bluuebunny/crossref_metadata_2025 huggingface dataset:
Litterfall Mass, Chemistry, and Nutrient Retranslocation in a Monodominant Forest on Maracá Island, Roraima, Brazil1
Authors: Villela Dora M. , Proctor John
Published: March 2006

Maracá Island is on the boundary of the Amazon rain forest and the Rio Branco‐Rupunini savanna. The annual rainfall is ca. 1800 mm, with a dry season from October‐March and a wet season from April‐September. A forest type dominated by Peltogyne gracilipes (Caesalpiniaceae) occurs on parts of the island and the adjacent mainland, the least species‐rich (for trees > 10 cm DBH) of any recorded in Brazilian Amazonia. The goal of this study was to test the hypothesis that the dominance by Peltogyne is associated with an unusual litterfall mass, nutrient concentrations, or retranslocation. Three plots (50 × 50 m) were set up in each of three forest types: (1) Peltogyne‐rich forest (PRFa), dominated by Peltogyne gracilipes; (2) Peltogyne‐poor forest (PPF), with a sparse occurrence of Peltogyne; and (3) forest without Peltogyne (FWPa). Litterfall was collected for 360 d at ca 15‐d intervals in 11 randomly positioned traps (0.32 m2) per plot. Mature Peltogyne leaves were collected at random from three randomly selected understory Peltogyne trees in each of the three PRFa plots during the early dry and early wet season. Additionally, young Peltogyne leaves were collected during the early wet season. Chemical analyses were made on bulked (on a 2‐mo basis) litterfall samples and young and mature Peltogyne leaves. The estimated annual litterfall was similar among PRFa (7.9 t/ha), PPF (9.1 t/ha) and FWPa (8.6 t/ha); however, PRFa was distinguished by its litterfall seasonality, because of the deciduous Peltogyne, and its higher concentrations of Ca (9.3 compared to 6.5 mg/g in FWPa) and Mg (3.2 compared to 1.9mg/g in FWPa). About 40–50 percent of N and P, 25–41 percenr of K, and 2–13 percent of Mg were rerranslocated from Peltogyne leaves.
Factors Limiting Tropical Rain Forest Regeneration in Abandoned Pasture: Seed Rain, Seed Germination, Microclimate, and Soil1
Authors: Holl Karen D.
Published: March 2006

Vegetation, seed rain, seed germination, microclimate, and soil physical and chemical parameters were measured in a recently abandoned pasture and adjacent primary rain forest in southern Costa Rica. The goal of this study was to assess the importance of these factors in limiting forest regeneration in abandoned pastures. Seed rain of animal dispersed species decreased dramatically in the pasture >5 m from the forest/pasture edge; fewer wind dispersed seeds fell in the pasture than in the forest, but the difference was much less than for animal dispersed seeds. Percent seed germination of most species studied was similar in the forest and in pasture with grasses; seed germination was lower during the dry season in areas of pasture cleared of grasses. Air temperature, vapor pressure deficit (VPD), and photon flux density (PFD) were much higher in the pasture than in the forest at 1 m above the ground. VPD and PFD at ground level and soil temperature were similar in the pasture and the forest, indicating that pasture grasses strongly modify microclimatic conditions near the soil surface. The lowest gravimetric water content recorded in the pasture during the dry season was 0.5 and leaf relative water contents of the two species measured in the forest and pasture were identical, suggesting that plants in the pasture were not water stressed. Levels of most soil nutrients were lower in the pasture as compared to the forest; however, aboveground and root biomass for seedlings grown in pasture and forest soils did not differ significantly. Although a number of factors impede forest recovery in abandoned pastures, these results suggest that the most imporrant limitation is lack of seed dispersal.
Vegetative Life History of a Dominant Rain Forest Canopy Tree1
Authors: Gavin Daniel G. , Peart David R.
Published: March 2006

Tetramerista glabra has a remarkable combination of life history traits. It is a dense‐wooded, large, common canopy tree in primary peat swamp rain forest. Its seedlings, although shade tolerant, can grow rapidly in high light conditions, but frequently lack structural stability. Most juvenile stems (94% in the understory and 38% in canopy gaps) collapse under their own weight or from branchfalls. Fallen stems then ramify into vegetative sprouts, which in turn may collapse, perpetuating a vegetative juvenile cycle. Most recruitment is from sprouts rather than from seed. Structural analysis of stem dimensions shows that stems 2–8 cm DBH (diameter at breast height) are close to the theoretical buckling limit, especially for those dependent on neighboring vegetation to maintain vertical form. Trees > 4 cm DBH persisting as upright stems develop stilt root support and become structurally independent at ca 8 cm DBH. Eventually, as stems thicken, stilt roots anastamose and trees adopt the cylindrical growth form of mature canopy trees (up to 150 cm DBH). Thus, the vegetative life history strategy of the species is to: (i) regenerate a large “ramet bank” from the majority of juveniles that fail structurally while suppressed in the understoty, and (ii) to maximize height growth at the expense of diameter growth in high light conditions. The growth pattern and plastic form of T. glabra shows how a shade tolerant species may adapt to utilize the ephemeral light resource in canopy gaps. The growth strategy of this species allows it to circumvent the normal trade‐off between shade tolerance and rapid growth in canopy gaps.
Ants, Stem Borers, and Pubescence in Endospermum in Papua New Guinea1
Authors: Letourneau Deborah K. , Barbosa Pedro
Published: March 2006

The stems of the ant‐plant, Endospermum labios Schodde, serve as colonization sites for the ant, Camponotus quadriceps F. Smith. They are also subject to damage by insect borers. We sampled young E. labios trees in distutbed forest to compare evidence of stem boring insect and stem miner damage in plants with and without colonies of C. quadriceps. Dissections of a subsample of plants showed that dipteran stem borers and stem miner damage were significantly more common in plants lacking C, quadriceps colonies than in plants with established colonies. Evidence from these dissections and from field counts of meristem damage caused by emerging borers suggested that coleopteran stem borers were also more abundant when ants were not present.

In addition to the incidence of stem boring insects and ant colonies, we examined relative levels of leaf pubescence by measuring trichome density and leaf size for E. labios trees. We found that trichome density was significantly greater in trees with evidence of prior shoot damage (presumably from stem borer emergence at the meristem) but was not significantly related to the presence or absence of an ant colony. This prompted us to compare trichome density on leaves of nearby small trees and of different branches of the same tree, pairing a stem/branch that appeared damaged with one that appeared healthy. Trichome densities on leaves from damaged stems and branches were significantly greater than were trichome densities on healthy branches and stems. Based on these empirical data, we present several possible explanations for the patterns of association between ants, stem borers, and pubescence. Although feeding preference tests with a common folivore showed no effect of trichome densities on leaves, we suggest further study on how trichomes may affect ovipositing stem borers.
Evaporative Water Loss in Insular Populations of the Anolis cristatellus Group (Reptilia: Sauria) in the British Virgin Islands II: The Effects of Drought1
Authors: Perry Gad , Dmi'el Razi , Lazell James
Published: March 2006

Previous work has shown that water loss in some populations of Anolis cristatellus from the British Virgin Islands is closely tied to the conditions available on the islands they inhabit. This manifested itself in a strong correlation between habitat aridity and several water loss rate parameters. Here we report on a similar study conducted in the same locations in 1994, a year of extreme drought.

We hypothesized that lizards caught at the height of the drought will experience lower rates of water loss than those measured during a normal year. Our findings show that in 1994, as in 1993, habitat aridity and water loss parameters were strongly correlated. Also as before, the Guana Island population of A. cristatellus displayed higher resistance to water loss than expected by the island's aridity. However, a striking change occurred within populations. All were at least as good at retaining water (measured as integumentary resistance to water loss, R) as in 1993, and some were over 3.5 times better. Existing evidence is insufficient to determine whether these changes were the result of phenotypic plasticity or attributable to differential mortality of nonresistant individuals.
Roosting and Foraging Behavior of Two Neotropical Gleaning Bats, Tonatia silvicola and Trachops cirrhosus (Phyllostomidae)1
Authors: Kalko Elisabeth K. V. , Friemel Dorothea , Handley Charles O. , Schnitzler Hans‐Ulrich
Published: March 2006

We studied roosting and foraging behavior of two Neotropical gleaning bats, ďOrbigny's round‐eared bat, Tonatia silvicola, and the fringe‐lipped bat, Trachops cirrhosus (Phyllostomidae). Techniques included radio‐tracking in a tropical lowland forest in Panama and analysis of data from long‐term studies in Panama and Venezuela. Day roosts of T. silvicola were in arboreal termite nests. T. cirrhosus roosted in a hollow tree. T. silvicola emerged late (ca 60 min after sunset), and foraged close to the roosts (maximum distance 200–500 m). T. cirrhosus emerged early (ca 30 min after local sunset), and foraged farther from its roost (>1.5 km). Both bats used small foraging areas (3–12 ha) in tall, open forest. They foraged in continuous flight (maximum 27–36 min) or in short sally flights (<1 minute) from perches (“hang‐and‐wait” strategy). The small foraging areas of these bats and their sedentary foraging mode most likely make them vulnerable to habitat fragmentation.
Short‐Term Disappearance of Foliar Litter in Three Species Before and After a Hurricane1
Authors: Sullivan Neal H. , Bowden William B. , McDowell William H.
Published: March 2006

Litter disappearance was examined before (1989) and after (1990) Hurricane Hugo in the Luquillo Experimental Forest, Puerto Rico using mesh litterbags containing abscisedCyrilla racemiflontorDacryodes excelsaleaves or freshPrestoea montanaleaves. Biomass and nitrogen dynamics were compared among: (i) species; (ii) mid‐ and high elevation forest types; (iii) riparian and upland sites; and (iv) pre‐ and post‐hurricane disturbed environments. Biomass disappearance was compared using multiple regression and negative exponential models in which the slopes were estimates of the decomposition rates subsequent to apparent leaching losses and the y‐intercepts were indices of initial mass losses (leaching).Cyrilla racemifloraleaves with low nitrogen (0.39%) and high lignin (22.1%) content decayed at a low rate and immobilized available nitrogen.Dacryodes excelsaleaves had moderate nitrogen (0.67%) and lignin (16.6%) content, decayed at moderate rates, and maintained the initial nitrogen mass.Prestoea montanafoliage had high nitrogen (1.76%) and moderate lignin (16.7%) content and rapidly lost both mass and nitrogen. There were no significant differences in litter disappearance and nitrogen dynamics among forest types and slope positions. Initial mass loss ofC. racemifloraleaves was lower in 1990 but the subsequent decomposition rate did not change. Initial mass losses and the overall decomposition rates were lower in 1990 than in 1989 forDacryodes excelsa. Dacryodes excelsaandC. racemifloralitter immobilized nitrogen in 1990 but released 10‐15 percent of their initial nitrogen in 1989, whereasP. montanareleased nitrogen in both years (25‐40%). Observed differences in litter disappearance rates between years may have been due to differences in the timing of precipitation. Foliar litter inputs during post‐hurricane recovery of vegetation in Puerto Rico may serve to immobilize and conserve site nitrogen.
Biomass Allocation in Cyperus papyrus in a Tropical Wetland, Lake Naivasha, Kenya1
Authors: Boar Rosalind R. , Harper David M. , Adams Christopher S.
Published: March 2006

The nutrient status of Lake Naivasha, a freshwater lake in southeastern Kenya, has been rising since at least 1982. A potential effect of increases in nutrient supply to the lake's floating papyrus is increasing of the plants’ investment in above–water material and reduction of the amount of energy invested in uptake and storage. Biomass and its allocation between culms, panicles, roots, and rhizomes was measured in 17 sites around the 150–km2 lake. Although above–water biomass was greatest in sites closest to the lake's major nutrient inflow, the River Malewa, there was little evidence of corresponding decreases in the biomass of uptake and storage tissues. In August 1995, the average ± SD biomass of papyrus in the lake was 11,540 ± 3020 g/m2, with the papyrus containing about 4500 ± 1900 g total carbon/m2 and about 100 ± 70 g total nitrogen/m2. Plant nitrogen contents did not vary with distance from the main external nutrient supply. Together with low nitrogen concentrations in the plants (0.60 ± 0.26 in culms and 0.99 ± 0.50% in rhizomes), very high carbon to nitrogen ratios (49 ± 20:1) and nitrogen fixation in the rhizosphere explaining only about half of the plants’ nitrogen, papyrus is a likely net sink for nitrogen supplied from the lake's increasingly cultivated watershed. Despite this role, clearance of papyrus in favor of agriculture partly explains the reductions in the area of papyrus within the lake basin from 48 km2 in the late 1960s to 14 km2 in 1995.
Effects of Light Regime on Antioxidant Content of Foliage in a Tropical Forest Community1
Authors: Frankel Steven , Berenbaum May
Published: March 2006

A basic tenet of plant ecology is that under high light and limiting nutrient levels, carbon becomes relatively more available for investment in anti‐herbivore defense. Rarely considered in discussions of such defense investments, however, is the necessity for plants to defend themselves against oxidative damage caused by light exposure itself. To determine if the ability to respond to elevated levels of light exposure by increasing production of antioxidant compounds is a general characteristic of foliage in tropical plants, we conducted a broad survey of antioxidant content in foliage of 55 species in a tropical forest community by comparing individuals within forest gaps to conspecifics in the closed canopy forest. To do so, we devised a rapid assay to use under field conditions. Of the 41 species of shrubs, trees, and lianas demonstrating a discernible difference in antioxidant content under the two light regimes, 34 (68%) showed higher antioxidant content under high light conditions. In a quantitative laboratory‐based study using four of these species, light was associated with a 15 to 45 percent increase in water‐soluble antioxidants in three species; one species displayed a 118 percent increase in fat‐soluble antioxidants as well. Thus, changes in the chemistry of plant foliage in response to light may reflect plant investments in defense against abiotic stress factors as well as investments in defense against biotic stress factors.
Patterns of Clonal Diversity in Dicranopteris linearis on Mauna Loa, Hawaii1
Authors: Russell Ann E. , Ranker Tom A. , Gemmill Chrissen E. C. , Farrar Donald R.
Published: March 2006

The clonal mat‐forming fern, Dicranopteris linearis (N. L. Burm.) Underw., dominates vast areas of rainforests on the windward slopes of Mauna Loa Volcano on the island of Hawai'i. Because clone size has important ecological and evolutionary consequences in such a dominant species, we used isozyme analysis to investigate clone size and other aspects of genetic diversity and reproduction over a broad range of environmental conditions on primary successional sites (pahoehoe lava substrates).

Isozyme analysis provided a measure of the upper limit of clonal size in this interdigitating clonal species. Each 0.5‐ha primary successional site on Mauna Loa was comprised of a minimum of two to four clones. Genetic diversity in Dicranopteris was low; of 32 putative loci investigated, only 4 were polymorphic, with 2 or 3 alleles/locus. Over the 17 study locations on Mauna Loa and Kilauea Volcanoes, we identified nine multilocus genotypes based on unique combinations of allozymes. Seven of the nine genotypes were heterozygous for at least one locus, evidence of an intergametophytic mating system. Highly dispersible spores, coupled with intergametophytic mating should promote higher genetic diversity. We propose that the following factors contributed to low genetic diversity: founder effects; extreme isolation from mainland gene pools; high potential for mating among different gametophytes produced from the same sporophyte; relatively low numbers of safe sites for gametophyte establishment over space and time; and long‐term reliance on vegetative growth. Leaf phenotypes were associated with genotype, but also with environmental conditions. Enough variability within a genotype existed to support the current treatment of Hawaiian Dicranopteris as one species.

Vegetative growth was the primary means by which Dicranopteris covered the landscape. Nevertheless, spore production, gametophyte establishment, and sexual reproduction were absolutely essential for colonization of the few favorable microsites available on pahoehoe lava substrates of Mauna Loa following lava eruptions, dieback, and similar landscape‐level disturbances.
Inflorescence Height Affects Visitation Behavior of Bees–A Case Study of an Aquatic Plant Community in Bolivia1
Authors: Gumbert Andreas , Kunze Jan
Published: March 2006

We studied the bee fauna visiting a plant community of 10 species of flowering aquatic plants in an inundated savanna region in Bolivia. In total we observed 36 bee species in 17 genera at the flowers. Cluster analysis of the similarities among the plant species in terms of their visitor spectra showed a division into two groups: plants with inflorescence heights shorter than the grass height and plants with inflorescences projecting out of the surrounding vegetation. Larger bees of the genera Apis, Melipona, Bombus, and Xylocopa were observed only at flowers above the surrounding vegetation. Smaller, mainly solitary bees (e.g., Augochlorella, Ancyloscelis) visited flowers in the dense vegetation near the water surface. Analyses of the pollen loads revealed that most individuals were highly flower constant. When bees carried different pollen types, it was generally pollen from flowers within a single stratum. We discuss specialization, flower constancy, competition, and different foraging strategies as possible reasons for stratum fidelity.
Use of Vocal Signatures for the Inventory of Free‐flying Neotropical Bats1
Authors: O'Farrell Michael J. , Miller Bruce W.
Published: March 2006

An ongoing study is being conducted to test the efficacy of the Anabat II detector and analysis system in obtaining reliable vocal signatures for the identification of non–phyllostomid species of bats. We sampled a wide range of elevations and associated habitat types throughout Belize. Anabat provides an instantaneous output of echolocation call structure with a laptop computer. Select sequences can be saved directly to the hard drive, avoiding extraneous noise and sound distortion commonly associated with tape recorders. To date, 18 of the 37 species known or expected to occur in the study region were identified by recognizable differences in the time–frequency characteristics of echolocation calls. In general, each family is recognizable by call structure patterns and species readily separated by frequency range parameters. Species that commute or forage at high altitudes are not susceptible to capture but are conspicuous by acoustic sampling. Further work is needed to determine limitations of the equipment, establish better sampling procedures, and develop a comprehensive library of vocal signatures incorporating the range of variation inherent in each species. As this work progresses, we predict the addition of hitherto unknown species occurring within the study region.
Long‐term Persistence of Raphia taedigera Mart. Swamps in Nicaragua1
Authors: Urquhart Gerald R.
Published: March 2006

The palm Raphia taedigera Mart, forms vast, monodominant swamps in Central and South America, but very little is known about the ecology and natural history of these ecosystems. Debate surrounds the issue whether R. taedigera swamps are early successional stages or mature “climax” communities. This paleoecological analysis of a 1.46‐m sediment core from swamps on the Caribbean coast of Nicaragua establishes the abundant presence of R. taedigera swamps for at least 2800 ± 90 years. R. taedigera swamps must be considered persistent communities, warranting further study because of their great extension into Central and South America.
Vagility and the Monsoon Rain Forest Archipelago of Northern Australia: Patterns of Genetic Diversity in Syzygium nervosum (Myrtaceae)1
Authors: Shapcott Alison
Published: March 2006

Syzygium nervosum is a common monsoon rain forest tree. Its habitat in Australia consists of small rain forest patches that are scattered through a savanna matrix. It is a mast flowering canopy species that produces large quantities of fruits fed on by mobile frugivores such as birds and fruit bats. The genetic diversity of this species was investigated, especially in relation to rain forest patch size, geographic isolation, and geographic distribution. Syzygium nervosum was found to have high levels of genetic diversity within populations (He= 0.307). Diversity among populations, however, was relatively low (Fsr = 0.118), and was not spatially structured across its geographic range in Australia. This is thought to have been caused by relatively frequent gene flow among populations (Nm= 1.67), mediated primarily by mobile frugivores. Genetic diversity was not correlated with patch size or isolation. It is thought that seed dispersal by frugivores has acted to expand the effective population size of this species beyond the individual rain forest patch, and thus has prevented the substantial loss of genetic diversity that otherwise would have been observed. Thus this species is dependent upon these frugivores for the maintenance of its genetic diversity and hence its long‐term viability. These results lend support to theories of post‐Holocene expansion of rain forest by vagile species in northern Australia.
Small Gap Creation in Belizean Mangrove Forests by a Wood–Boring Insect1
Authors: Feller IIka C. , McKee Karen L.
Published: March 2006

We investigated the role of wood‐boring insects in the creation of light gaps within mangrove forests. We compared the frequency of gaps caused by wood borers to other gap‐forming processes and characterized the physical attributes of light gaps in mangrove forests on small islands in Belize. Methods of quantifying light gaps included aerial photography, ground surveys, and experimental plots. Small light gaps (≤12 m2) were very common in Rhizophom mangle fringe, comprising almost 22 percent of these forests. Rhizophora mangle gaps were smaller than gaps in Avicennia germinans forests. In R. mangle forests, gaps were caused by branch death, and in A. germinans forests, gaps were caused primarily by downed trees. More than 91 percent of the gap‐forming branches and boles in the R. mangle fringe were killed by a wood‐boring cerambycid beetle, Elaphidion mimeticum, indicating that it is the major cause of small‐scale disturbances in these forests. No trees or branches in the A. germinans forest were attacked by this beetle. In R. mangle forests, small gaps had significantly higher light levels and soil temperatures than areas under the closed canopy; however, soil conditions for sulfide concentrations, porewater salinity, and redox potentials were similar in small gaps and under the closed canopy. Survival of R. mangle, A. germinans, and Laguncularia racemosa seedlings was also higher inside these small gaps, indicating their importance in regeneration of mangrove forests. Feeding by wood borers is thus an important type of indirect herbivory in mangrove forests, with a critical role in ecological processes such as gap dynamics.
Reproductive Ecology of Understory Species in a Tropical Montane Forest in Costa Rica1
Authors: Wesselingh Renate A. , Witteveldt Martin , Morissette Julienne , den Nijs Hans C. M.
Published: March 2006

The reproductive ecology of nine hermaphroditic understory species in a tropical montane Quercus forest was studied at two sites (2300 and 2600 m elev.) in the Cordillera de Talamanca, Costa Rica. Flower life span, studied in six species, averaged 4.4 d. This is longer than flower life spans found in the Monteverde cloud forest (2.7 d) and comparable to flower life spans found for arctic and alpine species. We studied the breeding system in five species and found no self‐incompatible species. Four species proved self‐compatible, and three of these showed autogamy. The main diurnal insect pollinator was the bumblebee Bombus ephippiatus. Natural fruit set was low (8‐32%) in six species with few seeds per fruit, while two many‐seeded species showed a high rate of fruit set (90 and 96%). The incidence of pre–dispersal seed predation was high; the percentage of seeds infested in four species ranged from 8 to 56 percent.
Rareza y Diversidad de Hormigas en Fragmentos de Bosque Seco Colombianos y sus Matrices1
Authors: Armbrecht Inge , Ulloa‐Chacón Patricia
Published: March 2006

Los bosques secos del valle medio del Rio Cauca (suroeste de Colombia) ban sido casi eliminados de la región y los últimos remanentes corren peligro de desaparecer. Este estudio registra el valor boilógico de siete fragmentos de bosque comparando la diversidad y rareza de hormigas dentro de ellos con la de las matrices (alrededores antropogénicos del bosque). Entre agosto de 1994 y febrero de 1995 se hicieron dos muestreos intensivos de hormigas en cada fragmento boscoso y su matriz. El esfuerzo de muestreo fue similar en cada uno de los siete sitios. Todos los fragmentos boscosos fucron más ricos y más diversos que sus matrices respectivas. Los bosques preservan un número mayor de especies raras de hormigas que las matrices. A medida que el bosque se hace más rico en hormigas, mayor es el número dc especies de hormigas exclusivas que preserva. Estos bosques deben ser preservados para mantener la biodiversidad regional.
Seed Dispersal by Salvin's Curassow, Mitu salvini (Cracidae), in a Tropical Forest of Colombia: Direct Measurements of Dispersal Distance1
Authors: Yumoto Takakazu
Published: March 2006

Seed dispersal by Salvin's curassows (Mitu salvini) was studied in a lowland tropical forest at La Macarena on the border of the Macarena and Tinigua National Parks, the Department of Meta, Colombia. Continuous observations were made on the feeding and ranging behavior of a well‐habituated pair of birds from 0600 to 1800 h for 19 days. Ibtal observation time was 222 h. The daily distance traveled by the birds ranged from 630 to 3750 m, with a mean of 1959 m (± 776 m). The total home range was ca 34.4 ha. Although curassows were observed consuming fruits of 13 species belonging to the families Rubiaceae, Meliaceae, Moraceae, Burseraceae, Leguminosae, and Lecythidaceae, only seeds of Geophila re fens (Rubiaceae) and Picas spbenophylla (Moraceae) were found in their feces. For G. repens, the mean and maximum retention times were 1 h 52 min (± 1 h 20 min) and 6 h 08 min, and the mean and maximum direct dispersal distances were 245 m (± 164 m) and 633 m. More than half the seeds were dispersed in canopy gaps. For F. sphenophylla, the mean and maximum retention times were 3 h 1 5 mm (± .37 min) and 7 h 08 min, and the mean and maximum direct dispersal distances were 329 m (± 46 m) and 451 m. Nearly 60 percent of the estimated seed intake of G. repens and 92‐94 percent of F. sphenophylla were digested or damaged. The retention times and the dispersal distances for Streptogyna americana, which has adhesive burrs, were also measured. The mean and maximum retention times were 1 h 55 min (± 1 h 56 min) and 9 h 11 min, and the mean and maximum direct dispersal distances were 128 m (± 68 m) and 280 m. This is the first study in which direct measurements were made for retention times and dispersal distances of the epizoochory and endozoochory for birds in the field.
Mangrove Distribution during the Holocene in Tribugí Gulf, Colombia1
Authors: Jaramillo Carlos , Bayona Germín
Published: March 2006

Neotropical mangrove ecosystems have undergone drastic changes in terms of extension and floristic composition during Plio–Pleistocene times. It is unclear if the northern Pacific coast of Colombia has been occupied continuously by mangroves during the last 5000 years, or if their presence is a recent phenomenon. Two basic questions were asked: (1) is the establishment of mangroves recent?; and (2) what were the dominant floral taxa during the late Holocene? In the Gulf of Tribugí, northern Colombian Pacific, 22 sediment cores were drilled to a maximum depth of 2 m in a diverse suite of mangrove substrates and positions relative to the shoreline. Data were gathered from sedimentological descriptions, palynological analyses, and radiocarbon dating of these cores. During the last 4500 years, mangroves in the southern area of the Tribugí Gulf have remained floristically stable and dominated by Rhizophora. The abundant presence of Acrostichum aureum is recent, probably related to human activities. In contrast, two areas in the northern part of the Gulf show a different history. In the first area, the establishment of mangrove has been relatively recent (ca 2600 yr), probably a result of local subsidence due to tectonic faulting; this mangrove forest was and is dominated by Pelliciem rhizophorae. In the second area, mangrove pollen was not found in sediments younger than 2500 years, suggesting that the scarce presence of mangrove in the area is a result of recent colonization, and not due to logging as previously thought.
Developmental Patterns of Tree Dimensions in a Neotropical Deciduous Forest1
Authors: Bullock Stephen H.
Published: March 2006

For 26 tree species in very dry tropical forest in Mexico, the developmental trends of relationships among trunk diameter, tree height, and crown diameter were inferred from a one‐time measurement of dispersed individuals across the size range from saplings to large, mature trees. On hillside sites in this high diversity forest, maximum dimensions were usually <10‐m height, 4‐m crown diameter, and 0.3‐m trunk diameter. The relationship of height to trunk diameter was characterized by an asymptotic, three‐parameter model. Crown diameter was a linear function of trunk diameter. The parameter values for both models varied widely among the species. In general, the dispersion among species of the height–crown diameter relationship increased linearly with trunk diameter (up to 0.2 m). Arborescent cacti were distant from other species at all sizes, although they were well modeled using the same equations. Empirical and theoretical features and limitations of the present and previous models, including mechanical buckling and water‐stress theories, are considered.
Insights into the Witheringia solanacea (Solanaceae) Complex in Costa Rica. II. Insect Visitors and Pollination Biology of W. asterotricha and W. meiantha1
Authors: Bohs Lynn
Published: March 2006

Isolating mechanisms are important in maintaining the taxonomic integrity of closely related sympatric taxa. A previous study found strong post‐zygotic isolating barriers between two species, Witheringia asterotricha and W. meiantha, of the W. solanacea (Solanaceae) species complex in Costa Rica. This study examines the presence of pre‐zygotic barriers between the two species at La Selva Biological Station in Costa Rica. Both species offer pollen and nectar as floral rewards and are visited primarily by solitary or semi‐social bees, some of which sonicate (“buzz”) the anthers to discharge pollen. No evidence was found for phenological differences in flowering time between W. asterotricha and W meiantha, but pre‐zygotic factors, such as ethological isolation and possibly fine‐scale ecological or geographic barriers, may be responsible for restricting gene flow between the two species.
Relationship between Plant Size and Ant Associates in Two Amazonian Ant‐Plants1
Authors: Vasconcelos Heraldo L. , Davidson Diane W.
Published: March 2006

A survey of two Amazonian melastome ant‐plants,Maieta guianensisandTococa bullifera, revealed a significant difference in plant size according to the species of ant inhabiting the plant. Plants withCrematogaster laevis, on average, were smaller than those withPheidole minutula(inM. guianensis)and those withAztecasp. (inT. bullifera).There is no evidence that these patterns were due either to the deterministic replacement ofC. laevisby another ant species during host‐plant ontogeny or to a habitat effect on plant growth rates coupled with colony survival. More likely, the smaller size ofC. laevisplants can be explained by its effects on host‐plant performance. Plants withC. laevislost their associated ant colonies more frequently than plants withP. minutulaandAztecasp. Plants that lost theirC. laeviseither died, or more commonly, were severely defoliated. Defoliated plants, once sprouted, tended to become recolonized, but such recolonizations were not deterministic so as to favor one species over another. Plants withC. laevisshowed similar, or only slightly greater, standing levels of herbivory than plants withP. minutulaorAztecasp. This suggests that whenC. laevisis present, it confers some degree of protection to its hosts. It was found that early in colony development, queens ofC. laevismoved off their host plants to build satellite nests in dead twigs on the ground, a behavior not seen in the other two species and one that possibly renders colonies more vulnerable to mortality from predation, flooding, or nest decay. Comparable 815N values inC. laevisandP. minutulaindicate that the two species are equally dependent on food supplied by the host plant.
Ant Defense of Euphyonarthex phyllostoma (Homoptera: Tettigometridae) during Trophobiotic Associations1
Authors: Dejean A. , Bourgoin T. , Orivel J.
Published: March 2006

During a five‐year field study, we made observations and conducted experiments to demonstrate unequivocally thatEuphyonarthex phyllostoma(Fulgoromorpha: Tettigometridae) is a myrmecophile. Isolated adults and colonies always were found in association with ants. Colonies were associated only withCamponotus brutusorC. acvapimensis(For‐micinae), whereas isolated adults were attended by ants belonging to several species of Formicinae, Dolichoderinae, and Myrmicinae. The size of the planthopper colonies reached higher levels when attended byC. brutusthan byC. acvapimensis.Experiments using ant exclusion showed that both ant species protected egg masses against parasitic wasps, but egg masses were less parasitized on trees occupied byC. brutusthan on those occupied byC. acvapimensis (P =0.0052). The production of egg masses by female hoppers was recorded only whenC. brutus, C. acvapimensis, or the myrmicine antMyrmicaria opaciventrisattended the hopper. In both former cases, the presence of ants influenced the aggregation of the nymphs as they dispersed when ants were excluded. The aggregation of the nymphs ensured chat they were properly attended. Parental care by the females was reduced to their presence above or close to the egg masses. In fact, specialized workers of the attending ant species protected the egg masses as well as nymphs.
Densidad Poblacional y Disponibilidad de Híbitat de la Danta de Montaña (Tapirus pinchaque) en los Andes Centrales de Colombia1
Authors: Cavelier Diego J. Lizcano M. y Jaime
Published: March 2006

En este estudió se estimó la densidad poblacional de Tapirus pinchaqueen un área de 7000 ha en el Parque Nacional Natural Los Nevados, Andes centrales de Colombia. Se midieron ocho variables (largo y ancho de la huella y largo y ancho de cada un de los dedos) en 110 huellas de la pata posterior izquierda de T: pinchaque. La información sobre huellas se analizó, mediante el método de agtupamiento UI'GMA y distancia Euclidiana de los “scores” obtenidos mediante un análisis de componentes priiicipales (ACP) con las ocho variables. La disponibilidad de hábitat se midió en un área de 147,000 ha documentada con fotografías aéreas de los años 50s y 80s. Los resultados del an4aAlisis de agrupamiento indicaron que en las 7000 ha habitan entre 11 y 15 individuos, con una densidad de un tapir par cada 551 ± 85 ha. Las mediciones de la cobertura boscosa dentro del área de 147000 ha mostraron que la superficie disponible para el tapir (bosques montanos y plantaciones forestales) aumentó en 18141 ha de 10s años 50s a los años 80s. El incremento del área, boscosa parece tener un efecto positivo sobre el tamaño de la población de T: pinchaque, ya qrie en antiguas áreas de pastizales hay existen bosques secundarios con abundantes hellas y excrementos de danta.
A Comparison of the Phyllostomid Bat Assemblages in Undisturbed Neotropical Forest and in Forest Fragments of a Slash‐and‐Burn Farming Mosaic in Petén, Guatemala1
Authors: Schulze Mark D. , Seavy Nathaniel E. , Whitacre David F.
Published: March 2006

Using mist nets, we compared phyllostomid bat ensembles of continuous mature forest in Tikal National Park, Guatemala, and of forest fragments in the nearby farming landscape. Of 20 species captured, 13 were shared between treatments, 4 were unique to continuous forest, and 3 were unique to forest fragments. Dominance–diversity curves were similar for the two treatments except that Sturnira lilium comprised 43 percent of captures in the forest fragments, resulting in greater dominance there. Capture rates (and presumably relative abundance) differed significantly between continuous forest and forest fragments, both in terms of species and feeding guilds. Sturnia lilium and Dermanura sp. were captured significantly more often in forest fragments than in continuous forest, whereas Artibeus jamaicensis, A. lituratus, and Centurio senex were taken significantly more often in continuous forest. Large frugivores accounted for a higher proportion of total captures in continuous forest than in forest fragments, whereas small frugivores showed the opposite pattern. By their abundances, Carollia perspicillata and S. lilium are indicators of forest disturbance. The relative abundances of large frugivores, which feed on large fruits of mature forest trees, and small frugivores, which feed on small‐fruited plants occurring in early succession, are an indicator of forest disturbance. Other groups, such as large insect‐ and vertebrate‐eating bats, because of their low capture rates, are impractical as indicators for rapid assessment of forest disturbance based on mist netting, but may prove especially vulnerable to forest fragmentation.
Nutrient Dynamics of Soil Derived from Different Parent Material on Barro Colorado Island, Panama1
Authors: Yavitt Joseph B.
Published: March 2006

I compared the concentrations of N, P, and S in both litter and mineral soil (0–15 cm depth) from three old‐growth, tropical moist forests on Barro Colorado Island (BCI), Panama. Each site was on a different substrate (i.e., parent material), but otherwise had similar climate, vegetation, and topography. There were no site differences in concentrations of N and S for either litter or soil. Concentrations of litter P and soil‐extractable P were greater for the andesite (igneous rock) site than for two sites on different sedimentary rocks; however, concentrations of several other litter and soil P fractions did not differ among sites. Patterns in soil P fractions suggested advanced soil development to the point that parent material has little control of P dynamics. Litter samples from each site, leached in the laboratory, released similar amounts of N, P, and S to the soil, indicating no differences in rates of turnover in the litter and in fluxes from litter into the mineral soil among sites. I expected more site differences in soil nutrient dynamics given vastly different parent materials and soil types (i.e., Oxisol vs. Alfisol) and very shallow soil on BCI that brings the parent material close to the plant root zone. Erosion and soil mixing may explain the uniformity in soil nutrient dynamics across the sites.
Lack of Ecotypic Differentiation: Plant Response to Elevation, Population Origin, and Wind in the Luquillo Mountains, Puerto Rico1
Authors: Fetched Ned , Cordero Roberto A. , Voltzow Janice
Published: March 2006

How important is ecotypic differentiation along elevational gradients in the tropics? Reciprocal transplants of two shrubs, Clibadium erosum (Asteraceae) and Psychotria berteriana (Rubiaceae), and a palm, Preitoea acuminata var. montana (Palmaceae), were used to test for the effect of environment and population origin on growth and physiology in the Luquillo Experimental Forest of Puerto Rico. Two sites were used, one at Pico del Este (1000 m in cloud forest) and one at El Verde (350 m in lower montane rain forest). At the cloud forest site, plastic barriers were erected around a subset of the plants to examine if protection from wind affected survival or biomass accumulation. Survival of C. erosum and P. berteriana was not affected by site, population origin, or the presence of barriers. For P. acuminata var. montana, survival was higher for plants with barriers, but not affected by site and population origin. Plants of C. erosum and P. berteriana at El Verde grew larger than at Pico del Este, but there was no effect of population origin or barrier treatment on biomass accumulation for these species. For P. acuminata var. montana, there was no effect of environment, population origin, or barrier treatment on biomass accumulation. Light‐saturated photosynthetic rate (Amax) of C. erosum, P. berteriana, and P. acuminata var. montana, as well as leaf anatomical characteristics of C. erosum, were unaffected by environment, population origin, and barrier treatment. On balance, there seems to be little evidence of ecotypic differentiation in these species along the gradient.
Post‐Hurricane Regeneration of Pioneer Plant Species in South Florida Subtropical Hardwood Hammocks1
Authors: Kwit Charles , Platt William J. , Slater Harold H.
Published: March 2006

After Hurricane Andrew crossed southern Florida (U.S.A.) on 24 August 1992, native and exotic pioneer species in subtropical hardwood forests (hammocks) regenerated from seed banks. Regeneration occurred in hammocks of metropolitan Dade County and the Long Pine Key region of Everglades National Park. The density of the native pioneer Trema micrantha was significantly higher in hammocks of Long Pine Key than in those of metropolitan Dade County. In contrast, the basal area of the exotic pioneer Carica papaya was greater in Dade County hammocks than Long Pine Key hammocks. Although T. micrantha tended to be restricted to areas of soil disturbance (tip‐up pits) formed by trees uprooted during Hurricane Andrew, especially in Long Pine Key, C. papaya was located throughout hammocks. These results suggest differences in the regeneration niches in which the native T. micrantha required more specific disruptions (i.e., both canopy and soil) than C. papaya (only removal of canopy) for establishment. A broad regeneration niche could in part account for the capability of an exotic species with a dormant seed bank to invade native subtropical forests following natural large‐scale disturbances.
Small Canopy Gaps Influence Plant Distributions in the Rain Forest Understory1
Authors: Svenning Jens–Christian
Published: March 2006

This study tested three hypotheses regarding how plants respond to the spatial heterogeneity in light availability in the rain forest understory: (1) understory plants occur preferentially in the lighter parts of the understory; (2) under–story palms are more shade tolerant than other understory plants; (3) rain forest plants differ in their ontogenetic response to understory light conditions. The study was carried out in old–growth rain forest in the Yasuní National Park, Amazonian Ecuador. The hypotheses were tested by comparing the distributions of 20 plant species (1454 individuals) over microsites with differing degrees of exposure to canopy gaps to the background distribution of these microsites in the forest. The gap exposure of a given microsite was described by an index based on the number and size of gaps in the canopy to which the site was exposed. Two plant height classes were studied: 0.80–2.49 and 2.50–5 m. The first and third hypotheses were accepted, while the second hypothesis was rejected. The results for the individual species corresponded well with what is known from earlier studies about the ecology of these species or close relatives, suggesting that the patterns observed can be generalized for Neotropical rain forests. Notably, the most abundant species in the study represent several different life history strategies. Thus, abundance in the rain forest understory can be achieved by several different strategies. This suggests that niche differentiation in terms of response to small changes in understory light conditions may be an important factor in the maintenance of the high local plant species richness of tropical rain forests.
Seedling and Sapling Dynamics of Treefall Pits in Puerto Rico1
Authors: Walker Lawrence R.
Published: March 2006

Seedling and sapling dynamics in a Puerto Rican rain forest were compared between forest understory and soil pits created by the uprooting of 27 trees during Hurricane Hugo. Soil N and P, organic matter, and soil moisture were lower and bulk densities were higher in the disturbed mineral soils of the pits than in undisturbed forest soils ten months after the hurricane. No differences in N and P levels were found in pit or forest soils under two trees with N–fixing symbionts (Inga laurinaandOrmosia krugii) compared to soils under a tree species without N–fixing sym–bionts (Casearia arborea), but other soil variables (Al, Fe, K) did vary by tree species. Forest plots had greater species richness of seedlings (<10 cm tall) and saplings (10–100 cm tall) than plots in the soil pits (and greater sapling densities), but seedling densities were similar between plot types. Species richness and seedling densities did not vary among plots associated with the three tree species, but some saplings were more abundant under trees of the same species. Pit size did not affect species richness or seedling and sapling densities. Recruitment of youngCecropia schreberianatrees (>5 m tall) 45 months after the hurricane was entirely from the soil pits, with no tree recruitment from forest plots. Larger soil pits had more tree recruitment than smaller pits. Defoliation of the forest by the hurricane created a large but temporary increase in light availability. Recruitment ofC. schreberianato the canopy occurred in gaps created by the treefall pits that had lower soil nutrients but provided a longer–term increase in light availability. Treefall pits also significantly altered the recruitment and mortality of many understory species in the Puerto Rican rain forest but did not alter species richness.