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Triassic limestone areas of Thuringia are well-known for their richness of hybrids between S. aria and S. torminalis (subgenus Tormaria). Those have been originally described as endemic taxa (i.e. Sorbus heilingensis, S. isenacensis). However, the former endemics have been recently synonymized with S. × decipiens (Karpatiosorbus × hybrida (Bechst.) Sennikov & Kurtto) due to diploidy and putative sexuality. Generally, crosses between diploid and sexual parents should segregate and intermediates as well as morphotypes close to the parents should be the outcome. To test for clonality versus segregation, we investigated progeny of 10 Tormaria mother trees, derived from open pollination. Three to ten seedlings of each mother tree were cultivated, and six leaf characters were measured being indicative for subgenus Aria, Tormaria and Torminalis. For genetic characterization, we used three ISSR microsatellite markers and one chloroplast marker. The progeny of nine mother trees segregated; the S. aria genome prevailed in pollen clouds. One polyploid mother tree, however, produced partly clonal progeny and proved to be polyploid and facultative apomictic. This means that in Thuringian Tormaria polyploidization occurs at low rates starting from diploid hybrids. Exact comparisons between geno- and phenotypes of the progeny proved a frequent uncoupling between genetic markers and genes responsible for leaf morphology, pointing to excessive genomic rearrangement within Tormaria mother trees. Only 1/3 of Tormaria-genotypes possessed the Tormaria-phenotype. Most of them belong to S. aria and to S. aria forma incisa, a S. aria type with slightly incise leaves. This means that plasticity of parental species may be explained by excessive introgression between S. aria and S. torminalis. [ABSTRACT FROM AUTHOR]

Most studies on Salix hybrids concerning the diversity in a hybrid complex included typical morphological characteristics of leaves, buds, twigs and flowers for comparison with genotypic traits. Our analyses are based on a set of phenotypical traits of 19 clones of the S. alba/S. fragilis-aggregate which includes characteristics as phenology, growth, and composition of secondary leaf compounds, for the first time additional to morphological traits. Three clearly distinct groups ( S. alba L., S. fragilis L., and S. × rubens Schrank) could be identified based on phenotypical traits and ITS1 and 5.8S nrDNA sequences. S. × rubens revealed additivities at variable ITS1 and 5.8S positions as well as intermediate morphology and secondary compound pattern, but was characterised by significant earlier foliation start. This property leads to a better utilization of the vegetation period and may explain the detected better growth compared to the parent species and therefore also may have contributed to the widespread occurrence of S. × rubens in Central Europe. [ABSTRACT FROM AUTHOR]

The Franconian Alb (Bavaria, Germany) is rich in endemic Sorbus taxa, considered as apomictic microspecies and derived by hybridization between Sorbus aria aggregate and Sorbus torminalis ( Sorbus latifolia aggregate). Molecular studies using the AFLP technique, neighbour joining, Bayesian clustering, principal coordinate analysis (PCo) and voucher studies were used to investigate genetic structure and origin of adult plants and cultivated offspring of three endemic S. latifolia taxa, namely Sorbus cordigastensis, Sorbus franconica and Sorbus adeana and probable parental species from the S. aria agg. and S. torminalis. The S. latifolia taxa, adults and progeny, showed low genetic variability and a more or less clonal structure, confirming an apomictic mode of reproduction. The investigated S. latifolia taxa were remarkably different among each other, confirming their status as microspecies. The AFLP data confirmed the hybrid origin of the S. latifolia taxa, they were 1.3-1.5 times more closely related to S. aria agg. than to S. torminalis. The S. aria agg. showed a complicate genetic structure and fell into four main groups, two intermediate groups besides Sorbus pannonica and Sorbus aria sensu stricto ( S. aria s.str.). Some progeny of S. pannonica was more variable than expected and clustered partly with other groups indicating gene flow within S. aria agg. Different subgroups of the S. aria aggregate may be parental for the S. latifolia taxa, contributing to the remarkable genetic distances between them. [ABSTRACT FROM AUTHOR]