Reproductive ecology in the endemic Primula apennina Widmer (Primulaceae)

Abstract

Disassortative mating in distylous self-incompatible species should result in the equilibrium of morph types in natural populations. Deviation from isoplethy may affect pollen transfer, and in isolated populations it could lead to Allee effect and genetic drift. Pollen limitation has been found to occur in several distylous species, for which mating opportunities are actually reduced to half population. In this study, we investigated the reproductive features and pollination ecology of the narrow endemic Primula apennina. We recorded equilibrium of morph frequencies in the studied population, reflecting the comparable fecundity found in the two morphs. Long-styled flowers produce more pollen grains of smaller size than short-styled ones: we hypothesize that in thrum flowers, pollen is more easily removed by the insect pollinator Macroglossum stellatarum, resulting in equal pollen amounts carried to both short styles and long styles. This lower pollen transfer efficiency from long-styled to short-styled flowers is also reflected in legitimate pollen–ovule ratio values. Despite results show no evidence of imminent threats to population persistence at study site, the strict dependence on one or very few pollinator species, and ecological traits, may increase extinction risks in the long-term period.

Keywords:

• Distyly
• endemism
• female fitness
• pollen limitation
• pollination

Acknowledgements

Special thanks to Adriano Zanetti (Museo Civico di Storia Naturale di Verona) and Mario Marini for insect identification, to Sandro Cavicchi and Vincenzo Trotta for their help with statistical analysis and to Martina Rossi and Elena Bortoluzzi for valuable assistance with fieldwork. The authors are also grateful to the staff of the natural park “Parco Nazionale dell'Appennino Tosco-Emiliano”, and in particular Willy Reggioni, for permitting field experiments and sample collection.

Notes

Voucher specimens are conserved at the Department of Biology, University of Bologna.