Competition and predation in temporary habitats (biological control, experimental ecology, amphibians, mosquitoes)
Durham, NC, Duke Univ., Diss., 1984
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| Format: | UnknownFormat |
| Sprache: | eng |
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Tag hinzufügen | Zusammenfassung: | Durham, NC, Duke Univ., Diss., 1984 Intra- and interspecific competition and predation are studied in a 3-species community of treehole-breeding mosquitoes and in populations of treefrog larvae. Although distantly related taxa, mosquitoes and many amphibians have analogous life histories. Mosquitoes do all of their growing, and amphibians do much of theirs, in the larval stage which typically occurs in aquatic habitats. The relative arrival times of species and the subsequent developmental and growth trajectories of individuals define the network of ecological interactions in both systems. An experimental approach is employed throughout to evaluate the absence of phenotypic detail common in population models. The abundances of hatchlings of two competing mosquitoes, Aedes triseriatus and Orthopodomyia signifera, and the predatory mosquito Toxorhynchites rutilus were varied in a factorial design (Chapter Two). Each species exhibited density-dependent growth, development, and survival when reared in isolation. Aedes was the superior competitor, having a larger effect on Orthopodomyia than Orthopodomyia had on itself. The predator reversed the outcome of competition. At some densities Orthopodomyia did better when the predator was present than when it was absent. Both species responded positively to predator-induced reduction in intraspecific competition by increases in growth and developmental rates. Simultaneous arrival of these species into the larval habitat is unlikely in nature. Manipulations of arrival time of a species relative to its predator (Chapter Three) and interspecific competitor (Chapter Four) reveal that the outcome of predation and competition pivots on the sequence of colonization. Subsequent colonizers compete poorly and suffer heavier predation relative to when they precede the other species. Larvae of Hyla gratiosa responded negatively to increased initial density and positively to increased predation intensity (Chapter Five). Developmental rate of larvae was more sensitive to initial density than it was to predator-induced changes in density. Growth rates were more plastic to experienced density. The repercussions of the manipulated factors are traced by inductive arguments to their ultimate effects on the populations of the interacting species. The results emphasize the necessity of incorporating more detail than abundances into population models. The implications of these results are developed with reference to control of pests by natural enemies. |
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| Beschreibung: | 214 S. |