bluuebunny/crossref_metadata_2025_split huggingface dataset:
Factors Contributing to Variation in Seed Production among Remnant Populations of the Endangered Daisy Gerbera aurantiaca1
Authors: Johnson Steven D. , Collin Carine L. , Wissman H. Jörgen , Halvarsson Erika , Ågren Jon 
Published: March 2006

ABSTRACTThe species‐rich mist‐belt grasslands of southern Africa have been severely reduced in extent as a result of commercial afforestation, thus confining many endemic plants and animals to small populations in habitat fragments. We investigated the influence of various environmental factors on seed production and seedling recruitment in remnant populations of the endangered grassland herb Gerbera aurantiaca (Asteraceae). Experiments with color traps showed that Eriesthis beetles, which appear to be the primary pollinators of G. aurantiaca, were most abundant in the two largest y extant populations. Seeds are produced in a very small proportion (typically <10%) of the ca 80 female florets in a capitulum. The mean number of seeds produced in undamaged capitula was found to be significantly lower in small than in large populations. Pollen limitation was evident from a significant overall increase in seed set after supplementalpollination in three populations over two seasons. The proportion of capitula containing seed predators did not differ markedly among populations or years, but lepidopteran larvae, which destroy all of the seeds in a capitulum, weremost abundant in the two largest populations in 2003. The presence of juvenile plants varied markedly amongpopulations, but this could not be linked firmly to estimates of seed production. Clonal growth is likely to contribute to the persistence of small isolated populations of G. aurantiaca, even when seed production is severely compromised by pollen limitation and predation.
Sex in Space: A Synthesis
Authors: Ghazoul Jaboury , Shaanker R. Uma 
Published: March 2006

ABSTRACTThe five papers in this Special Section illustrate that pollination processes are often disrupted by changing plant distributions. They further demonstrate that plant pollination and seed production outcomes are highly complex due to multidimensional spatial effects and numerous interactive biological responses of both plants and pollinators at individual and population scales. Nevertheless, these studies also lend support to some emerging generalities that (through modeling) begin to provide a coherent framework by which further research, and ultimately management planning, could proceed.
Termite Mounds as Nutrient–Rich Food Patches for Elephants
Authors: Holdo Ricardo M. , McDowell Lee R. 
Published: March 2006

ABSTRACTThis study compared elephant use of woody vegetation on termite mounds with surrounding woodlands in western Zimbabwe. Twelve sites consisting of paired plots on termite mounds and in woodlands were selected. At each site, soil and vegetation samples (leaf and stem) were collected for chemical analysis. Both soil and plant samples were analyzed for calcium, magnesium, potassium, sodium, and phosphorus, and plant samples were also analyzed for crude protein concentration. Two indices of elephant feeding damage were computed: the median number of stems and branches removed per plant, and the mass of stems and branches removed by elephants per unit area. Termite mound soils had higher concentrations of all elements tested than soils from woodlands, and termite mounds differed from woodland plots in terms of plant species composition. Trees growing on termite mounds had higher concentrations of all nutrients except sodium and crude protein, and were subjected to more intense feeding by elephants than trees from the surrounding vegetation matrix. Termite mounds may play an important role in determining food availability and spatial feeding patterns by elephants and other herbivores.
Lack of Genetic Structuring among Tropical Brazilian Wood Stork Populations and Low Genetic Differentiation from North American Populations
Authors: Rocha Cristiano Dosualdo , Del Lama Silvia Nassif , Regitano Luciana Correia de Almeida 
Published: March 2006

ABSTRACTThe Wood Stork (Mycteria americana) is a wading bird inhabiting subtropical and tropical regions of the American continent. This species is considered endangered in the United States. We compared variability and genetic structuring of nine Brazilian Pantanal subpopulations with an North American population using eight allozyme loci data (MPI, ICD, NSP, EST‐D, LDH, PGM, 6PGD, and PEP‐A) and four microsatellite loci data (WS1, WS2, WS4, and WS6). Average expected heterozygosity of Pantanal population was similar (0.198 ± 0.065) to that expected for the North American population (0.231 ± 0.066). No significant genetic differentiation was found among Pantanal subpopulations (Fst= 0.012) and low differentiation was detected between Pantanal and North American populations (Fst= 0.023). Lack of differentiation among Pantanal subpopulations may have been due to high gene flow level among birds of neighbor breeding colonies and low natal philopatry. We propose that low differentiation between North and South American populations has arisen either because these populations occupied neighboring regions during late glaciation or because there is a continuous gene flow between them, via Central American or northern South American populations.RESUMOO Cabeça‐seca (Mycteria americana) é uma ave aquática habitante das regiões tropicais e subtropicais do continente americano. Essa espécie está ameaçada de extinção nos Estados Unidos. Nós comparamos a variabilidade e a estruturação genética de nove subpopulações brasileiras do Pantanal com as da população norte americana, baseando‐se em dados de oito locos alozímicos (MPI, ICD, NSP, EST‐D, LDH, PGM, 6PGD, e PEP‐A) e em dados de quatro locos de microssatélites (WS1, WS2, WS4, e WS6). A heterozigosidade média esperada para a população do Pantanal (0.198 ± 0.065) foi semelhante á esperada para a população norte americana (0.231 ± 0.066). Não foi encontrada diferenciação genética significativa entre as subpopulaçóes do Pantanal (Fst= 0.012) e baixa diferenciação genética foi detectada entre as populações do Pantanal e a norte americana (.Fst= 0.023). A não diferenciação entre subpopulações do Pantanal pode ser resultante de um alto nível do fluxo génico entre aves de colónias reprodutivas vizinhas e da baixa filopatria natal. Nós propomos que a baixa diferenciação entre as populações norte e sul americanas seja decorrente da ocupaçaTo de regiões vizinhas por essas populações durante a última glaciação ou devido á existéncia de fluxo contínue entre elas, via populações da América Central ou do norte da América do Sul.
Aquatic Insect Assemblages in Shrimp‐dominated Tropical Streams, Puerto Rico
Authors: Ramirez Alonso , Hernandez‐Cruz Luz Raquel 
Published: March 2006

ABSTRACTWe examined the effects of shrimp on insects in Puerto Rico by assessing insect assemblages in streams relative to varying shrimp densities and also by manipulating shrimp presence. Insect assemblages were typical of tropical island streams and insects were found in all stream habitats. Shrimp impacted insects directly via predation and competition and indirectly through removing particles from the water column. Variation in shrimp distribution is likely to be an important factor determining insect‐assemblage structure in tropical streams.RESUMENExaminamos los efectos de los camarones sobre los insectos en Puerto Rico, para ello estudiamos quebradas con densidades contrastantes de camarones y manipulamos su presencia. Los ensamblajes de insectos fueron tipicos de quebradas de islas tropicales y usaron todos los hábitats. Los camarones impactaron directamente a los insectos via depredacion y competencia e indirectamente al remover particulas del agua. Variacion en la distribución de camarones es un factor importante en determinar la estructura de los ensamblajes de insectos en las quebradas tropicales.
Placing an Omnivore in a Complex Food Web: Dietary Contributions to Adult Biomass of an Ant
Authors: Tillberg Chadwick V. , Breed Michael D. 
Published: March 2006

ABSTRACTWorkers of Paraponera clavata, a common Neotropical ant, collect both nectar and insect prey. Previous reports show that nectar accounts for up to 90 percent of the ants’ food loads, while calculations suggest that nectar contributes only 10 percent of colonies’ energy supply. We assessed the trophic source of carbon and nitrogen in adult workers using stable isotope analysis. Carbon in adult workers was largely derived from plant sources. Worker nitrogen isotopic ratios varied significantly among colonies and were enriched compared to prey. Prey nitrogen isotope ratios suggest considerable intercolonial variation in diet, with some colonies collecting prey from lower trophic levels than other colonies. The importance of nectar as a source of metabolic carbon in adult worker biomass, coupled with the high frequency of nectar collection, supports the conclusion that omnivory is a key to supporting this species’ biomass in Neotropical wet forests.
Beyond Paradise—Meeting the Challenges in Tropical Biology in the 21st Century
Authors: Bawa Kamaljit S. , Kress W. John , Nadkarni Nalini M. 
Published: March 2006

ABSTRACTTropical ecosystems support a diversity of species and ecological processes that are unparalleled anywhere else on Earth. Despite their tremendous social and scientific importance, tropical ecosystems are rapidly disappearing. To usher tropical ecosystems and the human communities dependent upon them through the environmental transformations of the 21st century, tropical biologists must provide critical knowledge in three areas: 1) the structure and function of tropical ecosystems; 2) the nature and magnitude of anthropogenic effects on tropical ecosystems; and 3) the socio‐economic drivers of these anthropogenic effects. To develop effective strategies for conservation, restoration, and sustainable management of tropical ecosystems, scientific perspectives must be integrated with social necessities. A new set of principles built on a framework for pursuing relevant tropical biological research will facilitate interdisciplinary approaches, integrate biological knowledge with the social sciences, and link science with policy. We propose four broad recommendations for immediate action in tropical biology and conservation that are fundamental to all biological and social disciplines in the tropics: 1) assemble and disseminate information on life's diversity in the tropics; 2) enhance tropical field stations and build a worldwide network to link them with tropical field biologists at their field sites; 3) bring the field of tropical biology to the tropics by strengthening institutions in tropical countries through novel partnerships between tropical and temperate zone institutions and scientists; and 4) create concrete mechanisms to increase interactions between tropical biologists, social scientists, and policy makers.
Physical Damage in Relation to Carbon Allocation Strategies of Tropical Forest Tree Saplings
Authors: Pauw Anton , Van Bael Sunshine A. , Peters Halton A. , Allison Steven D. , Camargo José L. C. , Cifuentes‐Jara Miguel , Conserva Aurlstela , Restom Teresa Garcia , Heartsill‐Scalley Tamara , Mangan Scott A. , Nunez‐lturri Gabriela , Rivera‐Ocasio Elsie , Rountree Mark , Vetter Susanne , de Castllho Carolina Volkmer 
Published: March 2006

ABSTRACTWe show that tropical forest tree saplings with greater belowground carbon allocation have more breakage scars along their stems. We suggest the existence of alternative carbon allocation strategies in relation to physical damage in the forest understorey. “Tolerators” allocate more belowground, have enhanced resprouting ability and slower aboveground growth, whereas “escapers” allocate less belowground, are not well prepared for recovering from damage, but grow fast enough to escape from the damage‐susceptible size class.RESUMENBrinzales de árboles tropicales que asignan mayor cantidad de carbono bajo el suelo muestran más cicatrices de fractura en sus tallos. Sugerimos la existencia de estrategias alternativas de asignación de carbono en respuesta a daño fisico en el sotobosque: los “tolerantes” asignan mayor cantidad de carbono bajo el suelo, tienen mayor capacidad para rebrotar y su crecimiento aéreo es lento; los “escapistas” asignan menor cantidad de carbono bajo el suelo y no están bien preparados para recuperarse después de ocurrido un daño, pero crecen lo suficientemente rápido para escapar de la clase diamétrica más susceptible a daños.
The Flexible Breeding System of Werauhia sintenisii, a Cloud Forest Bromeliad from Puerto Rico
Authors: Lasso Eloisa , Ackerman James D. 
Published: March 2006

ABSTRACTThe tropical mountain cloud forest bromeliads studied thus far have been reported as self compatible; however, whether or not autogamy and apomixis occur is not known. We characterized the breeding system of Werauchia sintenisii using a series of treatments to detect self‐compatibility, autogamy, and apomixes. The natural fruit set of this population was 97 percent. Pollen origin (self vs. cross) did not affect fruit and seed set. Werauhia sintenisii is autogamous but not apomictic. All pollinator‐excluded flowers produced fruits, but flowers that were emasculated and caged did not produce any fruit. Factors affecting the evolution of autogamy in this system are discussed.RESUMENLas bromelias de Bosques Montanos estudiadas hasta la fecha han sido reportadas como auto‐compatibles. Sin embargo, se desconoce si las mismas son autógamas o apomfcticas. Caracterizamos el sistema de apareamiento de Werauchia sintenisii por medio de una serie de tratamientos diseñados para detectar auto‐compatibilidad, autogamia, y apomixes. En la población estudiada 97 por ciento de las flores producen frutos. El origen del pollen (propio vs foráneo) no affectó el número de semillas y fructos producidos. Werauhia sintenisii es autogama pero no apomictica. Todas las flores que fueron excluidas a los polinizadores produjeron frutos, sin embargo aqudlas que fueron emasculadas y excluidas a los polinizadores no produjeron frutos. Se discuten los factores que han podido afectar la evolución de autogamia en este sistema.
Population Dynamics of Pterocereus gaumeri, a Rare and Endemic Columnar Cactus of Mexico
Authors: Méndez Martha , Durán Rafael , Olmsted Ingrid , Oyama Ken 
Published: March 2006

ABSTRACTWe 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 (X) 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.RESUMENSe presenta un estudio demográfico de Pterocereus gaumeri, un cactus raro, y endémico columnar de la Peninsula de Yucatán, México. Desde 1997 a 1999, se registró el crecimiento, la sobrevivencia y la fecundidad de individuos en dos poblaciones. Se construyeron marrices de proyección basadas en tamano 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 vegetative, por lo tan to 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) varia 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 categorias de tamanos menores. Nuestros resultados no indican que el tamano 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
Authors: Sheil Douglas , Salim Agus 
Published: March 2006

ABSTRACTSixteen 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
Authors: Hodgkison Robert , Balding Sharon T. , Zubaid Akbar , Kunz Thomas H. 
Published: March 2006

ABSTRACTThe 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 m2 mist‐net hours of sampling between February 1996 and September 1999. Three species of fruit bats (Balionycteris maculita, 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.
The Striped Squirrel (Tamiops swinhoei hainanus) as a Nectar Robber of Ginger (Alpinia kwangsiensisy)
Authors: Deng Xao‐Bao , Ren Pan‐Yu , Gao Jiang‐Yun , Li Qing‐Jun 
Published: March 2006

ABSTRACTNectar 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
Authors: Walsh Peter D. , Henschel Phillipp , Abernethy Kate A. , Tutin Caroline E. G. , Telfer Paul , Lahm Sally A. 
Published: March 2006

ABSTRACTHere, 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.RESUMENNous documentons l'invasion de l'Afrique Equatoriale par la fourmi électrique (Wasmannia auropunctata). L'exploitation forestière et les autres formes d'extraction des ressources naturelles ont catapultéWasmannia auropunctataá l'interieur du Gabon á un rythme 60 fois plus rapide que la progression non assistée que nous avons mesurée sur 19 ans á la Réserve de la Lopé. Nous présentons également des photographies suggérant que Wasmannia auropunctata a un impact négatif sur la faune de grands mammiféres exceptionnellement riche et intacte du pays.
HBV, HCV, and TTV detection by in situ polymerase chain reaction could reveal occult infection in hepatocellular carcinoma: comparison with blood markers
Authors: Comar M , Dal Molin G , D’Agaro P , Crocè S L , Tiribelli C , Campello C 
Published: March 2006

Objective:To report a retrospective analysis on the presence of hepatitis B virus (HBV), hepatitis C virus (HCV), and transfusion transmitted virus (TTV) sequences in formalin fixed, paraffin embedded liver biopsies from eight patients with hepatocellular carcinoma, in comparison with blood markers.Methods:A direct in situ polymerase chain reaction (PCR) technique was developed for the detection and localisation of genomic signals in the liver tissue. Conventional serological and molecular methods were used for blood evaluation.Results:In situ PCR showed the presence of one of the three viruses (four HCV, two HBV, and one TTV) in seven of the eight patients. In addition, a co-infection with HBV and HCV was detected in one patient. HCV and HBV sequences were located in the cytoplasm and the nucleus, respectively. When compared with blood markers, these findings were compatible with one occult HBV and two occult HCV infections.Conclusions:These findings provide further evidence for occult HBV and HCV infections in cancerous tissues from patients with hepatocellular carcinomas. In situ PCR could be an additional tool for evaluating the viral aetiology of hepatocellular carcinoma alongside conventional diagnostic procedures.