Quantitative Genetics, Development and Physiological Adaptation in Host Strains of Fall Armyworm

Abstract

Two genetically differentiated host strains of fall armyworm were reared on their own and each other's host plants, rice and corn, to determine whether they were physiologically adapted to their natural hosts and whether they exhibited genetically based differences in development. Larval host had a greater impact on development in the rice strain than in the corn strain, indicating that physiology could have facilitated specialization in one strain but not the other. Consequently, behavioral mechanisms are also likely to be important in the maintenance of host specificity. Comparisons between strains indicated significant differences in one trait, the rate at which larvae gained weight. Because this character had consistently high heritabilities, genetic differentiation in development is indicated. An analysis of genotype-by-environment interactions within each strain detected significant interactions for three of five traits, suggesting that genotypic performance on one host was not indicative of performance on the other. Each strain thus exhibited genetic variation that would facilitate host-associated divergence and adaptation if coupled with a mechanism that reduced gene flow between hosts. Finally, significant genetic correlations between several characters were detected when strains were reared on their natural hosts but not when they were reared on nonnatural hosts. Apparently, feeding on novel hosts caused developmental uncoupling of characters. Release from genetic constraints could provide a mechanism for physiological adjustments to newly occupied habitats.

Associations of fecundity with adult size in the cotton stainer bug Dysdercus fasciatus

“…For relatively small samples, estimates of genetic correlations are subject to large sampling errors and are, therefore, seldom precise (Robertson, 1959;Falconer, 1981). For this reason, the results presented ( (Giesel et al, 1982;Via, 1984;Service & Rose, 1985;Pashley, 1988). The results of this study (Table 1) indicate that this is also true for Dysdercus fasciatus, subject to sampling error.…”

Biologia comparada de populações de Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) em folhas de milho e arroz

“…Os resultados obtidos também encontram-se na faixa dos relatados em estudos com os biótipos "milho" e "arroz" da praga, como por exemplo, por Pashley (1988) com insetos coletados em Porto Rico (América Central) e alimentados com folhas de milho e arroz, e por Whitford et al (1988) com insetos do biótipo "milho" oriundos de Louisiana e do biótipo "arroz" de Mississipi e alimentados com quatro plantas hospedeiras.…”

“…Nessas áreas existe a possibilidade de ocorrerem os biótipos "milho" e "arroz", pois, de acordo com Pashley (1988) estes ocorrem simpatricamente em Porto Rico, Flórida, Geórgia e Louisiana.…”

Attraction of Spodoptera frugiperda Larvae to Volatiles from Herbivore-Damaged Maize Seedlings

“…Despite the polyphagous nature of the species as a whole, selection of an appropriate new host plant can impact larval growth and development. Larval performance of individual FAWs from different host strains varies considerably among host plant species (Pashley, 1988; and also can be impacted by previous damage from other herbivores (Bultman and Conard, 1998;Tindall and Stout, 2001). Given that volatiles from herbivoredamaged and undamaged plants differ quantitatively at a minimum, foraging FAW are presented with differences in olfactory cues when making a choice.…”