Genetic differentiation across North America in the generalist moth Heliothis virescens and the specialist H. subflexa

Abstract

The two moth species Heliothis virescens (Hv) and H. subflexa (Hs) are closely related, but have vastly different feeding habits. Hv is a generalist and an important pest in many crops in the USA, while Hs is a specialist feeding only on plants in the genus Physalis. In this study, we conducted a comparative population genetic analysis to assess whether and how generalist and specialist life styles are reflected in differences in population structures. In Hv 98% of the total variation occurred within populations. The overall differentiation (F(ST) ) between regions was 0.006 and even lower between years (0.0039) and hosts (0.0028). Analyses of population structure suggest that all individuals form one genetically homogeneous population, except for at most 12 individuals (6%) that diverged from this cluster. Population homogeneity likely results from the high mobility of Hv and its generalist feeding behaviour. Hs exhibited substantially more population structure. Even though 96% of the total variation was attributable to within-population variability, F(ST) -values between Hs populations were 10 times higher than between Hv populations. Hs populations showed significant isolation by distance. Analyses of Hs population structure suggest at least two subpopulations and thus some degree of metapopulation structure. We speculate that the patchy distribution of Physalis- the exclusive food source of Hs - contributes to differences in population structure between these closely related species. The finding that the specialist shows more population differentiation than the generalist corroborates the notion that host specialization is not an evolutionary dead end but a dynamic trait.

Genetic diversity and susceptibility to Vip3Aa20 protein in Brazilian populations of <i>Helicoverpa armigera</i> and <i>Helicoverpa zea</i> (Lepidoptera: Noctuidae)

“…Chloridea virescens (Fabricius) (Lepidoptera: Noctuidae) showed no structure regardless of geographical scale, time, and host, with most genetic variation occurring within populations, using mtDNA markers . This is consistent with other studies performed in other countries with S. frugiperda (CLARK et al, 2007), when not considering rice and maize strains (PASHLEY, 1986), and C. virescens (HAN;CAPRIO, 2004;GROOT et al, 2011). Therefore, almost all studies with lepidopteran pests reported no genetic structure.…”

Coevolution is linked with phenotypic diversification but not speciation in avian brood parasites

“…Because host use can be related to diversity in coevolutionary interactions [25,26], we also test whether different measures of host diversity can explain the patterns observed. We calculate the breadth of host niche within the three lineages of parasites, which is a measure of how phylogenetically distant their hosts are from each other in the avian phylogeny.…”

Heliothis virescens and Bt cotton in the United States

“…By this time, cotton would have a great influence producing this generation which is probably reflected (C.A.B., unpublished). These observations indicate that perhaps there is a physiological 77 or genetic [80][81][82] differentiation in TBW host races that may be responsible for these preferences, which will be addressed below.…”

“…97 Recent calculations of gene flow between populations support this idea. About 6% of a sample from an area as wide as 1,700 km 80 show distinct genetic may involve the chemical composition of the pheromone lures and the role of other hosts. Consider for a moment that the development of commercial lures used to bait traps indeed simulate the chemical composition of the pheromone of females captured from cotton; after all, around 1980 when the lures were developed, TBW were quite abundant on this widely planted crop host.…”