If areas must be fragmented, maximize potential for dispersal between different preserves. For example, keep them as close together as possible, avoid linear arrangements, etc. Try to include all stages of succession. Since different species occur in communities at dfferent stages of succession, this will help maximize overall diversity. It is also important to remember that the only way to get to a climax community is through a successional process.
Corridors increase immigration rates to reserves.
Island Biogeography theory predicts that this should increase species richness. It should also increase population sizes and reduce inbreeding depression, reducing the risks of extinction for some organisms. On the negative side, increased movement can facilitate the spread of epidemic diseases, insect pests, and introduced species, and could reduce genetic variation between species. Corridors can increase the foraging area for wide-ranging species, reducing probability of extinction. On the other hand, corridors could facilitate the spread of fires or other disturbances.