All in an afternoon: mixed breeding system in one-day lasting flowers of Hypericum elodes L. (Hypericaceae)

Abstract

Knowledge about mixed mating systems can improve our understanding of the evolutionary dynamics of reproductive systems. Here we report a study of the floral and reproductive biology of Hypericum elodes, an Atlantic-European soft-water pools specialist which shows a floral architecture consistent with both self- and cross-pollination. Controlled pollination experiments were performed in a natural population during three consecutive years. Marked flowers were monitored until fruit production, and laboratory germination experiments were conducted with the seeds produced. Plants were self-compatible (SCI>0.75), however, compared with selfing, cross-pollination enhanced fruit-set, seed-set and seedling growth, but not seed germination. Inbreeding depression (δ) was mild in the pre-dispersal stages (δ = 0.22 for fruit set, 0.18 for seed set and 0.13 for seed mass), low for germination percentage (δ = 0.003) and mild for seedling growth (δ = 0.23). The breeding system of H. elodes promotes outcrossing and assures reproductive success by means of competitive autogamy. Our results suggest a mixed mating strategy for the studied population, characterized by mild inbreeding depression (cumulative δ = 0.57), highlighting the benefit of this reproductive mode in unpredictable habitat, as the typical shallow-water meadows where H. elodes grows.

Keywords::

• Hypericum
• inbreeding depression
• breeding system
• pollen germination
• seed germination
• self-compatibility
• wetland

Acknowledgements

This research was funded by EX60% from the University of Pisa and conducted under the auspices of the Regional Natural Park of Migliarino-San Rossore-Massaciuccoli. Financial support (RFO funds) from Alma Mater Studiorum – Università di Bologna is also gratefully acknowledged. We are grateful to Angela Giannotti, who helped with laboratory experiments and Matilde Boschetti, Sara Campigli, Mario Calbi and Gherardo Bogo for valuable assistance with fieldwork.

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