Variation in genome size in a particular taxonomic group can reflect different evolutionary processes including polyploidy, hybridization and natural selection but also neutral evolution. Using flow cytometry, karyology, ITS sequencing and field surveys, the causes of variation in genome size in the ecologically and morphologically diverse high-Andean genus Lasiocephalus (Asteraceae, Senecioneae) were examined. There was a 1.64-fold variation in holoploid genome size (C-values) among 189 samples belonging to 20 taxa. The most distinct was a group of plants with large genomes corresponding to DNA triploids. Disregarding the DNA triploids, the remaining samples exhibited a pronounced (up to 1.32-fold) and rather continuous variation. Plants with the smallest genomes most likely represent intergeneric hybrids with the closely related and sympatric Culcitium nivale, which has a smaller genome than Lasiocephalus. The variation in genome size in samples of diploid Lasiocephalus was strongly correlated with several environmental and life history traits (altitude, habitat and growth form). However, all these factors, as well as genome size itself, were correlated with phylogeny (main split into the so-called ‘forest’ and ‘páramo’ clades), which most probably represents the true cause of the differentiation in intrageneric genome size. In contrast, relationships between genome size and phylogeny were not apparent at lower divergence levels. Instead, here we suggest that ecological conditions have played a role in driving shifts in genome size between closely related species inhabiting different environments. Collectively, this study demonstrates that various evolutionary forces and processes have shaped the variation in genome size and indicates that there is a need for multi-approach analyses when searching for the causes and consequences of changes in genome size.
In the present study hybridization between the decaploid Cardamine enneaphyllos and hexaploid C. glanduligera (both previously assigned to Dentaria) was examined. The study area was located in the West Carpathians in Slovakia, where the distribution ranges of the putative parental species overlap, and they occur sympatrically. The putative hybrid C. ×paxiana was studied in many localities in terms of its morphological variation, pollen fertility and PCR-RFLP patterns. Prior to analyses hybrid individuals were tentatively determined based on three morphological characters reported as diagnostic: flower colour, presence of glands on leaves and length of rhizome internodes. Such tentative hybrid identification was confirmed by strongly decreased pollen fertility and an additive restriction pattern in the nuclear ITS region. The possible sources of the substantial morphological variation of hybrids, revealed by morphometric analyses, are discussed. Based on the results of the PCR-RFLP analysis of cpDNA, bidirectional hybridization occurred, although C. enneaphyllos was usually the maternal parent. Geographic distribution and sterility of hybrid individuals suggest that they are repeatedly generated from crosses between the parental species, and represent F1 or early generation hybrids maintained by vegetative reproduction.
Gymnadenia densiflora was recently either misinterpreted or not accepted as a distinct taxon by several authors. To resolve its taxonomic position and differentiation from the related G. conopsea, a detailed study of the morphology, chromosome numbers and distribution of these two taxa in the Czech Republic, Slovakia and neighbouring areas was carried out. Chromosome counts showed an invariable diploid chromosome number (2n = 40) for G. densiflora, while G. conopsea is diploid, tetraploid and rarely also pentaploid (2n = 40, 80, 100). Results of morphometric analyses (principal component analysis, cluster analysis, classificatory and canonical discriminant analysis) confirmed a good morphological separation between G. densiflora and G. conopsea. Characters such as the width of the second lowermost leaf, height of the plant, number of flowers in the inflorescence, number of leaves, and the ratio of height of the plant and distance from the stem base to the base of the uppermost sheathed leaf contributed most to this separation. Our study supports the recognition of G. densiflora as a distinct species.
The phylogeographical structure of the temperate shrub Rosa pendulina at 45 locations in Europe was studied using sequencing of a non-coding cpDNA region (trnL-trnF). Our study revealed a clear geographic structure of cpDNA haplotypes. Three main haplotypes were geographically widespread, but showed little overlap in their distributions, suggesting that postglacial expansion occurred from at least two distinct glacial refugia, probably located (1) at the edge of the Alps, N Apennines or Dinaric Alps, and (2) in the Balkan Peninsula or S Carpathians. All populations at locations in the Czech Republic and surrounding regions are of Carpathian origin. This finding disproved an Alpine origin of R. pendulina populations in the Šumava Mts (Czech Republic). A contact zone between Carpathian and Alpine migration routes of R. pendulina is probably located in the Danube valley.
The phylogeographic pattern of the temperate shrub Lonicera nigra (Caprifoliaceae) in Europe was inferred from molecular and fossil data. Population samples and pollen data from most of the contemporary natural distribution were analysed. While chloroplast DNA sequences revealed no intraspecific variation, AFLP data show a non-random geographic pattern. Two genetically different groups, distinguished by Bayesian clustering, divided the distribution area of L. nigra into south-western and north-eastern regions with a contact zone situated approximately in the upper part of the Danube Valley. Iberian populations constitute an additional distinct genetic group. Pollen evidence supports the genetic data, indicating that L. nigra might have survived in glacial refugia located in Central Europe. Nevertheless, this evidence should be considered only as indicative and supplementary, as an unambiguous determination of the species is not possible based on the information on pollen in the literature.