Remote Sensing Research Priorities in Tropical Dry Forest Environments
G. A. Sánchez-Azofeifa, K. L. Castro, B. Rivard, M. R. Kalascka, and R. C. Harriss
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Size and Structure of Fine Root Systems in Old-growth and Secondary Tropical Montane Forests (Costa Rica)
Dietrich Hertel, Christoph Leuschner, and Dirk Hölscher
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Use-history Effects on Structure and Flora of Caatinga
Israel M. Pereira, Leonaldo A. Andrade, Everardo V. S. B. Sampaio, and Maria Regina V. Barbosa
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Do Tropical Storm Regimes Influence the Structure of Tropical Lowland Rain Forests?
Roland C. de Gouvenain and John A. Silander Jr.
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Ant Protection against Herbivory in Three Species of Tococa (Melastomataceae) Occupying Different Environments
Fabian A. Michelangeli
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Relationships between El Niño Southern Oscillation and Demographic Patterns in a Substitute Food for Collared Peccaries in Panama
T. Ticktin
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Pollinator Assemblages and Visitation Rates for 11 Species of Neotropical Costus (Costaceae)
Kathleen M. Kay and Douglas W. Schemske
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Foraging Patterns of Sympatric Hornbills during the Nonbreeding Season in Arunachal Pradesh, Northeast India
Aparajita Datta and G. S. Rawat
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Seed Predation in Neotropical Pre-montane Pastures: Site, Distance, and Species Effects
F. Andrew Jones, Chris J. Peterson, and Bruce L. Haines
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Macroecology of Aquatic Insects: A Quantitative Analysis of Taxonomic Richness and Composition in the Andes Mountains of Northern Ecuador
Robert W. Sites, Michael R. Willig, and Marc J. Linit
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Variation in Growth and Demography of a Knob-scaled Lizard (Xenosaurus newmanorum: Xenosauridae) from a Seasonal Tropical Environment in México
Julio A. Lemos-Espinal, Geoffrey R. Smith, and Royce E. Ballinger
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Biannual Cycles of the Cinnamon-bellied Flowerpiercer
Jorge E. Schondube, Eduardo Santana C., and Irma Ruán-Tejeda
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Bat Mobility and Roosts in a Fragmented Landscape in Central Amazonia, Brazil
Enrico Bernard and M. Brock Fenton
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Bat Species Richness in Atlantic Forest: What Is the Minimum Sampling Effort?
Helena Godoy Bergallo, Carlos E. L. Esbérard, Marco Aurélio Ribeiro Mello, Viviane Lins, Renato Mangolin, Glauce G. S. Melo, and Márcia Baptista
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Florivory by the Crab Armases angustipes (Grapsidae) Influences Hummingbird Visits to Aechmea pectinata (Bromeliaceae)
Maria Bernadete F. Canela and Marlies Sazima
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Contrasting Responses to Induction Cues by Ants Inhabiting Contrasting Responses to Induction Cues by Ants Inhabiting Maieta guianensis (Melastomataceae)
David M. Lapola, Emilio M. Bruna, and Heraldo L. Vasconcelos
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Remote Sensing Research Priorities in Tropical Dry Forest Environments
G. A. Sánchez-Azofeifa (arturo.sanchez@ualberta.ca), K. L. Castro, B. Rivard, M. R. Kalascka, and R. C. Harriss
Satellite multi- and hyper-spectral sensors have evolved over the past three decades into powerful monitoring tools for ecosystem processes. Research in temperate environments, however, has tended to keep pace with new remote sensing technologies more so than in tropical environments. Here, we identify what we consider to be three priority areas for remote sensing research in Neotropical dry forests. The first priority is the use of improved sensor capabilities, which should allow for better characterization of tropical secondary forests than has been achieved. Secondary forests are of key interest due to their potential for sequestering carbon in relatively short periods of time. The second priority is the need to characterize leaf area index (LAI) and other biophysical variables by means of bidirectional reflectance function models. These biophysical parameters have importance linkages with net primary productivity and may be estimated through remote sensing. The third priority is to identify tree species using hyper-spectral imagery, which represents an entirely new area of research for tropical forests that could have powerful applications in biodiversity conservation.
En las últimas tres decadas, los sensores satelitales multi e hiper-espectrales han evolucionado hasta convertirse en importantes herramientas para el monitoreo de los ecosistemas. La investigación en los ecosistemas templados y boreales ha seguido el paso de los avances en los sistemas de percepción remota, mientras que en los sistemas tropicales existe un desface significativo. En este artículo identificamos y revisamos tres prioridades básicas en la investigación basada en sensores remotos de las regiones neotropicales del bosque seco. Estas prioridades están relacionadas con el monitoreo de bosques secundarios, el desarrollo de estudios relacionados con la cuantificación del área foliar por medio de métodos ópticos y finalmente el desarrollo de técnicas, que ligadas a información hiper-espectral, puedan ser utilizadas para la identificación de especies de árboles en zonas tropicales. Esta última prioridad representa una nueva área de investigación en los bosques tropicales con importantes connotaciones para la conservación de la biodiversidad biológica.
Size and Structure of Fine Root Systems in Old-growth and Secondary Tropical Montane Forests (Costa Rica)
Dietrich Hertel, Christoph Leuschner (cleusch@gwdg.de), and Dirk Hölscher
The fine root systems of three tropical montane forests differing in age and history were investigated in the Cordillera Talamanca, Costa Rica. We analyzed abundance, vertical distribution, and morphology of fine roots in an early successional forest (10-15 years old, ESF), a mid-successional forest (40 years old, MSF), and a nearby undisturbed old-growth forest (OGF), and related the root data to soil morphological and chemical parameters. The OGF stand contained a 19 cm deep organic layer on the forest floor (i.e., 530 mol C/m 2 ), which was two and five times thicker than that of the MSF (10 cm) and ESF stands (4 cm), respectively. There was a corresponding decrease in fine root biomass in this horizon from 1128 g dry matter/m 2 in the old-growth forest to 337 (MSF) and 31 g/m 2 (ESF) in the secondary forests, although the stands had similar leaf areas. The organic layer was a preferred substrate for fine root growth in the old-growth forest as indicated by more than four times higher fine root densities (root mass per soil volume) than in the mineral topsoil (0-10 cm); in the two secondary forests, root densities in the organic layer were equal to or lower than in the mineral soil. Specific fine root surface areas and specific root tip abundance (tips per unit root dry mass) were significantly greater in the roots of the ESF than the MSF and OGF stands. Most roots of the ESF trees (8 abundant species) were infected by VA mycorrhizal fungi; ectomycorrhizal species (Quercus copeyensis and Q. costaricensis) were dominant in the MSF and OGF stands. Replacement of tropical montane oak forest by secondary forest in Costa Rica has resulted in (1) a large reduction of tree fine root biomass; (2) a substantial decrease in depth of the organic layer (and thus in preferred rooting space); and (3) a great loss of soil carbon and nutrients. Whether old-growth Quercus forests maintain a very high fine root biomass because their ectomycorrhizal rootlets are less effective in nutrient absorption than those of VA mycorrhizal secondary forests, or if their nutrient demand is much higher than that of secondary forests (despite a similar leaf area and leaf mass production), remains unclear.
Use-history Effects on Structure and Flora of Caatinga
Israel M. Pereira (pereiraim@hotmail.com), Leonaldo A. Andrade, Everardo V. S. B. Sampaio, and Maria Regina V. Barbosa
Floristic composition and vegetation structure of plants 3 cm stem diameter or greater were compared at four sites in the Agreste of Paraíba, Brazil: (1) little disturbed for five decades (LD); (2) grazed fragment, selectively logged 16 years before sampling (GF); (3) naturally regrowing for 30 years after 39 years of agriculture (OR); and (4) naturally regrowing for 20 years after 35 years of agriculture plus 15 years of pasture (NR). Cattle graze frequently in the last three sites but very seldom in LD. The little disturbed site had more species (53) than the other three sites (36, 25, and 11 species in GF, OG, and NG, respectively) and also more (3253, 2780, 2780, and 2115 plants/ha) and larger plants (34.8, 26.8, 18.6, and 7.8 m 2 /ha), including taller tree species (up to 15 m) absent in the other sites (maximum height: 14, 6, and 5 m). Differences were striking in relation to NR, the site with longer use and shorter regrowth period, which was strongly dominated by only two species: Mimosa tenuiflora (73% relative density and 81% basal area) and Piptadenia stipulacea (21% relative density and 16% basal area). These results indicate that abandoned agricultural sites may take several decades to reestablish vegetation similar to the original.
Foram comparadas a composião florística e a estrutura da vegetaão das plantas com dimetro do caule >= 3 cm, em quatro áreas no Agreste da Paraíba: (1) pouco perturbada por cinco décadas (LD); (2) fragmento pastejado que teve corte seletivo de árvores 16 anos antes da amostragem (GF); (3) revegetaão natural por 30 anos depois de 39 anos de agricultura (OR); e (4) revegetaão natural por 20 anos depois de 35 anos de agricultura e 15 anos como pasto plantado (NR). Gado bovino pasta frequentemente nas três últimas áreas e só raramente em LD. A área pouco perturbada tinha maior número de espécies (53) que as outras três áreas (36, 25 e 11 espécies em GF, OR e NR, respectivamente), além de plantas em maior número (3253, 2780, 2780 e 2115 plantas/ha) e de maior tamanho (34.8, 26.8, 18.6 e 7.8 m 2 /ha), incluindo espécies arbóreas mais altas (até 15 m), ausentes nas outras áreas (alturas máximas de 14, 6 e 5 m). As diferenas foram marcantes em relaão a NR, área com maior tempo de uso e menor tempo de revegetaão, e dominada por apenas duas espécies: Mimosa tenuiflora (densidade e área basal relativas de 73 e 81%) e Piptadenia stipulacea (21% de densidade e 16% de área basal). Os resultados indicam que as áreas de agricultura abandonadas podem levar décadas até estabelecerem vegetaão semelhante original.
Do Tropical Storm Regimes Influence the Structure of Tropical Lowland Rain Forests?
Roland C. de Gouvenain (roland.degouvenain@uconn.edu) and John A. Silander Jr.
It has been suggested that the average canopy height of Madagascar's lowland rain forests is shorter and the average tree density is greater than in other tropical lowland rain forests of the world. The cause was hypothesized to be frequent cyclone disturbances. We compared the structure of the lowland rain forests in Madagascar to the structure described in published accounts of other tropical lowland rain forests. We found that the eastern coastal lowland forests of Madagascar have short canopy heights relative to that of many other lowland tropical rain forests, and that these Malagasy forests also have relatively high tree densities. On a worldwide basis, there is a significant correlation between short forest canopies and occurrence of tropical cyclones. This association between high tree density and occurrence of tropical cyclones is valid for Africa, but the pattern does not hold up globally.
Il a été conjecturé que la taille moyenne de la canopée des forêts basses ombrophiles de Madagascar est moindre, et que la densité des arbres est plus grande, que pour d'autres forêts tropicales ombrophiles du monde. L'hypothèse a été avancée que les perturbations fréquentes des cyclones en sont la cause. Nous avons comparé la structure des forêts ombrophiles de basse altitude de Madagascar avec la structure d'autres forêts tropicales ombrophiles du monde. La hauteur de la canopée des forêts de l'est de Madagascar est relativement plus courte que celles de beaucoup d'autres forêts tropicales humides de basse altitudes, et la densité des arbres est relativement élevée. A l'échelle globale, il y a une relation entre courte canopée et perturbations par les cyclones. La relation entre densité des arbres et perturbations par les cyclones est validée par cette étude seulement pour le continent Africain.
Ant Protection against Herbivory in Three Species of Tococa (Melastomataceae) Occupying Different Environments
Fabian A. Michelangeli (fabian@nybg.org)
The genus Tococa is comprised of 47 species of small trees and shrubs distributed from southern Mexico to Bolivia. About 30 of the species have ant domatia that develop at the base of the leaf blade or at the apex of the petiole. Ant exclusion experiments on three different species of Tococa occupying different environments were carried out to assess their effect in protecting the plant against herbivores. Additionally, ant behavior was monitored in control plants to study how they might be conferring protection against herbivory. Herbivory was significantly lower on control plants (ants maintained) than on experimental plants (ants removed), demonstrating the role of the ants as defenses against herbivores. Herbivory rates in open and disturbed areas were higher than in the forest understory. Ant exclusion experiments showed that both timid and aggressive ants protect their host plants against potential herbivores by killing or warding off scouts of leaf-cutter ants (Atta sp.) and removing the eggs of Lepidoptera and Coleoptera from the surface of the plants.
El género Tococa esta compuesto por 47 especies de arbustos y árboles pequeños distribuidos desde el sur de México hasta Bolivia. Cerca de 30 especies poseen domacios que se desarrollan en la base de la lámina de la hoja o en el ápice del pecíolo. Se llevaron a cabo experimentos de exclusión de hormigas en tres especies de Tococa en distintos hábitat con el fin de evaluar su rol potencial de protección contra la herbivoría. Adicionalmente, se observó el comportamiento de las hormigas en las plantas del grupo control con el fin de estudiar su papel como defensa contra los herbívoros. Las diferencias en las tasas de herbivoría entre plantas con y sin hormigas fue siempre significativa, demostrando así el rol de las hormigas como defensa contra los herbívoros. Además, en las zonas abiertas y secundarias, la cantidad de herbivoría fue siempre mayor que en el dosel del bosque. Estos experimentos también demuestran que tanto las hormigas tímidas como las agresivas protegen a las plantas que habitan, ya sea matando o ahuyentando los exploradores de las hormigas cortadoras de hoja (Atta sp.) o removiendo los huevos de Lepidoptera y Coleoptera de la superficie de las plantas.
Relationships between El Niño Southern Oscillation and Demographic Patterns in a Substitute Food for Collared Peccaries in Panama
T. Ticktin (ticktin@hawaii.edu)
Environmental fluctuations are recognized to play an important role in shaping demographic processes in plant and animal populations. On Barro Colorado Island (BCI), Panama, El Niño Southern Oscillation (ENSO) events followed by mild dry seasons have been shown to stimulate variation in community-wide fruit production. This variation has been postulated to lead to famine in frugivore and granivore populations, but few if any studies have assessed further implications for other members of the ecological community. This study examined the ways in which variation in fruit production associated with an El Niño event on BCI may influence demographic and evolutionary traits in a plant species that is only consumed by frugivores during periods of fruit scarcity. Specifically, I assessed the effects of herbivory by collared peccaries (Tayassu tajacu) on demographic rates and patterns in the terrestrial bromeliad, Aechmea magdalenae. Aechmea magdalenae usually suffers little or no herbivory, and rain forest collared peccaries, which are primarily frugivorous, have not previously been reported to eat this species. Rates of survival and reproduction of 296 A. magdalenae rosettes in three transects of differing densities were recorded from 1997 through 1999. Mortality rates due to herbivory increased significantly from 1997 to 1999 and showed a close correspondence with enhanced and then decreased rates of community-wide fruit production associated with the 1997 ENSO. The densest portions of the A. magdalenae population showed lower mortality rates and higher rates of reproduction than did the less dense regions. Over the study period, A. magdalenae populations decreased by 45 percent. The implications of periodic herbivory by hungry frugivores are discussed with respect to population regulation, seedling dispersal, and evolution of A. magdalenae's dense growth habit.
Se reconoce que las fluctuaciones climáticas juegan un papel importante en los procesos demográficos de las poblaciones de plantas y animales. En la isla Barro Colorado (BCI), Panamá, los fenómenos El Niño/Oscilación del Sur (ENOS), seguidos de períodos moderadamente secos, han producido variación en la producción de frutos a nivel de comunidades vegetales. Se ha propuesto que esta variación se asocia con las épocas de hambruna de las poblaciones de frugívoros y granívoros, pero hasta donde se sabe, ningún estudio ha investigado su impacto en otros miembros de la comunidad ecológica. Este estudio examina las formas en que la variación en la producción de frutos asociada con ENOS, puede influir las características evolutivas y demográficas de una especie vegetal que sólo es consumida por frugívoros durante períodos de baja producción de frutos. Específicamente, se examinan los efectos que la herviboría por pecarí de collar (Tayassu tajacu) tiene sobre las tasas y patrones demográficos de la bromelia terrestre Aechmea magdalenae. Aechmea magdalenae usualmente padece poca herviboría, y no existen reportes de pecaríes de collar alimentandose de ella. Entre 1997 y 1999 se registraron las tasas de supervivencia y reproducción de 296 rosetas de A. magdalenae en tres transectos con diferente densidad de rosetas. Las tasas de mortalidad debidas a la herbivoría se incrementaron significatívamente en este período y mostraron una estrecha correspondencia con las tasas decrecientes en la producción de frutos de la comunidad asociadas con el ENOS de 1997. Los transectos con mayor densidad de A. magdalenae mostraron tasas de mortalidad más bajas y tasas de reproducción más altas respecto a los transectos de menor densidad. A lo largo de todo el período del estudio, las poblaciones de A. magdalenae decrecieron un 45 porciento. Las implicaciones que ocasiona la herbivoría periódica por frugívoros hambrientos se discute en relación con la regulación de la población, dispersión de semillas, y evolución de los hábitos de crecimiento de A. magdalenae.
Pollinator Assemblages and Visitation Rates for 11 Species of Neotropical Costus (Costaceae)
Kathleen M. Kay (kaykathl@msu.edu) and Douglas W. Schemske
Most plant species in tropical forests are pollinated by animals, and yet the diversity and specificity of pollinator assemblages are poorly documented. Here, we investigated pollinator relationships for 11 species of understory herbs in the genus Costus, with the goal of documenting visitation rates and pollinator assemblages among a variety of habitats. For a subset of species, we documented pollinator visitation for multiple years and/or multiple sites to examine temporal and spatial variation in pollinator relationships. Furthermore, we examined the extent to which specialization in pollination systems can contribute to reproductive isolation for sympatric species. Each species was primarily pollinated by either euglossine bees or hummingbirds. Total visitation rates were generally low, averaging 3.2 visits per flower per hour for bee-pollinated species and 0.5 visits per flower per hour for hummingbird-pollinated species. All of the higher elevation species studied were hummingbird-pollinated, while low elevation species were pollinated either by euglossine bees or hummingbirds. Spatial and temporal variation in visitation rates and pollinator identities was minimal. Pollinator specificity was found to contribute strongly to reproductive isolation for the 11 pairwise combinations of sympatric species differing in pollination syndrome, in some cases functioning as a complete barrier to potential pollen flow.
La mayoría de las especies vegetales de los bosques tropicales son polinizadas por animales, pero la diversidad y las especies de los gremios de polinizadores son poco conocidas. En este trabajo investigamos las interacciones de los polinizadores de 11 especies de hierbas del sotobosque pertenecientes al género Costus, con el objetivo de documentar la frecuencia de visitas y los gremios de polinizadores en distintos hábitats. Para un subconjunto de las especies, documentamos las visitas de los polinizadores en varios años y/o sitios para examinar la variación espacial y temporal de las interacciones de los polinizadores. Además, examinamos como la especialización de los sistemas de polinización puede contribuir al aislamiento reproductivo de especies simpátricas. Cada especie fue polinizada principalmente ya sea por abejas euglosinas o colibríes. Las frecuencia de visitas fue baja en general, con un promedio de 3.2 visitas/flor/hora en las especies polinizadas por abejas y 0.5 visitas/flor/hora en las especies polinizadas por colibríes. Las especies localizadas a mayor altitud fueron polinizadas por colibríes, mientras que las de bajas elevaciones fueron polinizadas por ambos. La diferencia espacial y temporal en frecuencia de visitas e identidad de polinizadores fue mínima. Se encontró que la especificidad de los polinizadores contribuye al aislamiento reproductivo, en las 11 combinaciones reciprocas de especies simpátricas se observaron síndromes de polinización diferentes, que en algunos caso sirvieron como una barrera efectiva al flujo potencial de polen.
Foraging Patterns of Sympatric Hornbills during the Nonbreeding Season in Arunachal Pradesh, Northeast India
Aparajita Datta (aparajita@ncf-india.org) and G. S. Rawat
The diet and food resource partitioning of three sympatric hornbills (Great Hornbill Buceros bicornis, Wreathed Hornbill Aceros undulatus, and Oriental Pied Hornbill Anthracoceros albirostris) during the nonbreeding season were studied relative to fruit availability in a foothill semievergreen forest of Arunachal Pradesh, northeast India. Hornbills fed on fruits of 49 plant species that comprised over 95 percent of their diet. Hornbill species partitioned food resources by varying the relative contribution of figs and non-fig fruits in the diet. Similarity in non-fig fruit diet was low. Ten species contributed to over 90 percent of the non-fig diet. The availability of non-fig fruits was much lower in the nonbreeding season than in the breeding season; however, despite lower fruit availability during the nonbreeding season, hornbills had a wide diet breadth and indirect evidence suggests that Wreathed Hornbills foraged widely in this season for fruit. Great Hornbills relied more on figs that were available year-round. The diverse diet breadth that included rare and patchy fruit resources underscores the importance of conserving large forest tracts for hornbills.
Seed Predation in Neotropical Pre-montane Pastures: Site, Distance, and Species Effects
F. Andrew Jones (fajones@dogwood.botany.uga.edu), Chris J. Peterson, and Bruce L. Haines
We studied patterns of removal and predation on seeds of ten plant species over two years in four abandoned pastures adjacent to forest fragments in Costa Rica. We hypothesized that: (1) removal within pastures would be greater nearest forest fragments and decline at farther distances; (2) removal rates would be greater on smaller-seeded species; and (3) removal rates would differ among pastures. We placed seeds of two species in three pastures in 1997 and eight species in two pastures during 1998. In each pasture, removal was monitored at three distances from the forest edge. Rates of seed removal in 1997 and 1998 were significantly greater 1-5 m from the forest than at 20 m distances, but removal rates at the 40 m distance did not differ from the 1-5 m distance. Rates of removal for both species were low in 1997, although removal was significantly greater for the smaller-seeded species Sorocea trophoides than for the large seeds of Nectandra sp. Removal rates differed significantly among pastures for both species in 1997 and among pastures for five small-seeded species in 1998. No removal of three large-seeded species was detected in 1998. Interspecific differences in seed removal rates were consistent with the hypothesis that larger seeds are removed less in pastures than smaller seeds. While some seed removal patterns appear predictable, species-specific variation in removal within and among sites was substantial. Predator population densities and other among-pasture differences may also influence patterns of spatial variation in seed predation.
Estudiamos los patrones de remoción y depredación de semillas en diez especies de plantas durante dos años, en cuatro pastizales abandonados adyacentes a fragmentos de bosque en el sur de Costa Rica. Planteamos las siguientes hipótesis: 1) la remoción de semillas de los pastizales será mayor cerca a los bordes de los fragmentos y disminuirá a medida que la distancia al borde aumenta, 2) las tasas de remoción serán mayores para semillas pequeñas, 3) las tasas de remoción diferirán entre los diferentes pastizales. Colocamos semillas de dos especies de plantas en tres pastizales en 1997 y de ocho especies de plantas en dos pastizales en 1998. En cada pastizal monitoreamos la remoción de semillas a tres distancias del borde. Las tasas de remoción en ambos años fueron mayores a 1-5 m del borde que a 20 m, pero no fueron significativamente diferentes de las tasas de remoción a 40 m. La tasa de remoción para ambas especies fue baja en 1997, aunque la remoción fue mayor para la especie con semillas pequeñas (Sorocea trophoides) que para la especie con semillas grandes (Nectandra sp.). Las tasas de remoción para estas especies fueron significatívamente diferentes entre los pastizales en 1997 y para 5 especies con semillas pequeñas en 1998. Ese mismo año, no detectamos remoción en ninguna de las 3 especies con semillas grandes. Aunque algunos de estos patrones de remoción de semillas parecen predecibles, hubo una variación substancial a nivel específico dentro y entre pastizales. Sugerimos que la densidad poblacional de los depredadores y otras diferencias bióticas y/o abióticas entre pastizales, pueden influenciar la variación espacial observada en la remoción de semillas.
Macroecology of Aquatic Insects: A Quantitative Analysis of Taxonomic Richness and Composition in the Andes Mountains of Northern Ecuador
Robert W. Sites (bugs@missouri.edu), Michael R. Willig, and Marc J. Linit
To determine the spatial dynamics of Neotropical lotic insect species, specimens were collected from 41 streams on the eastern and western flanks of the Andes Mountains in Ecuador. We examined the manner in which taxonomic richness and composition differed with elevation, latitude, and versant. Statistical analyses were limited to 5 families (Ephemeroptera: Baetidae, Leptohyphidae, Oligoneuriidae; Heteroptera: Naucoridae; Coleoptera: Elmidae), comprising 32 genera and 85 species, for which identifications or morphospecies assignments were reliable. Assessment of taxonomic diversity was based on the richness of genera and species at each site. In addition, each site was characterized by species richness within each of 4 families with more than 10 species. The effects of versant and transect on composition and structure were family-specific. Mean site differences between versants in elmid richness at generic and specific levels depended on transect. Only baetid richness was affected by versant and transect in a consistent manner. Variation among sites in composition based on all genera and species was captured using multidimensional scaling (MDS). Subsequent MANOVAs based on scores from MDS axes revealed that differences between versants were much stronger in the southern transect, although transects differed from each other at specific and generic levels. A Jaccard's similarity matrix was computed for each family to reflect the spatial organization of taxonomic composition. Mesogeographic patterns of species composition for each of the four families were correlated (Mantel analysis) at both the regional level and at the level of the entire study area. At the regional level, the only pair of families to exhibit correlated patterns of species composition was elmids and naucorids in the southwestern region. The pattern of species composition for each family was correlated with the patterns for one or more other families at the level of the entire study area. Thus, spatial dynamics of species composition was similar for the families examined, suggesting that the Andes exert a consistent influence on species distributions within families, regardless of ordinal affiliation. At a local scale, however, the way in which taxonomic composition changed with latitude and versant was family-specific. Mayflies, the most vagile of the taxa studied, had the highest percentage of species overlap between versants. Of three genera of Naucoridae collected, species of Ambrysus, of probable Mexican origin, were found only on the eastern versant, corroborating other evidence that the genus is recent in South America. Moreover, dispersion by Ambrysus across the Andes Mountains may not have occurred, as it has for Cryphocricos and Limnocoris, which are of probable South American origin.
Variation in Growth and Demography of a Knob-scaled Lizard (Xenosaurus newmanorum: Xenosauridae) from a Seasonal Tropical Environment in México
Julio A. Lemos-Espinal, Geoffrey R. Smith (smithg@denison.edu), and Royce E. Ballinger
We studied growth and demography in a population of Xenosaurus newmanorum, a lizard that lives in rock crevices in the tropical cloud forests of México. Growth rates varied with season (faster in the wet season) and year (faster in 1995 and 1997, slower in 1996 and 1999). Males and females did not differ in growth rate. Proportion of reproductive females varied from year to year, with 1996 having the lowest proportion of reproductive females (32.5%) compared to the other years (all >75%). The age/size structure changed slightly among years, but did not differ between the wet and dry seasons. On average, the sex ratio was female-biased; however, the proportion of males in the population was greater in the dry season than in the wet season. Our results suggest that, like other lizards, growth and demographic characteristics of this population fluctuate with the proximate environment on both a seasonal and annual timescale.
Estudiamos los patrones de crecimiento y la demografía de una población de Xenosaurus newmanorum, una especie de lagartija que vive en las grietas de las rocas de los bosques de niebla de México. La tasa de crecimiento corporal varió en función de la época del año (más rápida en la época húmeda), y en función del año (más rápida en 1995 y 1997, y más lenta en 1996 y 1999). No hubo diferencias significativas en las tasas de crecimiento corporal de machos y hembras. La proporción de hembras reproductivas varió de año a año, 1996 fue el año con menor proporción de hembras reproductivas (32.5%) comparado con el resto de los años (todos ellos >75%). La estructura de las clases de edad de esta población fluctuó levemente entre los años, pero no hubo diferencias entre las estaciones húmedas y secas. En promedio la proporción de sexos estuvo sesgada hacia las hembras; aunque la proporción de machos en la población fue mayor en la época seca que en la época húmeda. Nuestros resultados sugieren que, al igual que otras lagartijas, las características demográficas y de crecimiento corporal de esta población pueden fluctuar con base a factores próximos a escalas estacionales y anuales.
Biannual Cycles of the Cinnamon-bellied Flowerpiercer
Jorge E. Schondube (schondub@u.arizona.edu ), Eduardo Santana C., and Irma Ruán-Tejeda
Biannual cycles of reproduction and molt are rare in birds, with most species exhibiting a single annual cycle. We studied the breeding and molting phenology of the Cinnamon-bellied Flowerpiercer (Diglossa baritula), a nectar feeding passerine, in western Mexico. Monthly captures from December 1994 to May 1998 revealed clear biannual breeding and molting cycles. The two breeding seasons took place from January to April (dry season) and from July to October (rainy season). Their July to October breeding season coincided with the single breeding season exhibited by resident hummingbirds at our study site. Even though flowerpiercers and hummingbirds use the same food resources, hummingbirds only molt and breed once a year. Male flowerpiercers breed and molt flight feathers twice a year, whereas females appear to breed only once. A higher proportion of females bred in the rainy season (90%) than in the dry season (30%), and they underwent a complete molt only during the rainy season. Proportions of males in breeding condition during the dry and the rainy season were similar (86 and 92%). Some males (40%) showed an incomplete molt in the dry season, while most males (80%) underwent a complete molt in the rainy season. Differences in proportions of breeding and molting individuals between the dry and the rainy season suggest that the dry season cycle is limited by food availability. We hypothesize that D. baritula individuals use soft fruits (in addition to flowers) to fuel their breeding during the dry season.
Los ciclos bianuales de reproducción y muda son raros en las aves. La mayoría de las especies presentan un ciclo anual único. En este trabajo estudiamos la fenología reproductiva y de muda de Diglossa baritula, un paseriforme nectarívoro, en el occidente de México. Los muestreos mensuales con redes de niebla (Diciembre 1994 - Mayo 1998) mostraron que esta especie presenta ciclos bianuales de reproducción y muda. Las dos temporadas reproductivas ocurrieron en Enero-Abril (secas) y Julio-Octubre (lluvias). La temporada reproductiva de lluvias se traslapó con la temporada de reproducción única de los colibríes residentes en nuestra área de estudio. Aunque los colibríes y D. baritula utilizan los mismos recursos alimenticios, los colibríes se reproducen y mudan sólo una vez por año. Los machos de D. baritula se reprodujeron y mudaron plumas de vuelo dos veces por año, mientras que las hembras parecen hacerlo sólo una vez. Se reprodujeron más hembras en la temporada de lluvias (90%) que en la de secas (30%). Los porcentajes de machos en condición reproductiva fueron similares para las dos temporadas (secas 86% y lluvias 92%). Algunos machos (40%) mostraron una muda incompleta en la temporada de secas, mientras que la mayoría presentó una muda completa en la temporada de lluvias (80%). Las diferencias en las proporciones de individuos reproductivos/mudando entre la temporada seca y la temporada de lluvias sugieren que durante la temporada de secas la disponibilidad de recursos alimenticios es limitante. Conjeturamos que D. baritula combina flores y frutos blandos para satisfacer los requisitos energéticos de su reproducción durante la época seca.
Bat Mobility and Roosts in a Fragmented Landscape in Central Amazonia, Brazil
Enrico Bernard (ebernard@ufla.br) and M. Brock Fenton
In spite of the important role played by bats in tropical ecosystems, little is known about how they are affected by habitat fragmentation. By using a mark/recapture protocol and radiotelemetry techniques in a naturally fragmented landscape composed of primary forests and forest fragments surrounded by savannas in Alter do Chão, Pará State, Brazil, we were able to track the movements of various species of bats, calculate the size of the area used, locate roosts and potential feeding areas, and determine preferred flight routes. We marked 3440 bats belonging to 44 species and recaptured 151 belonging to 14 species. The average distance between extra-site recaptures was 2.2 km. With the exception of bats marked in fragments and recaptured in forests, all other possible inter-habitat recaptures were observed. We selected 23 bats of 8 species for radiotelemetry and the areas used by them varied from 65 to 530 ha. Some species restricted their activity to the vicinity of their roosts, rarely moving more than 500 m away, but others traveled greater distances between roosts and foraging areas. All tracked bats flew over savannas, crossing distances from 0.5 to 2.5 km. Roost location and type varied among species, from individuals roosting alone in the foliage to colonies in buildings. Bats were highly mobile and savannas did not appear to inhibit the movements of some species, suggesting that a persistent biological flow may be maintained among isolated fragments, with bats acting as pollinators and seed dispersers.
Apesar da importncia dos morcegos nos ecossistemas tropicais, pouco se sabe a respeito de como estes animais interagem com uma paisagem fragmentada. Apresentamos aqui dados sobre a mobilidade de morcegos em uma paisagem naturalmente fragmentada, composta por florestas e fragmentos florestais circundados por savanas em Alter do Chão, Estado do Pará, Brasil. Através de marcaão/recaptura e de rádio-telemetria conseguimos rastrear os movimentos de espécies selecionadas, calcular o tamanho da área usada, localizar abrigos e áreas potenciais de forrageio e apontar rotas preferidas de vo. Marcamos 3440 morcegos de 44 espécies e recapturamos 151 individuos de 14 espécies. A distncia média entre recapturas em sítios diferentes foi de 2.2 km. Com exceão dos morcegos que foram marcados em fragmentos e recapturados em florestas, todas as outras combinaes de recapturas entre habitats foram observadas. Selecionamos 23 morcegos de oito espécies para radio-telemetria e as áreas usadas por eles variaram entre 65 e 530 ha. Algumas espécies restringiram suas atividades ao redor dos abrigos, raramente afastando-se mais do que 500 m destes, enquanto outras deslocaram-se por distncias maiores entre os abrigos e as áreas de forrageio. Todos os morcegos rastreados cruzaram as savanas, cobrindo distncias de 0.5 a 2.5 km. O tipo e a localizaão dos abrigos variou entre as espécies, desde indivíduos abrigando-se sozinhos na folhagem até colnias em edificaes. Os morcegos apresentaram alta mobilidade e as savanas aparentemente não inibiram a movimentaão de algumas espécies, sugerindo que um fluxo biológico entre fragmentos pode persistir, tendo os morcegos como agentes polinizadores e dispersores de sementes.
Bat Species Richness in Atlantic Forest: What Is the Minimum Sampling Effort?
Helena Godoy Bergallo (bergallo@uerij.br), Carlos E. L. Esbérard, Marco Aurélio Ribeiro Mello, Viviane Lins, Renato Mangolin, Glauce G. S. Melo, and Márcia Baptista
Species lists are sources of information for studies of both conservation and macroecology. It is, however, important to differentiate between relatively complete lists and extremely incomplete ones. The aim of this study was to evaluate how sampling effort typically used in inventories affects the number of bat species captured in areas of Atlantic Forest in southeastern Brazil. We also evaluated if the number of sampled sites, size of the sampled area, and sampling effort (net hours) affect species richness. We used previously reported data from studies in Rio de Janeiro, São Paulo, and Minas Gerais States, and our own data collected during 1989 and 2001. Nonlinear models fit well the data for Rio de Janeiro and Minas Gerais States and all states together, but not for São Paulo State. Genera richness showed a similar pattern to that of species richness. The model used to explain the relationship between species richness and size of the study area, number of sites, and sampling effort sampled was significant. The number of sites sampled explained a significant part of the variation observed; however, other variables contributed nothing to the model, suggesting that capturing beta diversity is the most important aspect of biodiversity surveys for bats, and that increasing net hours at a given location is much more inefficient than distributing net hours across locations. We suggest 1000 captures as the minimum necessary when sampling with mist nets to capture the majority of phyllostomid species for a given site (alpha diversity). In addition, we suggest that shifting the position of the mist nets between nights will increase the probability of capturing more species.
As listas de espécies são fontes de informaes para estudos, tanto de conservaão quanto de macroecologia. Entretanto, é importante diferenciar entre listas relativamente completas daquelas seriamente incompletas. O objetivo deste estudo foi avaliar como o esforo amostral mínimo tipicamente usado em inventários afeta o número de espécies de morcegos capturados em áreas de Mata Atlntica do sudeste do Brasil. Nós também avaliamos se o número de pontos amostrados, o tamanho da área amostrada e o esforo de captura (hora-rede) afetam a riqueza de espécies. Nós usamos dados disponíveis de estudos desenvolvidos nos estados do Rio de Janeiro, São Paulo e Minas Gerais, e os nossos próprios dados coletados de 1989 a 2001. Modelos não-lineares se ajustaram para os estados do Rio de Janeiro e Minas Gerais e todos os estados juntos, mas não para o Estado de São Paulo. A riqueza de Gêneros mostrou o mesmo padrão da riqueza de espécies. O modelo usado para explicar a relaão entre riqueza de espécies e tamanho da área de estudo, número de pontos amostrados e esforo amostral foi significativo. O número de pontos amostrados explicou uma parte significante da variaão observada. Contudo, as outras variáveis não contribuíram para o modelo, sugerindo que capturar a diversidade Beta é o aspecto mais importante de inventários de biodiversidade para morcegos, e que o aumento de horas-rede numa dada localidade é muito mais ineficiente do que distribuir horas-rede entre localidades. Nós sugerimos 1000 capturas como o mínimo necessário para amostrar, com redes de neblina, a maioria das espécies de filostomídeos de uma dada área (diversidade Alfa). Adicionalmente, sugerimos que mudando a posião das redes entre noites aumentará a probabilidade de capturar um maior número de espécies.
Florivory by the Crab Armases angustipes (Grapsidae) Influences Hummingbird Visits to Aechmea pectinata (Bromeliaceae)
Maria Bernadete F. Canela (betec@hotmail.com) and Marlies Sazima
Armases angustipes (Grapsidae) crabs were recorded on 31.5 percent of Aechmea pectinata inflorescences, a common ornithofilous bromeliad in rain forests of southeastern Brazil. Crabs foraged mainly in the morning and used newly opened flowers, usually damaging the corolla, consuming the stamens and stigma, and interfering with hummingbird visits. This florivory may reduce the reproductive success of A. pectinata, both directly through consumption of flowers and indirectly by reducing pollinator visits.
Contrasting Responses to Induction Cues by Ants Inhabiting Contrasting Responses to Induction Cues by Ants Inhabiting Maieta guianensis (Melastomataceae)
David M. Lapola, Emilio M. Bruna (brunae@wec.ufl.edu), and Heraldo L. Vasconcelos
The two most common ant associates of the understory myrmecophyte Contrasting Responses to Induction Cues by Ants Inhabiting Maieta guianensis (Melastomataceae) respond in different ways to experimental cues associated with herbivory. While Pheidole minutula is induced by both physical damage and extracts of leaf tissue, Crematogaster laevis is induced by leaf damage only. We suggest such interspecific variation in induced responses is common and could influence the quality of defense against herbivores provided to host-plants of ants.
As duas formigas que mais comumente se associam com a mirmecófita de sub-bosque Maieta guianensis (Melastomataceae) respondem de maneiras diferentes a simulaes experimentais de herbivoria. Enquanto Pheidole minutula é induzida tanto por danos fisicoes e extratos de tecido foliar, Crematogaster laevise induzida apenas pelos danos físicos. Surgerimos que tal variaão interespecífica em respotas induzidas é comum e pode infuenciar a qualidade das defesas contra herbivoros que as formigas oferecem ás plantas que elas ocupam.