Ardelean, Gavril (szerk.): Satu Mare. Studii şi comunicări. Seria ştiinţele naturale 6. (2005)
The epigeic spider communities (araneae) of three winter wheat fields in Gherla region (Cluj district)
Satu Mare - Studii şi Comunicări Ştiinţele Naturale — Voi. VI (2005) ■ -5 traps to 5 m from the margin ■ -5 traps to 35 m from the margin The traps were used from May to August in 2001, emptied with 7 day frequency (9 sampling data). Spiders were identified to species level (juveniles only to genus or family) according to Heimer & Nentwig (1990), Locket & Millidge (1951), Roberts (1993) and Tongiorgi, (1966). Species nomenclature is according to Platnick (2005). Since pitfall traps catch mainly adult spider individuals and juveniles could not be reliably identified, for dominancy and diversity analyses only the data of adult specimens were used. For faunistical investigation we used the whole amount of collected spiders. We used Rényi-function (Tóthmérész 1993) to characterize species diversity in different trap rows. Rényi- diversity: H„= (lnI(N,/NT )“)/(!-<*) where 0<a, a^l, Ni means the number of individuals of the species i, T means the total number of species, Nt means the total number of individuals, and a is scale parameter. When the scale parameter is low, the function is more sensitive to rare species, whereas high values of the scale parameter suggests that the function is more sensitive to dominant species. If a = 0, then H„ ->H s (H s: Shannon diversity). If a = 0, then H« = ln T. Results and discussion Faunistical results A total of 4540 spiders were collected belonging to 57 species of 12 families (Tab. 1). We identified four species which was not recorded since now from arable lands in Eastern Europe: family Linyphiidae: Erigonoplus globipes (Koch 1872) 2 female and 3 male specimens, Nematogmus sanguino lentus (Walckenaer 1841) 1 female and 2 male specimens and Pocadicnemis juncea Locket & Millidge 1953: 2 male specimens; family Lycosidae: Pardosa vittata, (Keyserling 1863): 55 male specimens. Pardosa vittata was recorded second time in Romania; it was first recorded in 1971 from south Romania, Hagieni forest, Constanta district (Fuhn & Oltean 1969, Fuhn & Niculescu -Burlacu 1985). This hygrophilous species was collected in large numbers from the margin rows of the winter wheat. This Pardosa species have not occured in arable fields of the neighbour countries as Hungary and Slovakia (Gajdos 1992, Samu & Szinetár 1999). Community structure and dominancy To have a view on the distorted dominancy structure of species we made five groups of spider species using the number of adult spiders: 39 species with individuals between 1 and 10; 9 species with individuals between 10 and 50 individuals; 5 species with individuals between 50 and 100; 4 species with individuals between 100 and 450; 1 species individuals between 450 and 2600. The 86.96% of 4540 collected spiders was adult specimens and 13% was subadult or juvenile (Fig. 1). The family Lycosidae proved to be eudominant (84.9% of adult spiders) followed by Thomisidae (5.2%) and Linyphiidae (3.44%). Lycosid spiders were represented by 3350 adult specimens belonging to 17 species. The most abundant species of this family were: Pardosa agrestis, Pardosa prativaga and Trochosa ruricola. Family Thomisidae was represented by 208 adult specimens belonging to 4 species. Xysticus kochi was the most abundant species of this family. Family Linyphiidae was represented by 136 adult specimens belonging to 12 species. The most abundant species of this family was Oedothorax apicatus. Table 1. List of collected species of spiders and number of female and male specimens. Families Species Female Male Iheridiidae Episinus truncatus Latreille, 1809 0 2 Robertus arundineti (O. P.-Cambridge, 1871) 0 6 Robertus neglectus (O. P.-Cambridge, 1871) 0 9 Steatoda phalerata (Panzer, 1801) 6 15 Linyphidae Araeoncus humilis (Blackwall, 1841) 0 3 Ceratinella brevipes (Westring, 1851) 0 1 Diplosţyla concolor (Wider, 1834) 3 5 Erigonoplus globipes (L. Koch, 1872) 2 3 Meioneta rurestris (C. L. Koch, 1836) 0 13 Meioneta simplidtarsis (Simon, 1884) 0 1 Microlinyphia impigra (O. P.-Cambridge, 1871) 0 1 Nematogmus sanguinokntus (Walckenaer, 1841) 1 2 Oedothorax apicatus (Blackwall, 1850) 74 18 41
