Coevolution

Coevolu

tion

The reciprocal

change of a

biological object

triggered by the

change of a

related object.

Darwin’s Theory

Coadapta

tion

Where might it occur?

• Interspecific competition for food or space

•Parasite/ host interactions

•Predator/ prey interactions

•Symbiosis

•Mutualisms

Types of Coevolution

•Specific Coevolution•Gene-for-gene Coevolution•Diffuse or Guild Coevolution•Escape-and-radiate Coevolution

•Diversifying Coevolution

Gene-by-gene Coevolution

-the mutual interactions are between individual loci in two species.

- For each gene causing resistance in a host there is a corresponding (matching) gene for virulence in the parasite or pathogen

Specific Coevolution (Coadaptation)

-One species interacts closely with another, and changes in one species induce adaptive changes in the other, and vice-versa.

Diffuse Coevolution-the whole groups of species interact

with other groups of species (guild) rather than pairs of species.

*GUILD- is defined as a group of species using the same class of environmental resources in a similar manner—for instance, phloem feeders (greenfly: Aphidina), pollinators, and predators.

The concept of guild coevolution is important because

it emphasizes that the evolutionary unit of an

interaction may be broader than a pair of species

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Escape-and-radiate Coevolution

A specific form of how guild coevolution may involve both adaptation and speciation

• It differs from other concepts of coevolution in that it explicitly includes periods during which the interaction between the taxa does not occur.

period

Ehrlich and Raven postulated that in response to selection by herbivores, a plant species may evolve new defenses that enable it to escape herbivory and to flourish so well that it gives rise to a clade of descendant species with similar defenses.

At some later time, one or more species of herbivores adapt to the defenses and give rise to an adaptive radiation of species that feed on the plant clade. In this scenario, the evolutionary diversification of both herbivores and plants is enhanced by their interactions.

Diversifying Coevolution• Can be defined as

reciprocal evolution between species in which the interaction causes at least one of the species to become subdivided into two or more reproductively isolated populations

Differences in Interactions

EndGroup 1