Genetic analysis of scattered populations of the Indian eri silkworm, Samia cynthia ricini Donovan: differentiation of subpopulations

Abstract

Deforestation and exploitation has led to the fragmentation of habitats and scattering of populations of the economically important eri silkworm, Samia cynthia ricini, in north-east India. Genetic analysis of 15 eri populations, using ISSR markers, showed 98% inter-population, and 23% to 58% intra-population polymorphism. Nei’s genetic distance between populations increased significantly with altitude (R2 = 0.71) and geographic distance (R2 = 0.78). On the dendrogram, the lower and upper Assam populations were clustered separately, with intermediate grouping of those from Barpathar and Chuchuyimlang, consistent with geographical distribution. The Nei’s gene diversity index was 0.350 in total populations and 0.121 in subpopulations. The genetic differentiation estimate (Gst) was 0.276 among scattered populations. Neutrality tests showed deviation of 118 loci from Hardy-Weinberg equilibrium. The number of loci that deviated from neutrality increased with altitude (R2 = 0.63). Test of linkage disequilibrium showed greater contribution of variance among eri subpopulations to total variance. D’2IS exceeded D’2ST, showed significant contribution of random genetic drift to the increase in variance of disequilibrium in subpopulations. In the Lakhimpur population, the peripheral part was separated from the core by a genetic distance of 0.260. Patchy habitats promoted low genetic variability, high linkage disequilibrium and colonization by new subpopulations. Increased gene flow and habitat-area expansion are required to maintain higher genetic variability and conservation of the original S. c. ricini gene pool.

Population genetic characterization of the Japanese oak silkmoth, Antheraea yamamai (Lepidoptera: Saturniidae), using novel microsatellite markers and mitochondrial DNA gene sequences

“…An. yamamai is an important insect resource for the agricultural industry in Asia, including South Korea, but no population genetic information is available for its domestic or foreign populations (Liu et al, 2010;Pradeep et al, 2011;Singh et al, 2012). Inferring the population genetic structure of this species would be important for systematic domestication and subsequent cocoon production, along with the traditional perspectives to understand the evolutionary process of the populations.…”

“…For example, the wild and domesticated populations of A. assamensis from India have been studied to estimate their genetic diversity using inter-simple sequence repeats (ISSR) and simple sequence repeats (SSR, Singh et al, 2012). In the eri silkworm, Samia cynthia ricini, found in Northeast India, ISSR markers have been employed to estimate the genetic structure of its unexploited, scattered populations at various altitudes, as well as the genetic interactions among its patchy subpopulations (Pradeep et al, 2011). Using limited samples, Liu et al (2010) investigated the genetic diversity and genetic structure of B. mori, A. pernyi, and Samia cynthia ricini collected in China using randomly amplified polymorphic DNA markers.…”

ISSR Primer Selection for Genetic Variability Analyses with Jaborandi (Pilocarpus microphyllus Stapf ex Wardlew., Rutaceae)

“…The number of fragments by ISSR primer may vary considerably, depending on the species. Some authors [3,[30][31][32][33], observed a total number of bands per primer lower than 10 (about five) with the primers UBC-807, UBC-810, UBC-812, UBC-813, and UBC-856, which were relatively uninformative in their respective analyses. However, other authors, such as NAN et al [27,[34][35][36][37] reported an abundant generation of bands for these same primers, showing an average of 20 fragments per primer.…”