Crowding and Host Plant Nutrition: Environmental Determinants of Wing‐form in Prokelisia marginata
1985
Denno, Robert F. | Douglas, Larry W. | Jacobs, Dan
Prokelisia marginata is a wing—dimorphic planthopper that feeds on the phloem sap of the intertidal marsh grass Spartina alterniflora. Populations are comprised of two wing—forms: flightless brachypters and macropters, which can fly. Macropters migrate between permanent and temporary stands of Spartina. Brachypters, because of their immobility and early age at first reproduction, are the successful morph as long as conditions remain suitable in the current patch of host plants. Wingform in planthoppers is not inherited according to any simple genetic rule; there is a strong environmental component. Various environmental cues acting on the nymphal stage trigger a developmental switch that determines adult wing—form. We investigated the wing—form response to two environmental cues, crowding and host plant nutrition, by raising planthoppers at five levels of crowding on nutritionally superior and inferior seedlings of Spartina. Percentage of macroptery was density—dependent in females but not in males. Even when raised in isolation a significant number of males eclosed as macropters. There was no consistent main effect of host plant nutrition on wing—form. However, there was a significant crowding x host nutrition interaction, which suggest that the density—dependent migration response observed at high densities is dampened if planthoppers feed on nutritionally superior hosts. The roles of crowding and host plant nutrition in the population dynamics and migration behavior of P. marginata are discussed.
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