Is it possible to obtain a response to selection if one starts with a perfectly

Question

Is it possible to obtain a response to selection if one starts with a perfectly inbred line? Put another way, if an island is colonized by one inbred plant (selfing possible) and no other individual of its species exist on the island, is it possible to evolve and become more adapted to the local environment and eventually become a healthy genetically diverse species, or is it doomed to extinction ? Explain, can you give any examples? What assumptions do you need to make in order to get the outcome predicted?

Explanation / Answer

A perfectly inbred line is homozygous i.e. it does not have genetic diversity for the natural selection to act upon it. So, selection can not work on a homozygous line as genetic diversity is the prerequisite for it to operate. Similarly, one inbred plant which can only reproduce by selfing would stay homozygous and hence would produce only genetically identical progenies i.e. clone. Presence of genetic diversity is necessary for natural selection which then favors the variations that makes the population more adapted to the prevailing conditions. Hence, a inbred plant on an isolated island can not evolve to the prevailing conditions as natural selection can not operate on it. Here, mutation and genetic drift should not be operative. If mutation (random changes in genetic material) and/or genetic drift (changes in the allelic frequency by chance event alone) are operative, the resultant genetic variation would serve as raw material for natural selection and would make it possible for the coming generations to become more adapted to the prevailing environment.

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