Is Salix fursaevii Mavrodiev (Salicaceae) a palaeoendemic of the Volga River valley or an ecotype of S. triandra L.?

Salix fursaevii, a species endemic to the Volga River flood plain, was described by E. Mavrodiev and co-authors in Byull. Moskovsk. Obshch. Isp. Prir. 2012. It differs from closely related widespread S. triandra few quantitative morphological characters and, most of all its much later flowering time. This late-flowering willow known studied before as an ecotype triandra. Our study large sample s. l. revealed that 1) str. fursaevii could not be clearly distinguished using several time flowering; 2) specimens morphologically corresponding are with single exception strictly confined plain; 3) populations do differ nrITS sequences; 4) poorly differentiated chloroplast atpB-rbcL 5) representatives both taxa tetraploids 2n = 4x 76. Poor differentiation sequences is indicative intraspecific variability, geographic pattern which suggests valley probable glacial refugium source post spread