Vertical Stratification and Caloric Content of the Standing Fruit Crop in a Tropical Lowland Forest1

Fruit abundance in tropical forests thus far has been studied in relation to consumer populations. Area–based surveys that focus on the quantity and quality of the standing fruit crop of an entire plant community, however, are lacking. This paper presents the results of a four–month study on the seasonality and vertical distribution of the standing fruit crop within a tropical forest during the dry season in southern Venezuela. Fruit numbers ranged from 262,000 to 424,000 fruits/ha. The standing crop was between 39 and 92 kg/ha, yielding 67,000 to 126,000 kj. Fruits were not evenly distributed in different forest layers. They were most abundant in the canopy above 16 m and scarce between 4 and 12 m above the ground. Despite a scarcity of fruits in the mid–strata, the caloric value of the total fruit supply peaked within a narrow layer of subcanopy at 12 to 16 m above ground due to a high amount of energy per fruit. Palms fruited mostly in this layer, their fruits contributing 59 percent of the energy supplied by all fruits. Above 12 m, we found a broader range of fruit sizes than in the forest below 12m. Small–sized fruits were distributed in the understory and in the canopy but were nearly absent from die mid–story. Corresponding to the abundance of small–sized fruits in the canopy, small frugivorous species, such as members of the Thraupidae, limited their foraging to the canopy strata whereas larger avian frugivores foraged mainly in die mid–story.     

Comparative Roosting Ecology of Cynopterus (Chiroptera: Pteropodidae) Fruit Bats in Peninsular Malaysia1

Although the use of modified roosts has been reported in more than 20 species of bats in the tropics, comparative studies of the roosting ecology of congeneric tent‐roosting species are notably lacking. In the Paleotropics, this unique behavior has been described in two species belonging to the genus, Cynopterus: C. sphinx and C. brachyotis. However, it is not known whether tent roosting is an essential component of their roosting ecology, or whether the behavior is found in other members of the genus. In this study we characterize the roosting ecology of four sympatric species of Cynopterus in peninsular Malaysia and use these data to address two main questions. (1) Do all four species use modified roosts and, in those that do, is tent‐roosting obligate or opportunistic? (2) Do species pairs overlap in roost preferences and roosting habitat and, if so, is there evidence for interspecific interactions in relation to these resources? We radio‐tracked bats at two floristically distinct sites and located a total of 249 roosts. Interspecific roost niche overlap was minimal at both sites and we found no evidence for interspecific competition for roost resources at the local level. Species differences in roosting ecology were defined primarily by spatial separation of roosting habitats and secondarily by within‐habitat differences in roost selection. Importantly, we found that although periodic use of modified roosts was a characteristic shared by all four species, most roosts were unmodified, indicating that tent roosting is a facultative behavior in Malaysian Cynopterus.     

Dietary strategies of Old World Fruit Bats (Megachiroptera,Pteropodidae): how do they obtain sufficient protein?

The complexity of dietary strategies evolved by megachiropterans (Pteropodidae) is gaining recognition, although there are relatively few reports of feeding habits other than frugivory, and even fewer of non-herbivorous ones. This paper reviews the information obtained so far on how the diets of Old World fruit bats may provide them with sufficient protein, as most fruits are known to be low in this vital nutrient. There is evidence to suggest that pollen, leaves or insects may provide wild pteropodids with the extra protein that studies in captivity have shown to be necessary.     

Roosting Requirements of Two Frugivorous Bats (Sturnira lilium and Arbiteus intermedius) in Fragmented Neotropical Forest1

As tropical forest fragmentation accelerates, scientists are concerned with the loss of species, particularly those that play important ecological roles. Because bats play a vital role as the primary seed dispersers in cleared areas, maintaining healthy bat populations is critical to natural forest regeneration. Observations of foraging bats suggest that many Neotropical fruit‐eating species have fairly general habitat requirements and can forage in many different kinds of disturbed vegetation; however, their roosting requirements may be quite different. To test whether or not general foraging requirements are matched by equally broad roosting requirements, we used radiotelemetry to locate roost sites of two common frugivorous bat species (Sturnira lilium and Artibeus intermedius) in a fragmented forest in southeastern Mexico. Sturnira lilium roosted inside tree cavities and selected large‐diameter roost trees in remnant patches of mature forest. Fewer than 2 percent of trees surveyed had a mean diameter equal to or greater than roost trees used by . S. lilium, Artibeus intermedius roosted externally on branches and vines and under palm leaves and selected roost trees of much smaller diameter. Compared to random trees, roost trees chosen by A. intermedius were closer to neighboring taller trees and also closer in height to these trees. Such trees likely provide cryptic roosts beneath multiple overlapping crowns, with sufficient shelter from predators and the elements. While males of A. intermedius generally roosted alone in small trees within secondary forest, females roosted in small groups in larger trees within mature forest and commuted more than three times farther than males to reach their roost sites. Loss of mature forest could impair the ability of frugivorous bats to locate suitable roost sites. This could have a negative impact on bat populations, which in turn could decrease forest regeneration in impacted areas.     

Pollinators of Syntopic Marcgravia Species in Costa Rican Lowland Rain Forest: Bats and Opossums

Abstract: The visitors of four syntopically occurring species of Marcgravia (M. nervosa, M. serrae, M. mexicana , and M. nepen-thoides ) in the Atlantic lowland rain forest at La Selva Biological Station in Costa Rica were observed. The four species differed in flowering phenology and morphology of inflorescences. Flowers of all species opened during the night and the stamens dropped before dawn. All species were visited by small nectar-feeding bats (Phyllostomidae: Glossophaginae). Marcgrovia nepen-thoides , with much larger nectaries, additionally attracted two species of opossums, Caluromys derbianus and Didelphis marsu-pious . Judging from the large distance between nectaries and flowers, glossophagine bats probably are inefficient pollinators of this species, and merely exploit a non-flying mammal pollination system.     

Disperser- vs. Establishment-Limited Distribution of a Riparian Fig Tree (Ficus insipida) in a Costa Rican Tropical Rain Forest1

Studies were conducted at the La Selva Biological Station in Costa Rica and in a greenhouse in California to determine the factors accounting for the nonrandom distribution of the riparian fig tree Ficus insipida Willd. along streams in the La Selva Biological Reserve and adjacent deforested lands. We also evaluated the potential seed dispersers of this tree relative to the role of the fruit‐eating fish Brycon guatemalensis that previously was proposed to be an important disperser of F. insipida seeds in this system. At La Selva, we recorded the fig‐foraging activities of vertebrates at fruiting F. insipida trees, surveyed for the presence or absence of F. insipida along streams of different sizes, and determined the fate of fig seedlings transplanted in different riparian habitats. In the greenhouse, we measured seed germination and seedling survival and growth under different light and soil pH conditions mimicking natural conditions. The findings provided evidence that (1) the tree occurs along the larger streams running through forest habitat and only along smaller streams with relatively high light availability; (2) bats (Artibeus spp.) and fish are the major dispersers of F. insipida seeds; (3) the seedlings are subject to mortality not only from low light conditions but also from treefalls, frequent flooding, and bank erosion; and (4) high light levels and near neutral soil pH result in relatively better seed germination, faster growth, and higher survival rates of seedlings. Overall, our results suggest that this fig tree is dispersed mainly by bats and fish and is more establishment‐limited than disperser‐limited in its local distribution in the La Selva rain forest habitat.     

Temporal Variation in the Relative Abundance of Fruit Bats (Megachiroptera: Pteropodidae) in Relation to the Availability of Food in a Lowland Malaysian Rain Forest

The aims of this study were to investigate the diet and relative abundance of fruit bats in a lowland Malaysian rain forest and to test the hypothesis that the local assemblage structure of fruit bats varies significantly over time in relation to the availability of food. In total, 352 fruit bats of eight species were captured during 72,306 m² mist‐net hours of sampling between February 1996 and September 1999. Three species of fruit bats (Balionycteris maculita, Chironax melanocephalus, and Cynopterus brachyotis) that fed on a wide range of “steady state” and “big bang” food resources were captured continuously throughout the study period, with no significant variation in capture rates over time. In contrast, five species that fed exclusively or almost exclusively on “big bang” food resources were sampled intermittently, with significant temporal variation in the capture rates of two species (Cynopterus horsfieldi and Megaerops ecaudatus). Significant variation in the capture rates of the remaining three species (Dyacopterus spadiceus, Eonycteris spelaea, and Rousettus amplexicaudatus) could not be detected due to small sample sizes. Since ephemeral “big bang” food resources were only sporadically available within the study area and were associated with large canopy trees and strangler figs, these results suggest that food abundance, or the availability of specific food items, may be important factors limiting local fruit bat species diversity in old‐growth Paleotropical rain forest. Thus, only three fruit bat species were locally resident within the forest throughout the study period. Therefore, further studies on the ranging behavior and habitat requirements of Malaysian fruit bats are required to assess the adequacy of existing reserves and protected areas.     

Seed Rain Produced by Bats and Birds in Forest Islands in a Neotropical Savanna1

The high degree of isolation of forest “islands” relative to “continental” forested areas creates a naturally fragmented landscape in the savanna ecosystem. Because fragmentation can affect the intensity and quality of biological interactions (e.g., seed dispersal) we examined the abundance and species richness of seed rain produced by birds and bats in three different parts of forest islands (center, edge, and exterior) located at the Estación Biológica del Beni, Bolivia. Despite the fact that we found higher species density of seeds in the seed rain at the center of forest islands, when comparing species richness corrected for observed differences in density, species richness was higher at the edge of islands. The three parts of the islands did not differ in total number of seeds. Three genera (Byrsonima, Ficus, and Piper) contributed the most seeds to the seed rain. We found differences in the abundance of dispersed seeds probably because of the variation related with the disturbance line, where the savanna matrix interacts with the forest islands. Carollia perspicillata, Carollia brevicauda, and Sturnira lilium were the bats that contributed most to seed dispersal within forest islands, and Schistochlamys melanopis and Tyranneutes stolzmanni were the most important birds. The movement of seeds produced by bats and birds within forest islands of the savanna is crucial to assure the continuity of ecological process and dynamics of these forest islands.     

Species-specific Seedling Responses to Hurricane Disturbance in a Puerto Rican Rain Forest1

Seedling dynamics were followed in a Puerto Rican forest for 20 months following a severe hurricane to study the interactive effects of hurricane debris, nutrients, and light on seedling diversity, density, growth, and mortality. Three treatments (debris removal, an unaltered control with hurricane debris, and chemical fertilization added to hurricane debris) altered levels of forest debris and soil nutrients. Canopy openness was measured twice using hemispherical photographs of the canopy. We examined the demographic responses of six common species to treatments over time. Seedling densities increased for all six species but the only significant treatment effects were increased densities of the pioneer tree Cecropia and the shrub Palicourea in the debris removal treatment. Seedling growth declined with declining light levels for four species but not for the pioneer tree Alchornea or the non‐pioneer tree Dacryodes. Only Cecropia and the non‐pioneer tree Chionanthus had treatment effects on growth. Mortality also differed among species and tended to be highest in the fertilized plots for all but Cecropia and Dacryodes. We found only some of the expected differences between pioneer and non‐pioneer plants, as each species had a unique response to the patchy distributions of organic debris, nutrients, and light following the hurricane. High local species diversity was maintained through the individualistic responses of seedlings after a disturbance.     

Temporal and Spatial Diversity and Distribution of Arboreal Carabidae (Coleoptera) in a Western Amazonian Rain Forest1

Diversity of arboreal carabid beetles was sampled by fumigation in 100 3 × 3 m stations within a 100 × 1000 m terra firme forest plot in Ecuadorian Amazonia. Nine sampling dates from January 1994 to October 1996 yielded 2329 individuals belonging to 318 species of which more than 50 percent were undescribed species. A high percentage of the species sampled were rare; the proportion that occurred once per sampling date (singletons) ranged from 50.0 to 62.5 percent. Estimates of species richness were from 82 to 282 species of arboreal carabids in the study plot on a given sampling date. Most richness values were greater than 173 species. Species accumulation curves attained asymptotes for all but one sampling date, indicating that an adequate level of sampling effort was used to characterize the diversity of carabid fauna. Total accumulation curves based on pooled data failed to reach asymptotes. There was a high turnover in species composition between sampling dates; less than 50 percent of the species between the majority of sampling dates were shared, suggesting that the total species pool may be extremely large. Although species composition changed seasonally, species richness varied little. Spatial autocorrelation analysis revealed that the structure of this species assemblage was significantly patterned at distances below 280 m. Taken together, the large percentage of undescribed species, die failure of the overall species accumulation curves to level off, and the high turnover in species composition indicate that the species diversity of carabid beetles is far higher than previously thought.     

The Structure of Ground Beetle Assemblages (Coleoptera: Carabidae) at Fruit Falls of Melastomataceae Trees in a Brazilian Terra Firme Rain Forest1

Although most Carabidae are recognized as predacious, recent studies have shown that some tropical rain forest Carabidae use the small seeds of fallen fruit from some tree species as a key food resource (particularly figs [Moraceae] but also those from other families). Assemblages of carabid beetles (Coleoptera: Carabidae) at fruit falls of the Melastomataceae tree genera, Bellucia, Loreya, and Miconia, were studied in a terra firme rain forest near Manaus (Amazonia, Brazil) from February 1992 to August 1996. Of 5483 specimens of 14 carabid species collected at 53 fruit falls, 98.2 percent of the collected beetles represented the seed-feeding genus Notiobia. Four of the 7 Notiobia species were found to reproduce at Melastomataceae fruit falls. The most abundant species, N. glabrata, was found to be a Melastomataceae seed generalise while N. maxima seemed to prefer the seeds of Bellucia, and N. aulica and Af. umbrifera the seeds of Miconia. The presence of larvae indicated reproduction of N. glabrata at fruit falls of all three tree genera and reproduction of N. maxima at those of Bellucia. Fruit falls of different species and genera of Melastomataceae appeared to occur at different times of die year and not continuously throughout the year. The seed-feeding Notiobia species, which specialize on Melastomataceae, used fruit falls of figs as migratory “stepping stones” during periods when there were no Melastomataceae fruit falls. The comparable suite of fig seed-feeding specialist species of Notiobia did not appear to do the reverse and seemed to avoid Melastomataceae fruit falls. The carabid assemblage at fig fruit falls was more diverse than the assemblage at those of Melastomataceae. Among the Melastomataceae, carabid species richness was highest at Miconia fruit falls and lowest at Loreya fruit falls. The three most common predatory species caught at Ficus fruit falls were also caught at those of Melastomataceae and appeared to reproduce at both fruit fall types. The proportion of the carabid assemblage accounted by predatory species was much lower at Melastomataceae (1.8%) than at fig fruit falls (8%).     

Flower Visitation by Bats in Cloud Forests of Western Ecuador1

The importance of bat pollination has been demonstrated for many plant species. Yet this mutualism has rarely been studied on a community–wide level. In this paper we present results of a yearlong study of a bat–flower community in cloud forests on the western slopes of the Ecuadoran Andes. Of eight plant–visiting bat species caught, only Anoura caudifera and A. geoffroyi were carrying pollen. These species of Anoura supplement their diets with insects. Unlike glossophagines in other environments, however, which switch completely to a frugivorous or insectivorous diet during certain seasons, they are nectarivorous year–round and were never found with seeds or fruit pulp in their feces. Of the 13 morphotypes of pollen carried by the bats, 11 were identified to genus and 7 to species. Floral characteristics of all of these plants fit the traditional chiropterophilous syndrome well. Our study represents the first direct evidence of bat pollination for those plants identified to species, including four species of Burmeistera (Campanulaceae), as well as the first record of bat pollination for a plant of the genus Meriania (Melastomataceae). While overlap in the diets of the two Anoura was high, significant differences in visitation frequencies to particular plant species were detected. The larger bat species (A. geoffroyi) preferred large flowers, whereas the smaller species (A. caudifera) preferred small flowers.     

Effects of Land Crabs on Leaf Litter Distributions and Accumulations in a Mainland Tropical Rain Forest1

The effect of the fossorial land crab Gecarcinus quadratus (Gecarcinidae) on patterns of accumulation and distribution of leaf litter was studied for two years in the coastal primary forests of Costa Rica's Corcovado National Park. Within this mainland forest, G, quadratus achieve densities up to 6 crabs/m² in populations extending along the Park's Pacific coastline and inland for ca 600 m. Crabs selectively forage for fallen leaf litter and relocate what they collect to burrow chambers that extend from 15 to 150 cm deep (N= 44), averaging (±SE) 48.9 ± 3.0 cm. Preference trials suggested that leaf choice by crabs may be species‐specific. Excavated crab burrows revealed maximum leaf collections of 11.75 g dry mass– 2.5 times more leaf litter than collected by square‐meter leaf fall traps over several seven‐day sampling periods. Additionally, experimental crab exclosures (25 m²) were established using a repeated measures randomized block design to test for changes in leaf litter as a function of reduced crab density. Exclosures accumulated significantly more (5.6 ± 3.9 times) leaf litter than did control treatments during the wet, but not the dry, seasons over this two‐year study. Such extensive litter relocation by land crabs may affect profiles of soil organic carbon, rooting, and seedling distributions.     

Seed Dispersal by the Sloth Bear (Melursus ursinus) in South India1

Previous studies have shown that sloth bears are mainly myrmecophagous, but in this study, 39 and 83 percent (wet and dry season, respectively) of scats surveyed in South India contained fruits. Seeds from three of six plant species collected from scats germinated faster than seeds not passing through bears; germination percentage was not higher in any of the six species. These results suggest that the sloth bear may play an important role in the population dynamics of fleshy‐fruited species of the region.     

Host Specialization among Wood-Decay Polypore Fungi in a Caribbean Mangrove Forest1

Host specialization in highly diverse tropical forests may be limited by the low local abundance of suitable hosts. To address whether or not fungi in a low‐diversity tropical forest were released from this restriction, fruiting bodies of polypore basidiomycete fungi were collected from three species of mangroves (Avicennia germinans, Laguncularia racemosa, and Rhizophora mangle) in a Caribbean mangrove forest in Panama. Unlike other tropical forests, the polypore assemblage in this mangrove forest was strongly dominated by a few host‐specialized species. Three fungal species, each with strong preference for a different mangrove host species, comprised 88 percent of all fungi collected.     

Ornithophilous and Chiropterophilous Pollination in Musa itinerans (Musaceae), a Pioneer Species in Tropical Rain Forests of Yunnan, Southwestern China1

The role of bats and sunbirds in the pollination ecology of Musa itinerans Cheesman (Musaceae) was studied in the tropical seasonal rain forests of Xishuangbanna, southern Yunnan, China. It was found that both long–tongued fruit bats (Macroglossus sobrinus) and sunbirds (Arachnothera longirostris) were effective pollinators of M. itinerans. Nectar production had two peaks, one during the day and one during night (0800–1200 h and 2000–2400 h), which allowed the two different foragers to visit at specific times. The visitation patterns of the two foragers coincided with both flowering time and nectar production. By measuring the differences in fruit weight and seed production among different bagging experiments, we found that birds and bats were equally effective as pollinators of this species.     

Tree Seed Fate in a Logged and Fragmented Forest Landscape, Northeastern Costa Rica1

We compared the seed fate of two animal‐dispersed, large‐seeded timber species (Dipteryx panamensis [Fabaceae] and Carapa guianensis [Meliaceae]) in logged and fragmented forests with that for continuous forest in northeastern Costa Rica. For both species, we quantified rates of seed removal (an index of vertebrate predation) and the fate of dispersed seeds (those carried away from their original location that either germinated or were not subsequently removed within three months). We predicted that (1) fewer seeds would be dispersed by vertebrates in fragmented forest than in continuous forest due to low population abundances after hunting and/or loss of suitable habitat, and (2) seed predation rates would be higher in forest fragments than in continuous forest due to high abundance of small‐bodied seed consumers. We compared three forest fragments currently managed for timber (140–350 ha) and a large reserve of continuous forest (La Selva, 1500 ha and connected to a national park). An exclusion experiment was performed (seeds placed in the open vs. seeds within semipermeable wire cages; 5 cm mesh size) to evaluate the relative roles of large and small animals on seed removal. Seed germination capacity did not differ among all four sites for both species. Removal of Dipteryx seeds was higher in forest fragments (50% removal within 10 days and related to the activity of small rodents) compared to La Selva (50% removal after 50 days). Also, more Dipteryx seeds were dispersed at La Selva than in fragmented forests. Contrary to our predictions, removal of Carapa seeds was equally high among all four sites, and there was a trend for more seeds of Carapa to be dispersed in fragments than in La Selva. Our results suggest that fragmentation effects on tree seed fate may be specific to species in question and contingent on the animal biota involved, and that management strategies for timber production based on regeneration from seed may differ between forest patches and extensive forests.