Biology Reference
In-Depth Information
Interpopulation diversity using allozyme data are usually measured using the
coefficient of gene differentiation
(
G
ST
). G
ST
is derived by estimating the average
similarity within and between populations. G
ST
is an extension of Wright's cor-
relation (F
ST
) between two gametes drawn at random from each subpopulation.
The coefficient of differentiation is determined as follows:
GHHH
ST
=−
(
) /
T
S
T
where H
S
is the average gene diversity within populations, and HT
T
is the inter-
population gene diversity.
13.6.2 Microsatellites
Microsatellites are the most widely applied molecular markers in population
genetic studies, conservation genetics, and paternity tests because the mark-
ers are codominant, highly reproducible, and can be obtained by the PCR once
primers can be developed (
Ellegren 2004
). Microsatellites can be generated by
analysis of sequences available in GenBank, especially for species that have had
their genomes sequenced. Alternatively, microsatellite-enriched libraries can be
generated, although this can be time-consuming, costly, and technically com-
plex.
Techen et al. (2010)
describe an optimized method for constructing micro-
satellite-enriched libraries (
Table 13.3
). Microsatellites can identify multiple loci
or single loci in individuals (
Zane et al. 2002, Ellegren 2004
). Satellite sequences
scattered throughout the chromosomes can produce a series of bands that are
often specific to an individual insect. However, microsatellites may detect so
much variation within populations that it is difficult to analyze them unless
inbreeding has occurred in the population under study so that some of the vari-
ability has been lost. DNA fingerprinting using microsatellites can be done with
the PCR using specific or consensus primers (
Kirby 1990
).
Population estimates of allele and genotype frequencies can be tested for cor-
respondence to Hardy-Weinberg equilibrium conditions (
Bruford et al. 1992
),
and genetic differentiation can be calculated from microsatellite data (
Goodman
1997
, Goodnight and Quellar 1999). The high level of variation detected by sat-
ellite data make it feasible to test for paternity and to conduct studies of vari-
ability within both sexual and clonal populations (
(Brookfield 1992
). Variation
and genetic distance also can be calculated (
Hoelzel and Bancroft 1992
). Single-
locus DNA fingerprinting is easier to analyze because there are fewer bands but
advances are being made in analysis of multiple microsatellite loci (
Estoup and
Angers 1998
).
