Genetic diversity patterns in Phragmites australis populations in straightened and in natural river sites in Lithuania

Like in many other parts of the world, Phragmites australis distribution and abundance are changing in Lithuania because of the impact of human activities on aquatic habitats. We studied P. australis genetic diversity patterns and the effect of hydrographic modifications, introduced in the mid-late twentieth century with great impact on Lithuanian landscape. The genetic diversity was studied using chloroplast DNA sequences and nuclear microsatellite markers in natural and straightened river stretches for water regulation. We found haplotypes M and L and their variants in the studied populations. The analysis of microsatellites revealed high genetic diversity within populations and significant structure both at the population and river level. We did not find differences in the distribution of genetic diversity between populations growing in natural and in straightened river stretches; however, at the local level, 5 populations in straightened river sites had higher genetic diversity values than populations in nearby natural sites within the same river, confirming seed establishment in disturbed habitats. Our results demonstrate that anthropogenic river modifications have had an impact on the genetic diversity of P. australis populations; however, disturbance is not the only factor that affects genetic diversity recruitment and dynamics in new P. australis stands.