evolution against hybridization

A species of wild flower (Drummond's phlox ) has evolved to produce flowers colored purple-blue when grown alone but red when grown with sister species Phlox cuspidata to prevent it hybridizing with it presumably because, if it hybridizes, the plant just wastes energy producing seeds for hybrids that are not well adapted to either niche ( and any niche ) the two parent species have adapted to thus natural selection selects against such hybridization.

http://phys.org/news/2014-09-wildflowers.html

This is an unusual example of what can help to make one species split into two species.

Originally posted by humy
A species of wild flower (Drummond's phlox ) has evolved to produce flowers colored purple-blue when grown alone but red when grown with sister species Phlox cuspidata to prevent it hybridizing with it presumably because, if it hybridizes, the plant just wastes energy producing seeds for hybrids that are not well adapted to either niche ( and any niche ) the tw ...[text shortened]... .html

This is an unusual example of what can help to make one species split into two species.

Presumably some local pollinating insects have a colour preference?