Perspectives in Plant Ecology, Evolution and Systematics 15 (2013) 12–19 Contents lists available at SciVerse ScienceDirect Perspectives in Plant Ecology, Evolution and Systematics jo ur nal homep ag e: www.elsevier.com/locate/ppees Research article Assessing the influence of environmental gradients on seed mass variation in mountain grasslands using a spatial phylogenetic filtering approach Matteo Dainese ∗ , Tommaso Sitzia Department of Land, Environment, Agriculture and Forestry, University of Padova, Viale dell’Università 16, I-35020 Legnaro, Padova, Italy a r t i c l e i n f o Article history: Received 26 April 2012 Received in revised form 30 October 2012 Accepted 30 October 2012 Keywords: Elevational gradient Phylogenetic autocorrelation Soil pH Soil fertility Spatial autocorrelation Temperature a b s t r a c t Several studies have demonstrated that seed mass is related to different environmental factors. However, they have taken no account of the joint effects of spatial and phylogenetic information. We analysed the distribution pattern of seed mass along an elevational gradient (1040–2380 m a.s.l.) at the community level in grasslands of the southern Alps. First, we tested the influence of environmental filters (climate and soil properties) in determining community-weighted seed mass variation in mountain grasslands. Second, we verified the relative roles of environmental filters in determining seed mass variation after accounting for spatial and phylogenetic autocorrelation with an eigenvector filtering approach. Temper- ature, soil fertility, and soil pH were the most important predictors for explaining seed mass variation; specifically, warmer, low fertility, and alkaline grasslands showed a greater seed mass. Inclusion of spatio- phylogenetic filters in the model increased its fit and the variance explained and reduced autocorrelation significantly but had substantial effects on the parameter estimates, with temperature and soil pH becom- ing insignificant. This effect may be ascribable to spatially structured phylogenetic patterns and could likely result from the common evolutionary histories shared by many species at sites with similar envi- ronmental conditions. Therefore, the observed patterns between community-weighted seed mass and both temperature and soil pH are not independent of phylogeny, but they are explained by the shared history within genera and families. Nevertheless, soil fertility remained the most important predictor for explaining seed mass variation. The results of this work contribute to better understanding the combined effects of environment and evolutionary factors for determining seed mass distributions in the spatial context of mountain grasslands. The observed relationships with climate and soil properties are partic- ularly interesting because they are potentially relevant when modelling plant trait composition under changes in land use and climate. © 2013 Elsevier GmbH. All rights reserved. Introduction The factors that regulate how species are distributed in com- munities involve a complex mixture of ecological, evolutionary, and biogeographical processes (Ricklefs, 2007; Leibold et al., 2010; Webb et al., 2010). Characterisation of organisms on the basis of their biological attributes, such as physiological, morphological, and life history traits, has recently emerged as a promising way to study the processes responsible for variations in species compo- sition and ecosystem functioning (e.g., de Bello et al., 2005; Ackerly and Cornwell, 2007; Kraft et al., 2007; Pakeman et al., 2009; Webb et al., 2010). In the context of vegetation dynamics, traits related to dis- persal and establishment are especially important, and seed mass ∗ Corresponding author. Tel.: +39 0498272674; fax: +39 0498272686. E-mail address: matteo.dainese@unipd.it (M. Dainese). is widely recognised as a key trait controlling plant population dynamics and community structure (Rees, 1993, 1995; Guo et al., 2000; Leishman, 2001). Seed mass is connected to a number of other life history traits, such as growth form (Moles et al., 2005, 2007), plant size (Moles and Westoby, 2004), and dispersal type (Moles et al., 2007), and persistence in the soil (Thompson et al., 1993). Several studies have demonstrated that seed mass is related to different environmental factors, including climate (i.e., seed mass increases with temperature; Murray et al., 2004; Pakeman et al., 2008), elevational gradients (i.e., seed mass increases with eleva- tion; Baker, 1972; Pluess et al., 2005), latitudinal variation (i.e., more large-seeded species at the equator than towards the poles; Murray et al., 2004; Moles et al., 2007), soil moisture (i.e., larger seeds are more common in drier conditions; Baker, 1972; Wright and Westoby, 1999; Murray et al., 2004; Pakeman et al., 2008), soil fertility (i.e., higher seed mass is more common in nutrient- poor environmental conditions; Kuhner and Kleyer, 2008), and soil 1433-8319/$ – see front matter © 2013 Elsevier GmbH. All rights reserved. http://dx.doi.org/10.1016/j.ppees.2012.10.005