as Anopheles messeae.
European Russia, Siberia, the Russian Far East. Europe (ranging northward to the UK, the Netherlands, and Denmark); North Africa, Belarus, Ukraine, Moldova, Transcaucasia, West, Middle, and South Asia.
European Russia, West Siberia. Europe (ranging northward to the UK, Belgium, and Denmark); North Africa, Belarus, Ukraine, Moldova, Asia Minor, Kazakhstan, Middle Asia.

DISCUSSION
Analysis of additional publications has allowed us to correct the mosquito check-list in NWR, currently comprising 47 species; the list was supplemented with Anopheles atroparvus, recorded in KP (Levenson et al., 1959). In the course of the examination of the records of species of the genera Anopheles, Coquillettidia, Culex, and Culiseta in comparison with the SAT parameter, the minimal SAT values for each species within NWR were determined (Table 2) and the position of the northern range boundaries of these species was analyzed. Based on our material and the ZIN collections, the northern distribution boundaries in NWR were updated for five species: Anopheles claviger, A. messeae, Culiseta morsitans, Culex territans, and C. modestus. Based on the minimal SAT values, species of the genera Anopheles, Coquillettidia, Culex, and Culiseta were included in four groups (Fig. 17).
Group 1. Three species: Culex pipiens, Culiseta alaskaensis, and C. bergrothi. These species are distributed in the area with SAT values exceeding 770°C (i.e., the whole territory of NWR excluding the north and east of Group 2. Nine species, including 3 species of group 1 and also Anopheles beklemishevi, A. maculipennis, A. messeae, Culex territans, Culiseta morsitans, and C. ochroptera. These species are distributed in the area with SAT values exceeding 1227°C (i.e., the territory of NWR excluding the greatest parts of MP and NAO and the north and east of the Komi Republic; see Fig. 17). The northernmost locality of Culiseta morsitans differs considerably from those of the remaining species in a lower SAT value (see Table 2). The records with SAT 1577.2°C are probably located near the northern distribution boundary of Anophelinae mosquitoes in NWR; as compared with this value, the record of an Anopheles mosquito in MP (Shuioniioki River, SAT 1136.4°C) is quite unexpected.
Group 3. Thirteen species: all the examined species excluding Anopheles atroparvus, Culex modestus, and Culiseta annulata. Mosquitoes of this group are distributed in the area with SAT values exceeding 1733°C (KP, LP, south of RK, AP, Komi, VP, PP, and NP). Coquillettidia richiardii is the only species of its genus in the North Palaearctic; correspondingly, the locality with a SAT value of 1966.7°C probably lies at the northern distribution boundary of the genus Coquillettidia in NWR. Mosquitoes are amphibiotic insects whose larvae and pupae develop in temporary and permanent water bodies, while the adults are terrestrial. The larvae and adults of most mosquito species are not trophically specialized to any plant or animal species; therefore, the ranges of species of the family Culicidae do not directly follow those of other organisms. The distribution of some mosquito species may be limited by the presence of water bodies suitable for their larvae. NWR occupies a large territory with a total area of over 1.5 mln km 2 , diverse climatic conditions, and a wide range of ecozones, from Arctic deserts to mixed forests. At the same time, in NWR there are no large arid or highland regions which could prevent the spreading of mosquitoes. Consequently, the SAT value in the collection locality appears to be an adequate climatic parameter reflecting the main features of the life cycle of mosquito species.
NWR includes some territories with relatively wellstudied faunas of mosquitoes (e.g., MP, RK, SPb, and Komi) and also regions poorly studied in this respect (KP, AP, and NAO). In some cases, comparison of the northern distribution boundaries and the corresponding SAT values may be used to extrapolate the range boundary onto still unstudied territories. For example, the records of Culiseta bergrothi in the north of MP and the northeast of Komi (SAT 848.3°C) indicate that the species may be distributed over the largest part of NAO and AP. The records of Culiseta morsitans in MP and Komi Each group includes all the species of the former group, i.e., group 2 includes group 1; group 3 includes groups 1 and 2; group 4 comprises all the 16 mosquito species.
(SAT 1227.8°C) indicate that the species may also occur in the continental parts of AP and VP, while the records of Coquillettidia richiardii in RK and Komi (SAT 1966.7°C) suggest its presence in VP.
The northward expansion of a mosquito species may be limited not only by the number of days with a temperature sufficient for its preimaginal development and adult activity, but also by the low winter temperatures eliminating the insects during diapause. Most mosquitoes distributed in the high latitudes of the Holarctic (e.g., Aedes species) overwinter in the egg stage, but the northernmost species considered herein, Culiseta alaskaensis and C. bergrothi, diapause as adult females; yet this feature does not prevent them from spreading as far northwards as the Barents Sea coast.

CONCLUSIONS
Comparison of the species records and the SAT values for the collection localities was used to extrapolate the northern distribution boundaries of mosquito species in NWR. The northern range boundaries in different mosquito species were found to vary significantly within

COMPLIANCE WITH ETHICAL STANDARDS
The authors declare that they have no conflict of interest. All the applicable international, national, and/or institutional guidelines for the care and use of animals were followed. All the procedures performed in studies involving animals were in accordance with the ethical standards of the institution or practice at which the studies were conducted.

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