Ontogenic Morphometry and Genetic Diversity of Lygus hesperus (Hemiptera: Miridae)

Lygus hesperus Knight (Hemiptera: Miridae) is an economically important pest of many field crops, including cotton, in the United States. Lygus hesperus is commonly found in the western United States, hence, it is commonly known as Western Tarnished Plant Bug. Lygus hesperus populations from different geographic regions respond differently to the identical pest management practices. Population-specific pest management strategy is required for successful management of this pest. Morphological or molecular techniques or biological assays could be used to differentiate these Lygus populations. But scientific information on ontogenic morphometry and genetic diversity of this species is mostly lacking. Therefore, ontogenic morphometry, and genetic diversity studies were conducted in the cotton entomology laboratory at Texas AgriLife Research Center, Lubbock, Texas.

Lygus hesperus has allometric ontogenic growth patterns and there was no significant difference between ontogenic shape and size trajectories between male and female. The discriminant function analysis revealed significant differences in pattern of ontogenic shape and size between Lygus hesperus and Lygus lineolaris. Thus, the morphometric technique can be used to differentiate nymphal stages of two species when they are hard to differentiate by visual observation of their morphology. Ten polymorphic microsatellite markers were developed and used in a genetic diversity study of eight Lygus hesperus populations from the Texas High Plains. Lygus hesperus population from this region showed a high degree of genetic diversity. Lygus hesperus from the Texas high Plains showed significant genetic population structure and they were differentiated into three genetically distinct populations. The molecular marker comparison study showed Simple Sequence Repeat (SSR) and Amplified Fragment Length Polymorphism (AFLP) markers are potential markers for genetic diversity study of this species when the capillary electrophoresis facility is available but Inter Simple Sequence Repeat (ISSR) markers can be next alternative when the capillary electrophoresis facility is not available. Morphometric and molecular biology knowledge and techniques developed in these studies will be useful in identification of pest management units and development of population specific precision pest management technology for Lygus hesperus.