bluuebunny/crossref_metadata_2025 huggingface dataset:
Damage and Recovery of Cycas micronesica after Typhoon Paka1
Authors: Hirsh Heidi , Marier Thomas
Published: March 2006

Typhoon Paka passed over Guam on 16 December 1997, and caused extensive damage to the Cycas micronesica population. Defoliation reduced subsequent stem extension and leaf size, and increased synchrony of flushes. Decapitated plants developed numerous adventitious buds on damaged stems during recovery. Toppled plants were selectively browsed by feral deer and pigs. Epiphytes increased susceptibility to decapitation or toppling. Growth reduction was minimal and ephemeral, indicating that this species is highly resilient to tropical cyclone damage.
Spatial and Temporal Variation in Hydrochory in Amazonian Floodplain Forest1
Authors: Moegenburg Susan M.
Published: March 2006

ABSTRACT The hypothesis that water depth, plant species, and the presence of submerged substrates influence seed dispersal by water was tested in a whitewater tributary of the Tocantins River of the Amazon Basin. Seed dispersal was greatest when water depth was greatest, which occurred during the new moon. Seeds of buoyant species with smaller seeds required less water for dispersal than large seeded species. Submerged objects reduced the distance dispersed but not the probability of dispersal.
Effects of the Tropical Freshwater Shrimp Caridina weberi (Atyidae) on Leaf Litter Decomposition1
Authors: Williams Jennifer L.
Published: March 2006

Effects of feeding by atyid shrimp, Caridina weberi, on the rate of decomposition of leaf litter were studied in the Opunohu River, Moorea, French Polynesia. In a laboratory feeding experiment shrimp consumed microbially conditioned Hibiscus leaves, but in a field study shrimp did not affect the rate of decomposition of leaf litter. In this system, the rate of decomposition was influenced more by water discharge or by microbial activity than by shrimp.
Nitrogen Fixation in Bryophytes, Lichens, and Decaying Wood along a Soil‐age Gradient in Hawaiian Montane Rain Forest
Authors: Matzek Virginia , Vitousek Peter
Published: March 2006

We determined rates of acetylene reduction and estimated total nitrogen fixation associated with bryophytes, lichens, and decaying wood in Hawaiian montane rain forest sites with underlying substrate ranging in age from 300 to 4.1 million years. Potential N fixation ranged from ca 0.2 kg/ha annually in the 300‐year‐old site to ca 1 kg/ha annually in the 150,000‐year‐old site. Rates of acetylene reduction were surprisingly uniform along the soil‐age gradient, except for high rates in symbiotic/associative fixers at the 150,000‐year‐old site and in heterotrophic fixers at the 2100‐year‐old site. Low fixation at the youngest site, where plant production is known to be N‐limited, suggests that demand for N alone does not govern N fixation. Total N fixation was highest in sites with low N:P ratios in leaves and stem wood, perhaps because epiphytic bryophytes and lichens depend on canopy leachate for mineral nutrients and because heterotrophic fixation is partly controlled by nutrient supply in the decomposing substrate; however, differences in substrate cover, rather than in fixation rates, had the largest effect on the total N input from fixation at these sites.
Food Web Structure and Basal Resource Utilization along a Tropical Island Stream Continuum, Puerto Rico
Authors: March James G. , Pringle Catherine M.
Published: March 2006

Tropical stream food webs are thought to be based primarily on terrestrial resources (leaf litter) in small forested headwater streams and algal resources in larger, wider streams. In tropical island streams, the dominant consumers are often omnivorous freshwater shrimps that consume algae, leaf litter, insects, and other shrimps. We used stable isotope analysis to examine (1) the relative importance of terrestrial and algal‐based food resources to shrimps and other consumers and determine (2) if the relative importance of these food resources changed along the stream continuum. We examined δ15N and δ13C signatures of leaves, algae, macrophytes, biofilm, insects, snails, fishes, and shrimps at three sites (300, 90, and 10 m elev.) along the Río Espíritu Santo, which drains the Caribbean National Forest, Puerto Rico. Isotope signatures of basal resources were distinct at all sites. Results of two‐source δ13C mixing models suggest that shrimps relied more on algal‐based carbon resources than terrestrially derived resources at all three sites along the continuum. This study supports other recent findings in tropical streams, demonstrating that algal‐based resources are very important to stream consumers, even in small forested headwater streams. This study also demonstrates the importance of doing assimilation‐based analysis (i.e., stable isotope or trophic basis of production) when studying food webs.
Winds under the Rain Forest Canopy: The Aerodynamic Environment of Gliding Tree Frogs
Authors: McCay Michael G.
Published: March 2006

Movement of air under the canopy of a forest affects the gliding of animals such as frogs, snakes, geckos, and squirrels; the dispersal of pollen, seeds, and spores; as well as convective transport of heat and carbon dioxide. Wind speed profiles were measured under the canopy of a lowland rain forest during the morning, afternoon, and night at three sites in Costa Rica to determine the aerodynamic environment in which tree frogs maneuver while gliding. During the course of a day, average and maximum wind speeds were highest in the morning and midday, and lowest at night. Wind speeds under the canopy were highest near the top of the canopy and were lowest near the canopy floor in the morning and afternoon, and exhibited little variation with respect to height at night. Turbulence intensity (a common measure of gustiness) was constant (ca 1) for all times of day, heights in the canopy, and sites, but the absolute magnitudes of wind gust speeds were higher during the day than at night. Power spectral densities revealed that most of the variation in wind speeds occurred at frequencies that could potentially affect the gliding of tree frogs. Tree frogs (and many other gliding animals), however, glide at night and thereby avoid the higher wind speeds that occur by day. Computer simulations of the dynamic motions of frogs while gliding revealed that the night levels of wind gusts have little effect on the direction of gliding of tree frogs.
Do Tropical Storm Regimes Influence the Structure of Tropical Lowland Rain Forests?
Authors: Gouvenain Roland C. de , Silander John A.
Published: March 2006

It has been suggested that the average canopy height of Madagascar's lowland rain forests is shorter and the average tree density is greater than in other tropical lowland rain forests of the world. The cause was hypothesized to be frequent cyclone disturbances. We compared the structure of the lowland rain forests in Madagascar to the structure described in published accounts of other tropical lowland rain forests. We found that the eastern coastal lowland forests of Madagascar have short canopy heights relative to that of many other lowland tropical rain forests, and that these Malagasy forests also have relatively high tree densities. On a worldwide basis, there is a significant correlation between short forest canopies and occurrence of tropical cyclones. The association between high tree density and occurrence of tropical cyclones is valid for Africa, but the pattern does not hold up globally.

II a été conjecturé que la taille moyenne de la canopée des forȩts basses ombrophiles de Madagascar est moindre, et que la densité des arbres est plus grande, que pour d'autres forȩts tropicales ombrophiles du monde. L'hypothèse a été avancée que les perturbations fréquentes des cyclones en sont la cause. Nous avons compare la structure des forȩts ombrophiles de basse altitude de Madagascar avec la structure d'autres forȩts tropicales ombrophiles du monde. La hauteur de la canopée des foréts de I'est de Madagascar est relativement plus courte que celles de beaucoup d'autres forȩts tropicales humides de basse altitudes, et la densité des arbres est relativement élevée. A l'échelle globale, il y a une relation entre courte canopée et perturbations par les cyclones. La relation entre densité des arbres et perturbations par les cyclones est validée par cette étude seulement pour le continent Africain.
Variation in Growth and Demography of a Knob‐scaled Lizard (Xenosaurus newmanorum: Xenosauridae) from a Seasonal Tropical Environment in México
Authors: Lemos‐Espinal Julio A. , Smith Geoffrey R. , Ballinger Royce E.
Published: March 2006

We studied growth and demography in a population ofXenosaurus newmanoruma lizard that lives in rock crevices in the tropical cloud forests of Mexico. Growth rates varied with season (faster in the wet season) and year (faster in 1995 and 1997, slower in 1996 and 1999). Males and females did not differ in growth rate. Proportion of reproductive females varied from year to year, with 1996 having the lowest proportion of reproductive females (32.5%) compared to the other years (all >75%). The age/size structure changed slightly among years, but did not differ between the wet and dry seasons. On average, the sex ratio was female‐biased; however, the proportion of males in the population was greater in the dry season than in the wet season. Our results suggest that, like other lizards, growth and demographic characteristics of this population fluctuate with the proximate environment on both a seasonal and annual timescale.

Estudiamos los patrones de crecimiento y la demografia de una población deXenosaurus newmanorum, una especie de lagartija que vive en las grietas de las rocas de los bosques de niebla de México. La tasa de crecimiento corporal varió en función de la época del año (más rápida en la época húmeda), y en función del año (más rápida en 1995 y 1997, y más lenta en 1996 y 1999). No hubo diferencias significativas en las tasas de crecimiento corporal de machos y hembras. La proporción de hembras reproductivas varió de ańo a ańo, 1996 fue el ańo con menor proporción de hembras reproductivas (32.5%) comparado con el resto de los ańos (todos ellos > 75 %). La estructura de las clases de edad de esta población fluctuó levemente entre los años, pero no hubo diferencias entre las estaciones húmedas y secas. En promedio la proporción de sexos estuvo sesgada hacia las hembras; aunque la proporción de machos en la población fue mayor en la época seca que en la época húmeda. Nuestros resultados sugieren que, al igual que otras lagartijas, las características demográficas y de crecimiento corporal de esta población pueden fluctuar con base a factores próximos a escalas estacionales y anuales.
Age and Long‐term Growth of Trees in an Old‐growth Tropical Rain Forest, Based on Analyses of Tree Rings and 14C1
Authors: Fichtler Esther , Clark Deborah A. , Worbes Martin
Published: March 2006

In an old‐growth tropical wet forest at La Selva, Costa Rica, we combined radiocarbon (14C) dating and tree‐ring analysis to estimate the ages of large trees of canopy and emergent species spanning a broad range of wood densities and growth rates. We collected samples from the trunks of 29 fallen, dead individuals. We found that all eight sampled species formed visible growth rings, which varied considerably in distinctiveness. For five of the six species for which we combined wood anatomical studies with 14C‐dates (ring ages), the analyses demonstrated that growth rings were of annual formation. The oldest tree we found by direct ring counting was a Hymenolobium mesoamericanum Lima (Papilionaceae) specimen, with an age of ca. 530 years at the time of death. All other sampled individuals, including very large trees of slow‐growing species, had died at ages between 200 and 300 years. These results show that, even in an everwet tropical rain forest, tree growth of many species can be rhythmic, with an annual periodicity. This study thus raises the possibility of extending tree‐ring analyses throughout the tropical forest types lacking a strong dry season or annual flooding. Our findings and similar measurements from other tropical forests indicate that the maximum ages of tropical emergent trees are unlikely to be much greater than 600 years, and that these trees often die earlier from various natural causes.
Flower Color, Hummingbird Pollination, and Habitat Irradiance in Four Neotropical Forests1
Authors: Altshuler Douglas L.
Published: March 2006

Pollinator visual systems differ considerably among broad groupings such as bees, bats, and birds, and it has been proposed that factors shaping the diversity of flower color in tropical plants include differences in pollinator perceptual abilities. Within the pollinators of the Neotropics, one major difference between taxa is that hummingbirds perceive color well across a broad range of wavelengths from 300–660 nm whereas most bees perceive color well over a narrower range spanning 300–550 nm. Thus, hummingbirds can see red and other long‐wavelength reflection much better than bees. Another factor that could potentially influence flower color in tropical forests is the difference in light availability among habitats such as gaps, canopy, and forest understory. I conducted a survey of floral color in four Neotropical forests using a portable spectroradiometer to provide an unbiased measure of color reflectance. The primary pollinator agents and light habitats of each plant species were classified using primary literature or accounts of direct observations by experts. Flower color was not influenced by differences in light availability between open and closed habitats but was influenced by pollinator visual systems. Specifically, insect flowers reflected across a broad range of the spectrum but hummingbird flowers reflected mostly long‐wavelength light (typically median wavelength <585 nm). Thus, hummingbird‐pollinated flowers are not tuned specifically to hummingbird color sensitivity but instead may decrease conspicuousness to bees and other insects that have poor visual sensitivity to long‐wavelength color.
Genetic Variation of Mantled Howler Monkeys (Alouatta palliata) from Costa Rica1
Authors: Zaldivar Maria E. , Glander Kenneth E. , Rocha Oscar , Aguilar Gabriel , Vargas Elida , Gutierrez‐Espeleta Gustavo A. , Sanchez Ronald
Published: March 2006

We examined genetic diversity of howler monkeys (Alouatta palliata) from Costa Rica. Blood samples of howler monkeys were collected at various locations in Costa Rica, and electrophoresis of total plasma proteins yielded no variation. We also conducted starch gel electrophoresis of red cell isozymes and did not find variation for any of the 14 loci analyzed (i.e., ACP, ADA, CA2, EST, GPI, IDH, LDH‐1, LDH‐2, MDH, PGD, PGM‐1, PGM‐2, SOD, and TPI). These findings were compared with the levels of genetic variation for A. seniculus and A. belzebul from one Brazilian population. Four of the 14 isozymes (ADA, GPI, PGD, and SOD) showed more than one allele for these species. Both A. seniculus and A. belzebul from Brazil showed similar levels of genetic variation. The potential causes of the low genetic variation in A. palliata from Costa Rica are discussed.
Succession and Micro‐elevation Effects on Seedling Establishment of Calophyllum brasiliense Camb. (Clusiaceae) in an Amazonian River Meander Forest1
Authors: King Rachel T.
Published: March 2006

I investigated the effects of successional stage and micro‐elevation on seedling establishment of Calophyllum brasiliense (Clusiaceae), a common canopy tree of seasonally flooded lowland forest along the Manú River meander zone in southeastern Peru. To compare seedling establishment between microhabitat types, I planted C. brasiliense seeds in a fully crossed experimental design of three successional stages (early, mid, and mature) and two micro‐elevations (levees and backwaters). Seedling establishment success in this study was affected by both successional stage and micro‐elevation, but micro‐elevation was most important in mid‐successional habitats. In general, seedlings in early succession experienced better conditions than in mature forest; light levels were higher, herbivory lower, and seedling growth higher. In mid‐successional forest, micro‐elevation determined habitat quality; backwaters had higher light levels, lower herbivory, and higher seedling growth and survival than levees. Mid‐successional backwaters were similar in quality to early successional forest for seedling establishment, while levees in that same successional stage were the poorest microhabitats for establishment. Although mid‐successional backwaters are similar to early succession for seedling establishment, in the long run, seedlings that establish in mid‐succession have a lower chance of reaching reproductive size before their habitat ages to mature forest than members of their cohort that established in early succession. I hypothesize that successful recruitment for C. brasiliense in the Manú River meander system requires dispersal to early successional habitat.
Foliar C:N Ratio of Ferns along an Andean Elevational Gradient1
Authors: Wegner Caroline , Wunderlich Meike , Kessler Michael , Schawe Marcus
Published: March 2006

We studied the concentration of leaf N and C among 183 fern species along an elevational gradient at 1700 to 3400 m in humid montane forest in the Bolivian Andes at different levels of taxonomic resolution. For two species of Elaphoglossum sampled 8 and 14 times, respectively, there were no elevational trends. Similarly, a contrast of 22 species with wide elevational amplitudes sampled at their highest and lowest locations did not show any change in C or N contents, or in C:N ratios with elevation. At the community level, however, the mean values of C:N ratios for (a) all species found at a given elevation showed a significant decline with increasing elevation and (b) among epiphytic species, higher ratios (i.e., lower relative N content) than among terrestrial species at the same elevation. These trends were opposite to those of the upper soil layer, in which C:N ratios increased with elevation.
Lizard Assemblages from Natural Cerrado Enclaves in Southwestern Amazonia: The Role of Stochastic Extinctions and Isolation1
Authors: Gainsbury Alison Melissa , Colli Guarino Rinaldi
Published: March 2006

We used null model analyses to investigate the existence of structure in lizard assemblages from open vegetation enclaves in Rondónia, southwestern Amazonia, in relation to species richness, species co‐occurrence, diet, and size overlap. These enclaves presumably have been isolated since the Holocene, providing a history of long‐term isolation. We assumed that the presence of structure in lizard assemblages from the Rondónia enclaves is consistent with the notion that extinctions are a deterministic process, some species being more prone to extinction than others. We grouped enclaves into four categories: latosoil cerrado, sandy cerrado, transitional forest, and rocky field. We collected 14 Cerrado lizard species, consisting of five families in all sampled areas. Analyses of species richness, co‐occurrence, diet overlap, and size overlap patterns suggested lack of organization in the assemblages. The assemblages from the rocky fields of Guajarí–Mirim and the sandy cerrados in Vilhena were significantly structured in diet overlap, whereas the remaining assemblages lacked structure. This probably resulted from phylogenetic inertia and not from ecological interactions. Our results suggest that extinctions proceeded in a stochastic fashion and that historical factors had a dominant role in shaping lizard assemblages in detriment of present‐day ecological factors. In addition, we identified endemic species in the enclaves as well as a tight association between unique ecogeographic features of the landscape and species occurrences. We propose that conservation measures in the region must adequately preserve these features to ensure the survival of the species.
Morphological Variation in Two Facultative Epiphytic Bromeliads Growing on the Floor of a Swamp Forest1
Authors: de Freitas Cecília A. , Scarano Fabio R. , Blesboer David D.
Published: March 2006

The epiphytic tank bromeliads Nidularium procerum (a CAM plant) and TV. innocentii (a C3 plant) can be found as terrestrial plants in the understory of a Brazilian swamp forest. They occur in segregated patches differing in light and flooding regimes; however, plants of each species are found in the other species preferred habitat in a narrow boundary zone where the two populations meet. Although ecophysiological factors were previously thought to dictate the distribution of these species at this site, we suggest that their current distribution is probably related to colonization history and subsequent competition for space.
New Perspectives in Comparative Ecology of Neotropical Rain Forests: Reflections on the Past, Present, and Future
Authors: Powers Jennifer S.
Published: March 2006

In an effort to understand variations in ecological patterns among lowland tropical rain forests, Alwyn Gentry and colleagues synthesized data sets from four of the premier Neotropical field stations–La Selva (Costa Rica), Barro Colorado Island (Panama), Cocha Cashu (Peru), and the Biological Dynamics of Forest Fragmentation Project (Brazil). To promote the kind of geographically comparative tropical ecology advocated in the 1990 Gentry book, the Organization for Tropical Studies and the Smithsonian Tropical Research Institute organized a course in 2001 that visited each of these field stations. Papers from some of the studies resulting from this course are highlighted in this special section. These studies are notable for the consistent methods applied across forests, and they underscore the acute need and bright future for comparative tropical ecology. Key site characteristics for each of the field stations are summarized here.

En un esfuerzo de entender las variaciones en patrones ecológicos entre selvas tropicales de bajura, Alwyn Gentry y colegas sintetizaron bases de datos en las cuatro principales estaciones biológicos del Neotrópico: La Selva (Costa Rica), Barro Colorado Island (Panamá), Cocha Cashu (Perú), y el Proyecto de Dinámica Biológica de Fragmentación de Bosque (Brasil). Con el fin de promover el estudio ecologico tropical comparativa a nivel geográfico recomendada por Gentry en 1990 la Organización para Estudios Tropicales y el Smithsonian Tropical Research Institution organizaron un curso en el año 2001, el cual visitó cada una de éstas estaciones. Los artículos científicos de algunos de los estudios producto de este curso se presentan en esta sección especial. Estos estudios son notables debido a la consistencia en los metodología aplicada a través de los cuatro sitios. Asimismo, estos estudios denotan la necesidad y el potencial de Uevar a cabo mas investigación a nivel de ecología tropical comparativa. Caracteristicas importantes para cada una de las estaciones de campo son resumidos en esta sección.
Efectos de la Fragmentatión Sobre la Aborción y Depredación de Semillas en el Chaco Serrano
Authors: Chacoff Natacha P. , Morales Juan M. , Vaquera Maria del P.
Published: March 2006

Las interacciones entre plantas e insectos pueden ser afectadas por la fragmentacion de los hábitats. En este estudio, realizado en el Chaco Serrano de Argentina, investigamos los efectos de la fragmentación sobre la cantidad de semillas abortadas, depredadas y sanas de Acacia aroma y Cercidium praecox. Encontramos que los efectos de la fragmentaci6n fueron diferentes en cada especie. A medida que se redujo el área del fragmento, aumentó el número de semillas abortadas en A. aroma, mientras que la depredación pre‐dispersión disminuyó y la cantidad de semillas sanas aumento en C. praecox. El aumento de semillas abortadas en los fragmentos pequeños no produjo un número menor de semillas sanas disponibles para la dispersión. En las dos especies, los niveles máximos de depredacion por parte de brúquidos fueron cercanos al 35 por ciento, mientras que la aborción de semillas no superó el 7 por ciento. Debido a los altos niveles de daño y la especificidad de los brúquidos, los cambios producidos por la fragmentacióon pueden ser muy importantes para las poblaciones de estas dos especies. Los efectos de la fragmentación sobre la polinización y la depredación pre‐dispersión de semillas de estas fabáceas pueden generar una mayor disponibilidad de semillas para su posterior dispersión en ambientes fragmentados.

Habitat fragmentation can have consequences on plant reproduction through several interactions with insects. We studied the effects of habitat fragmentation in die proportion of aborted, predated and undamaged seeds of Acacia aroma and Cercidium praecox. We performed this study in the Chaco Serrano of Argentina. We found that fragmentation effects differed between species. In small patches, the number of aborted seeds of A. aroma increased and the number of pre–dispersal predated seeds and undamaged seeds of C. praecox decreased and increased, respectively. However, higher numbers of aborted seeds in small patches did not lead to fewer available seeds for dispersion. For these species, seed predation by bruchids was about 35 percent and aborted seeds were around 7 percent. Because of the elevated levels of damage and the high specificity of bruchids, the changes caused by habitat fragmentation may be very important for the populations of these two species. Habitat fragmentation effects on pollination and pre–dispersal seed predation of these legumes may determine higher availability of seeds for dispersion in fragmented habitats.
Myrmecophagy in Mycetophiloidea (Diptera): Note on a Keroplatidae from Africa1,2
Authors: Debout Gabriel
Published: March 2006

Information on an undescribed keroplatid fly (tribe Orfeliini) from Cameroon is presented. Its myrmecophagous larvae live in hollow stems of an understory myrmecophytic tree. Data on the biology of this fly and its interaction with one of the plant's strictly associated ant species Cataulacus mckeyi (Myrmicinae) showed that the number of keroplatid larvae per tree was not limited by occupation competition with the ant. Through predation on workers, keroplatid larvae may have a sizeable impact on colonies of C. mckeyi.

Nous préntons des informations sur une espèce non‐décrite de Keroplatidae (tribu Orfeliini), au Cameroun. Les larves myrmécophages se développent dans les tiges creuses 7dcarune myrmécophyte de sous‐bois. Des données sur la biologie de cette espèce et son interaction avec lcarune des fourmis‐ho̧tes de cette plante, Cataulacus mckeyi, montrent que le nombre de larves par arbre n'est pas limité par la compétition pour lcaroccupation avec la fourmi. En prédatant les ouvrières, ces larves ont un impact potentiellement important sur les colonies de C. mckeyi.
Alien Abduction: Disruption of Native Plant‐Pollinator Interactions by Invasive Species
Authors: Ghazoul Jaboury
Published: March 2006

The indirect impacts of Shorea siamensis‐logging on the reproductive ecology of Dipterocarpus obtusifolius, a self‐incompatible butterfly‐, moth‐, and bird‐pollinated tree, were studied in tropical dry forest in Thailand. Pollinator activity at D. obtusifolius trees and subsequent seed production were recorded in three forest areas subject to differing intensities of S. siamensis extraction. The pollinator and plant understory communities in these areas were also noted. Forest areas subject to high S. siamensis extraction intensities had very high understory flowering plant cover, dominated by the exotic invader Chromolaena odorata. Activity of butterfly pollinators at D. obtusifolius trees decreased in these disturbed areas, although their abundance remained comparable to other forest areas subject to only moderate or no extraction. For sphingid moth pollinators, there was no difference across differentially disturbed forest areas in either abundance or in the proportion bearing pollen. Pollinator activity by birds increased at highly disturbed locations but was not sufficient to offset a decline in overall pollinator activity at D. obtusifolius canopies in areas of heavy 5. siamensis extraction. Thus, extraction of S. siamensis indirectly affected the pollination of D. obtusifolius, primarily by causing changes in the foraging behavior of butterfly pollinators rather than their abundance. A shift in the relative abundance of floral nectar resources from the canopy to the understory, a consequence of 5. siamensis extraction and invasion by C. odorata, led to a parallel shift in foraging location of the principal diurnal pollinators, the butterflies, toward the understory. Despite reduced pollination at disturbed sites, behavioral changes did not translate into a D. obtusifolius seed set effect, possibly because pollination by birds (or moths) at the disturbed site compensated for reduced butterfly pollination.
Extracellular Enzyme Activities and Carbon Chemistry as Drivers of Tropical Plant Litter Decomposition
Authors: Allison Steven D. , Vitousek Peter M.
Published: March 2006

Litter quality parameters such as nitrogen and lignin content correlate with decomposition rates at coarse scales, but fine‐scale mechanisms driving litter decomposition have proven more difficult to generalize. One potentially important driver of decomposition is the activity of extracellular enzymes that catalyze the degradation of complex compounds present in litter. To address the importance of this mechanism, we collected 15 Hawaiian plant litter types and decomposed them in fertilized and control plots for up to two years. We measured litter nutrient content and carbon chemistry prior to decomposition, as well as extracellular enzyme activities, mass loss, and litter nutrient content over time. We found that water‐soluble carbon content, cellobiohydrolase activities, and polyphenol oxidase activities were significantly correlated with mass loss. Enzyme activities and decomposition rate constants both varied significantly by litter type, and fertilization increased mass loss rates in five litter types. Some litter types that decayed faster under fertilization also showed time‐dependent increases in carbon‐degrading enzyme activities, but others decayed faster independent of enzyme changes. These results suggest that extracellular enzyme activities partially determine litter decomposition rates, but high soluble carbon content may circumvent the requirement for enzyme‐catalyzed decomposition.
Observations on the Ecology of Weaver Ants (Oecophylla smaragdina Fabricius) in a Thai Mangrove Ecosystem and Their Effect on Herbivory of Rhizophora mucronata Lam.
Authors: Offenberg Joachim , Havanon Sopon , Aksornkoae Sanit , Macintosh Donald J. , Nielsen Mogens Gissel
Published: March 2006

Ants of the genus Oecophylla are predators of other insects and are able to protect a variety of terrestrial plants against pest insects; however, observations on the ecology of these ants in mangrove forests are lacking. General observations on the ecology of Oecophylla smaragdina were carried out in a Thai mangrove forest to determine if these ants can protect their host plants in less favorable mangrove habitats. Leaf herbivory and the density of O. smaragdina ants were measured on Rhizophora mucronata trees at two sites. The results showed a negative correlation between ant density and herbivory. At both sites, the mean percent damaged leaf area was more than four times higher on trees without ants compared to “ant‐trees.” A significant negative correlation was found between tree mean percent leaf damage and the density of ants on the tree. Furthermore, on trees with ants, there was less herbivory on leaves close to ant nests compared to other leaves on the tree. Most damage was caused by chrysomelid beetles (62%) and sesarmid crabs (25%) and both types of herbivory were significantly reduced on ant‐trees.
Fruit, Minerals, and Forest Elephant Trails: Do All Roads Lead to Rome?
Authors: Blake Stephen , Inkamba‐Nkulu Clement
Published: March 2006

Tropical forests are among the most heterogeneous environments on earth, and food resources for many animals are patchy both in time and space. In Africa's equatorial forest, permanent trails created and maintained by forest elephants are conspicuous features. Trails may be several meters wide and continue for tens of kilometers. Speculation on which resources determine the distribution of trails has identified fruit, browse, and mineral deposits as candidates. In this study, the relationships between these habitat variables and elephant trails were investigated. The size of individual trails and the density of the trail system increased dramatically with proximity to mineral deposits. Fruit tree basal area decreased with perpendicular distance from trails, while that of non‐fruit trees did not. Fruit tree abundance and basal area were significantly higher on trail intersections than random sites and increased with intersection size. No relationship was found between monocotyledon browse abundance and elephant trail system characteristics. Clumped resources, which are at least partially reliable, provide a high nutritional payback, and are not rapidly depleted and can thus be visited repeatedly, appear to influence permanent trail formation by forest elephants. Permanent trails may allow naive individuals or those with imperfect knowledge to locate and acquire important resources.
Arboreal Ant Species Richness in Primary Forest, Secondary Forest, and Pasture Habitats of a Tropical Montane Landscape1
Authors: Schonberg Lisa A. , Longino John T. , Nadkarni Nalini M. , Yanoviak Stephen P. , Gering Jon C.
Published: March 2006

Canopy invertebrates may reflect changes in tree structure and microhabitat that are brought about by human activities. We used the canopy fogging method to collect ants from tree crowns in primary forest, secondary forest, and pasture in a Neotropical cloud forest landscape. The total number of species collected was similar in primary forest (21) and pasture (20) habitats, but lower in secondary forest (9). Lower diversity in secondary forest was caused by lower species density (no. of species per sample). Rarefaction curves based on number of species occurrences suggest similar community species richness among the three habitats. This study has implications for conservation of tropical montane habitats in two ways. First, arboreal ant species density is reduced if secondary forest replaces primary forest, which increases the chance of extinction among rare species. Second, pasture trees may serve as repositories of primary forest ant communities due to similar tree structure.

Los disturbios antropogénicos sobre la estructura de los árboles y microhabitat afectara la diversidad de invertebrados del dosel. Se usó la técnica de fumigación para colectar hormigas de las copas de los árboles en tres ambientes en un bosque nuboso Neotropical; bosque primario, bosque secundario, y pastizal. La cantidad total de especies colectadas fue similar entre el bosque primario (21) y el pastizal (20), pero menor en el bosque secundario (9). La baja riqueza en el bosque secundario fue consequencia de menor densidad de especies (cantidad de especies por muestra). Las curvas de rarefacción basada en presencia/ausencia de especies sugieren que la riqueza a nivel de la comunidad es similar entre los tres tipos de hábitat. Estos resultados puede aportar a la conservación de los hábitat tropicales nubosos de dos maneras. Primero, sugieren que la densidad de especies de hormigas es baja cuando un bosque primario es reemplazado por un bosque secundario. Segundo, los árboles grandes de pastizales pueden servir como refugios para las comunidades de hormigas, debido a que presentan similitud con la estructura de un bosque primario.
Granivorous Birds as Potentially Important Post‐dispersal Seed Predators in a Brazilian Forest Fragment1
Authors: Pizo Marco A. , Vieira Emerson M.
Published: March 2006

In tropical forests, rodents exert a prominent role as post‐dispersal seed predators, while other vertebrates apparently have a minor effect on seed predation. In some forest fragments in southeast Brazil, however, the density of rodents is unusually low, whereas terrestrial granivorous birds are abundant. In this study, we used seeds of a second‐growth tree (Cretan priscus, Euphorbiaceae) to investigate experimentally the relative importance of rodents and birds as seed predators in a forest fragment. We also estimated the density of terrestrial granivorous birds and trapped small mammals. Results indicate that, as a consequence of decreased rodent population and increased bird abundance, the latter are at least as important as the former as the main post‐dispersal seed predators ofC. priscus.We interpret such apparent imbalance in the interaction betweenC. priscusand their seed predators as a possible consequence of forest fragmentation.

Em florestas tropicals, enquanto os roedores figuram entre os principals predadores pós‐dispersão de sementes, outros vertebrados desempenham mais raramente este papel. Em alguns fragmentos da floresta no sudeste do Brasil, no entanto, a densidade de roedores é bastante baixa, enquanto aves granivoras terrestres são abundantes. Neste estudo nós usamos sementes de uma árvore caracterfstica de vegetaçáo secundaria (Croton priscus, Euphorbiaceae) para investigar experimentalmente a importancia relativa dos roedores e das aves granfvoras como predadores de sementes em um destes fragmentos da floresta. Concomitantemente também estimamos a densidade das aves granivoras e a abunda̧ancia de pequenos mamiferos. Os resultados obtidos indicaram que, como conseqüȩncia da baixa abunda̧ancia de roedores e alta abunda̧ncia de aves granivoras, estas sa̧o ao rnenos ta̧o importantes quanto os roedores como predadores pós‐dispersa̧o das sementes deC.priscus. Interpretamos este padra̧o pouco usual na interaça̧o enterC. priscuse os predadores de suas sementes como uma possivel conseqüȩnica da fragmentação floresta.
Decomposition of Greenfall vs. Senescent Foliage in a Tropical Forest Ecosystem in Puerto Rico1
Authors: Fonte Steven J. , Schowalter Timothy D.
Published: March 2006

In many forest ecosystems, green leaf deposition (greenfall) constitutes an enrichment over background levels of litterfall nutrients and may therefore influence key ecosystem processes. This study examined the litter quality and decomposition rates of green leaves compared to senescent litterfall for four dominant tree species(Dacryodes excelsa, Manilkara bidentata, Guarea guidonia, andCecropia schreberiana)in a lower montane rain forest at El Verde Field Station, Luquillo Experimental Forest, Puerto Rico. Green leaves from the canopy and freshly senesced leaves from the forest floor were analyzed for carbon, nitrogen, and fiber and placed in litterbags in the field for up to 16 weeks. Green leaves displayed significantly higher rates of decomposition than did senescent litter among all four species. Green leaves also had significantly higher nitrogen concentrations and lower lignin to nitrogen ratios compared to senescent leaves. These results suggest that greenfall may have a major influence on decay processes and nutrient cycling in forests that experience large‐scale green foliage removal.

En muchos ecosistemas forestales, la adición de hojas verdes constituye en altos niveles de enriquecimiento de nutrientes de hojarasca y por lo tanto puede influir en los procesos fundamentales de un ecosistema. Este estudio examina la calidad de hojarasca y la tasa de descomposición de hojas verdes comparado con hojas senescentes recién caidas de cuatro especies dominantes (Dacryodes excelsa, Manilkara bidentata, Guarea guidonia, y Cecropia schreberiana) en un bosque lluvioso montanoso bajo en la estación El Verde, Bosque Experimental de Luquillo, Puerto Rico. Hojas verdes de la copa de los árboles y hojas senescentes recién caidas en el suelo del bosque fueron analizadas para carbono, nitrógeno, y fibra, y fueron colocadas en bolsas de basura en el suelo del bosque por 16 semanas. Las hojas verdes mostraron tasas de descomposición significativamente mayores que la hojarasca senescente entre todas las cuatro especies. Las hojas verdes muestran significativamente mayores concentraciones de nitrógeno y menores relaciones de lignina‐nitrógeno comparado con las hojas senescentes. Estos resultados sugieren que la cafda de hojas verdes puede influir en forma significativa en los procesos de descomposici6n y ciclaje de nutrientes en bosques que experimentan a gran escala remoci6n de follaje verde.
Avian Geophagy and Soil Characteristics in Southeastern Peru
Authors: Brightsmith Donald J. , Muñoz‐Najar Romina Aramburú
Published: March 2006

We observed ten species of psittacids, three species of columbids, and two species of cracids consuming soil from banks of the lower Tambopata River in southeastern Peru. Our study used observations and soil analyses from eight exposed riverbank sections to test the predictions of three models to determine why birds consume clay: mechanical aid to digestion (grit), adsorption of dietary toxins, and mineral supplementation. We found that preferred soils were deficient in particles large enough to aid in the mechanical breakdown of food and help digestion. Percent clay content and cation exchange capacity (CEC), both predicted to correlate with adsorption of toxins, did not differ between used and unused sites as had been found in a similar study. Instead, preferred soils were more saline and had higher concentrations of exchangeable sodium. This suggests that the choice of soils at our site was based primarily on sodium content. Birds may be using the heavy, plastic texture of soils rich in clays and high in exchangeable sodium as a proximal cue for soil selection. Our findings suggest that avian soil selection decisions depend on the range of available soil characteristics.

Observamos diez especies de Psittasidos, trés especies de Columbidos, y dos especies de Cracidos consumiendo suelo de los bancos del bajo Rio Tambopata en el sureste del Perú. Nuestro estudio utiliza observaciones de aves y análisis de suelos de ocho secciones expuestas de los bancos de rio para probar las predicciones de tres modelos de porque las aves consumen arcilla: ayuda mecánica para la digestión (arena triturada), adsorción de toxinas en la dieta, y suplemento mineral. Encontramos que los suelos preferidos eran deficientes en particulas lo suficientemente grandes como para ayudar en la trituración mecánica del alimento y ayudar a la digestión. El porcentaje de contenido de arcilla y la capacidad de intercambio catiónico (CIC), ambos esperados para correlacionar con la adsorción de toxinas, no varió entre sitios usados y no usados como ha sido encontrado en un estudio similar. En cambio, los suelos preferidos fueron más salinos y con mayor concentracion de sodio intercambiable. Esto sugiere que la selección de suelos en nuestro sitio de estudio está basado principalmente en el contenido de sodio. Las aves pueden estar usando las texturas densas y plásticas de los suelos ricos en arcillas con alto contenido de sodio intercambiable como una señal próxima para la selección del suelo. Nuestros resultados sugieren que las decisiones de selección de suelos por las aves depende del rango de caracteristicas de suelos disponibles.
Respiratory Ecology of Aquatic Macroinvertebratestween dissolved oxygen and invertebrate1
Authors: Chapman Lauren J. , Scnelder Kimberly R. , Apodaca Chrissy , Chapma Collin A.
Published: March 2006

Hypoxia (oxygen scarcity) is widespread in tropical freshwaters, particularly in dense swamps, and may be an important factor structuring benthic macroinvertebrate communities. Macroinvertebrates show a diversity of respiratory modes ranging from atmospheric breathing to tracheal gill breathing, and these adaptations affect their ability to use hypoxic water. The objectives of this study were to (a) describe the benthic macroinvertebrate community from ten swamp and river sires in Kibale National Park, Uganda, (b) determine the degree to which dissolved oxygen explains variation in abundance of respiratory groups (taxa with a similar respiratory mode) among sites, and (c) rest for significant seasonal variation in the abundance of the numerically dominant respiratory groups. Macroinvertebrates from monthly collections over a two‐year period were identified to the lowest taxonomic level necessary to place them in functional respiratory groups. Across all sites, both the relative and absolute abundance of atmospheric breathers (e.5, pulmonate snails and nepids) and mantle/ctenidia breathers (primarily fingernail clams) were negatively correlated with dissolved oxygen, while the abundance of tracheal gill breathers (e.g. anisopterans and zygopterans) was positively correlated with dissolved oxygen. We did not detect significant seasonal trends in catch per unit effort of numerically dominant respiratory groups. Dissolved oxygen concentration was a good predictor of the abundance of some respiratory groups and may be a key factor in maintaining the structure and diversity of these assemblages.
The privilege against self-incrimination in competition investigations: theoretical foundations and practical implications
Authors: MacCulloch Angus
Published: March 2006

This paper examines the historical and theoretical basis of the privilege against self-incrimination and the case-law regarding the privilege before the UK and European courts in order to understand better the development of the privilege in relation to competition investigations in the UK and EU. The historical and theoretical basis of the privilege indicates that the privilege is a relatively modern legal creation and a number of theoretical bases are offered to justify its existence. The theoretical justifications assist in a better understanding of the extant case-law, but indicate that some of the distinctions drawn between categories of protected information have no clear basis. The paper goes on to examine the difference between self-incrimination and self-accusation, the extension of ‘human’ rights to corporate entities, and the existence of a privilege as a ‘functional necessity’. Finally the paper makes some suggestions about the type of information that might be sought legitimately in competition investigations and those requests that might be challenged.
Patronising the mentally disordered? Social landlords and the control of ‘anti-social behaviour’ under the Disability Discrimination Act 1995
Authors: Cobb Neil
Published: March 2006

The 2004 decision of the Court of Appeal inManchester City Council v Romano and Samarihighlighted the unexpected impact of the Disability Discrimination Act 1995 (DDA) upon the control of anti-social behaviour by social landlords where that conduct is caused by a mental disorder. This paper positions the legislation against the backdrop of advanced liberal housing policy, and its concern with the management of risk and the fostering of individual responsibility among tenants. In particular, it explores the possible criticism that, by preventing landlords in certain circumstances from taking action against the mentally disordered on grounds of their anti-social conduct, the DDA patronises those individuals by denying them the opportunity to take responsibility for their actions.