Multivariate morphometric analysis of white grub, Holotrichia serrata (Coleoptera: Scarabaeidae) populations from India

Morphometric variation among three different geographical populations of the predominant white grub species, Holotrichia serrata (F.) (Coleoptera: Scarabaeidae) was studied through multivariate analyses. The univariate one factor ANOVA analysis has yielded 21 and 19 significant characters of male and female, respectively, which were further subjected to Principal Component Analysis (PCA) for identifying the most significant characters that explains the intraspecific morphometric variation. The first two principal components PC1 and PC2 accounted for 43.65% variation in males and characters such as length of tarsal segments especially second (TR2_L), third (TR3_L), and fourth (TR4_L), followed by male genitalia characters, width of phallobase (PH_W) and width of paramere (PA_W), total body length (TB_L), length of antennal pedicel (AP_L), length of elytra (EL_L) were found to be the significant traits contributing to the variation in the three populations of male H. serrata. In case of females, the first two principal components accounted for 46.40% and characters such as length of antennal scape (AS_L), antennal pedicel (AP_L), width of clypeus (CL_W), length of hind inner tibial spur (ITS_L) and outer tibial spur (OTS_L) were the significant characters among the female populations of H. serrata. Multivariate analysis of variance (MANOVA) and cross-validation of discriminant function analysis (DFA) also confirmed that three populations are distinct and morphometrically significant for the selected characters. Sexual dimorphism for maximum characters was observed in Andhra Pradesh and Karnataka populations. Our study aids in identification of morphological features that attributes to the intraspecific variation among the different geographical population of Holotrichia serrata in the light of speciation.