RESEARCH PAPER A latitudinal gradient in seed nutrients of the forest herb Anemone nemorosa P. De Frenne 1 , A. Kolb 2 , B.J. Graae 3 , G. Decocq 4 , S. Baltora 5 , A. De Schrijver 1 , J. Brunet 6 , O. Chabrerie 4 , S.A.O. Cousins 7 , R. Dhondt 1 , M. Diekmann 2 , R. Gruwez 1 , T. Heinken 8 , M. Hermy 9 , J. Liira 10 , R. Saguez 4 , A. Shevtsova 11,12 , C.C. Baskin 13 & K. Verheyen 1 1 Laboratory of Forestry, Ghent University, Melle-Gontrode, Belgium 2 Vegetation Ecology and Conservation Biology, Institute of Ecology, University of Bremen, Bremen, Germany 3 Department of Biology, Norwegian University of Science and Technology, Trondheim, Norway 4 Plant Biodiversity Lab, Universite ´ de Picardie Jules Verne, Amiens, France 5 BioPI, EA 3900, Universite ´ de Picardie Jules Verne, Amiens, France 6 Southern Swedish Forest Research Centre, Swedish University of Agricultural Sciences, Alnarp, Sweden 7 Department of Physical Geography and Quaternary Geology, Stockholm University, Stockholm, Sweden 8 Biodiversity and Systematic Botany, University of Potsdam, Potsdam, Germany 9 Division Forest, Nature and Landscape, K.U. Leuven, Leuven, Belgium 10 Institute of Ecology and Earth Sciences, University of Tartu, Tartu, Estonia 11 Department of Biology, Research Group Plant and Vegetation Ecology, University of Antwerp, Campus Drie Eiken, Wilrijk, Belgium 12 Present address: Department of Medical Biochemistry and Biophysics, Umea ˚ University, Umea ˚ , Sweden 13 Department of Biology and Department of Plant and Soil Sciences, University of Kentucky, Lexington, KY, USA INTRODUCTION The sexual reproductive phase from gamete development to seedling emergence is one of the most critical stages in the lifecycle of plants (Harper 1977). The success of an individual in passing through this phase is greatly dependent on the maternal environment (Roach & Wulff 1987; Donohue 2009). Effects of the maternal environment on seed set, mat- uration, predation, germination and seedling survival are all well documented (e.g. Meunier et al. 2007; De Frenne et al. 2009, 2010b). With respect to seed traits, however, seed nutrient concentration is often overlooked, although for mul- tiple reasons it deserves as much attention as, for example, seed size (Kitajima 2002): the seed nutrient concentration has important implications for several processes within the sexual reproductive phase, including interactions with nitrogen-lim- ited seed predators (Mattson 1980; Jolivet & Bernasconi 2006; De Menezes et al. 2010), efficiency of seed dispersal (Boulay et al. 2006; Delatte & Chabrerie 2008) and seedling performance (Parrish & Bazzaz 1985; Stock et al. 1990; Naegle et al. 2005). In addition, global warming is likely to affect plant reproduction in many ways (Hedhly et al. 2009), but current knowledge about the effects of global warming on the number, mass and nutrient concentration of seeds in natural settings is still very limited (Hovenden et al. 2008; De Frenne et al. 2009, 2010b; Verheyen et al. 2009). One approach to assess the impact of the maternal environment on plant performance in general and on seed Keywords Collection date; latitude; nutrient stoichiometry; seed nitrogen; seed predation; seed provisioning; sexual reproduction; wood anemone. Correspondence P. De Frenne, Laboratory of Forestry, Ghent University, Geraardsbergsesteenweg 267, BE-9090 Melle-Gontrode, Belgium. E-mail: Pieter.DeFrenne@UGent.be Editor M.V. Kleunen Received: 1 July 2010; Accepted: 7 Septem- ber 2010 doi:10.1111/j.1438-8677.2010.00404.x ABSTRACT The nutrient concentration in seeds determines many aspects of potential success of the sexual reproductive phase of plants, including the seed predation probability, efficiency of seed dispersal and seedling performance. Despite considerable research interest in latitudinal gradients of foliar nutrients, a similar gradient for seeds remains unexplored. We investigated a potential latitudinal gradient in seed nutrient concentrations within the widespread European understorey forest herb Anemone nemorosa L. We sampled seeds of A. nemorosa in 15 populations along a 1900-km long latitudinal gradient at three to seven seed collection dates post- anthesis and investigated the relative effects of growing degree-hours >5 °C, soil char- acteristics and latitude on seed nutrient concentrations. Seed nitrogen, nitrogen: phosphorus ratio and calcium concentration decreased towards northern latitudes, while carbon:nitrogen ratios increased. When taking differences in growing degree- hours and measured soil characteristics into account and only considering the most mature seeds, the latitudinal decline remained particularly significant for seed nitro- gen concentration. We argue that the decline in seed nitrogen concentration can be attributed to northward decreasing seed provisioning due to lower soil nitrogen avai- lability or greater investment in clonal reproduction. This pattern may have large implications for the reproductive performance of this forest herb as the degree of seed provisioning ultimately co-determines seedling survival and reproductive success. Plant Biology ISSN 1435-8603 Plant Biology ª 2010 German Botanical Society and The Royal Botanical Society of the Netherlands 1