Gene flow and its consequences for microevolution in Taraxacum (Asteraceae)

[7] Summary Microevolution refers to evolutionary changes at or below the species level. These changes are the result of mutation, natural selection, gene flow and genetic drift. When microevolutionary processes in agamic complexes, like Taraxacum, are studied, gene flow deserves special attention. Taraxacum is very large and widespread genus with a very complicated taxonomy. It forms a polyploid series with basic chromosome number x=8, diploids (obligate sexuals) and triploids (apomicts) prevail. The presented work studies reproductive behaviour and pathways of the gene flow in Taraxacum sect. Ruderalia and compares it with Taraxacum sect. Erythrosperma. Diploid, triploid and tetraploid individuals were sampled from mixed diploid - polyploid natural populations of Taraxacum sect. Ruderalia, diploids and triploids from Taraxacum sect. Erythrosperma. Seeds resulting both from the crosses between particular ploidy levels, from isolated anthodia and from open pollinated anthodia (from cultivated and wild plants) were subjected to the flow-cytometric seed screening (FCSS) to determine ploidy levels in the progeny and to infer breeding behaviour of maternal plants. Three possible pathways of the gene flow were studied: (A) fertilization of sexuals by pollen of apomicts, (B) BIII (2n+n) hybrid formation, (C)...[7] Summary Microevolution refers to evolutionary changes at or below the species level. These changes are the result of mutation, natural selection, gene flow and genetic drift. When microevolutionary processes in agamic complexes, like Taraxacum, are studied, gene flow deserves special attention. Taraxacum is very large and widespread genus with a very complicated taxonomy. It forms a polyploid series with basic chromosome number x=8, diploids (obligate sexuals) and triploids (apomicts) prevail. The presented work studies reproductive behaviour and pathways of the gene flow in Taraxacum sect. Ruderalia and compares it with Taraxacum sect. Erythrosperma. Diploid, triploid and tetraploid individuals were sampled from mixed diploid - polyploid natural populations of Taraxacum sect. Ruderalia, diploids and triploids from Taraxacum sect. Erythrosperma. Seeds resulting both from the crosses between particular ploidy levels, from isolated anthodia and from open pollinated anthodia (from cultivated and wild plants) were subjected to the flow-cytometric seed screening (FCSS) to determine ploidy levels in the progeny and to infer breeding behaviour of maternal plants. Three possible pathways of the gene flow were studied: (A) fertilization of sexuals by pollen of apomicts, (B) BIII (2n+n) hybrid formation, (C)...Department of BotanyKatedra botanikyFaculty of SciencePřírodovědecká fakult

Petasites kablikianus (Asteraceae) in the Slovak Carpathians: distribution, chromosome number and genome size

The paper treats the distribution and ecological characteristics of the butterbur species Petasites kablikianus in the Slovak Carpathians (Central Europe). Study of herbarium specimens, review of published sources and results of field research show its wide distribution in northern and central Slovakia, mainly in wet biotopes such as gravel riverbeds and rocky banks of mountain streams. The majority of populations occur from the submontane to montane level (mainly at elevations of 600-1200 m a.s.l.) with the altitudinal maximum at ca. 1850 m a.s.l. Chromosome number analysis showed 2n = 60. The nuclear DNA content measured in leaves was 2C = 5.96 ± 0.17 pg, or 5828 Mbp. Characters used for determination are also discussed. A distribution map is attache

Gene flow and its consequences for microevolution in Taraxacum (Asteraceae)

[7] Summary Microevolution refers to evolutionary changes at or below the species level. These changes are the result of mutation, natural selection, gene flow and genetic drift. When microevolutionary processes in agamic complexes, like Taraxacum, are studied, gene flow deserves special attention. Taraxacum is very large and widespread genus with a very complicated taxonomy. It forms a polyploid series with basic chromosome number x=8, diploids (obligate sexuals) and triploids (apomicts) prevail. The presented work studies reproductive behaviour and pathways of the gene flow in Taraxacum sect. Ruderalia and compares it with Taraxacum sect. Erythrosperma. Diploid, triploid and tetraploid individuals were sampled from mixed diploid - polyploid natural populations of Taraxacum sect. Ruderalia, diploids and triploids from Taraxacum sect. Erythrosperma. Seeds resulting both from the crosses between particular ploidy levels, from isolated anthodia and from open pollinated anthodia (from cultivated and wild plants) were subjected to the flow-cytometric seed screening (FCSS) to determine ploidy levels in the progeny and to infer breeding behaviour of maternal plants. Three possible pathways of the gene flow were studied: (A) fertilization of sexuals by pollen of apomicts, (B) BIII (2n+n) hybrid formation, (C)..

Variability of Reproduction Pathways in the Central-European Populations of Hawthorns with Emphasis on Triploids

The role of apomeiosis, parthenogenesis, and pseudogamy in the asexual reproduction of some plant groups has not been fully elucidated in relation to species diversification. Quantitative analyses of seed origin may help in gaining better understanding of intercytotypic interactions. Asexual reproduction associated with polyploidy and frequent hybridization plays a crucial role in the evolutionary history of the genus Crataegus in North America. In Europe, the genus represents a taxonomically complex and very difficult species group not often studied using a modern biosystematic approach. We investigated the reproduction pathways in mixed-cytotype populations of selected taxa of Crataegus in eastern Slovakia, Central Europe. The investigated accessions were characterized by seed production data and the ploidy level of mature plants as well as the embryo and endosperm tissues of their seeds determined via flow cytometry. Diploid and polyploid hawthorns reproduce successfully; they also produce high numbers of seeds. An exception is represented by an almost sterile triploid. Diploids reproduce sexually. Polyploids shift to asexual reproduction, but pseudogamy seems to be essential for regular seed development. In rare cases, fertilization of unreduced gametes occurs, which offers opportunity for the establishment of new polyploid cytotypes between diploid sexuals and polyploid asexuals. Opposite to sexual diploids, triploids are obligate, and tetraploids almost obligate apomicts. Apomixis is considered to help stabilize individual weakly differentiated polyploid microspecies. Pseudogamy is a common feature and usually leads to unbalanced maternal to paternal contribution in the endosperm of triploid accessions. Parental contribution to endosperm gene dosage is somehow relaxed in triploids. Our Crataegus plant system resembles reproduction in the diploids and polyploids of North American hawthorns. Our data provide support for the hypothesis that polyploidization, shifts in reproduction modes, and hybridization shape the genus diversity also in Central Europe

Out of the Balkans and Anatolia to the Western Alps? Surprising phylogenetic implications for two endemic <i>Alyssum </i>(Brassicaceae) species: <i>A. cognense</i> sp. nov. and <i>A. rossetii</i>

The European Alps show a high degree of endemism associated mainly with the location of glacial refugia and environmental heterogeneity. Several Alpine endemics have evolved in the genus Alyssum. Here we study perennial Alyssum populations in the Western Alps, mainly distributed in the Aosta Valley region, which hosts high species diversity, although endemics are rare. We addressed the recently described stenoendemic A. rossetii and taxonomically uncertain populations usually attributed to A. montanum s.s. to clarify their phylogenetic position and morphological differentiation. The latter entity has been shown to be distinct from A. montanum s.s. and is described as a new species, Alyssum cognense, phylogenetically placed in the A. montanum–A. repens species complex. Both morphological and genetic patterns revealed that its closest relative occurs in the central Balkans. We present detailed ecological characteristics and morphological differentiation of A. cognense sp. nov. from its relatives and geographically closest species and speculate on its biogeographic origin. Genetic patterns (reduced diversity and nestedness) suggest long-distance dispersal from the central Balkan Peninsula. The second studied species, A. rossetii, is phylogenetically distant and belongs to the mainly Asian Alyssum section Gamosepalum lineage, which includes few representatives in southern and eastern Europe. The phylogenetically closest species of A. rossetii are Anatolian endemics, so this extreme disjunction remains puzzling. The present study illustrates the need for in-depth taxonomic and phylogenetic studies, even in well-explored Alpine regions, and also shows that the processes underlying the evolution of endemics can be complex and poorly understood.</p