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Coevolution
Hilary Skiba
I.
Coevolution
A. reciprocally induced evolutionary change between two or more species or
populations (Price)
B. change in genetic composition of an individual or species in response to
genetic change within another
II.
Types of coevolution
A. Gene-for-Gene Coevolution
i. complementary genes – one side has genes that affect the
relationship while the other side has genes that oppose the effect
ii. Ex. Resistance of plants against parasites - genes for resistance and
susceptibility are matched by genes for virulence and avirulence in
a parasite
B. Specific Coevolution
i. two species evolve in response to each other
ii. “evolutionary arms race” between prey and predator
iii. Ex. Wolves and deer – improvement in speed in the deer would
cause the wolf to increase speed in order to catch its prey
C. Guild Coevolution
i. Several species are involved and their effects are not independent
ii. Prey species interacts with two or more predators
iii. Ex. Succulent plants – cacti and euphorbs
D. Diversifying Coevolution
i. reduce mating in populations, reduce gene flow, and results in
enough reproductive isolation to cause speciation events
ii. commonly seen in parasites
iii. Ex. Crossbills and Black Spruce Pines - cone morphology and bill
morphology affects feeding
-thicker cone caused larger beaks to develop
E. Escape-and-Radiation Coevolution
i. species evolve a defense against enemies and is thereby enabled to
reproduce into a diverse group
ii. Ex. Plant/herbivore relationship- plants that evolved effective
chemical defenses were freed from predation by most herbivorous
insects, becoming diverse, and evolving into chemically differing
food sources that different insects later adapted and then
diversified again
III.
Mutualism
A. Pollination – insects depend on plant as a food source, plants need insects
to spread the pollen
B. Ants and Acacia – the ant depends on the plant for food and shelter and
the plant depends on the ant for protection from herbivores
i. Acacia develop:
a. swollen hollow thorns = ant shelter
b. extra floral nectaries = ant food
c. leaflet tips = solid food for larva and adult ants
ii. Ants develop:
a. defense against herbivores
b. aid in protecting fungal pathogen growth
IV.
Coevolution of Predators and Prey
A. Predators and Parasites - evolved adaptations for capturing prey or
infecting hosts
i. the dorsal fin of a deep-sea anglerfish
ii. larva of a trematode migrate to the intermediate hosts eye stalk and
turns it a bright color to make it more visible to the host
B. Defenses against predators and parasites
i. leaf-tailed gecko blends into the forest floor
ii. toxins in poison dart frogs
References
Futuyma, D. (2005). Evolution. Sinauer Associates Inc.
Price, P. (1996). Biological Evolution. Saunders College Publishing.
http://biomed.brown.edu/Courses/BIO48/27.Coevolution.HTML