Department of Physics, Chemistry and Biology Master Thesis Comparison of saproxylic beetle assemblages on four different broad-leaved tree species in south-eastern Sweden Helena Johansson LiTH-IFM- Ex--11/2428--SE Supervisor: Nicklas Jansson, Linköpings universitet Examiner: Anders Hargeby, Linköpings universitet Department of Physics, Chemistry and Biology Linköpings universitet SE-581 83 Linköping, Sweden Avdelning, Institution Datum Division, Department Date Avdelningen för biologi Instutitionen för fysik och mätteknik 2011-06-03 Språk Rapporttyp ISBN Language Report category LITH-IFM-A-EX--—11/2428—SE __________________________________________________ Svenska/Swedish Licentiatavhandling ISRN x Engelska/English x Examensarbete __________________________________________________ C-uppsats x D-uppsats ________________ Övrig rapport Serietitel och serienummer ISSN Title of series, numbering _______________ Handledare URL för elektronisk version Supervisor: Nicklas Jansson Ort Location: Linköping Titel Title: Comparison of saproxylic beetle assemblages on four different broad-leaved tree species in south- eastern Sweden Författare Author: Helena Johansson Sammanfattning Abstract: Old hollow trees have declined in Europe and many saproxylic (wood-dwelling) beetles dependent on them are threatened. Several studies have been done on old hollow oaks and they have been shown to harbour a species-rich saproxylic beetle fauna. However, other broad-leaved trees might also be important to consider as supporting habitats. The aim of this study was to investigate to what extent saproxylic beetles are tree genus specialists. Pitfall traps and window traps were used to compare the saproxylic beetle fauna in oak, ash, norway maple and small- leaved lime in an area dominated by old oaks. 5,501 specimens of saproxylic beetles were found, belonging to 239 species of which 27 species were red-listed. There were significant differences in the saproxylic species composition between the four tree species, but with large overlaps. The saproxylic species found in oak overlapped to 66 % with norway maple, to 67 % with ash and to 70 % with small-leaved lime. About one third of the species in this study seem to be tree genus specialists. The conclusion is that other broad-leaved trees are important to consider in models as supporting habitats for oaks. However, to be able to save the whole fauna of saproxylic beetles, trees of all different tree species are needed. Nyckelord Keyword: Conservation, coleoptera, beetles, saproxylic, broad-leaved trees, hollow, preferences Table of contents 1 Abstract ....................................................................................................................... 2 2 Introduction ................................................................................................................. 2 2 Material and methods .................................................................................................. 3 2.1. Study sites ........................................................................................................... 3 2.2 Beetle trapping ..................................................................................................... 4 2.3 Identification of saproxylic beetles ...................................................................... 5 2.4 Data analyses ....................................................................................................... 5 3 Results ......................................................................................................................... 6 3.1 Obligate saproxylic beetles .................................................................................. 6 3.2 Facultative saproxylic beetles .............................................................................. 7 4 Discussion ................................................................................................................. 11 4.1 Conservation implications ................................................................................. 13 5 Acknowledgement .................................................................................................... 13 6 References ................................................................................................................. 13 Appendix 1. The hollow trees ...................................................................................... 16 Appendix 2. Saproxylic species table .......................................................................... 18 1 Abstract Old hollow trees have declined in Europe and many saproxylic (wood-dwelling) beetles dependent on them are threatened. Several studies have been done on old hollow oaks and they have been shown to harbour a species-rich saproxylic beetle fauna. However, other broad-leaved trees might also be important to consider as supporting habitats. The aim of this study was to investigate to what extent saproxylic beetles are tree genus specialists. Pitfall traps and window traps were used to compare the saproxylic beetle fauna in oak, ash, norway maple and small-leaved lime in an area dominated by old oaks. 5,501 specimens of saproxylic beetles were found, belonging to 239 species of which 27 species were red-listed. There were significant differences in the saproxylic species composition between the four tree species, but with large overlaps. The saproxylic species found in oak overlapped to 66 % with norway maple, to 67 % with ash and to 70 % with small-leaved lime. About one third of the species in this study seem to be tree genus specialists. The conclusion is that other broad-leaved trees are important to consider in models as supporting habitats for oaks. However, to be able to save the whole fauna of saproxylic beetles, trees of all different tree species are needed. Keywords: Conservation, coleoptera, beetles, saproxylic, broad-leaved trees, hollow, preferences. 2 Introduction In Europe, many species dependent on old trees are threatened, due to habitat loss (Speight 1989). Old-growth temperate deciduous forests have decreased to a small fraction from their previous large distribution, thus old trees have disappeared from many regions (Hannah et al. 1995). Until the nineteenth century, old trees were common in pasture woodland and wooded meadows, but changes in land use have reduced the distribution of old trees (Kirby & Watkins 1998). When trees get older, structures serving as microhabitats for many organisms start to develop (Sverdrup-Thygeson et al. 2009). One of these microhabitats is trunk hollows that start to develop when the trees are about 200 years old (Ranius 2009a). Hollows in old trees provide important habitats for mammals, birds and many invertebrates. Tree hollows in the trunks often contain wood mould, which is loose wood colonized with fungi and remains from bird nests, insects and dead leaves (Ranius 2002a, Jansson et al. 2009a). Hollows with wood mould in old trees harbour a specialized insect fauna, among them saproxylic insects (Dajoz 2000). Saproxylic insects are insects that some part of their life cycle are dependent on dead wood (Speight 1989). Jonsell et al. (1998) suggest that the richness and composition of the red-listed saproxylic invertebrate species in boreal forests differ between different tree species. Many saproxylic insects were classified as specific to host tree genera and some were classified as monophagus to a single tree species. Results from field studies are mixed. A field study of saproxylic beetles on logging residues of aspen, birch, oak and spruce showed that the assemblages differed between tree species (Jonsell et al 2007) but Irmler et al (1996) found small differences between tree species on logs and stumps of three different tree species (beech, alder and spruce). Hollow oaks have been shown to harbour a rich saproxylic beetle fauna and it has been shown that different qualities of hollows and oak individuals affect the fauna (Ranius 2002b). However, there seem to be no systematic sampling comparing the saproxylic fauna in hollows between tree species. 2 The aim of this study was to investigate if different saproxylic beetles prefer hollow trees of different species. To what extents are saproxylic beetles tree genus specialists? A better knowledge about the habitat requirements of rare saproxylic beetles can be useful in landscape planning and conservation of this fauna. Old oaks have been in focus in many studies but other broad-leaved tree species might also be important to consider as supporting habitats. Therefore it is important to know which saproxylic beetles that utilize other broad-leaved tree genera and how specialized they are. This can be used to get better models in conservation and management planning. 2 Material and methods 2.1. Study sites This study was conducted in one of the few remaining landscapes in Northern Europe with high density of old oaks, in Östergötland, south-eastern Sweden (Antonsson & Wadstein 1991). Hollow trees of the different tree species, were selected from a database at the County Administration Board of Östergötland with old and hollow trees that they had registered the past 10 years was used. In a study area of approximately 10 x 30 km2, 48 hollow trees were selected, clustered at 10 study sites (Figure 1). At each site, at least one hollow oak (Quercus robur) was examined together with one or several hollow tree species of ash (Fraxinus excelsior), norway maple (Acer platanoides) and/or small-leaved lime (Tilia cordata) (Figure