P3-6: Biodiversity Patterns and Processes Across Landscapes Differing in Local Habitat Composition and Configuration

PhD Student: Felipe Libran
Supervisor: Prof. Dr. Teja Tscharntke
Group: Crop Sciences, Division Agroecology

Project Description:
Local biodiversity and associated processes are shaped by landscape heterogeneity, which is meanwhile a fundamental concept in ecology (Wiens, 2002). Landscapes differ widely in their degree of heterogeneity, from homogeneous landscapes dominated by cropland to heterogeneous landscapes dominated by natural-habitat. Two components of landscape heterogeneity are functionally particularly important: the compositional heterogeneity, which refers to the variety of different cover types, and the configurational heterogeneity, which refers to the geometric complexity of spatial patterning of cover types (Fahrig et al., 2011; Villard and Metzger, 2014). The functional importance of landscape heterogeneity for biodiversity comes from the different requirements of species and species groups with respect to food and nesting resources. Species differ also in dispersal abilities (often positively linked to body size) and thereby experience the landscape matrix (surrounding habitat patches) at different spatial scales, which affects food web interactions at different trophic levels (Gagic et al., 2011). Resource specialization and dispersal ability are two major (out of several) traits that can be used to characterize functional composition of species groups, food web structure (quantitative bipartite interaction networks) and the functional importance of landscape heterogeneity.

In this project, we aim at so far little tested hypotheses (Tscharntke et al., 2012), in particular the cross-habitat spillover hypothesis (the exchange of organisms among different habitats), the functional trait-selection hypothesis (considering that species differ in how they experience the surrounding landscape), and the dominance of beta diversity hypothesis (quantifying the role of dissimilar community composition across landscapes). We specifically focus on the unknown differences between urban and rural landscapes with respect to how landscape heterogeneity and habitat connectivity affect community structure. For example, we test the (not yet validated) idea that isolation plays a bigger role for local extinction and species richness in urban than rural areas, enhancing extinction rates, but also dissimilarity of community composition. If community dissimilarity (i.e. beta diversity) is high, negative effects of habitat fragmentation should play only a minor role (Tscharntke et al., 2012; Lasky and Keitt, 2013; Rösch et al., 2013). Further, habitat identity (for example, mass-flowering vs. non-flowering patches) matters for many organisms spilling over from one habitat to the other (Holzschuh et al., 2011; Samnegård et al., 2011). We will combine experimental approaches (creating standardized resource patches, using exclusion cages, manipulating access to resources) with quantitative sampling of a range of species and trait groups (from plants and insects to birds) and ecological processes such as pollination and biological control. As in P3-5, fine scale data on landscape structure and habitat composition will be collected using unmanned aerial vehicles (UAVs).

Our project aims to connect empirical approaches with state-of-the-art statistical modeling (P3-1, Scherber et al., 2012), GIS-based spatio-temporal autocorrelation (P3-3) and mathematical modeling (P3-7, Vollhardt et al., 2010) to improve our understanding of biodiversity patterns and processes across spatial scales. We build on the experience and results from our former RTG projects, which focused on biodiversity effects of habitat fragmentation. Exchange of ideas for the coming period will specifically take place with P3-11 (comparing optimal-size valuations of farms with organisms) and P3-14 (animal traits).

Fahrig, L., Baudry, J., Brotons, L., Burel, F. G., Crist, T. O., Fuller, R. J., Sirami, C., Siriwardena, G. M. and Martin, J.-L. (2011), Functional landscape heterogeneity and animal biodiversity in agricultural landscapes, Ecology Letters 14, 101-112.

Gagic, V., Tscharntke, T., Dormann, C. F., Gruber, B., Wilstermann, A. and Thies, C. (2011), Food web structure and biocontrol in a four-trophic level system across a landscape complexity gradient, Proceedings of the Royal Society B: Biological Sciences 278, 2946-2953.

Holzschuh, A., Dormann, C. F., Tscharntke, T. and Steffan-Dewenter, I. (2011), Expansion of mass- flowering crops leads to transient pollinator dilution and reduced wild plant pollination, Proceedings of the Royal Society B: Biological Sciences 278, 3444-3451.

Lasky, J. R. and Keitt, T. H. (2013), Reserve size and fragmentation alter community assembly, diversity, and dynamics, The American Naturalist 182, E142-E160.

Rösch, V., Tscharntke, T., Scherber, C. and Batáry, P. (2013), Landscape composition, connectivity and fragment size drive effects of grassland fragmentation on insect communities, Journal of Applied Ecology 50, 387-394.

Samnegård, U., Persson, A. S. and Smith, H. G. (2011), Gardens benefit bees and enhance pollination in intensively managed farmland, Biological Conservation 144, 2602-2606.

Scherber, C., Lavandero, B., Meyer, K. M., Perovic, D., Visser, U., Wiegand, K. and Tscharntke, T. (2012), Scale effects in biodiversity and biological control: Methods and statistical analysis, in G. M. Gurr, S. D. Wratten, W. E. Snyder and D. M. Y. Read, eds, 'Biodiversity and Insect Pests', John Wiley & Sons, Ltd, Chichester, UK, pp. 121-138.

Tscharntke, T., Tylianakis, J. M., Rand, T. A., Didham, R. K., Fahrig, L., Batáry, P., Bengtsson, J., Clough, Y., Crist, T. O., Dormann, C. F., Ewers, R. M., Fru?nd, J., Holt, R. D., Holzschuh, A., Klein, A. M., Kleijn, D., Kremen, C., Landis, D. A., Laurance, W., Lindenmayer, D., Scherber, C., Sodhi, N., Ste_an-Dewenter, I., Thies, C., van der Putten, W. H. and Westphal, C. (2012), Landscape moderation of biodiversity patterns and processes - eight hypotheses, Biological Reviews 87, 661-685.

Villard, M.-A. and Metzger, J. P. (2014), Beyond the fragmentation debate: a conceptual model to predict when habitat con_guration really matters, Journal of Applied Ecology. doi: 10.1111/1365-2664.12190.

Vollhardt, I. M. G., Bianchi, F. J. J. A., Wäckers, F. L., Thies, C. and Tscharntke, T. (2010), Spatial distribution of flower vs. honeydew resources in cereal fields may affect aphid parasitism, Biological Control 53, 204-213.

Wiens, J. A. (2002), Central concepts and issues of landscape ecology, in K. Gutzwiller, ed., 'Applying Landscape Ecology in Biological Conservation', Springer, New York, pp. 3-21.