Journal Article

Differences in dichogamy and herkogamy contribute to higher selfing in contrasting environments in the annual <i>Blackstonia perfoliata</i> (Gentianaceae)

Rein Brys, Bram Geens, Tom Beeckman and Hans Jacquemyn

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 111, issue 4, pages 651-661
Published in print April 2013 | ISSN: 0305-7364
Published online February 2013 | e-ISSN: 1095-8290 | DOI: http://dx.doi.org/10.1093/aob/mct031
Differences in dichogamy and herkogamy contribute to higher selfing in contrasting environments in the annual Blackstonia perfoliata (Gentianaceae)

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Background and Aims

The establishment of plant populations in novel environments may generate pronounced shifts in floral traits and plant mating systems, particularly when pollinators are scarce. In this study, floral morphology and mating system functioning are compared between recently established and older populations of the annual plant Blackstonia perfoliata that occur in different pollinator environments.

Methods

Hand-pollination and emasculation experiments were conducted to assess the extent of pollinator-mediated pollen deposition and pollen limitation, and the contribution of autonomous selfing to total seed production. Detailed measurements of key floral traits were performed to compare the flower morphology and mating system functioning between plants from both pollination environments.

Key Results

Pollinator-mediated pollen deposition was about twice as low in the recently colonized and pollinator-poor environment compared with the old and pollinator-rich sites, but total seed set was little affected by any type of pollen limitation. The contribution of autonomous selfing to total seed production was higher in the pollinator-poor sites than in the pollinator-rich sites (index of reproductive assurance = 0·56 and 0·17, respectively), and seed production was only poorly affected by selfing, whereas in the pollinator-rich populations selfing reduced total reproductive output by about 40 % compared with outcross pollination. Plants originating from pollinator-poor environments produced smaller flowers that showed significantly lower levels of dichogamy (i.e. protogyny) and herkogamy. These reductions resulted in a 2-fold higher capacity for autonomous selfing under pollinator-free conditions (index of autonomous selfing = 0·81 and 0·41 in plants originating from the pollinator-poor and pollinator-rich environment, respectively).

Conclusions

The results illustrate that plant populations colonizing novel environments can differ markedly in floral morphology and mating system functioning. Due to a temporal shift in the male phase, the breeding system of B. perfoliata shifted from delayed selfing under pollinator-rich conditions towards competing selfing in recently established populations, providing greater reproductive assurance when pollinators and/or reproductive partners are limited.

Keywords: Autogamy; competing selfing; delayed selfing; dichogamy; herkogamy; pollen limitation; pollen quality; reproductive assurance; Blackstonia perfoliata; Gentianaceae

Journal Article.  7245 words.  Illustrated.

Subjects: Plant Reproduction and Propagation

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