A flowering vine plant,Gelsemium spp.,includes two separate species that formerly occupied a large,common habitat area,and currently occupy overlapping areas in the southeastern United States.Gelsemium sempervirens and Gelsemium rankinii have reproductive isolation,which has allowed them to exist as separate species due to
A) allopatric speciation. B) sympatric speciation. C) prezygotic speciation. D) postzygotic speciation. E) parapatric speciation.