Population Dynamics and Gene Flow of Helicoverpa armigera (Lepidoptera: Noctuidae) on Cotton and Grain Crops in the Murrumbidgee Valley, Australia

Abstract

The population dynamics of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) in the Murrumbidgee Valley, Australia, has been characterized using five highly variable microsatellite loci. In the 2001-2002 growing season, there were very high levels of migration into the Murrumbidgee Valley with no detectable genetic structuring, consistent with previous analyses on a national scale. By contrast, there was significant genetic structuring over the 2002-2003 growing season, with three distinct genetic types detected. The first type corresponded to the first two generations and was derived from local individuals emerging from diapause and their progeny. The second genetic type corresponded to generation 3 and resulted from substantial immigration into the region. There was another genetic shift in generation 4, which accounts for the third genetic type of the season. This genetic shift occurred despite low levels of immigration. During the third generation of the 2002-2003 growing season, different population dynamics was characterized for H. armigera on maize, Zea mays L., and cotton Gossipium hirsutum L. Populations on cotton tended to cycle independently with very little immigration from outside the region or from maize within the region. Maize acted as a major sink for immigrants from cotton and from outside the region. If resistance were to develop on cotton under these circumstances, susceptible individuals from maize or from other regions would not dilute this resistance. In addition, resistance is likely to be transferred to maize and be perpetuated until diapause, from where it may reemerge next season. If low levels of immigration were to occur on transgenic cotton, this may undermine the effectiveness of refugia, especially noncotton refugia.

Population Genetic Structure of the Cotton Bollworm Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) in India as Inferred from EPIC-PCR DNA Markers

“…Endersby et al [28] applied markers developed by both Scott et al [36] and Ji et al [37] to study Australian H. armigera populations collected from the southern and western regions of Australia and found no significant patterns of population substructure. The conflicting findings of Scott et al [32], [33], [34], [35], Endersby et al [28] and Weeks et al [38] were due, at least in part, to factors associated with allele drop-outs (ADO), null alleles caused by mutations at primer annealing sites [28], and microsatellite loci being associated with non-LTR RTE retrotransposable elements (TE's) in Scott et al's analyses [39].…”

“…In Australia, studies have revealed small genetic distances between widely separated populations based on isozymes [29], mitochondrial DNA polymorphisms [30], and sodium channel gene alleles [31]. In contrast, studies of Scott et al [32], [33], [34], [35] based on microsatellites suggested substantial population substructure in Australian populations of H. armigera . Endersby et al [28] applied markers developed by both Scott et al [36] and Ji et al [37] to study Australian H. armigera populations collected from the southern and western regions of Australia and found no significant patterns of population substructure.…”

Structured populations of the oriental fruit moth in an agricultural ecosystem

“…Molecular markers are widely used to investigate the genetic structure of populations (Behura 2006). Recent molecular studies of lepidopteran pest species have uncovered the effect of various factors on population structuring and dynamics at different spatial scales, such as dispersal‐related gene flow (Scott et al. 2005, 2006; Kim et al.…”

Survival strategies of Dalbulus maidis during maize off‐season in Brazil

“…Molecular techniques are important tools in the study of populations (Welsh & McClelland, ; Williams et al., ) and have been used for determining gene flow and migratory potential in insects (Laffin et al., ; Scott et al., , ; Oliveira et al., ). Using the random amplified polymorphic DNA‐polymerase chain reaction (RAPD‐PCR) technique, Oliveira et al.…”

“…Molecular techniques are important tools in the study of populations (Welsh & McClelland, 1990;Williams et al, 1990) and have been used for determining gene flow and migratory potential in insects (Laffin et al, 2004;Scott et al, 2005Scott et al, , 2006Oliveira et al, 2007). Using the random amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR) technique, Oliveira et al (2007) showed that D. maidis populations from Northeastern Brazil differ genetically from those collected in the Central-South region of Brazil, suggesting a restriction in gene flow between populations from these distant regions.…”