Oes specialization must lead to an evolutionary dead end
Title: Does specialization must lead to an evolutionary dead end?
Specialization has been assumed to be an evolutionary dead end for a long time, however, recent studies showed that it might not be the case. In this paper, I will argue that specialization does not necessarily lead to an evolutionary dead end. In order to support my argument, I will provide evidence from recent studies which included large varieties of organisms: floral plants, parasites and mammals, etc. These evidences demonstrated that although specialization occurred, the evolutionary dead end was not driven by specialization. Moreover, since it happened in many types of organisms (eg: from plants to mammal), it further suggests that the validity of my argument is not simply based on rare random cases. Furthermore, I will provide a possible mechanism through which specialists can give rise to generalist, which suggests that an evolutionary dead end is not always the result of specialization.
1. Floral plants
It has been widely believed that plants that are specialized to particular pollinators (eg: hummingbirds, hawkmoths, and bats) tend to be driven to an evolutionary dead end, since these plants would evolve physical structures which are team up with their certain types of pollinators, and these structures have become too specialized to return to their generalized structures which can be visited by other pollinators. However, there is evidence showing that specialist plants such as Ruellia genus can exhibit evolutionary flexibility, which drives it away from the evolutionary dead end.
Competition tends to drive the evolution from host specialist parasites to host generalist parasites. In this way, specialization may results in evolving to generalist rather than an evolutionary dead end.
3. Mammal: Giant Panda
Although the giant panda (Ailuropoda melanoleuca) is highly specialized in diet, experiences reproductive constrains, and live in isolated habitat, a recent study using microsatellite markers has shown that its specialization is not at an evolutionary dead end. Instead, these data indicated that the giant panda is in common with other carnivores.
4. Possible mechanism through which a specialist can become a generalist.
Resource specialists such as parasites are able to switch their host species instead of being at an evolutionary dead end. One possible mechanism that enables this rapid host switching is termed as ecological fitting, which allows organisms to shift their host without evolving novel host-utilization capabilities.
Although an evolutionary dead end may be driven by overspecialization, it does not mean that it is the only outcome of specialization. Many studies have shown that specialized species are able to escape that dead end, and one possible mechanism is by becoming a generalist. Hence, specialization does not necessarily lead to an evolutionary dead end.