Species Richness and Composition Patterns Across Trophic Levels of True Bugs (Heteroptera) in the Agricultural Landscape of the Lower Reach of the Tisza River Basin
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J Insect Conserv DOI 10.1007/s10841-012-9484-1 ORIGINAL PAPER Species richness and composition patterns across trophic levels of true bugs (Heteroptera) in the agricultural landscape of the lower reach of the Tisza River Basin Attila Torma • Pe´ter Csa´sza´r Received: 30 September 2011 / Accepted: 25 March 2012 Ó Springer Science+Business Media B.V. 2012 Abstract River basins are among the most threatened the remaining grasslands of the lower reach of the Tisza ecosystems. The species diversity of several European river River Basin. basins decreased seriously during the last decade due to loss of habitats and increasing land use pressure on the Keywords Predaceous Á Herbivorous Á Insect diversity Á remaining habitats. We studied true bug assemblages in Land use Á Dike Á Riparian grasslands various land use types of grassland fragments and dikes as linear grassland habitats in the agricultural landscape of the lower reach of the Tisza River Basin. We tested the effects Introduction of the recorded variables of habitat quality, surrounding landscape and land use type on the abundance, species In their natural states, riverine landscapes are characterised richness and composition of true bugs. Altogether, 5,389 as a mosaic habitat-complex with considerable longitudinal adult Heteroptera individuals representing 149 species in extension. Due to the high connectivity and the heteroge- 13 families were collected. The factors which influenced neity of riverine landscapes (Naiman et al. 2005), flood- significantly the species richness of different trophic levels plains can support a diverse flora and fauna (Gregory et al. (i.e. herbivors, predators) and degrees of food specializa- 1991; Zwick 1992; Ward et al. 1999). However, river tion (i.e. generalist and specialist herbivors) were concor- controls have caused dramatic changes in rivers and their dant. Contrary to this, the factors which influenced the riparian zones (Dynesius and Nilsson 1994; Nilsson et al. abundance of the different feeding groups varied strongly. 2005). Nowadays, many European rivers are restricted to We emphasise the vegetation and land use types as pri- narrow riverbeds bordered by rigid dikes, riverbeds are marily influential factors for insects. Excluding the grass- often straightened and the majority of riparian habitats are feeding species, the number of both generalist, specialist transformed into intensive agricultural areas (Tockner et al. herbivorous and predaceous species were lower in agri- 2009). In the last decade Central European floodplains have cultural swards, i.e. hay-meadows and pastures than in old experienced a decline in biodiversity, due to a loss of field and dike habitats and their number increased with habitats and increased land use pressure on the remaining increasing vegetation diversity. Due to the high species habitats (Godreau et al. 1999; McCollin et al. 2000). The richness and abundance observed in dike and old field intensification of agricultural land use caused a decrease in habitats compared to agricultural swards, we emphasise species richness in most European countries (Marshall and their importance for conservation of insect diversity and we Moonen 2002) due to the destruction, fragmentation and stress the negative effects of agricultural intensification on isolation of the natural habitats (Tscharntke and Kruess 1999; Steffan-Dewenter and Tscharntke 2000). In the present study we focus on the effect of land use type, landscape structure and habitat quality on the species & A. Torma ( ) Á P. Csa´sza´r diversity and composition patterns of true bugs in the Department of Ecology, University of Szeged, Ko¨ze´p fasor 52, Szeged 6726, Hungary agricultural landscape of the lower reach of the Tisza River e-mail: [email protected] Basin. 123 J Insect Conserv The River Tisza is the second largest river in Hungary they represent an ecologically diverse group including both and presumably the most characteristic river in the Carpa- predaceous and herbivorous species with different degrees thian Basin which is a separated biogeographical region of food specialization (Dolling 1991; Schuh and Slater (Pannon region) in Europe. The Tisza is 965 km long and its 1995; Schaefer and Panizzi 2000) and the various trophic catchment includes most of the Carpathian Mountains levels are supposed to be influenced by different factors covering approximately 157,000 km2 (Alfo¨ldi and (Zurbru¨gg and Frank 2006; Hines et al. 2005); moreover, Schweitzer 2003; Sommerwerk et al. 2009). The Tisza River influential factors could differ between the degrees of Basin is regarded as an important core area and also a green feeding specialization (Jonsen and Fahrig 1997). Finally, corridor (Galle´ et al. 1995 Galle´ 2005;IUCN1995), con- Heteroptera is a good indicator group of total insect taining highly endangered habitats (Decamps 1993; Frank- diversity in agricultural ecosystems (Duelli and Obrist lin 1993) and contributing to the conservation of 1998). biodiversity in Europe (Sze´p 1997; Sommerwerk et al. Here we address the following: 2009). The Tisza River Basin has high plant and animal 1. To reveal the effects of environmental controls (i.e. diversities (Galle´ 2005; Sommerwerk et al. 2009) and land use type, surrounding landscape structure and unique insect species as the endemic Tisza mayfly (Palin- vegetation) on the structure, species composition and genia longicauda Olivier, 1791) and the European stalk- distribution of true bugs. eyed fly (Sphyracephala europaea Papp et Fo¨ldva´ri 1997). 2. To test the significance of the environmental controls Although the major works of the so-called ‘‘regulation of on the species richness and abundance of true bugs Tisza’’ in the nineteenth century divided the historical belonging to different trophic levels (i.e. herbivores floodplain by dikes into flooded and nonflooded parts, the and predators) and with different ranges of host-plant extensively used, mosaic landscape preserved several nat- specialization (i.e. generalist and specialist ural habitats, i.e. pastures, woody pastures and hay-mead- herbivores). ows until the 1950s (Dea´k 2007; Sendzimir et al. 2008), and 3. To test whether the species composition of Heteroptera the traditional, Hungarian land use types (see e.g. Hortoba´gy assemblages differs significantly within a dike as a a site of the UNESCO World Heritage) maintained high linear landscape element at the landscape scale. biodiversity (Aradi and Lengyel 2003). Intensification of agriculture during the socialist era, reduced the area of grasslands (Dea´k 2007). Nowadays, the remaining grass- lands are enclosed between highly modified landscape ele- Materials and methods ments, i.e. arable fields and forest plantations of mainly non- native tree species. In this agricultural landscape mosaic, the Study sites and sampling dikes form grassland-strip habitats. Dikes function as grassland habitats and corridors for insects (Galle´ et al. Two habitat complexes of the lower Tisza-valley were 1995; Krausz et al. 1995) and are of considerable length: selected for sampling in Csongra´d county (Fig. 1). The approximately 4,500 km of primary and secondary dikes structure of the landscape and the land use differed exist along the River Tisza and its tributaries in Hungary between the two habitat complexes. The Ta´pe´ habitat (Sendzimir et al. 2008). In general, linear grassy elements complex is situated near Szeged, where the landscape are supposed to enlarge insect habitats and to reduce frag- consists of arable fields with small patches of meadows, old mentation (Nicholls et al. 2001; Pywell et al. 2005;O¨ ckin- fields and forest plantations embedded in the matrix of ger and Smith 2007;So¨derstro¨m and Hedblom 2007), thus arable fields. The Do´c habitat complex lies approximately the conservation, restoration and management of linear 30 km north of Szeged in a more natural landscape. Higher grassy elements of agricultural landscape is of concern in proportion of semi-natural grasslands and forests occur in many parts of Europe (e.g. Noordijk et al. 2009; Tikka et al. the latter. In both of the two habitat complexes we studied 2001; Saarinen et al. 2005; de la Pen˜a et al. 2003). typical land use types, i.e. hay-meadows, pastures, old Heteroptera is an ideal group to study diversity patterns fields and dikes. Six and four grassland habitats were in fragmented and managed grasslands as firstly they are selected for the study in Do´c and Ta´pe´ habitat complexes, known to be influenced by various vegetation properties respectively (for further details, see Table 1). In each (Sanderson et al. 1995; Schwab et al. 2002; Littlewood habitat, Heteroptera assemblages were sampled in three et al. 2009; Bro¨ring and Wiegleb 2005; Frank and Ku¨nzle plots. The distance between the plots within a grassland 2006; Torma and Ko¨rmo¨czi 2009; Torma et al. 2010; Galle´ habitat was approximately 250 m. True bugs were col- et al. 2010) and respond quickly to grassland disturbances lected by sweep netting, which is an adequate technique for such as mowing, grazing, burning and polluting (Morris sampling the structure and species diversity of assemblages 1973, 1975, 1979, 1990; Bra¨ndle et al. 2001). Secondly, (Remane 1958; Standen 2000; Coscaron et al. 2009). In 123 J Insect Conserv radius, to reveal the scale which had the major influence on the assemblages. Finally, according to land use type; hay- meadow, pasture, old field and dike habitats were distin- guished and they were defined as factors in the analyses. Data analysis To show the natural grouping of samples according to the species composition of true bugs, Non-metric Multidi- mensional Scaling (NMDS) with Bray-Curtis dissimilarity was used (Legendre and Legendre 1998; Oksanen 2011). We used permutational MANOVA (Permanova) based on Bray-Curtis similarity (Vegan R package, Oksanen et al. Fig. 1 The location of the studied habitat-complexes in Hungary. The above and below black circles mark Do´c and Ta´pe´ habitat- 2010) to reveal the variation within the dike habitat in the complexes, respectively species composition of true bugs.