Interspecific variation in diel‐scale temporal niches is common in natural communities. Such variation changes population dynamics via effects on the growth and reproduction of individuals. Also at the community level, theory predicts that animals can reduce competition for shared resources by changing diel activity in certain situations. However, the role of diel activity at the community‐level has not been examined sufficiently. In this study, to examine whether the diel‐scale temporal niche act as a competition‐mitigating mechanism for stream fishes at the community level, we surveyed diel changes in microhabitat use and foraging, and the pattern of interspecific diet overlap in the middle reaches of a temperate stream where various fish species that seemed to be either nocturnal or diurnal coexisted. Our results suggest that the fishes forage during both daytime and night, but change their foraging mode at different times of the day, so that the foraging habits of these fish species cannot be divided simply into nocturnal and diurnal. Furthermore, fishes appeared to aggregate in the vicinity of common food resources during time zones with high availability of the resources, and therefore, inter‐guild diet overlap was high during certain time zones. On the other hand, when inter‐guild diet overlap was low, each fish species used foods or microhabitats that did not any have the potential to be used by species of another guild. Therefore, we conclude that variation in diel niche use is influenced by variation in the fundamental niche and food supply or availability rather than by competitive interaction between fishes in the stream fish community.

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Two novel isoflavonoid dimers presumably originating from 2′-hydroxygenistein, 5,7,4′- trihydroxycoumaranochroman-4-one-(3→5‴)-5″,7″,2‴,4‴-tetrahydroxyisoflav- one (1, lupinalbisone A ) and 5,7,4′-trihydroxycoumaranochro-man-4-one-(3→6″)-5″,7″,2‴,4‴-tetrahydroxyisoflavone (2, lupinalbisone B) were isolated from the roots of Lupinus albus L., and their structures involving relative stereochemistry were elucidated by spectroscopic methods. Using horse radish peroxidase and 2′-hydroxygenistein (3) as the substrate revealed the formation of these dimers together with 5,7,4′-trihydroxycoumaronochromone (4, lupinalbin A ). Dimerization of 3 caused a remarkable increase of antifungal activity.

Although previous studies have claimed that Pungtungia herzi (Cyprinidae) is an obligate brood parasite, in this study a significant proportion of P. herzi egg masses was found in crevices formed by stones and rocks, which was not guarded by hosts. Egg masses were also found in almost all nests of a goby Odontobutis obscura, suggesting that P. herzi has two alternative reproductive tactics: brood parasitic spawning and non-parasitic crevice spawning, the latter of which may occur when a shortage of reproductive resources (i.e. host nests) exists. The hatching rates of parasitic egg masses were significantly higher than those of non-parasitic egg masses, and the hatching rate of P. herzi eggs exhibited a strong positive correlation with continuous egg guarding by a reproductive O. obscura male. These results indicate that brood parasitism effectively improves reproductive success in P. herzi. The alternative reproductive tactic of this species suggests that brood parasitism has evolved directly from crevice spawning via the sharing of spawning habitat with host species.

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Sum~rznry Rhoeadine, an alkaloid from a variety of species of the genus Papaver, Papaveraceae, has been sy n thesised.

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