Plant biol (Stuttg) 2007; 9(6): 736-744
DOI: 10.1055/s-2007-965249
Research Paper

Georg Thieme Verlag Stuttgart KG · New York

Variation in Sexual Expression in the Monoecious Shrub Buxus balearica at Different Scales

A. Lázaro1 , 2 , M. Méndez3 , 4
  • 1Institut Mediterrani d'Estudis Avançats (C.S.I.C.-U.I.B.), c/Miquel Marqués 21, 07190 Esporles, Mallorca, Spain
  • 2Present address: Department of Ecology and Natural Resource Management, Norwegian University of Life Sciences, P.O. Box 5003, 1432 Ås, Norway
  • 3Botaniska Institutionen, Stockholm Universitet, 106 91 Stockholm, Sweden
  • 4Present address: Área de Biodiversidad y Conservación, Universidad Rey Juan Carlos, c/Tulipán s/n., 28933 Móstoles, Madrid, Spain
Further Information

Publication History

Received: November 10, 2006

Accepted: March 20, 2007

Publication Date:
12 June 2007 (eFirst)

Abstract

Monoecy allows high plasticity in gender expression because the production of separate female and male flowers increases the ability to respond to specific environmental circumstances. We studied variation in sexual expression and its correlates in the monoecious shrub Buxus balearica, for two years, in six populations in the Balearic Islands and four in the Iberian Peninsula. Phenotypic gender varied among populations; while island populations showed slight variations around an average gender, mainland populations showed a broad range of variation in gender among individuals, always biased towards increasing maleness compared with the other populations. Within populations, gender was not related to plant size. Between-year changes were slight and mainly consisted of an increase in relative maleness in the mast year. Reproduction did not affect gender in the next year, as assessed by either observational or experimental methods. Most variation in gender expression occurred among individuals within populations (83.6 %), followed by variation among populations (13.6 %) and years (2.8 %). Our results suggest that male-biased gender at population and plant levels was related to stressful conditions and resource limitation, because: (1) maleness was higher in mainland populations, where summer drought was stronger; (2) maleness increased with elevation; (3) fruit set was positively correlated with femaleness; (4) the percentage of male inflorescences increased over the flowering period; and (5) male inflorescences were preferentially in lower parts of the branch nodes. Higher maleness in mast years, however, could be related to increased male success under synchronic flowering.