North-Western Journal of Zoology Vol. 4, No. 1, 2008, pp.61-71 [Online: Vol.4, 2008: 11] The effect of a naturally fragmented landscape on the spider assemblages Robert GALLÉ Department of Ecology, University of Szeged, Szeged, Közép fasor 52, H-6725 E-mail: [email protected]; Tel: +36/62-546-952 Abstract. As the Kiskunság sanddune region in the Great Hungarian Plain is a network of poplar forest fragments surrounded by open grasslands, it offers an opportunity to study the ecological effects of natural, long-term fragmentation on the invertebrate assemblages. The spider assemblages of 15 forest patches and the grassland matrix in between them were sampled using pitfall traps. A Principle Coordinate Analysis revealed three distinct groups of forest assemblages: (1) small patches with high species diversity, similar to the surrounding grassland, (2) medium sized patches and (3) large forests. The only significant relationship was observed between the frequency of forest specialist species and the fragment size. Key words: Araneae, poplar (Populus) forest, Kiskunság, sand dune area. Introduction Spiders are one of the most abun- dant polyphagous predators in all According to the classical theory of kinds of forests (Miyashita 1998). The island-biogeography the assemblages litter type, soil moisture (Pearce & of the larger habitat patches have Veiner 2006), composition and struc- higher number of species, and the ture of vegetation has a significant degree of isolation is inversely related influence on the species composition to the number of species (MacArthur & and diversity of spider assemblages Wilson, 1967). This theory was later (Ysnel & Canard. 2000, Heikkinen & used on terrestrial patchy landscapes, MacMahon 2004). where the islands are the hospitable The spiders are suitable organisms patches and the surrounding matrix is for the study of fragmented landscapes usually less hostile than the sea in the as the species composition is different classical theory (Hartel et al 2008). in small and large forest patches (Gibb Several studies showed that the patch & Hochuli 2002). The habitat frag- shape, quality and also the surround- mentation has various effects on the ing matrix have a significant influence spider guilds (Vandergast & Gillespie on the species composition and 2004): species number of large orb richness of the invertebrate assemblage weavers (Araneidae) relative to all spi- (e.g. Laurence & Yensen 1991, Lővei et der species decreases with the higher al. 2006, Magura & Köbölöcz 2007, degree of fragmentation (Miyashita Öberg 2007). 1998), whereas tangle-web weavers North-West J Zool, 4, 2008 Oradea, Romania 62 Gallé, R. (Theridiidae) and wandering hunters meters between the traps. The traps were (e.g. Lycosidae) are less sensitive to installed four times in 2006, in May, June, forest size and isolation (Major et al August and September to cover the activity of the most spider species. Each sampling period 2006, Miyashita 1998). lasted for two weeks. The spider data were The original vegetation of the standardized to number of individuals per Kiskunság region of the Hungarian traps and number of species per trap to Great Plain was forested-steppe which account for unequal sampling among forest consisted of small poplar and oak patches. The Principle Coordinate Analysis (PCoA) forests surrounded by open sandy on the basis of Bray-Curtis similarity measure grasslands. Only small patches of the was used to group spider assemblages of the natural vegetation are left in the matrix patches. of agricultural fields and forest planta- We measured the canopy area of the forest tions. The present study was carried patches using ArcView GIS software and out near Fülöpháza village in a natural aerial photographs as background data (Fig. 1). The area/perimeter ratio was described by sand dune area. The spider assem- the shape index (Magura et al 2001, Magura & blages of the forest patches of different Köbölöcz, 2007). The value of the index is 1 for sizes were evaluated in order to the round patches and it increases if the shape examine the relationship between the deviates from the round shape. The inverse assemblage properties and the habitat isolation was used to characterize the degree characteristics and to compare the of isolation of the studied patch. The index was estimated as the number and cumulative species diversity of the grasslands (the area of the neighbouring forests not further matrix for the forest specialist species) than 100 meters from the patch. The 100 and that of the forests. The aim of the meters distance was chosen because present study was to characterize the wandering spiders can cover more than 10 m spider assemblages of the poplar forest per day, and although ambush spiders and web builder move less, they can however shift patches and to show how the distri- great distances by ballooning in the air (Marc bution of the spider species indicates et al. 1999), and thus spiders can cover this the heteromorphic landscape. distance in a few days. The collected species were categorized according to their habitat requirements. Three Materials and methods groups were identified: (1) forest specialists, (2) grassland specialists and (3) generalist The spider assemblage of 14 poplar species (Heimer & Nentwig 1994, Buchar & (Populus alba) forest patches (~90-1500 m2), one Ruzicka 2002). larger forest (~5000 m2) and the open The multiple linear regression analysis grassland (with the most abundant plant was used to analyze the relationship between species being Festuca vaginata, Stipa the forest patch characteristics (size, shape, borysthenica and Euphorbia seguieriana) in isolation) and that of the spider assemblages between them were sampled using pitfall (total number of species per trap, number of traps containing ethylene glycol as preserva- forest-specific species per trap, and the tive. There were five to 15 traps in a forest number of specimens belonging to the forest patch, depending on its size, placed by an specialist species per trap). No significant inhibition random pattern in the typical part colinearity was found between the variables of the forest patch, keeping at least four (variance inflation factors ranged between 1 and 1.1). North-West J Zool, 4, 2008 The effect of a naturally fragmented landscape on the spider assemblages 63 Rényi’s diversity was calculated in order According to the PCoA, three to compare the distinct groups of assemblages distinct groups of forest assemblages (Tóthmérész, 1995). were identified: (1) small patches and For the statistical analyses we used the PAST (Hammer et al 2001) and R (R the control grassland; (2) medium sized Development Core Team 2007) software patches and (3) larger forests (Fig. 2). packages. On the PcoA scatterplot the points got arranged along a curve (horseshoe or arch effect), the cause of the pheno- mena presumably being the changes in species composition and richness along an underlying gradient. No significant relationship was found between the patch character- ristics, the number of species and the number of forest specialist species. There is however a significant relation- ship between the number of specimens belonging to the forest specialist species and the area of the forests (Table 2). The diversity profiles of the grassland and small patches lie above those of the larger forests and in case of larger scale parameters, they do not intersect. Thus assemblages of the open habitats are more diverse for a wide range of the scale parameter, for indexes sensitive for both the abundant Figure 1. The areal photograph of the forest- and rare species (Fig. 3). steppe area near Fülöpháza village. The studied forest are marked. Discussion Results When the species–area relationship is applied to terrestrial patchy Out of the total number of 1092 landscapes the results do not usually collected spider specimens, 211 spiders confirm the classical theory of island were juveniles; these could not be biogeography (Cook et al 2002, Lővei et identified to species level. Altogether al 2006). This phenomena is brought 59 species belonging to 11 families about by the inclusion of matrix species were recorded (Table 1). North-West J Zool, 4, 2008 Table 1. Forest patch characteristics and the list of species. The specimens per trap values are given. Abbriveration: gr: grassland. ID gr 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Area (m2) - 88 104 109 138 167 265 410 428 476 591 726 1005 1414 1443 4966 Shape index - 1.09 1.30 1.17 1.20 1.15 1.03 1.64 1.90 1.50 1.21 1.49 1.26 1.23 1.16 1.24 Inverse isolation (m2) - 5629 5270 8544 5635 5593 3811 4908 5123 5404 13852 3414 7128 6651 8987 7246 Taxa: Dysderidae Harpactea rubicunda (C.L. Koch, 1838) 0 0 0 0 0 0 0 0 0.20 0 0.25 0.20 0.10 0 0.07 0.07 Theridiidae Enoplognatha thoracica (Hahn, 1833) 0 0 0 0 0 0 0 0 0.10 0 0 0 0 0 0 0 Steatoda albomaculata (De Geer, 1778) 0.07 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Steatoda phalerata (Panzer, 1801) 0 0 0 0 0 0 0 0 0 0 0 0 0 0.07 0 0 Linyphiidae Acartauchenius scurrilis (O.P.-Cambridge, 1872) 0.27 0 0.20 0 0 0 0 0 0 0 0 0.10 0.10 0 0 0 Centromerus sylvaticus (Blackwall, 1841) 0 0 0 0 0 0 0 0 0.10 0.13 0 0.10 0.10 0 0.20 0.20 Ceratinella brevis (Wider, 1834) 0 0 0 0 0 0 0 0 0 0 0 0 0 0.07 0.20 0 Meioneta rurestris (C.L. Koch, 1836) 0.13 0 0 0 0 0 0 0 0 0.13 0.13 0 0 0 0 0 Neriene clathrata (Sundevall, 1830) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0.07 Panamomops fagei Miller & Kratochvil, 1939 0 0 0 0 0 0 0 0 0 0 0 0 0 0.07 0.13 0 Pelecopsis parallela (Wider, 1834) 0 0 0 0 0 0.20 0 0 0 0 0 0 0 0 0 0 Sintula spiniger (Balogh, 1935) 0 0 0 0 0 0 0 0 0 0 0.13 0 0 0 0.07 0 Styloctetor romanus (O.P.-Cambridge, 1872) 0.07 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Table 1.