Beyond Paradise----Meeting the Challenges in Tropical Biology in the 21st Century
Kamaljit S. Bawa, W. John Kress, and Nalini M. Nadkarni, and Sharachchandra Lele
(Click for Abstract)(Resumen Haga Clic Aquí)(Resumo Haga Clic Aquí)
Why Do Some Tropical Forests Have So Many Species of Trees?
Egbert Giles Leigh, Jr., Priya Davidar, Christopher W. Dick, Jean-Philippe Puyravaud, John Terborgh, Hans ter Steege, and Stuart Joseph Wright
(Click for Abstract)(Resumen Haga Clic Aquí)
Decomposition of Greenfall vs. Senescent Foliage in a Tropical Forest Ecosystem in Puerto Rico
Steven J. Fonte and Timothy D. Schowalter
(Click for Abstract)(Resumen Haga Clic Aquí)
Does Growth and Survival of Aerial Roots Limit the Vertical Distribution of Hemiepiphytic Aroids?
Christoph F. J. Meyer and Gerhard Zotz
(Click for Abstract)(Resumen Haga Clic Aquí)
Population Dynamics of Pterocereus gaumeri, a Rare and Endemic Columnar Cactus of Mexico
Martha Méndez, Rafael Durán, Ingrid Olmstead, and Ken Oyama
(Click for Abstract)(Resumen Haga Clic Aquí)
Forest Tree Persistence, Elephants, and Stem Scars
Douglas Sheil and Agus Salim
(Click for Abstract)
Temporal Variation in the Relative Abundance of Fruit Bats (Megachiroptera: Pteropodidae) in Relation to the Availability of Food in a Lowland Malaysian Rain Forest
Robert Hodgkison, Sharon T. Balding, Akbar Zubai, and Thomas H. Kunz
(Click for Abstract)
Avian Geophagy and Soil Characteristics in Southeastern Peru
Donald Brightsmith and Romina Aramburú Muñoz-Najar
(Click for Abstract)(Resumen Haga Clic Aquí)
Variación Estacional de un Ensamble de Aves en un Bosque Subtropical Semiarido del Chaco, Argentino
Mariano Codesido and David Bilenca
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Spatial Ecology of Puerto Rican Boas (Epicrates inornatus) in a Hurricane Impacted Forest
Joseph M. Wunderle Jr., Javier E. Mercado, Bernard Parresol, and Esteban Terranova
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Respiratory Ecology of Macroinvertebrates in a Swamp-River System of East Africa
Lauren J. Chapman, Kimberly R. Schneider, Chrissy Apodaca, and Colin A. Chapman
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Escape Behavior of Neotropical Homopterans in Response to a Flush-Pursuit Predator
Mark L. Galatowitsch and Ronald L. Mumme
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Spatial Distribution Patterns of Jumping Spiders Associated with Terrestrial Bromeliads
Gustavo Q. Romero and João Vasconcellos-Neto
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Influences of Fruit Diversity and Abundance on Bird Use of Two Shaded Coffee Plantations
Tomás A. Carlo, Jaime A. Collazo, and Martha J. Groom
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Forest Modification Affects Diversity, but not Dynamics of Speciose Tropical Pyraloid Moth Communities
Konrad Fiedler and Christian H. Schulze
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Do Species Dominance Indices Indicate Rain Forest Disturbance by Logging?
Matti Nummelin and Seppo Kaitala
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The Striped Squirrel (Tamiops swinhoei hainanus) as a Nectar Robber of Ginger (Alpinia kwangsiensis)
Xao-Bao Deng, Pan-Yu Ren, Jiang-Yun Gao, and Qing-Jun Li
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Logging Speeds Little Red Fire Ant Invasion of Africa.
Peter D. Walsh, Phillipp Henschel. Kate A. Abernethy, Caroline E.G. Tutin, Paul Telfer, and Sally A. Lahm
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The Azteca-Cecropia Association: Are Ants Always Necessary for Their Host Plants?
Sarita B. Fáveri and Heraldo L. Vasconcelos
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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, and Sharachchandra Lele
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 help tropical ecosystems and the human communities dependent upon them better face the challenges of the 21st century, tropical biologists must provide critical knowledge in three areas: (1) the structure and functioning 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. Three principles for guiding tropical biological research are suggested: (1) broadening the set of concerns; (2) integration of biological knowledge with the social sciences and traditional knowledge; and (3) linking science to policy and action. Four broad recommendations are proposed 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.
Los ecosistemas tropicales mantienen una diversidad de especies y procesos ecológicos como ningún otro en la tierra. A pesar de su gran importancia a nivel social y científico, los ecosistemas tropicales están desapareciendo rápidamente. Para ayudar a estos y a las comunidades humanas que dependen de ellos a encarar mejor los desafíos del siglo 21, los biólogos tropicales deben proveer información crítica en tres áreas: (1) la estructura y funcionamiento de los ecosistemas tropicales; (2) la naturaleza y magnitud de los efectos antropogénicos sobre los ecosistemas tropicales; y (3) las fuerzas socio-económicas de esos efectos antropogénicos. Para desarrollar estrategias efectivas para la conservación, restauración y manejo sostenible de los ecosistemas tropicales , las perspectivas científicas deben ser integradas a las necesidades sociales. Tres principios para orientar la investigación en biología tropical son sugeridos: (1) ampliación del grupo de interés; (2) integración del conocimiento biológico con las ciencias sociales y el conocimiento tradicional; y (3) enlazar la ciencia con las políticas y la acción. Para una acción inmediata en biología tropical y la conservación, se proponen cuatro recomendaciones amplias que son fundamentales a todas la disciplinas biológicas y sociales en los trópicos: (1) recopilar y diseminar información sobre diversidad biológica en los trópicos; (2) mejorar las facilidades para la investigación en los trópicos (estaciones biológicas) y construir una red mundial que las una con los biólogos tropicales; (3) apoyar el campo de la biología tropical fortaleciendo las instituciones de los países tropicales a través de la colaboración con instituciones y científicos de zonas templadas; y (4) crear mecanismos concretos para incrementar la interacción entre biólogos tropicales, científicos sociales y tomadores de decisiones.
Os ecossistemas tropicais abrigam uma diversidade de espécies e de processos ecológicos sem paralelo em qualquer outro lugar da Terra. Apesar de sua tremenda importncia social e científica, os ecossistemas tropicais estão desaparecendo rapidamente. Para ajudar os ecossistemas tropicais e as populações humanas que dependem deles a melhor enfrentar os desafios do século 21, os biólogos tropicais precisam gerar conhecimentos cruciais em três áreas: (1) a estrutura e o funcionamento dos ecossistemas tropicais; (2) a natureza e a magnitude dos efeitos antrópicos sobre os ecossistemas tropicais; e (3) as diretrizes sócio-econmicas destes efeitos antrópicos. Para se desenvolver estratégias efetivas para a conservação, restauração e manejo sustentável dos ecossistemas tropicais, as perspectivas científicas tem que ser integradas s necessidades sociais. Três princípios norteadores da pesquisa em biologia tropical são indicados: (1) ampliar o conjunto de interesses; (2) integrar o conhecimento biológico com o conhecimento tradicional e as ciências sociais; e (3) unir ciência com política e tomada de decisão. Quatro amplas recomendações são propostas para ação imediata na biologia tropical e conservação e que são fundamentais para todas as disciplinas biológicas e sociais nos trópicos: (1) organizar e disseminar informação sobre a diversidade biológica nos trópicos; (2) consolidar as estações de pesquisa de campo nos trópicos e construir uma rede mundial para ligar estas estações e os biólogos tropicais atuando nelas; (3) levar o campo da biologia tropical para os trópicos pelo fortalecimento das instituições nos países tropicais e através de novas parecerias entre estes países e seus cientistas com os cientistas e as instituições de países da região temperada; e (4) criar mecanismos concretos para aumentar as interações entre os biólogos tropicais, os cientistas sociais e os políticos tomadores de decisão.
Why Do Some Tropical Forests Have So Many Species of Trees?
Egbert Giles Leigh, Jr. (LeighL@si.edu). Priya Davidar, Christopher W. Dick, Jean-Philippe Puyravaud, John Terborgh, Hans ter Steege, and Stuart Joseph Wright
Understanding why there are so many kinds of tropical trees requires learning, not only how tree species coexist, but what factors drive tree speciation and what governs a tree clade's diversification rate. Many report that hybrid sterility evolves very slowly between separated tree populations. If so, tree species rarely originate by splitting of large populations. Instead, they begin with few trees. The few studies available suggest that reproductive isolation between plant populations usually results from selection driven by lowered fitness of hybrids: speciation is usually a response to a "niche opportunity." Using Hubbell's neutral theory of forest dynamics as a null hypothesis, we show that if new tree species begin as small populations, species that are now common must have spread more quickly than chance allows. Therefore, most tree species have some setting in which they can increase when rare. Trees face trade-offs in suitability for different microhabitats, different-sized clearings, different soils and climates, and resistance to different pests. These trade-offs underlie the mechanisms maintaining a-diversity and species turnover. Disturbance and microhabitat specialization appear insufficient to maintain a-diversity of tropical trees, although they may maintain tree diversity north of Mexico or in northern Europe. Many studies show that where trees grow readily, tree diversity is higher and temperature and rainfall are less seasonal. The few data available suggest that pest pressure is higher, maintaining higher tree diversity, where winter is absent. Tree a-diversity is also higher in regions with more tree species, which tend to be larger, free for a longer time from major shifts of climate, or in the tropics, where there are more opportunities for local coexistence.
Comprender por qué hay tantos tipos de árboles tropicales, se requiere aprender no sólo cómo las especies de árboles coexisten, sino también, cuáles factores conducen a su especiación, y qué determina la velocidad de diversificación de un clado de árboles. Muchos reportan que la esterilidad híbrida evoluciona muy lentamente entre poblaciones separadas de árboles. De ser así, las especies de árboles raramente se originarían por la separación de grandes poblaciones; más bien empezarían con pocos árboles. Los pocos estudios disponibles sugieren que el aislamiento reproductivo entre las poblaciones vegetales usualmente resulta de selección derivada del bajo éxito de los híbridos: la especiación generalmente responde a una "oportunidad de nicho". Usando la teoría neutral de Hubbell de dinámica de bosques como hipótesis nula, nosotros mostramos que si las nuevas especies de árboles comienzan como poblaciones pequeñas, especies que ahora son comunes deberían haberse expandido más rápido que lo que el azar permite. Por lo tanto, la mayoría de las especies de árboles tendrían alguna condición donde sus poblaciones podrían crecer cuando son raras. Los árboles enfrentan compromisos en su adecuación por diferentes microhábitats, claros de diferentes tamaños, diferentes suelos y climas, y resistencia a diferentes plagas. Estos compromisos sirven de base para los mecanismos que mantienen la diversidad a y al reemplazo espacial de especies. Los disturbios y la especialización de microhabitats parecen ser insuficiente para mantener la diversidad a de árboles tropicales, sin embargo ellos pueden mantener diversidad de árboles al norte de México o en Europa del norte. Muchos estudios muestran que en lugares donde los árboles crecen fácilmente, la diversidad de árboles es mayor donde la temperatura y la lluvia son menos estacionales. Los pocos estudios disponibles sugieren que la presión de las plagas es mayor, manteniendo así la diversidad de árboles en lugares donde no hay invierno. La diversidad a de árboles también es más alta en regiones con más especies de árboles, las cuales tienden a ser más largas, exentas por un largo periodo de tiempo de grandes cambios climáticos , o en los trópicos donde hay más oportunidades de coexistir localmente.
Decomposition of Greenfall vs. Senescent Foliage in a Tropical Forest Ecosystem in Puerto Rico
Steven J. Fonte and Timothy D. Schowalter (tschowalter@agcenter.lsu.edu)
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, and Cecropia 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 caídas de cuatro especies dominantes (Dacryodes excelsa, Manilkara bidentata, Guarea guidonia, y Cecropia schreberiana) en un bosque lluvioso montañoso bajo en la estación El Verde, Bosque Experimental de Luquillo, Puerto Rico. Hojas verdes de la copa de los árboles y hojas senescentes recién caídas 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 caída de hojas verdes puede influir en forma significativa en los procesos de descomposición y ciclaje de nutrientes en bosques que experimentan a gran escala remoción de follaje verde.
Do Growth and Survival of Aerial Roots Limit the Vertical Distribution of Hemiepiphytic Aroids?
Christoph F. J. Meyer and Gerhard Zotz (gerhard.zotz@unibas.ch)
We tested the hypothesis that growth and survival of aerial roots impose a limit on the height at which a primary hemiepiphyte can become successfully established within tree crowns and evaluate the implications for the vertical distribution of hemiepiphytes in the forest canopy. Density and spatial distribution, and growth and survival of aerial roots were studied in two common species of hemiepiphytic Araceae, Philodendron radiatum and Anthurium clavigerum, in a lowland tropical moist forest in Panama between March and October 2001. Additionally, root growth and survival were studied both in normal, unmanipulated, and experimentally cut roots to investigate the effect of damage on root resprouting and survival. Survival analysis revealed much greater survival of aerial roots of A. clavigerum than P. radiatum. In contrast, growth rates in the latter were on average about three times higher when compared to A. clavigerum. In both species, experimental cutting of the root invariably led initially to the development of dieback symptoms; however, plants responded to root damage by producing resprouts. A risk model for the two species suggests that only the fastest-growing roots of P. radiatum are likely to survive long enough to reach the soil from a host branch 6.8 m high, which equals the mean height of occurrence observed for the epiphytic stage of this species at our study site. In contrast, slow-growing appressed aerial roots of A. clavigerum may never be able to establish a connection with the soil from similar heights in the canopy before roots die. Consistent with our hypothesis, A. clavigerum is found much lower in the forest (it rarely exceeds ca 5 m).
Probamos la hipótesis que el crecimiento y la sobrevivencia de raíces aéreas imponen un límite en la altura en que una hemiepífita primaria puede establecerse con éxito dentro de la copa de los árboles, y evaluamos las implicaciones para la distribución vertical de hemiepífitas en el dosel del bosque. La densidad y la distribución espacial y el crecimiento y la sobrevivencia de raíces aéreas fueron estudiados en dos especies comunes de hemiepífitas de la familia Araceae, Philodendron radiatum e Anthurium clavigerum, en un bosque húmedo tropical en Panamá entre Marzo y Octubre del 2001. Adicionalmente, el crecimiento y sobrevivencia de las raíces se estudió en raíces normales sin manipular y raíces cortadas experimentalmente para investigar el efecto de daño en la punta de crecimiento y sobrevivencia de raíces. El análisis de sobrevivencia reveló que hay una mayor sobrevivencia en las raíces aéreas de A. clavigerum que en P. radiatum . En contraste, las tasas de crecimiento en esta última fueron en promedio casi tres veces más altas comparado con A. clavigerum. En ambas especies, el corte experimental de la raíz invariablemente conllevó al principio al desarrollo de síntomas de "dieback", sin embargo las plantas respondieron al daño de la raíz, produciendo nuevas puntas de crecimiento. Un modelo de riesgo para las dos especies sugiere que solamente las raíces de crecimiento rápido de P. radiatum probablemente sobrevivan un tiempo suficientemente para alcanzar el suelo desde una rama hospedadora a 6.8 m de altura, la cual iguala la altura promedia de ocurrencia observada, para la etapa epifítica de esta especie en nuestro área de estudio. En contraste, debido al crecimiento lento de las raíces aéreas de A. clavigerum, probablemente esta nunca sea capaz de establecer una conección con el suelo desde alturas similares en el dosel antes de que las raíces mueran. Consistente con nuestra hipótesis, A. clavigerum se encuentra a una altura menor dentro del bosque (raramente suele ocurrir arriba de ca 5 m).
Population Dynamics of Pterocereus gaumeri, a Rare and Endemic Columnar Cactus of Mexico
Martha Méndez (mar@cicy.mx), Rafael Durán, Ingrid Olmstead, and Ken Oyama
We conducted a demographic examination of Pterocereus gaumeri, a rare and endemic columnar cactus of the Yucatan peninsula, Mexico. Growth, survival, and fecundity of individuals were recorded in two populations from 1997 to 1999. Size-based population projection matrices were constructed to document the population dynamics. Seed germination and seedling establishment experiments were conducted in the field to estimate the rate of seed and seedling survival. Our results show that P. gaumeri did not reproduce by asexual means or vegetative growth and thus relies wholly on sexual reproduction for population growth. Low reproductive success, seed predation, and low seedling survival appear to be important factors that contribute to the rarity of this species. The population growth rate (λ) varied between 0.9545 and 1.0316. According to the matrix elasticity values, population dynamics of this species depend mainly on adult survival, with low values in fecundity and survival for the lowest size categories. Our results did not indicate that the population size of P. gaumeri was decreasing; however, increasing pressure on land use transformation is one of the most important factors that may threaten the persistence of this species.
Se presenta un estudio demográfico de Pterocereus gaumeri, un cactus raro, y endémico columnar de la Península de Yucatán, México. Desde 1997 a 1999, se registró el crecimiento, la sobrevivencia y la fecundidad de indivíduos en dos poblaciones. Se construyeron matrices de proyección basadas en tamaño poblacional para documentar la dinámica de las poblaciones. Se realizaron experimentos de germinación de semillas y establecimiento de plántulas en condiciones naturales, para estimar la tasa de sobrevivencia de semillas y plántulas. Nuestros resultados sugieren que P. gaumeri no se reproduce asexualmente o por crecimiento vegetativo, por lo tanto el crecimiento poblacional depende completamente de la reproducción sexual. El bajo éxito reproductivo, la depredación de semillas y la baja tasa de sobrevivencia parecen ser factores importantes que contribuyen a la rareza de esta especie. La tasa de crecimiento poblacional (λ) varía entre 0.9545 y 1.0316. De acuerdo con los valores de las matriz de elasticidad, la dinámica poblacional de esta especie depende principalmente de la sobrevivencia de los adultos, con valores bajos en fecundidad y sobrevivencia de las categorías de tamaños menores. Nuestros resultados no indican que el tamaño poblacional de P. gaumeri esté decreciendo, sin embargo, el incremento de presion por el cambio de uso de la tierra es uno de los factores más significativos que puede amenazar la continuidad de esta especie.
Forest Tree Persistence, Elephants, and Stem Scars
Douglas Sheil (d.sheil@cgiar.org) and Agus Salim
Sixteen percent of tree stems 10 cm diameter or greater recorded in seven 1 ha plots in Rabongo Forest, Uganda had stem damage attributable to elephants (Loxodonta africana). We propose four strategies that may help tree species persist under these conditions: repellence, resistance, tolerance and avoidance. We sought and found evidence for each strategy. Large, shade-tolerant Cynometra alexandri dominated basal area (often >50%) and showed severe scarring. Nearly 80 percent of stems were small pioneer species. Scarring frequency and intensity increased with stem size. Stem-size distributions declined steeply, implying a high mortality to growth rate ratio. Tree species with spiny stems or with known toxic bark defenses were unscarred. Epiphytic figs escaped damage while at small sizes. Mid-successional tree species were scarce and appeared sensitive to elephants. Savanna species were seldom scarred. Taking stem size-effects into account by using a per-stem logistic modeling approach, scarring became more probable with slower growth and with increasing species abundance, and also varied with location. Pioneer and shade-bearer guilds showed a deficit of intermediate-sized stems. Evidence that selective elephant damage is responsible for monodominant C. alexandri forests remains equivocal; however, elephants do influence tree diversity, forest structure, and the wider landscape.
Temporal Variation in the Relative Abundance of Fruit Bats (Megachiroptera: Pteropodidae) in Relation to the Availability of Food in a Lowland Malaysian Rain Forest
Robert Hodgkison (rhodgkison@hotmail.com), Sharon T. Balding, Akbar Zubaid, and Thomas H. Kunz
The aims of this study were to investigate the diet and relative abundance of fruit bats in a lowland Malaysian rain forest and to test the hypothesis that the local assemblage structure of fruit bats varies significantly over time in relation to the availability of food. In total, 352 fruit bats of eight species were captured during 72,306 m 2 mist-net hours of sampling between February 1996 and September 1999. Three species of fruit bats (Balionycteris maculata, Chironax melanocephalus, and Cynopterus brachyotis) that fed on a wide range of "steady state" and "big bang" food resources were captured continuously throughout the study period, with no significant variation in capture rates over time. In contrast, five species that fed exclusively or almost exclusively on "big bang" food resources were sampled intermittently, with significant temporal variation in the capture rates of two species (Cynopterus horsfieldi and Megaerops ecaudatus). Significant variation in the capture rates of the remaining three species (Dyacopterus spadiceus, Eonycteris spelaea, and Rousettus amplexicaudatus) could not be detected due to small sample sizes. Since ephemeral "big bang" food resources were only sporadically available within the study area and were associated with large canopy trees and strangler figs, these results suggest that food abundance, or the availability of specific food items, may be important factors limiting local fruit bat species diversity in old-growth Paleotropical rain forest. Thus, only three fruit bat species were locally resident within the forest throughout the study period. Therefore, further studies on the ranging behavior and habitat requirements of Malaysian fruit bats are required to assess the adequacy of existing reserves and protected areas.
Avian Geophagy and Soil Characteristics in Southeastern Peru
Donald J. Brightsmith (djb4@duke.edu) and Romina Aramburú Muñoz-Najar
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 Río Tambopata en el sureste del Perú. Nuestro estudio utiliza observaciones de aves y análisis de suelos de ocho secciones expuestas de los bancos de río 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 partículas 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 características de suelos disponibles.
Variación Estacional de un Ensamble de Aves en un Bosque Subtropical Semiarido del Chaco, Argentino
Mariano Codesido (marianolucas@hotmail.com) and David Bilenca
We studied seasonal variation in bird assemblages in a Chaco subtropical semiarid forest, Santiago del Estero Province, Argentina. We carried out seven samplings during both breeding and non breeding periods, in order to assess the resident status and the trophic guild of each species. During the last four samplings we recorded bird populations using 30 fixed-radius points, in order to estimate bird density, species density, evenness, and species diversity. We found that: (1) the bird assemblage had 96 species (67 residents, 19 summer migrants, 1 winter migrant, 5 of doubtful residency and 4 species whose resident status was unknown); (2) higher values of species density, evenness and species diversity were found during breeding periods; and (3) higher community attributes were followed by higher densities of 4 trophic guilds: nectarivores, frugivores and short and long-flight insectivores during the breeding periods. Changes in guild densities were probably associated with the arrival of summer migrants and to seasonal fluctuations in food resources, which in turn promoted seasonal changes in species density and diversity. Different from observations in other avian assemblages of the Chaco, no temporal variations were observed in the terrestrial seedeaters guild. This could be due to the fact that our study site forests are located in a landscape matrix with agricultural fields and grasslands that may offer year-round seed supply. The Chaco subtropical semiarid forest seems to be an important breeding habitat for many migrant species from both Neotropical and Nearctic regions.
Entre 1997 y 1999, se analizaron las variaciones estacionales de los atributos comunitarios (diversidad, densidad de especies y equitatividad) y de la densidad de gremios tróficos en un ensamble de aves del bosque subtropical semiárido del Chaco argentino. Se realizaron siete muestreos que abarcaron tanto los períodos reproductivos como los no reproductivos, lo que permitió clasificar a las especies según su estatus de residencia. En los cuatro últimos de esos siete muestreos se dispusieron 30 puntos de conteo de radio fijo dentro del bosque para hacer las estimaciones de densidad, densidad de especies, equitatividad y diversidad de aves. Los resultados indicaron: (1) que el ensamble estuvo compuesto por 96 especies (67 residentes, 19 migrantes estivales, 1 migrante invernal, 5 de residencia dudosas y 4 accidentales); (2) que los mayores valores de diversidad, densidad de especies y equitatividad se observaron durante períodos reproductivos; y (3) que los cambios en estos atributos comunitarios estuvieron acompañados por aumentos significativos en las densidades de los gremios de nectarívoras, insectívoras de vuelo corto, insectívoras de vuelo largo y frugívoras durante los períodos reproductivos. Es probable que los cambios estacionales observados en estos gremios estén asociados al aporte del componente migratorio estival y respondan a los incrementos en los niveles de recursos (néctar, frutos e insectos voladores) que tienen lugar en estos ambientes durante la estación húmeda. Estos cambios gremiales son los que en definitiva promueven los aumentos de los atributos comunitarios. A diferencia de lo observado para otros ensambles de aves en el Chaco, no detectamos variaciones temporales en el gremio de las semilleras terrestres. Esto podría deberse a que en el área de estudio los bosques están insertos en una matriz de paisaje que cuenta con áreas agrícolas y de pastizales que probablemente provean ofertas sostenidas de semillas a lo largo de todo el año. Es importante destacar la importancia de los bosques subtropicales semiáridos Chaqueños como hábitat de reproducción para las especies migrantes neotropicales y neárticas.
Spatial Ecology of Puerto Rican Boas (Epicrates inornatus) in a Hurricane Impacted Forest
Joseph M. Wunderle Jr. (wunderle@coqui.net), Javier E. Mercado, Bernard Parresol, and Esteban Terranova
Spatial ecology of Puerto Rican boas (Epicrates inornatus, Boidae) was studied with radiotelemetry in a subtropical wet forest recovering from a major hurricane (7-9 yr previous) when Hurricane Georges struck. Different boas were studied during three periods relative to Hurricane Georges: before only; before and after; and after only. Mean daily movement per month increased throughout the three periods, indicating that the boas moved more after the storm than before. Radio-tagged boas also became more visible to observers after the hurricane. Throughout the three periods, the sexes differed in movements, with males moving greater distances per move and moving more frequently than females. Males showed a bimodal peak of movement during April and June in contrast to the females' July peak. Sexes did not differ in annual home range size, which had a median value of 8.5 ha (range = 2.0-105.5 ha, N = 18) for 95 percent adaptive kernal. Females spent more time on or below ground than did males, which were mostly arboreal. Trees used by boas had larger diameters and more vines than random trees. Hurricane winds that strip leaves, vines, and branches from trees may reduce cover for boas and limit access to arboreal sites, at least for several years until succession brings about recovery with increased vine growth. Boas were especially difficult to observe; telemetrically monitored boas were detected visually at an average of only 15 percent of their fix sites, indicating that the species is more abundant than generally perceived.
La ecología espacial de las boas Puertorriqueñas (Epicrates inornatus; Boidae) fue estudiada con radio telemetría en un bosque subtropical lluvioso, en recuperación de un fuerte huracán (7-9 años antes) cuando el Huracán Georges azotó la isla. Varias boas fueron estudiadas durante tres períodos relativos al Huracán Georges: antes, antes y después, y después del huracán. El desplazamiento diario promedio por mes se incrementó a lo largo de los tres períodos, indicando que las boas se desplazaron más después que antes de la tormenta. Las boas con radio transmisor eran más visibles a los observadores después del huracán. El desplazamiento de los sexos difirió a lo largo de los tres períodos, recorriendo los machos mayor distancia por movimiento y desplazándose con mayor frecuencia que las hembras. Los machos mostraron un desplazamiento bimodal, con picos en abril y junio, en contraste de las hembras donde el pico fue en julio. Los sexos no difirieron en el tamaño del territorio, el cual presenta una mediana de 8.5 ha (intervalo = 2.0-105.5 ha, N = 18) para el 95 por ciento adaptive kernal. Las hembras pasaron mayor tiempo encima o bajo tierra que los machos, los cuales eran principalmente arbóreos. Los árboles utilizados por las boas tenían un diámetro mayor y más lianas que árboles escogidos al azar. Los vientos huracanados que despojan a los árboles de sus hojas, lianas y ramas, pueden reducir la cobertura de las boas y limitar su acceso a ubicaciones arbóreas al menos por varios años hasta que la sucesión traiga consigo recuperación en incremento del crecimiento de lianas. Las boas estudiadas fueron especialmente difíciles de observar; boas seguidas con telemetría fueron detectadas visualmente en promedio en sólo el 15 por ciento de las veces buscadas, indicando que la especie posiblemente sea más abundante de lo que se percibe.
Respiratory Ecology of Macroinvertebrates in a Swamp-River System of East Africa
Lauren J. Chapman (lauren.chapman@mcgill.ca), Kimberly R. Schneider, Chrissy Apodaca, and Colin A. Chapman
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 sites 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) test 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.g., 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.
Escape Behavior of Neotropical Homopterans in Response to a Flush-Pursuit Predator
Mark L. Galatowitsch and Ronald L. Mumme (rmumme@allegheny.edu)
Insect defenses against avian predators often include both a primary defense that reduces the probability of being attacked and a secondary defense, typically escape behavior, employed if the primary defense fails. Escape behavior, however, can make insects potentially vulnerable to specialized flush-pursuit predators. Neotropical Redstarts of the genus Myioborus (Parulidae) exploit insect escape behavior by using their contrasting black-and-white plumage and animated foraging behavior to startle insect prey that are then pursued and captured in flight. We examined how insect primary defense strategy and natural variation in Myioborus plumage pattern influence escape behavior in six species of homopterans from Monteverde, Costa Rica. The six homopterans included two aposematic species of the family Cercopidae (Ocoaxo sp. and Sphenorhina sp.), two cryptic species of the family Cixiidae (both Bothriocera spp.), and two structurally defended species of the family Membracidae (Campylocentrus sp. and Vestistilus variabilis). We measured the distance at which models of Myioborus Redstarts elicited escape behavior in insects under field conditions. Response distances varied significantly with both homopteran primary defense and Myioborus plumage pattern. Structurally defended homopterans were the most sensitive to the models and cryptic homopterans were the least sensitive. The model simulating the plumage of endemic M. miniatus comptus of Costa Rica elicited greater responses than did models of other Myioborus taxa with either less or more white in the plumage. Our results suggest that (1) primary defense strategies can have a significant effect on insect vulnerability to flush-pursuit predators, and (2) geographic variation in the plumage pattern of Myioborus Redstarts may reflect adaptation to regional prey and habitat characteristics that maximizes flush-pursuit foraging performance.
Las defensas de los insectos contra aves depredadoras, frecuentemente incluye dos tipos de defensa: una primaria, que disminuye la probabilidad de ser atacado, y una defensa secundaria típica de comportamiento de escape, la cual es empleada si falla la defensa primaria. Sin embargo, el comportamiento de escape puede ocasionar que los insectos sean potencialmente vulnerables a depredadores especializados en vuelo y persecusión. Los colirrojos neotropicales del género Myioborus (Parulidae) explotan el comportamiento de escape de los insectos usando su plumaje contrastante blanco-negro, y su comportamiento de forrajeo animado para sobresaltar a los insectos a cazar, que luego son perseguidos y capturados en vuelo. Nosotros examinamos cómo la defensa primaria de insectos y la variación natural del plumaje en Myioborus influye en el comportamiento de escape en seis especies de homópteros de Monteverde, Costa Rica. Los seis homópteros estudiados incluyeron dos especies conspicuas de la familia Cercopidae (Ocoaxo esp. y Sphenorhina esp.), dos especies enigmáticas de la familia Cixiidae (ambos Bothriocera esp.), y dos especies de la familia Membracidae (Campylocentrus esp. y Vestistilus variabilis) que se defienden estructuralmente. Nosotros medimos la distancia en la cual los modelos colirrojos de Myioborus provocan el comportamiento de escape en insectos bajo de condiciones de campo. Las respuestas a las distancias variaron significativamente en ambas, en defensa primaria de los homópteros y el patrón del plumaje de los Myioborus. Los homópteros que se defienden estructuralmente fueron los más vulnerables a los modelos, y los homópteros enigmáticos los menos vulnerables. El modelo simulando el plumaje del colirrojo M. miniatus comptus endémico de Costa Rica, produjo mayor respuesta que los otros modelos Myioborus de otras taxas con menos o más color blanco en su plumaje. Los resultados de este estudio sugieren que: (1) las defensas de estrategia primaria pueden tener un efecto significativo en la vulnerabilidad de los insectos a los depredadores que vuelan y persiguen; y (2) la variación geográfica en el patrón del plumaje de los Myioborus colirrojos puede indicar adaptaciones a presas por regiones y a características del hábitat que maximizan su habilidad de volar y perseguir.
Spatial Distribution Patterns of Jumping Spiders Associated with Terrestrial Bromeliads
Gustavo Q. Romero (gqromero@unicamp.br) and João Vasconcellos-Neto
The jumping spiders Eustiromastix nativo, Psecas sumptuous, and Uspachus sp. n. (Salticidae) live on terrestrial bromeliads in areas with different phytophysiognomies in southeastern and northeastern Brazil. To understand these spider-plant interactions, we investigated if (1) these spiders were associated specifically with bromeliads, (2) the spiders utilized particular bromeliad species, and (3) plant size and density of bromeliads affected spider distribution. The jumping spiders were not found outside bromeliads, indicating a strict spider-plant association. Eustiromastix and Uspachus occupied bromeliads in open areas, whereas Psecas was found on forest bromeliads. Eustiromastix occurred at a higher frequency on larger bromeliads and in patches with higher bromeliad density. This is one of the few studies to demonstrate specific relationships between jumping spiders and a particular plant type.
As aranhas saltadoras Eustiromastix nativo, Psecas sumptuosus e Uspachus sp. n. (Salticidae) vivem sobre bromélias terrestres em áreas com diferentes fitofisionomias no sudeste e nordeste do Brasil. Para compreender estas interações aranha-planta, nós investigamos se (1) estas aranhas estavam associadas especificamente a bromélias, (2) as aranhas utilizam espécies particulares de bromélias e (3) tamanho e densidade das bromélias afetam a distribuição das aranhas. As aranhas saltadoras não foram encontradas fora das bromélias, indicando uma associação estrita entre aranha e planta. Eustiromastix e Uspachus ocuparam bromélias em áreas abertas enquanto Psecas foi encontrada em bromélias de floresta. Eustiromastix ocorreu em maior freqüência sobre bromélias maiores, e em manchas com maior densidade de bromélias. Este estudo é um dos poucos a demonstrar relações específicas entre aranhas saltadoras e um tipo particular de planta.
Influences of Fruit Diversity and Abundance on Bird Use of Two Shaded Coffee Plantations
Tomás A. Carlo (carlo@colorado.edu), Jaime A. Collazo, and Martha J. Groom
We studied avian foraging at two shaded coffee plantations in Ciales, Puerto Rico. Both coffee plantations contained patches of second-growth forest but differed in shade types; one was a rustic plantation with a species-diverse shade including many fruiting plant species and the other was a commercial polyculture shaded almost solely by Inga vera. We quantified foraging activity of five fruit-eating bird species (Euphonia musica, Loxigilla portoricensis, Nesospingus speculiferus, Spindalis portoricensis, and Vireo altiloquous) and monthly fruit abundance in the coffee plantation and adjacent second-growth forest habitats at each site. Fruits comprised more than 50 percent of the diets for four of five focal bird species. We found a significant difference in the number of foraging records for focal bird species between coffee and forest habitats in the commercial polyculture but found few differences between these habitats in the rustic coffee farm. Overall, foraging activity was positively correlated with the abundance of fruits across study sites. Bird foraging was concentrated on plant species in the genera Cecropia, Miconia, Schefflera, Phoradendron, and Guarea, which together accounted for over 50 percent of frugivory records. Plant species in such genera fruited over prolonged time periods and provided birds with a fairly constant fruit supply. Our findings underscore the importance of fruiting plant species in making coffee plantations suitable habitat for birds and suggest that native fruiting plants be incorporated in coffee farms for avian conservation.
Estudiamos el forrajeo de aves frugívoras en dos plantaciones de café de sombra en Ciales, Puerto Rico. Ambas plantaciones contenían parches de bosque de crecimiento secundario, pero se diferenciaban por el tipo de sombra: una era "rústica" con una gran diversidad de especies de sombra, incluyendo muchas especies de plantas frutales, y la otra era un "policultivo comercial" sombreada casi únicamente por Inga vera. En cada sitio, cuantificamos la actividad de forrajeo de cinco especies de aves frugívoras (Euphonia musica, Loxigilla portoricensis, Nesospingus speculiferus, Spindalis portoricensis, Vireo altiloquous), y la abundancia mensual de frutos en los cafetales y en los bosques adyacentes. Las frutas comprendieron más del 50 por ciento de la dieta de cuatro de las cinco especies de aves en estudio. Encontramos diferencias significativas en el número de registros de forrajeo de especies de aves entre los habitats de café y bosque en el policultivo comercial, pero encontramos pocas diferencias entre estos habitats en la granja de café rústico. En general, la actividad de forrajeo estuvo positivamente correlacionada con la abundancia de frutos a través de los sitios de estudio. El forrajeo de las aves estuvo centrado en especies de plantas de los géneros Cecropia, Guarea, Schefflera, y Phoradendron, que juntas abarcaron por encima del 50 por ciento de los registros de frugivoría. Especies de plantas en estos géneros fructificaron por un período de tiempo más prolongado y surtieron constantemente a las aves de frutas. Nuestros hallazgos resaltan la importancia de las especies de plantas frutales en convertir las plantaciones de café en hábitats adecuados para las aves, y sugiere que las plantas frutales nativas deberian ser incorporadas en las granjas de café para la conservación de las aves.
Forest Modification Affects Diversity, But Not Dynamics of Speciose Tropical Pyraloid Moth Communities
Konrad Fiedler (konrad.fiedler@univie.ac.at) and Christian H. Schulze
We studied temporal and spatial dynamics of extremely diverse moth ensembles (Lepidoptera: Pyraloidea) along a gradient of forest disturbance ranging from undisturbed primary tropical rain forest to different kinds of modified forest and open cultivated land at the margin of Mount Kinabalu National Park (Sabah, East Malaysia). We sampled moths by light trapping during two periods (March-May and August-September 1997). We collected a total of 7724 individuals representing 680 species during 78 light-trapping nights at six study sites. Species diversity (Fisher's a) of ensembles in undisturbed primary forest was distinctly higher than in disturbed or secondary forest. More pyraloid moths were attracted in undisturbed primary forest. Samples from disturbed primary or old-growth secondary forest were statistically indistinguishable from the undisturbed primary forest ensemble in regard to species composition. Thus, pyraloid ensembles from disturbed forest with tall trees remaining appeared to represent impoverished subsets of the undisturbed primary forest community. The more heavily disturbed sites had a distinct fauna and showed a stronger faunal differentiation among each other. Four species of the genus Eoophyla, in which aquatic larvae feed on algae in fast-running streams benefited prominently from forest disturbance. Temporal variation of ensembles was remarkably concordant across the disturbance gradient. Relative abundance variation of the commonest species was identical at all sites. Overall, pyraloid moths responded more sensitively to anthropogenic habitat alteration than most other moth taxa studied thus far in tropical regions and allowed for an analysis of diversity patterns at a high temporal resolution.
Do Species Dominance Indices Indicate Rain Forest Disturbance by Logging?
Matti Nummelin (Matti.Nummelin@Formin.Fi) and Seppo Kaitala
Species distributions of several insect groups in unlogged and adjacent logged forest were analyzed from several published data sets. The slope of the geometric series model and dominance indices proved to be unsuitable indicators of rain forest disturbance.
De un conjunto de datos publicados, se analizó la distribución de varias especies de grupos de insectos en un bosque sin deforestar y adjacente a un bosque deforestado. La pendiente del modelo de serie geométrico y los índices de dominación probaron ser indicadores no adecuados de perturbaciones del bosque lluvioso.
The Striped Squirrel (Tamiops swinhoei hainanus) as a Nectar Robber of Ginger (Alpinia kwangsiensis)
Xao-Bao Deng, Pan-Yu Ren, Jiang-Yun Gao, and Qing-Jun Li (qjlixtbg@bn.yn.cninfo.net)
Nectar robbing by squirrels is reported for the first time in the striped squirrel (Tamiops swinhoei hainanus), which was found robbing nectar from ginger plants (Alpinia kwangsiensis) in tropical forests of south Yunnan, China. We describe the behavior of squirrels visiting inflorescences, and we compare the fruit set of inflorescences visited by squirrels with that of inflorescences not subject to nectar robbing by squirrels. Most of the styles of robbed flowers were damaged and the affected plants exhibited reduced fruit set.
Logging Speeds Little Red Fire Ant Invasion of Africa.
Peter D. Walsh (pdwalsh@earthlink.net), Phillipp Henschel. Kate A. Abernethy, Caroline E.G. Tutin, Paul Telfer, and Sally A. Lahm
Here, we document the invasion of equatorial Africa by the little red fire ant (Wasmannia auropunctata). Commercial logging and other forms of natural resource extraction have catapulted W. auropunctata into the interior of Gabon at a rate 60 times faster than the unassisted rate we measured over 19 years at the Lope Reserve. We also present photographic evidence suggesting that W. auropunctata is negatively affecting the country's exceptionally rich and intact large mammal fauna.
Nous documentons l'invasion de l'Afrique Equatoriale par la fourmi électrique (Wasmannia auropunctata). L'exploitation forestire et les autres formes d'extraction des ressources naturelles ont catapulté Wasmannia auropunctata l'intérieur du Gabon un rythme 60 fois plus rapide que la progression non assistée que nous avons mesurée sur 19 ans la Réserve de la Lopé. Nous présentons également des photographies suggérant que Wasmannia auropunctata a un impact négatif sur la faune de grands mammifres exceptionnellement riche et intacte du pays.
The Azteca-Cecropia Association: Are Ants Always Necessary for Their Host Plants?
Sarita B. Fáveri (sarita@inpa.gov.br) and Heraldo L. Vasconcelos
We assessed the effects of Azteca alfari presence on herbivory and growth of saplings for two Amazonian Cecropia species. For both species, rates of herbivory were low and did not differ between ant-removed and ant-maintained plants. Plant growth, measured over six months, was also similar among treatments. This is the first experiment to show that in its native mainland habitat, Cecropia may suffer low incidence of attack by insect herbivores in the absence of associated ants.
Nós testamos os efeitos da presença de Azteca alfari sobre a herbivoria e crescimento em arvoretas de duas espécies de Cecropia, na Amaznia. Para ambas espécies, as taxas de herbivoria foram baixas e não diferiram entre plantas que tiveram as formigas removidas ou mantidas. O crescimento das plantas, medido após seis meses, também foi similar entre os tratamentos. Este é o primeiro experimento que mostra que em seu hábitat natural, Cecropia pode sofrer baixa incidência de ataque por herbívoros na ausência das formigas associadas.