Vol. 15 - Deutsches Primatenzentrum

Lemur News Vol. 15, 2010 Page 61
1996; Luikart et al., 1998; Piry et al., 1999) under the Infinite
Alleles Model (IAM; Kimura and Crow, 1964), the Stepwise
Mutation Model (SMM;Ohta and Kimura,1973),and the Two
Phase Model (TPM;di Rienzo et al.,1995).We varied the proportion
of the single step contribution to the TPM to identify
the P < 0.05 threshold of significance.The program identifies
populations with an excess of heterozygosity relative to
mutation-drift equilibrium which is indicative of a reduction
in the effective population size (Maruyama and Fuerst,1985).
An estimate of relationships among all individuals sampled at
each forest was done in SPAGeDi (Hardy and Vekemans,
2002),then compared to a simulation of known pedigreed individuals.
The analysis was performed to calculate the relationship
coefficients described in Queller and Goodnight
(1989) in the absence of spatial data.
Results
Genetic diversity as mean number of alleles ranged from
6.08-8.92 per population. Using the rarefacted allelic richness,
the range lowered to 5.87-7.67. The expected heterozygosity
ranged from 0.77-0.86 (P > 0.05;Fig.2) with an average
of 0.81, while the observed heterozygosity ranged from
0.65-0.84 (P < 0.05; Fig. 3) with an average of 0.74. The number
of effective breeders in the sampled populations averaged
between 12.6 and 39.6 per population (Tab. 2).
Results from Bottleneck showed that none of the 10 populations
deviated from a mutation-drift equilibrium under the
SMM.Three populations,Anjanaharibe Sud,Ambatovaky and
Anjozorobe did not show evidence of population bottleneck
under the IAM either.The rest of the populations were significant
for bottleneck events under the IAM and varying proportions
of single step contributions under the TPM.
The frequencies of the relationship coefficients estimated
using SPAGeDi were overlaid upon a simulation generated
from known pedigreed data so that each of the population’s
relative distribution of relationships could be compared with
parent offspring, full sibling, half sibling and unrelated relationship
coefficient distributions (Fig. 4). The data indicated
that the sampling was from individuals that were somewhat
related more than the unrelated individuals in the reference
simulation. Inbreeding can also be due to background relatedness
where an increased allelic identity by descent is a result
from bottleneck events in the population’s history.Relationship
coefficient distributions sup-
port the assumption that the individuals
sampled were often from family
groups. All of these sources may potentially
be due to the effects of habitat
fragmentation which is certainly
the case in the Anosibe an’ala population
where the habitat is so fragmented
that although multiple family
groups were encountered, they were
found in isolated forest fragments.
Discussion
Of the 10 Indri populations sampled,
six (Anjanaharibe Sud, Ambatovaky,
Zahamena, Betampona, Mantadia, and
Anosibe an’ala) deviated from HWE
with an excess of homozygotes.Considering
inbreeding as potential cause,
five of the populations (Anjanaharibe
Sud, Ambatovaky, Betampona, Mantadia,
and Andasibe) had relatively
high FIS and one (Anosibe an’ala) had
Y
.90
.80
.70
.60
55DD
A B C D E F G H I J
X
Fig. 2: Ranges of expected heterozygosities with 95 % confidence
intervals: A) Anjanaharibe Sud; B) Marotandrano; C)
Ambatovaky; D) Zahamena; E) Betampona; F) Anjozorobe;
G) Mantadia;H) Andasibe;I) Maromizaha; J) Anosibe an’ala.
4DF4
Y
.90
.85
.80
.75
A B C D E F G H I J
X
Fig. 3: Ranges of observed heterozygosities with 95 % confidence
intervals: A) Anjanaharibe Sud; B) Marotandrano; C)
Ambatovaky; D) Zahamena; E) Betampona; F) Anjozorobe;
G) Mantadia;H) Andasibe;I) Maromizaha; J) Anosibe an’ala.
Tab. 2: Population genetic parameter estimates for 10 populations comprised of n
samples each derived from 12 microsatellite loci for number of alleles (k), the mean
number of alleles (MNA), allelic richness (AR), probability of satisfying Hardy-Weinberg
Equilibrium (HWE), observed (HO) and expected (HE) heterozygosities, inbreeding
estimate (FIS), the number of effective breeders (Neb) estimated with the
linkage disequilibrium method and 95 % confidence interval,and results from the Bottleneck
test under the infinite allele model (IAM) and the two phased model (TPM)
with proportion of multistep mutations contributing to the P < 0.05 significance level.
n k MNA AR HWE HO HE FIS Neb 95% CI IAM TPM
ANJ 10 80 6.67 6.41 * 0.67 0.77 0.135 23.0 16.2-37.8 NS NS
TAND 10 73 6.08 5.87 NS 0.75 0.77 0.024 21.9 15.1-36.9 ** 70
VAK 11 76 6.33 5.92 NS 0.69 0.77 0.121 20.1 14.7-30.4 NS NS
ZAH 14 107 8.92 7.65 NS 0.81 0.86 0.060 39.6 28.8-61.3 ** 10
BET 10 79 6.58 6.37 ** 0.73 0.80 0.093 18.3 13.5-27.1 ** 20
ANJZ 10 83 6.92 6.70 NS 0.84 0.79 -0.066 20.9 15.1-32.5 NS NS
TAD 10 96 8.00 7.67 NS 0.75 0.85 0.120 20.1 15.3-28.3 ** 70
DASI 11 81 6.75 6.40 NS 0.73 0.81 0.095 12.6 10.2-16.2 ** 5
MIZA 10 89 7.42 7.17 NS 0.83 0.84 0.021 15.9 12.4-21.3 ** 5
ANOSIBE 10 92 7.67 7.38 * 0.65 0.85 *0.236 28.8 19.9-49.3 ** NS
* P < 0.05, ** P < 0.001; Anjanaharibe-Sud(ANJ), Marotandrano (TAND), Ambatovaky (VAK),
Zahamena (ZAH), Betampona (BET), Anjozorobe (ANJZ), Mantadia (TAD), Andasibe (DASI).
Maromizaha (MIZA), Anosibe an’ala (ANOSIBE).