What has been shown to cause rapid speciation?

Rapid speciation can be caused by a number of factors, including:

- Geographical isolation: When populations of a species become geographically isolated, they can experience different selective pressures and evolve independently. This can lead to rapid speciation, especially if the isolation is long-term.

- Ecological opportunity: When a new ecological niche becomes available, it can provide an opportunity for a new species to evolve. For example, the evolution of flowering plants created a new niche for pollinating insects, which led to the rapid speciation of many insect groups.

- Hybridization: When two different species hybridize, they can produce offspring that have a combination of traits from both parents. This can lead to the evolution of new species that are distinct from either parent.

- Mutation: Mutations can introduce new alleles into a population, which can lead to new adaptations. If a mutation is beneficial, it can spread through the population and eventually lead to speciation.