Helophorus shatrovskyi, Angus, 1985

Enkhnasan, Davaadorj & Boldgiv, Bazartseren, 2019, Endemic and sub-endemic water beetles of Mongolia and their distribution ranges, Journal of Species Research 8 (4), pp. 395-406 : 402-404

Helophorus shatrovskyi Angus, 1985 ( Fig. 7 )

Diagnosis. Body length: 2.5 - 2.7 mm; breadth: 1.2 - 1.3 mm.

General form: robust, highly arched.

Head: shining dark green with bronze reflections, the surface granulates. Y-groove shining golden bronze stems linear, floor rugulose. Maxillary palpi yellowish brown, the apical segment symmetrical oval. Antennae 9-segmented, yellowish, the clubs a little darker. Pronotum: highly arched and domed, the inner edges of the internal intervals depressed towards the mid groove. Raised lateral margins distinct. Elytra: yellowish brown, strongly striate, the interstices convex, narrower than the striae. Widest point just behind the middle, the sides curved, the apex bluntly rounded. Flanks broadly visible from below. Legs: rather short, tarsal swimming hairs weak ( Angus, 1985).

Published records. Angus, 1985:163 - Töv.

Remarks. Helophorus shatrovskyi Angus, 1985:163 [Holotype ♂ (Department of Zoology, University of Halle): Mongolia, Bayankhongor, 23.vii.1982. leg. H.-J. Altner].

A list of 13 sub-endemic species is given in Table 2. In total, 21 species that are considered as endemic or sub-endemic water beetles belonging to seven genera in four families of total seven beetle families make up 12.4% of the all water beetle species recorded in Mongolia ( Table 1). The majority of endemic and sub-endemic water beetles of Mongolia is represented by Dytiscidae (10 spp.), which comprises about 47.6% of the total endemic and sub-endemic species. Other three families, Gyrinidae (1 sp.), Hydraenidae (5 spp.) and Helophoridae (5 spp.), were represented by a relatively few species in Mongolia ( Fig. 8 ). By comparing the number of total species recorded in Mongolia for each family, Hydraenidae has the highest endemism rate ( Table 1).

At the level of genera, the most diverse genera are Agabus (5 spp.) belonging to Dytiscidae , Helophorus (5 spp.) belonging to Helophoridae , and Ochthebius (5 spp.) belonging to Hydraenidae . Several genera were represented by few species, namely, Hydroporus (1 spp.), Oreodytes (2 spp.), and Zaitsevhydrus (1 spp.) from Dytiscidae and Gyrinus (1 sp.) ( Fig. 8 ).

Endemic and sub-endemic water beetles were recorded in different numbers (from 1 to 12) in the nine sub-basins included in this study. Each of these sub-basins had a peculiar composition of endemic beetles, but there were several species dominating in most of the sub-basins ( Fig. 9 ). The highest number of endemic and sub-endemic beetles was found in SRB (13 species) followed by GLDB (11 species), VLRB and TRB (6 species). Four species were recorded for ShRB, ORB, and GRB, and 3 species for KhRB, while the lowest richness of endemic beetles (1 species) was found in KhGRB ( Table 3).

For endemic species, Helophorus parajacutus was common to five sub-basins, while Oreodytes mongolicus inhabited four sub-basins, Ochthebius mongolensis and Helophorus kaszabianus were found from three, Helophorus shatrovsky was recorded for two sub-basins, which provide a variety of habitats, while Agabus kaszabi , Gyrinus sugunurensis and Ochthebius mongolicus were re-

Bray-Curtis Cluster Analysis(Single Link) VLRB

GRB ORB KhRB ShRB TRB

GLDB SRB

0 50 100 % Similarity corded from one sub-basin. From our analysis, the similarity of endemic species fauna was the highest between ORB and KhRB (80%) and between SRB and DGLB (76.9%), which are located close to each other. The endemic species fauna among other sub-basins was less similar to one another ( Fig. 10 ).

Among the sub-endemic species, Agabus coxalis was the most common, occurring in six sub-basins, while Ochthebius kuwerti was common to five sub-basins, two other species ( Agabus arcticus alpinus and Helophorus mongoliensis ) were distributed in four, and Zaitsevhydrus formaster was found in three sub-basins. Several sub-endemic water beetles, such as Agabus svenhedini , Ochthebius perdurus , Ochthebius subaeneus , and Oreodytes shorti , were recorded from two sub-basins. From our data, it was apparent that three species ( Agabus angusi , Hydroporus kabakovi , and Helophorus khnzoriani ) had restricted ranges within Mongolia because of their distribution were confined to a single sub-basin ( Table 3).

We considered regions bordering Mongolia in our characterization of sub-endemic distribution, including Xinjiang, Gansu and Nei Mongol of China, East Siberia and West Siberia of Russia, as well as Kazakhstan. The sub-endemic species were recorded from 1 - 5 of the above regions. Zaitsevhydrus formaster was distributed in five regions including Mongolia, Agabus coxalis was record- ed from four regions, A. arcticus alpinus and Ochthebius kuwerti were found from three regions, while the most of sub-endemic species ( Agabus angusi , A. svenhedini , Oreodytes shorti , Hydroporus kabakovi , Ochthebius perdurus , O. subaeneus , Helophorus khnzoriani and H. mongoliensis ) were recorded only two regions including Mongolia ( Table 2).

For our analysis concerned with sub-endemic water beetles, we identified a total of 13 species representing in six genera. Based on information of the distribution of sub-endemic species in Mongolia and adjacent regions, a presence or absence matrix for species in the six regions was constructed. We found that the faunistic similarity

Nei Mongol

Xinjiang

Gansu

Kazakhstan

West Siberia

East Siberia

Mongolia

0

50 100

% Similarity coefficient between Mongolia and adjacent regions rang- ed between 15.4 - 73.7% ( Fig. 11 ).

The sub-endemic species fauna of Mongolia was the most similar with that of East Siberia, Russia (73.7%) and followed by West Siberia (58.8%). These results show that Mongolian endemic water beetle fauna was more similar with the neighboring regions in the north rather than in the south.

Figures

Fig. 7. Helophorus shatrovsky Angus, 1985. Photos by Robert Angus. a. Dorsal habitus, male, b. Head and pronotum, c. Aedeagus.

Fig. 8. Classification of endemic and sub-endemic water beetles in Mongolia. n is the total abundance in our samples; E endemic species; S sub-endemic species.

Fig. 9. Endemic and sub-endemic species richness in the nine subbasins of Mongolia included in this study. SRB-Selenge River Basin; ShRB-Shishkhed River Basin; GRB-Gobi River Basin.

Fig. 10. Similarities of endemic beetle fauna among the sub-basins of Mongolia.

Fig. 11. A dendrogram of water beetle faunal similarity of Mongolia and adjacent territories.