bluuebunny/crossref_metadata_2025 huggingface dataset:
Responses of Aquatic Macrophytes to Disturbance by Flash Floods in a Brazilian Semiarid Intermittent Stream1
Authors: Maltchik Leonardo , Pedro Fabio
Published: March 2006

Resistance and resilience of Najas marina to disturbance by flash floods were studied in a permanent fluvial pool of a Brazilian semiarid intermittent stream. A total of 21 macrophyte samples was collected in the high‐rainfall season during two annual cycles (1996–1997). Decreases in macrophyte biomass were positively correlated with flood magnitude (Pearson, P = 0.047), varying from 25 to 53 percent when discharges were lower than or equal to 0.5 m3/ sec and between 70 and 100 percent when discharges were higher than 1.0 m‐3/sec. Macrophyte resilience was greater after floods of low magnitude. After floods of 0.5 m‐3/sec, three weeks were necessary to re‐establish 88 percent of biomass lost, and after a flood of 1.4 m‐Vsec, six months were needed to initiate A, marina regrowth. This population of N. marina in Avelós stream has higher stability in response to small disturbances, but as expected, its resistance and resilience decreases with larger disturbances. In general, the high resistance and resilience of N. marina m response to small disturbances have been observed in intermittent tropical streams. The absence of large floods during the study period and the low variability of water temperature in this tropical region may have influenced these results.

RESUMES

A influencia de cheias rápidas na resistência e na resistência de Najas marina foram estudadas em uma poça fluvial permanente de um riacho efêmero do Semi‐árido Brasileiro. Vinte e uma coletas de macrófitas aquáticas foram realizadas durante o período de chuvas de dois ciclos anuais (1996 e 1997). A variaçäo da biomassa de macrófitas aquáticas estava diretamente correlacionada com a magnitude da cheia (Pearson, P=0.047), variando entre 25 e 53 por cento quando as vazöes eram inferiores ou iguais à 0.5 m3‐Vsec e entre 70 e 100 por cento quando as vazöes eram superiores à 1.0 m3/sec. A resiliência de macrófitas era maior após às cheias de baixa magnitude. Após a cheia de 0.5 m3‐Vsec, foram necessários seis meses para restabelecer 88 por cento da biomassa perdida, e após a cheia de 1.4 m3/ sec, foram necessáries seis meses para iniciar a resiliência de Najas marina. Esta populaçäo de N. marina do riacho Avelós apresentou maior estabilidade frente ás perturbaçöes hidrológicas de baixa magnitude, mas a resistêncía e a resiliéncia diminuíam à medida que a magnitude da perturbaçao aumentava. A alta resístência e resiliência de N marina frente às perturbaçöes hidrológicas de baixa magnitude, geralmente tem sido observadas em riachos intermi‐tentes tropicais. A ausência de grandes cheias durante o periodo estudado e a pequena amplitude térmica da água superficial desta regiäo tropical podem ter favorecido estes resultados.
The Role of Arboreal Seed Dispersal Groups on the Seed Rain of a Lowland Tropical Forest1
Authors: Clark C. J. , Poulsen J. R. , Parker V. T.
Published: March 2006

Most tropical plants produce fleshy fruits that are dispersed primarily by vertebrate frugivores. Behavioral disparities among vertebrate seed dispersers could influence patterns of seed distribution and thus forest structure. This study investigated the relative importance of arboreal seed dispersers and seed predators on the initial stage of forest organization–seed deposition. We asked the following questions: (1) To what degree do arboreal seed dispersers influence the species richness and abundance of the seed rain? and (2) Based on the plant species and strata of the forest for which they provide dispersal services, do arboreal seed dispersers represent similar or distinct functional groups? To answer these questions, seed rain was sampled for 12 months in the Dja Reserve, Cameroon. Seed traps representing five percent of the crown area were erected below the canopies of 90 trees belonging to nine focal tree species: 3 dispersed by monkeys, 3 dispersed by large frugivorous birds, and 3 wind‐dispersed species. Seeds disseminated by arboreal seed dispersers accounted for ca 12 percent of the seeds and 68 percent of the seed species identified in seed traps. Monkeys dispersed more than twice the number of seed species than large frugivorous birds, but birds dispersed more individual seeds. We identified two distinct functional dispersal groups, one composed of large frugivorous birds and one composed of monkeys, drop dispersers, and seed predators. These groups dispersed plants found in different canopy strata and exhibited low overlap in the seed species they disseminated. We conclude it is unlikely that seed dispersal services provided by monkeys could be compensated for by frugivorous birds in the event of their extirpation from Afrotropical forests.
Ants Induce Domatia in a Rain Forest Tree (Vochysia vismiaefolia)1
Authors: Blüthgen Nico , Wesenberg Jens
Published: March 2006

In Amazonian rain forest trees of Vochysia vismiaefolia (Vochysiaceae), ants were found to induce twig structures that resembled classical ant domatia. This phenomenon is novel for ant‐plants, which commonly develop domatia without the activity of ants. Eight species of ants were recorded inside the domatia of six individual trees, but domatia were most numerous and characteristic when induced and inhabited by an undescribed species of Pseudomyrmex on two trees. To investigate the mechanism of domatium growth, we drilled holes into young twigs: the expansion of the twig diameter surrounding the holes was significantly accelerated, comparable to domatia formation. Domatia induction is discussed as a putative step in the evolution of ant‐plants.
Hyper‐abundance of Native Wild Pigs (Sus scrofa) in a Lowland Dipterocarp Rain Forest of Peninsular Malaysia1
Authors: Ickes Kalan
Published: March 2006

This study reports extraordinarily high density estimates for the wild pig (Sus scrofa) from an aseasonal tropical forest site within the species'native range. At Pasoh Forest Reserve, a 2500 ha area of lowland dipterocarp rain forest in Peninsular Malaysia, line transects were used to estimate pig density from May to October in 1996 and 1998. In 1996, 44 sightings of S. scrofa consisting of 166 individuals were recorded along 81 km of transects. In 1998, 39 sightings documented 129 individuals along 79.9 km of transects. Estimated population density was 47.0 pigs/km2 in 1996 and 27.0 pigs/km2‐ in 1998. Sus scrofa biomass in this forest was estimated at 1837 kg/km2 and 1346 kg/ km2 in 1996 and 1998, respectively. Differences between years were attributed to changes in the density of young pigs, coincident with a mast‐seeding year of dipterocarp trees in 1996. Pig densities at Pasoh Forest Reserve were much higher than at other forest locations within the species' native range in Europe and Asia. Because Pasoh Forest Reserve is a forest fragment, two factors likely account for the extremely high pig densities: (1) local extinction of natural predators (mainly tigers and leopards) and (2) an abundant year‐round food supply of African oil palm fruits from extensive plantations bordering the reserve.
Past Vegetation Changes in Amazon Savannas Determined Using Carbon Isotopes of Soil Organic Matter1
Authors: Sanaiotti T. M. , Martinelli L. A. , Victoria R. L. , Trumbore S. E. , Camargo P. B.
Published: March 2006

We investigated the variation of stable (813C) soil carbon isotopes in relation to depth in seven of the most important savanna areas to adjacent contiguous forests in the Amazon region. The 813C of bulk organic matter in all profiles from forested sites increased with soil depth. In forest profiles from Amapá, Alter do Chão, and Roraima, the enrichment was less than 3.5%o between deeper soil and surface layers, suggesting that 03 plants have remained the dominant vegetation cover. On the other hand, in forest soil profiles from Humaitá and Carolina sites, the 813C enrichment was greater than 3.5%o, indicating the influence of past 04 vegetation or a mixture of C3/C4 vegetation (woody savanna). The surface 813C values in the savanna profiles were 5–13%o greater than the comparable forest profiles, indicating the influence of C4 vegetation. Two kinds of isotopic distribution were observed in deeper layers. The savanna profiles at Alter do Chão, Chapada dos Parcels, and Redenção had relatively constant 813C values throughout the profile, suggesting minor past changes in the vegetation composition. In profiles at Amapá, Roraima, Humaitá, and Carolina, 813C values decreased with depth from the surface and converged with comparable forest values, suggesting more woody savanna in the past than exists currently.

Nós investigamos neste estudo a variação em profundidade dos isótopos estáveis de carbono (δ13C) da matéria organica do solo (SOM) em sete áreas de savanas e florestas da região Amazo̧nica. Os valores de δ13C da SOM aumentaram com a profundidade do solo. Nos perfis em floresta do Amapá, Alter do Chão e Roraima o enriquecimento isotópico com a profundidade foi menor que 3,5%0, sugerindo que plantas do tipo C3 foram sempre o tipo de vegetação dominante. Por outro lado, nos perfis em floresta de Humaitá e Carolina, o enriquecimento isotópico foi maior que 3,5%o, indicando a influ○ncia no passado de uma vegetação do tipo 04, ou uma mistura de vegetação C3/C4 (savana lenhosa). Os valores de δ13C na superflcie do solo em savanas fbram cerca de 5 a 13%o maiores que os perfis em floresta, evidenciando a influ○ncia da vegetação C4. Dois tipos de distribuição isotópica foram observados em camadas mais profundas. Nas savanas de Alter do Chão, Chapada dos Parecis e Redenção os valores δ13C foram constantes ao longo do perfil do solo, sugerindo que não houveram mudanças significativas na vegetação. Nos perfis do Amapá, Roraima, Humaitá e Carolina, os valores de δ13C diminuiram com a profundidade do solo, aproximando‐se aos valores encontrados na floresta, sugerindo a exist○ncia no passado de uma savana mais lenhosa que a actual.
Modification of Vegetative Phenology in a Tropical Semi‐deciduous Forest by Abnormal Drought and Rain1
Authors: Borchert R. , Rivera G. , Hagnauer W.
Published: March 2006

The control of vegetative phenology in tropical trees is not well understood. In dry forest trees, leaf abscission may be enhanced by advanced leaf age, increasing water stress, or declining photoperiod. Normally, it is impossible to dissect the effects of each of these variables because most leaves are shed during the early dry season when day length is near its minimum and leaves are relatively old. The 1997 El‐Niño Southern Oscillation caused a ten‐week long, severe abnormal drought from June to August in the semi‐deciduous forests of Guanacaste, Costa Rica. We monitored the effect of this drought on phenology and water status of trees with young leaves and compared modifications of phenology in trees of different functional types with the pattern observed during the regular dry season. Although deciduous trees at dry sites were severely water stressed (Ψstem < ‐7MPa) and their mesic leaves remained wilted for more than two months, these and all other trees retained all leaves during the abnormal drought. Many trees exchanged leaves three to four months earlier than normal during the wet period after the abnormal drought and shed leaves again during the regular dry season. Irrigation and an exceptional 70 mm rainfall during the mid‐dry season 1998/1999 caused bud break and flushing in all leafless trees except dormant stem succulents. The complex interactions between leaf age and water stress, the principal determinants of leaf abscission, were found to vary widely among trees of different functional types.
The Reproductive Biology and Reproductive Success of Pterocarpus macrocarpus Kurz1
Authors: Doungyotha Yupa , Owens John N.
Published: March 2006

The reproductive biology of Pterocarpus macrocarpus Kurz (pradu) was studied in 37‐year‐old plantation trees in Thailand to determine the causes of seed and fruit loss. Trees flowered at the end of March or early in April at the end of the hot dry season and start of the rainy season. Flowering occurred over about a one‐month period. Fruits developed over the next six months during the rainy season and matured at the start of the cool dry season in October and November. Phenology was similar in the four trees that were studied in detail. Racemes averaged 30 flowers each and each raceme was receptive for several days, although each flower was only receptive for one day. After pollination, floral parts were shed over several days and fruits began to develop. Pradu is entomopholous but its insect pollinators were not identified. The stigma is covered by hairs and a secretion is produced. A high proportion of flowers were pollinated. Then, there was a rapid loss of flowers and young fruits. These observations and earlier genetic studies indicate the probability of a high level of self‐incompatibility in this predominantly outbreeding species. Pradu may have a very late‐acting self‐incompatibility mechanism found in many other hardwoods. The zygote remains quiescent for six weeks as the endosperm develops. During this time most of the ovules and fruits abort, suggesting resource allocation preferentially to cross‐pollinated ovules. Pradu has a high reproductive potential but a low preemergence reproductive success (0.8), which is common for many hardwood species. The major cause of the low reproductive success was fruit loss during early development. Fruit production may be enhanced by increased cross‐pollination among unrelated parent trees. This may be accomplished in seed orchards and seed production areas by the introduction of additional insect pollinators that travel greater distances between trees and by the relatively close spacing of unrelated parent trees.
The Role of Flower Width in Hummingbird Bill Length‐Flower Length Relationships1
Authors: Temeles Ethan J. , Linhart Yan B. , Masonjones Michael , Masonjones Heather D.
Published: March 2006

Observations of hummingbirds feeding at flowers longer or shorter than their bills seem to contradict the view that bill lengths of hummingbirds evolved in concert with the lengths of their flowers. Recent experiments, however, indicate that a hummingbird's ability to feed at artificial flowers of different lengths depends on the widths of the flowers. We examined if the broad range of flower lengths visited by many hummingbird species can be explained by the widths of the flowers. We predicted that both short‐ and long‐billed hummingbirds would include long, wide flower species in their diets, but that short‐billed hummingbirds would not include long, narrow flower species because nectar in these species might be beyond the reach of their bills. If so, the slope of the regression for flower width versus flower length should be smaller for flower species visited by longer‐billed hummingbirds relative to those visited by shorter‐billed hummingbirds. Analyses of data sets for some North American and Monteverde hummingbirds and their food plants were consistent with this prediction, and bill lengths were significantly correlated with the slopes of the regressions of flower width versus length for seven hummingbird species. Comparisons of observed flower use by some Monteverde hummingbird species to flower assemblages generated at random suggest that these significant regressions were not simply a result of allometric relationships between flower lengths and widths, but in some cases reflected active choice by the birds. The two hummingbird–flower data sets also differed significandy in the scaling of corolla width relative to corolla length. In particular, the Monteverde data set contained a large number of long, narrow flower species, which we suggest is a consequence of a different floral evolutionary history and association with long‐billed hummingbird species. The evolutionary effects of hummingbirds and their flowers upon one another are more complex than has generally been realized, and a consideration of corolla length jointly with other floral characters may improve our understanding of hummingbird‐flower relationships.
The Function of Hitchhiking Behavior in the Leaf‐cutting Ant Atta cephalotes1
Authors: Linksvayer Timothy A. , McCall Andrew C. , Jensen Rebecca M. , Marshall Cynthia M. , Miner Joshua W. , McKone Mark J.
Published: March 2006

In some leaf‐cutting ant species, minim workers ride on the fragments of leaves as they are carried back to the nest from the cutting site. There is convincing evidence that these “hitchhikers” can protect the leaf carriers from attack by phorid (Diptera: Phoridae) parasitoids, but we consider the possibility of other functions for the hitchhiking behavior. It has been hypothesized that the hitchhikers (1) feed on leaf sap from the edges of the cut leaves; (2) ride back to the nest to save energy; (3) get caught on the fragments as they are cut, and hitchhike because they cannot (or will not) get off; and (4) begin the process of preparing the leaf to enter the fungal gardens in the nest, perhaps by removing microbial contaminants. We observed hitchhikers of Atta cephalotes in 14 nests at the La Selva Biological Station in Costa Rica. There was no difference in the proportion of leaf carriers with hitchhikers between day and night. Because the nests we observed were largely nocturnal, more than 90 percent of the hitchhiking occurred at night. The phorid parasitoids are usually considered to be diurnal, so the preponderance of nocturnal hitchhiking suggests other functions in addition to parasitoid defense. Hitchhikers spent more time in the defensive head‐up posture during the day, but spent more time in the head‐down posture at night. The head‐down posture may indicate cleaning or other leaf preparation. The hitchhikers were never observed feeding on sap. Hitchhikers frequently got onto and off of the fragments, and so they were not “marooned.” Few hitchhikers rode all the way back to the nest and were often moving on the leaf fragment; these observations make the energy conservation hypothesis less likely, although we cannot reject it. We conclude that parasitoid defense is an important function of hitchhiking but also that there are probably other functions when parasitoids are absent. Based on available data, the most likely possibility is preparation of the leaf fragment before it enters the nest.
Response of Dung Beetle Diversity to Human–induced Changes in a Tropical Landscape1
Authors: Halffter Gonzalo , Arellano Lucrecia
Published: March 2006

This paper examines dung beetle communities in remnant patches of tropical deciduous forest at Veracruz, Mexico, as a case study of the effects of tropical deforestation on biodiversity. The two study areas have a common biogeographic history and similar macroclimatic conditions and have been modified by human activities to different extents. The main difference between them is that cattle, which provide the dung beetle's food supply, are present in only one of the areas. Comparison of the dung beetle faunas sheds light on the relative importance of forest cover versus food supply as the principal factor determining the structure and diversity of the fauna. This comparison, which we broaden through an examination of data from other localities in central Veracruz, permits us to speculate about what happens to biodiversity when a tropical deciduous forest undergoes modification of varying type and intensity. Where tree cover has been most modified, native forest species undergo local extinction and are replaced by open area species. On the whole, there has not been a net reduction in species richness (gamma diversity) in the fragmented landscape of central Veracruz, although local species richness (alpha diversity) has diminished.

RESUMES

En este trabajo se presenta una aproximación de lo que ocurre con la biodiversidad estudiada a través de un grupo indicador (los escarabajos del estiércol) en dos remanentes de bosque tropical caducifolio del estado de Veracruz, México. Los dos sitios comparten la misma historia biogeografica, condiciones macroclimaticas semejantes, y ser bosques parcialmente modificados por la actividad humana. La diferencia principal está en la oferta de alimento para los Scarabaeinae, porque solamente en uno de los lugares hay ganado vacuno. La comparación de la fauna de Scara‐baeinae de los dos lugares nos permite señalar que la cubierta forestal, y no la oferta de alimento, es el principal elemento conformador de la estructura y diversidad del gremio. Esta comparación, ampliada con datos de otros puntos de Veracruz centra nos permite especular lo que ocurre con la biodiversidad (representada por los Scarabaeinae) al modificarse el bosque tropical caducifolio en distintas formas e intensidades. Es relevante la sobrevivencia de las especies propias del bosque a nivel paisaje (diversidad gama), aunque puedan desaparecer en parte a escala puntual. Asi como su reemplazo por especies heliofilas en los puntos en que la vegetación arborea ha sido mas modificada. En conjunto el paisaje fragmentado y diverse de Veracruz centre no señala una pérdida de especies, aunque puntualmente (diversidad alia) si ocurra.
Survival, Growth, and Ecosystem Dynamics of Displaced Bromeliads in a Montane Tropical Forest1
Authors: Pett‐Ridge Jennifer , Silver Whendee L.
Published: March 2006

Epiphytes generally occupy arboreal perches, which are inherently unstable environments due to periodic windstorms, branch falls, and treefalls. During high wind events, arboreal bromeliads are often knocked from the canopy and deposited on the forest floor. In this study, we used a common epiphytic tank bromeliad,Guzmania berteroniana(R. & S.) Mez, to determine if fallen bromeliads can survive, grow, and reproduce on the forest floor and evaluate the potential impact of adult dispersal on plant and soil nutrient pools. Bromeliads were transplanted to and from tree stems and the forest floor and monitored intensively for six months; survival, growth, and impacts on ecosystem nutrient pools were followed on a subset of plants for 16 months. Six months after transplanting, bromeliad mortality was low (3%), and 19 percent of study individuals had flowered and produced new juvenile shoots. Mortality on the subset of plants followed for 16 months was 14–30 percent. Although survival rates were relatively high in all habitats, bromeliads transplanted to trees grew significantly more root length (x̄±SE: 189 ± 43 cm) than those moved to the forest floor (53 ±15 cm) and experienced lower rates of leaf area loss. All transplanted bromeliads rapidly altered the substrate they occupied. Individuals transplanted to and among trees rapidly decreased base cation concentrations but significantly increased P concentrations of their underlying substrate. On the ground, bromeliads increased C, N, and P concentrations within nine months of placement. Our results suggest that in this montane tropical forest, bromeliads respond rapidly to displacement, locally modify their substrates, and can access the resources needed for survival regardless of habitat.
Vertical Stratification and Caloric Content of the Standing Fruit Crop in a Tropical Lowland Forest1
Authors: Schaefer Hinrich Martin , Schmidt Veronika , Wesenberg Jens
Published: March 2006

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.
Are Tropical Highland Frog Calls Cold–adapted? The Case of the Andean Frog Hyla labialis1
Authors: Lüddecke Horst , Sínchez Oscar Raúl
Published: March 2006

Across a wide range of temperatures established in the laboratory, we tape–recorded the advertisement calls of 76 freshly caught Hyla labialis males from three elevationally separated populations in the Eastern Andes of Colombia. Each male was tested once at a single temperature and returned to his capture site after measurement of his snout–vent length. We measured and averaged three characteristics of five to ten successive calls for each individual: number of pulses per call, pulse repetition rate, and call duration. We found that calling activity occurred within temperature ranges that overlapped among frogs from different elevations, but widened and shifted downward with increasing altitude of origin. Males from all sites called at temperatures higher, but not lower, than those naturally occurring during their nightly activity period. No decline in vocal performance was apparent when frogs extended their calling activity into the range of high temperatures selected for basking. Both snout–vent length and temperature affected pulse repetition rate and call duration, while the number of pulses per call was temperature–independent. Compared to the smaller males from lower elevations, the larger, high–mountain males had calls with significandy more pulses, a lower pulse repetition rate, and longer duration. Within each population, rising temperatures caused pulse repetition rate to increase and call duration to decrease significantly, whereas the number of pulses per call remained unchanged. Pulse repetition rate of highland males was the factor least affected by temperature, and it was less sensitive to night temperatures than to day temperatures. This, together with their capacity to call at low temperatures, suggests that highland frog calls are cold adapted.
Dung Beetle Communities and Seed Dispersal in Primary Forest and Disturbed Land in Amazonia1
Authors: Vulinec Kevina
Published: March 2006

Seeds from tropical fruiting trees ingested and defecated on the soil surface by primary dispersers (such as primates) are vulnerable to destruction from rodents, insects, and fungi. Burial by dung beedes as an incidental result of their feeding and nesting activities often provides these seeds with refugia from attack. To examine the effect of habitat disturbance on the dung beetle communities involved in this process, I surveyed dung beedes at three sites in the Amazon basin, in die states of Parí, Amazonas, and Rondónia, Brazil. Through principal component analysis on measurements of size and behavioral characters of beedes, I determined the relative quality of beetle species as seed dispersers (dispersal defined as horizontal or vertical movement of seeds) and ranked them into seed dispersal guilds. I used correspondence analysis to examine in what habitats (primary forest or varying degrees of disturbed habitat) these guilds were abundant. Most guilds decreased with increasing habitat disturbance, but one guild made up of large nocturnal burrowers (primarily Dichotomius) became more abundant with increasing disturbance (up to the level of highest disturbance surveyed), at which point all dung beede species became scarce. Clear–cuts had lower species richness, lower abundance, and lower biomass dian forested areas. These results imply that clear–cutting is detrimental to all seed dispersal dynamics in tropical rain forests, but that some levels of disturbance allow enough disperser activity to preserve this ecosystem function.
Leaf Litter Decomposition and Monodominance in thePeltogyneForest of Marací Island, Brazil1
Authors: Villela Dora M. , Proctor John
Published: March 2006

The forest type dominated byPeltogyne gracilipes(Caesalpiniaceae) on the riverine Marací Island is the least speciesrich of any recorded for Brazilian Amazonia. Because the forest has high soil and foliar Mg concentrations, and Mg is known to be toxic to plant growth at high concentrations, this study tested the hypothesis that dominance byPeltogyneis related to Mg leaf litter amounts and decomposition. We predicted that decomposition ofPeltogyneleaves would differ from that of other species, and that their decomposition would result in a pulse of Mg release. Three plots (50 × 50 m) were established in each of three forest types:Peltogyne‐rich forest (PRF; dominated byP. gracilipes),Peltogyne‐poorforest (PPF), and forest withoutPeltogyne(FWP). Three leaf litter decomposition experiments tested if decomposition of mixed leaf litter in coarse‐ mesh (CM) litterbags differed among forests (experiment 1); whether or not decomposition and nutrient release ofEcclinusa guianensis, Lueheopsis duckeana, andPeltogynein CM litterbags differed among forests and species (experiment 2); and using fine‐mesh (FM) litterbags, investigated the differences in the influence of fauna! activity onEcclinusa and Peltogynedecomposition (experiment 3). Decomposition was independent of the presence and dominance ofPeltogyne, since decomposition rates in both PRF and FWP were in general lower than in PPF. These differences appeared to be related to fauna] activity. The decomposition ofPeltogyneleaves was lower than that of the other species tested and was more affected by microbial and physical action. It is possible that the monodominance ofPeltogyneis related to its deciduousness and faster decomposition in the dry season, which coincides with a large leaf fall. Magnesium was lost quickly from thePeltogyneleaves and the resultant pulses of Mg into the soil during the heavy rains at the beginning of the wet season may be deleterious for other species that are not adapted to high solution Mg concentrations. Results obtained were consistent with the hypothesis thatPeltogynedominance is related to the pattern of its leaf decomposition and the seasonal pulses of toxic Mg.
Seasonal Foraging Activity and Bait Preferences of Ants on Barro Colorado Island, Panama1
Authors: Hahn Daniel A. , Wheeler Diana E.
Published: March 2006

A yearlong arboreal baiting survey of ants was conducted during 1983 on Barro Colorado Island, Panama. Because of a severe El Nino event, the 1983 dry season in Panama was exceptionally long and dry with a distinct boundary between the dry and wet seasons. Baits, located on tree trunks, attracted both terrestrial and arboreal ants, allowing comparisons between the two groups. Species composition at baits changed dramatically with season. Baits were primarily occupied by arboreal species during the dry season, while wet season baits were occupied mostly by terrestrial species. Arboreal and terrestrial ants differed markedly in their preferences for protein‐ or carbohydrate‐based baits; arboreal ants preferred protein‐based baits and terrestrial ants preferred carbohydrate‐based baits. Foraging preference for protein suggests that protein resources were limiting for arboreal ants, particularly during the dry season, and that carbohydrate resources were limiting for terrestrial ants. Fundamental differences in arboreal and terrestrial habitats may promote the differences in foraging strategies observed during an annual cycle in a seasonal tropical forest.
Variation in Species and Trophic Composition of Insect Communities in Puerto Rico1
Authors: Barberena‐Arias M. F. , Aide T. M.
Published: March 2006

Insects are important participants in many ecosystem processes, but the effects of anthropogenic and natural disturbances on insect communities have been poorly studied. To describe how disturbances affect insect communities, we addressed two questions: Do insect communities return to a pre‐hurricane composition? And how do insect communities change during succession? To answer these questions, we studied insect communities in a chronosequence of two abandoned pastures (5 yr and 32 yr) and a mature forest (>80 yr) that were recently disturbed by two hurricanes (Hurricane Hugo, 1989) Hurricane Georges, 1998). Although insect abundance and richness fluctuated during the study, all sites returned to pre‐hurricane (Hurricane Georges) abundance and richness in less than one year. All trophic categories present before Hurricane Georges were present after the hurricane, but richness within categories fluctuated greatly. Insect richness did not increase during succession; the 5 yr site had the highest richness, the >80 yr site had an intermediate richness, and die 32 yr site the lowest. Nevertheless, the species composition of the two forested sites was different in comparison to the 5 yr site. These results suggest that trophic structure varies little in time and space, but the species composition within each trophic category is highly variable.
Home Range, Habitat Use, and Activity of Baird's Tapir in Costa Rica1
Authors: Foerster Charles R. , Vaughan Christopher
Published: March 2006

Home range size, habitat utilization, and activity patterns of five adult Bairds tapirs (Tapirus bairdii) were studied via radiotelemetry from June 1995 to May 1996 in Corcovado National Park, Costa Rica. Estimates of 4153 animal locations were made. Home range sizes (95% minimum convex polygon) for the entire study period (wet season and dry season) averaged 125.0 ha (SD = 72.7), 94.9 ha (SD = 47.6), and 96.8 ha (SD = 51.2), respectively. Monthly home range sizes averaged 55.5 ha (SD = 32.1) and did not vary between seasons. Across the entire study, secondary forest, the most commonly used habitat type (61.3%) was utilized more than expected as predicted by availability (49.6%), while the second most used habitat, primary forest, was used (25.0%) less than expected (36.2%). The same general habitat selection pattern was observed in the dry season. Wet season habitat utilization values showed tapirs using both primary and secondary forest habitats in proportion to their availability. Diurnal and nocturnal activity levels were estimated at 20.2 and 80.4 percent, respectively. More diurnal and less nocturnal activity was observed during the wet season compared to the dry season.
Postpollination Nectar Reabsorption and Its Implications for Fruit Quality in an Epiphytic Orchid1
Authors: Luyt R. , Johnson S. D.
Published: March 2006

We present evidence that pollination triggers nectar reabsorption in flowers of the epiphytic orchid Mystacidium venosum. The amount of sugar in nectar of M. venosum decreased significantly by more than 50 percent within 72 hours of pollination. Hand–pollinated flowers from which nectar was previously removed set significantly smaller fruits with a lower percentage of viable seeds than hand–pollinated flowers containing nectar, suggesting that resources reclaimed by nectar resorption are allocated to fruit production.
Effects of Forest Fragmentation on the Colima Long‐nosed Bat (Musonycteris harrisoni) Foraging in Tropical Dry Forest of Jalisco, Mexico1
Authors: Stoner Kathryn E. , Quesada Mauricio , Rosas‐Guerrero Victor , Lobo Jorge A.
Published: March 2006

We determined the effect of forest fragmentation on the nectarivorous Colima long‐nosed bat (Musonycteris harrisoni) by observing foraging behavior of this species in disturbed and undisturbed forests on the flowers of Ceiba grandiflora (Bombacaceae). The study was conducted in the area of the Chamela‐Cuixmala Biosphere Reserve in Jalisco, Mexico. Musonycteris harrisoni was observed visiting flowers during six nights (88 visits), exclusively in undisturbed forest. This species feeds on the nectar and serves as a pollinator of C. grandiflora.
Estimating Canopy Structure in an Amazon Forest from Laser Range Finder and IKONOS Satellite Observations1
Authors: Asner Gregory P. , Palace Michael , Keller Michael , Pereira Rodrigo , Silva Jose N. M. , Zweede Johan C.
Published: March 2006

Canopy structural data can be used for biomass estimation and studies of carbon cycling, disturbance, energy balance, and hydrological processes in tropical forest ecosystems. Scarce information on canopy dimensions reflects the difficulties associated with measuring crown height, width, depth, and area in tall, humid tropical forests. New field and spaceborne observations provide an opportunity to acquire these measurements, but the accuracy and reliability of the methods are unknown. We used a handheld laser range finder to estimate tree crown height, diameter, and depth in a lowland tropical forest in the eastern Amazon, Brazil, for a sampling of 300 trees stratified by diameter at breast height (DBH). We found significant relationships between DBH and both tree height and crown diameter derived from the laser measurements. We also quantified changes in crown shape between tree height classes, finding a significant but weak positive trend between crown depth and width. We then compared the field‐based measurements of crown diameter and area to estimates derived manually from panchromatic 0.8 m spatial resolution IKONOS satellite imagery. Median crown diameter derived from satellite observations was 78 percent greater than that derived from field‐based laser measurements. The statistical distribution of crown diameters from IKONOS was biased toward larger trees, probably due to merging of smaller tree crowns, underestimation of understory trees, and overestimation of individual crown dimensions. The median crown area derived from IKONOS was 65 percent higher than the value modeled from field‐based measurements. We conclude that manual interpretation of IKONOS satellite data did not accurately estimate distributions of tree crown dimensions in a tall tropical forest of eastern Amazonia. Other methods will be needed to more accurately estimate crown dimensions from high spatial resolution satellite imagery.
Composition Patterns of Caribbean Limestone Forests: Are Parsimony, Classification, and Ordination Analyses Congruent?1
Authors: Trejo‐Torres Jorge Carlos , Ackerman James D.
Published: March 2006

This study presents an analysis of floristic composition patterns for limestone vegetation from three Caribbean islands: Hispaniola, Mona, and Puerto Rico. The physical setting of these communities varies from very dry to wet climates, and from ridgetops, slopes, to plateaus. Consequently, vegetation communities have variable species composition. The questions addressed were: (1) What are the patterns of species composition among limestone vegetation types based on a parsimony analysis of species assemblages (PASA) and how congruent are they widi geography, climate, topography, and vegetation physiognomy? and (2) How do PASA patterns compare to floristic patterns obtained with a classification (UPGMA) and an ordination (NMS)? The main distinction of floristic categories was between communities of humid and dry climates, followed by a finer separation of communities congruent with topography; vegetation physiognomy corresponded with both. PASA, UPGMA, and NMS produced highly coincident floristic groups; however, affinities among groups were different. Advantages of PASA over UPGMA and NMS are that PASA produces groupings strictly based on the shared species and provides different measures of support for floristic groups. The three techniques indicated that the humid and dry limestone areas of Puerto Rico had floristically divergent dry‐type vegetation, even when they were structurally and physiognomically convergent. Also, floristic affinities of dry communities in Puerto Rico were stronger with dry communities on other islands than to more humid communities on the same island; thus, humidity regime is stronger than geography in promoting floristic links among limestone vegetation communities of die Caribbean. Almost every conclusion obtained from UPGMA and NMS was also taken from PASA, and so all diree techniques are compatible. The methodological, theoretical, and interpretive simplicity of PASA is what makes it an attractive procedure for studies that examine composition patterns.
Distribution and Diversity of Pteridophytes and Melastomataceae along Edaphic Gradients in Yasuní National Park, Ecuadorian Amazonia1
Authors: Tuomisto Hanna , Ruokolainen Kalle , Poulsen Axel Dalberg , Moran Robbin C. , Quintana Catalina , Cañas Gstavo , Celi Jorge
Published: March 2006

We documented the floristic composition of pteridophytes (ferns and fern allies) and Melastomataceae in Yasuní National Park, Amazonian Ecuador. Our main questions were: (1) Are the density of individuals, species richness, and/or species diversity (measured with Shannon's H′) of the two plant groups related to edaphic differences? and (2) How many of the pteridophyte and Melastomataceae species are non–randomly distributed in relation to a soil base content gradient within terra firme (non–inundated forest). To answer these questions, we sampled 27 line transects of 500 × 5 m distributed in an area of ca 20 × 25 km. The study area included a permanent 50 ha plot established to monitor forest dynamics; thus, our results also provide information on landscape–scale floristic variability to which results from within the plot can be compared. A total of 45,608 individuals and 140 species of pteridophytes, and 4893 individuals and 89 species of the Melastomataceae, were counted in the transects. Both with pteridophytes and with Melastomataceae, a clear negative correlation was found between the amount of extractable bases in the soil and the number of plant individuals encountered in a transect. With Melastomataceae, species richness and species diversity also were negatively correlated with soil base content, but with pteridophytes they were not. More than 50 percent of the common species of both pteridophytes and Melastomataceae were nonrandomly distributed along the soil cation content gradient within terra firme. We conclude that while the species richness patterns observed in one plant group are not indicative of similar patterns in other plant groups, it seems likely that a substantial (but unknown) proportion of species belonging to other plant groups will be found to show distribution patterns that reflect edaphic preferences within terra firme forests.
Spatio–temporal Variations in Post‐dispersal Seed Fate1
Authors: Feer François , Forget Pierre‐Michel
Published: March 2006

The post‐dispersal fate of Chrysophyllum lucentifolium (a canopy tree; Sapotaceae) seeds was analyzed in French Guiana over three consecutive years. Experiments using 750 thread‐marked seeds were performed to investigate seed removal, predation, and caching by terrestrial vertebrates on howler monkey (Alouatta seniculus) defecation sites, where clumps of intact C. lucentifolium seeds were observed. Year‐to‐year variations in seed fate during the peak fruiting period were considered in relation to overall fruit and seed resource availability estimated by a raked‐trail survey. The effect of two forest areas, which differed in soil and floristic composition, was examined with conspecific fruiting tree density as a covariant. Exclosure versus open treatment was used to discriminate small rodents (not larger than a spiny rat) from other vertebrates. The presence of fresh howler dung did not affect seed fate after 20 days as shown by comparisons between defecation sites and control during the first year. There was a significant effect of year on the percentage of seeds remaining after 20 days. Low seed removal in 1995 and 1996 (compared to 1997) corresponded to higher overall fruiting and higher fruiting of C. lucentifolium, or the presence of alternative resources for rodents. An effect of forest area was observed on the seed removal rate, which varied with years and protection. Comparatively, an effect of forest area on the percentage of seeds lost was observed in 1996 and an effect of treatment on the percentage of seeds eaten was seen in 1995. The mode of seed caching suggested that spiny rats were the main seed remover. Results of this study suggest that greater seedling recruitment may occur when large fruit crop and high howler dispersal co‐occur with a lower impact of rodents (i.e., when rodents are saturated by abundant and diversified fruit resources such as in 1995). Such event synchrony, however, is highly unpredictable after only three years of study.
Canopy Ferns in Lowland Dipterocarp Forest Support a Prolific Abundance of Ants, Termites, and Other Invertebrates1
Authors: Ellwood Martin D. F. , Jones David T. , Foster William A.
Published: March 2006

The epiphytic Bird's Nest Fern (Asplenium nidus complex) has a large basket‐shaped rosette that accumulates leaf litter. We investigated the role of these ferns in supporting invertebrate populations in the primary lowland dipterocarp forest of Danum Valley, Sabah, Malaysia. Ferns were divided into three size classes: large (rosette diameter >60 cm), intermediate (30–60 cm), and small (<30 cm). Seven hectares of forest were surveyed: the canopy had a mean density of 30 large ferns/ha and 20 intermediate ferns/ha. Six large and five intermediate ferns were removed from the crowns of Parashorea tomentella (Dipterocarpaceae) at heights between 39 and 52 m. The largest ferns had fresh weights of ca 200 kg. The mean animal abundance in large and intermediate ferns was 41,000 and 8000, respectively. Termites and ants represented at least 90 percent of the abundance in these ferns. Of die 11 ferns, 4 contained a nest of Hospitalitermes rufus (Nasutitermitinae), while another contained a nest of an undescribed species of Hospitalitermes. An additional 56 small ferns were removed from die low canopy (2–6 m above the forest floor), of which only 1 contained a termite nest (Nasutitermes neoparvus). These results suggest that Bird's Nest Ferns contain ca 0.5 million termites/ha and contribute almost one ton (dry mass) of suspended soil and plant material/ha. Five of the trees containing large ferns were fogged immediately before the removal of die ferns. From these samples we were able to estimate the total number of animals in each tree crown. When each estimate was added to die abundance in each fern, the results suggested that a single large fern may contain from 7 to 93 percent of die total number of invertebrates in die crown. Although these results must be treated with caution because of die small sample size, they have important implications for studies of canopy invertebrates.
Use of Fruiting Trees by Birds in Continuous Forest and Riparian Forest Remnants in Los Tuxtlas, Veracruz, Mexico1
Authors: Graham Catherine , Martínez‐Leyva Jesús Eduardo , Cruz‐Paredes Leticia
Published: March 2006

The composition of plant species in fragmented landscapes may be influenced by the pattern of visitation by birds to fruiting trees and by the movement of seeds among and within fragments. We compared bird visitation patterns to two tree species (Dendropanax arboreus, Araliaceae; Bursera simaruba, Burseraceae) in continuous forest and remnants of riparian vegetation in a region dominated by pasture in Los Tuxtlas, Veracruz, Mexico. We quantified frequency of visitation, fruit consumption, consistency of visitation (percentage of total tree observation periods during which a given bird species was recorded), and species composition of birds at individuals of both tree species in continuous forest and riparian remnants. Bird visitation rate, species richness, and fruit consumption rates were similar within both tree species in the two habitats. Species assemblages at D. arboreus were different between continuous forest and remnants. Species assemblages at B. simaruba did not differ by habitat. Our results demonstrate that habitat disturbance may influence avian visitation patterns, which may in turn affect subsequent recruitment patterns in some tree species. Our results, however, were not consistent between the tree species, suggesting that it is difficult to generalize concerning the effects of forest disturbance on avian species assemblages in fruiting trees.