Bugger, for that I am apologetic! We'll least you got to see my full response now

and certainly, this is a high possibility in all honesty that could end up with various hybridise specimens being hatched out and surviving! Lol they could be housed for a great length of time before being departed in the import, your talking months...
And well ell I think the best bet is finding the details out about where they got the D.leucomelas in all honesty.... Find their supplier and you will find out more...
and, you will commonly see a species having 'cf.' in the middle of their scientific naming which will look like Mantella.cf.madagascarensis. This basically means in Latin "consult" or you can interpret that as "compare", which normally means in regards to animal species, comparing two or more of the same species with a single irregular specimen which clearly isn't one or the other, but shows certain traits...
You will see some unusual specimens of Mantella on your travels on the internet and if you look at the Conservation. international Pocket Guide of Mantella species, you will see a lot of oddly coloured M.milotympanum or M.crocea, these would be labeled or considered a confer species.