Colour polymorphism in common primrose (Primula vulgaris Huds.): many colours–many species?

Abstract

Primula vulgaris exhibits flower colour polymorphism in the eastern part of its range, especially pronounced on the NE coast of the Black Sea. This polymorphism in the Caucasian populations has been taxonomically described and some segregated species are listed as rare and endangered. We used sequence variation in two chloroplast noncoding regions (trnL–trnF and rpll32–trnL) and the complete nuclear internal transcribed spacer (ITS) of ribosomal DNA region to investigate correspondence between flower colour and geographical distribution of both nuclear and chloroplast haplotypes. It appears that variability in these DNA regions does not correlate with flower colour, being, however, clearly structured geographically. We used nested clade analysis to explore this geographical structure. It seems that the territory of the Colchis refugium on the E coast of the Black Sea contains both the highest flower colour and haplotype diversities. The results suggest that common primroses colonized the NE coast of the Black Sea from this refugium, spreading along the coast westward. At the same time, the analysis of ITS haplotypes indicates that P. vulgaris colonized the Crimea from NW Anatolia. This makes it clear that no segregated species can be recognized within flower colour polymorphic P. vulgaris in the Caucasus region. However, its phylogeography needs further detailed study on a broader scale.