In a primary dense moist evergreen forest of southern India, spatial patterns of trees ≥30 cm gbh were investigated from three contrasting 0.4-ha plots that differed in topography and amount of disturbance due to treefall. Exploratory data analysis is based on second-order neighbourhood and pair-correlation statistics used to describe the degree of clustering/regularity in patterns of all trees, and the degree of attraction/repulsion between young trees and adults. Stochastic simulations from the Markov point process models are then used to fit spatial interaction models. The results show that spatial patterns can be related to particular dynamic processes which depend on both exogenous and endogenous factors: on steep slopes disturbed by many treefalls, spatial pattern displays large clusters which can be interpreted as within-gap regeneration stages of various ages, while in areas undisturbed over a long period, interactions between young trees and adults give rise to spatial patterns consistent with substitution dynamic processes implying standing mortality rather than treefalls. Characterizing forest dynamics through spatial patterns of trees opens up the possibility of mapping structural units that might be considered as elementary functional patches of the forest mosaic.

Conversion to permanent agriculture is rapidly occurring over vast areas of the 1.8 million km2; Brazilian Cerrado; a region that is naturally a mosaic of grasslands, savannas and evergreen tropical woodlands. Yet, few studies have quantified total biomass of plant communities in this ecosystem, particularly the belowground component; a C pool of potential global significance. Total biomass (aboveground and belowground), and the quantity of biomass consumed by fires were measured in four plant communities comprising a vegetation gradient from pure grassland (campo limpo) to a woodland with a closed canopy of tall shrubs and scattered trees (cerrado denso) near Brasilia, DF, Brazil. Total aboveground biomass (TAGB) increased along this gradient from 5.5 Mg ha-1 in campo limpo to 29.4 Mg ha-1 in cerrado denso. Vegetation structure varied among communities; trees were nonexistent in campo limpo, but were at a density of 1000 ha-1 and a biomass of 12.9 Mg ha-1 in cerrado denso. Fires consumed 92 and 84% of the TAGB in campo limpo (pure grassland) and campo sujo (savanna), respectively. In cerrado aberto and cerrado denso, trees and tall shrubs were little affected by fire. Combustion factors of the TAGB in these communities was 54 and 33%, respectively. The total biomass consumed by fire ranged from 5.0 Mg ha-1 in campo limpo to 13.5 Mg ha-1 in cerrado aberto. Compared to other widespread Brazilian ecosystems (tropical dry forest and evergreen forest), the Cerrado has a lower aboveground biomass. The TAGB of cerrado denso is > 9% of that of Amazonian tropical evergreen forest. The total quantity of biomass consumed by fire, and hence emissions to the atmosphere is lower in intact Cerrado communities compared to fires in slashed tropical forest.

The effect of natural canopy gaps on the performance of naturally occurring tree seedling populations was studied in a tropical rain forest in French Guiana. This was done at two levels of scale. Firstly, on a 20 m × 250 m forest transect intersecting four canopy gaps, it was investigated how patterns of recruitment, growth and survival of seedlings of Cecropia obtusa, Dicorynia guianensis and Pourouma bicolor differed between canopy gaps and closed forest. Secondly, for one large natural canopy gap, performance of seedling cohorts established before (‘pre-gap’ cohorts) and after (‘post-gap’ cohorts) gap formation was studied in relation to environmental heterogeneity. The direct site factor (DSF) was used as an indicator of light availability in the gap zone. Cecropia specialised in large gaps, and also in specific sites within the large gap: seedling performance was increased by light, and by dead wood. Pourouma mainly germinated under closed forest conditions, where it can survive for a long period until a canopy gap is formed nearby. Pourouma seedlings adjusted well to the new gap environment but they did not specialise in specific places within the gap. Seedling location of Pourouma seedlings was mainly determined by accidental positioning before gap formation. Dicorynia was able to germinate both in gaps and under closed forest conditions. Although the number of gaps studied in this study was low, the results show that seedling establishment, early growth and survival of the three tree species were affected by canopy gaps and by the environmental heterogeneity within a large gap.

Current hypotheses to explain dynamic transitions between savanna grasslands and woodlands in Africa focus on grazing by elephant or the influence of fire. Using a simple mathematical model, this paper argues that interactions between small herbivores such as impala or buffalo and large herbivores such as elephant or giraffe may provide a plausible alternative hypothesis. The interplay of competition and facilitation between these types of herbivores could explain transitions between grassland and woodland and vice versa. A review of the literature is presented in support of this hypothesis.

ABSTRACT. Seeds with ‘imitation arils’ appear wholly or partially covered by pulp or aril but actually carry no fleshy material. The mimetic seed hypothesis to explain this phenomenon proposes a parasitic relationship in which birds are deceived into dispersing seeds that resemble bird-dispersed fruits, without receiving a nutrient reward. The hard-seed for grit hypothesis proposes a mutualistic relationship in which large, terrestrial birds swallow the exceptionally hard mimetic seeds as grit for grinding the softer seeds on which they feed. They defecate, dispersing the seeds, and abrade the seed surface, enhancing germination. Any fruit mimicry is incidental. Fruiting trees of Ormosia spp. (Leguminosae: Papilionoideae) were observed to ascertain mechanisms of seed dispersal and the role of seemingly mimetic characteristics of the seeds in that dispersal. Seed predation and seed germination were also examined. Ormosia isthamensis and O. macrocalyx (but not O. bopiensis) deceived arboreally-foraging frugivorous birds into taking their mimetic seeds, although rates of seed dispersal were low. These results are consistent with the mimetic seed hypothesis. On the other hand, the rates of disappearance of seeds from the ground under the Ormosia trees, hardness of the seeds, and enhancement of germination with the abrasion of the seed coat are all consistent with the hard-seed for grit hypothesis.

RESUMEN. Semillas con arilos falsos aparecen estar cubiertas en parte o completamente por pulpa o arilo, pero en realidad no llevan ninguna materia carnosa. El hipótesis semilla mímica propone que las semillas parecen frutos carnosos cuyas semillas están dispersadas por aves y que engañan las aves a dispersar sus semillas sin recibir una recompensa nutritiva — una relación parasítica. El hipótesis semilla dura para arenisca propone que aves grandes y terrestres tragan las semillas mímicas y excepcionalmente duras como arenisca para moler las semillas más suaves en que se alimentan; las aves defecan y dispersan las semillas, y las rascan, lo cual mejora la germinación — una relación mutua. Cualquier mimetismo es incidente. Se observaron árboles de Ormosia espp. (Leguminosae: Papilionoideae) con frutos para averiguar los mecanismos de dispersión de semillas y el papel que hacen las características aparentemente mímicas de sus semillas en esa dispersión. Se examinaron también la depredación y germinación de semillas. Las semillas mímicas de Ormosia isthamensis y O. macrocalyx (pero no O. bopiensis), engañaron aves frugivoras y arbóreas en comerlas, aunque las tasas de dispersión eran bajas. Estos resultados son consistente con el hipótesis semilla mímica. En cambio, las tasas de desaparición de semillas caídas de Ormosia, dureza de las semillas, y mejoramiento de germinación con la raedura de las capas de las semillas son consistente con el hipótesis semilla dura para arenisca.

Vegetative growth, reproductive effort, seedling establishment, and mortality of the bark epiphyte, Dimerandra emarginata (Orchidaceae), were studied over a 3-y period in the moist lowland tropical forest on Barro Colorado Island, Panama. The study included more than 350 individuals growing on 12 branches of five different host tree species. Mortality was highest among small individuals. Most deaths occurred during the dry season and were probably related to drought. Mortality among older individuals, on the other hand, was always related to the instability of the substrate, i.e. flaking bark, breaking branches or falling trees. Vegetative growth was slow. The average increase in size (= height of the most recent, fully developed shoot) was 2.7 cm over 3 y (not considering ‘stemless’ seedlings). This increase was negatively correlated with initial plant size. Growth was highly seasonal, with little variation between years. The reproductive effort increased strongly with plant size. Larger individuals produced fruits more frequently, in larger numbers and of larger size. After reproduction, plants showed reduced vegetative growth in the following year (in 1994). There was no negative effect on future reproduction. Compared to seed production, annual recruitment was very low and showed large year-to-year variation. Fewer than 50% of the seedlings survived the first dry season after germination. After 3 y, their average size was 0.5 cm. The results suggest that slow-growing epiphytes such as D. emarginata can attain considerable age and that their longevity – after an initial vulnerable juvenile stage – is almost exclusively limited by substrate durability.

This study examined whether postdispersal fruit and seed removal by terrestrial mammals of common plant species was affected by the type of item, item density (low, medium, high), and habitat (gap, mid-succession, mature). Fruits of Brosimum alicastrum and Ficus yoponensi (Moraceae), Astrocaryum mexicanum (Palmae), and Nectandra ambigens (Lauraceae), and seeds of Omphalea oleifera (Euphorbiaceae) and Cymbopetalum baillonii (Annonaceae) were tested at the Los Tuxtlas rainforest in Mexico. Item removal from 108 experimental patches (N = 2340 fruits or seeds for each plant species tested) after 5 d was lower for F. yoponensis (6.6%) than for N. ambigens (68.8%), B. alicastrum (67.8%), C. baillonii (64.0%) and A. mexicanum (60.0%). No seeds of O. oleifera were removed. A higher fruit or seed removal was observed from high density than low density food patches in A. mexicanum, C. baillonii and N. ambigens, but not in B. alicastrum and F. yoponensis. A higher fruit or seed removal was observed from food patches in mature forest than in gaps in all plant species tested. Similar removal values between open (open to all terrestrial mammals) and caged (open to small rodents) fruit and seed patches, abundant rodent live-trapping, and a scarcity of large terrestrial mammals, indicated that forest-dwelling small rodents were the main postdispersal removal agents. Differences in plant species seedling recruitment resulting from small rodent food choices can partially determine long-term forest floristic composition at the Los Tuxtlas rainforest.

At Los Tuxtlas, Mexico, presence of dung and carrion beetles, were sampled using baited pitfall traps, at the following habitats: isolated forest fragments, forest edges, plantations (coffee, cacao, mixed, citrus and allspice), live fences and pastures. A total of 14,269 beetles representing 36 species were captured. Onthophagus batesi, Canthon femoralis, Canthidium centrale, Copris laeviceps, O. rhinolophus and Deltochilium pseudoparile accounted for 75% of the captures in the overall sample from 79 sites. Across forest fragments capture rates of species and individuals were associated positively to area and negatively to isolating distance. Rarefaction analysis showed that forest fragments were the most species-rich habitats followed by the mixed and cacao plantations, the forest edge, live fences and coffee, citrus and allspice plantations. Pastures were the least species-rich habitat. Horizontal and vertical diversity of the vegetation at the habitats studied influenced the species richness of dung and carrion beetles and the number of species in common between forest fragments and human-made habitats. A significant relationship existed between the number of non-flying mammals recorded at the study sites and the richness of species and individuals of dung beetles at the habitats investigated. The relevance of this information is discussed in the light of the ecological flexibility of dung and carrion beetle species and of possible conservation scenarios involving landscapes in which isolation of forest fragments is reduced by the presence in open areas of human-made vegetation such as plantations of cacao, coffee, cacao and coffee and live fences.

Nests of leaf-cutting ants (Hymenoptera: Formicidae: Attini) are abundant disturbances in Neotropical rain forests, and could affect the plant community both while the nests are active and after they are abandoned. We measured the diversity and abundance of understorey plants (>1 m in height) in the area around active and abandoned nests of leaf-cutting ants (Atta cephalotes) at the La Selva Biological Station in Costa Rica. Sampel quadrats on active nests had reduced diversity (number of morphospecies) and abundance of both small (height >10 cm) and large (10 cm–1 m) understorey plants, when compared to the nearby forest floor (3 and 13 m from the nest edge). Abandoned nests had greater diversity and marginally greater abundance of small understorey plants relative to nearby forest; there was no difference in diversity or abundance of large understorey plants. Leaf-cutting ant nests create gaps in the plant understorey when active, but serve as centres of recruitment for small plants after they are abandoned. Thus, like canopy gaps, ant nests could play an important role in recruitment of new individuals and maintenance of plant species diversity in tropical forests.

Dual stable isotope analyses (δ13C and δ15N) of fiddler crabs from a forest-fringed, land-locked lagoon in Puerto Rico indicated the differential assimilation of material from ingested sediments. Fiddler crabs preferentially selected for nitrogen-fixing benthic microalgae (cyanobacteria) over vascular plant detritus. These results question the assumption that mangrove detritus is always the principal source of energy to estuarine consumers. Previous research from this lagoon as well as from Amazonia suggests that the magnitude of land-water ecotonal coupling may be low for these particular tropical systems where benthic algal productivity is presumably high.

The ant fauna of a rain forest in Sabah, Malaysia was sampled by using different collecting methods in three strata. In total, 524 morphospecies of ants could be distinguished. They belong to seven subfamilies and 73 genera. So far, the ant community described is the most species rich published for a primary tropical rain forest. Regarding the stratification in the forest, the leaf litter community comprised as many ant species as the lower vegetation or canopy. Furthermore the litter stratum had the highest generic diversity. The stratification of ants in rain forests seems to be a very strict one with the majority of species (75%) being related to only one stratum. This is in contrast to findings on the stratification of beetles in rain forests. The stratification and a radiation of some groups into vegetation and canopy, where a broad spectrum of permanent habitats exist, is responsible for the high diversity of ants in tropical rain forests.

The dioecious character (sex ratios and stand structures, conspecific neighbour relationships, inflorescence numbers and structure) and reproductive process (phenology, anthesis, flower visitors and fruit production) of a miombo woodland species, Uapaca kirkiana were investigated in natural populations in Malawi. The sex ratio of reproductive individuals ≥ 10 cm diameter at breast height was about 1:1 and departures from this ratio mostly resulted from a higher proportion of the males. Spatially, the sexes were randomly distributed but generally within 10 m of each other with no obvious gender differences in size. Throughout Malawi, male and female reproductive individuals flower synchronously between October–April (with a peak period in February–March). A 6 : 1 male to female inflorescence sex ratio was common. Anthesis in female inflorescences lasts almost twice as long as in male inflorescences and only the latter have any odour. On male trees, inflorescences are in fascicles, whereas on female trees, they are solitary. In both cases, the inflorescences are generally similar in size except for the peduncles of the male inflorescences which are longer than the female's. A range of insects visits U. kirkiana flowers but the most likely pollinators are bees (Apis mellifera), and beetles (Dothera bennigseni, Chelomenes lunata, Alcidodes denticulatus and Mitracamenta sp.). Apart from pollen from the male inflorescences, female flowers do not offer any obvious reward for flower visitors. Pollination studies revealed that assisted pollination did not significantly improve fruit production or seed quality over unpollinated or naturally pollinated inflorescences. Facultative agamospermy (apomixis) is suspected as a phenomenon requiring further attention in U. kirkiana.

Information on the feeding habits of the the lesser dog-faced friut bat, Cynopterus brachyotis, was obtained by the collection of food remains directly beneath daytime and feeding roosts. The bats were found to feed on the fruits of 54 plant species, the leaves of 14 species and the flower parts of four species. The seasonal phenological differences among congeneric plant species led to steady production of fruit throughout the year and the data suggets that Ficus spp. are a key component in the diet. Judging from its wide selection of fruits, C. brachyotis, is considered to be an important seed disperser. Folivory in C. brachyotis appears to be more common than previously thought. Of the leaves consumed by the bats, seven species belonged to the family Leguminosae, followed by Myrtaccae, Moraccae, Rhizophoacae and Euphorbiaccae. Friuts in general, provide an energy rich diet for phytophagous bats but most are low in protein. In contrast, leaves consumed by bats have a relatively high protein content. We suggest that folivory (by leaf fractionation) should be energetically more advantageous than the ingestion of large amounts of low protein friut or the active pursuit of mobile insects.

Petioles are not usually thought of as a habitat for wood-boring insects. The large, woody leaf petioles of Neotropical Cecropia trees, however, have a diverse coleopterous fauna: 36 beetle species in three subfamilies of Cerambycidae and Curculionidae were recorded from Cecropia leafstalks in Costa Rica. A high percentage of the petioles were colonized by beetles in many patches, though fewer were colonized in sun-exposed sites. Community composition was dependent on forest type, petiole moisture and geographical location, but not on the species of Cecropia. Species of Scolytinae were most abundant though species of Zygopinae and Lamiinae were found regularly. The host-specific scolytine genus Scolytodes dominated in most localities, although species of Hypothenemus, Coccotrypes and Xylosandrus morigerus occurred frequently. Sympatric species of Scolytodes clearly used different parts of the petioles. Brood sizes of scolytine beetles were extremely low, ranging from two to ten offspring on average. However, mortality due to parasitoid wasps or predators was low, and since fresh leaves fall close to the previously fallen ones, mortality due to dispersal may also be low. Thus, large beetle populations can exist despite extremely low brood sizes.

Nodulation of Pterocarpus officinalis appears to be widely distributed in the swamp forest of Guadeloupe even under conditions of permanent waterlogging. The large majority of the nodules were found above the water table and as such were located on large aerial buttresses or on root hairs which develop mainly in emerged soil. Further, large trees modify their environment by accumulating litter between the buttresses to the point of ensuring sufficient topographic elevation to keep a volume of soil regularly emerged. Consequently the nodules were concentrated in a small circle (5 m in diameter) around the oldest trees. A few nodules (5%) survived under the water table, provided that healthy root hairs were present, and this kept the rate of nodulation constant over a vertical gradient (0.9 nodule g−1 root DW). The C2H4-evolution rate of P. officinalis, 2.6–5.9 μmol h−1 g−1, appeared to be quite low compared to that of the potted Gliricidia sepium cuttings (19.4 μmol h−1 g−1), but was considerably higher than that of the woody liana Dalbergia monetaria (1.0 μmol h−1 g−1) from the same swamp forest site as P. officinalis. It was concluded that P. officinalis is a N2-fixing tree species under the waterlogged conditions of tropical swamp forests, and was hypothesised that the symbiotic nitrogen fixation on P. officinalis buttresses and root hairs could be considered as an additional adaptation to flooded soil and a contribution to its success in the tropical swamp forests of the Caribbean region.

Meteorological variables, bulk cloud water and precipitation (BCWP), and bulk precipitation (BP) were measured above the canopy, and throughfall (TF; n = 20) was collected beneath an epiphyte-laden canopy of a tropical montane forest (TMF) for 1 y at Monteverde, Costa Rica. Total deposition (cloud + wet + dry) of inorganic ions to the canopy was estimated using a sodium (Na+) mass balance technique. Annual BCWP and BP depths were 2678 mm and 1792 for events where mean windspeeds (u) ≥ 2 m s&supminus1;, and 4077 mm and 3191 mm for all events, respectively. Volume-weighted mean pH and concentrations of nitrate-N (NO3−-N) and ammonium-N (NH4+-N) were 4.88, 0.09 and 0.09 mg l&supminus1; in BCWP, and 5.00, 0.05 and 0.05 mg l&supminus1; in BP, respectively. Cloud water and mist deposition to the canopy was estimated to be 356 mm. Estimated deposition of free acidity (H+), NO3−-N, and NH4+-N to the canopy was 0.49, 3.4 and 3.4 kg ha&supminus1; y&supminus1;, respectively. Mean TF depth was 1054 ± 83 mm (mean ± S.E.) for events where u ≥ 2 m s&supminus1;, and 2068 ± 132 mm for all events. Volume-weighted mean pH and concentrations of NO3−-N and NH4+-N in TF were 5.72, 0.04 mg l&supminus1;, and 0.07 mg l&supminus1;, respectively. Mean fluxes of H+, NO3−-N, and NH4+-N in TF were 0.04 ± 0.01, 0.6 ± 0.2 and 1.3 ± 0.2 kg ha&supminus1; y&supminus1;, and percent net retention of these ions by the canopy was 92 ± 2, 80 ±6, and 61 ± 6%, respectively. Phosphate, potassium, calcium and magnesium were leached from the canopy. Seasonal data suggest that biomass burning increased concentrations of NO3− and NH4+ in cloud water and precipitation at the end of the dry season. Regardless, a large majority of the inorganic N in atmospheric deposition was retained by the canopy at this site.

Patterns of gene flow within 21 northern Australian populations of Syzygium nervosum a dominant, mass-flowering, monsoon rain forest canopy tree were investigated using 10 isozyme loci. S. nervosum was found to have relatively high genetic diversity within populations (He = 0.307, AP = 3.7, P = 65) but also to have significantly lower frequencies of heterozygotes than expected (Ho = 0.126) and high allelic fixation (F = 0.512). Heterozygosity and allelic fixation were not correlated with measures of genetic diversity within populations, nor were they correlated with rain forest patch size, plant size or population isolation. Within populations, trees, of the same genotype (at each loci tested) were significantly clumped at short distances (c. 20 m), whereas trees of unlike genotypes were negatively associated. S. nervosum trees however, were not clonal in origin and had unique multilocus genotypes. The results suggest that the high levels of homozygosity recorded are the result of restricted pollination, primarily among flowers within individual trees or among closely related neighbouring trees, rather than rectricted seed dispersal. High homozygosity, the large fruit crop produced by trees of this species and the lack of association between heterozygosity and plant size, indicate that, S. nervosum is self-compatible, its fecundity does not appear to be impaired by inbreeding depression.

Myrmecophytic species of the Paleotropical plant genus Macaranga (Euphorbiaceae) have hollow stems that are almost always occupied by ants of the genus Crematogaster and scale insects of the family Coccidae (Hemiptera: Coccoidea). The coccids have a cryptic endophytic lifestyle and are confined to this microhabitat. They are much more diverse than previously recognised. First data are presented on the diversity, prevalence, specificity and distribution of the coccids associated with myrmecophytic Macaranga species. Twenty-two species of Coccidae in total, including 15 previously unknown from Macaranga, were discovered from 19 species of Macaranga in Peninsular Malaysia and Borneo. The original describers tentatively assigned the known coccid species to Coccus (Coccinae) but the Macaranga coccids still require taxonomic research to establish their correct placing. The coccids varied in their host-plant specificity from species that occurred in most of the sampled Macaranga to one species that was found almost exclusively only on a single host species. In addition to their occurrence on Macaranga, only three species, C. macarangae and C. secretus and morphospecies C. 214 were found on rare occasions in the stem interior of a few other myrmecophytes and in a non-myrmecophytic liana, but did not regularly colonise these plants. Most of the coccids can be regarded as highly specific at the plant genus level.

Information is presented on the phenology, herbivory, phytochemistry and production of the tree species Polylepis quadrijuga. Leaf production was lower during the dry season than during the wet season, when minimum temperatures also occurred. Flower and fruit phenology were also seasonal. Herbivory was significantly higher for leaves expanded during the wet season (20%) than during the dry season (1%), and was also higher for younger leaves. Flavonoids, compounds known as UV-B protectors, were found in high concentration in leaves of P. quadrijuga. There was a significant positive relationship between monthly rainfall, monthly minimum temperatures and flavonoid concentration, but no relationship was found with leaf age. The annual fine litterfall for the Polylepis forest was estimated to be 3.9 t ha−1 y−1, a high value when compared to other paramo and upper montane rain forests in tropical mountains. High production was associated with high leaf nitrogen concentration (3.0–3.5%), high rates of nitrogen retranslocation (80% dry weight), and relatively low leaf longevity (8.4 mo). High production in P. quadrijuga is probably a key factor in explaining the existence of this large woody species in a paramo environment otherwise dominated by bunch grasses, cushion plants and giant rosettes of the genus Espeletia.

New leaf production in seasonal tropical forests may result from changes in water or light availability. In this study, the relationship between leaf flushing, photosynthetically active radiation (PAR) and rainfall was examined for understorey saplings in a moist tropical forest over one year. During the wet season, weeks with greater PAR were correlated with a greater proportion of saplings flushing new leaves during subsequent weeks in nine out of ten species. Rainfall was negatively correlated with subsequent leafing during the wet season for six of ten species. However, during the dry season, rainfall was positively correlated with leafing during the following weeks for six species, but the relationship was much weaker. PAR in the dry season was negatively correlated with flushing in eight species. These results support the hypothesis that under well-watered conditions, light limits leaf production, and peaks in insolation result in greater leaf production.