Abstract
Pollinator species are widely accepted as an important factor in plant reproductive isolation. Although mostly investigated in plants visited by different groups of pollinators (e.g., hummingbirds vs bees), few studies have examined the role of pollinators belonging to the same taxonomic group (e.g., only bees) on plant reproductive isolation. In this study, we investigate this question by evaluating pre- and post-zygotic mechanisms putatively involved in the reproductive isolation of two oil-rewarding sympatric Calceolaria species (i.e., Calceolaria filicaulis and C. arachnoidea) in an Andean ecosystem of Chile. We estimated reproductive isolation values using a combination of field (pollinator visitation rates) and experimental (intra and interspecific manual cross-pollination and seed germination of parents and hybrids) evidence. The two Calceolaria species were preferentially visited by different oil-collecting bee species. Results from hand cross-pollination experiments indicate that intraspecific crossings produced significantly more seeds than interspecific ones. Notwithstanding, seed germination essays did not reveal differences between parental and hybrids. Taken together, these results suggest that pollinator species are responsible for most of the reproductive isolation in the two Calceolaria species studied here. This study is the first assessment of pollinator-mediated reproductive isolation in Calceolaria species and the first to document reproductive barriers in oil-rewarding plants.
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Acknowledgments
The authors thank Jannina Cisterna, Carmen Gloria Ossa, Fabiola Orrego and Isabel Mujica for help with greenhouse experiments, Daniel Caetano and Catalina González for help in data analysis, Fernanda Pérez and Pontificia Universidad Católica de Chile for providing logistic support, and Corporación Nacional Forestal (CONAF) for authorization to work in the National Reserve. This work was supported by Beca de Apoyo a la Realización de la Tesis Doctoral CONICYT [24110094], FONDECYT [PD3150267], FONDECYT [11110120], and FONDECYT [1150112]. AE was supported by the Swiss National Science Foundation (Grant PBNEP3-140192).
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Anahí Espíndola and Rodrigo Medel: share joint last authorship.
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Murúa, M., Espíndola, A., González, A. et al. Pollinators and crossability as reproductive isolation barriers in two sympatric oil-rewarding Calceolaria (Calceolariaceae) species. Evol Ecol 31, 421–434 (2017). https://doi.org/10.1007/s10682-017-9894-3
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DOI: https://doi.org/10.1007/s10682-017-9894-3