bluuebunny/crossref_metadata_2025_split huggingface dataset:
Methodological Issues in Research on Sexual Behavior with Latino Gay and Bisexual Men
Authors: Zea María Cecilia , Reisen Carol A. , Díaz Rafael M. 
Published: June 2003

AbstractLatino gay men are at high risk for HIV/AIDS, and therefore it is critical that we increase our understanding of their sexual behavior. This paper discusses theoretical and methodological issues of conducting research with Latino gay and bisexual men. The importance of culture in psychological theory addressing sexual behavior is highlighted. Cultural and socioeconomic forces that impact the social construction of sexuality and sexual risk need to be taken into account to increase research validity. Social context and internalized sociocultural experiences can affect a variety of issues, including sexual scripts and the definition and fluidity of sexual orientation identity. Moreover, Latino gay men's sexuality may be influenced by experiences of oppression, discrimination, racism, and homophobia. Level of acculturation should also be considered. Measures that are developed by taking into account the cultural context and incorporating a Latino perspective are helpful in conducting meaningful research. Triangulation of quantitative and qualitative methods will help provide a picture rich in context and at the same time generalizable. The relationship between researchers and participants is affected by Latino cultural styles, and suggestions for approaches to conduct research in the Latino gay community are offered.
Exploring Dynamics of Abusive Lesbian Relationships: Preliminary Analysis of a Multisite, Qualitative Study
Authors: Ristock Janice L. 
Published: June 2003

AbstractThis paper presents preliminary results from a multisite, qualitative study on violence in lesbian relationships. A framework for conducting community‐based, empowerment research that draws on theories of community psychology, feminism, and postmodernism is presented. The study was designed to understand the dynamics of abusive lesbian relationships and social service providers' responses to the abuse. Results from 80 in‐depth interviews with lesbians who have experienced relationship violence are examined with a particular focus on a pattern of first relationships being abusive and a theme of shifting power dynamics. Analysis of focus group discussions with 45 feminist service providers (e.g., counselors, shelter workers, social workers, healthcare providers) reveals the difficulties in assessing the power dynamics of abusive same‐sex relationships and in developing appropriate responses when relying on heterosexually gendered models developed to address men's violence against women. The preliminary results present implications both for how we theorize and research this form of violence, and for improving the practices and policies of social services that work with lesbian, gay, bisexual, and transgendered communities.
Effect of underground fungus‐growing termites on carbon dioxide emission at the point‐ and landscape‐scales in an African savanna
Authors: Konaté S. , Roux X. Le , Verdier B. , Lepage M. 
Published: June 2003

Summary

The rate of CO2 emission by two major termite species (Ancistrotermes cavithorax and Odontotermes n. pauperans) was studied in a West African savanna (Lamto, Côte d’Ivoire). First, in three major savanna types (grassy, shrubby and woody savannas), CO2 emission from the soil surface was measured using a closed container system. Control soil without termite fungus‐comb chambers, and soil of eroded termite mound with or without Odontotermes fungus‐comb chambers was sampled in each savanna type. Second, the mass‐specific respiration rate of the different components of termite fungus‐comb chambers (i.e. workers, soldiers, fungus comb and chamber walls) was measured under laboratory conditions. CO2 emission by termites at the landscape‐scale was computed from both field biomass data and laboratory measurements.
Whatever the savanna type, CO2 emission from the soil surface was not different between control soil and soil of eroded termite mound without termite fungus‐comb chambers, but was significantly higher in areas with fungus‐comb chambers than in areas without fungus‐comb chambers (10–19 µmol CO2 m−2 s−1vs 5–10 µmol CO2 m−2 s−1).
The mass‐specific respiration rates were higher for individuals of O. pauperans than for individuals of A. cavithorax. Total respiration rate from an individual fungus‐comb chamber was around 56 and 143 µmol CO2 h−1 for Ancistrotermes and Odontotermes, respectively.
Despite a low mass‐specific respiration rate, fungus comb accounted for 51% of the total respiration flux from whole chambers in Odontotermes and for 82% in Ancistrotermes. The laboratory‐derived respiration rate from individual Odontotermes chambers was consistent with the field estimates.
At the landscape‐scale, the CO2 emission due to A. cavithorax and O. pauperans was 0·022 and 0·050 µmol CO2 m−2 s−1, respectively. This total (27·2 g C m−2 years−1) represented 4·9% of the total above‐ground net primary production in this ecosystem and 11·3% of the carbon not mineralized by annual fires.
Fractal index captures the role of vegetation clumping in locust swarming
Authors: Despland E. 
Published: June 2003

Summary

This paper evaluates box‐counting dimension as a quantitative clumping index for discontinuous plant cover, and applies it to studies of both small‐ and large‐scale ecological processes in desert locust (Schistocerca gregaria) swarming.
The quadrat under study is tiled with squares of increasing size, and the relationship between the number of occupied squares and square size gives the box‐counting dimension. This index is high for random distributions and decreases when the vegetation is clumped; it is also positively linked to the abundance of vegetation.
At the scale of individual locusts, this index captures the space‐filling properties of vegetation that promote change to the gregarious phase and the onset of swarming. At the very large scale, box‐counting dimension measured from satellite imagery reflects topography, which influences the concentration and migration of locust swarms.
Fractal geometry considers scale of measurement in quantifying pattern and provides a framework to interpret ecological phenomena across spatial scales. Demonstration of a statistically significant relationship between the box‐counting exponent and locust behaviour shows how this approach can be applied to ecological studies.
The effect of wasps and ants on the reproductive success of the extrafloral nectaried plantTurnera ulmifolia(Turneraceae)
Authors: Cuautle M. , Rico‐Gray V. 
Published: June 2003

Summary1. To assess the effectiveness of extrafloral nectaries (EFN) as a defensive mechanism of plants it is vital to use a multiple interactions approach and assess the contribution of all visiting species and their interactions.2. The effect of EFN‐visiting ants (Camponotus planatus,C.abdominalis,Conomyrmasp.,Crematogaster brevispinosa,Foreliussp.,Pseudomyrmexsp.) and wasps (Polistes instabilis,Polybia occidentalis) on the reproductive success (estimated as the number of reproductive structures) ofTurnera ulmifolia(Turneraceae) was experimentally evaluated. Herbivory effects were tested usingEuptoieta hegesialarvae (caterpillars), which is the main herbivore of this plant. The study was done in a coastal sand dune scrub in Veracruz, México.3. Wasps and ants were selectively excluded using a two‐factor design (Wasps, Ants) block design, both factors with two levels (absent, present). The response variables were an index of herbivory per branch and the number of buds, flowers, ripe and unripe fruit per plant, and the seed/fruit ratio per branch.4. After a week of placing the larvae on experimental plants, they were significantly more frequent on plants where wasps and ants had been experimentally excluded.5. Wasp presence was associated significantly with greater numbers of buds, flowers, ripe fruit and seeds. When acting separately, wasps and ants exerted a positive effect in decreasing herbivory levels and increasing the number of unripe fruit; when acting together, however, their effect was not additive.6. This is the first demonstration of a positive effect on the plant by wasps associated with EFN. The ecological implication of this finding is that the function of EFN and the ultimate effects on a plant will probably depend on the array of organisms visiting its EFN.
Tropospheric O3 moderates responses of temperate hardwood forests to elevated CO2: a synthesis of molecular to ecosystem results from the Aspen FACE project
Authors: Karnosky D. F. , Zak D. R. , Pregitzer K. S. , Awmack C. S. , Bockheim J. G. , Dickson R. E. , Hendrey G. R. , Host G. E. , King J. S. , Kopper B. J. , Kruger E. L. , Kubiske M. E. , Lindroth R. L. , Mattson W. J. , Mcdonald E. P. , Noormets A. , Oksanen E. , Parsons W. F. J. , Percy K. E. , Podila G. K. , Riemenschneider D. E. , Sharma P. , Thakur R. , Sôber A. , Sôber J. , Jones W. S. , Anttonen S. , Vapaavuori E. , Mankovska B. , Heilman W. , Isebrands J. G. 
Published: June 2003

Summary

The impacts of elevated atmospheric CO2 and/or O3 have been examined over 4 years using an open‐air exposure system in an aggrading northern temperate forest containing two different functional groups (the indeterminate, pioneer, O3‐sensitive species Trembling Aspen, Populus tremuloides and Paper Birch, Betula papyrifera, and the determinate, late successional, O3‐tolerant species Sugar Maple, Acer saccharum).
The responses to these interacting greenhouse gases have been remarkably consistent in pure Aspen stands and in mixed Aspen/Birch and Aspen/Maple stands, from leaf to ecosystem level, for O3‐tolerant as well as O3‐sensitive genotypes and across various trophic levels. These two gases act in opposing ways, and even at low concentrations (1·5 × ambient, with ambient averaging 34–36 nL L−1 during the summer daylight hours), O3 offsets or moderates the responses induced by elevated CO2.
After 3 years of exposure to 560 µmol mol−1 CO2, the above‐ground volume of Aspen stands was 40% above those grown at ambient CO2, and there was no indication of a diminishing growth trend. In contrast, O3 at 1·5 × ambient completely offset the growth enhancement by CO2, both for O3‐sensitive and O3‐tolerant clones. Implications of this finding for carbon sequestration, plantations to reduce excess CO2, and global models of forest productivity and climate change are presented.
Anther arrangement influences pollen deposition and removal in hermaphrodite flowers
Authors: Kudo G. 
Published: June 2003

Summary

Effects of anther arrangement on pollen deposition and removal in hermaphrodite flowers were experimentally quantified to assess the ecological significance of stamen structure. The anther arrangement of Brassica rapa was modified into six types with respect to anther number and the spatial arrangement of long and short stamens. Each anther treatment was combined with a nectar‐intact and nectar‐depleted treatment. After single visits by bumblebees in a glasshouse, the visit duration to each flower and the number of pollen grains deposited on stigmas and pollen grains remaining in long and short anthers were measured.
Visits were significantly shorter in nectar‐depleted flowers. Short anthers also extended visit duration, but modification of the long anther arrangement had no effect. Pollen deposition on stigmas depended on the number of long anthers and on visit duration. Although an increase in long anther number accelerated self‐pollination, removal of short anthers did not influence pollen deposition.
Pollen removal from long anthers depended on anther treatment and visit duration, but not on nectar availability. Any modification of anther arrangement tended to increase pollen removal during single visits. Long anthers contributed to the decrease in pollen removal per visit, while pollen removal from short anthers depended only on visit duration. Short anthers appeared to have a different function from the restriction of pollen removal during single visits by bumblebees.
Thus, long and short anthers made different contributions to pollination efficiency of nectar‐feeding bumblebees. The maintenance of different types of stamens in Brassicaceae plants (tetradynamous stamens) may reflect functional advantages for a diverse pollination syndrome if the pollination efficiency of long and short anthers varies depending on the type of pollinator.
Reduced burst speed is a cost of rapid growth in anuran tadpoles: problems of autocorrelation and inferences about growth rates
Authors: Arendt J. D. 
Published: June 2003

Summary

It is becoming clear that individual growth rates are optimized to suit local conditions rather than maximized to be as fast as possible. To understand this adaptive variation in growth rates, we need to understand the costs of rapid growth.
Recent work in teleost fish suggests that a trade‐off between growth rate and critical swimming speed may be common. The current study demonstrates that the trade‐off also occurs in anuran tadpoles with regard to burst speed.
Individual growth rate and burst speed were compared in Bufo americanus and Scaphiopus hamondi, representatives of two distantly related anuran families. Path analysis showed that growth rate is negatively correlated with burst speed. Because the trade‐off between growth rate and swimming speed occurs in two such distantly related anuran species as well as teleosts, it may be general for all vertebrates.
However, identifying costs of rapid growth is complicated by the indirect effects of growth rate on body size which will also often correlate with performance factors. Distinguishing between direct effects of growth rate and indirect effects through body size is difficult because the two necessarily result in collinearity. A randomization test shows just how severe this problem can be.
Attack strategy of an ambush predator: which attributes of the prey trigger a pit‐viper's strike?
Authors: Shine R. , Sun L.‐X. 
Published: June 2003

Summary

Why do larger predators generally consume larger prey items? Endemic pit‐vipers (Gloydius shedaoensis) on a small island in north‐eastern China ambush passerine birds, usually from the branches of small trees. Both minimum and maximum prey sizes increase with predator size.
To clarify the reasons for this ontogenetic shift, 251 snakes in ambush postures were approached and offered potential prey items (dead birds, or models covered in feathers) to clarify the cues that trigger a foraging strike.
The snakes struck at the prey item in 101 of these trials, and this ‘decision’ was influenced by the size, movement and temperature of the prey item. A pit‐viper's body size influenced its prey‐size selectivity, with larger snakes refusing to strike at smaller prey items. Larger snakes also scavenge dead birds too large for smaller snakes to ingest, but do not ignore live birds: even the largest snakes use prey movement and prey temperature as cues to elicit feeding strikes.
The ontogenetic shift in prey size thus reflects a combination of processes. The absence of large prey from the diet of small snakes is due to gape‐limitation (these snakes strike and attempt to swallow much larger prey). The absence of small prey items from the diet of larger snakes is due to active refusal to strike at small prey, as well as a behavioural shift to scavenging and to terrestrial rather than arboreal ambush‐sites (and thus, higher rates of encounter with large prey items) by larger pit‐vipers.
Defoliation alters water uptake by deep and shallow roots of Prosopis velutina (Velvet Mesquite)
Authors: Snyder K. A. , Williams D. G. 
Published: June 2003

Summary

Prosopis velutina Woot. (Velvet Mesquite) at a site with limited groundwater availability derived a greater percentage of water from shallow soil at the onset of the summer rainy season than did trees at a site with greater availability of groundwater. Predawn leaf water potentials (Ψpd) were not a strong indicator of shallow water use for this species with roots in multiple soil layers.
We experimentally defoliated P. velutina plants to determine if reduced‐canopy photosynthesis would alter vertical patterns of root activity. After natural rain events, hydrogen isotope ratios of xylem sap indicated that defoliated P. velutina took up a greater percentage of its water from shallow soils than did undefoliated plants.
Irrigation with deuterium‐labelled water further demonstrated that undefoliated plants were able to use shallow soil water. Defoliation appeared to affect the ability of trees to use deep‐water sources.
Reduced carbon assimilation limited water uptake from deep soil layers. These data highlight that there are internal physiological controls on carbon allocation that may limit water uptake from different soil layers. During periods of high vapour pressure deficit or soil drought, when leaf gas exchange and carbon assimilation decline, this may create positive feedbacks where plants are unable to forage for deep water due to carbon limitations.
High daily energy expenditure of incubating shorebirds on High Arctic tundra: a circumpolar study
Authors: Piersma T. , Lindström Å. , Drent R. H. , Tulp I. , Jukema J. , Morrison R. I. G. , Reneerkens J. , Schekkerman H. , Visser G. H. 
Published: June 2003

Summary

Given the allometric scaling of thermoregulatory capacity in birds, and the cold and exposed Arctic environment, it was predicted that Arctic‐breeding shorebirds should incur high costs during incubation. Using doubly labelled water (DLW), daily energy expenditure (DEE) during incubation was measured in eight shorebird species weighing between 29 and 142 g at various sites in the Eurasian and Canadian High Arctic. The results are compared with a compilation of similar data for birds at lower latitudes.
There was a significant positive correlation between species average DEE and body mass (DEE (kJ day−1) = 28·12 BM (g)0·524, r2 = 0·90). The slopes of the allometric regression lines for DEE on body mass of tundra‐breeding birds and lower latitude species (a sample mostly of passerines but including several shorebirds) are similar (0·548 vs 0·545). DEE is about 50% higher in birds on the tundra than in temperate breeding areas.
Data for radiomarked Red Knots for which the time budgets during DLW measurements were known, indicated that foraging away from the nest on open tundra is almost twice as costly as incubating a four‐egg clutch.
During the incubation phase in the High Arctic, tundra‐breeding shorebirds appear to incur among the highest DEE levels of any time of the year. The rates of energy expenditure measured here are among the highest reported in the literature so far, reaching inferred ceilings of sustainable energy turnover rates.
Body size and the timing of egg production in parasitoid wasps: a comparative analysis
Authors: Jervis M. A. , Ferns P. N. , Heimpel G. E. 
Published: June 2003

Summary1. The ovigeny index, previously identified as both a significant fitness variable in parasitoid wasps and an important factor in parasitoid–host population dynamics, is the proportion of the maximum potential lifetime complement of eggs that is mature when the female emerges into the environment following pupal development. We tested the hypothesis that ovigeny index varies with female body size in parasitoid wasps. Body size measurements were obtained for 40 species in 13 families, representing a broad taxonomic and morphological diversity of parasitoid wasps. There was an almost 18‐fold difference in size between the smallest and the largest species.2. Ovigeny index is shown to be negatively correlated with body size across species – smaller wasps have a higher proportion of eggs mature at emergence than do larger wasps – a result supporting the hypothesis. This relationship has previously been observed within species.3. The previously reported cross‐species negative correlation between life‐span and ovigeny index is robust, as it still holds when variation in body size is controlled for.4. We discuss the likely selective factors in the evolution of a link between ovigeny index and body size across species.
Density‐dependent growth of Sea Lamprey larvae: evidence for chemical interference
Authors: Rodríguez‐Muñoz R. , Nicieza A. G. , Braña F. 
Published: June 2003

Summary

Density can influence growth through exploitation competition and behavioural or chemical interference. Negative effects of population density on the growth rate of Sea Lamprey larvae have been reported in several field and laboratory studies, but the mechanisms involved are poorly understood.
In this study the role of population density and waterborne‐mediated interference on the growth rate of Sea Lamprey larvae was assessed in two laboratory experiments. The effects of these factors were evaluated by comparing growth of larvae reared at three different densities (27, 75 and 128 individuals m−2) or in preconditioned water (i.e. containing Sea Lamprey larvae at the same three densities).
Larval density had a negative effect on growth rates. Water conditioning had a negative but weaker effect on growth. Larvae reared in water preconditioned at the two higher densities showed a lower mass increase than those growing in water preconditioned at the lowest density.
The results are consistent with the existence of some chemical or biological agent released into the surrounding water and influencing growth in larval Sea Lampreys. However, chemical interference is not the only factor influencing density‐dependent growth.
Is rate of ontogenetic growth constrained by resource supply or tissue growth potential? A comment on Westet al.'s model
Authors: Ricklefs R. E. 
Published: June 2003

SummaryWestet al. (2001) describe a general model of ontogenetic growth in which growth represents the surplus of energy acquisition over maintenance energy requirement, which themselves are allometric (power) functions of body mass with exponents3/4and 1, respectively. Furthermore, the intercept of the maintenance requirement decreases with the –1/4power of adult mass.These relationships determine the sigmoid shape of the postnatal growth curve and the3/4allometric slope of time to complete growth as a function of adult mass.Westet al.'s growth function is a particular form of the generalized Pütter growth model dm/dt = amy − bmz, which includes other familiar growth functions, such as the logistic and von Bertalanffy equations.Empirical estimates of the allometry of resting metabolism in growing birds are close toz = 1 in some precocial species, but are approximately 50% higher in altricial and semiprecocial birds, which challenges the generality of any single growth function for birds.Rather than growth rate being limited by the difference between energy acquisition and maintenance expenditure, it may also be determined by the growth potential of tissues, which is traded off against functional capacity. Predicted growth curves based on increasing tissue function with age are indistinguishable from the Westet al. and related equations.Models based on growth rate–functional maturity trade‐offs also can produce observed allometric relationships of growth rate to adult mass by incorporating the relative size of the chick at hatching.In contrast to Westet al.'s model, declining variance in size among individuals as chicks approach adult size implies targeted growth and control of growth rate by feedbacks of body size itself on growth rate.The existence of plausible alternative hypotheses for the control of postnatal growth should stimulate additional experimental studies to elucidate mechanisms of growth rate regulation and to understand the evolutionary diversification of postnatal growth.