Effects of interspecific competition on development and reproduction in two giant water bugs,Diplonychus japonicus vuillefroy andDiplonychus major esaki (Hemiptera: Belostomatidae) |
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Authors: | Hiroaki Okada Kenji Fujisaki and Fusao Nakasuji |
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Institution: | (1) Laboratory of Applied Entomology, Faculty of Agriculture, Okayama University, 700 Okayama, Japan;(2) Present address: Laboratory of Upland Crop Pest Research, Department of Upland Framing, Tohoku National Agricultural Experiment Station, Arai, 960-21 Fukushima, Japan |
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Abstract: | Summary We studied the interpecific competition between 2 species of predatory aquatic bugs,Diplonychus japonicus andD. major by conducting a field experiment. We set up 3 types of experimental plots in the paddy fields whereD. major predominated. The two plots contained single species of eitherD. japonicus orD. major, respectively, and one plot had both species in equal number. We compared the development and the reproductive performance
between plots in each species.
InD. japonicus, the number of eggs and early instar nymphs were significantly smaller in the plots containing both species than in the monospecific
plots. However, the numbers of late instar nymphs and newly emerged adults were not significantly different between plots.
The proportions of starved nymphs in both plots were larger than those in theD. japonicus's natural habitats. The final densities of adults in both plots were lower than those in the natural habitats. These results
suggest that lower density ofD. japonicus in these paddy fields is due to the lack of available food for nymphs rather than the effects of interspecific competition
withD. major.
InD. major, significant differences were not found in the number of eggs, each instar nymphs and adults. These results suggest that
the effects of interspecific competition did not affect the reproductive performance ofD. major. |
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Keywords: | interspecific competition field experiments Diplonychus japonicus D major |
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