Habitat Isolation

∞ generated and posted on 2016.12.13 ∞

Barriers to reproduction that result from organism occupation of distinct microenvironments in what otherwise is the same location.

Habitat Isolation is both hard and easy to accomplish as it occurs via two species, or would-be species, residing simultaneously in the same location and not in the same location at the same time, i.e., occupying different aspects of the same place and thereby not coming into contact with each other.

Environments can contain numerous aspects, many of which overlap geographically. Thus, for example, in the same location can exist a tree with its trunk, branches, and leaves, soil, and perhaps a rock or two that are covered in moss.

For organisms that are sufficiently small, these different aspects of the same place can be almost literally worlds apart. As such, contact might never take place, allowing for reproductive isolation despite relative spatial as well as temporal proximity.

One likely important means of habitat isolation is seen in terms of host preference among symbionts. That is, if two parasites, for example, spend all of their time in association with different host species then they are unlikely to find each other for the sake of mating.

Note that unlike geographical isolation, habitat isolation tends to have a genetic component. That is, organisms tend to choose to be in specific locations within environments because of underlying, genotype-encoded tendencies. It does not necessarily follow, however, that these tendencies evolved for the sake of reproductive isolation. Instead, occupying distinct habitats likely allows for specialization in resource procurement and only secondarily can it keep populations separated from each other.

As such, habitat isolation, like geographical isolation, can be viewed as a prezygotic barrier to reproduction that seemingly exists predominantly for reasons that are other than for the sake of reproductive isolation. Indeed, over the scales that tiny organisms exist, the distances that can be found between local habitats can be viewed almost as geographical in their nature.