Biologia, Bratislava, 62/3: 345—350, 2007 Section Zoology DOI: 10.2478/s11756-007-0057-9 Spatial pattern of water bugs (Nepomorpha, Gerromorpha) at different scales in the Szigetk¨oz (Hungary) János N. Nosek1, Tamás Vásárhelyi 2, Gábor Bakonyi3 & Nándor Oertel1 1Hungarian Danube Research Station of HAS, Jávorka S. u. 14,H-2131 G¨od, Hungary; e-mail: [email protected] 2Hungarian Natural History Museum, Baross u. 13,H-1088 Budapest, Hungary 3SzIU Department of Zoology and Ecology, Páter K. u. 1,H-2100 G¨od¨oll˝o, Hungary Abstract: In 2003, 26 Heteroptera species (16 aquatic and 10 semiaquatic) were collected from 53 sampling sites in the Szigetk¨oz region in Hungary. Ilyocoris cimicoides and Gerris argentatus were the most frequent aquatic and semiaquatic species, respectively. Large differences both in the species number and species composition were observed among the different flood-prevention areas, arm systems and habitats. Strong negative correlation was found between the average number of aquatic species and current velocity, and a strong positive correlation between the average number of aquatic and semiaquatic species and macrophyte density. From a faunistic point of view, the marsh at Arak is the most interesting and valuable site. Key words: Heteroptera; Nepomorpha; Gerromorpha; biodiversity; Danube River; Szigetk¨oz Introduction Sampling sites can be identified by the name of the water body or the nearest site, with the aid of the river kilometre There are very few data on the aquatic and semi- mark (rkm) and the code of the site. Sites were selected in aquatic bug (Heteroptera: Nepomorpha and Gerromor- order to ensure habitat diversity was as high as possible. pha) fauna of the Szigetk¨oz arm system of the Danube The sites are as follows: ¨ River. Only sporadic faunistical data are available con- 1. Danube main arm, (Oreg-Duna, Old Danube, DUF), abandoned main arm, 13 sampling sites): Dunaki- cerning the occurrence of some species (Bakonyi 1990; ◦ ◦ liti 1845 rkm (DKI4 /47 59 41.0 N, 17 18 51.0 E/, DKI5 Ambrus et al. 1995; Nosek 1996). Systematic sampling /47◦5940.3 N, 17◦1849.1 E/, DKI6 /47◦5940.0 N, programmes have been carried out only twice, at the 17◦1846.7 E/), Dunakiliti 1843 rkm (DKI0 /47◦5941.0 beginning (unpublished data) and the end (Cs¨orgits & N, 17◦1855.1 E/, DKI1 /47◦5941.1 N, 17◦1900.5 E/, th Hufnagel 2000) of the last decade of the 20 century. DKI2 /47◦5942.4 N, 17◦1903.8 E/, DKI7 /47◦5940.6 Within a research program looking at the macroscopic N, 17◦1910.9 E/), 1839 rkm (DUF0 /47◦5825.9 N, benthic macroinvertebrates of the Danube River (Nosek 17◦2129.6 E/), 1832 rkm (DUF3 /47◦5556.5 N, 17◦24 32.9 E/), 1827.5 rkm (DUF4 /47◦5343.4 N, 17◦2645.8 & Oertel 2004), a detailed sampling program was per- ◦ ◦ ◦ formed in Szigetk¨oz in 2003. In this study, the spa- E/, DUF6 /47 53 46.6 N, 17 26 37.3 E/, DUF7 /47 43 45.9 N, 17◦2642.3 E/), Dunaremete 1825.5 rkm (DRE2 tial heterogeneity of the aquatic and semiaquatic Het- ◦ ◦ eroptera species was analysed in the area of Szigetk¨oz /47 52 51.3 N, 17 27 40.2 E/). 2. Active alluvial floodplain (HUL, 30 sampling sites): in order to identify biodiversity hotspots (sensu Myers ◦ “Mosoni” Danube, upper lock head (RAJ1 /48 00 46.9 et al. 2000) and less valuable areas. N, 17◦1300.1 E/); main canal of water supply sys- tem at Dunakiliti (VPF1 /47◦5906.0 N, 17◦1926.1 E/); “Tejfalui” side arm system: “G¨orgetegi” weir (GOR1 Material and methods /47◦5840.7 N, 17◦2100.8 E/, GOR2 /47◦5836.8 N, ◦ ◦ ◦ Szigetk¨oz, one of the two wetlands along the Hungarian 17 21 02.9 E/, GOR3 /47 58 38.2 N, 17 21 04.9 E/), ◦ ◦ part of the Danube River, is situated in the northwest part “Szigeti- or Kormos-Danube” (TEJ1 /47 57 41.3 N, 17 21 ◦ ◦ of Hungary between the main arm of the Danube River 45.1 E/, TEJ2 /47 57 43.2 N, 17 20 36.3 E/, TEJ3 ◦ ◦ (bordering Slovakia) and the Mosoni Danube down streams /47 57 23.7 N, 17 21 25.3 E/); “Cikolai” arm system: ◦ ◦ from Rajka to the city of Gy˝or. After the break through at Nagy-Ciglés (NAC1 /47 56 57.7 N, 17 23 30.5 E/), “Kis- ◦ ◦ Dévény the slope of the river bed decreases significantly, vessz˝osi” weir (CIK3 /47 56 25.7 N, 17 22 49.5 E/, CIK4 leading to an enormous bed-load and deposition of sus- /47◦5741.3 N, 17◦2146.5 E/), outlet of the side arm pended material building up the alluvial fan along with its system (CIK2 /47◦5556.3 N, 17◦2428.0 E/); “Schisler” side arm systems. The area of the Szigetk¨oz is 375 km2. oxbow lake (SCH1 /47◦5712.6 N, 17◦2121.5 E/, SCH3 Samples were taken at 81 sites in the Szigetk¨oz area /47◦5707.9 N, 17◦2136.6 E/, SCH4 /47◦5707.8 N, at three occasions, late spring (26–31 May), early summer 17◦2143.0 E/); “Csákányi” Danube (CSK0 /47◦5748.1 (22–27 July) and early autumn (8–12 September) in 2003. N, 17◦2208.0 E/, CSA1 /47◦5717.8 N, 17◦2140.0 E/, c 2007 Institute of Zoology, Slovak Academy of Sciences 346 J.N. Nosek et al. CSA3 /47◦5715.8 N, 17◦2148.1 E/, CSA4 /47◦5716.4 plain, protected area) and Mosoni-Danube; 3. Arm sys- N, 17◦2140.3 E/); “Denk Pál” fish ladder (HAL0 /47◦55 tems (e.g., “Zátonyi” Danube, “Csákányi” Danube, “Ciko- 54.7 N, 17◦2431.5 E/), “Bodaki” side arm system: lai” arm system, “Ásványi” arm system, “Lipóti” oxbow (BOD1 /47◦5400.2 N, 17◦2538.8 E/), outlet of the “Bo- lake, “Araki” marsh, etc.); 4. Habitats (classified by current daki” side arm system (BOD2 /47◦5348.3 N, 17◦2631.1 velocity and macrophyte density categories); 5. Sampling E/); seapage water canal at Dunaremete (DRE3 /47◦52 sites. ◦ 44.9 N, 17 27 49.6 E/); “Ásványi” side arm system: According to current velocity five categories were iden- ◦ ◦ Ásványráró harbour (ASV2 /47 50 17.7 N, 17 31 06.5 tified (R 0 = standing water <0.1 m s−1;R1=slow,0.1– ◦ ◦ E/), “V¨olgy” island (ASV3 /47 50 10.7 N, 17 32 25.1 0.5 m s−1; R 2 = middle, 0.5–1.0 m s−1;R3=strong, ◦ ◦ E/), “Halrekeszt˝o” arm (ASV5 /47 50 13.2 N, 17 30 38.4 1.0–2.0 m s−1; R 4 = very strong, > 2.0 m s−1). According ◦ ◦ E/), “Árvai” arm (ASV6 /47 49 57.3 N, 17 32 33.1 E/), to the macrophyte density (total volume of emergent and ◦ ◦ “Gombócosi” island (GOS1 /47 51 21.3 N, 17 29 39.4 submersed plants in percent of the water column) six cate- E/); “Bagaméri” side arm system: “P¨or¨os” island (BAG1 gories were distinguished (S 0 = no plant; S 1 = very rare ◦ ◦ /47 48 17.3 N, 17 34 40.5 E/), outlet of the side arm sys- (1–5%); S 2 = rare (10–25%); S 3 = middle (25–50%); S 4 ◦ ◦ tem (BAG2 /47 48 40.2 N, 17 36 40.4 E/). = dense (50–80%); S 5 = very dense (>80%)). 3. Protected area (MEN, 25 sampling sites): Seapage The index of dispersion (ID) was calculated after El- ◦ ◦ water canal at Rajka (SZC1 /48 00 44.1 N, 17 12 51.0 liot (1971). Species composition of the sampling sites was ◦ ◦ E/), and at Dunakiliti (SZC2 /47 58 46.7 N, 17 15 56.2 compared by cluster analysis using the SYN-TAX 2000 pro- ◦ ◦ E/, SZC3 /47 58 46.7 N, 17 16 02.7 E/), “Zátonyi” gram package (Podani 2001). Nomenclature was used after ◦ ◦ Danube at Dunakiliti (ZAT1 /47 58 42.1 N, 17 16 41.7 Aukema & Rieger (1999). E/, ZAT2 /47◦5755.6 N, 17◦1815.0 E/, ZAT3 /47◦57 54.1 N, 17◦1815.9 E/, ZAT8 /47◦5754.6 N, 17◦1820.1 E/, ZAD2 /47◦5755.9 N, 17◦1812.6 E/), at Dunasziget Results (ZAD1 /47◦5705.2 N, 17◦2040.1 E/), at Cikolasziget (ZAT9 /47◦5513.6 N, 17◦2155.4 E/), at Bodak (ZAT4 ◦ ◦ ◦ Total area /47 54 15.1 N, 17 23 17.3 E/, ZAT5 /47 54 07.8 N, Aquatic and/or semiaquatic Heteroptera species were 17◦2315.2 E/, ZAT6 /47◦5413.9 N, 17◦2306.0 E/, ◦ ◦ found at 53 of the 81 sampling sites (65%). There was ZAT7 /47 54 18.7 N, 17 23 01.9 E/), “Nováki” canal (NOC1 /47◦5311.7 N, 17◦2337.6 E/, NOC2 /47◦5203.0 one sampling site where only Micronecta larvae were N, 17◦2539.4 E/, NOC3 /47◦5015.8 N, 17◦2539.4 E/), found which could not be identified to species level. “Lipóti” oxbow lake (LIP2 /47◦5151.6 N, 17◦2729.0 E/, As the evaluations (cluster and correlation analyses are LIP3 /47◦5151.4 N, 17◦2718.1 E/, LIP4 /47◦5153.1 based on the occurrence and/or number of species, this N, 17◦2756.8 E/, LIP5 /47◦5149.8 N, 17◦2745.8 E/), sampling site was excluded from the analyses. At the ◦ ◦ “Zsejkei” canal at Lipót (ZSC1 /47 51 02.8 N, 17 27 40.5 remaining 52 sampling sites (code underlined in the site E/), “Araki” marsh (ARA1 /47◦5145.2 N, 17◦2131.3 E/, ◦ ◦ list) 16 aquatic and 10 semiaquatic species were sam- ARA2 and ARA3 /47 51 42.8 N, 17 21 40.3 E/).