Question

Populations of some species of fish, insects, and crustaceans consist of both sexually and obligately asexually reproducing individuals. Would you expect such populations to become entirely asexual or sexual? What factors might maintain both reproductive modes? How might studies of these species shed light on the factors that maintain sexual reproduction?

Answer 1

Answer:

Entirely asexual populations of animals are rare.

The cost of sexual reproduction is considered to be twice that of asexual reproduction, because sexual females produce ≈ 50% male offspring, and males typically contribute only their genes to reproduction (Maynard Smith, 1978). Following this logic, asexual reproduction should dominate unless there is greater than a two-fold advantage to sexual reproduction.

B) Factors that might maintain a given mode of reproduction might include access or availability of mates, disease, or parasites. For example, if diseases and parasites have a major effect on the population, the Red Queen hypothesis suggests that sexual reproduction would be favored

C) Sexual selection is thought to be one way by which sexual reproduction is maintained, because only fit males are able to mate. In an environment free from enemies, asexual reproduction would be favored, but are unlikely to persist over evolutionary time, because when the environment changes they will have much less ability to adapt (owing to a lack of novel genetic variation that would be provided by segregation and recombination in a sexual population).