Showing papers in "Journal of Tropical Ecology in 2001"

Estimation of biomass in a neotropical forest of French Guiana: spatial and temporal variability

Abstract: Biomass content and turnover rate were estimated for a lowland wet rain forest in French Guiana. A regression model relating the biomass of a tree to its dbh (diameter at breast height) was deduced from previously published data. A power-law allometric relationship of the form AGTB = aD b was used to estimate the tree biomass, AGTB (Mg ha -1 ), from its dbh D (cm). Using direct measurements of tree biomass in the literature, the best-fit allometric exponent b = 2.42 (SD = 0.02) was found. The logarithm of the coefficient a was normally distributed with an aver- age of -2.00 (SD = 0.27). This method was applied to two permanent research sta- tions of the lowland tropical rain forest of French Guiana: the Nouragues and Piste de Saint-Elie. At the Nouragues, the biomass was estimated from trees 10 cm in dia- meter on two plots covering a total surface area of 22 ha and yielded an average bio- mass of 309 Mg ha -1 (± 32 Mg ha -1 , 95% confidence interval). Spatial variability was also addressed at the Nouragues by estimating the biomass of trees M 30 cm dbh over a total surface area of 82 ha. For the wet tropical forest vegetation type, an average of 284 Mg ha -1 was obtained (spatial variability ± 55 Mg ha -1 ). Biomass turnover was evaluated at Piste de Saint-Elie from two transects (0.78 and 1 ha) on which all trees M 5 cm in diameter were recorded and mapped twice in 10 y. Transect 1 showed a slight increase in biomass, from 245 to 260 Mg ha -1 (338 to 345 Mg ha -1 for transect 2), corresponding to a net increase of 1.9 Mg ha -1 y -1 (0.7 Mg ha -1 y -1 ), and the bio- mass ingrowth was 3.2 Mg ha -1 y -1 (2.8 Mg ha -1 y -1 ). These figures are discussed in the light of the natural recruitment dynamics of tropical forests.

Fruiting phenology and seed dispersal syndromes in caatinga, a tropical dry forest in the northeast of Brazil

Abstract: This study describes the fruiting phenology of woody plants and their dispersal syndromes in caatinga (semi-arid region in the northeast of Brazil). The fruiting phenology of 42 species with different dispersal modes and life-forms was followed over a period of 1 y. Animal dispersal was the most commonly observed dispersal mode (36%), followed by anemochory (33%), ballistic dispersal (19%) and barochory (12%). Overall, a greater number of species fruited during the rainy season. Zoochorous species were the most representative in the rainy season, whereas anemochorous species predominated during the dry season. Five different life-forms were observed, and the occurrence of dispersal modes was discussed for each of them. In the caatinga plant community studied the patterns of life-forms, fruiting phenology and seed dispersal syndromes were similar to other tropical seasonal ecosystems.Este trabalho teve como objetivo principal descrever como se comportam as especies de caatinga (regiao semi-arida do Nordeste brasileiro) com relacao ao modo de dispersao durante as estacoes seca e chuvosa. Foram observados tambem os modos de dispersao apresentados em cada forma de vida. A fenofase de frutificacao foi acompanhada em 10 individuos de 42 especies durante um intervalo de um ano. A zoocoria representou o modo de dispersao mais observado (36%), seguido da anemocoria (33%), balistica (19%) e barocoria (12%). Um maior numero de especies frutificou durante a estacao de chuvas, sendo a zoocoria mais representativa nesta estacao, enquanto que a anemocoria foi mais representativa na epoca de estiagem. Foram observadas varias formas de vida, discutindo-se o modo de dispersao em cada uma delas. Constatou-se que as especies de caatinga estudadas encontram-se dentro dos padroes gerais de epoca de dispersao dos diasporos e representatividade das sindromes de dispersao observados em outros ecossistemas com sazonalidade.

Vertical stratification of bat communities in primary forests of Central Amazon, Brazil

Abstract: The vertical stratification of bat communities in primary forests of the Central Amazon (80 km north of Manaus, Brazil) was investigated using capture nets in the canopy (17 to 30 m high) and in the understorey (from 0-2.5 m). Seventeen sites were sampled during one year (3398.5 mistnet-hours) and 936 individuals captured, belonging to 6 families, 29 genera and 51 species. Utilizing Non-Metric Multidimensional Scaling (NMMDS), a well-marked vertical stratification between the communities was verified, the canopy being the more utilized region. Fifteen species were exclusively captured in the canopy, 10 were predominantly captured in the canopy, and 12 species were exclus ively captured in ground nets. Species recorded and the communities they form were analysed using a matrix of guilds. The matrix obtained had 24 cells. A guild composed by background cluttered/gleaning frugivores was the richest in species (19), followed by background cluttered/gleaning insectivores (12 species). The results illustrate that when studying tropical forests it is highly desirable to involve both the lower and the upper part of the forests; otherwise the fauna would be merely subsampled, thus under-estimating the status and abundance of some species.

Diversity and distribution of lianas in a neotropical rain forest, Yasuní National Park, Ecuador

Abstract: Lianas (woody vines) contribute substantially to the diversity of woody plants in YasuniNational Park, Eastern Ecuador. In total 606 individuals, belonging to 138 species, were found in two 20-m × 100-m plots. The liana diversity was higher than in any comparable study, but the density was relatively low. Sapin- daceae and Leguminosae were the most species-rich families, whereas Legumino- sae and Celastraceae were the most abundant families. The number of liana indi- viduals as well as the number of liana species was partially explained by forest structure, but 92% of the variation in number of liana species depended on the number of liana individuals. Areas with high density of small trees had high liana density, and areas with a high number of tree saplings had a relatively high divers- ity of climbing lianas. The probability of trees being colonized by lianas increased with tree diameter. The presence of one liana on a tree increased its risk of being colonized by additional lianas.

A synthesis of the demography of African acacias

Abstract: Although acacias are ecologically and economically important, their demography is poorly known. In part this is because few field experiments have been undertaken. Also, a bewildering diversity of factors have been suggested to determine their demography. These factors include disease, fire, large and small browsers and grazers, climatic variation, competition with grass, seed predation and anthropogenic impacts. This synthesis concentrates on the life-history period from seed to adult plant and indicates that important hurdles have been demonstrated for some species in some habitats. Seed and seedling limitation have not been clearly demonstrated, nor has the value of dispersal been quantified. In contrast, the impacts of herbivores and fire in affecting the escape or release of resprouts has been repeatedly demonstrated. Whether fire and herbivory merely slow down the rate of promotion through size-classes or actually prevent it, needs further work. We note that very little comparative work amongst Acacia species has taken place. Most studies have concentrated on single aspects of their life history (especially seed predation), and have not been analysed in relation to population growth. Few field experiments, especially concerning seedling biology, have been performed. We conclude with some suggestions of a framework for interpreting acacia demography.

Evaluation of different methods to estimate understorey light conditions in tropical forests

Abstract: The suitability of several methods for estimating light conditions in the understorey of tropical forests, and of different sampling schedules was evalu- ated. Light conditions at 16 understorey sites in a Panamanian lowland forest were continuously measured for 9 mo with quantum sensors and photodiodes. Light conditions at the sites were also assessed indirectly with hemispherical fisheye photographs, plant canopy analysis, 38-mm photographs, 24-mm photographs and a spherical densiometer. Estimates from all indirect methods, except the spherical densiometer, were highly correlated with the direct measurements. Short-term direct light measurements for a day or a week also correlated with long-term light conditions. The indirect measures differed by up to c. 70% from the direct meas- ures relative to single site measurements. Hence, the indirect methods are inad- equate where single site light conditions have to be assessed accurately. However, because light conditions encountered in the understorey varied up to 13-fold, the indirect methods were found to be well suited to rank understorey light conditions among a large number of sites. The results from frequent and infrequent sampling schedules differed only slightly, suggesting that taking indirect measures at the beginning and the end of a study offers a reasonable compromise between accuracy and sampling effort.

Long-term tree ring chronologies from sympatric tropical dry-forest trees: individualistic responses to climatic variation

Abstract: The influence of local precipitation and temperature on long-term growth dynamics in two species of seasonally dry tropical forest trees were investig- ated. Growth records were extracted from tree rings in Guanacaste province, Costa Rica. These chronologies provide a long-term (c. 85-y) record of tree growth for two species with contrasting phenologies. Annual growth, in both species, was dependent on annual and/or monthly variation in local precipitation but less so on temperature. For each species, however, patterns of growth reflected unique degrees of sensitivity to monthly rainfall and rainfall during previous years. It is hypothesized that such differences were due to the rooting depth of these species. A review of the literature also indicated similar diverse cambial growth responses by tropical trees to variation in annual and monthly climate. Lastly, it was shown that variation in longer term fluctuations in the Pacific and Atlantic oceans, as measured by the El Nifio Southern Oscillation (ENSO) and North Atlantic Oscilla- tion (NAO), significantly influenced local precipitation in Guanacaste only during the wettest portion of the wet season. Such temporal sensitivity may have differen- tially influenced the longer-term growth of some tropical tree species but not others. Together, these results support the hypothesis that tropical tree species respond individualistically to variation in local and regional climate and that some tropical assemblages may in fact be structured by species-specific differences in soil water-use.

Patterns and correlates of interspecific variation in foliar insect herbivory and pathogen attack in Brazilian cerrado

Abstract: Patterns of insect herbivore and leaf pathogen attack are described for 25 plant species (10 trees, 10 shrubs and five herbs) at a Brazilian savanna (cerrado) site. Plant and leaf traits were correlated with interspecific variation in attack by herbivores and pathogens in order to account for differences among plant species. Across all species, pathogen damage was 1.5 times higher than insect damage (17.3% vs. 6.8%, respectively). Most insect damage occurred to young leaves while they were expanding (end of the dry season). In contrast, pathogen attack was low on young expanding leaves at the end of the dry season, increased as those leaves matured in the wet season, but continued to increase through the next dry season. Protein-binding capacity was negatively associated with interspecific differences in insect damage to mature leaves. Protein availability and plant height were positive predictors of pathogen attack among plant species, while leaf expansion rate was a significant negative predictor. Interspecific differences in leaf phenology had little effect on the amount of damage caused by either insects or pathogens. However, new leaves produced during the wet season suffered less insect damage than leaves produced during the dry season, the time of greatest leaf production. Timing of young leaf production affected pathogen attack but the season of escape depended on plant species. In contrast, there was no evidence for escape in space as common species were less likely to suffer high pathogen attack than rare species. New and mature leaf toughness, and time for a leaf to reach full expansion all increased from herbs to shrub to trees, while mature leaf nitrogen decreased in that order.

Effects of native pigs (Sus scrofa) on woody understorey vegetation in a Malaysian lowland rain forest.

Abstract: Large mammals often play important roles in determining the struc- ture and composition of plant communities. This study focused on the extent to which wild pigs (Sus scrofa) influence the dynamics of tree seedlings and saplings in a lowland rain forest at Pasoh Forest Reserve in West Malaysia. Native wild pigs are common in the study area and may significantly influence growth and survivorship of woody plants in the understorey through several activities - namely, nest building, soil rooting and seed predation. To test experimentally the impact of pigs on the plant community, eight 49-m 2 exclosures were constructed. After 2 y, the number of recruits inside exclosures was three times greater than in unfenced control plots. Stem density was highly correlated with species richness, which also increased significantly inside exclosures. Height growth of plants was greater in the exclosures by 52.5% for trees between 1 and 7 m tall. Trees less than 1 m tall, however, exhibited no differences in growth. Mortality of plants also did not differ between treatments. The observed differences between exclosure and control plots can be attributed to soil-rooting and seed predation, suggesting that these two behaviours of wild pigs are important to plant dynamics in the understorey.

Seed dispersal by a diurnal primate community in the Dja Reserve, Cameroon

Abstract: Multiple species of primate disperse seeds and differentially contrib- ute to the seed rain in tropical forests. The goal of this study was to examine seed dispersal by a primate community of five monkey and two ape species in the Dja Reserve, Cameroon. The density of primates in the reserve was calculated to be 77 individuals km −2 . Analysis of 5789 faecal clumps demonstrated that 40% of monkey and 74% of ape faecal clumps possessed whole seeds. Six of the seven focal species acted as seed dispersers; faecal clumps passed by the black-and-white colobus (Colobus guereza) did not contain any whole seeds during the study. Seed passage trials on four captive monkey species showed monkeys to have an average seed passage time of 22 hours and defecation rate of five times per day. From the above results, the primate community was estimated to defecate 1129 seeds km −2 d −1 . Seeds passed by the primate community came from 125 species of trees, lianas and shrubs, equivalent to at least 34% of the known tree flora. Rarefaction curves indicated that additional collection effort would identify more seed species passed by primates. Germination studies demonstrated that primate-passed seeds are viable. The number of seeds and plant species dispersed suggests that the primate community plays an important role in the maintenance of forest structure.

Effects of dung presence, dung amount and secondary dispersal by dung beetles on the fate of Micropholis guyanensis (Sapotaceae) seeds in Central Amazonia

Abstract: The study of seed fate is crucial for understanding fruit-frugivore interactions. One factor that can greatly influence the fate of seeds dispersed through mammal defecation, is the dung that accompanies the seeds. Dung attracts dung beetles and rodents; the former eat and bury dung, the latter feed on seeds. In this study the fate of Micropholis guyanensis subsp. guyanensis seeds surrounded by no dung and by 5, 10 and 25 g of howler monkey dung was followed until seedling establishment. The depths at which dung beetles bury the seeds were measured, and the effect of burial depth on seedling emergence was determined. Although initial seed fates differed among treatments, the same percentage of seedlings established from seeds without faecal material, and from seeds with 5, 10 and 25 g of dung. However, a significantly higher proportion of seedlings established from buried seeds when compared to seeds that remained on the surface. The percentage of seedlings establishing in a controlled germination experiment decreased significantly with increasing burial depth. The effect of dung beetle activity should be taken into consideration when assessing the role that mammal endozoochory plays on seed dispersal ecology of tropical plants. These results provide further evidence for the emerging realization that the study of secondary seed dispersal and post-dispersal events is crucial for a more complete understanding of plant regeneration.

Species composition and reproductive phenology of bats in a tropical landscape at Los Tuxtlas, Mexico

Abstract: The structure, composition and reproductive phenology of a bat assemblage were investigated in the tropical region of Los Tuxtlas, Mexico. A 90-km 2 landscape, originally occupied by rain forest, consisted of forest fragments and natural corridors of vegetation surrounded by pasturelands. Artificial strips of vegetation also were present as live fences. Bats were sampled with mist nets set at ground level in 52 forest fragments, three corridors, nine shaded plantations, six unshaded plantations and three live fences. We sampled each site twice, each time for a 5-h period for two consecutive nights. Bats were captured and released and the species identity and reproductive condition of adult females were recorded. Annual fruiting phenology and fruit production was measured with fruit traps in a forest site inthree 500 × 20-m transects. We captured 4799 bats of 39 species. At forest sites we recorded 97% of the species and captured 44% of the bats. In corridors we captured 76% of the species and 16% of the total individuals. In the plantations we captured 71% of the species and 32% of the individuals. In the live fences we captured 32% of the species and 8% of the individuals. Three species, Pteronotus parnelli, Carollia brevicauda and Glossophaga soricina, accounted for 52% of all bat captures. Fruit-eating species and fruit-eating insectivores accounted for 65% of captures. Fleshy fruits were available year-round, but a seasonal pattern was evident. Presence of lactating females seemed to be associated, in general, with rainfall and fruiting seasonality, but individual species displayed different patterns ranging from aseasonal polyoestry to seasonal bimodal polyoestry, sea- sonal polyoestry and seasonal monoestry. Despite extensive fragmentation of the original rain forest, a species-rich bat assemblage still exists in the landscape studied. Short distances among remaining forest fragments and man-made hab- itats seem to facilitate persistence and reproductive connectivity among members of this bat assemblage.

The insects of plant-held waters: a review and bibliography

Abstract: Phytotelmata habitats have been the focus of much research and are utilized by a wide variety of taxa. In the past 15 years numerous studies in many geographic regions and covering various types of phytotelmata have greatly increased our understanding of these unique habitats. The most recent summary of phytotelmata inhabitants included over 20 families of insects. A review of the literature and extensive work in lowland Ecuador shows the family level diversity is in fact at least twice that reported earlier. A reassessment of previous phytotelmata classification schemes, as well as an extensive bibliography, is provided.

The effects of altitude and rainfall on the composition of the termites (Isoptera) of the Leuser Ecosystem (Sumatra, Indonesia)

Abstract: In 1998 a survey was made of the termites of the Leuser Ecosystem (in Sumatra, Indonesia), which includes a substantial area (c. 1 million ha) of unbroken primary rain forest. Nine sites and an altitudinal gradient were sampled. Altitude had a significant effect on species richness, which declines with even a 100-m increase in altitude. Species composition too was significantly affected by altitude. Functionally, only termites in one feeding group (II, which forage outside of their nests) were significantly affected by altitude. A mid-altitude termite spe- cies assemblage was evident. Longitude also significantly affected species composi- tion; Macrotermitinae were numerous on the western side of the Ecosystem and Termitinae and Nasutitermitinae more numerous to the east of it. This was prob- ably due to differences in rainfall patterns across the Ecosystem.

Environmental heterogeneity, recruitment limitation and the mesoscale distribution of palms in a tropical montane rain forest (Maquipucuna, Ecuador)

Abstract: The study presented here investigated the importance of environmental heterogeneity and clumping for the mesoscale distribution patterns of five palm species in old-growth Andean forest (Maquipucuna, Ecuador). Seedlings, juveniles and adults were recorded in 167 plots located throughout the 3-km × 3-km study area. Mountain (Cerro Sosa or Cerro Sta. Lucia), altitude, aspect, topographic-edaphic conditions and forest structure were also recorded. The following questions were investigated: (1) Are the distributions related to environmental heterogeneity? (2) Are the distribution patterns consistent with severe recruitment limitation? The distribution patterns of four species were related to environmental heterogeneity, especially to that created by the mountainous landscape itself, and at least four of the five species also exhibited strong clumping that was clearly linked to spatially restricted recruitment and could not be explained by the environmental parameters. Thus, both niche specialization and recruitment limitation probably play important roles in Andean palm community ecology. Consistent differences among the two mountains in forest structure and the frequency of certain palm stages most likely reflected extractivism.

Effects of a Strong Drought on Amazonian Forest Fragments and Edges

Abstract: Little is known about how climatic variability affects fragmented forests and their abrupt edges. We contrasted effects of the 1997 El Nino drought between fragmented and continuous forests in central Amazonia, using long-term data on tree mortality. For 23 permanent 1-ha plots, annualized mortality rates of trees 10 cm diameter at breast height (dbh) were compared among a 'baseline' interval of 5-17 y before the drought, a 12-16-month interval during the drought, and a 12-13-month interval after the drought, using repeated-measures ANOVA. We also examined the size distributions of dead trees for each interval. During the drought, average annual tree mortality rose significantly in both forest edges (from 2.44% to 2.93%) and interiors (from 1.13% to 1.91%), and the magnitude of this increase did not differ significantly between edges and interiors. After the drought, tree mortality declined inall plots, but most dramatically onedges. Mor- tality rates were more variable over time onedges thanin teriors, an d there was no evidence of time lags in mortality. In forest interiors, the size distributions of trees that died did not differ significantly among the three intervals. On edges, however, relatively fewer small (10-15 cm dbh) and more medium-sized (20-30 cm dbh) trees died in the post-drought interval, compared to other intervals. More- over, forest edges lost a significantly higher proportion of large ( 60 cm dbh) trees thandid forest in teriors. These results suggest that droughts have relatively complex effects onfragmen ted Amazon ianforests. Drought effects inour forest fragments probably were reduced by prior floristic and structural changes near edges and by adjoining regrowth forest that partially buffered edge vegetation from desiccating conditions. 1

Avian predation upon lizards and frogs in a neotropical forest understorey

Abstract: Although tropical forest birds are known to prey upon small lizards and frogs, no study has documented the attributes of vertebrate-eating birds or whether birds prey opportunistically on the different elements of the herpetofauna within tropical communities. This study is based on a 14-mo investigation on avian diet, supplemented with a 3-y census of frogs and a 1-y census of lizards in a humid forest of central Panama. From 91 bird species, 1086 regurgitates were collected, in which were found 75 lizards and 53 frogs. Over 50% of the common, primarily insectivorous bird species preyed upon lizards or frogs, with a mean frequency of 0.26 prey/sample. These birds (22 species, nine families) foraged on various substrates from different strata of the forest, fed on invertebrates averaging from 3.3 to 17.2 mm in length, weighed from 11 to 195 g, and had bill lengths that varied from 12.2 to 49.8 mm. Based on a logistic regression analysis, intensity of foraging at army-ant swarms was the variable that best explained the likelihood that a bird species preyed upon lizards, leading to a classification that was 91% correct. In contrast, bill length and body length classified correctly 88% of the frog-eating birds, which showed a fairly constant 1:7 bill length/body length ratio (as opposed to a mean but highly variable 1:10 ratio in other species). A multiple regression analysis showed that seasonal variation in intensity of lizard predation was positively related to arthropod abundance except during the breeding season when lizard intake decreased, presumably because nesting birds did not follow ant swarms. Intensity of frog predation correlated with frog abundance over time, the latter being inversely related to arthropod availability. Ninety-seven per cent of all lizards and frogs identified in the diet samples (n = 105) were from two genera, Anolis and Eleutherodactylus, respectively. Prey size distribution in the regurgitates suggested an optimal prey size of 33.5 mm snout-vent length (SVL) for lizards and 14.5 mm SVL for frogs. Birds preyed opportunistically on the different Anolis species, but almost exclusively upon juvenile individuals. Abundances of the different Eleutherodactylus species correlated with their predation rates, but these frogs represented only 10% of all the frogs observed during the censuses. The two most common local anurans, Colostethus flotator and Bufo typhonius, were not taken by any bird species.

Seed scatterhoarding by white-tailed rats: consequences for seedling recruitment by an Australian rain forest tree

Abstract: The role of white-tailed rats (Uromys caudimaculatus) as dispersers of seeds of the Australian tropical rain forest tree Beilschmiedia bancroftii, (Lauraceae) was investigated by following the fates of seeds and seedlings over 2 y. Fruits of this tree are too large to be consumed by any avian frugivore except the southern cassowary (Casuarius casuarius), and the only other native mammal capable of dispersing the seeds is the musky rat kangaroo (Hypsiprimnodon moschatus). However, neither of these species has been documented to disperse the seeds of this tree. During a mast year, white-tailed rats cached seeds an average of 13 m from parent trees in a variety of microsites. Although none of the 61 cached seeds followed in this study survived to germination, comparison of seed, cache and seedling distributions suggested that most seedlings arose from rat-cached seeds. White-tailed rats cached seeds in both mast and non-mast years, but the time seeds remained on the forest floor and in caches was significantly shorter in non-mast years, suggesting that synchronous seed production increases the probability that some caches survive to germination. Because white-tailed rats are the most common and widespread native mammal capable of dispersing large-seeds, this study suggests that they may play an important role in the seed and seedling dynamics of large-seeded tree species in Australian tropical rain forests.

Effects of weather and phenology on the abundance and diversity of geometroid moths in a natural Malaysian tropical rain forest

Abstract: Geometroid moth abundance, species richness, weather and plant phenology were monitored monthly for 3 y in the lowland dipterocarp forest at Pasoh Forest Reserve, Negeri Sembilan in Malaysia. The intensity of tree flowering in the previous month (with mass events triggered in response to El Nifno Southern Oscillations) was an important environmental factor positively correlated with the numbers of species and individuals of geometroid moths that emerge in any month. Abundance for geometroid moths was greater in months with high flower- ing and flushing in the previous month but low flowering in the month before that. Important weather parameters that influenced moth abundance were monthly rainfall, relative humidity and minimum temperature in previous months. High rainfall 3 mo previously led to an increase in moth abundance (perhaps by stimu- lating an increase in fresh plant material), whereas high rainfall and relatiye humidity thereafter served to decrease abundance, possibly by encouraging the spread and activity of pathogens: all these factors impacted on early life-stage survivorship. Similar trends were observed for individual geometroid families and subfamilies. The diversity measurement for the geometroid moths, a from the log-series, was correlated more with weather parameters than with tree phenology.

The bat fauna of Lamanai, Belize: roosts and trophic roles

Abstract: Thirty-six of the 70 species of bats known from Belize were recorded from the area around Lamanai, Orange Walk County: two in roosts and 34 in about 680 mist net hours that produced 560 captures Day roosts used by 35 of the species were located using radio-tracking (Sturnira lilium, Platyrrhinus helleri, Centurio senex and Bauerus dubiaquercus) or general searching for roosts (Rhynchonycteris naso, Saccopteryx bilineata, Saccopteryx leptura, Dicli durus albus, Mimon bennettii, Micronycteris schmidtorum, Carollia brevicauda, Carollia perspicillata and Eptesicus furinalis) Data on the day roosts of 23 other species were determined from the literature Most species reported from Lamanai (19) roosted in hollows, while others used foliage (6), tents (3), sheltered sites (2), crevices (2), open sites (1), and a few species used more than one type of day roost (hollows and crevices (1); hollows and foliage (1); hollows, foliage and tents (1)) The fauna consisted of 13 aerial foragers, 9 gleaners, 11 fruit/leaf eaters, one trawler, one flower-visitor and one blood-feeder In day roost use and foraging behaviour, the Lamanai fauna did not differ significantly from that of Paracou, French Guiana, but both these locations differed from the bat fauna of Kruger National Park, South Africa, in foraging behaviour

Bat community structure at Iwokrama Forest, Guyana

Abstract: With 86 species, Iwokrama Forest in central Guyana has the highest reported bat biodiversity for a protected area in the world. Using standardized capture data for 73 of these 86 species, we document community structure of bats in terms of species diversity, relative abundance, gross biomass, feeding guilds, vertical stratification and a trophic-size niche matrix. Based on faunal surveys in 1997, with similar amounts of effort in the forest canopy and at ground level, the greater fruit-eating bat (Artibeus lituratus) was by far the most ecologically dominant species in terms of frequency of capture and biomass. In total, frugivores comprised 70% of the species diversity and 78% of the biomass. The most common species of bat were fully partitioned in a resource niche matrix of size and trophic guild when vertical stratification was included as a variable. We conclude that resource partitioning and species packing differentially affect relative size in tropical bats, and are better summarized and analysed in three dimensions.

The densest terrestrial vertebrate

Abstract: An understanding of the abundance of organisms is central to understanding ecology, but many population density estimates are unrepresentative because they were obtained from study areas chosen for the high abundance of the target species. For example, from a pool of 1072 lizard density estimates that we compiled from the literature, we sampled 303 estimates and scored each for its assessment of the degree to which the study site was representative. Less than half (45%) indicated that the study area was chosen to be representative of the population or habitat. An additional 15% reported that individual plots or transects were chosen randomly, but this often indicated only that the sample points were located randomly within a study area chosen for its high abundance of the target species. The remainder of the studies either gave no information or specified that the study area was chosen because the focal species was locally abundant.

Population dynamics of the marsupial Micoureus demerarae in small fragments of Atlantic Coastal Forest in Brazil

Abstract: Patterns of population fluctuation, reproductive activity and age structure were studied in populations of the marsupial Micoureus demerarae occupy- ing two small (7.0 and 8.8 ha) fragments of Atlantic Coastal Forest in southeastern Brazil, from 1995 to 1998. Males, but not females, were observed to move between populations. Estimated sizes of the populations in each fragment were very small, usually below 20 individuals. Breeding usually occurred from September to April. Population peaks came mostly by the end of this season, the delay reflecting the time required for the young to become trappable. In August 1997, the area was hit by a fire severely affecting the smaller fragment. Populations were synchronous before the fire, although they became asynchronous after it, possibly in the short term only. Small population sizes, synchrony and presumable male-biased migra- tion are all likely to make the set of populations more vulnerable to extinction than expected for a metapopulation.

Agreement between floristic and soil organic carbon isotope (13C/12C, 14C) indicators of forest invasion of savannas during the last century in Cameroon.

Abstract: In an area of savanna-forest (S-F) mosaic of Cameroon, at Kandara near Bertoua, an enclosed savanna bordered by young semi-deciduous forests was selected for detailed studies of vegetation and soil carbon isotope compositions with a view to estimating the rate of forest advance into savannas. Forest floristic composition and structure were analysed in small plots along two S-F transects and within two large stands. Tree species counts and basal area (BA) measurements gave convergent results defining (1) an edge forest with low BA values that forms an irregular strip parallel to the S-F border, (2) a large colonization zone zone composed of pioneer species (Albizia species, with individuals of very large diameter) and (3) a mature forest composed of abundant Rinorea individuals and large individuals of Triplochiton scleroxylon and Piptadeniastrum africanum. Carbon stable isotopes were deter mined from organic matter of soil profiles sampled at various depths in savanna, colonization-zone and mature forest. In the deep soil horizons (40-50 cm) of the colonization-zone profiles, [delta]13C values similar to those of the present savanna reveal the past existence of a large-tree savanna. In subsurface horizons (15-20 cm), [delta]13C values intermediate between those of savanna and mature forest prove the encroachment of the forest ecosystem on savanna. Using 14C measurements, the mean residence time (MRT) of soil organic matter of these last horizons was determined with precision owing to the atmospheric 14C pulse from nuclear bomb tests prior to 1964. By assuming an exponential age distribution of organic compounds and by taking account of MRT and remaining carbon from the savanna, the coloniza tion zone was found to be 60-80 y old. The age of the colonization zone being the same near the present savanna and near the mature forest, it seems that the forest advance was probably not a linear process but would result from the coalescence of Albizia thickets born in savanna.

Pollination in a degraded tropical landscape: a Hong Kong case study

Abstract: Although the pollination biology of many individual plant species has been investigated in the Oriental region, there have been very few community-level studies. The two most comprehensive of these were in the primary mixed dipterocarp forest of Lambir Hills National Park, Sarawak (4°20′N: Momose et al. 1998, Sakai et al. 1999) and in the warm temperate evergreen broad-leaved forest and cool temperate mixed forest on Yakushima Island (30°N: Yumoto 1987, 1988). Hong Kong (22°17′N) lies midway between these sites, at the northern margin of the tropics, where winter temperatures fall below 10 °C at sea-level for a few days every year and there are occasional frosts above 400 m (Dudgeon & Corlett 1994). Latitudinal effects, however, are compounded in comparisons with other well-studied East Asian sites, by centuries of massive human impact, leaving a degraded landscape of steep, eroded hillsides, covered in fire-maintained grassland, secondary shrublands and, locally, secondary forests (Zhuang & Corlett 1997). This history has left a relatively impoverished fauna but a surprisingly diverse flora, including 400 native tree species (Corlett & Turner 1997). In these circumstances, failures of pollination and dispersal mutualisms might be expected to accelerate the loss of plant species from the landscape (Bond 1994, Kearns & Inouye 1997). Previous studies have shown that most woody vegetation in Hong Kong is dominated by species whose seeds can be dispersed by the commonest avian frugivores, the light-vented and red-whiskered bulbuls (Pycnonotus sinensis (Gmelin) and P. jocosus (Linn.)) and the Japanese white-eye (Zosterops japonicus Swinhoe) (Corlett 1996, 1998), but there is no equivalent information available on pollination biology.

The fragility of extreme specialization: Passiflora mixta and its pollinating hummingbird Ensifera ensifera

Abstract: Some of the most spectacular examples of coevolution between flowers and their pollinators are reflected in their morphologies. Tongue length of insects and bill lengths of nectar-feeding birds are some of the most significant characters in pollination studies (Kearns & Inouye 1993). As Darwin noted as early as 1862, the evolution of deep floral tubes or spurs and long tongues of flower visitors can be explained by runaway coevolution (Nilsson 1988). However, such a process has only been shown to be likely in a few cases, e.g. between Malagasy orchids and hawkmoths (Nilsson et al. 1985). The pollinator of the Malagasy orchid Angraecum sesquipedale, with a 30 cm nectar spur, is a sphingid moth with a tongue of a similar size (Darwin 1862, Nilsson 1998). However, most studies of such extreme pollination specialization also report that the interaction is asymmetrical, i.e. the pollinators interact with a guild of plants, whereas the plant often depends on only a few pollinators (Johnson & Steiner 1995).

Fruiting phenology of fleshy-fruited plants and seasonal dynamics of frugivorous birds in four vegetation zones on Mt. Kinabalu, Borneo

Abstract: An altitudinal survey of correspondences between fruiting phenologies of fleshy-fruited tree species and seasonal dynamics of frugivorous birds on Mt. Kinabalu in Borneo was carried out for 50 weeks across four vegetation types: a hill forest (800 m asl), a lower montane forest (1700 m), an upper montane forest (2000-3000 m) and a subalpine forest (3000-3500 m). In the hill forest, a large fruiting peak following the general flowering phenomenon was observed during October-November in 1996 and a fruitless period was observed during February-April in 1997. During the fruitless period, the number of resident frugivorous birds decreased. A bimodal fruiting pattern was observed in the lower montane forest. A large number of frugivorous temperate migrants were observed when the fruiting peak occurred. The number of resident frugivorous birds increased and several lowland bird species were observed, when the number of resident birds decreased in the hill forest. In the upper montane forest and the subalpine forest, more continuous and irregular fruiting patterns without outstanding peaks were observed and the number of resident frugivorous birds was more stable throughout the year. These suggested (1) there was a strong relationship between fruiting seasonality and seasonal dynamics of temperate migrants in the lower montane forest; (2) seasonal altitudinal movements of lowland bird species to montane vegetation might occur during the fruitless period in the lowland forest; and (3) the continuous fruiting pattern in the higher vegetation zones might be related to the scarcity of available frugivorous birds. The hypothesis that the influx of temperate migrants into the montane vegetation of Mt. Kinabalu is affected by density and habits of resident frugivorous birds is supported. Montane vegetation in Borneo plays an important role as temporal refugia for temperate and altitudinal migrants by supplying fruit resources.

Insular interactions between lizards and flowers: flower visitation by an endemic Mauritian gecko

Abstract: Lizards mainly eat arthropods, fruit, nectar, pollen and animal scats (Perez-Mellado & Casas 1997, Whitaker 1987), using their sense of smell and good colour vision while foraging (Vinson & Vinson 1969). Although several papers have contributed to the knowledge on the relationship between lizards and floral resources, this topic is often still regarded as anecdotal. However, a few detailed ecological studies on lizard and flower interactions have been conducted, e.g. in New Zealand and the Balearic Isles (Eifler 1995, Saez & Traveset 1995, Traveset & Saez 1997,Whitaker 1987). Pollination by lizards was rendered likely by the following findings: first, Mediterranean lacertid lizards and New Zealand geckos have pollen adhering to their belly, throat and labium; second, they may carry pollen for several hours, and thus also transport pollen some distance away from a pollen donor plant. New Zealand geckos carry pollen up to 72 m away from donors. Good experimental evidence of lizard pollination was produced by Perez-Mellado & Casas (1997). They showed that an umbellifer species produced less viable seeds if Podarcis lilfordi lizards were excluded from flowers.

Diversity of poroid and some corticoid wood-inhabiting fungi along the rainfall gradient in tropical forests, Costa Rica

Abstract: The influence of a rainfall gradient on the distribution and species richness of some groups of wood-inhabiting basidiomycetes was explored in Costa Rican tropical forests. The relationships between these fungi and wood size and decay stage were also studied. Basidiocarps of all poroid and some corticoid fungi were recorded in three plots of 30 logs in each of dry, moist, and wet forests. The logs were surveyed three times during one year, covering all seasons. The species richness gradient was inversely related to the rainfall gradient, with most species in the dry forest (51), least in the wet forest (37), and intermediate in the moist forest (44). A total of 102 species were identified. Only six species occurred at all three sites. Two of the four most common species were new to science. The com- position of wood-inhabiting fungal species in the dry forest varied from both the moist and the wet forest, while species composition in the two latter forest types was difficult to distinguish. Both frequent and rare species utilized the different decay stages as expected from availability of substrate. Perennials and rare species tended to occur on large logs in the dry forest, while all species tended to occur on large logs in the moist forest, but not in the wet forest.

Growth and photosynthesis of seedlings of four tree species from a dry tropical afromontane forest

Abstract: Growth, photosynthesis and carbon allocation pattern were studied in four dry afromontane forest tree species (Olea europea subspecies cuspidata, Podo- carpusfalcatus, Hagenia abyssinica andJuniperus procera) under varied light regimes in a greenhouse. The objective of the study was to assess the potential of the species for growth under forest canopies and to identify their habitat preferences. The light regimes were created using shade cloth and they corresponded with deep forest understoreys (2% of the light in the open gap); moderate shade (10%), slight shade as is found in edges of forest gaps (20%) and 100% representing open gaps. Seedling biomass was significantly influenced by light regimes for all species as were total leaf area and relative growth rate. H. abyssinica had the highest growth rate but the lowest survival rate in shade. There was a consistent trend for higher specific leaf area (SLA) and leaf area ratio (LAR) at lower growth light regimes in 0. europea and P.falcatus. 0. europea and P.falcatus had similar allocation patterns whereby between 20-40% of the total biomass was allocated to stem, 20-30% to roots and 50-60% to leaves. In H. abyssinica up to 80% was allocated to leaves and only a small percentage to stem and to roots. Within species there were significant differences in the light saturated rate of photosynthesis (Amax) per unit area among the plants grown at the lowest light level and in the open. For plants grown in the open there were very little among species differences in Amax per unit area. However, there were significant differ- ences in the Amax of the different species grown at the lowest light level. Chloro- phyll fluorescence measurements indicated that open-grown P. falcatus and 0. europea experienced moderate photoinhibition. From the growth and photosyn- thesis results P. falcatus and 0. europea appeared to be non-pioneer, shade-tolerant species, whileJ. procera and to a larger extent H. abyssinica showed pioneer, light- demanding characteristics. The results are discussed in terms of the occurrence of the species in the mosaic climaxes of afromontane forests.