Evidence of hybridization between Galatella villosa and G. linosyris, and a taxonomic reappraisal of the hybrid G. ×subvillosa

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At the westernmost distribution of the steppe herbaceous plant, Galatella villosa, in Hungary, Serbia and Ukraine, we recently observed intermediate specimens between this species and its close relative, G. linosyris. We were able to demonstrate the hybrid origin of these individuals by sequencing the biparentally inherited nuclear ribosomal internal transcribed spacer (nrITS) region and checking additive polymorphism in the hybrids. In addition, examination of the maternally inherited plastid regions (trnH-psbA and trnL-trnF intergenic spacers) revealed that G. villosa is likely to be the maternal parent in the Hungarian and Ukrainian populations and G. linosyris in the Serbian population. The intermediate forms produced only sterile seeds. The alleged hybrid between the above two species has already been described as G. ×subvillosa based on a very brief diagnosis. Still, the analysis of the morphological characters using linear discriminant analyses clearly separated the holotype of G. ×subvillosa from individuals of G. linosyris × G. villosa. The latter appeared to be morphologically intermediate between populations of G. villosa and G. linosyris. Contrary to the originally stated hybrid origin of the type plants of G. ×subvillosa, morphological evidence indicates the involvement of G. divaricata not G. linosyris. The hybrid G. linosyris × G. villosa is thus described here, as a new nothospecies G. ×feketegaborii. This study highlights the power of easily available molecular phylogenetic tools for demonstrating the hybrid origin of plants and illustrates how additive polymorphism can be distinguished from other types of intraindividual polymorphism in nuclear DNA sequences.