A recent study finally set out to clear up all the confusion on the exact ranges of the two members of the leopard frog complex and in doing so revealed a new species. The recent Molecular Phylogenetics and Evolution paper (link here) uncovered a leopard frog species living in the urban areas of NY, NJ, and CT.
In the figure above, light gray represents the Northern leopard frog (Rana pipiens) range while the dark gray is the range of the Southern leopard frog (Rana sphenocephala). The black indicates an overlap and the red oval from the inset stars the study sites.
Using molecular data from toe clips the authors constructed the tree below where the symbols also correlate to the symbols from the map above. The pickerel frog (Rana palustris) has also been included.
The range for this frog thus far is relatively small so more research is needed to establish a complete range and consider possible conservation measures.
Check out this 1983 paper from Hillis et al., 1983 if you’d like a more historical perspective on the Rana pipiens complex. Click here.