Editing Mutational meltdown (section)

== Explanation ==

           
The mechanism behind mutational meltdown is that a spontaneous deleterious mutation is introduced and after some time is eventually fixed into the population. This, in turn, leads to an accumulation in small populations where the growth rate as well as the population size both decrease. This, in consequence, allows the mutation to accumulate new deleterious alleles into the population until it is eventually extinct.<ref name="Coron_etal" /> In more detail, the accumulation of mutations in small populations can be divided into three phases. In the second phase a population starts in mutation/selection equilibrium, mutations are fixed at a constant rate through time, and the population size is constant because the fecundity exceeds mortality. However, after a sufficient number of mutations have been fixed in the population, the birth rate is slightly less than the death rate, and the population size begins to decrease. This is due to the fixation of deleterious mutations, which increases the death rate. The death rate eventually becomes too large in the population, theoretically infinite, that the time that it takes the deleterious mutant alleles to be fixated can be equated to the mean fixation time of a neutral mutation. This is only due to the small population that mutation is affecting, where the time for fixation is comparatively short. The smaller population size allows for more rapid fixation of deleterious mutations, and a more rapid decline of population size, which becomes irreversible after a certain number of generations<ref>{{cite journal |first1=Graham |last1=Rowe |first2=Trevor J.C. |last2=Beebee |title=Population on the Verge of a Mutational Meltdown? Fitness Costs of Geneticload for an Amphibian in the Wild |journal=Evolution |volume=57 |issue=1 |date=January 2003 |pages=177–181 |pmid=12643580 |doi=10.1111/j.0014-3820.2003.tb00228.x |doi-access=free}}</ref>