A Vine Plant in Georgia,U

A vine plant in Georgia,U.S.A,is known as Gelsemium spp.,and has been used as an herbal medicine.Only three species are known.Two of them,in Georgia,are found in the same overlapping areas of habitat.Two species of Gelsemium have similar insect pollinators,but pollination occurs for Gelsemium sempervirens from mid January to late March,and for Gelsemium rankinii from late March to mid April.This represents

A) ecological isolation.
B) mechanical isolation.
C) temporal isolation.
D) a process analagous to behavioral isolation in animals.
E) gametic isolation.