Research shows that genital morphology can diverge among genetically isolated populations, but not necessarily as rapidly as expected.
Evidence for stabilizing selection and slow divergent evolution of male genitalia in a millipede (Antichiropus variabilis), Evolution, April 2012, Vol. 66, no. 4, pp. 1138-1153
Evidence for stabilizing selection and slow divergent evolution of male genitalia in a millipede (Antichiropus variabilis), Evolution, April 2012, Vol. 66, no. 4, pp. 1138-1153