It seem that more and more species can interbred in cultivation where they met. Earlier I wrote about hybrid between autranii and gilanicus. Now between seedlings of C. karduchorum appear plants with vertically oriented tuber (typical for karduchorum and some kotschyanus subspecies), yellow blotches at base, creamy yellow and less deeply divided stigmatic branches. It shows that really in large collection artificial pollination and some isolation is very esential if you want to keep pure species. Here I show 2 pictures of typical C. karduchorum, 2 of supposed hybrids (between my seedlings) and pot with similar hybrids (not in my collection). Crocus speciosus and pulchellus hybridise very easy and seedlings mostly are fertile. Attached pictures are not of "show quality" - they are only informative.
Janis