1998. P. A. Selden (ed.). Proceedings of the 17th European Colloquium of Arachnology, Edinburgh 1997.

Dominance structure and seasonal changes in the abundance of dominant epigeic in pastures of northern Greater Poland

1 2 Pawe´l Szymkowiak and Marek Woz´ny 1A. Mickiewicz University, Department of and Ecology, Szamarzewskiego 91 A, 60–569 Poznan´, Poland 2 University of Wroc´law, Department of Zoology, Sienkiewicza 21, 50–335 Wroc´law, Poland

Summary Studies were undertaken to establish the relative abundance and quantitative dynamics of epigeic spiders in three types of pasture in northern Greater Poland in 1992 and 1993. The localities differed in the composition of plants, type of substrate, and character of the surrounding biotopes. There were eight dominant in all localities: palustris (Linnaeus, 1758), Xerolycosa miniata (C. L. Koch, 1834), Xysticus kochi Thorell, 1872, Erigone dentipalpis (Wider, 1834), degeeri Sundevall, 1830, Pardosa pullata (Clerck, 1757), Erigone atra Blackwall, 1833, and Oedothorax fuscus (Blackwall, 1834). Analysis of changes in the abundance of dominant species during a vegetation season revealed a number of successive abundance peaks and the replacement of certain species by others. In May P. degeeri, P. pullata and X. kochi reached peaks of abundance. In June they were replaced by P. palustris and X. miniata. In August E. dentipalpis, in September E. atra and P. degeeri, and in October O. fuscus and melanopygius (O. P.- Cambridge, 1879) were most abundant. The structure of dominance and fluctuation in the abun- dance of particular species dominant in a given pasture are affected by the climatic conditions, biocenotic structure and the types of neighbouring ecosystems.

Introduction and intra-population mechanisms related to competition and predator-prey interactions The literature provides a large body of data on (Breymeyer, 1970; Kajak, 1960, 1962, 1971, epigeic faunas. The most frequently used 1978; Kajak et al., 1971; Nentwig, 1982). method of collection is pitfall trapping. There The studies reported in this work were under- are a number of papers devoted to faunistic taken to establish the dominance structure and analyses in particular geographically or seasonal changes in the abundance of dominant naturally specific areas such as the Vienna epigeic spiders in pastures of northern Greater district (Thaler & Steiner, 1993), northern Poland. Switzerland (Maurer, 1975), mountainous areas (Thaler et al., 1987) and lowlands (Weiss & Andrei, 1989). Another group of faunistic–eco- Material and methods logical papers concerns ground spiders living in selected environments like arable fields The material was collected by modified pitfall (Basedow & Rzehak, 1988), xerothermic sites traps with bait of the “Didonis & Miller” type (Thaler, 1985; Bauchhenss, 1990, 1992), wood- (Didonis & Miller, 1980). In each study area 18 lands (Koponen, 1980, 1986), hedges (Blick, traps were arranged in 3 rows of 6 traps. The 1989) or specific plant communities (Polenec, distance between the rows was 100–120 cm, and 1978). Ecological aspects considered have been between traps in each row 150–180 cm. The problems of syn- and autecology of epigeic studies were carried out in 1992–1993, from the spiders communities (Flatz, 1986; Martin, 1991) beginning of May to the end of October. 246 Proceedings of the 17th European Colloquium of Arachnology, Edinburgh 1997

three study sites lie in the vicinity of the town of Szamotu´ly, located about 38 km northwest of Poznan´. Its natural north and east border is the valley of the River Warta. The area is slightly undulating with a mean height of 75–100 m above sea level. The area was once covered with oak–hornbeam forests (Kondracki, 1988), but with the development of cultivation the land was transformed into fields, meadows and pastures. Site 1— Osowo Stare: About 5 km north-east of Szamotul´y, in Osowo Stare village (Fig. 1). Meadows and pastures occupy a low percentage of the area and have been established on both sandy and swampy ground. Meadows are included in the Arrhenatherion alliance from the Molinio-Arrhenatheretea class (Matuszkiewicz, 1984). The area of study is a pasture amongst fields vegetated with high clumps of spreading grasses including a significant contribution of Rye grass (Arrhenatherum elatius) and Orchard grass (Dactylis glomerata). Where the elevation is lower, the contribution of bryophytes and Fig. 1: Map of the study sites. Scale line = 5 km. rushes increases. The transect was made on a drained mound. There was no afforestation in the vicinity of the pasture. Transects were placed in the same positions Site 2—Sycyn Dolny: In Sycyn Dolny village, each year and involved three sites of different about 8 km north of Szamotul´y (Fig. 1). The biotopic conditions located close to one another. pasture studied is a large forest clearing near the Samples were collected every seven or eight overgrown eutrophic Sycyn Lake, merging into days. Material was sorted and then preserved in swamps. The clearing is surrounded by a thick 75% ethyl alcohol. pine stand growing on dry ground. From the Zoocoenological analysis of spider communi- phytosociological point of view there are differ- ties was carried out using the individual domi- ent transient variants from associations of the nance index (D), defined as the percentage Crynephorera class (Matuszkiewicz, 1984) to contribution of specimens of a given species in freshwater marshy sedges of the Scheuchzerio- the total number of specimens collected at a Caricetea fuscae class (Szoszkiewicz, 1971). given site. The following classes of individual The transect was made on a sandy area in the dominance were assumed after Górny & Grüm clearing. This site is dominated by clumpy grass (1981): D5—eudominants > 10%, D4—domi- with a large contribution of sedge in lower-lying nants 5.1–10%, D3—subdominants 2.1–5%, land and perennial communities on sandy eleva- D2—recedents 1.1–2%, D1—subrecedents < 1%. tions. Site 3—Braczewo˛ : On the banks of the River Study sites Warta in Braczewo˛ village, about 12 km north of Szamotul´y (Fig. 1). The pasture is situated on The studies were conducted in northern a dry, strongly sunlit, 5 m high flood-terrace of Greater Poland which geographically belongs to highly mosaic growth with different transient Greater Poland–Kujawy Lowland. The spiders variants of plant associations from the Molinio- occurring in this region have been well studied. Arrhenatheretea class (Matuszkiewicz, 1984). Recently, A. Dziabaszewski (1989, 1991, 1995), The vegetation is dominated by low spreading W. Dziabaszewski (1992) and Szymkowiak and tussock grass, Cinquefoil (Potentilla sp.) (1993) have discovered a few rare species to add and Yarrow (Achillea millefolium) with isolated to the list of spiders known from this area. The aspen trees. Throughout the period of the study Szymkowiak and Woz´ny: Epigeic spiders in pastures 247

Fig. 2: Fluctuations in abundance of Pardosa Fig. 3: Fluctuations in abundance of Pardosa pullata palustris (Linnaeus, 1758) at the site in Osowo Stare. (Clerck, 1757) at the site in Osowo Stare. we did not observe any flooding. The transect but in a few months its index was the second lies in a strongly sun-lit flat part of the area. highest. These species dominated in spring and summer. In September and October the sequence of species with the highest index of Results dominance changed and the following species The material collected totalled 18,995 speci- appeared in the group of eudominants: mens comprising 138 species belonging to 17 Tegenaria agrestis (Walckenaer, 1802), families. Analysis of the contribution of partic- Centromerita concinna (Thorell, 1875), ular species enabled the determination of the C. bicolor (Blackwall, 1833), Tiso vagans dominance structure of spider communities at (Blackwall, 1834), Pisaura mirabilis (Clerck, the three sites. 1757), Pachygnatha degeeri and Oedothorax fuscus (Blackwall, 1834). Dominance structure and seasonal changes in Site 2—Sycyn Dolny. The 2302 specimens col- species dominance lected belonged to 83 species. Calculation of individual dominance index showed: D5— A group of species dominating in a given Xerolycosa miniata (C. L. Koch, 1834) (27.6%), month is defined as those whose dominance Pardosa palustris (25.0%), Xysticus kochi index is 5.1–100% (eudominants or dominants). Thorell, 1872 (15.9%); D4—absent; D3—3 The species dominant from May to October in species; D2—4 species; D1—73 species. The 1992 and 1993 are given in Table 1. Because of the small number of specimens collected at Braczewo˛ in October 1992, no dominance struc- ture was calculated. Site 1— Osowo Stare. The 10,451 specimens collected represented 92 species. Calculation of the individual dominance index revealed: D5— Pardosa palustris (Linnaeus, 1758) (52.8 %); D4—P. pullata (Clerck, 1757) (8.4%), Pachygnatha degeeri Sundevall, 1830 (5.6%); D3—7 species; D2—3 species; D1—79 species. The index of individual dominance of P. palustris reached 40–70% in seven of the twelve months of study. The second most abun- dant species was P. pullata which was eudomi- nant in four of the months of study. Its Fig. 4: Fluctuations in abundance of Pachygnatha contribution was less than that of P. palustris, degeeri Sundevall, 1830 at the site in Osowo Stare.

248 Proceedings of the 17th European Colloquium of Arachnology, Edinburgh 1997

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Fig. 5: Fluctuations in abundance of Xerolycosa Fig. 6: Fluctuations in abundance of Pardosa miniata (C. L. Koch, 1834) at the site in Sycyn Dolny. palustris (Linnaeus, 1758) at the site in Sycyn Dolny. contribution of two species, P. palustris and of eudominants and dominants. For these X. miniata, was the greatest from June to species seasonal changes in absolute abundance August. Apart from these two species, this site were determined in each year and at each site. was characterized by large numbers of X. kochi, Site 1— Osowo Stare. Changes in abundance eudominant in May, and Alopecosa schmidti of Pardosa palustris (eudominant) are similar in (Hahn, 1835) and Meioneta rurestris (C. L. the two years, the only difference being slightly Koch, 1836), eudominants in August. In fewer specimens in 1992 (Fig. 2). The abun- September and October the group of eudom- dance of P. pullata, a dominant, was greatest in inants was extended to include: Pardosa May in both years, and decreased until pullata, Tegenaria agrestis, Pisaura mirabilis, September (Fig. 3). In 1992 its abundance Ostearius melanopygius (O. P.-Cambridge, decreased gradually, while in 1993 small fluctu- 1879), and Pelecopsis parallela (Wider, 1834). ations were observed. Fluctuations in the abun- Site 3—Braczewo ˛ . The 2166 specimens col- dance of Pachygnatha degeeri were similar in lected belonged to 69 species. Calculation of the both years (Fig. 4), and resembled those of individual dominance index showed: D5— Pardosa palustris, with decrease in abundance Erigone dentipalpis (Wider, 1834) (36.7%), of the former more rapid in June. It is interesting Pardosa palustris (23.3%); D4—Pachygnatha to note that in 1992 its numbers were four times degeeri (9.5%), Erigone atra Blackwall, 1833 greater than in 1993 at this site. In general, the (7.9%), Oedothorax fuscus (5.3%); D3—2 fluctuations of abundance of these three species species; D2—2 species; D1—60 species. At this between the two years are similar. site, in May and June the species with the high- est dominance was Pardosa palustris. Other eudominants in these months were: Erigone dentipalpis, E. atra, Pachygnatha degeeri, Xerolycosa miniata, and Xysticus kochi. In September the contribution of E. dentipalpis decreased and, as a result, Meioneta rurestris (C. L. Koch, 1836), Pachygnatha degeeri and Oedothorax fuscus became more important, with the latter reaching 49% in October 1993.

Phenology

The material collected in the two years Fig. 7: Fluctuations in abundance of Xysticus kochi included eight species belonging to the classes Thorell, 1872 at the site in Sycyn Dolny. 250 Proceedings of the 17th European Colloquium of Arachnology, Edinburgh 1997

Fig. 8: Fluctuations in abundance of Erigone Fig. 9: Fluctuations in abundance of Pachygnatha dentipalpis (Wider, 1834) at the site in Braczewo.˛ degeeri Sundevall, 1830 at the site in Braczewo.˛

Fig. 10: Fluctuations in abundance of Erigone atra Fig. 11: Fluctuations in abundance of Oedothorax Blackwall, 1833 at the site in Br˛aczewo. fuscus (Blackwall, 1834) at the site in Braczewo.˛

Site 2—Sycyn Dolny. Changes in the abun- ilar to those at site 1. Pachygnatha degeeri was dance of Xerolycosa miniata, a eudominant, are a dominant at this site, but the changes in its similar in the two years (Fig. 5). In both, the abundance in the two years were different maximum number of specimens appeared in (Fig. 9). In 1992 it was abundantly represented June, and thereafter decreased until September. in May, but in 1993 reached a high abundance in For Pardosa palustris, another eudominant, the August. The abundance of another dominant at changes in abundance in the two years were dif- this site, Erigone atra, showed rather smooth ferent (Fig. 6). In 1992 high numbers appeared fluctuations in 1992, while in 1993 the changes in May and September. In 1993 the maximum were more pronounced with a distinct peak in numbers appeared in June and thereafter August (Fig. 10). The presence of the third dom- remained at a low level. The third eudominant, inant at this site, Oedothorax fuscus, was dis- Xysticus kochi, was most abundant at the begin- continuous. From May until July only a few ning of May, and then decreased rapidly. In 1992 specimens of this species appeared while in over 4.5 times more specimens were collected September and October they were most (Fig. 7). Site 3—Braczewo. ˛ The changes in abundance abundant (Fig. 11). of Erigone dentipalpis, a eudominant, were considerably different in the two years (Fig. 8). Discussion and conclusions In 1993 the numbers were over twice those in 1992. For Pardosa palustris, another eudomi- Analysis of the structure of dominance of nant, the changes in the two years are rather sim- spiders found at all sites studied in the period Szymkowiak and Woz´ny: Epigeic spiders in pastures 251 from May to October each year, identified eight One species, Pachygnatha degeeri, was com- key species: Pardosa palustris, P. pullata, mon to all three sites; although it did not take the Xerolycosa miniata, Xysticus kochi, highest position in terms of abundance in any of Erigone dentipalpis, E. atra, Pachygnatha the months of study, in many months its relative degeeri, and Oedothorax fuscus. abundance was high enough for it to be classi- The seasonal distribution of the index of dom- fied as eudominant. Therefore, P. degeeri inance revealed that there are many species (29) should be regarded as a constant element of the whose dominance in particular months reached spider arachnofauna. high values (Table 1). At site 1, Pardosa palustris Analysis of changes in the abundance of dom- reached the highest values for most of the trap- inant species during a vegetation season reveals ping season. This species prefers moderately a number of successive abundance peaks and humid places in meadows and fields under culti- replacement of certain species by others. In May vation (Prószyn´ski & Star˛ega, 1971). Lower P. degeeri, P. pullata and X. kochi reached peaks values of the index of dominance were found for of abundance. In June the numbers of these P. prativaga (L. Koch, 1870) and P. pullata. species rapidly decreased and they were These species choose more humid spots replaced by P. palustris and X. miniata. In sum- (Prószyn´ski & Star˛ega, 1971), so their individ- mer the epigeic spiders became much less abun- ual contribution was not as high as that of dant and in July no species was observed to P. palustris. The preferences of these species reach a peak of abundance in the three localities are also evident when analysing their dominance studied. The species of Lycosidae gave way to indices in particular months of 1992 and 1993. those from the families Erigonidae and The dominance index of P. palustris was higher in 1992 while the indices of P. prativaga and Tetragnathidae. In August we noted peaks of P. pullata were higher in 1993. This corre- abundance for E. dentipalpis, E. atra, and sponds to the changes in humidity level, as the P. degeeri, while in September and October mean daily precipitation in 1992 was 1.70 mm Oedothorax fuscus and Ostearius melanopygius while in 1993 it was 4.22 mm. This increase in were most abundant. humidity was most probably the reason why The structure of dominance and fluctuation in dominance of P. prativaga in August and the abundance of particular species dominant in September 1993 was so high. Site 2 was charac- a given pasture are affected by the climatic con- terized by the highest individual contribution of ditions, biocenotic structure and the types of Xysticus kochi in May and P. palustris and neighbouring ecosystems. Xerolycosa miniata alternately in the other months. X. kochi prefers the litter of dry pine Acknowledgements forests (Prószyn´ski & Star˛ega, 1971) and its appearance in the pastures was related to the The authors wish to thank Dr M. Bunalski for close neighbourhood of such forest. X. miniata the loan of the material he collected when study- prefers dry sandy conditions (Prószyn´ski & ing coprophagic beetles (Scarabaeoidea). Star˛ega, 1971) and at this site it found its favourite habitat. At site 3, one of the most abun- dant species was P. palustris; however, apart References from this species there were two other eudom- inants: Erigone dentipalpis and E. atra which BASEDOW, T. & RZEHAK, K. 1988: Abundanz und did not appear as dominants at the other sites. Aktivitätsdichte epigäischer Raubarthropoden auf Ackerflächen—ein Vergleich. Zool. Jb. (Syst.) 115: Representatives of these species supplanted 495–508. lycosid species which are usual dominants dur- BAUCHHENSS, E. 1990: Mitteleuropäische ing the spring and summer. The character of this Xerotherm-Standorte und ihre epigäische biotope—a riverside pasture—favours the Spinnenfauna—eine autökologische Betrachtung. appearance of aeronaut species such as Abh. Verh. naturw. Ver. Hamburg 31/32: 153–162. E. dentipalpis and E. atra. Most probably these BAUCHHENSS, E. 1992: Epigäische Spinnen an species had reached the site through migration unterfränkischen Muschelkalkstandorten. Abh. along the river banks. naturw. Ver. Würzburg 33: 51–73. 252 Proceedings of the 17th European Colloquium of Arachnology, Edinburgh 1997

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