Linking mesoscale landscape heterogeneity and biodiversity: gardens and tree cover significantly modify flower-visiting beetle communities

Landscape Ecol https://doi.org/10.1007/s10980-019-00822-x (0123456789().,-volV) ( 01234567 89().,-volV) RESEARCH ARTICLE Linking mesoscale landscape heterogeneity and biodiversity: gardens and tree cover significantly modify flower-visiting beetle communities Christopher W. Foster . Jessica L. Neumann . Graham J. Holloway Received: 30 August 2018 / Accepted: 20 April 2019 Ó The Author(s) 2019 Abstract Context Maintaining biodiversity in multifunction landscapes is a significant challenge. Planning for the impacts of change requires knowledge of how species respond to landscape heterogeneity. Some insect groups are known to respond to heterogeneity at the mesoscale, defined here as hundreds of metres. However, for many taxa these effects are poorly known. Objectives To identify key elements of mesoscale landscape heterogeneity influencing community composition in flower-visiting beetles, and whether landscape explains any variation in beetle communities beyond that driven by immediate habitat cover. Methods Flower-visiting beetles were sampled from 36 transects, laid out using a 6 km2 grid located in southern Britain. Landscape heterogeneity was measured for 30 and 200 m buffers around the transects and the relative response of beetle communities to each assessed using ordination analyses followed by variation partitioning. C. W. Foster (&)
G. J. Holloway Centre for Wildlife Assessment and Conservation, School of Biological Sciences, University of Reading, Reading, UK e-mail: J. L. Neumann Department of Geography and Environmental Science, University of Reading, Reading, UK Results The composition of immediately adjacent habitat (30 m) and mesoscale landscape heterogeneity (200 m) explained unique portions of the variation in flower-visiting beetle communities. A number of species, including those affiliated with deadwood habitats, were positively linked to tree cover in the surrounding mesoscale landscape. Gardens covered a smaller area than trees but modified beetle communities to the same extent. Conclusions The local abundance of some flowervisiting beetles is modified by the composition of the surrounding landscape. Results highlight the importance of tree cover for maintaining insect biodiversity in agricultural landscapes, while suggesting that gardens associated with small urban areas may have a disproportionate influence on biodiversity. Keywords Flower-visiting beetles
Landscape heterogeneity
Landscape mosaics
Mesoscale landscape
Urban biodiversity Introduction The need for landscapes to maintain or even exceed current levels of biodiversity is well recognised, with both governmental and non-governmental conservation strategies increasingly adopting landscape-scale approaches (Lawton et al. 2010). This is a significant 123 Landscape Ecol challenge in lowland mosaic landscapes where urban development and agricultural intensification have fragmented habitats over long timescales, with variable but consistently negative impacts on biodiversity (Andrén 1994; Haila 2002; Fahrig 2003; Kappes et al. 2009; Fletcher et al. 2018). Successful management of landscapes for wildlife requires an understanding of how landscape heterogeneity determines patterns of species distribution and modifies community composition. Landscape heterogeneity can be considered a function of both landscape composition—the amounts of different habitat cover types within the landscape— and landscape configuration, i.e., the heterogeneity of their spatial arrangement (Fahrig et al. 2011). Landscape heterogeneity is recognised as a key driver of species distributions in lowland agricultural landscapes for many taxonomic groups including birds (Fuller et al. 1997; Virkkala et al. 2013; Neumann et al. 2016a), bees and wasps (Fabian et al. 2013; Steckel et al. 2014), mammals (Mortelliti et al. 2011; Bender and Fahrig 2012) and plants (Jules and Shahani 2003). However, whilst landscape conservation or landscape planning tends to consider landscape from an anthropogenic point of view, perhaps at a kilometreswide scale, there is no single ‘landscape scale’ relevant to all species groups (Schweiger et al. 2005; Ekroos et al. 2013; Fuentes-Montemayor et al. 2017). Highly mobile species groups such as birds or Orthoptera respond to landscape composition even when examined at fairly broad scales, e.g., cricket species richness in 10-km2 (Cherrill 2015) or bird community composition in 2-km tetrads (Neumann et al. 2016a). For invertebrates with more limited dispersal power, landscape heterogeneity within a radius of hundreds of metres is important, as seen for ground beetles (Carabidae) at a 400-m radius (Barbaro et al. 2007; Barbaro and Van Halder 2009) and Lepidoptera, hoverflies (Syrphidae) and bees at 600 m (Sjödin et al. 2008). In common with Barbaro et al. (2007), we describe this as a mesoscale landscape. This spatial scale is comparable to the size of common units of land management, with many new housing developments in the United Kingdom, for example, in the range of 5–20 ha. Links between mesoscale landscape heterogeneity and biodiversity might therefore be successfully applied to the planning of new habitat networks as 123 mitigation for single housing developments, or to the spatial optimisation of agri-environment schemes at a farm scale. These processes would ideally take account of biodiversity in all elements of the landscape, but whilst the synergistic effect of complete landscape mosaics has been shown to have an impact on community composition, species communities drawn from multiple mosaic components are less often considered (Bennett et al. 2006; Neumann et al. 2016b; Duflot et al. 2017). This is perhaps due to the challenge of gathering data from multiple habitats and taxonomic groups; methods that rapidly capture a ‘snapshot’ of landscape biodiversity by sampling a single species community would facilitate this. Flower-visiting beetles cover a range of habitat affiliations within a single well-studied order, but few studies consider the effect of landscape heterogeneity on their distributions (Sjödin et al. 2008; Horak 2014). Among the flower-visitors are saproxylic beetles (one of the most threatened groups of species in Europe (Cálix et al. 2018) as well as many phytophagous and predatory species associated with tall sward and scrub habitats. By focussing on flower-visiting beetles, this study aims to provide a window into how mesoscale landscape heterogeneity influences the distribution of a diverse insect assemblage across a lowland agricultural mosaic. Sampling was carried out on linear patches of flowering plants in the Apiaceaea (e.g., cow parsley, Anthriscus sylvestris, and hogweed, Heraclium sphondylium), which are very abundant in a range of lowland habitats across Northern Europe. Apiaceaea attract a diverse variety of insect visitors (Willis and Burkill 1892; Zych 2007a) and are key plant species in some ecological networks (Zych 2007b; Poco (...truncated)