bluuebunny/crossref_metadata_2025 huggingface dataset:
Ecotope Characteristics of Coexisting Erythroneura Leafhoppers (Homoptera; Cicadellidae) on Sycamore
Authors: McClure Mark S. , Price Peter W.
Published: May 2006

Eight species of leafhoppers (Homoptera: Cicadellidae) of the genus Erythroneura (maculata group) breed on the American sycamore, Platanus occidentalis L. Several occur sympatrically in many areas throughout the range of their host plant even though they have been shown to compete severely for the last 9 weeks of the season in Illinois. The species are E. arta Beamer, E. bella McAtee, E. hymettana Knull, E. ingrata Beamer, E. lawsoni Robinson, E. morgani (DeLong), E. torella Robinson, and E. Usitata Beamer. Five of these are sibling species. Ecotope characteristics (niche and habitat) were examined to determine the factors which permit coexistence in this leafhopper guild on sycamore. The five niche or intracommunity factors examined were temporal utilization, distribution within the canopy, occurrence on leaves of various sizes and ages, and location of feeding sites on the leaf. There were insufficient differences between species for all five niche parameters to explain coexistence in the guild by niche segregation. Three habitat or intercommunity parameters were examined: occurrence on trees alone a moisture gradient, latitudinal distribution with respect to that of sycamore, and distribution within a given geographical locality. There were sufficient differences in the latter two parameters to explain coexistence by habitat segregation. The peak proportional abundances of seven of the eight species occurred in different latitudinal zones and the degree to which the distribution of each species was overlapped by those of all the other Erythroneura ranged from only 0.10 to 0.63 (° = 0.42). Data indicate that species whose ranges over—lapped substantially have apparently evolved differences in their manner of resource utilization, thus reducing competition through character displacement or through a shift in the adaptive mode of the population. There was a tendency for each species to become more unevenly distributed locally from its distributional center; this further reduced geographical overlap between species. Overall proportional similarities (PS), calculated for latitudinal and local distributions were low (PS range from 0.00 to 0.44; ° = 0.17 where PS_(max) = 1.0 and PS_(min) = 0.0). We infer that habitat segregation in the guild permits coexistence. Additional mechanisms which may permit coexistence are discussed.
Plant Standing Crop and Productivity Relations in a Scirpus‐Equisetum Wetland
Authors: Auclair A. N. D. , Bouchard A. , Pajaczkowski J.
Published: May 2006

Plant standing crop and productivity relations were examined for an extensive marsh complex in southern Quebec, Canada. Forty—five 1—m2 plots were sampled for dry weight shoot biomass, species composition, structure (species density, diversity, height), and soil parameters including nutrient concentrations. (Ca, K, Mg, Na, N, P), pH, organic matter, and water depth. Shoot net productivity and decomposition rates were computed for 20—day intervals across the growing season. Relationships between all parameters were examined by principal components analysis. Dominant emergent species included Scirpus fluviatilis, Equisetum fluviatile, Scirpus validus, Phragmites communis, and Eleocharis palustris. For a 150—day interval, shoot net productivity averaged 6.10 g·m(—2) · day(—1) and terminal standing crop was 845 g/m2. Seasonal productivity showed a strong bimodal pattern with peaks in late July (12.90 g°m(—2) · day(—1) and midSeptember 4.73 g°m(—2) · day(—1). Species typical of deep water showed much earlier and higher peak productivity than this general pattern but net shoot productivity as of short duration. Two—thirds of annual litter production was lost by export. Complete decomposition of remaining litter occurred within the next growing season. Temperature and decomposition rate maxima coincided with peak productivity in July and decreased exponentially through October. Among edaphic parameters, soil K had the highest correlation (r = 0.49**) with standing crop while soil N had the highest correlation with shoot net primary production (r = 0.39**). Soil P correlated negatively with all production and soil nutrient parameters except soil Mg levels. It was the only nutrient with a soil concentration maximum in shallow water. Other nutrients attained maximum levels at an intermediate point on the water depth gradient. Maximum litter standing crop occurred at this point, coinciding closely with changes in soil cation levels. While shoot density and standing crop followed these trends, they coincided more closely with changes in soil anion concentrations (nitrogen, hydrogen). Sedimentation and nutrient uptake associated with high stem density and standing crop were shown to be important factors in site enrichment. Shoot net primary productivity and standing crop correlated negatively with all measures of species diversity. Variety and equitability decreased from 8.00 species and 0.96 bits/m2 in Scirpus validus stands of deep water to 2.00 species and .01 bits/m2 in shallow stands of S. fluviatilis. Sparse canopy cover and high levels of disturbance in S. validus stands made possible the coexistence of a rich variety of aquatic life forms not possible under conditions of intense competition typical of S. fluviatilis.
Nitrogen Uptake and Release in a Forested Watershed, Lake Tahoe Basin, California
Authors: Coats Robert N. , Leonard Robert L. , Goldman Charles R.
Published: May 2006

Inorganic nitrogen supply is an important factor limiting primary productivity in Lake Tahoe, Californai—Nevada. To estimate the influence of a watershed ecosystem on nitrogen input to the lake, samples of precipitation, soil water and stream water were collected and analyzed for NO_3—N, NH_4—N and, with less intensity, dissolved organic nitrogen. Factors controlling nitrification in selected plots were studied using a soil perfusion technique. Inorganic nitrogen input by precipitation to the watershed is 1—2 kg° ha(—1)°yr(—1). Output of inorganic nitrogen from the watershed to the lake is 10 to 33% of the precipitation input. Inorganic nitrogen is removed from snowmelt water almost completely by well—developed conifer stands, but less efficiently by poorly developed or disturbed stands. Alder stands release NO_3—N to soil water especially in fall and early winter. Nitrification does occur in some coniferous forest soils in the watershed and is closely associated with NO_3—N release. The occurrence of significant nitrification in the watershed is related more to the C:N ratio and stand basal area than to either pH or release of toxic substances by decaying litter.
Carnivory by an Aquatic Detritivore, Clistoronia Magnifica (Trichoptera: Limnephilidae)
Authors: Anderson N. H.
Published: May 2006

The limnephilid caddisfly, Clistoronia magnifica, was reared through three generations on a detritus—based diet enriched with wheat grains and green grass. Developmental time was reduced and weight of mature larvae and pupae was increased by addition of enchytraeid worms to the above diet. Supplemental feeding on animals is also likely in the field but its importance would be underestimated because, in comparison with detritus, animal tissue would be a small component of the gut contents.
Population Stability of a Tropical Lizard
Authors: Andrews Robin M.
Published: May 2006

Populations of the lizard Anolis limifrons were censused for 19 yr at the Lutz site on Barro Colorado Island (BCI) and for 4 yr at 20 additional sites in central Panama. Census data provided estimates of population density at the end of the west season (December) and indices of per—capita food intake and annual recruitment. Year—to—year changes in density of as much as 5— to 8—fold were observed at Lutz over 19 yr and of 2— to 3—fold were observed over 4 yr at other sites. Changes in population density at 11 BCI sites were synchronous over 1983—1986, while population density fluctuated independently at non—BCI sites. Populations of A. limifrons exhibited significantly greater generation—to—generation variability than populations of West Indian Anolis and of lizards in temperate—zone habitats (mostly arid lands in North America). An index of per—capita food intake was negatively related to density both for temporal comparisons of Lutz and for spatial comparisons among sites. The relative number of young individuals at the end of the wet season was negatively related to population density and positively related to an estimate of food intake. Partial correlations indicated that the positive association between the relative number of young individuals in the population and food intake was independent of the negative association between food intake and population density. Recruitment was thus depressed when density was high and enhanced when food was relatively abundant. Despite the potential for density—dependent regulation, Anolis limifrons populations are highly unstable, presumably because of random perturbations of the environment. Rainfall is implicated casually although population density was only weakly associated with rainfall—density at BCI was positively associated with rainfall during the dry season and negatively associated with rainfall during the wet season and with total annual rainfall. Population attributes that contribute to instability are rapid population turnover and a middle—level trophic position in a complex food web.
Susceptibilities of Ten Rotifer Species to Interference From Daphnia Pulux
Authors: Gilbert John J.
Published: May 2006

Culture experiments showed that 10 rotifer species differed greatly in their susceptibilities to mechanical interference from Daphnia pulex. Direct observations and videographic analyses of rotifers entrained in Daphnia's inhalant feeding current provided some mechanistic explanations for these differences in susceptibility. In general, well—protected species either: (1) were too large to enter Daphnia's branchial chamber (Conochilus unicornis), (2) regularly escaped from Daphnia's inhalent current (Polyarthra remata), or (3) were rejected from Daphnia's branchial chamber after very short residence times (<2 s) (Asplanchna priodonta, Keratella crassa, K. testudo, Synchaeta pectinata). Highly susceptible species were rejected from Daphnia's branchial chamber only after relatively long residence times (6—15 s) and were either small in size (Keratella cochlearis, Synchaeta ablonga) or delicate (Ascomorpha ecaudis). Species with the longest residence times probably are those that are least likely to irritate Daphnia's branchial chamber and hence the most likely to be eaten or manipulated and damaged before being detected and rejected. In natural zooplankton communities, Daphnia interference has the potential to impose high morality rates on susceptible rotifer species and, therefore, to shift the species structure of rotifer assemblages in favor of resistant species. The ability of Daphnia to suppress most rotifer species in natural communities probably is often due to the combined effects of interference and exploitative competition. Large rotifer species least susceptible to Daphnia interference should be the most susceptible to declining food availability.
Responses of a Key Intertidal Predator to Varying Recruitment of Its Prey
Authors: Robles Carlos , Sherwood-Stephens Robin , Alvarado Mario
Published: May 2006

How a predator responds to fluctuating prey abundances determines its capacity to regulate the prey's population levels. Unlike many terrestrial and a few marine arthropods, key intertidal invertebrate predators, e.g., sea stars and whelks, have been portrayed as lacking rapid behavioral responses that would permit them to control episodes of massive prey recruitment. Our field experiments demonstrated that intertidal sea stars, Pisaster ochraceus, rapidly change densities and alter diet in response to varying recruitment of their prey, the mussels Mytilus spp. Densities of Pisaster foraging at high tide were positively correlated with an index of recruitment of Mytilus californianus. The sea stars aggregated in episodes of massive mussels recruitment and dispersed as local abundances of juveniles mussels declined. Aggregation and dispersal were reproduced in field experiments by adding or removing masses of 1st—yr Mytilus spp. to naturally occurring mussel beds. Over the 7 yr of the study, the lower margins of the mussel beds, a distributional limit set at least in some circumstances by the sea stars, remained relatively constant, despite significant year—to—year variation in mussel recruitment rates. We speculate that aggregation acts in concert with previously hypothesized long—term responses to stabilize the lower distributional limits of the mussels.
Analysis of Short Time Series: Correcting for Autocorrelation
Authors: Bence James R.
Published: May 2006

Short time series are common in environmental and ecological studies. For sample sizes of 10 to 50, I examined the performance of methods for adjusting confidence intervals of the mean and parameters of a linear regression for autocorrelation. Similar analyses are common in econometric studies, and serious concerns have been raised about the adequacy of the common adjustment approaches, especially for estimating the slope of a linear regression when the explanatory variable has a time trend. Use of a bias—corrected estimate of the autocorrelation, either in an adjusted t test or in two—stage approach, outperformed other methods, including maximum likelihood and bootstrap estimators, in terms of confidence interval coverage. The bias correction was, however, sometimes awkward to apply. It was generally better to test for autocorrelation at the 0.5 level and use ordinary least squares if the test was not significant, although this pretesting mainly helped for weak autocorrelation and small sample sizes. For the best methods, the coverage was sometimes still substantially less than the stated 95% when autocorrelation was strong, even for sample sizes as large as 50. This was true for estimates of the mean, the regression intercept, and, when the explanatory variable had a time trend, the slope. Simulation results and an example show that different adjustment methods can produce substantially different estimates and confidence intervals. Cautious interpretation of confidence intervals and hypothesis tests is recommended.
Convergence and Divergence of Old‐Field Plant Communities Along Experimental Nitrogen Gradients
Authors: Inouye Richard S. , Tilman David
Published: May 2006

Data from experiments in three old fields were analyzed using similarity indices and population trajectories to determine if similarity of resource supply rates influenced the similarity of plant community composition. In two of three fields, similarity indices indicated that experimental plots having different resource supply rates diverged in species composition with time. There was some evidence of convergence both within and between fields on plots with similar resource supply rates; however, divergence was also common, especially at high rates of nutrient supply. Much of the divergence indicated by similarity indices can be explained by plot—to—plot differences in the initial abundances of three dominant species: Agropyron repens, Poa pratensis, and Schizachyrium scoparium. High nitrogen treatments favored Agropyron repens if it was present, but led to major increases in P. pratensis or S. scoparium if A. repens was absent. The trajectories through time of these three species suggest that plots will converge at high nitrogen levels.
Size‐Dependent Growth in Two Zoanthid Species: A Constrast in Clonal Strategies
Authors: Karlson Ronald H.
Published: May 2006

The widespread occurrence of genet fragmentation among modular, clonal organisms results in size—dependent life history patterns that are often independent of clonal age. In this study the size dependence of clonal growth rates was experimentally evaluated using two common coral reef cnidarians that inhabit shallow reef environments at Discovery Bay, Jamaica. As a result of the turbulent conditions associated with storms, these organisms commonly undergo fragmentation. The growth of aggregations of these clonal fragments in three small size classes (ranging over three orders of magnitude) was statistically evaluated against a null, exponential model that predicts that relative growth rates of small aggregations are size independent. Growth rates for Zoanthus solanderi were consistent with this model. Z. sociatus, on the other hand, exhibited size—dependent relative growth rates. The smallest aggregations of this species had the higher relative growth rates, which were sufficiently high to more than compensate for losses due to mortality. These results are consistent with other life history and distributional differences between these two species. Zoanthus sociatus has a higher rate of mortality, does not undergo sexual reproduction until reaching a larger aggregation size, and commonly has a higher vertical distribution (which may represent a spatial refuge from subtidal predators) than does Z. solanderi. The comparatively rapid relative growth rates of small aggregations of Z. sociatus may be the result of spatial constraints on growth in large aggregations and/or of higher relative energy allocations to growth in small aggregations. The incorporation of fragmentation into the life history strategy of clonal organisms has a range of predicted consequences. Among some organisms, fragmentation and associated adaptations may be rare and of little consequence. Among organisms that frequently fragment as a result of physical disturbances, natural selection should favor repair and regenerative processes as well as resistance to this source of mortality. At the extreme, fragmentation need not be associated with death and injury. Adaptations at the developmental and physiological level may involve genetically programmed production of asexual fragments and size—dependent shifts in energy allocations to growth, sexual reproduction, and energy reserves. The degree of interdependence of the processes controlling the dynamics of genets and fragmented modules may well depend on the relative importance of such adaptations.
Effects of Patch Size on the Abundance of Sessile Marine Invertebrates
Authors: Keough Michael J.
Published: May 2006

The effects of patch size on the abundance of sessile invertebrates were investigated for two kinds of patchiness in a subtidal habitat in southern Australia: discrete pieces of substratum that were surrounded by water (isolated patches), and areas that were cleared within a background of other sessile organisms (nonisolated patches). They species composition of nonisolated patches following reoccupation was independent of patch size. Vegetative growth of organisms adjacent to the patches was the major means of reoccupation. Most larvae that recruited into the patches were overgrown, so that the species composition of the patches reflected the outcomes of interference competition among residents of patches. As a result, sponges and colonial tunicates were the most common taxa, with bryozoans and serpulid polychaetes being excluded. In contrast, the occupation of isolated patches was strongly size—dependent. On small substrata, species' abundances reflected their ability to colonize substrata by planktonic larvae, with few interactions among residents of patches. Bryozoans were the most abundant taxon, with a small number of patches containing tunicates, which have the potential to monopolize such patches. Larger substrata had a higher probability of being colonized by tunicates and sponges, in addition to bryozoans. Species compositions and abundances in these large patches were influenced most strongly by interference competition, rather than by recruitment. Bryozoans recruited preferentially onto small substrata (i.e., more recruits per square centimetre), while tunicate recruits occurred disproportionately on large substrata. Previously noted differences between the abundances of sessile invertebrate taxa on pier pilings and on the shells of the bivalve Pinna bicolor at Edithburgh can be ascribed to: (1) Differences in substratum size, which, when combined with the life histories of sessile invertebrates, result in variations in the relative importance of recruitment and interference competition for space. (2) Differential recruitment of bryozoans and tunicates that may be interpreted as evolved responses to patch—size—dependent rates of mortality (bryozoans) or size—dependent mean fitness (tunicates). (3) Predation by monacanthid fish, which reduces the incidence of tunicates (and thus potential competition) on Pinna shells and reduces the potential role of recruitment on pier pilings. (4) Differences between the total recruitment rates of some taxa on Pinna beds and beneath piers.
Nestling Survival and Growth in the Yellow‐Headed Blackbird, Xanthocephalus Xanthocephalus
Authors: Richter Wayne
Published: May 2006

I conducted a study on survival and growth of nestling Yellow—headed Blackbirds (Xanthocephalus xanthocephalus). I examined the following hypotheses on the nature of variation in clutch size among the individuals of a breeding population: (1) clutch size variation is maintained by reversing selection favoring different clutch sizes in different years, (2) clutch size variation reflects a trade—off between offspring number and quality, and (3) the clutch size laid by an individual is determined by its ability to rear offspring under prevailing conditions of physiology or territory. I found no influence of clutch size on either survival or growth in a poor year in which 41% of those birds hatching ultimately starved. These results argue against the first hypothesis, rule out of the second, and favor the third. Individual nests of this species show a high level of hatching asynchrony, with over one—third of the nests hatching no more than one offspring per day, and few ever having more than two hatchlings in a single day. By causing older birds to get a head start in growth, hatching asynchrony promotes efficient brood reduction of younger nestlings under conditions of food stress. At the same time, hatching order has no effect on the growth of those birds fledging, indicating that those birds not eliminated suffer no impairment due to their position in the brood. The extreme dependence of survival on hatching position, coupled to processes producing adequate growth of all fledging birds, is an adaptive response to breeding under conditions where weather may suddenly charge adversely. Yellow—headed Blackbirds show an ecological trade—off between those breeding habitats having a high likelihood of nest predation and favorable feeding conditions, and those that are relatively safe from predation but poor for provisioning the young.
Overcompensation in Response to Mammalian Herbivory: From Mutulastic to Antagonistic Interactions
Authors: Paige Ken N.
Published: May 2006

Studies of natural and simulated herbivory were conducted to assess the effects of secondary herbivory and plant association on the reproductive success of Ipomopsis aggregata. Over the 5—yr period of this study 77% of all plants were browsed by ungulate herbivores at some time during the flowering season. Of these, 33% were subsequently browsed. Removal of the single inflorescence stimulated the production of, on average, five new flowering stalks from dormant lateral buds along the remaining portion of the plant's stem. Although regrowth shoots were initially avoided by ungulates following the removal of scarlets gilia's single inflorenscence, plant types were secondarily browsed following stem elongation and flower bud formation. Secondary herbivory had no effect on the compensatory outcome. Plants that were naturally browsed produced significantly higher numbers of flowers and fruits than plants that were not eaten, even when plants were secondarily browsed. Because there were no significant differences in numbers of seeds produced per fruit or in seed mass, an increase in total fruits produced by browsed plants resulted in an increase in fitness through seed production. Observational and experimental results indicate that I. aggregata switches from a "mutualistic" to an "antagonistic" interaction with its ungulate herbivores in order to achieve its greatest fitness. Results of experimental clipping showed that high levels of secondary herbivory on I. aggregata would be detrimental, decreased fitness by °70%. An apparent change in plant quality following the initial bout of herbivory, however, deters high levels of subsequent herbivory, restricting tissue removal to the tips of the plant. When plants were found in close association with either pine or grasses (to add in the potential negative effects of competition), browsed plants still outperformed control plants, producing significantly more flowers and fruits than uneaten control plants. As in a previous study, these results support the contention that mammalian herbivores can benefit plants enhancing plant fitness.
The Impact of a Stream‐Dwelling Harpacticoid Copepod Upon Detritally Associated Bacteria
Authors: Perlmutter Daniel G. , Meyer Judy L.
Published: May 2006

Natural densities of common stream—dwelling harpacticoid copepods, Attheyella spp., reduced the density and biomass and increased the area—specific and cell—specific production of detritally associated bacteria. Bacterial density was reduced by as much as 58% and rod—shaped bacteria were reduced as much as 27%. Attheyella selectively removed larger rod—shaped bacteria. This resulted in a significant change in the size—frequency distribution of rod—shaped bacteria and a decrease in median cell length by 17—30%. The removal of larger sized cells by Attheyella probably contributed to the observed reduction in bacterial biomass. With copepods present, bacterial biomass was reduced as much as 45%. Estimated rates of ingestion of bacterial carbon by copepods are comparable to values for marine harpacticoids. Bacterial biomass appears to be a more important food source to microdetritivores than to macrodetritivores in streams.
Duration of Herbivore Removal and Environmental Stress Affect the Ectomycorrhizae of Pinyon Pines
Authors: Gehring Catherine A. , Whitham Thomas G.
Published: May 2006

The mutualistic mycorrhizal symbionts of plants have shown mixed responses to herbivory; they either decrease, increase, or show no measurable change. We examined the ectomycorrhizal responses of pinyon pine (Pinus edulis) exposed to 1 yr of simulated herbivory in two environments, one stressful and one less so. We also compared levels of ectomycorrhizal colonization and conelet production in pinyons form which an important insect herbivore had been removed for either 1 or 10 yr. Pinyons that grew in more stressful cinder soils experienced significant reductions (19%) in ectomycorrhizal colonization following 1 yr of simulated herbivory while pinyons growing in less stressful sandy loam soils did not. These results indicate that the degree of environmental stress experienced by a plant could affect whether mycorrhizal reductions result from herbivory. In addition the reductions in ectomycorrhizal colonization that resulted from chronic herbivory remained for a full year following herbivore removal even though conelet production increased 250—fold in the same time period. Our findings regarding the role of environmental stress and duration of herbivory in affecting mycorrhizal responses may help explain the variable responses found in other systems.
Are there Clumps in Body‐Size Distributions?
Authors: Manly Bryan F. J.
Published: May 2006

I examine the suggestion of Holling (1992) that distributions of body sizes for animals show clumps corresponding to basic biotic and abiotic processes operating at different scales in time and space. This is done by comparing the properties of observed sample distributions with what is obtained from computer—generated samples taken from distributions with different numbers of modes. A combination of kernel density estimation and smoothed bootstrap resampling provides a test for whether a distribution with k + 1 modes fits significantly better than a distribution with k modes. The analysis of three data sets discussed by Holling shows sample size distributions that are consistent with the hypothesis that the underlying distributions are unimodal or bimodal. A fourth data set has a sample distribution that seems unusual even for observations from a distribution with eight modes.
A Plant Pathogen Influences Pollinator Behavior and May Influence Reproduction of Nonhosts
Authors: Roy B. A.
Published: May 2006

Some plant pathogens attract pollinating insects and thus have the potential to influence the pollination of flowers, just as different flower species can influence one another's pollination. Showy, flower—like pseudoflowers caused by the rust fungus Puccinia monoica on Arabis holboellii (Brassicaceae) commonly co—occur with flowers of Anemone patens (Ranunculaceae). I evaluated the effects of pseudoflowers and anemone on each other's visitation, and the effect of pseudoflowers on the seed set of anemone. I expected that at low overall “flower” densities visitation would be facilitated in patches containing a mixture of these species. At low densities, pseudoflowers or flowers alone may be too rare to attract sufficient visitors, but the addition of the other species could make mixtures more attractive and thus increase visitation rates. At high densities I expected that “flower” in mixtures would compete for pollinators because it is more energy efficient for pollinators to concentrate visits on the most rewarding species. I used artificial arrays to separate the effects of “flower” density and relative frequency on visitation. Local density was not a good predictor of the influence of one species on the other. Instead, visitation patterns depended most strongly on the kind of visitor (flies vs. bees). Visitation to A. patens by flies was facilitated by the presence of pseudoflowers at both high and low densities, whereas visitation to pseudoflowers was not significantly influenced by A. patens at either density. Local density affected visitation by bees, but relative frequency did not. In addition to observing visitation, I also quantified the effects of interspecific movement of both pollen and spores on the reproductive success of A. patens. Although the presence of pseudoflowers sometimes facilitates visitation to A. patens, this effect could be counterbalanced by competition through interspecific insect movement: sticky pseudoflowers remove pollen from visiting insects, and fungal spermatia deposited on flower stigmas reduce seed set.
Empirical Bayes Estimation of Proportions with Application to Cowbird Parasitism Rates
Authors: Link William A. , Hahn D. Caldwell
Published: May 2006

Bayesian models provide a structure for studying collections of parameters such are considered in the investigation of communities, ecosystems, and landscapes. This structure allows for improved estimation of individual parameters by considering them in the context of a group of related parameters. Individual estimates are differntially adjusted toward in overall mean, with the magnitude of their adjustment based on their precision. Consequently, Bayesian estimation allows for a more reliable ranking of parameters and, in particular, a more credible identification of extreme values from a collection of estimates. In Bayesian models, individual parameters are regarded as values sampled from a specified probability distribution, called a prior. The requirements that the prior be known is often regarded as an unattractive feature of Bayesian analysis and may be the reason Bayesian analyses are not frequently applied in ecological studies. Empirical Bayes methods provide an alternative approach that incorporates the structural advantages of Bayesian models while requirng a less stringent specification of prior knowledge. Empirical Bayes methods require only that the prior be in a certain family of distributions, indexed by hyperparameters that can be estimated from the available data. This structur is of interest per se, in addition to its value in allowing for improved estimation of individual parameters; for example, hypothese regarding the existence of distinct subgroups in a collection of paramet ers can be considered under the empirical Bayes framework by allowing the hyperparameters to vary among subgroups. We describe the empirical Bayes approach in application to estimation of proportions, using data obtained in a community—wide study Brown—headed Cowbird paratism rates for illustration. Empirical Bayes estimates identify those species for which there is the greatest evidence of extreme parasitism rates. Subgroup analysis of our data on cowbird parasitism rates indicates that parasitisms rates for neotropical migrants as a group are no greater than those of resident/short—distance migrant in this forest community. Our data and analyses demonstrate that the parasitism rates for certain neotropical migrant species (Wood Thrush and Rose—breasted Grosbeak) are remarkably low while those for others (Ovenbird and Red—eyed Vireo) are remarkably high.
Two Songs with Accompaniment for an Elizabethan Choirboy Play
Authors: Sabol Andrew J.
Published: May 2006

Sophisticated song in the private theaters during the reign of Elizabeth—in contrast to the popular music characteristic of the public stage—implies at once compositions written especially for the drama, trained voices and instrumentalists to perform them, and a cultivated audience capable of appreciating the art of both composer and performer. In an often quoted description of a dramatic performance of the Children of the Chapel in 1602, a foreign visitor to London in the suite of Philipp Julius, Duke of Stettin-Pomerania, admired the skill of the boys as vocalists and instrumentahsts and called attention to the intensity of their training.
Grammar and Music in Thomas Campion's Observations in the Art of
English Poesie
Authors: Fenyo Jane K.
Published: May 2006

The problem presented by Thomas Campion's Observations in
the Art of English Poesie (London, 1602) has not yet been
satisfactorily solved. The question is: since Campion's
Ayres arouse unanimous praise for his
sensitive ear and metrical skill, how is it that his treatise on adapting
classical metrics to English verse evokes charges of an insensitive ear and
of phonetic inconsistency? Why does Campion seem to hear his ayres but not
all of his examples in Observations? The earlier
critics tend to blame his poor understanding of phonetic quantity in
Observations. He is accused of ‘hopeless
confusion’ and of having failed in the task he set himself. His’ system must
be wrong’ and his omission of needed examples shows ‘the apparently
irresistible spirit of perversity’. His work is cited as evidence that
‘shows how difficult it was to attain English (and therefore phonetic)
conception of quantity’.
Physiological Interactions Along Resource Gradients in a Tallgrass Prairie
Authors: Schimel David S. , Kittel Timothy G. F. , Knapp Alan K. , Seastedt Timothy R. , Parton William J. , Brown Virginia Bryan
Published: May 2006

Spatial variability in availability of resources that limit photosynthesis (water and N) leads to variation in rates of astmosphere—biosphere exchange. N content and allocation are canopy properties that link ecosystem, physiological, and biophysical processes and that vary in space at scale relevant to atmosphere—biosphere interaction. We studied landscape—scale variation in these and related canopy properties in Kansas Tallgrass prairie (USA). The tallgrass ecosystem was studied to this investigation because primary production in the prairie is constrained by N availability. This work was designed to aid in interpretation and spatial extrapolation of gas exchange measurements made using aerodynamic techniques as part of FIFE (First ISLSCP Field Experiments), a NASA—supported study. We collected data on spatial distribution of biomass, leaf area index (LAI), canopy N mass, N concentration ([N]), and gas exchange along topographic and management gradients. We also measured height distribution of N, light interception, and gas exchange within canopies as a function of position in the landscape. Substantial variation in biomass, LAI, N accumulation, and N allocation occurred over time, with topography, and as a result of previous burning. The vertical gradient of [N] and photosynthetic capacity within canopies were correlated, in space and time, with biomass and canopy light interception. The gradients were steeper in high biomass sites than in low biomass sites. in addition, proportional N allocation to the upper layer increased with time (12% in June, 32% in August) as biomass increased. As nutrient uptake increased within the tallgrass landscape, biomass increased and light limitation in the lower canopy was induced. As this light limitation increased with increasing biomass, or with accumulation of dead vegetation, allocation of N to the upper canopy increased. Height distribution of photosynthetic capacity paralleled within—canopy N allocation and light interception. As resource ratios (light, water, and nitrogen) varied in the landscape, so did rates of gas exchange. This work suggests that interactions between light extinction, N allocation, and photosynthesis that have been proposed for monospecific stands apply to the multispecies, but structurally simple, canopy of the tallgrass prairie. Models of plant performance based on evolutionary arguments may provide a powerful basis for spatial extrapolation of atmosphere—ecosystem exchange rates from sites to landscapes and larger regions.
Jean Barbot as a Source for the Slave Coast of West Africa
Authors: Law Robin
Published: May 2006

The author, who collects from others, is far from being exact.

John Barbot's Description of the Coasts of North and South Guinea, published in 1732 (and cited hereafter as 1732) is a text well known to historians of western Africa. The problems involved in its use as a historical source have been recognized for some time, and have been clarified in recent years primarily by the scholarship of Professor Paul Hair. The history of Barbot's text is, in general terms, now clear enough. John or, as he was originally called, Jean Barbot was a Frenchman who spent some time in the African trade, in the employment of the Compagnie du Sénégal. A Huguenot, he was obliged to leave France after the Revocation of the Edict of Nantes in 1685 and settled in England, where he died at Southampton in 1713. According to his own account (1732:381) Barbot made two voyages to Africa between 1678 and 1682. The manuscript journal of his first voyage, in 1678-79, is extant and has recently been published. That of his second voyage, in 1681-82, is not known to have survived. He subsequently wrote, in French, a general account of the western African coast under the title Description des Côtes d'Affrique, which he completed in 1688, but for which he was unable to find a publisher. This manuscript (hereafter cited as 1688) is also extant, and an English translation and critical edition of it is now in preparation, under the general editorship of Paul Hair. The 1688 Description was based partly on Barbot's own observations in 1678-82, but also drew extensively from earlier published accounts, especially from that of the Dutchman Dapper, published in 1668.
Fulfulde Literature in Arabic Script
Authors: Robinson David
Published: May 2006

Scholars of the West African savanna have long been familiar with the use of the Arabic alphabet to create cajami or “non-Arabic” literatures in Fulfulde and Hausa. Maurice Delafosse took a rather negative position on the value of this material, basing his opinion on two formidable obstacles: the absence of natural correspondence between a Semitic alphabet and non-Semitic phonemes and the difficulty of establishing a unified system of of conventions where such a natural correspondence was lacking. He argued that the ajamiyya manuscripts were few in number, poor in quality, and did not deserve the name of literature. By contrast, several more recent authors have stressed the importance and the continuing composition in ajamiyya: Gilbert Vieillard and Alfa Ibrahima Sow, in their work on the Fulfulde of Futa Jalon, Pierre Lacroix in his work on the Adamawa dialect of the same language, and Mervyn Hiskett in his studies in Hausa. Even where the volume of material is small, they have pointed to the critical pedagogical functions of ajamiyya for the spread of Islam.

In this paper I wish to show both the importance and the problems of exploiting Fulfulde literature in a somewhat different milieu, the jihad of al-hajj Umar of the mid-nineteenth century and the state which his son Amadu Sheku ran from Segu. To achieve this I will examine a narrative poem taken from the library and archives of Segu but housed since the 1890s at the Bibliothèque Nationale in Paris under the title Fonds Archinard. In the process I hope to draw attention to the historical circumstances in which the ajamiyya conventions for Fulfulde were developed and maintained in Futa Jalon and then extended to the Umarian entourage, and to the necessity for textual and contextual criticism of written documents based on an understanding of the close relationship between oral and written media and the continual revision that characterize a received tradition.
Can a Blind Man Really know an Elephant? Lessons on the Limitations of Oral Tradition from Paul Irwin's Liptako Speaks
Authors: Wright Donald R.
Published: May 2006

It was six men of IndostanTo learning much inclinedWho went to see the Elephant(Though all of them were blind),That each by observationMight satisfy his mind.

Over a thousand miles separate the Fulbe emirate of Liptako in Upper Volta from the region of the lower Gambia River, where several Mandinka states long held political authority. Fundamental differences between the areas are easy to notice. Besides speaking its own language and following its own set of social customs, Liptako's Fulbe population practiced a mixed pastoral and agrarian mode of subsistence on land where rainfall was only marginally sufficient. The Mandinka were more strictly farmers in an area that receives on average about twice as much rainfall as Liptako. Liptako existed as a unified Fulbe state only since the first decade of the nineteenth century, whereas many of the Mandinka states of the lower Gambia date to at least three centuries earlier. Commerce was important to both regions, but Liptako's commercial focus was toward the Sahara and the desert-side trade, whereas the lower Gambia was a point of contact between savanna merchants and Atlantic shippers. But, despite these obvious differences, there is a remarkable degree of similarity in the way individuals living in the two areas remember their past, and historians find a host of like problems they must confront when attempting to reconstruct the precolonial histories of either region.

I had become increasingly aware of some of the difficulties in working with Mandinka oral tradition during fieldwork in the lower Gambia. But only recently have I become familiar with problems another historian encountered as he studied traditions from Liptako, so many miles from my own area of interest. A Fulbe emirate, Liptako rose in the wake of Usuman dan Fodio's jihad early in the nineteenth century.
In the Wake of In the Wake of Columbus: Why the Polemic Over Columbus' First Landfall is of Interest to Africanist Historians
Authors: Henige David
Published: May 2006

It must be premised that the journal contains statements that appear to be absolutely irreconcilable with the present topography of the Bahamas.

Despite its disappointingly meager immediate results, its role as catalyst for the great age of worldwide culture contact inevitably resulted in a lively interest in every detail of Columbus' first voyage to the New World. Continuing unabated for nearly five centuries, the interest has assumed many forms, ranging from the putative effects of contact on the Amerindians to the identity of Columbus' first landfall--just where did the Old World first view the New World? Though it might seem to be both straightforward and of minor interest, the latter issue has in fact aroused great controversy for more than two centuries and remains far from settled today, as it appears that the most recent bid for consensus has been rudely shattered in its turn.

The controversy arises not at all from the fact that there exist several and contradictory independent testimonies bearing on the issue. Quite the contrary, as there is only a single surviving source, the so-called Diario de a bordo, which purports to be, at least in part, a record of Columbus' voyage on a day-by-day basis. The history of this text as we have it is complicated and this goes some way towards explaining why so many issues based on it remain moot. The only known extant copy was discovered as recently as 1790 and is in the handwriting of Bartolomé de las Casas, the noted missionary and historian of the early Indies, who was also a friend of several members of Columbus' family.
Traditions, Documents, and the Ife-Benin Relationship
Authors: Thornton John K.
Published: May 2006

Historians of Nigeria have been curious for many years about the relationship between the various states of the southern zone since the sixteenth century. The fact that the area has produced a rich art, has a fairly elaborate set of traditional histories, and has been the subject of some systematic archeological work means that the modern scholar has somewhat more to go on in reconstructing the region's history than just the fairly sparse and disappointing contemporary texts that came out of the early Portuguese contacts and subsequent European trade and navigation. But contemporary documentation for southern Nigeria remains much weaker than that for other African areas, such as the central African zone, Gold Coast, or the western Atlantic coast.

Nevertheless, documents have raised problems in understanding the history of the area that cannot be fully solved by recourse to the other sources of information, in spite of the comparative richness of non-documentary sources. One of these documentary problems is the issue of the Ife-Benin relationship as documentated in archeology, contemporary texts, and art history. The problems raised by the relationship between these two southern Nigerian cities ultimately reflects on a much larger set of questions concerning the relationship of all the early states south of the Niger, at a period quite near the origin of the state system that would predominate the rest of the pre-colonial period.