Peripheral genetic structure of Helicoverpa zea indicates asymmetrical panmixia.
Seasonal climatic shifts create peripheral habitats that alternate between habitable and uninhabitable for migratory species. Such dynamic peripheral habitats are potential sites where migratory species could evolve high genetic diversity resulting from convergence of immigrants from multiple regionally distant areas. Migrant populations of Helicoverpa zea (Boddie) captured during two different seasons were assessed for genetic structure using microsatellite markers and for host plant type using stable carbon isotope analysis. Individuals (N = 568) were genotyped and divided into 13 putative populations based on collection site and time. Fixation indices (F-statistics), analysis of molecular variance (AMOVA), and discriminant analysis of principal components (DAPC) were used to examine within and among population genetic variation. Mean number of alleles per locus was 10.25 (± 3.2 SD), and allelic richness ranged from 2.38 to 5.13 (± 3.2 SD). The observed and expected heterozygosity ranged from 0.07 to 0.48 and 0.08 to 0.62, respectively. Low F ST (0.01 to 0.02) and high F IS (0.08 to 0.33) values suggest captured migrants originated from breeding populations with different allele frequencies. We postulate that high genetic diversity within migrant populations and low genetic differentiation among migrant populations of H. zea are the result of asymmetrical immigration due to the high dispersal and reproductive behavior of H. zea, which may hinder the adaptation and establishment of H. zea to peripheral habitat. These findings highlight the importance of assessing peripheral population structure in relation to ecological and evolutionary dynamics of this and other highly reproductive and dispersive species.
Southern Insect Management Research Unit USDA-ARS Stoneville Mississippi 38776; Present address: Molecular Ecology and Fisheries Genetics Laboratory School of Biological Sciences Bangor University Deiniol Road Bangor LL57 2UW UK.
Mathew
M
Seymour
Southern Insect Management Research Unit USDA-ARS Stoneville Mississippi 38776.
Omaththage P
OP
Perera
Department of Biology The Pennsylvania State University University Park Pennsylvania 16802.
Howard W
HW
Fescemyer
Southern Insect Management Research Unit USDA-ARS Stoneville Mississippi 38776; Present address: Syngenta Crop Protection 410 South Swing Road Greensboro North Carolina 27409.
Ryan E
RE
Jackson
Department of Entomology The Pennsylvania State University University Park Pennsylvania 16802.
Shelby J
SJ
Fleischer
Corn Insects and Crop Genetics Research Unit USDA-ARS Ames Iowa 50011.
Craig A
CA
Abel
DAPC; Helicoverpa; heliothine; moth; population genetics; stable isotopes