On the southern distributional limit of the pool frog, Pelophylax lessonae (Camerano, 1882): the first record in Volgograd region, Russia

Distribution and types of population systems of green frogs (Pelophylax esculentus complex) in the northwest of Volgograd region were studied. The pool frog (P. lessonae) was reliably recorded in two localities of the area studied by use of the precise nuclear DNA flow cytometry method. That allowed to shift the southern boundary of this species area by 30 km. It is zoogeographically important that new records extend the range of the species distribution from the forest-steppe to the steppe zone. Two types of green frog population systems were revealed: a) R-type, ‘pure’ populations of P. ridibundus, and b) R-L-type, a mixed population system including P. ridibundus and P. lessonae. No hybrid P. esculentus was found. Refs 12. Figs 1. Tables 1.