The orchids Dendrobium infundibulum and Cymbidium insigne are pollinated by the bumblebee Bombus eximius, which also pollinates the ericaceous shrub Rhododendron lyi, A study of the three plants and the bumblebee in maquis-like mountainous vegetation in northern Thailand suggests that they form a floral mimicry system with two mimics (the orchids) to one model (R. lyi). The flowers of the two orchid species offer no food reward to pollinators. Flowers of the three species show definite morphological and visual resemblance, and the species overlap to a great extent in flowering phenology and habitat Mimic flowers were much less numerous than model flowers, which occurred abundantly in the area. The rate of pollinaria removal was very low in both orchid species, resulting in a relatively small percentage of fruit set, especially in D. infundibulum. Infrequency of pollinator visits was, however, somewhat counterbalanced by long-lasting flowers. The pollinaria of the two orchid species are differently positioned on the bee, hence interference between the different reproductive systems is minimized. This is the first report which indicates floral mimicry from tropical Asia.

Seedlings of Pentaclethra macroloba (Willd.) Kuntze, a dominant, shade-tolerant species of tropical moist forest in Costa Rica, were raised under three light conditions to assess their acclimatization and growth responses to irradiance. The light environments used were full sun, partial shade (25% of full sun), and full shade (1% of full sun). To test the effect of a sudden change in light level such as would occur in the event of a treefall gap, the seedlings in the above conditions were switched between environments after two months and grown for an additional 1.5 months. Plants in full sun and partial shade had similar total weight; switching between the two environments had no effect on biomass. Plants switched from full sun and partial shade to full shade had negative growth as a result of negative CO2, flux and leaf abscission. Plants transferred from full shade to full sun had lower growth rates than those switched from full shade to partial shade because of severe leaf damage in full sun. The previous environment significantly affected the response of most growth and size characteristics to the present environment. Maximum photosynthesis changed only 30% in response to light level during growth. However, large changes in other photosynthetic and structural characteristics were found. Leaves developed in full shade had lower respiration, leaf thickness, and stomatal density and higher apparent quantum yield, specific leaf area, and chlorophyll content than leaves from full sun. Osmotic potentials were similar between treatments. Despite only small changes in maximum photosynthesis, acclimatization to extreme shade or sun rendered leaves unsuitable for large changes in environment. Consequently, in the event of a large treefall gap, plants already present in the understory will require a substantial period of adjustment before they respond to the increase in light.

This study examined the ecological distribution and abundance of the small mammal fauna in the Kora National Reserve, Kenya. Over a period of eight weeks, 3300 trap-nights yielded 11 species and a total of 298 small mammals. All 11 species were trapped in the diverse nyika habitat, whereas in the riverine habitat five species were trapped and the rock outcrops had only two species. However, the catch per trap-night was the highest on the rock outcrops compared with the riverine and nyika habitats. The duration of prebaiting had a marked effect on both diversity and abundance. With one exception, males of all species were in breeding condition whereas females tended to be more erratic. The biology of small mammal species in Kora in the dry season is discussed.

Succession was monitored over ten years in a 10×10m plot in forest with mor humus at 1550 m in the Blue Mountains of Jamaica, following the removal in January 1975 of all aerial plant parts and some of the root material. In April 1977, August–January 1980/1 and August 1984, all woody recruits in the plot were tagged and numbered, identified and measured (height), and mapped on a 1 m grid. The height of coppice was recorded. Ten of the eleven tree species present before felling produced coppice shoots. Two individuals almost attained canopy height by 1984. Twenty tree species and three shrub species were recruited from seed; six of the tree species were normally absent from the forest. Species composition changed very little with time.

The rate of seedling recruitment was greatest immediately after clearing. The overall den-sity of individuals changed little after 1977. Overall mortality of recruits was about 10% per annum. Mortality of the earliest recruits declined with time since establishment. Later recruits and individuals with poor growth had higher mortality than other plants. Mortality was not density-dependent. Growth rates of recruits were relatively slow. Only ten individuals exceeded 4 m by 1984.

Recruitment rates, density, growth and species diversity were greatest in the parts of the plot where the mor humus had been removed or piled up during the initial clearance. Recruit-ment, growth and density were least, and mortality was greatest, at the edge. There was no relationship between any of these parameters and the presence of coppicing stumps.

Tree species showed a clear spectrum from obligate gap-demanders to obligate shade-bearers. The persistence of gap-demanding species in this forest (in which gaps are normally rare) may be due to infrequent hurricanes, and also to a natural ability to produce basal sprouts. The succession conforms to an initial floristic composition model; it is slow, and we suggest that at least 50 years will elapse before the plot begins to resemble the undisturbed forest.

Production and nutrient content of small litterfall were studied for one year in four plantations of Agathis dammara ranging in age from 7 to 35 years old, in a 12-year-old stand of Pinus merkusii and in an approximately three-year-old shrub community dominated by Eupatorium species. The dense Pinus plantation produced considerably more litter (10 t/ha/yr, with 5.5 t/ha as needles) than any of the Agathis stands (2.6–6.2 t/ha/yr; 2.3–3.5 t/ha as leaves) or nearby Lower Montane Rain Forest (6.8 t/ha/yr; 5.4 t/ha as leaves). Litterfall in the Agathis forests increased with stand age. The shrubs produced sizeable amounts of litter (3.4 t/ha/yr). The various species responded differently to a drought occurring during the study period.

Pine litter generally exhibited low nutrient concentrations (on average 9.2, 1.9, 2.5, 0.4 and 6.0 mg/g of calcium, magnesium, potassium, phosphorus and nitrogen respectively in needle litter), whilst concentrations in shrub litter were generally high (37.8, 4.9, 1.4, 1.05 and 21.5 mg/g for the same elements); Agathis litter usually showed nutrient concentrations that were intermediate between those for pine or shrub litterfall with only minor differences between stands. Comparison of the present findings with observations at other tropical sites suggests that nutrient content of litterfall in plantation forests may approach that of natural forests when the former become about 20 years old. Pine plantations may constitute an exception in this regard.