Chin J Plant Ecol ›› 2014, Vol. 38 ›› Issue (5): 460-467.DOI: 10.3724/SP.J.1258.2014.00042

Special Issue: 青藏高原植物生态学:群落生态学

• Research Articles • Previous Articles     Next Articles

Flower symmetry and flower size variability: an examination of Berg’s hypotheses in an alpine meadow

LU Ning-Na1,ZHAO Zhi-Gang2,*()   

  1. 1College of Life Sciences, Northwest Normal University, Lanzhou 730000, China
    2State Key Laboratory of Grassland and Agro-ecosystems, School of Life Sciences, Lanzhou University, Lanzhou 730000, China
  • Received:2013-11-14 Accepted:2013-12-26 Online:2014-11-14 Published:2014-05-13
  • Contact: ZHAO Zhi-Gang

Abstract:

Aims Flower symmetry is closely related to pollination system and variations in flower traits are under the selection role of pollinators. Berg predicted that flower size varies much less in bilateral species than in radial species because of the stable and/or directional selection by pollinators, and that it should also show lower variability than vegetative organs which have relatively higher sensitivity to environments. We examined these so-called Berg’s hypotheses in an alpine meadow.
Methods By measuring the traits of flowers and leaves in 50 flowering plants in an alpine meadow in the eastern Qinghai-Xizang Plateau, we compared the coefficients of variations (CV) in flower size and leaf size between 31 radial and 19 bilateral species and also performed phylogenetically independent comparisons.
Important findings Our results were not completely consistent with the Berg’s hypotheses. The CV of flower size was significantly smaller than that of leaf size in both radial and bilateral species as predicted by Berg, indicating that pollinator-mediated stabilizing selection would benefit flower stability. But the CV of flower size did not differ between the bilateral and the radial species, which is inconsistent with the Berg’s hypothesis even if we controlled confounding effects of phylogenetic relatedness. The role of pollinators in alpine ecosystem where bumble bees and flies predominate is likely more affected by local climatic environments, which leads to considerable variability in the selection of pollinators on flowers.

Key words: Berg’ hypothesis, bilateral symmetry, flower symmetry, phylogeny, radial symmetry