Geographical Distribution of Diploid and Tetraploid Cytotypes of Thymus sect. Mastichina (Lamiaceae) in the Iberian Peninsula, Genome Size and Evolutionary Implications |
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Authors: | Verónica Girón Teresa Garnatje Joan Vallès Ernesto Pérez-Collazos Pilar Catalán Benito Valdés |
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Institution: | 1. Departamento de Biolog??a Vegetal y Ecolog??a, Universidad de Sevilla, Apdo. 1095, 41080, Sevilla, Spain 2. Institut Bot??nic de Barcelona (IBB-CSIC-ICUB), Passeig del Migdia s.n., Parc de Montju?c, 08038, Barcelona, Catalonia, Spain 3. Laboratori de Bot??nica, Facultat de Farm??cia, Universitat de Barcelona, Av. Joan XXIII, s.n., 08028, Barcelona, Catalonia, Spain 4. Departamento de Agricultura y Econom??a Agraria. Escuela Polit??cnica Superior de Huesca, Universidad de Zaragoza, Carretera de Cuarte km 1, 22071, Huesca, Spain
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Abstract: | The occurrence of diploid and tetraploid cytotypes in Thymus section Mastichina (Lamiaceae) was investigated by chromosome counting and flow cytometric measurements of DNA content. To cover the entire native distribution of the section across the Iberian Peninsula, plant material was sampled from 29 populations, representing all three taxa (Thymus albicans, T. mastichina subsp. mastichina and T. mastichina subsp. donyanae). We provide first estimates of genome size for taxa of this section. Analyses revealed the existence of new cytotypes in T. mastichina subsp. mastichina (2n?=?2x?=?28, 30) and confirmed the existence of previous ones (2n?=?4x?=?56, 58, 60). We also confirmed the presence of exclusively diploid cytotypes (2n?=?2x?=?30) in the southwestern Iberian endemics T. albicans and T. mastichina subsp. donyanae. We conclude that the southwestern Iberian Peninsula acted as a Pleistocene glacial refugium that may have permitted speciation processes within this section. Several hypotheses concerning these processes and the origin and distribution of the studied taxa are discussed. |
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