▁For ▁example , ▁diver gence ▁in ▁the ▁m ating ▁signals ▁of ▁two ▁species ▁will ▁limit ▁hy brid ization ▁by ▁reducing ▁one ' s ▁ability ▁to ▁identify ▁an ▁individual ▁of ▁the ▁second ▁species ▁as ▁a ▁potential ▁mate . ▁Support ▁for ▁the ▁re product ive ▁character ▁disp lacement ▁hypothesis ▁comes ▁from ▁observations ▁of ▁sym pat ric ▁species ▁in ▁over la pping ▁habit ats ▁in ▁nature . ▁In cre ased ▁pre zy got ic ▁isol ation , ▁which ▁is ▁associated ▁with ▁re product ive ▁character ▁disp lacement , ▁has ▁been ▁observed ▁in ▁cic adas ▁of ▁genus ▁Magic ic ada , ▁stick le back ▁fish , ▁and ▁the ▁flow ering ▁plants ▁of ▁the ▁genus ▁Ph lo x . ▁ ▁D iffer ential ▁fusion ▁An ▁alternative ▁explanation ▁for ▁species ▁disc rim ination ▁in ▁sym pat ry ▁is ▁differential ▁fusion . ▁This ▁hypothesis ▁states ▁that ▁of ▁the ▁many ▁species ▁have ▁histor ically ▁come ▁into ▁contact ▁with ▁one ▁another , ▁the ▁only ▁ones ▁that ▁persist ▁in ▁sym pat ry ▁( and ▁thus ▁are ▁seen ▁today ) ▁are ▁species ▁with ▁strong ▁m ating ▁disc rim ination . ▁On ▁the ▁other ▁hand , ▁species ▁lack ing ▁strong ▁m ating ▁disc rim ination ▁are ▁assumed ▁to ▁have ▁f used ▁while ▁in ▁contact , ▁forming ▁one ▁distinct ▁species . ▁ ▁D iffer ential ▁fusion ▁is ▁less ▁widely ▁recognized ▁than ▁character ▁disp lacement , ▁and ▁several ▁of ▁its ▁imp lications ▁are ▁ref uted ▁by ▁experimental ▁evidence . ▁For ▁example , ▁differential ▁fusion ▁implies ▁greater ▁post zy got ic ▁isol ation ▁among ▁sym pat ric ▁species