Hybrids of Thymus L. (Lamiaceae) genus in flora of the western regions of Ukraine: taxonomic composition and distribution

Hybridization is a typical phenomenon in the taxonomically critical genus of thyme – Thymus L. (Lamiaceae Martinov). However, little attention has been drawn until now to the question of correct identification of thyme hybrid forms as a way to solve taxonomic problems in this plant group. The paper presents the results of critical taxonomic study of Thymus hybrids in the flora of western regions of Ukraine and the ascertainment of their distribution in the studied area. The hybrid diversity was found to be represented by nine interspecific hybrids. Among them, the hybrids T. alternans Klokov × T. pulegioides L. and T. alpestris Tausch ex A. Kern. × T. pulcherrimus Schur subsp. pulcherrimus are new for science. An annotated list of Thymus hybrids in flora of the western regions of Ukraine is presented, including the hybrid formula, main synonyms, basic literature, distribution in the western regions of Ukraine, map of distribution, list of the examined herbarium specimens, and critical comments. If a hybrid has been validly described as a nothospecies, then its Latin and Ukrainian binary names, nomenclature reference, and information about the nomenclature type and its deposition place are additionally provided. An original key identification of Thymus hybrids is proposed