2022 Volume 24 Issue 2 Pages 289-311
In Toyooka City, Hyogo Prefecture, fallow-field biotopes (hereinafter FFB) have been produced by flooding fallow fields throughout the year to maintain habitats for various aquatic plants and animals, including feeding habitats for the oriental stork Ciconia boyciana. In this study, specifically, we clarified the poorly understood habitat status of Odonata larvae, aquatic Hemiptera, aquatic Coleoptera, and frogs at the FFB. The effects of the FFB on the conservation of local aquatic animal communities were also evaluated by comparing habitat statuses in the FFB with those in the surrounding paddy fields and multitopes (i.e., earth ditches laid alongside the paddy fields). Results showed that many Odonata larvae inhabiting an irrigation pond were found in the FFB, while several peaks in the annual polyploidy of Odonata taxa were also observed. For many species of aquatic Coleoptera, larvae were less abundant in the FFB than in the surrounding paddy fields and side ditches; however, the number of adult taxa increased rapidly after August. In addition, the regal pond cruiser Epophthalmia elegans elegans, water stick-insect Ranatra chinensis, and diving beetle Eretes griseus were captured in the deep waterbody of the FFB in autumn. These results suggest that the FFB serves as a refuge and habitat in the nonbreeding season, and as a wintering site for a variety of aquatic insects; however, its function as a breeding site may not be as important as that of the paddy fields and multitopes, especially for aquatic Coleoptera. Nevertheless, the FFB is an important breeding site for some aquatic animals including the Japanese brown frog Rana japonica and annual polyphagous Odonata taxa. Overall, this study suggests that the coexistence of various water bodies, such as temporary paddy fields and side ditches, with year-round flooded biotopes effectively conserves the diversity of aquatic insects and frogs in the study region.
