Genetic Variation within Native Populations of Endemic Silkmoth <em>Antheraea assamensis</em> (Helfer) from Northeast India Indicates Need for <em>In Situ</em> Conservation

<div><p><em>A. assamensis</em> is a phytophagous Lepidoptera from Northeast India reared on host trees of Lauraceae family for its characteristic cocoon silk. Source of these cocoons are domesticated farm stocks that crash frequently and/or wild insect populations that provide new cultures. The need to reduce dependence on wild populations for cocoons necessitates assessment of genetic diversity in cultivated and wild populations. Molecular markers based on PCR of Inter-simple sequence repeats (ISSR) and simple sequence repeats (SSR) were used with four populations of wild insects and eleven populations of cultivated insects. Wild populations had high genetic diversity estimates (H_i = 0.25; H_S = 0.28; H_E = 0.42) and at least one population contained private alleles. Both marker systems indicated that genetic variability within populations examined was significantly high. Among cultivated populations, insects of the Upper Assam region (H_i = 0.19; H_S = 0.18; H_E = 0) were genetically distinct (<em>F</em>_ST = 0.38 with both marker systems) from insects of Lower Assam (H_i = 0.24; H_S = 0.25; H_E = 0.3). Sequencing of polymorphic amplicons suggested transposition as a mechanism for maintaining genomic diversity. Implications for conservation of native populations in the wild and preserving in-farm diversity are discussed.</p> </div

A map image showing the distribution of collection sites of <i>A. assamensis</i>.

<p>Names on the map correspond to collection sites in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0049972#pone-0049972-t001" target="_blank">Table 1</a>.</p

A map showing positions of motifs resembling putative transposable elements (boxes shown in different colors) within sequenced ISSR amplicons.

<p>Abbreviations are as described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0049972#pone-0049972-t002" target="_blank">Table 2</a>. Arrows denote tandem repeats. The bold lines ( ) indicate position of nested primers (Fp2 and Ah16) within amplicon EU872512.</p

Partitioning by AMOVA of genetic variation in <i>A. assamensis</i> moths from (A) cultivated and wild populations, (B1) three regions of Northeast India and (B2) cultivated populations from 2 regions of Northeast India using ISSR marker data; (C) cultivated and wild populations, (D1) three regions of Northeast India and (D2) cultivated populations from 2 regions of Northeast India using SSR marker data.

*<p>Significance tests were performed for all P-value estimates at 1023 permutations.</p

Population-wise comparison of percentage polymorphism (%P), Nei’s gene diversity (H_i) and Bayesian heterozygosity (H_S) values determined from ISSR-PCR data and Nei’s average gene heterozygosity (H_T) values determined from SSR-PCR data. n.d. = not detectable. Hap: Number of haplotypes.

<p>Asterisks (*) indicate populations from which selected loci were cloned and sequenced. Populations with highest and lowest genetic diversity estimates are shown in bold.</p

Estimates of heterozygosity calculated from SSR data. N_a is observed number of alleles (amplicons produced) and N_e is the effective number of alleles; H_E and H_O refer to expected and observed heterozygosity values; Asterisk (*) denotes significant deviation from HWE at p<0.05.

<p>Estimates of heterozygosity calculated from SSR data. N_a is observed number of alleles (amplicons produced) and N_e is the effective number of alleles; H_E and H_O refer to expected and observed heterozygosity values; Asterisk (*) denotes significant deviation from HWE at p<0.05.</p

Details of collection sites (populations) of <i>A. assamensis</i> from NE India.

<p>Details of collection sites (populations) of <i>A. assamensis</i> from NE India.</p

A primer-wise comparison of all <i>A. assamensis</i> populations for percentage polymorphism (%P), Nei’s gene diversity (H_i), and Bayes heterozygosity estimate (H_S).

<p>GenBank Accessions for cloned and sequenced amplicons are provided. The population and moth from which the amplicon was obtained are indicated in uppercase. Amplicon size and nature of the locus is shown in subscript. The subscript “P” refers to a polymorphic locus (amplicon present in some individuals of a particular population), while the subscript “M” refers to a monomorphic locus (amplicon present in all individuals of that population).</p

Southern hybridization of various silkmoths using a putative transposable element amplicon from <i>A. assamensis</i> as probe.

<p>Genomic DNAs (A) of <i>A. assamensis moths</i> BK12 (lane 1), TR3 (lane 2), TR4 (lane 3), KG8 (lane 4); <i>B. mori</i> (lane5), <i>S. cynthia</i> (lane 6), <i>A. mylitta</i> (lane 7) and <i>A. proylei</i> (lane 8) were digested with <i>Hae</i> III. Southern hybridization of the digested DNAs with an 800 bp amplicon containing a putative mariner-like element are shown after (B) a low stringency wash and (C) a high stringency wash. Lane M shows λ DNA restricted with <i>Hin</i>d III as a size marker. Arrows denote hybridization signals that distinguish moths from different populations.</p