2006 Volume 69 Issue 5 Pages 557-560
Genji-firefly Luciola cruciata, a symbolic species in Japanese traditional agricultural landscapes, has recently been decreased. Therefore, conservation practices of this species have been tried in various parts of Japan. It was reported that the factors influencing the distribution of this species in eastern Japan differed from those in western Japan, and that the difference corresponded to topographical difference between the two regions. There are, however, few studies in which the difference is analyzed quantitatively. To compare factors influencing firefly distribution in eastern Japan with those in western Japan, we constructed regression models using firefly abundance as dependent variable and environmental measurement values as independent variables. Data were obtained from two areas: one was Ichikai Town, which is located in a hilly district in eastern Japan, and the other was Hagi City, which is located in a piedmont region in western Japan. The results showed that the dominance of gravel deposition covering riverbed and the abundance of freshwater snails Semisulcospira libertina were significant factors influencing firefly abundance in the both study areas, while such factors as the channel width, current velocity, dissolved oxygen and bank height did not performed as environmental factors constantly. We confirmed that we should be careful in applying an inductive model obtained in a study area to the other areas. It appears that regional comparison of environmental factors influencing abundance of target organisms to find the reasons that causes regional difference in environmental factors may be a way to construct models with higher universality.
