LEAF DOMATIA AND FOLIAR MITE ABUNDANCE IN BROADLEAF DECIDUOUS FOREST OF NORTH ASIA

Plant morphology may be shaped, in part, by the third trophic level. L eaf domatia, minute enclosures usually in vein axils on the leaf under side, may provide the basis for protective mutualism between plants an d mites. Domatia are particularly frequent among species of trees, shr ubs, and vines in the temperate broadleaf deciduous forests in north A sia where they may be important in determining the distribution and ab undance of mites in the forest canopy. In lowland and montane broadlea f deciduous forests at Kwangnung and Chumbongsan in Korea, we found th at approximately half of all woody species in all forest strata, inclu ding many dominant trees, have leaf domatia. Pooling across 24 plant s pecies at the two sites, mites occupied a mode of 60% (range 20-100%) of domatia and used them for shelter, egg-laying, and development. On average, 70% of all active mires and 85% of mite eggs on leaves were f ound in domatia; over three-quarters of these were potentially benefic ial to their hosts. Further, mite abundance and reproduction (expresse d as the proportion of mites at the egg stage) were significantly grea ter on leaves of species with domatia than those without domatia in bo th forests. Effects of domatia on mite abundance were significant only for predaceous and fungivorous mite taxa; herbivore numbers did not d iffer significantly between leaves of species with and without domatia . Comparable patterns in broadleaf deciduous forest in North America a nd other biogeographic regions suggest that the effect of leaf domatia on foliar mire abundance is general. These results are consistent wit h several predictions of mutualism between plants and mites, and indic ate that protective mutualisms may be frequent in the temperate zone.