Question

1) Suppose the full reproductive isolation between two populations have evolved. Can speciation in this cae be reversed, so that two forms merge into a single species? Under what conditions is this probable or improbable?

2) Plants are to undergo self-fertilization are self compatible. In a population of self compatible, a fraction will undergo self fertilization, so the inbreeding coefficient is F=0.64. In a sample of 35 plants from a population of plants, 2 alleles A and a were observed. The sample included 17AA. 5Aa, and 12aa. Are these numbers consistent with the estimated F=0.64?

Answer 1

1) Speciation is the formation of one or more new species from an existing species. The original population may form subpopulation and become reproductively isolated, such population are called sympatric population. Reproductive isolation is the existence of intrinsic barrier to the interbreeding in natural populations. Each of the intrinsic barriers is called reproductive isolating mechanism. In the above case, the two populations are in full reproductive isolation, so initially their chances to fuse or converge into a single species is basically out of requirement. But with due course of time, anthropogenic habitat change such as change in climate, local ecology, or the introduction of predators force the two diverging species to fuse into a single species. The ecological separation can be removed when the two species hybridize and give rise to fertile hybrids so that the two species can fuse. But often there are some barriers to hybridization or convergence of species like behavioral isolation, temporal isolation, ecological isolation, etc that interfere in this process. Parallely, it may be possible for the convergence of species based on many factors like reproductive failure as a part of lack of mating, topographical factors, human interventions, etc.

2) The sample included 17 AA, 5 Aa and 12 aa out of 34 plants. Alleles of A=217=34 in AA, 5 alleles of A+ 5 alleles of a in Aa; alleles of a=212=24 in aa.

Total number of alleles=34+10+24=68, frequency of allele A= and frequency of allele a=1-0.57=0.43

frequency of Aa=

Number of heterozygote individuals=(approx)

Coefficient of inbreeding,

therefore, these numbers are not consistent with the estimated F=0.64