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Sexual Selection, Species Recognition, and Speciation
Reinforcement is the process by which two partially reproductively
isolated species come into secondary contact with one another, and
further reproductive isolating mechanisms are evolved to reduce or
prevent hybridization between the two. Presumably, reinforcement
evolves from the selection pressures to reduce hybridization. By
definition, reinforcement cannot initiate the process of speciation
to generate reproductive isolation, but it must act through selection
on the same types of processes as at the initial stages of speciation.
In this question, we would like for you to develop a narrative about
the process of reinforcement and the issues raised by it along the
following lines.
First, briefly review the concept of reinforcement and the empirical
evidence for the operation of the process. The classic model
typically considers a system consisting of two parts: mate
preference and a mating trait. The genetic architecture of these two
components can shape the evolution of reinforcement and
nonrandom mating in general. Expound on the genetic conditions
for these two components can hasten or retard their evolution?
Then break out of the classic model and evaluate various types of
premating and postmating isolating mechanisms as effective
evolutionary pathways to reducing the level of hybridization. In
particular, many people focus on the further evolution of genetic
incompatibilities as the outcome of reinforcement. However, premating barriers to gene flow would seem to also work as well. In
particular, focus on the relative advantages and disadvantages of
each as the outcome of reinforcement, and highlight some real
world examples of each type of isolating mechanism you discuss.
Finally, consider the consequences of each of these types of mating
barriers that may evolve via reinforcement to the intraspecific
mating advantages of a species. Namely, how might the evolution
of isolating mechanisms via reinforcement influence mating
dynamics with conspecific partners – both for males and females.