Adaptation of morphological and ecological characteristics of Digitagia ciliaris (Retz.) Koeler in adjacent habitats

Cultivation experiments were conducted on Digitagia ciliaris (Retz.) Koeler populations collected from adjacent habitats including an upland field and a levee of a field in Okayama and Kyoto prefectures, and also a flowerbed and along a roadside near the flowerbed in Akita prefecture, with the aim of assessing intraspecific variation in morphological and ecological traits. The following results were obtained: Adjacent populations in each prefecture showed differences in earliness of heading, seed (spikelet) size and dormancy. Individuals from upland fields and the flowerbed population had earlier heading, smaller seeds and stronger seed dormancy compared to populations from levees of upland fields and the roadside near the flowerbed (Fig. 1 and Table 2). Differences were also observed in seed production characteristics. D. ciliaris collected from upland fields and the flowerbed tended to allocate more dry matter to seeds and produce more and smaller seeds than that growing in levees and along the roadside (Figs 2, 3). Judging from the environment of each sampling site, population differentiation is thought to be a result of the selective pressures of plowing, weeding and competition with other plants (Table 3). D. ciliaris populations are thought to adapt their morphological and ecological characteristics to their habitats. These adaptations may enable the species to grow in various habitats such as upland fields, levees of fields, flowerbeds, and along roadsides throughout Japan.