Reproductive isolation is essential for the process of speciation and much has been learned in recent years about the ecology and underlying genetics of reproductive barriers.But plant species are typically isolated not by a single factor,but by a large number of different prezygotic and postzygotic barriers,and their potentially complex interactions.Groups with weak pollinator specificity,such as food deceptive orchids,show strong evidence for intrinsic post-mating reproductive barriers (both pre-zygotic and post-zygotic),particularly for late post-zygotic barriers like hybrid sterility.In contrast,groups with higher pollinator specificity,like the sexually deceptive orchids mostly rely on pre-mating reproductive barriers.Also the maintenance of species boundary among related sympatric species and the genetic architecture of natural hybrid zones are clearly dependent on the isolating barriers working between sympatric taxa.Population genetics of both sexually and food-deceptive orchid hybrid zones support this scenario and indicate that the rate and the evolutionary consequences of hybridization in different orchid groups are strongly affected by the types and strength of their pre-mating and post-mating barriers.