Oecologia (2007) 152:515–524 DOI 10.1007/s00442-007-0662-x 123 ECOSYSTEM ECOLOGY The interplay of pollination, costs of reproduction and plant size in maternal fertility limitation in perennial Paeonia oYcinalis Emilie Andrieu · Max Debussche · Marta Galloni · John D. Thompson Received: 11 December 2006 / Accepted: 9 January 2007 / Published online: 3 February 2007  Springer-Verlag 2007 Abstract Although several factors can limit female fertility in perennial plants, rarely have they been jointly studied in a single species over several years. In this study we experimentally manipulate seed produc- tion and simultaneously analyse the potential contribu- tion of pollen limitation, costs of reproduction and plant size to variation in seed output over a 3-year period in the perennial herb Paeonia oYcinalis, in southern France. Since this rare species is threatened by forest closure in many sites we also examine the causes of female fertility variation in relation to habitat closure (open habitat vs. woodland). P. oYcinalis has a partial self-incompatibility system and only very low ability for autonomous self pollination in the absence of pollinators. However, supplementary pollination of individual plants in three consecutive years did not sig- niWcantly increase seed production above natural lev- els. Forest closure was associated with a decline in ovule and seed production, which again was not due to pollen limitation since supplementary pollination had no signiWcant eVect on seed set in the woodland habi- tat. Comparison of the maternal fertility of plants which were previously excluded from reproduction with those which were hand pollinated to maximise seed set in two previous years produced no evidence that seed production in year three is limited by costs associated with prior reproduction. Likewise, Xowering probability was not related to prior seed production but was however positively related to plant size. The absence of any inXuence of pollen limitation or prior reproduction on seed production suggests that sub- maximal seed production in long-lived perennial herbs may be part of a size-dependent strategy that maxi- mises life-time seed production and Wtness without compromising survival. Keywords Forest closure · Pollen limitation · Rare species · Resource limitation · Self-incompatibility Introduction In many species of perennial Xowering plants, annual seed production is only a fraction of the numbers of Xowers or ovules produced by an individual in a given year (Stephenson 1981; Wiens 1984; Sutherland 1986). Several factors may contribute to this sub-maximal seed production: seed predation (Lavergne et al. 2005), an interaction between resource and pollen limitation (Bierzychudek 1981), allocation to male function (Sutherland and Delph 1984) or to prior reproduction (Obeso 2002), and genetic factors such as inbreeding depression and self-incompatibility (Charlesworth 1989). Other than predicted relations between breed- ing system and pollen limitation (Herrera et al. 2001; Rodriguez-Perrez 2005), and the mechanisms by which perennial plants may adjust their seed production to conjointly minimise pollen and resource limitation Communicated by Russell Monson. E. Andrieu (&) · M. Debussche · J. D. Thompson CNRS, UMR 5175—Centre d’Ecologie Fonctionnelle et Evolutive, 1919 Route de Mende, 34293 Montpellier Cedex 5, France e-mail: emilie.andrieu@cefe.cnrs.fr M. Galloni Dipartimento di Biologia Evoluzionistica Sperimentale, Università di Bologna, Via Irnerio 42, Bologna 40126, Italy