Plant Systematics and Evolution

, Volume 201, Issue 1–4, pp 131–138 | Cite as

The consequences of specialization for pollination in a rare South African shrub,Ixianthes retzioides (Scrophulariaceae)

  • Kim E. Steiner
  • V. B. Whitehead
Article

Abstract

Ixianthes retzioides is a rare South African shrub with large yellow oil-secreting flowers. Populations studied previously revealed low levels of reproductive success and the absence of a specialized oil-collecting pollinator. We report the discovery of a population in which the predicted specialist pollinator,Rediviva gigas, is present. The presence of this oil-collecting bee resulted in a mean fruit set per plant of 97.2 ± 8.3% (N = 9) and a mean seed set of 331.6 ± 162.6 (N = 52). This represents a 7.4-fold increase in fruit set and a 7.8-fold increase in seed set over a previously studied population lacking the specialist pollinator. The contrast between populations with and without the specialist pollinator dramatically illustrates the potential benefits and costs of specialization for pollination, respectively.

Key words

Scrophulariaceae Ixianthes Melittidae Rediviva Floral oil oil-collecting bees specialization for pollination reproductive success 

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Copyright information

© Springer-Verlag 1996

Authors and Affiliations

  • Kim E. Steiner
    • 1
  • V. B. Whitehead
    • 2
  1. 1.Compton HerbariumNational Botanical InstituteClaremontRepublic of South Africa
  2. 2.South African MuseumCape TownRepublic of South Africa

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