Abstract:

【Aim】 Eysarcoris aeneus, a main pest of many economic crops, is widely distributed in Palaearctic region with humeri variable. Difference in the humerus length of “rounded humerus form” and “needle-like humerus form” suggests that intraspecific variation may exist in E. aeneus. 【Methods】 In this study, 142 specimens (98 for E. aeneus and 44 for the outgroup E. ventralis ) from 19 regions of China were examined to ascertain the morphological variation of four characters (forewing, hindwing, head and scutellum) between the two forms, “rounded humerus form” and “needle-like humerus form”, respectively, of E. aeneus with the use of geometric morphometrics approaches, including multivariate regression, principal component analysis (PCA), canonical variate analysis (CVA) and discriminant function analysis (DFA). 【Results】 Allometry was not found in all of the four characters (forewing, hindwing, head and scutellum) examined. For the four characters, though the principal component analysis showed overlap between the two forms of E. aeneus, the canonical variate analysis showed significant differences between them (P-values for Procrustes distance and Mahalanobis distance were all less than 0.01). The correctly assigned percentages of “rounded humerus form” and “needle-like humerus form” ranged from 67% to 89% specimens based on the four characters using the discriminant function analysis. 【Conclusion】 This study proved that forewing, hindwing, head and scutellum can serve efficient evaluation criteria in describing intraspecific morphological difference of E. aeneus, and scutellum is the most informative character. The geometric morphometric descriptors showed significant shape differences and overlapped centroid size between the two forms of E. aeneus, indicating that the analysis of shape is more sensitive for detecting differences among lineages than that of size. Our study shows that geometric morphometrics is efficient in describing intraspecific morphological difference of E. aeneus, and lays a foundation for intraspecific variation studies of stink bugs in future.

Key words:  Eysarcoris aeneus, geometric morphometrics, principal component analysis (PCA), canonical variate analysis (CVA), discriminant function analysis (DFA)