Polyploidy, the major speciation mechanism in Muscari subgenus Botryanthus in the Iberian Peninsula

Abstract

Currently, three species of Muscari subg. Botryanthus are recognized in the Iberian Peninsula: two diploids (2n = 18), M. atlanticum and M. cazorlanum, and one morphologically variable species with three different ploidy levels, M. neglectum (2n = 36, 45, 54). We have made a comparative study of numerous Iberian populations to clarify the taxonomy and evolution of this group. To this end we carried out morphological and cytogenetic analyses, and phylogenetic analysis of the internal transcribed spacers of nuclear ribosomal DNA. Comparative and UPGMA analyses of the morphological characteristics show that the different ploidy levels of M. neglectum represent different species. We describe the pentaploid and hexaploid levels as two new species, M. olivetorum (2n = 45) and M. baeticum (2n = 54), each with an exclusive combination of morphological characters and a characteristic ecological behavior pattern. Phylogenetic study of ITS shows that the two new species are not autopolyploids from M. neglectum but allopolyploids. These findings are supported by the additivity of the three ITS variants found in M. olivetorum with the ITS of M. neglectum and M. baeticum, and also by morphology. Possible parents for both new species are proposed. Absence of homogenization between homeologous M. olivetorum nrDNA loci is explained by the absence of sexual reproduction and by nucleolar dominance, indicating that this is a recent species.