Aylostera pygmaea

[ralphrmartin]

It's quite clear to me that (in plenty of cases at least) they are species, if that word means anything. Once, on a hill in Bolivia, I saw "three kinds of Rebutia pygmaea" all growing within a very few 10s of metres of each other, all in flower at the same time, and each of the 3 types was very uniform (all the ones with bright orange flowers also had long white spines, and so on), without any sign of intermediates. They were living in the same space, flowering at the same time, and not interbreeding.

[SimonT]

I would wonder if you took the same three types of R. pygmaea in the greenhouse then could you cross them to produce plants that were fertile?

[ralphrmartin]

Yes, a good question. It might be that the different coloured flowers were causing different pollinators to visit them.

[edds]

I would wonder if you took the same three types of R. pygmaea in the greenhouse then could you cross them to produce plants that were fertile?

That wouldn't necessarily mean they aren't valid species in the wild as long as they are effectively reproductively isolated there. Depends on which version of the biological species concept you agree with!