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Abstract
Background: Intraspecific variations in floral traits of species over its geographic range can be associated with differences in pollinator assemblages and/or with environmental conditions.
Aims: We evaluated the area of elaiophores in different populations of Stigmaphyllon bonariense (n = 9) and S. jatrophifolium (n = 6), and we hypothesised a marked reduction in their size towards their southern limits of distribution, associated with different oil-collecting bee assemblages.
Methods: Area of elaiophores was calculated and we carried out linear correlations with floral size, pollinators, visitation rate and pollinator size along the latitudinal gradient of the plants’ distributions. Moreover, we examined the relative size relationships using allometric analyses, to verify this reduction.
Results: Floral elaiophore area decreased with latitude. However, for S. bonariense we observed an allometric reduction in elaiophore area with respect to floral size, while for S. jatrophifolium an isometric reduction was found. In both species, pollinator richness and visitation rate did not diminish with latitude, but pollinator size for S. bonariense varied.
Conclusions: Our results show a reduction in the size of elaiophores in both species along their distribution range, with dissimilar tendencies, suggesting that these species may have different selection pressures that cause variation of their phenotypic traits.
Acknowledgements
We thank H.J. Marrero and L. Álvarez for their help with fieldwork, N. Gomiz for her work in the laboratory and for the , A. Roig Alsina and L. Álvarez (Meliponini) for collaboration in the determination of bees, A. Torretta, R. Saurral and M. Zietsman for helping with the English revision and R. Saurral for providing the meteorological information. To the Administración de Parque Nacionales (Regional NEA) Ministerio de Ecología y Recursos Naturales Renovables, province of Misiones, Dirección de Áreas Naturales Protegidas, Organismo Provincial para el Desarrollo Sostenible, province of Buenos Aires, for permission to conduct part of this study in protected areas. The manuscript benefited from critical reading by M. Mendez, L. Nagy and one anonymous reviewer.
Disclosure statement
No potential conflict of interest was reported by the authors.
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Notes on contributors
Juan P. Torretta
Juan P. Torretta is an adjunct research scientist. His research focuses on flower–pollinator relationships with emphasis on ecology and conservation of wild native bees.
Sandra S. Aliscioni
Sandra S. Alisiconi is an independent research scientist. She is interested in leaf and flower anatomy from taxonomical, phylogenetic and functional approaches.
Adelia González-Arzac
Adelia González-Arzac is a postdoctoral student. She is interested in soil ecology, particularly in the role of soil fauna on carbon recycling.
Adan A. Avalos
Adan A. Avalos is a Ph.D. student, working on the reproductive biology, embryology and floral anatomy of Malpighiaceae.