bluuebunny/crossref_metadata_2025 huggingface dataset:
A Statistical Test of the Hypothesis that Polyclonal Intestinal Tumors Arise by Random Collision of Initiated Clones
Authors: Newton Michael A. , Clipson Linda , Thliveris Andrew T. , Halberg Richard B.
Published: March 2006

SummaryThe random collision hypothesis is a mathematical idealization of intestinal tumor formation that can account for the polyclonal origin of tumors without requiring a mechanistic description of clonal interaction. Using data from recent polyclonality studies in mice, we develop a statistical procedure to test the random collision hypothesis. Elements from stochastic geometry and approximations due toArmitage(1949,Biometrika36,257–266) support a statistical model of tumor count data. Bayesian analysis yields the posterior distribution of the number of heterotypic tumors, from whichp‐values are computed to test random collision.
Bayesian Estimation of Species Richness from Quadrat Sampling Data in the Presence of Prior Information
Authors: Dupuis Jérôme A. , Joachim Jean
Published: March 2006

Summary We consider the problem of estimating the number of species of an animal community. It is assumed that it is possible to draw up a list of species liable to be present in this community. Data are collected from quadrat sampling. Models considered in this article separate the assumptions related to the experimental protocol and those related to the spatial distribution of species in the quadrats. Our parameterization enables us to incorporate prior information on the presence, detectability, and spatial density of species. Moreover, we elaborate procedures to build the prior distributions on these parameters from information furnished by external data. A simulation study is carried out to examine the influence of different priors on the performances of our estimator. We illustrate our approach by estimating the number of nesting bird species in a forest.
Microstructural Characterization and Phase Development at the Interface Between Aluminum Nitride and Titanium After Annealing at 1300°–1500°C
Authors: Chiu Chia‐Hsiang , Lin Chien‐Cheng
Published: March 2006

Diffusion couples of aluminum nitride (AlN) and Ti were annealed under an argon atmosphere at temperatures ranging from 1300° to 1500°C for 0.5–36 h. The morphologies, crystal structures, and chemical compositions of the reaction zones at AlN/Ti interfaces were characterized using analytical scanning electron microscopy and analytical transmission electron microscopy. An interfacial reaction zone, consisting of TiN, τ2‐Ti2AlN, τ1‐Ti3AlN, α2‐Ti3Al, and a two‐phase (α2‐Ti3Al+α‐Ti) region in sequence, was observed in between AlN and Ti after annealing at 1300°C. The α2‐Ti3Al region revealed equiaxed and elongated morphologies with

and
. In the two‐phase (α2‐Ti3Al+α‐Ti) region, α2‐Ti3Al and α‐Ti were found to satisfy the following orientation relationship:and. The γ‐TiAl and a lamellar two‐phase (γ‐TiAl+α2‐Ti3Al) structure, instead of τ1‐Ti3AlN, were found in between τ2‐Ti2AlN and α2‐Ti3Al after annealing at 1400°C. The orientation relationship of γ‐TiAl and α2‐Ti3Al in the lamellar structure was identified to be as follows:and. Compared with the reaction zone after annealing at 1400°C, the γ‐TiAl was not found at the interface after annealing at 1500°C. The microstructural development resulting from isothermal diffusion at 1300°C and subsequent cooling at the interface are explained with the aid of the Ti–Al–N ternary phase diagram and a modified Ti–Al binary phase diagram.
Growth of ZnO Films with Controlled Morphology by Aqueous Solution Method
Authors: Liu Xiaoxin , Jin Zhengguo , Bu Shaojing , Zhao Juan , Liu Zhifeng
Published: March 2006

A novel method based on utilizing varied ionic strength and specific adsorption was developed to prepare c‐oriented zinc oxide (ZnO) films with controlled morphology in aqueous solution. Structure and morphology of the films were investigated by using X‐ray diffraction, scanning electron microscopy, field emission scanning electron microscopy, and high‐resolution transmission electron microscopy methods. A layer‐by‐layer growth manner of ZnO rod crystals was observed. The diameter of the ZnO rods can be controlled through the incorporation of the cost‐effective strong electrolyte NaCl. The reason for the variation of ZnO‐film morphology is that the enhanced ionic strength because of the addition of NaCl promotes not only the related reactants' concentration but also the specific adsorption of organic groups. Furthermore, acetyleacetone used as an assistant can play an important role in specific adsorption, leading to the formation of pyramid crystals through mild secondary growth.
Resource utilization in a Canadian national study of people with schizophrenia and related psychotic disorders
Authors: Kopala L. , Smith G. , Malla A. , Williams R. , Love L. , Talling D. , Balshaw R.
Published: March 2006

Objective:  To determine how the use of the newer, so called atypical antipsychotic medications, effects the pharmacoeconomic treatment burden of schizophrenia and related conditions and to provide a clear comparison of the costs and risks associated with these atypical drugs.

Method:  In this 2‐year, open‐label, prospective study, resource utilization (RU) data were collected on 160 patients with these conditions. A comparison between risks and costs was performed by combining the generalized CNOMSS data on both economic factors and risk assessments.

Results:  The main findings of the study were that the total adjusted 1‐ and 2‐year costs were lowest for quetiapine. Drug acquisition costs were lowest for risperidone for both the 1‐ and 2‐year cohorts. Clozapine use was predictably associated with the highest overall and medication costs at both 1 and 2 years.

Conclusion:  Treatment with risperidone or quetiapine was associated with the lowest overall costs when compared with olanzapine or clozapine.
Opportunism in Inter-firm Exchanges in Emerging Markets
Authors: Luo Yadong
Published: March 2006

This article develops a theoretical model of opportunism in inter-organizational exchanges in emerging markets. I decompose opportunism into ‘strong form’ (contractual norm violation) and ‘weak form’ (relational norm violation), and suggest that strong form tends to be more observable, measurable and remediable than weak form and its adverse effect on cooperation tends to be stronger but less enduring than weak form. I address how external uncertainty, a multidimensional concept that includes market volatility, legal unprotectability, information unverifiability and regulatory variability, along with internal uncertainty that reflects dyadic tensions such as goal disparity, resource misfit, cultural dissimilarity and bargaining asymmetry, together affect exchange members' opportunism. This is followed by further discussions on conditions under which firms will opt for strong form or weak form opportunism in the face of such external and internal uncertainties. I suggest that suppressing forces against opportunism necessitates not only economic ordering, such as contractual mechanisms and structural mechanisms, but also social ordering, such as relational mechanisms and justice mechanisms. I expect that economic ordering is more effective in resisting strong form opportunism while social ordering is more forceful in curtailing weak form opportunism.
Alcohol linked to enhanced angiogenesis in rat model of choroidal neovascularization
Authors: Bora Puran S. , Kaliappan Sankaranarayanan , Xu Qin , Kumar Shalesh , Wang Yali , Kaplan Henry J. , Bora Nalini S.
Published: March 2006

One of the pathologic complications of exudative (i.e. wet‐type) age‐related macular degeneration (AMD) is choroidal neovascularization (CNV). The aim of this study was to investigate whether chronic and heavy alcohol consumption influenced the development of CNV in a rat model. The oxidative metabolism of alcohol is minimal or absent in the eye, so that ethanol is metabolized via a nonoxidative pathway to form fatty acid ethyl esters (FAEE). Fatty acid ethyl ester synthase (FAEES) was purified from the choroid of Brown Norway (BN) rats. The purified protein was 60 kDa in size and the antibody raised against this protein showed a single band on western blot. BN rats on a regular diet were fed alcohol for 10 weeks. Control rats were fed water with a regular diet and pair‐fed control rats were fed regular diet, water and glucose. We found that FAEES activity was increased 4.0‐fold in the choroid of alcohol‐treated rats compared with controls. The amount of ethyl esters produced in the choroid of 10 week alcohol‐fed rats was 7.4‐fold more than rats fed alcohol for 1 week. The increased accumulation of ethyl esters was associated with a 3.0‐fold increased expression of cyclin E and cyclin E/CDK2; however, the level of the cyclin kinase inhibitor, p27Kip, did not change. The increased accumulation of ethyl esters was also associated with 3.0‐fold decreased expression of APN in the choroid. We also found that the size of CNV increased by 28% in alcohol‐fed rats. Thus, our study showed that chronic, heavy alcohol intake was associated with both an increased accumulation of ethyl esters in the choroid and an exacerbation of the CNV induced by laser treatment. These results may provide insight into the link between heavy alcohol consumption and exudative AMD.
Mycobacterium tuberculosis H37Rv ESAT‐6–CFP‐10 complex formation confers thermodynamic and biochemical stability
Authors: Meher Akshaya K. , Bal Naresh Chandra , Chary Kandala V. R. , Arora Ashish
Published: March 2006

The 6‐kDa early secretory antigenic target (ESAT‐6) and culture filtrate protein‐10 (CFP‐10), expressed from the region of deletion‐1 (RD1) of Mycobacterium tuberculosis H37Rv, are known to play a key role in virulence. In this study, we explored the thermodynamic and biochemical changes associated with the formation of the 1 : 1 heterodimeric complex between ESAT‐6 and CFP‐10. Using isothermal titration calorimetry (ITC), we precisely determined the association constant and free energy change for formation of the complex to be 2 × 107 m−1 and −9.95 kcal·mol−1, respectively. Strikingly, the thermal unfolding of the ESAT‐6–CFP‐10 heterodimeric complex was completely reversible, with a Tm of 53.4 °C and ΔH of 69 kcal·mol−1. Mixing of ESAT‐6 and CFP‐10 at any temperature below the Tm of the complex led to induction of helical conformation, suggesting molecular recognition between specific segments of unfolded ESAT‐6 and CFP‐10. Enhanced biochemical stability of the complex was indicated by protection of ESAT‐6 and an N‐terminal fragment of CFP‐10 from proteolysis with trypsin. However, the flexible C‐terminal of CFP‐10 in the complex, which has been shown to be responsible for binding to macrophages and monocytes, was cleaved by trypsin. In the presence of phospholipid membranes, ESAT‐6, but not CFP‐10 and the complex, showed an increase in α‐helical content and enhanced thermal stability. Overall, complex formation resulted in structural changes, enhanced thermodynamic and biochemical stability, and loss of binding to phospholipid membranes. These features of complex formation probably determine the physiological role of ESAT‐6, CFP‐10 and/or the complex in vivo. The ITC and thermal unfolding approach described in this study can readily be applied to characterization of the 11 other pairs of ESAT‐6 family proteins and for screening ESAT‐6 and CFP‐10 mutants.
Regional and segmental flexibility of antibodies in interaction with antigens of different size
Authors: Oda Masayuki , Uchiyama Susumu , Robinson Carol V. , Fukui Kiichi , Kobayashi Yuji , Azuma Takachika
Published: March 2006

The interaction of antibodies (Abs) with protein antigens (Ags) of different size, such as hen egg white lysozyme, ovalbumin, and bovine serum albumin, was examined using analytical ultracentrifugation, electrospray ionization time‐of‐flight mass spectrometry, and surface plasmon resonance in order to estimate regional and segmental Ab flexibility. When both Abs and Ags were free in solution, sedimentation equilibrium and surface plasmon resonance analyses showed the formation of an Ag2Ab1 complexes regardless of Ag size, suggesting that the Fab arms were able to move to avoid interference between Ags bound to Ab combining sites. The Ag2Ab1 complex, as well as the Ag1Ab1 complex, was observed by MS. However, when Abs were immobilized on the surface of a sensor chip through the Fc region, the stoichiometry of the Ag–Ab complex was dependent on the Ag size; Ag2Ab1 forming with hen egg white lysozyme and Ag1Ab1 with ovalbumin and bovine serum albumin. These results indicated that immobilization of the Fc region reduces the dynamic range of the Fab arms and results in interference from the first Ag bound to either combining site, which in turn prevents the binding of the second Ag to the other combining site. Our results allow us to propose that the Fab arms of B‐cell receptors whose Fc regions are immobilized on cell surface have a reduced dynamic range.
Inorganic phosphate regulates the binding of cofilin to actin filaments
Authors: Muhlrad Andras , Pavlov Dmitry , Peyser Y. Michael , Reisler Emil
Published: March 2006

Inorganic phosphate (Pi) and cofilin/actin depolymerizing factor proteins have opposite effects on actin filament structure and dynamics. Pi stabilizes the subdomain 2 in F‐actin and decreases the critical concentration for actin polymerization. Conversely, cofilin enhances disorder in subdomain 2, increases the critical concentration, and accelerates actin treadmilling. Here, we report that Pi inhibits the rate, but not the extent of cofilin binding to actin filaments. This inhibition is also significant at physiological concentrations of Pi, and more pronounced at low pH. Cofilin prevents conformational changes in F‐actin induced by Pi, even at high Pi concentrations, probably because allosteric changes in the nucleotide cleft decrease the affinity of Pi to F‐actin. Cofilin induced allosteric changes in the nucleotide cleft of F‐actin are also indicated by an increase in fluorescence emission and a decrease in the accessibility of etheno‐ADP to collisional quenchers. These changes transform the nucleotide cleft of F‐actin to G‐actin‐like. Pi regulation of cofilin binding and the cofilin regulation of Pi binding to F‐actin can be important aspects of actin based cell motility.
DNA strand exchange activity of rice recombinase OsDmc1 monitored by fluorescence resonance energy transfer and the role of ATP hydrolysis
Authors: Rajanikant Chittela , Kumbhakar Manoj , Pal Haridas , Rao Basuthkar J. , Sainis Jayashree K.
Published: March 2006

Rad51 and disrupted meiotic cDNA1 (Dmc1) are the two eukaryotic DNA recombinases that participate in homology search and strand exchange reactions during homologous recombination mediated DNA repair. Rad51 expresses in both mitotic and meiotic tissues whereas Dmc1 is confined to meiosis. DNA binding and pairing activities of Oryza sativa disrupted meiotic cDNA1 (OsDmc1) from rice have been reported earlier. In the present study, DNA renaturation and strand exchange activities of OsDmc1 have been studied, in real time and without the steps of deproteinization, using fluorescence resonance energy transfer (FRET). The extent as well as the rate of renaturation is the highest in conditions that contain ATP, but significantly less when ATP is replaced by slowly hydrolysable analogues of ATP, namely adenosine 5′‐(β,γ‐imido) triphosphate (AMP‐PNP) or adenosine 5′‐O‐(3‐thio triphosphate) (ATP‐γ‐S), where the former was substantially poorer than the latter in facilitating the renaturation function. FRET assay results also revealed OsDmc1 protein concentration dependent strand exchange function, where the activity was the fastest in the presence of ATP, whereas in the absence of a nucleotide cofactor it was several fold (≈ 15‐fold) slower. Interestingly, strand exchange, in reactions where ATP was replaced with AMP‐PNP or ATP‐γ‐S, was somewhat slower than that of even minus nucleotide cofactor control. Notwithstanding the slow rates, the reactions with no nucleotide cofactor or with ATP‐analogues did reach the same steady state level as seen in ATP reaction. FRET changes were unaffected by the steps of deproteinization following OsDmc1 reaction, suggesting that the assay results reflected stable events involving exchanges of homologous DNA strands. All these results, put together, suggest that OsDmc1 catalyses homologous renaturation as well as strand exchange events where ATP hydrolysis seems to critically decide the rates of the reaction system. These studies open up new facets of a plant recombinase function in relation to the role of ATP hydrolysis.
Distribution and Dispersion Patterns of Individuals in Nine Species of Lepanfhes (Orchidaceae)1
Authors: Tremblay Raymond L.
Published: March 2006

Dispersion of individuals and patches of individuals are presented for nine species of epiphytic and lithophytic orchids in the genus Lepanthes. Patches is defined as the group of individuals present on a phorophyte. Mean number and standard error of reproductive individuals per patch range from 11.6 ± 5.1 in Lepanthes eltoroensis, to 45.5 ± 5.2 in L. rupestris. Most patches contain few reproductive individuals and usually a few patches had most of the adults. The distribution of patch sizes is skewed and most patches carry fewer individuals than the mean. Therefore means may not be an appropriate measure of central tendency as shown by mean crowding and mean patchiness indices. Mean distances between patches range from 4.8 m in L. rupestris to 95.5 m in L. dodiana. Most species have a mean nearest neighbor patch further than 50 m. A regular pattern of dispersion is often observed at distances of 5 and 10 m while at larger distances patches are more frequently aggregated. Large distances between patches and few individuals per patch suggest that small effective population sizes may be common in these orchids if gene flow is restricted.

La distribución espacial de los individuos y las poblaciones vegetales son componentes importantes que influyen en el proceso de apareamiento. La dispersión de los individuos y grupos de estos individuos (o parchos) se presentan para nueve especies de orquídeas epifíticas del género Lepanthes. El número promedio y error estandard de los individuos reproductivos por parcho fluctúa desde 11.6 ± 5.1 en Lepanthes eltoroensis hasta 45.5 ± 5.2 en L. rupestris. La mayoría de los parchos tenían pocos individuos reproductivos y usualmente algunos de los parchos tenían la mayoría de los individuos; la distribución de frecuencias del tamaño de los parchos es desviada y la mayoría de los parchos tenía menos adultos que el promedio. Parece que el promedio no es una medida mas apropriada de la tendencia central como suguiera los indices de “mean crowding and mean patchiness”. Las distancias promedio entre los forofitos fluctúa desde 4.8 m en L. rupestris hasta 95.5 m en L. dodiana; la mayoría de las especies tenían un forofito vecino más cercano con un promedio mayor de 50 m. El patrón de dispersión observado a distancias de 5 y 10 metros es mayormente regular mientras que a distancias mayores los parchos se encuentran más agregados. Distancias grandes entre los forofitos y pocos individuos por forofito sugieren que tamaños de población efectiva pequeños pueden ser comunes en estas orquídeas.
Floral Lipid Chemistry of Byrsonima crassifolia (Malpigheaceae) and a Use of Floral Lipids by Centris Bees (Hymenoptera: Apidae)
Authors: Wnson S. B. , Williams H. J. , Frankie G. W. , Shrum G.
Published: March 2006

Byrsonima rrassifolia (L.), a Neotropical malpighiaceous tree or treelet, has flowers that produce abundant lipids instead of nectar. Several species of Centris bees collect this oil. The floral oil shows variation between trees and can be separated into two types. One type is most common (11 of 14 samples) and consists of mono‐ and di‐glycerides, some free fatty acids, a small amount of tri‐glycerides and a trace of carbohydrate. The composition of the glycerides is predominantly (53–63%) esters of unsaturated 18C–22C fatty acids with the rest made up of 14C–18C saturated fatty acids. The second type of floral oil is similar to type one except that the samples contain large amounts of an unknown lipid more polar than the standards.

Oil collected from the scopae of two representative Centris species, C. adanae and C. flavofasciata, was the same as the type one oil collected from B. rrassifolia floral elaiophores. The liquid provisions from the cells of several groundnesting Centris species was also found to be identical to B. crassifolia type one floral elaiophore oil with the exception of several minor ninhydrin positive compounds which may have been derived from the pollen which makes up part of the larval food provisions.
Influence ofAzteca alfariAnts on the Exploitation ofCecropiaTrees by a Leaf‐Cutting Ant
Authors: Vasconcelos Heraldo L. , Casimiro Antonio B.
Published: March 2006

The foraging activity of the leaf‐cutting antAtta laevigatain an early successional area near Manaus, Brazil, was monitored over a period of 18 mo. FourCecropiaspecies were growing in that area and all were associated with the antAzteca alfari. Unoccupied trees (those in which there was no ant response to mechanical disturbance of the stem) were attacked by leaf‐cutting ants more often than were trees occupied byA. alfaricolonies.

Cecropia uleiwas the most frequently attacked species. However, leaves ofC. uleiwere the least preferred ones during assays in which detached leaves of the fourCecropiaspecies were placed alongside the foraging trails of leaf‐cutting ant colonies.C. uleihad the largest number of unoccupied trees compared to the other species. In addition,A. alfaricolonies associated withC. uleiwere smaller than those associated withC. distacbya. These data suggest thatA. alfariwas influencing the selection ofCecropiaspecies byA. laevigata, which harvested more from species that were less defended by the ants (with a higher proportion of unoccupied trees or trees hosting smaller ant colonies), although these were less preferred.

A atividade forrageira da saúvaAtta laevigatafoi monitorada por 18 meses em uma área próxima a Manaus. Quatro espécies de embalúba (Cecropia), associadas a formigaAzteca alfari, ocorriam nesta área. Embaúbas não ocupadas porA. alfari(aquelas em que nenhuma formiga emergiu do tronco da planta quando este foi sacudido) foram mais atacadas pelas saúvas do que as embaúbas ocupadas.

Cecropia uleifoi a espécie mais atacada pelas saúvas. Entretanto as folhas deC. uleiforam menos preferidas pelas saúvas em ensaios de campo nos quais folhas das quatro espécies foram simultaneamente colocadas ao longo das trilhas das saúvas. Um número maior deC. uleinão tinha colônias deA. alfari, comparativamente às outras espécies. Além disto, as colônias deA. alfariemC. uleieram menores que aquelas de ao menos uma outra espécie,C. distuchya. Estes dados sugerem queA. alfariafetou a escolha das espécies deCecropiaporA. laevigata, a qua1 atacou mais a espéie que era menos defendida porA. alfari(que tinha menos plantas colonizadas e que abrigava colônias menores) mesmo que esta tinha folhas pouco palatáveis.
Ants of Forest and Fallow Plots in Nigeria1
Authors: Ewuim Sylvanus C. , Badejd M. Adetola , Ajayi Olawale O.
Published: March 2006

Pitfall traps were used to monitor the activity of ants in a forest floor and a one‐year‐old fallow plot in Ile‐Ife, Nigeria, at monthly intervals between November 1980 and October 1981. Similar studies were carried out between October 1987 and June 1988. These studies also included manual collection of ants from the floor of the experimental plots Of all the 10 species of ants recorded, Pbeihk crassinoda was the most abundant in the forest and fallow plots both in 1980–81 and 1987–88. P. crassinoda accounted for 52 percent and 88 percent of the ant populations collected manually from the forest and fallow plots respectively between December 1987 and June 1988. This species was also significantly higher in the pitfall catches of the fallow than the forest plots. Pitfall traps were not effective in sampling the populations of the belligerent Dorylus nigricans. The data are consistent with the widely accepted notion that forested areas support less ants than unforested areas. Differences in physical habitat characteristics, food availability, nesting habits, predation and microenvironmental factors were considered responsible for the differences in activities and abundance of ants in the forest and fallow plots.
Nectar Production of Two Sympatric Species of Columnar Cacti
Authors: Petit Sophie , Freeman C. Edward
Published: March 2006

We examined the potential for exploitation competition by differential attractiveness in two sympatric species of columnar cacti on Curaçao, Netherlands Antilles. Stenocereus griseus and Subpiloccreus repandus have temporally overlapping flowering phenologies and share pollinators. We examined nectar volume, energy contents, and sugar ratios for the entire night and at two‐hour intervals in both cactus species. Except for a burst in nectar volume and sugar concentration by Subpilocereus repandus during the first two hours of anthesis, nectar secretion patterns, energy contents, and sugar ratios (70% hexose) were similar for the two species. The standing crops of nectar in both species were kept very low by bat pollinators. We suggest that the potential for exploitation competition between Stenocereus griscus and Subpilocereus repandus is currently very low on Curapo.
Cyclone‐induced Shift in Foraging Behavior in Flying Foxes in American Samoa1
Authors: Grant Gilbert S. , Craig Peter , Trail Pepper
Published: March 2006

Tropical cyclones pass over or near American Samoa on average about once every 3 years. Because many trees may be stripped of leaves, flowers, and fruit, cyclones exert a major impact on the feeding ecology of nectivorous and frugivorous flying foxes. We examined search time and in‐tree time immediately postcyclone (3–6 weeks) and during a recovery period (15–16 months after the last cyclone). Both Pteropus tonganus and P. samoensis increased search time and decreased tree time (an indication of less food available per tree) immediately after the passage of cyclone Ofa.
Fruit Production and Seed Predation in Two Miombo Woodland Trees in Zambia
Authors: Chidumayo Ernrnanuel N
Published: March 2006

During a six year period (1990–1995) fruiting frequency among marked trees and seed production and predispersal predation by beetle larvae of lsoberlinia angolensis and Julbernardia globiflora of the Leguminosae family and Caesalpinoideae subfamily were studied at two dry miombo woodland sites in central Zambia. Fruit production varied from year to year and was not related to annual rainfall. On average I. angolensis trees fruited once every two years while J. globiflora trees fruited once every two and one‐half years. Number of fruits per tree was correlated with tree size for both species. In a peak year fruit biomass represented two to four percent of total above ground biomass but for J. globiflora about 5.5 and 4.5 percent of nitrogen and potassium, respectively, were in fruits compared to 0.6 and 1.8 percent for I. angolensis. The lower fruiting frequency in J. globifora was probably related to the depletion of N reserves during a fruiting year which required a longer replenishment period than in I. angolensis.

Predispersal seed predation was low for J. globiflora (10%) and very high in I. angolensis (65–85%) and for the latter species predation rate increased from August to November 1991 and significant variations were observed among years and pod types. Seed predation rate was lowest in a peak fruiting year and this observation provides support for the satiation hypothesis. The results of the study also suggest that I. angolensis and J. globiflora may have different regeneration strategies although reproductive allocation in both species was within the range reported for other iteroparous plants.
Patterns of Seed Size, Germination and Seed Viability of Tropical Tree Species in Southern India1
Authors: MURALI K. S.
Published: March 2006

Seed weight, days to germination and seed viability were observed for 99 species growing in the Western Ghats of Karnataka, India. Seed size was strongly correlated with days to germination; smaller seeds germinated faster than larger seeds. Species which flowered during the rainy season had lighter seeds than species which flowered during the dry season. It was also found that seed size and viability of seeds were related to the season of fruiting. Species which fruit during the rainy season had heavier seeds and shorter viability than species which fruit during the dry season. These flowering and fruiting patterns and varying seed sizes are argued to be adaptations to the time of dispersal, time of moisture availability in the habitat and seedling survival.
Habitat Characteristics and Lemur Species Richness in Madagascar1
Authors: Ganzhorn J. U. , Malcomber S. , Andrianantoanina O. , Goodman S. M.
Published: March 2006

In the extant lemur communities of Madagascar the number of lemur species increases with increasing number of tree species. In forests with few tree species lemurs use patches with higher number of tree species than average. However, in forest plots with high number of tree species, lemurs stay in places with lower number of tree species than average. At low tree species diversity a minimum number of different tree species seems to be required within the animals' home range to assure year‐round food availability. At high tree species diversity tree species essential for survival might be diluted by resources which are of no use for lemurs, thus increasing energetic expenses for traveling between suitable patches. According to the present analyses, structural diversity is of subordinate importance to the number of tree species as a correlate of lemur species richness.

Within limits of disturbance intensity and on a small geographic scale, disturbances increase forest productivity. Lemurs reach higher species numbers and population densities in slightly disturbed areas compared with undisturbed sites. This peaked curve of the number of lemur species over disturbance, however, may not only be a consequence of “resource dilution” in undisturbed sites and higher food abundance in slightly disturbed areas, but also a consequence of selective extinction of lemur species which were unable to cope with the disturbance regime exaggerated by human interference over the last few hundred or thousand years.
Facultative Ant‐Plant Interactions: Nectar Sugar Preferences of Introduced Pest Ant Species in South Florida1
Authors: Koptur Suzanne , Truong Ni
Published: March 2006

We observed nectar use by native and exotic ant species in nature, garden, and urban situations, and found ants utilizing floral and extrafloral nectar of a variety of flowering plant species. We collected 31 plant nectars (29 floral, 2 extrafloral) and used them in feeding preference tests against standard solutions of sugars (20 percent fructose, glucose, and sucrose, and their mixture), 10 trials for each nectar‐ant comparison. We compared time‐to‐discovery and total ant visits to each droplet using ANOVA, and found that both trial and solution contributed significantly to the variation in most experiments. Seven of the floral nectars tested were significantly more attractive to certain ant species than the sugar solutions. Not only do ants use floral nectar, but it appears that some floral nectars contain compounds that are especially attractive to ants.
Edaphic Distribution of Some Species of the Fern Genus Adiantum in Western Amazonia1
Authors: Tuomisto Hanna , Poulsen Axel Dalberg , Moran Robbin C.
Published: March 2006

The distribution patterns of Adiantum species were inventoried at twelve noninundated rain forest (tierra firme) sites in Amazonian Peru and Ecuador. Six species belonging to the genus were found, and four of these were abundant at some of the sites. At six of the sites none of the species was particularly abundant. Both the occurrence and the abundance of the species varied among sites with regard to soil texture and concentration of exchangeable bases and within sites with regard to topography. Adiantum tomentosum) Klotzsch was restricted to loamy soils with intermediate to low content of extractable bases and was locally most abundant in the well drained parts of slopes and ridge tops. Adiantum terminatum Kunze ex Miq. and A. humile Kunze occurred at sites with intermediate to high content of extractable bases, but their relative abundances differed among and within sites. Adiantum pulverulentum L. was restricted to soils with relatively high base concentration. Ecological differences among the species obviously explained many of the differences in their distribution patterns at the local and regional scales, and may be important for the understanding of such patterns at biogeographical scales as well.
Pattern and Performance of Understory Bamboos (Chusquea spp.) under Different Canopy Closures in Old‐Growth Oak Forests in Costa Rica1
Authors: Widmer Yvonne
Published: March 2006

The effect of canopy closure on spatial and morphological patterns of three understory Chusquea species was studied in pristine upper montane oak forests. Plots with either Chusquea talamancenis Widmer & L.G. Clark or C. tomentosa Widmer & L.G. Clark were set out in gaps, under intermediate tree canopy and under closed canopy. The third species Chusquea foliosa L.G. Clark was only found in gap and intermediate canopy sites in the study area. Clumps of all bamboo species tend to be few and large under open conditions and numerous and small under more shady conditions. The larger size of clumps in gaps is reflected in the number of culms per clump, the diameter of the culms and, as a consequence, clump basal area, clump crown area, and biomass (index of plant volume) compared to intermediate and closed canopy. The smaller clump density in gaps compared to closed canopy implies that there is more intraspecific competition and density dependent mortality (self‐thinning effect) when a bamboo species is dominant under favourable light conditions. Parameters of performance like culm length, number of nodes per culm, number and length of primary branches, and number of branch nodes seem not to be affected by the light regime, unlike total number of branches, total branch length, and the branching pattern. Species differ in their response to the light environment: C. tomentosa and C. foliosa have a higher degree of morphological plasticity than C. talamancensis, which in turn, appears to be more shade tolerant. No difference between species has been found regarding their contribution to vegetation, parameters reflecting abundance per unit area (site clump area, site crown area and site index of clump volume) were similar for all three species.
The Effect of Rust Infection on Reproduction in a Tropical Tree (Faramea occidentalis)1
Authors: Travers Steven E. , Gilbert Gregory S. , Perry Ethan F.
Published: March 2006

Fungal pathogens that infect reproductive structures of plants (e.g., flowers and fruits) can reduce the seed production and seedling recruitment of host plants. We report here on the effects of a rust, Aecidium farameae, that infects the ovaries and pedicels of mature flowers on Faramea occidentalis (Ruhiaceae), a small tree common on Barro Colorado Island, Republic of Panama. Rust infection of ovaries reduced the number of maturing fruit on infected trees. Trees with low rust incidence in June of 1992 had 68 percent fruit survival, compared to 17 percent fruit survival for those with high rust incidence. Infected fruits developed abnormally and were usually aborted long before uninfected fruits were mature. One hundred percent of the infected ovaries marked in July were diseased or missing in August. We conclude that infection by A. farameae has the potential to seriously decrease the reproductive output of Faramea occidentalis and may represent an important source of variation in the relative fitness of individual plants.
Growth Rates of Tree Height Six Years after Hurricane Damage at Four Localities in Eastern Nicaragua1
Authors: Vandermeer John , Brenner Andrew , de la Cerda Iñigo Granzow
Published: March 2006

Growth rates for 44 species of trees in a posthurricane forest in Nicaragua were measured. The pattern is consistent with the interpretation of succession as a two stage process: an initial building phase after the hurricane followed by a thinning phase. Localities that were damaged less from the hurricane are now entering the thinning phase of postdisturbance succession, while those subjected to the most severe damage appear to remain in the building phase.
Mating Systems of Three Tropical Dry Forest Tree Species1
Authors: James Tim , Vege Sunitha , Aldrich Preston , Hamrick J. L.
Published: March 2006

Polymorphic allozyme loci were used to estimate outcrossing rates for three tree species from a disturbed dry forest in southern Costa Rica. Estimates of the multilocus outcrossing rates of Cedrela odorata and Jacaranda copaia were 0.969 and 0.982, respectively, and suggest that these species may be self‐incompatible. The subcanopy tree Stemmadenia donnell‐smithii also demonstrated little self‐fertilization based on an estimated outcrossing rate of 0.896. Significant heterogeneity in pollen allele frequencies among maternal trees was detected for at least two enzyme loci for each species. A test of correlated mating between progeny of S. donnell‐smithii revealed that all seeds within a fruit were singly sired. In addition, the low estimates of biparental inbreeding and significant differences in pollen and ovule allele frequencies for this species suggest that gene flow into the sampled forest fragment may occur. The implications of deforestation on the mating systems of these tropical tree taxa are discussed.
Observations on the Reproductive Biology of Miconia calvescens DC (Melastomataceae), an Alien Invasive Tree on the Island of Tahiti (South Pacific Ocean)1
Authors: Meyer Jean‐Yves
Published: March 2006

Miconia calvescens DC (Melastomataceae) is a dominant invasive species in the tropical oceanic island of Tahiti (French Polynesia, South Pacific Ocean), where it was introduced as an ornamental plant. Whereas this small tree is sparse in its native range of Central America, it has spread in Tahiti into a wide variety of habitats including native wet forests. The remarkable success of this invasion is due in great part to prolific reproduction: a mature tree can bear up to 220 inflorescences with an average of 1330 flowers/inflorescence, 208 fruits/infructescence and 195 seeds/fruit. Two and a half years of phenological observations in a highly invaded site indicated that three major peaks of flowering occur/year over brief periods: flower anthesis lasted a few days and pollen grain germination suggested a short stigmatic receptivity of only a few hours; no pollinators were observed foraging on flowers during our survey; the production of fruits containing viable seeds in bagged inflorescences showed that self‐fertilization can occur; pollen‐ovule ratio (log P/O = 2.68) suggested facultative xenogamy; bagged isolated flowers to test for autogamy and style cutting to learn whether apomixis occured or not were not conclusive. The flowering phenology and the breeding system of M. calvescens enable this plant to build up rapidly successful populations from even a single propagule on the island of Tahiti and on other sites of introduction. The vegetation structure of Polynesian native forests compared to Neotropical rain forests probably plays an important role in determining the reproductive success of M. calvescens and could provide a complementary explanation of the biological invasion processes in tropical oceanic islands.
Occurrence Patterns, Habitat Associations, and Potential Prey of the River Dolphin, Inia geoffrensis, in the Cinaruco River, Venezuela1
Authors: McGuire Tamara L. , Winemiller Kirk O.
Published: March 2006

The distribution, habitat association, group size, population structure, and prey availability of river dolphins (Inia geoffrensis) were studied from November 1993‐June 1994 in the Cinaruco River, a tributary of the Orinoco River that forms the southern boundary of Venezuela's Santos Luzardo National Park. Dolphins were sampled from a boat using modified strip‐width transects, for a total of 418 h. The study area was 1.67 km2, and contained 20 km of water courses. Like other rivers of this region, the Cinaruco River undergoes a seasonal flood cycle. Dolphins were seen most often during the period of falling water (41% of total sightings) and least often during the rising water period (24% of total sightings). Dolphins were seen most often in confluence areas (35% of total sightings) and were seldom seen in side channels (13% of total sightings). The presence of rocks or sandbanks was associated with a greater frequency of dolphin sightings, and sightings increased with habitat heterogeneity. Average group size for the 8‐mo study was 2.0 (±1.0) and was largest during the rising water period. Calves were first sighted during the end of the dry season and became more common during the early flood season. Six individuals were photo‐identified and resighted with one sighted eight times over 186 d. The fish diversity of the study area was high, with 161 species documented in our samples. The stomach of one Inia contained 15 fishes representing at least 4 species.
Use of Alternative Food Plants Exclusively by Adult Male Froghoppers (Homoptera: Cercopidae)1
Authors: Peck Daniel C.
Published: March 2006

Male‐specific associations of adult froghoppers (Homoptera: Cercopidae) with alternative food plant hosts is reported. Four accounts from the field and one from the literature are presented: Iphirhina quota on Bourreria costaricensis (Boraginaceae), Huaina inca on Solanaceae sp., Prosapia simulans and Prosapia sp. (near P. bicincta) on Ilex haberi (Aquifoliaceae), and Prosapia bicincta on Ilex cornuta and Ilex opaca. In three cases host use is limited to adults while in two cases use is limited to only adult males. In four cases adults feed on plants that differ taxonomically, structurally and ecologically from hosts normally utilized by all life stages. These associations are not considered aggregations per se because froghoppers are not clustered and because these associations cannot be explained by the usual criteria supporting the adaptiveness of insect aggregations. Indirect evidence suggests that these unusual hosts may be unavailable to nymphs and not sought by females. This passive lack of opportunity by nymphs and females, in tandem with an active selection/attraction by males, is a plausible explanation for the existence of male‐specific hosts.
The Quantity and Turnover of Dead Wood in Permanent Forest Plots in Six Life Zones of Venezuela1
Authors: Delaney Matt , Brown Sandra , Lugo Ariel E. , Torres‐Lezama Armando , Quintero Narsizo Bello
Published: March 2006

Dead wood can be an important component of the carbon pool in many forests, but few measurements have been made of this pool in tropical forests, To fill this gap, we determined the quantity of dead wood (downed and standing dead) in 25 long‐term (up to 30 yr) permanent forest plots located in six different life zones of Venezuela. Downed wood was separated into fine (< 10 cm in diameter) and coarse (≥ 10 cm in diameter) classes, and three decomposition states (sound, intermediate, or rotten). The total quantity of dead wood, averaged by life zone, was lowest in the dry (2.43 Mg/ha), reached a peak in the moist (42.33 Mg/ha) and decreased slightly in the wet (34.50 Mg/ha) life zone. Most of the dead wood was in the standing dead category (about 42–76% of the total). The decomposition state of dead wood in all plots was mostly rotten (45%) or intermediate (44%); there was little sound wood (11%). Turnover rates of dead wood generally ranged between 0.03/yr to 0.52/yr with no clear trend with life zone. The large amount of dead wood in some plots was equivalent to about 20 percent or less of aboveground biomass, indicating that dead wood can represent a significant amount of carbon in these forests.
Growth, Net Production, Litter Decomposition, and Net Nitrogen Accumulation by Epiphytic Bryophytes in a Tropical Montane Forest1
Authors: Clark Kenneth L. , Nadkarni Nalini M. , Gholz Henry L.
Published: March 2006

To understand the ecological roles of epiphytic bryophytes in the carbon (C) and nitrogen (N) cycles of a tropical montane forest, we used samples in enclosures to estimate rates of growth, net production, and N accumulation by shoots in the canopy, and litterbags, to estimate rates of decomposition and N dynamics of epiphytic bryophyte litter in the canopy and on the forest floor in Monteverde, Costa Rica. Growth of epiphytic bryophytes was estimated at 30.0–49.9 percent/yr, net production at 122–203 g/m2/yr, and N accumulation at 1.8–3.0 g N/m2/yr. Cumulative mass loss from litterbags after one and two years in the canopy was 17 ± 2 and 19 ± 2 percent (mean ± 1 SE) of initial sample mass, respectively, and mass loss from litter and green shoots in litterbags after one year on the forest floor was 29 ± 2 and 45 ± 3 percent, respectively. Approximately 30 percent of the initial N mass was released rapidly from litter in both locations. Nitrogen loss from green shoots on the forest floor was greater; about 47 percent of the initial N mass was lost within the first three months. There was no evidence for net N immobilization by litter or green shoots, but the remaining N in litter was apparently recalcitrant. Annual net accumulation of C and N by epiphytic bryophytes was estimated at 37–64 g C/m2/yr and 0.8–1.3 g N/m2/yr, respectively. Previous research at this site indicated that epiphytic bryophytes retain inorganic N from atmospheric deposition to the canopy. Therefore, they play a major role in transforming N from mobile to highly recalcitrant forms in this ecosystem.
Growth Rings, Phenology, Hurricane Disturbance and Climate inCyrilla racemifloraL., a Rain Forest Tree of the Luquillo Mountains, Puerto Rico1
Authors: Drew Allan P.
Published: March 2006

The growth phenology ofCyrilla racemifloraL., the dominant tree species of the montane rain forest, (subtropical lower montane rain forest, sensu Holdridge) of the Luquillo Mountains of Puerto Rico was studied intensively during 1989, and then semiannually through mid‐1993 to determine the periodicity of changes in xylem structure. Four trees at 770 m were monitored for flowering, branch elongation, leaf litterfall, and xylem cell growth and differentiation in the lower stem, and these events were related to local seasonal patterns of rainfall and temperature. Hurricane Hugo defoliated study trees in September, 1989.

Bud‐break and branch elongation in March, 1989 were followed by earlywood xylem cell production in the lower stem in April and the onset of flowering in May. Leaf litterfall was greatest between April and June, coinciding with peak branch growth and new leaf formation. Latewood xylem was produced in December. The general phenological pattern was synchronized between trees and over study years. Vessel diameter and density were monitored along with thickness of earlywood and latewood and the former converted to vessel lumen area, a measure of xylem conductance capacity. Annual growth rings were formed with periods of earlywood and latewood production coinciding with traditional summer (rainy) and winter (dry) seasons, respectively, in the Luquillo Mountains.

Hurricane defoliation was followed by heavy flowering in 1990, a year of reduced branch elongation and annual xylem ring width, and was associated with maximum vessel lumen area, as was flowering in 1989, prior to the hurricane. Hurricane Hugo provided a perturbation that, through its elicited stress response, allowed for the demonstration of the interplay between flowering, branching, structural growth of xylem, and xylem function.