bluuebunny/crossref_metadata_2025_split huggingface dataset:
Environmental Effects on Components of Pollen Performance in Faramea occidentalis (L.) A. Rich. (Rubiaceae)1
Authors: Travers Steve E. 
Published: March 2006

ABSTRACTStudies focusing on gametophytic competition have focused on differences in pollen performance (e.g., pollen germination rate and pollen tube growth rate) among donors in order to examine genetic sources of variation in siring success among them. Donors that produce the fastest growing pollen tubes are expected to fertilize more ovules relative to donors with slow growing pollen tubes under conditions of gametophytic competition. However, the performance of pollen in the field is known to be influenced by environmental conditions in addition to the genotype of donor plants. This field study of Faramea occidentalis was conducted to: (1) determine the effect of environmental conditions during pollination on pollen performance; (2) measure differences among pollen donors in pollen performance; (3) determine if the pollen of different donors responds differently to a variety of environmental conditions surrounding pollinated flowers; and (4) measure differences among pollen recipients in pollen performance. Single‐donor crosses were made between four pollen donors and four pollen recipients under a variety of environmental conditions. Pollen performance was then quantified as the growth rate of the fastest pollen tube, the mean pollen tube growth rate, and by a pollen germination index. Pollination environment (the environment surrounding a pollinated flower) and recipient significantly affected all three measures of pollen performance. Pollen donors did not differ overall in pollen performance. However, there was significant among‐donor variation in two of the five pollination environment conditions. Future studies of variation in relative siring success may benefit by considering pollination environment in addition to donor and recipient identity.
Tropical Monodominance: A Preliminary Test of the Ectomycorrhizal Hypothesis1
Authors: Torti Sylvia D. , Coley Phyllis D. 
Published: March 2006

ABSTRACTThis study reports results from the first explicit test of the ectomycorrhizal hypothesis for tropical monodominance in the Ituri Forest of the Democratic Republic of Congo (formerly Zaire), where the canopy tree Gilbertiodendron dewevrei forms large, monospecific stands. To test the hypothesis that ectomycorrhizae are important to the success of dominant species, we surveyed the mycorrhizal status of dominant species, as well as other common, but not dominant, species in the forest. The survey reveals that two dominant species, Gilbertiodendron dewevrei and Julbernardia seretii, form ectomycorrhizae and vesicular‐arbuscular mycorrhizae, while Cynometra alexandri, another dominant, forms only vesicular‐arbuscular mycorrhizae. These results, along with those of other species in this and other forests, are discussed within the context of the ectomycorrhizal hypothesis for tropical mondominance. This study demonstrates that the relationship between EM and tropical monodominance is more complex than has been previously recognized.
Nitrogen Fixation in Soils and Canals of Rehabilitated Raised‐Fields of the Bolivian Altiplano1
Authors: Biesboer David D. , Binford Michael W. , Kolata Alan 
Published: March 2006

ABSTRACTRaised‐field agricultural systems were exploited extensively by pre‐Columbian Andean civilizations and now are used less extensively by contemporary Bolivian and Peruvian farmers as a method for farming the perennially wet soils of the intermontane pampas of the Andean high altiplano. The raised‐field agricultural systems are linear or semi‐linear raised planting platforms interspersed with shallow, parallel canals filled with water. The elevated planting platforms raise the critical rooting zone of crops such as potatoes, quinoa, or barley above perennially saturated soils. A hypothesized advantage of the raised‐field system is that agricultural production can be increased by exploiting the ability of bacteria and Azolla fililculoides to fix nitrogen in the canals adjacent to the planting platforms.To test this hypothesis, nitrogen fixation was estimated in situ in the water column of canals, in the soils of planting platforms, in the soils of a dry hillside field, and in the sediments and water column of marshes and totora beds. Nitrogen fixation was significantly greater in the canals of the raised‐field systems and in marshes compared to planting platforms and the hillside field. These data support the theory that pre‐Hispanic agricultural prosperity of the Andes, as well as other regions of Central and South America, was partially supported by extensive development of raised‐field agriculture and probable exploitation of nitrogen fixation.
Effects of Elevated CO2 and Defoliation on Compensatory Growth and Photosynthesis of Seedlings in a Tropical Tree, Copaifera aromatica1
Authors: Lovelock Catherine E. , Posada Juan , Winter Klaus 
Published: March 2006

ABSTRACTAfter defoliation by herbivores, some plants exhibit enhanced rates of photosynthesis and growth that enable them to compensate for lost tissue, thus maintaining their fitness relative to competing, undefoliated plants. Our aim was to determine whether compensatory photosynthesis and growth would be altered by increasing concentrations of atmospheric CO2. Defoliation of developing leaflets on seedlings of a tropical tree, Copaifera aromatica, caused increases in photosynthesis under ambient CO2, but not under elevated CO2. An enhancement in the development of buds in the leaf axils followed defoliation at ambient levels of CO2. In contrast, under elevated CO2, enhanced development of buds occurred in undefoliated plants with no further enhancement in bud development due to exposure to elevated CO2. Growth of leaf area after defoliation was increased, particularly under elevated CO2. Despite this increase, defoliated plants grown under elevated CO2 were further from compensating for tissue lost during defoliation after 51/2 weeks than those grown under ambient CO2 concentrations.
The Bromeliad Microcosm and the Assessment of Faunal Diversity in a Neotropical Forest1
Authors: Richardson Barbara A. 
Published: March 2006

ABSTRACTThe faunas of tank bromeliads were sampled over two years in three forest types at different elevations in the Luquillo Experimental Forest, Puerto Rico, and the diversity of their animal communities compared. Bromeliad plants behaved as islands in that, within forests, the species richness and abundance of their animal communities were significantly and positively correlated with increase in plant size. The amount of canopy debris they accumulated was similarly correlated with increase in plant size. Overall diversity was lowest in the dwarf forest, where plants were uniformly small. Animal communities were stable from year to year, and could be characterised for each forest type and for compartments within the plant. They showed a pattern of high dominance, which increased with elevation (Mc‐Naughton index 37, 54, and 73, respectively, for the tabonuco, palo Colorado, and dwarf forest). Alpha‐diversity for sites sampled in each year reflected net primary productivity (NPP) of the forest, declining with increasing elevation when animal abundance measures were used (jackknife estimates of Simpson's diversity index 6.54 & 11.04 [tabonuco], 3.53 & 6.22 [palo Colorado], and 2.75 & 2.17 [dwarf forest]). Species richness over the two years, however, was highest in the intermediate palo Colorado forest (187 species), compared to 146 and 88 in the tabonuco and dwarf forests, respectively. These figures were close to jackknife estimates of maximum species richness. The difference in species richness between tabonuco and palo Colorado forests was significant in one year only. In addition to NPP, other factors, such as litter quality and the structural complexity of the habitat in the palo Colorado forest, may have influenced species richness. The most abundant species in individual plants were also the most widely occurring, confirming known patterns of abundance and distribution in other functional groups. Diversity within bromeliad microcosms at different elevations supported known relationships between diversity, productivity, and habitat complexity along gradients and was not related to differences in the total bromeliad habitat available for colonization.
Sampling Effects on Food Availability Estimates: Phenological Method, Sample Size, and Species Composition1
Authors: Hemingway Claire A. , Overdorff Deborah J. 
Published: March 2006

ABSTRACTIt is currently recognized that the method used to collect phenology data can affect the resulting pattern. However, to date, the underlying influences have not been examined. To examine potential methodological biases, we investigated the effects of phenological method, sample size, and species composition on phenological patterns using data collected to estimate food availability for three primate species in Ranomafana National Park, Madagascar. Two phenological methods were compared: selected tree observations and systematic transect monitoring. By generating bootstrapped subsamples derived from the transect tree data set, we simulated two selected tree data sets and subsequently compared the observed and bootstrapped values. Although the observed values fell within the bootstrapped confidence inrervals, suggesting no significant effects of sampling protocol or sample size, additional lines of evidence suggest otherwise. Observed samples composed of different plant species, whether based on species attributes such as life‐form or categories such as food versus nonfood plants, consistently produced different phenological patterns. Wide confidence intervals of the bootstrapped samples indicate high individual variation in reproductive activity within the species sampled. Finally, we compared how well the selected tree and the transect methods represented food items used by all three primate species studied and found that transect methods sampled a wider diversity of food items, including rare foods, and a higher percentage of main primate food items than selected tree methods.
Variation in Nickel Content in the Nickel‐Hyperaccumulating Shrub Psychotria douarrei (Rubiaceae) from New Caledonia1
Authors: Boyd Robert S. , Jaffré Tanguy , Odom John W. 
Published: March 2006

ABSTRACTPlants that hyperaccumulate Ni contain > 1000 ppm (dry wt.) in their tissues. Variation of Ni content within hyperaccumulating plant species is poorly explored. Using the Ni‐hyperaccumulating shrub Psychotria douarrei, we documented variation of leaf Ni levels within individual shrubs, and variation with respect to plant size and leaf age. Plant size did not correlate significantly with leaf Ni content, and leaf Ni content did not correlate significantly with soil Ni content. Older leaves contained twice as much Ni as younger leaves. Older leaves also contained greater concentrations of Ca, Fe, and Cr but less K, P, and Cu. Five elements (Zn, Pb, Co, Mn, Mg) showed no significant variation due to leaf age. We also examined the effect of leaf age on epiphyll cover, finding increased epiphyll cover on the upper surface of older leaves. The dominant leafy liverwort epiphyll had a relatively high Ni content (400 ppm), suggesting that epiphylls of Ni hyperaccumulators obtain some Ni from host leaves. Individual shrubs differed in mean leaf Ni content almost two‐fold (14,900‐27,700 ppm). Variation among branches within individuals also ranged widely; however, this intraplant variability was not strongly correlated with the mean leaf Ni content of an individual shrub. We concluded that Ni contents in leaves of P. douarrei vary considerably due to leaf age, among individual shrubs, and among branches within a shrub.
Dispersal of Amazonian Trees: Hydrochory in Swartzia polyphylla1
Authors: Williamson G. Bruce , Costa Flávia , Vera Carolina V. Minte 
Published: March 2006

ABSTRACTHydrochory was investigated in the seeds of the Amazonian floodplain tree, Swartzia polyphylla, in which pods open on the tree to release one large seed. Seeds collected from beach drift along the Rio Negro showed a high percentage of floaters (82%). Yet most seeds sank following collection from: adult trees (89%), unflooded ground under adults (96%), and flooded ground under adults (86%). The specific gravity of the seeds was near that of water, 1.04 ± 0.03 for sinkers and 0.98 ± 0.02 for floaters. The ability to float was correlated directly with the volume of the air pocket between the two cotyledons, which varied from 5.6 to 20.5 percent of the total seed volume. In a long‐term floatation test lasting 81 days, 45 percent of the seeds never floated, 33 percent always floated, and 22 percent first sank for one week and then floated for at least one month. Seeds that never floated eventually rotted, but not until days 63‐73. Seeds that were floating at day 81, regardless of how long they had been floating, were placed on moistened filter paper for 18 days during which time 36 percent germinated, 45 percent rotted, and 19 percent did neither but remained viable. These results suggest that S. polyphylla achieves dimorphism in flotation of its seeds, some sinking and some floating, by producing seeds of continuous variation in specific gravity around a mean close to 1.00. Seeds that float can be dispersed long distances along river margins, while those that sink may be moved only marginally from the parent tree.
Seed Dispersal by Bats and Birds in Forest and Disturbed Habitats of Chiapas, Mexico1
Authors: Medellin Rodrigo A. , Gaona Osiris 
Published: March 2006

ABSTRACTWe examined seed dispersal by bats and birds in four habitats of the Selva Lacandona tropical rain forest region, Chiapas, Mexico. The four habitats represented a disturbance gradient: active cornfield, ten‐year‐old abandoned cornfield, cacao plantation, and forest. Using seed traps examined before sunrise (0400 h) and before sunset (1800 h), we compared volant vertebrate seed dispersal, assuming that seeds found at the end of the night were dispersed by bats and those found at the end of the day were dispersed by birds. We did not find seeds from other frugivores such as monkeys or opossums. In all habitats bats dispersed more seeds than birds. In most months bats also dispersed more seeds than birds, except in December when no seeds were found in the traps. Bats also consistently dispersed more species of seeds than birds, although a x2 comparison showed differences not to be significant. Fifty percent of the species represented in the dispersed seeds in all habitats were pioneer species. Cecropia seeds represented a high percentage (up to 87% of those dispersed by bats and up to 83% by birds) of dispersed seeds that fell in our traps. The influence of bats and birds on secondary successional processes is likely to be fundamental for the establishment of vegetation. Since bats dispersed more seeds than birds (primarily to disturbed areas and consisting primarily of pioneer species), they are likely to play an important role in successional and restoration processes among habitats as structurally and vegetationally different as cornfields, old fields, cacao plantations, and forest.
Feeding Ecology of the Giant Otter, Pteronura brasiliensis1
Authors: Rosas Fernando C. W. , Zuanon Jansen A. S. , Carter Sarah K. 
Published: March 2006

ABSTRACTThe food habits of the giant otter, Pteronura brasiliensis, were determined by analyzing fecal samples collected year–round from communal latrines at Xixtiaú Creek (00°48'S, 61°33'W), Jauaperi River (central Brazilian Amazon) between 1993 and 1994. Communal latrines were also sampled during the low water season at Aquidauana River (19°32'S, 56°40'W), Pantanal of Mato Grosso do Sul (central Brazil). Fragments of vertebrae, mandibles, teeth, scales, and fin spines provided an estimate of the diet composition. Remains of fish were present in all of the samples. The main fish groups found at Xixuaú Creek were Perciformes, represented specifically by Cichlidae (97.3% of all samples), Characiformes (86.5%) and Siluriformes (5.4%). The Characiformes were represented mainly by E, rythrinidae (Hoplias sp. 90.6%), followed by Serrasalmidae (28%). The Anostomidae occurred with a frequency of 18.7 percent, while Characinae, Bryconinae, and Cynodontidae were only observed in 3.1 percent of the Characiformes records. At Aquidauana River, the Characiformes were the most frequent fish group, represented in 100 percent of all samples, followed by Siluriformes (66.6%) and Perciformes (33.3%). The fish from the main groups identified in the diet of the giant otters prefer riverbanks, lakes, and flooded forests. The feeding habits of Pteronura brasiliensis are probably influenced by the vulnerability and abundance of the prey consumed by this carnivore.
Early Plant Succession in Abandoned Pastures in Ecuador1
Authors: Zahawi R. A. , Augspurger C. K. 
Published: March 2006

ABSTRACTWe compared early plant succession in four abandoned pastures of differing age since abandonment and a nearby secondary forest site in northwestern Ecuador. Two “Open” pastures had no tree canopy covering, and two “Guava” pastures had a well‐developed canopy cover of Psidium guajava. No site had been seeded with pasture grasses. All pastures were compared in a chronological sequence; two were monitored for 18 months. Species richness was consistently higher in Guava sites than in Open sites and it continued to increase over time, whereas it remained static in Open sites. Species richness was highest in secondary forest. Recruitment of tree saplings in Guava sites was lower than in secondary forest; however, it was nearly absent in Open sites. The seed bank contained predominantly herbaceous species at all sites, and was highly dissimilar to aboveground vegetation. Dominance‐diversity curves for Guava sites showed a more equitable distribution of species that increased over time. In contrast, dominance‐diversity curves for Open sites were static and indicated dominance by a few aggressive species. Soil characteristics among sites were variable; however, a principal components analysis on soils isolated the older Open site from all others. The older Open site had the lowest species richness and was dominated by Baccharis trinervis, an aggressive shrub species. The site appears to be in a state of arrested succession and some form of restorative intervention may be necessary to initiate succession toward a forested condition. Succession in Guava sites appears headed toward secondary forest, whereas it does not in Open sites.
Single‐Seeded Fruits and Seedling Establishment in Dalbergia miscolobium Benth. (Papilionaceae)1
Authors: Sassaki Regina Miyuki , Felippe G.M. 
Published: March 2006

ABSTRACT Dalbergia miscolobium (Papilionaceae) is a tree of the Brazilian cerrado that produces ovaries with two ovules. Only one ovule usually matures, but when two mature, they are smaller than seeds of single‐seeded pods. Germination percentage was lower in small seeds than in medium or large seeds. In general, small seeds gave rise to smaller seedlings (dry mass) than did medium and large seeds. The root/shoot ratio, however, was very similar for the first six months, indicating that this ratio is consistent across seedling sizes. There was no correlation between seed size and relative growth rate. Single‐seeded fruit production in D. miscolobium resulted in greater seed reserves and increased fruit dispersal distance; single‐seeded fruits were lighter than double‐seeded ones. Together, these two features should increase the probability of successful seedling establishment of seeds from single‐seeded versus double‐seeded fruits.
Pollination Ecology and Effect of Nectar Removal in Macleania bullata (Ericaceae)1
Authors: Navarro Luis 
Published: March 2006

ABSTRACTThe floral syndrome of Macleania bullataYeo (Ericaceae) reflects its adaptation to hummingbird pollination. Its flowers, however, are subject to high levels of nectar robbing. I examined the floral visitor assemblage of M. bullata in a tropical montane wet forest in southwestern Colombia, focusing on the behavior of the visitors. I also tested for the presence of nocturnal pollination and the effects of nectar removal on new nectar production. The principal floral visitors were the nectar robbing hummingbirds Ocreatus underwoodii (19.1% of visits) and Chlorostilbon mellisugus (18.9%). Only two species of long–billed hummingbirds visited the flowers of M. bullata as “legitimate” pollinators: Coeligena torquata (14.7% of visits) and Doryfera ludoviciae (14.3%). The remaining visits constituted nectar robbing by bees, butterflies, and other species of hummingbirds. Nocturnal pollination took place, although fruit set levels were 2.4 times higher when only diurnal pollination was allowed as opposed to exclusively nocturnal pollination. Nectar robbers removed floral nectar without pollinating the flower. Treatments of experimental nectar removal were carried out to examine if flowers synthesize more nectar after nectar removal. Nectar removal increased the total volume of nectar produced by each flower without affecting sugar concentration. Thus, nectar robbing can impose a high cost to the plants by forcing them to replace lost nectar.
Behavioral and Physiological Differences between Two Parapatric Heliconius Species1
Authors: Davison Angus , McMillan W. Owen , Griffin Ashleigh S. , Jiggins Chris D. , Mallet James L. B. 
Published: March 2006

ABSTRACTThe behavior and physiology of two parapatric sibling species,i Heliconius erato cyrbiaGodt. andH. himeraHew., were investigated to assess if environmental adaptation enabled stable morphological, genetic, and ecological differences to exist in the face of hybridization. Morning and evening activity, egg production, and larval development time ofH. himeraandH. eratoin insectaries were recorded; individuals were collected in allopatry and in sympatry from a hybrid zone in which the species overlapped. Studies were performed at ambient conditions within the natural range ofH. himera. H. himerawas considerably more active thanH, eratoflying earlier in the morning and later in the evening, even when both species were collected in sympatry. Similarly,H. himeralaid more eggs, and the hatched larvae developed more rapidly. The results suggest that physiological constraints are an important selective force that may have been important in speciation and counteracts hybridization in the maintenance of theH. himeral H. eratocontact zone. Ecological selection, arising from adaptation to low temperatures, may help explain the competitive exclusion ofH. eratobyH. himerain the drier, cooler montane habitat favored by the latter species.
Diversity and Abundance of Litter Frogs in a Montane Forest of Southeastern Brazil: Seasonal and Altitudinal Changes1
Authors: Giaretta A. A. , Facure K. G. , Sawaya R. J. , Meyer J. H. De M. , Chemin N. 
Published: March 2006

ABSTRACTWe sampled litter frogs in an 1800‐ha mid‐elevation seasonal forest in southeastern Brazil. One hundred 8 * 8‐m plots were sampled during the dry/cold season and wet/warm season (unburned areas); we also examined the effects of fire in recently burned areas. A total of 267 frogs (305 g), belonging to 16 species (4 families) were caught. A single species comprised 78.5 percent of the individuals in the dry/cold season and 54.3 percent in the wet/warm season. The density of individuals did not change significantly with season, biomass did. Density and biomass of frogs were positively correlated with altitude. A Mantel test indicated that biological data (species and their abundance) were significantly associated with environmental parameters. The burned areas showed low values in richness, density and biomass of frogs. Harsh seasonal climate and a history of human disturbance may produce the low observed diversity values. The greater densities of frogs in sites of higher elevation may primarily result from mist‐generated humidity, which diminishes the harshness of the dry/cold season in relation to lower sites.