The biology of rarity: Patterns, causes and consequences.

There is a growing body of evidence suggesting that locally rare and geographically restricted species may have characteristics that differ from those of taxa that are more common. Several studies show that rare taxa have lower levels of self-incompatibility, a tendency toward asexual reproductive pathways, lower overall reproductive effort and poorer dispersal abilities. There are several mechanisms that could be responsible for such differences, but they may in practice be difficult to differentiate. Nonetheless, the documentation of recurrent rare-common differences is of vital importance because it may allow us to compensate partially for the bias of the published literature toward studies of common taxa.