Molecular confirmation of the hybrid origin of the critically endangered western Mediterranean endemic Sonchus pustulatus (Asteraceae: Sonchinae)

  • Seung-Chul Kim
  • Jose A. Mejías
  • Pesach Lubinsky
Regular Paper

Abstract

The critically endangered composite Sonchus pustulatus Willk. despite being known from fewer than ten locations in southern Spain and northern Africa, has never been characterized in robust phylogenetic context. Here, we report molecular evidence that strongly supports a hybrid origin for S. pustulatus. Although parentage cannot be identified with certainty, analysis of DNA sequence variation from the internal transcribed spacer (ITS) region of nuclear ribosomal DNA (nrDNA) supports a phylogenetic placement of S. pustulatus close to other species in the poorly known section Pustulati, whereas examination of chloroplast DNA (cpDNA) places S. pustulatus most closely with species from the sections Sonchus and Asperi. This is one of several instances of topological non-concordance reported for the genus Sonchus. Monophyly of S. pustulatus in both gene genealogies supports the null hypothesis of a single origin, and the relatively large amount of nucleotide substitutions is indicative of an origin in the range of millions of years. A hypothesis of a northern African origin of S. pustulatus followed by dispersal to the Iberian Peninsula during the Messinian salinity crisis/later Quaternary glaciations is proposed on the basis of biogeographic patterns and calibrated estimations of molecular evolution.

Keywords

Critically endangered species Internal transcribed spacer (ITS) matK gene Reticulate evolution Sonchus pustulatus 

Notes

Acknowledgments

This project was supported, in part, by an Academic Senate Grant, Regents’ Faculty Fellowship, and Agricultural Experiment Station funds from the University of California at Riverside, to S.-C. Kim. We are also grateful for financial support by the Spanish Ministerio de Educación y Ciencia (grant CGL 2006-00817) and Junta de Andalucía (Group RNM-210). Suggestions from two anonymous reviewers and the editor greatly improved the earlier version of the manuscript. We thank Li Yao for cloning S. pustulatus. Special thanks are due to Stephen Jury for information of the Sonchus species in Morocco.

Supplementary material

10265_2008_166_MOESM1_ESM.pdf (131 kb)
Figure S1. Geographic locations of known (solid) and reported (gray) populations of Sonchus subgenus Sonchus section Pustulati taxa. SquaresS. pustulatus, circlesS. fragilis, trianglesS. masguindalii, and starsS. briquetianus. Populations in gray have not been confirmed during the past 15 years. X indicate the peaks of mountains, followed by altitudes in meters. (PDF 131 kb)
10265_2008_166_MOESM2_ESM.doc (49 kb)
Appendix S1. Additional samples of species in section Pustulati used in this study, including the locality, voucher and herbarium numbers, and GenBank accession numbers. SEV Herbarium Universidad de Sevilla. RNG Herbarium of the University of Reading. Accession numbers with asterisks were reported previously in Kim et al. (2007) (DOC 48 kb)

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Copyright information

© The Botanical Society of Japan and Springer 2008

Authors and Affiliations

  • Seung-Chul Kim
    • 1
  • Jose A. Mejías
    • 2
  • Pesach Lubinsky
    • 1
  1. 1.Department of Botany and Plant SciencesUniversity of CaliforniaRiversideUSA
  2. 2.Departmento de Biología Vegetal y EcologíaUniversidad de SevillaSevillaSpain

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