Distribution and habitat segregation on different spatial scales among diploid, tetraploid and hexaploid cytotypes of Senecio carniolicus (Asteraceae) in the Eastern Alps

The spatial distribution of cytotypes can provide valuable insights into evolutionary patterns of polyploid complexes. In a previous study the macro-scale distribution of the three main cytotypes in Senecio carniolicus (Asteraceae) within the Eastern Alps was characterized. Employing a roughly 12-fold extended sampling, the present study focuses on unravelling patterns of cytotype distribution on the meso- and microscale and on correlating those with ecological properties of the growing sites. DAPI flow cytometry of dried samples was used to determine DNA ploidy level in 5033 individuals from 100 populations spread over the entire Eastern Alpine distribution area of S. carniolicus. Descriptors of microhabitats as well as spatial data were recorded in the field, and analysed with a mixed-effects ANOVA. Extensive variation in DNA ploidy levels (2x, 3x, 4x, 5x, 6x, 7x, 8x, 9x) was detected. Of the main cytotypes, diploids and hexaploids were widespread and had strongly overlapping distributions resulting in the frequent occurrence of cytotype mixtures (half of the investigated populations), whereas tetraploids were disjunctly distributed and occurred in the south-west and the east of the species' distribution area. In spite of the frequent co-occurrence of cytotypes, only 1 % of the samples belonged to secondary cytotypes (3x, 5x, 7x, 8x, 9x). Diploids, tetraploids and hexaploids were altitudinally segregated, but with broad overlap. Similarly, highly significant differences in vegetation and rock cover as well as microhabitat exposure were found between the main cytotypes. Senecio carniolicus shows a remarkable diversity of cytotypes. The distribution of the three main cytotypes (2x, 4x, 6x) has been shaped by Pleistocene glaciations to different extents. Whereas tetraploids are nearly entirely restricted to refugia, hexaploids colonized areas that were extensively glaciated. Diploid and hexaploid individuals often co-occur in mixed populations, where they are spatially and ecologically segregated at both the meso-scale (altitudinal differentiation, exposure of the growing site) and the micro-scale (cover of vegetation and bare rock). With regard to the ecological parameters investigated, the tetraploid cytotype occupies an intermediate position. The rareness of secondary cytotypes suggests the presence of strong pre- or post-zygotic mating barriers

Thliphthisa sapphus (Rubiaceae, Rubieae), a new species from Lefkada (Ionian Islands, Greece) and its ecological position

The new species, Thliphthisa sapphus sp. nov. (Rubiaceae, Rubieae), a narrow endemic of the white cliffs of Lefkátas on the southwest coast of Lefkada (Greece) is described and illustrated and an IUCN assessment is presented. Vegetation relevés were performed at the single known locality, limestone cliffs facing the sea and revealed a new association, the Thliphthisa sapphus-Lomelosietum dallaportae. The chromosome number of Thliphthisa sapphus was determined as 2n = 4x = 44, being the single tetraploid species in the genus to date. The species also differs markedly morphologically from its morphologically closest relatives, two Greek steno-endemic oreophytes, Th. baenitzii and Th. muscosa by the following characters: densely setose mericarps and corolla, tetraploidy and by its distribution. An identification key for the Greek species of Thliphthisa is provided. Th. sapphus constitutes the westernmost outpost of a group of Greek steno-endemics, highlighting the importance of coastal habitats and their protection as refugia for poorly competitive chamaephytes

SenecioCarniolicus_2x_8regions_irreversible_model_run1

BEAST input file form irreversible discrete phylogeographic region with 8 geographic regions and default settings for the geographic model. Populations acronyms as in Table S1 (online supplementary material)

Parental ploidy strongly affects offspring fitness in heteroploid crosses among three cytotypes of autopolyploid Jacobaea carniolica (Asteraceae).

Reproductive interactions among cytotypes in their contact zones determine whether these cytotypes can co-exist and form stable contact zones or not. In autopolyploids, heteroploid cross-compatibilities might depend on parental ploidy, but tests of this hypothesis in autopolyploid systems with more than two ploidies are lacking. Here, we study Jacobaea carniolica, which comprises diploid, tetraploid, and hexaploid individuals regularly forming contact zones. Seeds obtained from in situ cross-pollinations within and among cytotypes were subjected to DNA flow cytometry and greenhouse germination experiments. Hybrid fitness and parental effects on hybrid fitness were tested with regression models comparing fitness parameters of early life stages. Irrespective of the direction of crosses, seed viability and seedling survival in diploid-polyploid crosses were substantially lower than in tetraploid-hexaploid crosses. In contrast, seedling growth traits indicated neither transgressive character expression nor any selection against hybrid offspring. Congruent with a model of genome dosage effects, these traits differed between reciprocal crosses, especially of diploids and tetraploids, where trait values resembled those of the maternal parent. The strong effect of parental ploidy on offspring fitness in heteroploid crosses may cause contact zones involving exclusively polyploid cytotypes to be less stable over longer terms than those involving diploids and polyploids

SenecioCarniolicus_2x_plus_outgroups_uncoded_plastidSequences

Alignment of plastid sequences from Senecio carniolicus and related taxa (the alignment with sequences coded for statistical parsimony analysis is available from TreeBase). Populations acronyms of S. carniolicus as in Table S1, out-group taxa information in Table S2 (online supplementary information

SenecioCarniolicus_2x_AFLPmatrix

AFLP data matrix. Populations acronyms as in Table S1 (online supplementary material

SenecioCarniolicus_2x_13regions_reversible_model_run1

BEAST input file using the reversible discrete phylogeographic model with 13 geographic regions using default settings for geographic model. Populations acronyms as in Table S1 (online supplementary material)

<i>In situ</i> cross-pollinations (left) among diploid, tetraploid and hexaploid individuals of <i>Jacobaea carniolica</i> and consecutive germination of a subset of the seed yield of heteroploid crosses (right) in the climate chamber.

1<p>maternal parent is given first; SI, selfing treatments.</p