Genetic diversity of the rare and endangered meadow violet (Viola pumila Chaix) at the southern margin of its range

Viola pumila Chaix is a rare violet with a Eurasian-continental distribution. It has undergone a severe population decline during the last decades, and is endangered in Europe. Its southernmost extrazonal occurrence is in northern Italy, with only four populations. Inter-simple sequence repeat markers were used to detect genetic diversity level and distribution in the Italian stand and to compare it to a small sample from Germany. Estimates of genetic diversity revealed retention of genetic variation and weak genetic structure in the Italian populations of V. pumila. Comparable levels of genetic variation were detected in the German population. Principal component and cluster analyses on the whole data-set grouped individuals regardless of their geographical distribution, pointing out that genetic diversity in the V. pumila populations surveyed is homogeneously distributed. Analysis of molecular variance showed that most of the genetic variation is within populations rather than among them. Our results indicate that habitat fragmentation has not induced genetic depauperation and differentiation in the Italian stand of V. pumila; moreover, they provide evidence of past extensive outcrossing and a common evolutionary history of the examined populations. The high diversity detected in this study suggests effective measures for conservation strategies of this rare species.