Abstract
Indian tasar silkmoth, Antheraea mylitta is an economically important wild silkmoth species distributed across India. A number of morphologically and ethologically well-defined ecotypes are known for this species that differ in their primary food plant specificity. Most of these ecotypes do not interbreed in nature, but are able to produce offspring under captive conditions. Microsatellite markers were developed for A. mylitta, and out of these, ten well-behaved microsatellite loci were used to analyze the population structure of different ecoraces. A total of 154 individual moths belonging to eight different ecoraces, were screened at each locus. Hierarchical analysis of population structure using Analysis of MOlecular VAriance (AMOVA) revealed significant structuring (FST = 0.154) and considerable inbreeding (FIS = 0.505). A significant isolation by distance was also observed. The number of possible population clusters was investigated using distance method, Bayesian algorithm and self organization maps (SOM). The first two methods revealed two distinct clusters, whereas the SOM showed the different ecoraces not to be clearly differentiated. These results suggest that although there is a large degree of phenotypic variation among the different ecoraces of A. mylitta, genetically they are not very different, and the phenotypic differences may largely be a result of their respective ecology.
Highlights
Populations of several species are further classified by taxonomists into subspecies, races, demes, clines and so on, of which only cline and deme have non-arbitrary definitions[1]
Few studies have been carried out with RFLP13, RAPD14, SCAR15, ISSR12,16 and other DNA markers[17], except for RFLP, the rest are dominant markers, and the estimation of allele frequencies are based on the assumption that the loci are in Hardy-Weinberg equilibrium
There is a need to identify genetic markers for a specific phenotype to differentiate ecoraces. Are these ecoraces genetically distinct from each other? Do the ecoraces form structured population? Are any of these ecoraces in decline? These questions are of considerable importance to the biology of A. mylitta. With these points in mind, we developed 32 microsatellite markers and screened eight A. mylitta ecoraces collected from different geographical locations across India to obtain insights into the population genetics of these ecoraces (Fig. 1 and Table 1)
Summary
Populations of several species are further classified by taxonomists into subspecies, races, demes, clines and so on, of which only cline and deme have non-arbitrary definitions[1]. The ecoraces are uni, bi or trivoltine depending upon the geo-ecological conditions and differ from each other in several qualitative and quantitative traits[7], such as cocoon weight and colour, larval colour, and so on Most of these ecotypes do not interbreed in nature, some of them produce offspring when mated in captivity[8]. A. mylitta primarily inhabits forested habitats, it is expected that with the gradual depletion of forest cover due to surge in the human activities the habitat lost its continuity and resulted in geographic isolation This isolation might have allowed the populations to continue separately for generations, resulting in different ecoraces. These questions are of considerable importance to the biology of A. mylitta With these points in mind, we developed 32 microsatellite markers and screened eight A. mylitta ecoraces collected from different geographical locations across India to obtain insights into the population genetics of these ecoraces (Fig. 1 and Table 1)
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