Evolutionary significance of hybridization inOnosma(Boraginaceae): analyses of stabilized hemisexual odd polyploids and recent sterile hybrids

摘要: Interspecific hybridization is an important evolutionary force promoting plant speciation. In the genus Onosma, one of three main lineages presumably evolved by hybrid The assumed lineage (Heterotricha) consists two species complexes with bimodal karyotypes containing different numbers large (L) and small (S) chromosomes, tetraploid Onosma pseudoarenaria (2n = 12 L + 14S) triploid arenaria (2n = 12 L + 8S). latter represents a rare case hemisexual, asymmetrically compensating allopolyploids. Representatives other genus, Haplotricha (2n = 12 L) Asterotricha (2n = 14S), have been considered to be ancestral taxa O. pseudoarenaria O. arenaria, although this has yet investigated critically. present study, we examined genetic [amplified fragment length polymorphism (AFLP), internal transcribed spacer (ITS) , chloroplast (cp)DNA)], reproductive (pollen viability seed production) cytogenetic (chromosome counts, genome size assessment) patterns resolve hypothesized allopolyploid formations in Heterotricha group, single or polytopic origins, as well ongoing interspecific gene flow piece evidence for understanding past speciation events genus. Discordant maternally inherited cpDNA (Heterotricha accessions bearing haplotypes related asterotrichous species) nuclear ITS AFLP markers clustering haplotrichous Onosma fastigiata), karyological features, support origin stabilized lineage. Genetic variation that both geographically correlated indicates multiple origins allopolyploids or, less likely, recurring introgression from progenitor species. features also provide between O. arenaria echioides which gives rise sterile triploids 2n = 6 L + 15S. We contrast cases LLS (hemisexual lineage) LSS (recent hybrids) karyotypes, could help understand mechanisms ensuring establishment fitness odd Onosma. © 2014 Linnean Society London, Biological Journal Society, 2014, 112, 89–107.