2016 Volume 61 Issue 1 Pages 9-16
This study aimed to investigate the geographical distribution patterns of the grass species Echinochloa oryzicola in Japan. Panicles of this species were collected from 636 sites, except Okinawa, and their spikelet forms (C or F) were identified (first study). Subsequently, the spikelet forms of 87 specimens of E. oryzicola that were deposited in four herbariums were identified (second study). In the first study, C- and F-form spikelets were collected from 396 and 377 sites, respectively. The degree of overlap indicated independent distribution patterns of both forms across the various sites. The Moran’s I value of both the C- and F-forms indicated positive spatial autocorrelation. The results of these two spatial statistical analyses strongly suggested that the C- and F-forms have geographical trends in Japan. In the second study, a relatively higher number of specimens was collected from the Hokkaido and Kinki regions, and the geographical distribution patterns of the C- and F-forms agreed well with those of the first study. These two studies indicated that the C-form is densely distributed in Tokyo, Kanagawa, Yamanashi, Shizuoka, Aichi, Kinki region, Okayama, Tottori, Hiroshima, Yamaguchi, Fukuoka, and Oita regions, whereas the F-form is densely distributed in Hokkaido, Tohoku, Hokuriku, Chiba, and Tottori regions. Thus, our results partially contradicted previous research suggesting that the C- and F-forms of E. oryzicola are predominantly distributed in areas on the Pacific Ocean side and the Japan Sea side of Japan, respectively (Yabuno 2001).
