I doubt if this is true. In closed communities, there may be low need for new types of the species, thus the established populations are close the the best nature in the community. However, this dependent on if reproductive system is the object of selection.
Plant species with restricted and closed recombination systems are in fact found commonly in open and pioneering habitats; Plants with open recommbination systems, on the other hand, are commonly found in closed plant communities. (Grant, 1981)