Disentangling the role of herkogamy, dichogamy and pollinators in plant reproductive assurance

ABSTRACT

Background: Autonomous selfing can be favoured by reduced floral herkogamy, dichogamy and pollinator visitation. Autonomous selfing diminishes as pollinator abundance increases; however, the ways pollinators contribute to such result have not been tested. Pollinators can reduce the occurrence of autonomous selfing by two not mutually exclusive mechanisms: successful pollen deposition on stigmas and pollen removal from anthers.

Aims: We tested the role of herkogamy and protandry on autonomous selfing and the role of pollinators to reduce it via pollen removal.

Methods: We studied Lepechinia floribunda (Lamiaceae) in two natural populations in the Chaco Serrano forest, Argentina. Pollination treatments were conducted to test if floral herkogamy and pollen removal by one pollinator visitation decreased seed set by autonomous selfing.

Results: Seed set in pollinator exclusion and emasculation treatments were higher in flowers with lack of herkogamy and selfing increased seed set only in these flowers. Pollen removal during the male phase decreased by 72% the probability of autonomous self-pollination.

Conclusions: Flowers with lack of herkogamy are reproductively more advantageous than flowers with approach herkogamy independently of pollinator abundance. We demonstrated for the first time that only one pollinator visitation during the male phase can strongly decrease autonomous selfing by pollen removal.

KEYWORDS:

• Autonomous self-pollination
• autonomous selfing rate
• dichogamy
• herkogamy
• Lepechinia
• protandry
• reproductive assurance

Acknowledgements

We appreciate the valuable comments of the editor X. Picó and two anonymous reviewers who helped to improve the manuscript. We are grateful to the authorities of the natural reserves La Quebrada and Los Manantiales for allowing us to working there and J. Camina and E. Glinos for the photographs and M. Gritti for processing them. We also appreciate the meticulous review of the English style made by the editor in chief L. Nagy, an anonymous reviewer and Beatriz Aguilar, professor of the English Department of the Agronomic Faculty, National University of Córdoba.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by Consejo Nacional de Investigaciones Científicas y Técnicas [CONICET, PIP 2015–0371], and L.A was supported by the Programa de Estancias de Investigación (DGAPA), Universidad Nacional Autónoma de México, at the Laboratorio Nacional de Análisis y Síntesis Ecológica (LANASE).

Notes on contributors

Joanna Soledad Roldán

Joanna Soledad Roldán is a fellowship holder from CONICET (Argentina); her research interests include plant-pollinator interaction networks and its consequences in plant reproduction.

Lorena Ashworth

Lorena Ashworth is a researcher from CONICET (Argentina); her current research interests are linked to ecosystem services mediated by ecological interactions (pollination, herbivory and mycorrhiza).