Beyond Paradise----Meeting the Challenges in Tropical Biology in the 21st Century
Kamaljit S. Bawa, W. John Kress, and Nalini M. Nadkarni
(Click for Abstract)
Extracellular Enzyme Activities and Carbon Chemistry as Drivers of Tropical Plant Litter Decomposition
Steven D. Allison and Peter M. Vitousek
(Click for Abstract)
Forty Years of Tropical Forest Recovery from Agriculture: Structure and Floristics of Secondary and Old-growth Riparian Forests in the Dominican Republic
Patrick H. Martin, Ruth E. Sherman, and Timothy J. Fahey
(Click for Abstract)(Resumen Haga Clic Aquí)
Levels of Herbivory in Two Costa Rican Rain Forests: Implications for Studies of Fossil Herbivory
Dena M. Smith and Cesar R. Nufio
(Click for Abstract)(Resumen Haga Clic Aquí)
Herbivory by Leaf-Cutting Ants: Nutrient Balance between Harvested and Refuse Material
Enrique H. Bucher, Victoria Marchesini, and Adriana Abril
(Click for Abstract)(Resumen Haga Clic Aquí)
Does Mangrove Leaf Chemistry Help Explain Crab Herbivory Patterns?
Amy A. Erickson, Susan S. Bell, and Clinton J. Dawes
(Click for Abstract)
Observations on the ecology of weaver ants (Oecophylla smaragdina Fabricius) in a Thai mangrove ecosystem and their effect on herbivory of Rhizophora mucronata Lam.
Joachim Offenberg, Sopon Havanon, Sanit Aksornkoae, Donald J. MacIntosh, and Mogens Gissel Nielsen
(Click for Abstract)
Life History and Demography of Cephaloleia fenestrata (Hispinae: Chrysomelidae: Coleoptera)
Derek Marley Johnson
(Click for Abstract)(Resumen Haga Clic Aquí)
Differential Wing Strength in Pierella Butterflies (Nymphalidae, Satyrinae) Supports the Deflection Hypothesis
Ryan I. Hill and Jarol F. Vaca
(Click for Abstract)(Resumen Haga Clic Aquí)
Introduced honeybees (Apis mellifera) reduce pollination success without affecting the floral resource taken by native pollinators
Roselaini Mendes do Carmo, Edivani Villaron Franceschinelli, and Fernando Amaral da Silveira
(Click for Abstract)(Resumen Haga Clic Aquí)
Flower mites of Calyptrogyne ghiesbreghtiana (Arecaceae): Evidence for dispersal using pollinating bats
Marco Tschapka and Saul A. Cunningham
(Click for Abstract)(Resumen Haga Clic Aquí)
Population Dynamics of a Resident Colony of Leptonycteris curasoae (Chiroptera: Phyllostomidae) in Central Mexico
Cristobal Galindo G., Adalinda Sánchez Q., Ramón H. Quijano and L. Gerardo Herrera M.
(Click for Abstract)(Resumen Haga Clic Aquí)
Fruit, Minerals and Forest Elephant Trails: Do All Roads Lead to Rome?
Stephen Blake and Clement Inkamba-Nkulu
(Click for Abstract)
Arboreal Ant Species Richness in Primary Forest, Secondary Forest, and Pasture Habitats of a Tropical Montane Landscape
Lisa A. Schonberg, John T. Longino, Nalini M. Nadkarni, Stephen P. Yanoviak and Jon C. Gering
(Click for Abstract)(Resumen Haga Clic Aquí)
Physical Damage in Relation to Carbon Allocation Strategies of Tropical Forest Tree Saplings
Pauw et al.
(Click for Abstract)(Resumen Haga Clic Aquí)
The Flexible Breeding System of Werauhia sintenisii, a Cloud Forest Bromeliad from Puerto Rico
Eloisa Lasso and James D. Ackerman
(Click for Abstract)(Resumen Haga Clic Aquí)
Granivorous Birds as Potentially Important Post-dispersal Seed Predators in a Brazilian Forest Fragment
Marco A. Pizo and Emerson M. Vieira
(Click for Abstract)(Resumen Haga Clic Aquí)
Predation-mediated Mortality of Early Life Stages: A Field Experiment with Nymphs of an Herbivorous Stick Insect (Metriophasma diocles)
Jürgen R. Berger and Rainer Wirth
(Click for Abstract)
The Role of Canopy Ants in Removing Ficus perforata Seeds from Howler Monkey (Alouatta palliata mexicana) Faeces at Los Tuxtlas, Mexico
Rodolfo Martínez-Mota, Juan Carlos Serio-Silva and Víctor Rico-Gray
(Click for Abstract)(Resumen Haga Clic Aquí)
2004 Excellence Award
Beyond Paradise---Meeting the Challenges in Tropical Biology in the 21st Century
Kamaljit S. Bawa (kamal.bawa@umb.edu), W. John Kress, and Nalini M. Nadkarni
Tropical ecosystems support a diversity of species and ecological processes that are unparalleled anywhere else on Earth. Despite their tremendous social and scientific importance, tropical ecosystems are rapidly disappearing. To usher tropical ecosystems and the human communities dependent upon them through the environmental transformations of the 21st century, tropical biologists must provide critical knowledge in three areas: 1) the structure and function of tropical ecosystems; 2) the nature and magnitude of anthropogenic effects on tropical ecosystems; and 3) the socio-economic drivers of these anthropogenic effects. To develop effective strategies for conservation, restoration, and sustainable management of tropical ecosystems, scientific perspectives must be integrated with social necessities. A new set of principles built on a framework for pursuing relevant tropical biological research will facilitate interdisciplinary approaches, integrate biological knowledge with the social sciences, and link science with policy. We propose four broad recommendations for immediate action in tropical biology and conservation that are fundamental to all biological and social disciplines in the tropics: 1) assemble and disseminate information on life's diversity in the tropics; 2) enhance tropical field stations and build a worldwide network to link them with tropical field biologists at their field sites; 3) bring the field of tropical biology to the tropics by strengthening institutions in tropical countries through novel partnerships between tropical and temperate zone institutions and scientists; and 4) create concrete mechanisms to increase interactions between tropical biologists, social scientists, and policy makers.
Extracellular Enzyme Activities and Carbon Chemistry as Drivers of Tropical Plant Litter Decomposition
Steven D. Allison (steveall@stanford.edu) and Peter M. Vitousek
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.
Forty Years of Tropical Forest Recovery from Agriculture: Structure and Floristics of Secondary and Old-growth Riparian Forests in the Dominican Republic
Patrick H. Martin (martinp@ecostudies.org), Ruth E. Sherman, and Timothy J. Fahey
Interest in tropical secondary forests has grown as large areas of agriculture have been abandoned in recent decades; yet, there are few long-term studies of post-agriculture vegetation recovery in the tropics. In this study, we compared the vegetation structure and floristic composition of old-growth and 40-year-old secondary riparian forests in the Cordillera Central, Dominican Republic. Canopy height and stem density of woody plants were similar between forest types, but basal area of trees was 27 percent lower in secondary forests. Introduced tree species comprised 20 percent of the basal area and dominated the understory of secondary forests. Life-form diversity was higher in old-growth forests as arborescent ferns, the palm species, and epiphytic bromeliads, orchids, and bryophytes were much more abundant. The number of species of epiphytic orchids and bromeliads, ground ferns, and herbaceous plants was also significantly higher in old-growth forests. The species density of woody plants and vines, however, was comparable between forest types, and vine abundance was significantly higher in secondary forests. The high importance of introduced tree species and the delayed recovery of several plant life-forms have important implications for the conservation of plant diversity in secondary forests in the tropics. The robust regeneration of woody structure despite the long land tenure (ca 60 yr) by farmers is probably due to the nutrient-rich alluvial soils and low-intensity agriculture. This study revealed the potential for the rapid recovery of woody plant diversity and structure in fertile secondary forests adjacent to mature forest seed sources and the more delayed recovery of nonwoody plant diversity and abundance.
El interés por los bosques tropicales secundarios ha crecido debido a que grandes extensiones de áreas agrícolas han sido abandonadas en las últimas décadas. Aun así, en los trópicos hay pocos estudios a largo plazo sobre la recuperación de la vegetación de zonas agrícolas abandonadas. En nuestro estudio, comparamos la estructura de la vegetación y la composición florística de bosques ribereños maduros y bosques de 40 años de edad en la Cordillera Central de República Dominicana. La altura del dosel y la densidad de tallos de plantas leñosas fueron similares en los distintos tipos de bosque, pero el área basal de los árboles fue 27 por ciento más baja en los bosques secundarios. Las especies arbóreas introducidas representaron 20 por ciento del área basal y dominaron el sotobosque de los bosques secundarios. La diversidad de formas de vida fue más alta en los bosques maduros, debido a que los helechos arborescentes, las palmas, bromelias, orquídeas, y musgos epífítos fueron mucho más abundantes. El numero de especies de orquídeas y bromelias epifítas, helechos de tierra y de plantas herbáceas fue significativamente más alta en los bosques maduros. Sin embargo, el números de especies leñosas y de bejucos fue comparable en los dos tipos de bosque, mientras que la abundancia de bejucos fue significativamente mayor en los bosques secundarios. La gran importancia de las especies arbóreas exóticas y la lenta recuperación de varias formas de vida vegetal, llevan implicaciones importantes para la conservación de la diversidad de plantas en bosques tropicales secundarios. La regeneración vigorosa de la estructura leñosa, a pesar de la larga ocupación de estas tierras por los granjeros (ca 60 años) se debe, probablemente, a la riqueza de nutrientes del suelo en los terrenos aluviales y a la agricultura de baja intensidad que se practicaba en la zona. Este estudio demuestra el potencial para una recuperación rápida de la diversidad y estructura de la vegetación leñosa en bosques secundarios fértiles que colindan con fuentes de semilla ubicadas en bosques maduros, y la recuperación más lenta de la diversidad y abundancia de plantas no leñosas.
Levels of Herbivory in Two Costa Rican Rain Forests: Implications for Studies of Fossil Herbivory
Dena M. Smith (dena.smith@colorado.edu) and Cesar R. Nufio
We measured changes in insect herbivore intensity and guild structure in two tropical forests of Costa Rica over a three-year period. We estimated herbivory levels using discrete leaf litter samples to account for factors that influence the types of leaves most likely to be preserved in the fossil record. We found that leaf area removed by insect herbivores did not vary significantly between years within the two sampled forests, but differed across years between forests. The lack of variation in herbivore intensity within forests suggests that estimates of herbivore damage from fossil assemblages may reflect levels of herbivore intensity typically experienced by a given forest, at least over a short ecological timescale. The differences in herbivore intensity between similarly categorized forests suggest that simple one-to-one comparisons between fossil and modern sites can be problematic. The distribution of functional feeding groups also differed on an interannual basis both within and between forests. As guild structure can be highly variable, caution should be taken when comparing modern herbivore guild structures with those from fossil assemblages. Studies of herbivory in fossil assemblages have yielded much lower levels of damage than those found in this study as well as those measured from other modern forests. Leaf fossil preservation, environmental differences, and changes in plant-insect associations through time may account for these differences.
En este estudio medimos durante un período de tres años los cambios en la intensidad de herbivoría y la estructura de la comunidad de insectos herbívoros en dos bosques tropicales en Costa Rica. Estimamos los niveles de herbivoría usando muestras discretas de hojarasca teniendo en cuenta los factores que influyen sobre el tipo de hojas que tienen una mayor probabilidad de ser preservadas en el registro fósil. El área de la hoja removida por insectos herbívoros no cambio significativamente entre años dentro de los bosques muestreados, pero era diferente entre años entre bosques. La falta de variación en la intensidad de herbivoría dentro de un mismo bosque, sugiere que la estimación del daño por herbivoría en las comunidades fósiles puede reflejar los niveles de intensidad de herbivoría que se presentan típicamente en bosques actuales por lo menos en cortos periodos de tiempo ecológico. La diferencia en la intensidad de herbivoría entre bosques de categoría similar sugiere que las comparaciones simples uno a uno entre sitios fósiles y sitios modernos puede llegar a ser problemática. La distribución de grupos funcionales difieren año a año tanto entre como dentro de bosques. Ya que la estructura de la comunidad puede ser altamente variable, debe tenerse precaución al comparar las estructuras de la comunidad de herbívoros actuales con la comunidad fósil. Los estudios de herbivoría en comunidades fósiles han encontrado niveles de daño mucho menores que las encontradas en nuestro estudio al igual que en otras estudios en bosques actuales. La preservación de hojas fósiles, las diferencias en el ambiente y cambios en la asociación de plantas e insectos a través del tiempo pueden ser la causa de estas diferencias.
Herbivory by Leaf-Cutting Ants: Nutrient Balance between Harvested and Refuse Material
Enrique H. Bucher (buchereh@uolsinectis.com.ar), Victoria Marchesini, and Adriana Abril
From an ecological standpoint, the symbiosis between leaf-cutting ants and their fungus can be described as an herbivore feeding on plant material harvested by the ants, metabolized by the fungus, and finally removed by the ants as refuse. Here, we report on a nutrient balance (soluble and insoluble carbon and nitrogen compounds) between harvested and refuse material collected from six Acromyrmex lundi nests from a semiarid woodland in Córdoba, Argentina. The nutrient balance was calculated using cellulose as an indicator. Harvested material had low protein (10%) and high fiber content (57%). Refuse material was rich in fiber (53%), total nitrogen (2%), and ash content (28%). Balance was negative for soluble carbon and phenols. Soluble fibers, lignin, and true protein remained unchanged. Surprisingly, crude protein and all soluble nitrogen fractions had a positive balance, suggesting additional nitrogen sources besides plant material. Phenol utilization by the leaf-cutting ant fungus suggests that phenols are not harmful to the fungus. Inability to metabolize insoluble carbon compounds and a net nitrogen gain in the refuse material were peculiar and interesting features of the ant-fungus system.
Desde un punto de vista ecológico, la simbiosis entre las hormigas cortadoras y su hongo se comporta como un herbívoro que se alimenta de material vegetal el cual es colectado por las hormigas, metabolizado por el hongo, y finalmente eliminado por las hormigas como desecho. En este trabajo se evalúa el balance de nutrientes (compuestos de carbono y nitrógeno solubles e insolubles) entre el material colectado y el desechado en seis nidos de Acromyrmex lundi en un bosque semiárido en Córdoba, Argentina. El balance de nutrientes fue calculado usando celulosa como indicador. El material colectado presentó bajo contenido de proteína (10%) y alto contenido de fibras (57%). El material desechado era rico en fibras (53%), nitrógeno total (2%), y cenizas (28%). El balance fue negativo para el carbono soluble y los fenoles y neutro para fibra soluble, lignina, y proteína verdadera. Sorprendentemente, la proteína cruda y todas las fracciones solubles de nitrógeno tuvieron un balance positivo, sugiriendo una fuente adicional de nitrógeno aparte del material vegetal. La utilización de fenoles por el hongo de la simbiosis sugiere los fenoles no serían perjudiciales para el metabolismo del hongo. La incapacidad para metabolizar compuestos de carbono insoluble y la ganancia neta de nitrógeno en el material desechado son características particulares e interesantes del sistema hormiga-hongo.
Does Mangrove Leaf Chemistry Help Explain Crab Herbivory Patterns?
Amy A. Erickson (erickson@sms.si.edu), Susan S. Bell, and Clinton J. Dawes
We examined feeding by the mangrove tree crab Aratus pisonii in Tampa Bay, Florida, in relation to the percent dry weight of carbohydrate, protein, phenolics, condensed tannins, ash, carbon, nitrogen, carbon:nitrogen ratio, water content, and sclerophylly for leaves of the red mangrove Rhizophora mangle. Comparisons of leaf chemistry were made among leaves that experienced variable levels of crab damage. Because R. mangle is the crab's preferred food source based on damage patterns in the field, comparisons of R. mangle leaf chemistry were made in relation to that of the black mangrove Avicennia germinans and the white mangrove Laguncularia racemosa.
We observed a negative relationship between level of leaf damage and percent dry weight of nitrogen, carbohydrates, condensed tannins, and sclerophylly. In contrast, a positive relationship was found between leaf damage and the carbon:nitrogen ratio. The chemical constituents that provided the best explanation for differences in damage among the three mangrove species include condensed tannins, nitrogen, carbon:nitrogen ratio, carbohydrates, phenolics, water content, and ash. The results from this study suggest that chemistry only partially explains food preference by A. pisonii. It appears that A. pisonii feeding behavior and preference may be influenced by a more complex series of factors and interactions, which may include reproduction by, predation on, and interspecific competition with A. pisonii.
Observations on the ecology of weaver ants (Oecophylla smaragdina Fabricius) in a Thai mangrove ecosystem and their effect on herbivory of Rhizophora mucronata Lam.
Joachim Offenberg (offenberg@biology.au.dk), Sopon Havanon, Sanit Aksornkoae, Donald J. MacIntosh, and Mogens Gissel Nielsen
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.
Life History and Demography of Cephaloleia fenestrata (Hispinae: Chrysomelidae: Coleoptera)
Derek Marley Johnson (dmj10@psu.edu)
The Neotropical beetle Cephaloleia fenestrata is a specialist herbivore on Pleiostachya pruinosa (Marantaceae) in upland and flood zone habitat of lowland tropical wet forest in Costa Rica. Cephaloleia fenestrata spends its entire life cycle on P. pruinosa, feeding primarily in rolled young leaves as adults, feeding in the concavity of leaf petioles as larvae, and laying eggs and pupating on the leaf petioles. Egg development time is about average for Chrysomelidae, approximately ten days. Cephaloleia fenestrata larvae, like other rolled leaf hispines, have an extremely long development period (94 d) consisting of only two instars (compared to a range of three to six in other Chrysomelidae). The 30-day pupal stage is also long, but within the range of that observed in other Chrysomelidae. Adults live an average of six weeks. The generation time for C. fenestrata is thus approximately six months. Male C. fenestrata lived longer and had a higher capture probability than females. There was no difference between males and females in the movement probabilities between upland and flood zone habitat. Rolled P. pruinosa leaves are both ephemeral (available to the beetles for approximately two days) and somewhat rare (1 in ca 15 ramets has a rolled leaf). Adults must move from leaf to leaf ca 36 times during their average adult life span. Still, C. fenestrata adults demonstrate high site fidelity.
El escarabajo neotropical Cephaloleia fenestrata es un herbívoro especialista en Pleiostachya pruinosa (Marantaceae) de las partes altas y zonas de inundación de la selva lluviosa tropical de tierras bajas en Costa Rica. Cephaloleia fenestrata pasa todo su ciclo de vida dentro de P. pruinosa. Como adulto, se alimenta principalmente en el interior de hojas enrolladas jovenes y como larva en las concavidades de los pecíolos de las hojas. Los huevos y pupas se encuentran en los pecíolos. El tiempo de desarrollo dentro de los huevos es aproximadamente 10 días, cercano al tiempo promedio para la familia Chrysomelidae. Las larvas de C. fenestra, como otras de la subfamilia Hispinae, tienen un periodo de desarrollo exageradamente largo (94 días), consistiendo de solo dos estadios (comparado al rango de tres a seis estadios de otros Chrysomelidae). La etapa pupal de 30 dias de duración también es larga, pero está dentro del rango observado en otros Chrysomelidae. Los adultos viven un promedio de seis semanas. Por lo tanto, el tiempo generacional de C. fenestrata es aproximadamente seis meses. Los machos de C. fenestrata vivieron más tiempo y tuvieron una mayor probabilidad de ser capturados que las hembras. No hubo diferencias entre machos y hembras en cuanto a las probabilidades de movimiento entre las zonas altas y las zonas de inundación. Las hojas enroscadas del P. pruinosa son efímeras (están disponibles para los escarabajos aproximadamente durante dos días) y son un tanto escasas (aproximadamente uno de cada 15 tallos tiene una hoja enroscada). Los adultos deben moverse de hoja en hoja aproximadamente 36 veces durante su tiempo de vida promedio. Aun así, los adultos C. fenestrata demuestraron alta fidelidad de sitios.
Differential Wing Strength in Pierella Butterflies (Nymphalidae, Satyrinae) Supports the Deflection Hypothesis
Ryan I. Hill (rihill@uclink.berkeley.edu) and Jarol F. Vaca
The "deflection hypothesis" asserts that conspicuous marginal patches on insect wings function to deflect predator attacks toward such patches and away from more vital body parts. As a result of selection from predator attacks, these marks are predicted to increase the probability of escape by tearing relatively easily. To test if a conspicuous marginal patch is weak relative to a homologous wing area without such a patch, hindwing tear weight was compared among three Pierella species (Satyrinae) differing in the presence of a conspicuous patch in the hindwing tornus. The species with a conspicuous white hindwing patch (P. astyoche) had significantly lower tear weights than the two species lacking the patch (P. lamia and P. lena). Forewing length did not explain variation in wing-tear weight, but wing-tear weight was positively related to insect age in a manner consistent with the deflection hypothesis. Older individuals of P. lamia and P. lena had higher tear weight, whereas this relationship was absent in P. astyoche. These results represent the first direct evidence that deflection marks on butterfly wings are relatively weak and should have an increased tendency to tear when handled by a predator.
La "hipótesis de desvio" propone que las conspicuas manchas marginales en alas de insectos funcionan para desviar los ataques de depredadores hacia tales manchas y lejos de partes del cuerpo más vitales. Como resultado de selección por ataques de depredadores, se predice que estas manchas deberían rompese fácilmente para aumentar la probabilidad de escape. Para probar si un mancha marginal conspicua es débil comparada con un área homóloga de alas sin tales manchas, se comparó el peso de rotura del ala posterior entre tres especies de Pierella (Satyrinae) que difieren en la presencia de un mancha visible en el tornus del ala posterior. Las alas posteriores de la especie con una mancha blanca visible (P. astyoche) se rasgaron con pesos significativamente más bajos comparadas con las alas posteriores de las dos especie sin mancha (P. lamia y P. lena). La longitud del ala anterior no explicó la variación en el peso de rotura, pero el peso de rotura estuvo relacionado positivamente con la edad del insecto de una manera consistente con la hipótesis de desvío. Los individuos más viejos de P. lamia y P. lena tuvieron los pesos de rotura más altos, mientras que ésta relación no se encontró en P. astyoche. Estos resultados representan la primera evidencia directa de que las manchas de desvío en alas de mariposas son relativamente débiles y deben tener una tendencia aumentada a romperse cuando son manipuladas por un depredador.
Introduced honeybees (Apis mellifera) reduce pollination success without affecting the floral resource taken by native pollinators
Roselaini Mendes do Carmo, Edivani Villaron Franceschinelli (edivani@icb.ufmg.br), and Fernando Amaral da Silveira
Detrimental effects of introduced honeybees (Apis mellifera L.) on native plant pollination have been predicted based on their observed deterrence or expulsion of native pollinators or their depletion of floral resources. Here, a case is reported in which floral visitation by the introduced honeybee affects male fitness and probably fruit and seed production of a tropical tree without affecting the resource sought by the native pollinator. Clusia arrudae is a dioecious species and is pollinated by individuals of Eufriesea nigrohirta that visit its flowers to collect resin. Male flowers, however, are also visited by individuals of A. mellifera, which remove ca 99 percent of their pollen grains. When E. nigrohirta leaves flowers previously visited by A. mellifera, they carry on their bodies less than 0.1 percent of the pollen grains carried by bees leaving flowers not visited by the honeybee. This may explain why the frequency of A. mellifera at male flowers is negatively correlated with the number of seeds produced by female flowers. This novel situation may affect other plants offering alternative rewards for pollinators, such as resins, oils, and aromatic compounds.
A polinização de espécies nativas de plantas pode ser prejudicada em decorrência das visitas da abelha introduzida Apis mellifera. Isto tem sido previsto com base em registros de situações em que esta abelha impede o acesso de polinizadores nativos ou os expulsa das flores e também pelo fato dela exaurir os recursos florais. Clusia arrudae é polinizada por Eufriesea nigrohirta que busca resina em suas flores. Apis mellifera visita as flores masculinas de Clusia arrudae e remove cerca de 99 percent dos grãos do pólen da flor visitada. Quando E. nigrohirta visita flores já visitadas por A. mellifera, ela carrega em seu corpo menos de 0,1 percent dos grãos de pólen carregados por abelhas que visitam flores ainda não visitadas por A. mellifera. Isto pode explicar porque a freqüência de A. mellifera em flores masculinas é negativamente correlacionada com a quantidade de sementes produzidas por flores femininas. Esta é uma situação que ainda não havia sido registrada e que pode afetar outras plantas que oferecem recursos alternativos para o polinizador, como resinas, óleos, e compostos aromáticos.
Flower mites of Calyptrogyne ghiesbreghtiana (Arecaceae): Evidence for dispersal using pollinating bats
Marco Tschapka (marco.tschapka@biologie.uni-ulm.de) and Saul A. Cunningham
We describe the association between a new species of flower mite (tribe Melicharini) and Neotropical flower-visiting bats. Analogous to the well-known hummingbird-mite interactions, these mites appear of use bat visitors of the lowland tropical palm Calyptrogyne ghiesbreghtiana as a means of traveling to new inflorescences. Phenology data show tight coupling between the occurrence of mites on bats and flowering phenology of C. ghiesbreghtiana, suggesting that the palm is the most important host for the mites.
Describimos la asociación entre una nueva especie de ácaro de las flores (tribu Melicharini) y murciélagos Neotropicales que visitan flores. Similar a la interacción bien conocida entre colibríes y ácaros, aparentemente estos ácaros utilizan a los murciélagos que visitan las inflorescencias de la palma Calyptrogyne ghiesbreghtiana como medio de transporte hacia nuevas inflorescencias. Datos de fenología indican una fuerte asociación entre los registros de los ácaros en los murciélagos y la fenología floral de C. ghiesbreghtiana, sugierendo que la palma es el hospedero más importante para los ácaros.
Population Dynamics of a Resident Colony of Leptonycteris curasoae (Chiroptera: Phyllostomidae) in Central Mexico
Cristobal Galindo G., Adalinda Sánchez Q., Ramón H. Quijano and L. Gerardo Herrera M. (gherrera@ibiologia.unam.mx)
We studied the population dynamics of the lesser long-nosed bat Leptonycteris curasoae in a cave in central Mexico for a two-year time. The population had substantial seasonal changes in size and composition during this time. Colony size was largest from February to July (22,000-27,000 adults) and contained equal numbers of males and females. In June and July, males had enlarged testes and presumably mated with females. In August, the population size began to decline and was mostly composed of pregnant females. Between September and December, the colony was composed exclusively of pregnant and lactating females and their young, and population size decreased to about one-third of the observed maximum size. In January, adult males returned to the roost and the population size increased. We also observed an increase in body mass and fat accumulation in both sexes, apparently related to reproductive activity. This is the first report of the continuous presence of a substantial female population of L. curasoae throughout the year in a single roost in Mexican tropics, indicating that some populations of L. curasoae in central Mexico complete their life cycle without having to migrate.
Se estudió la dinámica poblacional del murciélago nectarívoro Leptonycteris curasoae en una cueva localizada en el centro de México durante dos años. La población presentó cambios sustanciales en su tamaño y composición durante este período. El tamaño más grande de la población se registró entre febrero y julio (22,000-27,000 individuos) con una proporción similar de hembras y machos. En junio y julio los testículos de los machos crecieron y aparentemente se aparearon con las hembras. En agosto, la población empezó a disminuir y se encontraron casi exclusivamente hembras preñadaz. Entre septiembre y diciembre, la colonia estuvo compuesta exclusivamente de hembras preñadaz o lactantes y de sus crías. La población disminuyó en este periodo hasta equivaler a una tercera parte del tamaño máximo registrado en el año. En enero, la población empezo a crecer de nuevo con la incorporación de machos adultos. Durante el año, en ambos sexos se observaron también cambios en la masa corporal y en la acumulación de grasa aparentemente relacionados con la actividad reproductiva. Este es el primer estudio que reporta la presencia continua de hembras en una colonia de L. curasoae en la misma cueva durante todo el año para el centro de México. Nuestros resultados indican que esta población no es migratoria a diferencia de otras poblaciones de esta especie.
Fruit, Minerals and Forest Elephant Trails: Do All Roads Lead to Rome?
Stephen Blake (sblake@wcs.org) and Clement Inkamba-Nkulu
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 Landscape
Lisa A. Schonberg (drummer@riseup.net), John T. Longino, Nalini M. Nadkarni, Stephen P. Yanoviak and Jon C. Gering
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 afectan 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.
Physical Damage in Relation to Carbon Allocation Strategies of Tropical Forest Tree Saplings
Pauw et al. (pauw@botzoo.uct.ac.za)
We show that tropical forest tree saplings with greater belowground carbon allocation have more breakage scars along their stems. We suggest the existence of alternative carbon allocation strategies in relation to physical damage in the forest understorey. "Tolerators" allocate more belowground, have enhanced resprouting ability and slower aboveground growth, whereas "escapers" allocate less belowground, are not well prepared for recovering from damage, but grow fast enough to escape from the damage-susceptible size class.
Brinzales de árboles tropicales que asignan mayor cantidad de carbono bajo el suelo muestran más cicatrices de fractura en sus tallos. Sugerimos la existencia de estrategias alternativas de asignación de carbono en respuesta a daño físico en el sotobosque: los "tolerantes" asignan mayor cantidad de carbono bajo el suelo, tienen mayor capacidad para rebrotar y su crecimiento aéreo es lento; los "escapistas" asignan menor cantidad de carbono bajo el suelo y no están bien preparados para recuperarse después de ocurrido un daño, pero crecen lo suficientemente rápido para escapar de la clase diamétrica más susceptible a daños.
The Flexible Breeding System of Werauhia sintenisii, a Cloud Forest Bromeliad from Puerto Rico
Eloisa Lasso (elasso@students.uiuc.edu) and James D. Ackerman
The tropical mountain cloud forest bromeliads studied thus far have been reported as self compatiable; however, whether or not autogamy and apomixis occur is not known. We characterized the breeding system of Werauchia sintenisii using a series of treatments to detect self-compatibility, autogamy, and apomixes. The natural fruit set of this population was 97 percent. Pollen origin (self vs. cross) did not affect fruit and seed set. Werauhia sintenisii is autogamous but not apomictic. All pollinator-excluded flowers produced fruits, but flowers that were emasculated and caged did not produce any fruit. Factors affecting the evolution of autogamy in this system are discussed.
Las bromelias de Bosques Montanos estudiadus hasta la fecha han sido reportadas como auto-compatibles. Sin embrago, se desconoce si las mismas son autogamas o apomicticas. Caracterizamos el sistema de apareamiento de Werauchia sintenisii por medio de una serie de tratamientos disenados para detectar auto-compatibilidad, autogamia, y apomixes. En la poblacion estudiada 97 por ciento de las flores producen frutos. El origen del pollen (propio vs foraneo) no afecto el numero de semillas y fructos producidos. Werauhia sintenisii es autogama pero no apomictica. Todas las flores que fueron excluidas a los polinizadores produjeron frutos, sin embargo aquellas que fueron emasculadas y excluidas a los polinizadores no produjeron frutos. Se discuten los factores que han podido afectar la evolucion de autogamia en este sistema.
Granivorous Birds as Potentially Important Post-dispersal Seed Predators in a Brazilian Forest Fragment
Marco A. Pizo (pizo@rc.unesp.br) and Emerson M. Vieira
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 (Croton 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 of C. priscus. We interpret such apparent imbalance in the interaction between C. priscus and their seed predators as a possible consequence of forest fragmentation.
Em florestas tropicais, enquanto os roedores figuram entre os principais 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 granívoras terrestres são abundantes. Neste estudo nós usamos sementes de uma árvore característica de vegetação secundária (Croton priscus, Euphorbiaceae) para investigar experimentalmente a importância relativa dos roedores e das aves granívoras como predadores de sementes em um destes fragmentos da floresta. Concomitantemente também estimamos a densidade das aves granívoras e a abundância de pequenos mamíferos. Os resultados obtidos indicaram que, como conseqüência da baixa abundância de roedores e alta abundância de aves granívoras, estas são ao menos tão importantes quanto os roedores como predadores pós-dispersão das sementes de C. priscus. Interpretamos este padrão pouco usual na interação entre C. priscus e os predadores de suas sementes como uma possível conseqüência da fragmentação da floresta.
Predation-mediated Mortality of Early Life Stages: A Field Experiment with Nymphs of an Herbivorous Stick Insect (Metriophasma diocles)
Jürgen R. Berger (jrberger@rhrk.uni-kl.de) and Rainer Wirth
We quantified predation pressure on first instar nymphs of a stick insect in predator-exclusion experiments in the forest of Barro Colorado Island, Panamá. After considering intrinsic mortality (19%) and potential emigration (negligible), we estimated that 54 percent of the nymphs died due to predation in a two-week period. Predation on nymphs was highest at night and may explain the low abundance of Metriophasma. diocles in the understory.
The Role of Canopy Ants in Removing Ficus perforata Seeds from Howler Monkey (Alouatta palliata mexicana) Faeces at Los Tuxtlas, Mexico
Rodolfo Martínez-Mota, Juan Carlos Serio-Silva and Víctor Rico-Gray (ricogray@ecologia.edu.mx)
We analyzed Ficus perforata seed removal by canopy ants under four treatments: syconia seeds; howler monkey-defecated washed seeds; syconia seeds with howler dung; and defecated seeds with howler dung. Ants removed more defecated washed seeds in the wet season, while during the dry season, removal was greater for syconia seeds and defecated washed seeds. Our results suggest that ants tended to remove more seeds when they were not embedded in feces; however, even seeds set on howler dung were still attractive to ants.
Determinamos la preferencia de hormigas para remover semillas de Ficus perforata bajo cuatro tratamientos: semillas provenientes de siconos y semillas defecadas por monos aulladores; y dentro de cada uno de estos tipos se colocaron semillas sobre heces frescas. Las hormigas removieron más semillas defecadas en la estación húmeda, mientras que en la estación seca la mayor remoción fue para las semillas de siconos y semillas defecadas. Los resultados sugieren que las hormigas remueven más semillas cuando no están embebidas en excretas, sin embargo también las semillas colocadas en excretas fueron atractivas para las hormigas.