What is coevolution?
Coevolution involves two or more species which exert selective pressures on each other and evolve in response to each other.
The key idea is because each species involves in response to each other the selective environments is constantly changing.
When does coevolution occur?
Selective pressure will be strongest when there is a close ecological relationship. Close relative in terms as species who are specialists rather than generalists.
How do we study Coevolution?
There are different levels that we look at coevolution. The study of adaptations of the individuals, interactions between species or broad evolutionary patterns.
Does coadaptation demonstrate coevolution?
Some biologist would say that having coadaptation does not give evidence to the parallel evolution between taxa. To convincingly show coevolution you must show a parallel evoltuion between taxa.
An example of this would be the Fig Trees and Fig Wasps.
The figs have a specialist relationship with the wasps. The wasps act as pollinators for the figs. Coadaptations happen with these species. The receptive figs produce scents that are specific to a particular pollinator species. The shape of the ostiole is specifically shapped to the head of the particular wasp species. The morphology of individuals flowers specialized to a particular wasp species.
The Fig starts to develope and the ostiole opens up. The female wasp crawls in and lays here eggs in the plant with pollen from the fig she was born from. The eggs hatch and the females fly out and find another fig.
Congruent phylogenies due to cospeciation is strong evidence for coevolution.