Towards resolving the systematics of Cerastium subsection Cerastium (Caryophyllaceae): A cytogenetic approach

Abstract

Analyses of mitotic chromosome numbers and nuclear DNA content were performed for 39 populations of 17 perennial Cerastium taxa from south-eastern Europe. The DNA content ranged from 2C=2.43 to 8.78pg, revealing four ploidy levels corresponding to 4x (2n=36), 8x, 12x and 16x. High-polyploid cytotypes with a greater range of ploidy (up to 2n=144) occur mostly in the central mountainous parts of the Balkan Peninsula. The chromosome number was determined for the first time for C.dinaricum (2n=36+1B), C.decalvans subsp. orbelicum (2n=36), C.decalvans subsp. glutinosum (2n=36), C.neoscardicum (2n=144), C.malyi subsp. serpentini (2n=144) and C.moesiacum s.s. (2n=144). New chromosome counts were recorded for C.arvense subsp. strictum (2n=108), C.banaticum subsp. kosaninii (2n=36) and C.grandiflorum (2n=36). For the first time, flow cytometry was used to estimate C values for six species (15 taxonomic entities). The intraspecific variation quotient of C values is high, ranging from 1.003 in C.malyi to 1.306 in C.decalvans subsp. decalvans. The variation in chromosome size among both tetra- and octoploid members of Cerastium is much more prominent than in most other angiosperm polyploid series. Significant genome downsizing after polyploidization was observed in some investigated taxa. Differences in ploidy levels and monoploid genome size values confirm the taxonomic status of C.decalvans subsp. glutinosum and C.decalvans subsp. leontopodium. The results obtained indicate a possible close relationship between C.banaticum and C.grandiflorum, but not C.arvense. © 2013 The Linnean Society of London.