PRIMARY RESEARCH PAPER Environmental and spatial control of ostracod assemblages in the Western Carpathian spring fens M. Zhai • O. Nova ´c ˇek • D. Vy ´ravsky ´ • V. Syrova ´tka • J. Bojkova ´ • J. Heles ˇic Received: 17 January 2014 / Revised: 30 October 2014 / Accepted: 3 November 2014 / Published online: 15 November 2014 Ó European Union 2014 Abstract The effect of environment and species dispersal limitations may both significantly affect the structure of ecological metacommunities but there have been a relatively few attempts to separate their effects in aquatic assemblages. In this paper, we tested the relative importance of environment and space on the ostracod assemblages on a regional scale (encom- passing ca 15,800 km 2 ) in 74 permanent helocrene springs. We used Canonical Correspondence Analysis and Variation Partitioning to test the unique and shared effects of environment and space, represented by Principal Coordinates of Neighbor Matrices. We found that ostracod assemblages were significantly influenced by environment (mainly the mineral con- tent and TOC) and space (roughly the west-east direction); the shared effect was relatively low. A unique effect of space was found for both species strongly associated with spring habitats and for euryoecious species found in the springs. We suggest that the passive dispersal in ostracods is random and infrequent between the isolated spring fens and produces spatially structured assemblages. Keywords Ostracoda Á Spring fens Á Environmental filtering Á Mineral content Á Spatial structure Á Dispersal Introduction Environmental conditions that sort species, according to their ecological requirements, and the spatial configuration of sites, (i.e., geographical distances together with possible barriers between sites) that influences species dispersal, have been recognized as two of the major mechanisms driving ecological metacommunities (Leibold et al., 2004; Chase, 2005, Gravel et al., 2006; De Bie et al., 2012). Assessment of the relative importance of environmental filtering and dispersal has been used to increase our understanding of the key processes structuring various assemblages in ecological studies (e.g., Cottenie, 2005; Ha ´jek et al., 2011; Chytry ´ et al., 2012). The research into aquatic invertebrate metacommunities has been so far focused mainly on environmental filtering (e.g., Glazier, 1991), but spatial issues and the dispersal has received attention only recently (Heino & Mykra ¨, 2008; Heino et al., 2010; Gro ¨nroos et al., 2013). In the connected system of running waters, there seem to be a few limits on the dispersal of aquatic invertebrates, which results in a lack of spatial structure (e.g., Heino & Mykra ¨, 2008; Gro ¨nroos et al., 2013). Springs, however, are isolated habitats scattered within a mosaic of terrestrial Handling editor: Stuart Anthony Halse. M. Zhai (&) Á O. Nova ´c ˇek Á D. Vy ´ravsky ´ Á V. Syrova ´tka Á J. Bojkova ´ Á J. Heles ˇic Department of Botany and Zoology, Faculty of Science, Masaryk University, Kotla ´r ˇska ´ 2, 61137 Brno, Czech Republic e-mail: marie.zhai@yahoo.com 123 Hydrobiologia (2015) 745:225–239 DOI 10.1007/s10750-014-2104-1