Biology as Poetry: Evolutionary Biology

Bacteriophage Ecology Group

Adaptive Landscape

Means of visualizing the relationship between genotype and fitness.

Also known as fitness landscapes, adaptive landscapes are usually metaphorical rather than representing a mapping of actual fitness measurements onto actual genotypes. That is, adaptive landscapes are employed more as models than as actual representations of data, and this is in no small part due the difficulty associated with obtaining such data, where gathering fitness data for even a single genotype is often no small feat.

Within such representations, typically all variance in genotype is presented as a single two-dimensional plane, with genotypes displaying greater fitness rising above the plane as peaks and those displaying lower fitness falling below the plane as valleys (and with the plane itself representing, for example, the average fitness of the population). In addition, for a given environment, the topography of fitness landscapes are fixed, and it is assumed that not all genotypes associated with the landscape are found in a population (indeed, it is usually implicitly assumed that most available genotypes will not be found within a population).

The primary question in considering adaptive landscapes is one of how populations might maximize their fitness, i.e., by possessing genotypes that are found higher above the genotype plane. This can be straightforward in terms of moving up a single adaptive peak, which may be accomplished via a series of single mutations along with associated natural selection. It is less obvious, however, how populations might move away from shorter adaptive peaks in order to scale adaptive peaks that possess greater heights, i.e., greater fitness potentials. A standard answer is that it is through random processes, such as genetic drift or random environmental changes, that such shifts to the vicinity of higher peaks may occur.

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