Long-Term Development of Different Grassland Insect Communities In
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GÖTTINGER ZENTRUM FÜR BIODIVERSITÄTSFORSCHUNG UND ÖKOLOGIE − GÖTTINGEN CENTRE FOR BIODIVERSITY AND ECOLOGY − Long-term development of different grassland insect communities in Central Europe since the 1950s Dissertation zur Erlangung des Doktorgrades der Mathematisch-Naturwissenschaftlichen Fakultäten der Georg-August-Universität Göttingen vorgelegt von Dipl. biol. Sebastian Schuch aus Leimen Göttingen, Mai 2011 Referent: Prof. Dr. Matthias Schaefer Korreferent: Prof. Dr. Stefan Vidal Tag der mündlichen Prüfung: 14. Juli 2011 1 2 Table of contents Summary .................................................................................................................................... 5 Introduction ................................................................................................................................ 8 Why is long-term research necessary? ................................................................................... 8 General problems in long-term research ................................................................................ 9 Previous entomological long-term research......................................................................... 11 Chapter outline ..................................................................................................................... 12 Chapter 1 Long-term population trends in three grassland insect groups: a comparative analysis of the years 1951 and 2009................................................................................................................. 14 Abstract ................................................................................................................................ 16 Introduction .......................................................................................................................... 16 Material and methods ........................................................................................................... 19 Results .................................................................................................................................. 23 Discussion ............................................................................................................................ 28 Acknowledgements .............................................................................................................. 33 References ............................................................................................................................ 34 Chapter 2 Minor changes in orthopteran assemblages of Central European protected, dry grasslands during the last 40 years............................................................................................................. 38 Abstract ................................................................................................................................ 40 Introduction .......................................................................................................................... 41 Material and methods ........................................................................................................... 44 Results .................................................................................................................................. 49 Discussion ............................................................................................................................ 54 Acknowledgements .............................................................................................................. 57 References ............................................................................................................................ 58 3 Chapter 3 Long-term decline in abundance of planthoppers and leafhoppers (Auchenorrhyncha) in Central European protected dry grasslands.............................................................................. 62 Abstract ................................................................................................................................ 64 Introduction .......................................................................................................................... 65 Material and methods ........................................................................................................... 68 Results .................................................................................................................................. 73 Discussion ............................................................................................................................ 79 Acknowledgements .............................................................................................................. 83 References ............................................................................................................................ 83 Synopsis ................................................................................................................................... 88 General long-term trends in the investigated insect communities ....................................... 88 The influence of the environment ........................................................................................ 91 Remarks on some species..................................................................................................... 92 Implications for future work and outlook ............................................................................ 94 References ................................................................................................................................ 96 Zusammenfassung.................................................................................................................. 101 Danksagung............................................................................................................................ 105 Curriculum vitae..................................................................................................................... 106 Appendix ................................................................................................................................ 107 Explanations to Marchand’s and Schuch’s data................................................................. 107 Explanations to Schiemenz’s and Schuch’s data ............................................................... 107 Marchand’s and Schuch’s data........................................................................................... 109 Schiemenz’s and Schuch’s data ......................................................................................... 131 4 Summary Central European landscape considerably changed during the second half of the 20 th century. These changes are probably mainly caused by modern agriculture. Today, Central Europe consists of a patchwork of intensively used arable fields and grasslands (~50% of total land cover) mixed with forests (mainly plantations, ca. 30%), human settlements, and nature reserves. The implications of the long-term changes in the landscape structure (i.e. effects of fragmentation, of diminishing population sizes, edge effects etc.) are largely understood, but very few empirical studies give data on the long-term consequences for the native fauna. In this context the insects are a very good example. Although the insects comprise a wide range of taxa and are often the most dominant group in a given ecosystem, very little is known about the real-world development of insect populations during the last five decades, in which the most pronounced changes in agricultural practices occurred. The aim of this thesis was to detect long-term shifts in species richness, species composition, and species abundance of various insect groups. It was based on the results of two historical studies. The first one was conducted by Marchand in 1951, while the second survey was done by Schiemenz between 1963 and 1967. Both studies were repeated independently between 2008 and 2010 using the same sampling techniques at the same sites during a similar time frame as in the historical data. In the first study, Auchenorrhyncha, Heteroptera, and Orthoptera were re-sampled at nine sites (mainly pastures) in Lower-Saxony (federal state of northern Germany). In the second, auchenorrhynchan and orthopteran assemblages were investigated in dry grasslands of eastern Germany. Here, 26 sites were re- sampled, which were equally distributed in Brandenburg, Thuringia and Saxony. Whereas original data (including abundance) of the pastures study were completely available, the abundance data for Orthoptera of dry grassland unfortunately were incomplete and no quantitative comparisons were possible. However, dry grassland data on Auchenorrhyncha 5 were preserved and could thus be compared to our new, in this case quantitative survey. A comparison capturing three years (1964 to 1966 vs. 2008 to 2010) additionally allowed us to assess interannual variability of auchenorrhynchan abundance. In the first investigation – based on Marchand’s work – we found that the insect communities exhibited no consistent trends between years. Species richness of Auchenorrhyncha and Heteroptera increased on the plot as well as on landscape level but it remained unchanged for Orthoptera. While the abundance of auchenorrhynchans and orthopterans decreased significantly, the quantity of Heteroptera increased. There was a strong trend towards homogenisation in species composition for Heteroptera and also,