Browsing by Author "Hazel, Wade Nelson"

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    The evolution and ecological genetics of pupal color dimorphism in swallowtail butterflies (Lepidoptera: Papilioninae)
    Hazel, Wade Nelson (Virginia Tech, 1980-06-05)
    Data bearing on the evolution, environmental control and genetic basis of pupal color dimorphism was presented or discussed for six species of swallowtail betterflies. Papilla glauces and P. cresphontes produce only brown pupae while P. polyxenes, P. troilus, Battus philenor and Eurytides marcellus produce both green and brown pupae. Natural pupation sites of the species were located and results were generally consistent with the hypothesis of Sheppard (1958) which relates the evolution of the environmentally-cued dimorphism to environmental variation. The relative importance of texture, color and photo-period as environmental cues controlling the expression of pupal color was investigated and the results were discussed in relation to differences in the pupation sites of the species. The genetic basis of pupal color was investigated in E. marcellus by selecting for an increase in the tendency of larvae to produce green or brown pupae. The results were found to be consistent with the genetic basis of the trait as proposed by Hazel (1977). It was concluded that the primary factor responsible for the evolution of the dimorphism and the environmental cues which control its expression is nature of the pupation sites that a species utilizes.
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    The genetic basis of pupal color dimorphism in Papilio polyxenes and its maintenance by natural selection
    Hazel, Wade Nelson (Virginia Tech, 1976-06-05)
    A survey of the genetic variation in the ability to produce brown pupae was conducted using 23 broods reared from wild caught females. In addition a selection experiment was designed to investigate the genetic basis of the dimorphism. It was concluded that the genetic basis of the dimorphism is a threshold trait with quantitative genetic variation underlying the two phenotypes of green and brown pupal color. It was further concluded that the dimorphism is maintained in nature by weak stabilizing selection, thus explaining the occurrence of mismatches in pupal and background color.