The Ewens-Watterson test for neutrality at 7 microsatellite loci in Spodoptera exigua

The Ewens-Watterson test for neutrality of microsatellite markers showed that F-value (sum of square of allelic frequency) lied outside the lower and upper limit of 95% confidence region of expected F value in 3 loci (Spe08, Spe10, Spe12) . According to results of Ewens-Watterson test for neutrality for markers, some loci were not neutral and may be linked with some selection traits. If a neutral allele statistically associated with a selected allele at another locus or genes where selection is operating significantly may be carried along and alleles cannot be separated from their genetic background. This phenomenon is known as hitchhiking. Genetic hitchhiking can be potent force in changing allelic frequency and heterozygosity (Kumar et al. 2009)

Locus-wise data on the number of alleles (Na), number of effective alleles (Ne), mean observed (Mean Ho) and expected (Mean He) heterozygosities, F statistics, and Hardy-Wienberg Equilibrium (HWE) obtained by analyzing seven populations of Spodoptera exigua.

<p>Among four loci (Table 2), Spe09 had the highest number of alleles, whereas Spe06 had the lowest. Average observed and expected heterozygosities ranged from 0.007 to 0.172 and from 0.194 to 0.767, respectively. Locus Spe02 had the highest observed heterozygosity and locus Spe06 had the lowest observed heterozygosity. Loci Spe11 and Spe06 had the highest and lowest expected heterozygosity, respectively. </p><p> </p><p>The highest values of F_is and F_it were detected in Spe09 and the lowest on Spe02. F_stvalues ranged from 0.123 to 0.346, detected in Spe06 and Spe02 loci, respectively. All four loci showed departures from the Hardy-Weinberg equilibrium. </p

AMOVA of 7 tested geographic populations of Spodoptera exigua using 4 microsatellites loci.

<p>Analysis of molecular variance (AMOVA) was performed using ARLEQUEIN version 3.11 (Excoffier et al. 2005). A two-part AMOVA analysis was conducted to check genetic divergence (FST) as a factor of variation between individuals within a given population and between populations. Molecular variance analysis showed significant variations among and within populations, 21 and 71 percent, respectively </p

Distance genetic matrix (above diagonal) and population pairwise FST of 7 tested regions comparison by 4 microsatellites loci (below diagonal).

<p>Genetic distance and pair-wise FST values between regions are shown in Table 5. The minimum genetic distance was found between the Moghan-Zarghan pair (0.116) and the maximum between the Esfahan-Sabzvar pair (0.722). Computed FST values ranged from 0.102 for the Kalposh-Miandoab to 0.349 for the Moghan-Esfahan. FST values were significant for all paired combinations (P < 0.05).<br></p

The Map of Iran showing the collection sites of Spodoptera exigua

We used of pheromone trap (Green Universe Company of Espain) for collection of specimens. Male adults of <i>S. exigua</i> were captured from sugar beet fields in seven locations in Iran: Kalposh, Gonbad, Esfahan, Sabzvar, Moghan, Miandoab and Zarghan during May 201

Results from the Bayesian clustering analysis in STRUCTURE, using k=2. Each population represented by a vertical line with different colors representing the assignments probabilities to each of the clusters.

<p>We inferred population structure using a Bayesian clustering algorithm as implemented in the software STRUCTURE (Pritchard et al. 2000, Falush et al. 2003). The most probable number of genetic clusters based on the log probability of the data was inferred following the method of Evanno et al. (2005). We varied the number of genetic clusters (K) from 1 to 10 and ran 10 independent simulations for each k with a burn-in period of 50,000 iterations, followed by 50,000 Markov chain Monte Carlo steps. For all simulations, the admixture model was used. The distribution of log- likelihoods for the number of genetic clusters (K) from the Bayesian clustering analysis with STRUCTURE peaked at estimates of k=2. In this k, 52.9 % of individuals could be assigned to one of the clusters with more than 50% probability. The ∆k method by Evanno et al (2005) favored k=2 than the others, with a seven–fold higher value of ∆k. The assignment of this cluster with respect to population is illustrated in Fig. 3. The most individuals collected from Gonbad and Esfahan regions were assigned to cluster 1; whereas, individuals assigned with high probability to cluster 2 were found in Moghan, Sabzvar and Zarghan regions. Most individuals from Kalposh and Miandoab regions were assigned in cluster 2.</p><p></p><p></p