Is there spatial variation in phenotypic selection on floral traits in a generalist plant–pollinator system?
The selective role of pollinators on the floral phenotype has been identified as the main force behind angiosperm diversification. However, in generalized plant–pollinator interactions this association may not be that evident, since pollinator assemblages vary in composition among populations, possibly influencing the direction and intensity of floral trait selection. In this study we determine whether there was spatial variation in pollinator assemblages and the selective forces they exert in ten populations of Alstroemeria ligtu var. simsii. We characterized the whole pollinator assemblage in ten populations, quantified four floral attraction traits and determined potential selection targets in each of the study populations. Our results revealed that populations differed in the composition of their pollinator assemblages, and the pollinators with the highest visitation rates also differed among populations. Using phenotypic selection analysis we detected significant differentials and selection gradients only in two of the ten populations, for corolla tube length and ratio of the nectar guide. The spatial variation in selection showed that linear selection acting upon these traits differed significantly among the studied populations. Our study indicates that selection can be detected in generalized plant–pollinator systems and brings new evidence of phenotypic selection variation in space for this endemic plant species. Future studies are needed to determine whether the selective patterns described here are consistent over time and whether they produce evolutionary change in the populations under study.
KeywordsAlstroemeria Chile Floral traits Generalist pollination Phenotypic selection
We are grateful to L. Contreras, D. Lillo, M. Zuñiga, T. Poch, V. Durán and M.J. Ramírez who assisted us in the fieldwork, and I. Sepulveda who helped in the organization of the data and the construction of Fig. 1. We thank V. Duran for providing photographs. This study was supported by the FONDECYT 11110120 Grant awarded to AG. We are grateful to the Corporación Nacional Forestal (CONAF) and the Jardín Botánico Nacional of Chile for granting permits to work on their lands. The authors declare no conflicts of interest.
- Botto-Mahan C, Ojeda-Camacho M (2000) The importance of floral damage for pollinator visitation in Alstroemeria ligtu L. Rev Chil Entomol 26:73–76Google Scholar
- Caruso CM, Scott SL, Wray JC, Walsh CA (2010) Pollinators, herbivores, and the maintenance of flower color variation: a case study with Lobelia siphilitica. Evol Ecol 31(2):285–304Google Scholar
- Darwin CR (1862) On the various contrivances by which British and foreign orchids are fertilized by insects. John Murray, LondonGoogle Scholar
- di Castri F, Hajek ER (1976) Bioclimatología de Chile. Ediciones de la Universidad Católica de Chile, Santiago, p 128Google Scholar
- Faegri K, van der Pijl L (1979) The principles of pollination ecology. Pergamon Press, OxfordGoogle Scholar
- González AV, Murúa M, Ramírez P (2014) Temporal and spatial variation of the pollinator assemblages in Alstroemeria ligtu (Alstroemeriaceae). Rev Chil Hist Nat 1:5Google Scholar
- Hammer O, Harper D, Ryan P (2001) PAST: paleontological statistics software for education and data analysis. Paleontol Electrón 4:1–9Google Scholar
- Lillo D (2014) Spatial variation in the pollen limitation of Alstroemeria ligtu var. simsii. Bs. Thesis, Universidad de Chile, Santiago, ChileGoogle Scholar
- Muñoz M, Moreira MA (2003) Alstroemerias de Chile; diversidad, distribución y conservación. Taller la Era, SantiagoGoogle Scholar
- Navas LE (1973) Flora de la cuenca de Santiago de Chile. Ediciones de la Universidad de Chile, SantiagoGoogle Scholar
- Ne’eman G, Jürgens A, Newstrom-Lloyd L, Potts SG, Dafni A (2010) A framework for comparing pollinator performance: effectiveness and efficiency. Biol Rev 85:435–451Google Scholar
- R Core Team (2019) R: a language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. https://www.R-project.org/. Accessed 23 June 2019
- Schaefer H, Schaefer V, Levey D (2004) How plant–animal interactions signal new insights in communication. TREE 19:577–584Google Scholar