Fundamentals of Conservation Biology. Malcolm L. Hunter, Jr.. Читать онлайн. Newlib. NEWLIB.NET

Автор: Malcolm L. Hunter, Jr.
Издательство: John Wiley & Sons Limited
Серия:
Жанр произведения: Биология
Год издания: 0
isbn: 9781119144175
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2.00 50 0.99 3.99 3.60 ∞ 1.00 4.00 4.00

      * Retention of heterozygosity is approximately equal to 1 − 1/(2N), where N is the population size after the bottleneck. If a population crashed to 10 individuals, about 1 − ½(10) = 1 − 0.05 = 0.95 of the genetic variation of the original population would remain.

       The formula for estimating how many alleles would remain after a bottleneck is E = mj (1 − pj) 2N , where m is the number of alleles before the bottleneck, p is the frequency of the jth allele, and N is the population size after the bottleneck. From an original set of four alleles the remaining number would be

       4 − ∑ (1 − 0.94)20 + (1 − 0.02)20 + (1 − 0.02)20 + (1 − 0.02)20 =

       4 − ∑ 0.0620 + 0.9820 + 0.9820 + 0.9820 =

       4 − ∑ ~0 + 0.666 + 0.666 + 0.666 = 2

       With a population of infinite size no genetic bottleneck occurs.

      

      Based on Frankel and Soulé 1981

Generations
Population size (N) 1 5 10 100
2 0.75 0.24 0.06 <<0.01
6 0.917 0.65 0.42 <<0.01
10 0.95 0.77 0.60 <0.01
20 0.975 0.88 0.78 0.08
50 0.99 0.95 0.90 0.36
100 0.995 0.975 0.95 0.60

      Based on Frankel and Soulé 1981

Number of alleles
Generations m = 2 m = 4 m = 12
0 2.00 4.00 12.00
1 1.99 3.87 7.78
2 1.99 3.55 5.88
8 1.67 2.18 2.64
20 1.24 1.36 1.44
1.00 1.00 1.00

      If drift erodes genetic diversity then will mutation simply replenish it? Probably not. The problem is a severe imbalance between the rates at which the two processes operate. A population bottleneck can deplete genetic diversity from a population during just a few generations if the bottleneck is narrow enough. In contrast, it has been estimated that 105–107 generations are required to regenerate allelic diversity for a single gene (Lande and Barrowclough 1987). The genetic machinery of a cell is remarkable at avoiding