The flowering and fruiting phenology, floral biology, pollination ecology, and breeding system of the emergent tree Ceiba pentandra were studied in the Brazilian Central Amazon. Of the 21 trees studied, 17 flowered once or twice during the 6-y study period. The mass flowering and relatively high production of nectar per flower (mean of 310 μl) resulted in a high nectar production (over 200 l per tree per season). Flowers were visited by a wide range of nocturnal (bats, marsupials, night monkeys, hawk moths) and diurnal (bees, wasps, hummingbirds) animals, but only phyllostomid bats, especially Phyllostomus hastatus and Phyllostomus discolor, played a relevant role promoting cross-pollination. Pollinations which occurred in the early morning by diurnal floral visitors were ineffective since pollen tubes did not traverse the style and reach the ovary before stylar abscission. Despite the apparently normal growth of the self-pollen tubes, controlled pollinations carried out in one tree revealed no fruit set by selfing and 16.8% fruit set by crossing. Progeny analysis from this ‘self-incompatible’ tree using isozyme markers showed that fruits resulting from mixed-pollination (i.e., 50% self- plus 50% cross-pollen on the stigma) set only 1.6% of selfed seeds. The percentage of outcrossed seeds in fruits resulting from open-pollination in two neighbouring planted trees, which flowered in isolation and concomitantly, was estimated at 91% and 71%. Two isolated trees did not set any fruits despite massive flowering, whereas two others set large quantities of seed, supporting data in the literature stating that variable degrees of self-fertility may occur in this species.

RESUMO. A fenologia de floração e de frutificação, a biologia floral, a ecologia de polinização e o sistema reprodutivo da árvore emergente Ceiba pentandra foram estudados na Amazônia Central Brasileira. Dezessete das 21 árvores estudadas (doze nativas e nove plantadas de sementes de procedência desconhecida) floriram uma ou duas vezes cada uma durante os seis anos do estudo. A maior parte das árvores nativas floriu massivamente somente em 1993 e 1996, enquanto que algumas das árvores plantadas floriram massivamente somente em 1992 e 1997. A floração massiva e a relativamente alta produção de néctar por flor (média de 310 μl de néctar secretado por flor por noite) resultaram em uma alta produção de néctar por árvore (mais

de 200 l de néctar por árvore por estação de floração). As flores de C. pentandra foram visitadas por uma grande variedade de animais noturnos (morcegos, marsupiais, macacos-da-noite, mariposas) e diurnos (abelhas, vespas, beija-flores), mas somente morcegos, especialmente Phyllostomus hastatus e Phyllostomus discolor, parecem exercer papel relevante promovendo a polinização cruzada. Não foram detectadas diferenças na capacidade dos tubos polínicos originados do auto-pólem e do pólem cruzado de se desenvolverem até o ovário e penetrarem nos óvulos. Polinizações que ocorreram no início da manhã foram inefetivas, uma vez que os tubos polínicos não tiveram suficiente tempo para atravessarem o estilete antes da sua abscisão. Apesar do aparente desenvolvimento normal dos tubos polínicos oriundos do auto-pólem, polinizações controladas executadas em uma árvore resultaram em nenhuma produção de frutos em flores auto-polinizadas e em 16,8% de produção de frutos nas flores que sofreram polinização cruzada. A produção natural de frutos (polinização aberta) na mesma árvore foi estimada em 0,7%. O uso de marcadores isoenzimáticos na análise genética da progênie dessa mesma árvore ‘auto-incompatível’ revelou que, em frutos resultantes de polinizações mistas (isto é; uma mistura contendo 50% auto-pólem e 50% pólem cruzado, depositada no estigma), apenas cerca de 1,6% das sementes foram originadas por eventos de auto-fecundação. A proporção de sementes originadas por fecundação cruzada em frutos formados naturalmente em duas árvores plantadas e vizinhas, que floriram isoladamente e concomitantemente em 1992, foi de 91% e 71%, respectivamente. Duas árvores isoladas não produziram frutos, apesar de intensa floração, enquanto que outras duas também isoladas frutificaram em abundância. Essas observações reforçam dados da literatura que indicam a ocorrência de níveis muito variáveis de auto-fertilidade entre as árvores dessa espécie.

The ant communities of the leaf litter were studied along an elevational gradient on Mount Kinabalu in primary rain forest systems ranging from dipterocarp hill forest to dwarf forest of the highest altitudes (560, 800, 1130, 1360, 1530, 1740, 1930, 2025, 2300, 2600 m a.s.l.). The litter ant fauna along the gradient included 283 species of 55 genera. The number of ant species in the leaf litter decreased exponentially without evidence of a peak in species richness at mid-elevations. This result is in contrast to many findings on altitudinal gradients in ants and other animal groups. Most ant species have a very limited altitudinal range leading to high turnover values when comparing communities of different altitudes. Of the ant species, 74% were even restricted to one site. As evident from this study, altitudinal ranges of species are very narrow. Elevational gradients are therefore extremely species-rich and might serve as a prime example of hot spots of biodiversity. This fact is of great concern when implementing conservation strategies.

The spatial patterns presented by the marsupial Micoureus demerarae were studied through capture–mark–recapture in two small Atlantic Forest fragments (areas 7.1 and 8.8 ha). The study took place from March 1995 to August 1997. Considering all captures of each individual, males did not have larger home ranges within the fragments than did females. A negative correlation was found between home range sizes and population densities. For males, home ranges overlapped often, and were larger during the breeding season. For females, home ranges did not overlap except for a short period when there were many individuals present, and home range sizes were not significantly larger in the breeding season. Five movements between the two forest fragments were detected, across 300 m of open vegetation. All the movements were performed by males during the reproductive season. M. demerarae in the small fragments therefore displays a metapopulation structure, although possibly an atypical one where only males disperse.

This study described the diet of the orange-rumped agouti Dasyprocta leporina in French Guiana. Five food types were identified in stomach contents: seeds, pulp, fibre, leaves and animal matter. D. leporina ate mainly fruit parts, pulp and seeds, although the ingestion of animals, leaves and fibre was not negligible. Food intake differed from one season to another. D. leporina was a pulp-eater (64.8% pulp in March) when fleshy fruit was plentiful and available on the ground (February–May). The level of pulp ingestion was globally in accordance with fruit production. When food resources were low (June–September), D. leporina consumed seeds and cotyledons (73.0% seeds in August) as well as animal (16.4% in July) and to a lesser level, plant parts. By focusing on other food categories, and particularly seeds, it gets nutritious food thus avoiding starvation between June–September. Large proportions of seeds appeared in stomach contents and correlations between seed quantities and ground production were negative and significant; D. leporina seemed to react to environmental factors such as rainfall and fruit production.

The spatial distribution of two rain forest tree species, Carapa procera (Meliaceae) and Vouacapoua americana (Caesalpiniaceae) was analysed within and between plots of different sizes (6.25 and 25 ha) at Paracou, French Guiana. The L(d) function was used to characterize spatial patterns, and the Lij(d) intertype to study independancy between young and adult trees. Although both species are known to be dispersed by caviomorph rodents within short distances (c. 10–20 m and up to 50 m) of parent tree crowns, the analysis of tree positions led to different spatial patterns between species depending on soil drainage characteristics. Overall, while V. americana showed a strongly aggregated spatial distribution, C. procera had a weaker propensity to depart from complete spatial randomness (CSR). A complex distribution, sometimes clustered in areas with hydromorphic soils (swamps and around streams) and sometimes very near CSR outside these areas characterized the C. procera population. When C. procera tree aggregation occurred, there was a slight attraction between juveniles and adults. The aggregation of V. americana trees was evidenced at different levels depending on the scale of investigation. Within small plots (6.25 ha), a first level of aggregation with short distance radii of c. 10–25 m giving small clusters, and a second level which is composed of small clusters aggregated at c. 40–50 m distance radius, were observed. A third level of aggregation was suggested by analysing the tree population at the larger scale (25 ha) whose boundaries outside the plot were not delimited. Aggregation of V. americana trees at all levels was enhanced by a strong attraction between juveniles and adults. These results were discussed in light of seed and seedling ecology, especially with regard to seedling and sapling gap-dependence and soil drainage, which likely affected the recruitment of juvenile trees, and henceforth final tree spatial pattern.

The relationships between body size and host specificity were studied in leaf-chewing and sap-sucking insect communities, including 792 species, feeding locally on 15 species of Ficus in a lowland rain forest in Papua New Guinea. A negative correlation between body size and host specificity, i.e., the tendency for large species to feed on numerous Ficus hosts and those smaller to have a more restricted host range, was found within both the sap-sucking and the leaf-chewing community. A more detailed analysis, which divided herbivorous species into three sap-sucking and four leaf-chewing guilds, revealed that the correlation between body size and host specificity was caused by differences in these traits between the guilds, while no such correlation was detected within any of the guilds. As the changes in feeding mode, defining various guilds, were unique evolutionary events, it is uncertain whether there is a functional relationship between feeding mode, body size and host specificity, or whether their correlation is only coincidental. It is suggested that, in the sap-sucking community at least, the positive body size versus host specificity correlation is a coincidental by-product of the causal relationship between the feeding mode and both the body size and host specificity. The causes of analogous patterns in a leaf-chewing community require further investigation. Methodological problems in the analysis of tropical insect communities, dominated by rare species, are discussed.

Frugivorous birds play an important role in parasitic mistletoe transmission among host species. The foraging behaviour and host selection of Psittacanthus schiedeanus mistletoe fruit-eating birds was studied in cloud forest remnants in Central Veracruz, México. Cedar waxwings, Bombycilla cedrorum, gray silky-flycatchers, Ptilogonys cinereus, and social flycatchers, Myiozetetes similis, eating ripe whole mistletoe fruits and defecating or regurgitating the seeds were observed. That variation in host species selection by frugivorous birds had a direct effect on mistletoe dispersion was hypothesized. To test whether mistletoe host species are visited in proportion to their abundance (total number of trees), or infested-tree abundance (total number of infested trees), or abundance of mistletoes (total number of individual mistletoe plants in each host species), the number of trees, infested trees and individual mistletoe plants were recorded. Tree abundance, infested-tree abundance and mistletoe abundance were different among host species. Frequency of birds' visits to host species varied depending on the tree, infested-tree, or mistletoe abundance. Liquidambar styraciflua was the most abundant host species with the highest number of infested trees and individual mistletoe plants, but Persea americana and Crataegus mexicana host species had the highest number of individual mistletoe plants in each tree. Our data suggest that L. styraciflua was the most selected host species by the three frugivorous birds. Host selection by birds is one behavioural factor in explaining differences in prevalence among host species, and variation in infection levels among individuals of one host species.

RESUMEN. Las aves frugívoras juegan un importante papel en la transmisión de muérdagos parásitos hacia sus árboles hospederos. La conducta de forrajeo y selección de hospedero de aves consumidoras de frutos del muérdago Psittacanthus schiedeanus fueron estudiados en remanentes de bosque mesófilo de montaña del Centro de Veracruz, México. Bombycilla cedrorum, Ptilogonys cinereus and Myiozetetes similis fueron observados consumiendo frutos maduros enteros y defecando o regurgitando las semillas. Hipotetizamos que la variación en la selección de la especie hospedera por las aves frugívoras tiene un efecto directo en la dispersión del muérdago. Para probar si las especies de árboles hospederos son visitadas en proporción a su abundancia (número total de árboles), o la abundancia de hospederos infectados (número de árboles infectados) o la abundancia de muérdagos (número total de plantas individuales de muérdago en una sola especie de árbol); el número de árboles, árboles infestados y plantas de muérdago fueron registradas. La abundancia de árboles, de árboles infestados y de plantas de muérdago fue diferente entre las especies de árboles estudiadas. La frecuencia de visitas de las aves a las especies hospederas varió de acuerdo a la abundancia de árboles, de árboles infestados y de plantas de muérdago. Liquidambar styraciflua fue la especie hospedera más abundante con el mayor número de árboles infestados y abundancia de muérdagos, pero las especies Persea americana y Crataegus mexicana presentaron el mayor número de plantas de múerdago por árbol. Nuestros datos sugieren que L. styraciflua fue la especie hospedera más seleccionada por las aves frugívoras. La selección de hospederos por las aves es uno de los factores conductuales que explican las diferencias en prevalencia entre especies de hospedero, y la variación en los niveles de infestación entre individuos de una de las especies de hospedero.

The last population of giraffes in west Africa lives in Niger in an unprotected Sahelian region inhabited by farmers and herders. The spatial behaviour of each individual of the population (n = 63) was studied by direct observation during 15 mo. Two-thirds of the population were resident in the tiger bush in the rainy season and in the nearby area of Harikanassou, a sandy agricultural region, in the dry season. Rainy season and dry season home ranges were mutually exclusive and individual home ranges were overlapping when considering one season (rainy season: 84%; dry season: 67%). The mean size of the seasonal home ranges of these resident giraffes during the dry season (90.7 km2) was twice the mean size during the rainy season (46.6 km2). A third of the population moved 80 to 200 km in three directions, and two giraffes from an isolated group from Mali moved 300 km along the Niger River. Long distance movements of such length have never been reported before, and several explanations are proposed: previous distribution, social transmission, hydrographic network and food availability, poaching events. The giraffes in Niger do not avoid rural communities; indeed, they live in densely populated regions. Furthermore, their movements, synchronized with human activities in these regions, are representative of life conditions in the Sahel.

An evaluation of whether large arborescent palms depend on large treefall gaps for recruitment to the adult stage is reported. Specifically three hypotheses were tested: (1) The light requirement of juveniles of tall arborescent palms increases as they grow in size. (2) Tall arborescent palms depend on gaps over 0.10 ha for growth and survival to maturity, due to high light requirements during the stem height growth phase. (3) Stilt-rooted palms are not dependent on gaps for juvenile height growth. The hypotheses were evaluated using data on size and crown position of individuals of tall arborescent palm species as well as data on the forest-phase in which each individual grew. The study site was a 50-ha plot in old-growth rain forest in Amazonian Ecuador. The first hypothesis was accepted for the two most common species, Iriartea deltoidea and Oenocarpus bataua, but tentatively rejected for the arborescent palm community as a whole. The second hypothesis was rejected for Iriartea and the community as a whole. Only Oenocarpus had strongly gap-dependent recruitment. The results for Iriartea and Oenocarpus were consistent with the third hypothesis.

Studies of niche overlap within communities of lizards have shown that separation may be along the three major dimensions of space, time and food. Space is usually the most important dimension where a range of habitats are involved; there is less information on the importance of microhabitat separation within a single habitat type. This study investigated microhabitat relationships of small diurnal lizard species occupying granitic rock habitat in Zimbabwe. There was statistically significant niche separation among all species in both the type of rock occupied (size, shape, number of cracks, closeness to other rocks, and vegetation cover) and the position of the lizard in the microhabitat (height on rock, slope angle, and distance to cover). Overlap of microhabitat was lowest between the generalist terrestrial skink Mabuya varia and all other species. The arboreal skink Mabuya striata was found on rocks at one site where the more saxicolous Mabuya quinquetaeniata was absent, due to competitor release. Overlap of microhabitat among rock specialists was lowest between the sit-and-wait foragers Agama kirkii and Platysaurus intermedius, as in other tropical lizard communities. The high degree of microhabitat separation was attributed to the high structural complexity of the granitic rock habitat.