Does specialization must lead to an evolutionary dead end Term Paper

Does specialization must lead to an evolutionary dead end - Term Paper Example The term ‘specialist’ refers to organisms that are adapted to a narrow range of environmental conditions and thus occupy one extreme of the adaptation band. On the other end are ‘generalists’, which are able to utilize a wider range of environmental conditions. Factors such as â€Å"jack of all, master of none† and freedom from natural enemies, have been used to justify the prevalence of specialists, however; it has also been postulated that in spite of these advantages, specialization would gradually lead to loss of genetic variations, thus disabling capacity of adaptation to altered set of environmental conditions. These factors would eventually lead to extinction of a specialized organism, a theory first put forward by Cope IN 1896 and termed â€Å"law of the unspecialized† (Kelly and Farrel, 1998). Another implication of this concept is that the specialists are derived from generalists and the change is irreversible. This theory has been ch allenged by larger number of recent studies, and the evidences contradicting the implications of this theory are mounting. These evidences have proved that either no directionality exists in the evolution of specialists and generalists or that the generalists have evolved from specialist ancestors (Stireman III, 2005). In either case specialization definitely does not lead to an evolutionary dead end. That this trend is not an exception or restricted to a few taxa, is evidenced by the fact that such reports are available for organisms belonging to varied phyla including angiosperms, insects, fishes, mammals and microorganisms. This paper aims to prove that specialization does not definitely lead to an evolutionary dead end using evidences from relevant researches on floral plants, parasites, and mammals. As further evidence of this concept a plausible mechanism through which transition of specialist to generalist has been reported to occur will also be discussed. II. EVIDENCES FROM FLORAL PLANTS Floral plants depend on various species acting as pollen vectors for the completion of their reproductive cycle. Thus pollen biology is an integral part of study of evolution of floral plants. Darwin had stressed the importance of the role of pollen vectors in the reproduction of floral plants and its ecological and evolutionary significance (Harder and Aizen, 2010). Specialization of plants in context to their pollination apparatus and pollinators has major impact on the diversification of the species and is of paramount significance in its sympatric reproductive isolation, even leading to speciation (Gegear and Burns, 2007). Cope’s law has been traditionally applied to pollination biology as well and the hypothesis that specialized pollination systems have evolved from ancestral generalized systems has been accepted unchallenged. This has neither been established nor studied. However, among the recent reports challenging the universality of Cope’s law, some belong to highly specific dependence of floral plants and their pollination vectors. The genera Ruellia with approximately 300 species is characterized by diverse floral morphology and varied pollinators namely bees, hummingbirds, hawk moths, bats, butterflies etc.