Chromosomal variability in the genus Primula (Primulaceae)

Abstract

Chromosome numbers and measurements were recorded in 47 individuals of ten taxa of Primula, representing eight species and two subspecies from ten populations. The basic numbers of chromosomes were x = 8, 9 or 11, and they were mostly metacentric, medium-long to medium-small, ranging in length from c. 3.6 μm to 1.6 μm. Diploid chromosome numbers of 2n = 2x = 24 and 22 were scored for the first time in P. loeseneri Kitag. and P. prenantha Balf. & Sm., respectively. A new ploidy level of 2n = 4x = 44 was found in P. burmanica Balf. & King. The recorded diploid numbers of the remaining species confirmed earlier reports. Interspecific variability in chromosome numbers was correlated with heterogeneity in their mean length. Comparison of the data with those in the literature revealed that the observed variability of chromosomal characters was compatible with the other taxonomic criteria and supports the current taxonomic delimitation. Chromosomal variation at the diploid level is the predominant feature in Primula evolution, and allopatric speciation has played a major role in its specific diversity. Subgen. Aleuritia could represent the main clade from which the other subgenera have evolved. The origin of the chromosome numbers, geographical distribution and evolution of the species were assessed, and the parallel polyphyletic mode of evolution in the genus was confirmed. © 2006 The Linnean Society of London.