Anatomic, cytogenetic and molecular variations between non-serpentine and serpentine populations of endemic Lillium bosniacum

Serpentine soils are characterized by extreme ecological conditions for plant development - they are barren of plant nutrients, contain high concentrations of heavy metals, they are shallow and do not hold water well, which results in dry and exposed habitats. The stresses induced in such conditions exert evolutionary pressure for selection of traits and mutations that allow certain plants to adapt to serpentine soils. Serpentine flora in general provides an opportunity to examine adaptive evolutionary mechanisms. Lilium bosniacum is an endemic species of Balkan Peninsula, which usually grows on limestone or dolomite substrates with deep soils rich in nutrients and at altitudinal optimum from 1200 m to 1300 m. We found a population of L. bosniacum growing on inclined slope of serpentine substrate at altitude of 970 m, at the environmental conditions that are not habitual for this species. This is the first serpentine population found in the distributional range of Bosnian lily. Cytogenetic and molecular analyses revealed variations in karyotype/genome features between serpentine and non-serpentine populations, as well as within serpentine population, in terms of changed chromosome morphology, different number and position of 18S-26S rDNA loci and CMA bands, different copy number and transcriptional activity of rRNA genes, presence/absence of B-chromosomes and different rDNA IGS length variants. Full sequence is given for IGS length variants. In addition, analysis of leaf anatomy revealed difference in number and size of stoma per leaf area between non-serpentine and serpentine populations. Changes of karyotype/genome and anatomic features found in serpentine population are discussed in respect to the extreme life conditions that are characteristic for serpentines.