Early View (EV): 1-EV How do low dispersal species establish large range sizes? The case of the water beetle Graphoderus bilineatus Lars Lønsmann Iversen, Riinu Rannap, Philip Francis Thomsen, Jos Kielgast and Kaj Sand-Jensen L. L. Iversen (lliversen@bio.ku.dk) and K. Sand-Jensen, Freshwater Biological Laboratory, Biological Inst., Univ. of Copenhagen, Helsingørsgade 51, DK-3400 Hillerød, Denmark. – R. Rannap, Inst. of Ecology and Earth Sciences, Univ. of Tartu, Vanemuise 46, EE-51014 Tartu, Estonia. – P. F. homsen and J. Kielgast, Centre for GeoGenetics, Natural History Museum of Denmark, Univ. of Copenhagen, Øster Voldgade 5-7, DK-1350 Copenhagen, Denmark. Species’ dispersal abilities have been considered a major driving force in establishment and maintenance of large range sizes. However, recent studies question the general validity of this relationship because the relationship between dis- persal ability and range size might in some cases be less important than species phylogeny or local spatial attributes. In this study we used the water beetle Graphoderus bilineatus a philopatric species of conservation concern in Europe as a model to explain large range size and to support efective conservation measures for such species that also have limited dispersal. We recorded the presence/absence of G. bilineatus and measured 14 habitat and 20 landscape variables at 228 localities in Estonia, Poland and Sweden within the core range of the species. Using information theory and average multivariate logistic regression models we determined that presence of G. bilineatus depended on landscape connectiv- ity, distance to a possible source habitat, and stability of the site; however, speciicity of habitat characteristics was not vital for the species. We reason that the large range of G. bilineatus is best explained by the historical combination of lakes, river systems and wetlands which used to be highly connected throughout the central plains of Europe. Our data suggest that a broad habitat niche can prevent landscape elements from becoming barriers for species like G. bilineatus. herefore, we question the usefulness of site protection as conservation measures for G. bilineatus and similar philopat- ric species. Instead, conservation actions should be focused at the landscape level to ensure a long-term viability of such species across their range. At the frontiers of ecology, biogeography, and interest in climate-driven species extinction, there is considerable inter- est in the distributions and range sizes of species (Brown et al. 1996, Gaston 2006, Hof et al. 2011). For a broad range of taxa, dispersal ability appears to be a major driving force in establishment of large range sizes (Brown et al. 1996, Gaston 1996, Gutierrez and Menendez 1997, Mora and Robertson 2005, Lowry and Lester 2006). However, in a recent review, Lester et al. (2007) questioned the general validity of this relationship. In addition, recent studies have shown that the positive relationship between dispersal ability and range size may, in some cases, be an artifact of phylogenetic bias or local spatial attributes (Gove et al. 2009, Garcia-Barros and Benito 2010, Mora et al. 2011). hus dispersal ability should be regarded as only one of several factors that may shape range size of a species (Lester et al. 2007). Dennis et al. (2005), for example, have suggested that species ranges are fundamentally a result of interaction between niche-breath and dispersal ability and niche- breadth itself is often regarded as an important characteri- stic for establishing large range sizes (Gaston 2006). Nonetheless, few studies have empirically addressed the basis of species range sizes. In particular, little is known about how species with low dispersive power attain large range sizes and what processes drive the persistence of such large ranges. Habitat and landscape features, which afect the local distribution of species, are generally regarded as decisive for the viability of populations at the local scale and, thus, the distribution of species at the global scale (Joly et al. 2001, Bakker et al. 2002, Lowe and Bolger 2002, Armstrong 2005). In this study we explored the paradoxical distri- bution pattern of a philopatric but widespread aquatic insect species, the aquatic water beetle Graphoderus bilineatus, and attempted to understand its range size in rela- tion to the factors that limit local persistence. We examined the habitat and landscape dependencies of this species across three diferent landscapes in northern and eastern Europe. Graphoderus bilineatus uses a well-deined habitat (lakes, ponds and other stagnant waters), and has a large European range size despite low dispersal capacity and is thus an ideal candidate for the purposes of this study. Graphoderus bilineatus is considered a threatened species throughout its western distribution range where its occurrence is rare and patchy (Nilsson and Holmen 1995, Foster 1996, Hendrich and Balke 2000). It is strictly pro- tected within the EU-countries (Council of the European Ecography 36: 001–008, 2013 doi: 10.1111/j.1600-0587.2013.00001.x © 2013 he Authors. Ecography © 2013 Nordic Society Oikos Subject Editor: John R. Spence. Accepted 4 February 2013