Evidence of Morphological Divergence and Reproductive Isolation in a Narrow Elevation Gradient

Abstract

Elevation gradients generate different environmental conditions. This environmental differentiation can influence morphological adaptation, habitat isolation, reproductive isolation, and pollinator limitation in plants. Habitat differentiation and isolation often act first on phenotypic traits and then on genotype variation, causing genetic divergences between populations. We evaluated the effect of elevation on morphological traits, reproductive isolation, and pollinator limitation in Croton aff. wagneri in dry shrublands of inter-Andean valleys in Ecuador. We measured morphological traits of Croton at three elevations and carried out experimental pollination crosses between and within each population at different elevations to assess the degree of reproductive isolation and pollinator limitation. Morphological traits such as leaf thickness, plant volume, inflorescence length and inflorescence number were dissimilar between plants in different elevations. There was evidence of incipient reproductive isolation between plants in populations at the highest and the lowest studied elevations. Pollination experiments within each elevation showed a limitation of pollinators in Croton in the highest elevation. Intrinsic barriers to pollen dispersal and ecological divergence can produce reproductive incompatibilities between individuals with different traits along the Croton elevation gradient.

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Availability of data and material

If this paper is accepted our data will be deposited in Dryad Digital Repository. However, they will be available for Evolutionary Biology and for peer reviewers if required.

Code availability

Code will be sent to the reviewers when they require it.

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Acknowledgements

We thank to Inés Vélez, Ismael Vélez and many Universidad Técnica Particular de Loja students for their help in the field. Thanks to Monterrey Azucarera Lojana C.A. and the Jaramillo family for access to their beautiful property. We also thank Chris Brinegar and Javier Morente-López for valuable comments on this document.

Funding

This work was supported by the Secretaría de Educación Superior, Ciencia, Tecnología e Innovación, Ecuador PIC-13-ETAPA-005 to DPVM, and The Winter Park Garden Club through a University of Central Florida endowment to PFQA.

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DPVM and PFQA conceived the study and design. DPVM, KTA and PFQA collected the samples and measurements. DPVM carried out the pollinations. PFQA conducted the analyses. DPVM and PFQA wrote the draft of the manuscript. All authors edited and reviewed the final version of the manuscript.

Corresponding author

Correspondence to Diego P. Vélez-Mora.

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The authors have no conflict of interest to declare.

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Vélez-Mora, D.P., Trigueros-Alatorre, K. & Quintana-Ascencio, P.F. Evidence of Morphological Divergence and Reproductive Isolation in a Narrow Elevation Gradient. Evol Biol (2021). https://doi.org/10.1007/s11692-021-09541-1

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Keywords

  • Croton
  • Elevation gradient
  • Inter-andean shrubland
  • Morphological divergence
  • Pollen limitation
  • Reproductive isolation