Solution

Niche overlap is when two species compete for the same limiting resource, therefore they overlap and develop similar traits. Niche overlap is reduced by resource partitioning.
Resource partitioning is the process of moving things around in order to satisfy the niche size to an appropriate level. The ways in which species within ecological communities partition available resources among themselves is a major determinant of the diversity of coexisting species.
A community with more resource sharing, or greater niche overlap, will support more species than one with less niche overlap.

So, the correct answer is option D.