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.
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.