Simple Summary The genus Sorbus (whitebeams, rowans, and service trees) encompasses forest trees and shrubs characterised by exceptional diversity resulting from the interplay of polyploidisation, hybridization, and apomixis. The spatiotemporal processes driving Sorbus diversification remain poorly understood. This research aims to provide insights into the evolution and diversification patterns of mountain whitebeam (S. austriaca) covering most of its range in the mountains of Central and South-eastern Europe. Our molecular and morphometric data revealed pronounced cryptic diversity within the S. austriaca complex; it is composed of different lineages, that likely originated via multiple allopolyploidisations accompanied by apomixes, and these lineages exhibit different distribution patterns. Our results are particularly valuable from a biodiversity conservation perspective due to the continuing generation of novel diversity in sympatric populations of the parental taxa. Such derived diversity requires process-oriented conservation plans and measures. Abstract The interplay of polyploidisation, hybridization, and apomixis contributed to the exceptional diversity of Sorbus (Rosaceae), giving rise to a mosaic of genetic and morphological entities. The Sorbus austriaca species complex from the mountains of Central and South-eastern Europe represents an allopolyploid apomictic system of populations that originated following hybridisation between S. aria and S. aucuparia. However, the mode and frequency of such allopolyploidisations and the relationships among different, morphologically more or less similar populations that have often been described as different taxa remain largely unexplored. We used amplified fragment length polymorphism (AFLP) fingerprinting, plastid DNA sequencing, and analyses of nuclear microsatellites, along with multivariate morphometrics and ploidy data, to disentangle the relationships among populations within this intricate complex. Our results revealed a mosaic of genetic lineages—many of which have not been taxonomically recognised—that originated via multiple allopolyploidisations. The clonal structure within and among populations was then maintained via apomixis. Our results thus support previous findings that hybridisation, polyploidization, and apomixis are the main drivers of Sorbus diversification in Europe.

Cotoneaster integerrimus represents a multiploid and facultative apomictic system of widely distributed mountain populations. We used flow cytometry to determine genome size, ploidy level, and reproduction mode variation of the Balkan populations, supplemented by analysis of nuclear microsatellites in order to address: (i) geographic distribution and variation of cytotypes among the populations; (ii) variation of reproduction mode and the frequency of sexuality; (iii) pathways of endosperm formation among the sampled polyploids and their endosperm balance requirements; (iv) genotypic diversity and geographic distribution of clonal lineages of polyploids. The prevalence of apomictic tetraploid cytotype followed by sexual diploids and extremely rare triploids was demonstrated. This prevalence of tetraploids affected the populations’ structure composed from clonal genotypes with varying proportions. The co-occurrence of diploids and tetraploids generated higher cytotype, reproductive mode, and genotypic diversity, but mixed-ploidy sites were extremely rare. The endosperm imbalance facilitates the development and the occurrence of intermediate triploids in mixed-ploidy populations, but also different tetraploid lineages elsewhere with unbalanced endosperm. All these results showed that the South European populations of C. integerrimus have higher levels of cytotype and reproductive diversity compared to the Central European ones. Therefore, the South European populations can be considered as a potential reservoir of regional and global diversity for this species.

This paper presents new records and noteworthy data on the following taxa in SE Europe and adjacent regions: cyanobacteria Anagnostidinema amphibium, mycorrhizal fungus Tricholoma frondosae, stonewort Chara connivens, mosses Dicranum polysetum and Ulota intermedia, and dicots Eclipta prostrata, Paeonia daurica subsp. daurica, Ruta graveolens and Sorbus bosniaca.

This paper presents new records and noteworthy data on the following taxa in SE Europe and adjacent regions: the diatom alga Eunotia boreoalpina; the saprotrophic fungus Clitocybe truncicola; the liverwort Haplomitrium hookeri; the moss Leptodon smithii: the monocots Epipactis purpurata, Stipa tirsa, Typha laxmannii and T. shuttleworthii; and the dicots Krascheninnikovia ceratoides, Polygonum albanicum and Sorbus latifolia.