Two populations of a species of frog live around the gulf of california. one population has a brown back, and lives on rocky islands with brown rocks and little vegetation. a second population lives on the mainland among the vegetation and has a back that is speckled with green and brown spots. if, after many generations, a reproductive isolating mechanism evolves, what type of speciation most likely occurred? a. sympatricb. postzygotic isolationc. habitat isolationd. allopatric