bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thiamine and Fatty Acid Content of Walleye Tissue from Three Southern U.S. Reservoirs
Authors: Honeyfield Dale C. , Vandergoot Christopher S. , Bettoli Phillip W. , Hinterkopf Joy P. , Zajicek James L. 
Published: June 2007

Abstract
We determined the thiamine concentration in egg, muscle, and liver tissues of walleyes Sander vitreus and the fatty acid content of walleye eggs from three southern U.S. reservoirs. In two Tennessee reservoirs (Dale Hollow and Center Hill), in which there were alewives Alosa pseudoharengus in the forage base, natural recruitment of walleyes was not occurring; by contrast in Lake James Reservoir, North Carolina, where there were no alewives, the walleye population was sustained via natural recruitment. Female walleye tissues were collected and assayed for thiamine (vitamin B1) and fatty acid content. Thiamine pyrophosphate was found to be the predominant form of thiamine in walleye eggs. In 2000, mean total egg thiamine concentrations were similar among Center Hill, Dale Hollow, and Lake James reservoirs (2.13, 3.14, and 2.77 nmol thiamine/g, respectively). Egg thiamine concentration increased as maternal muscle (r2 = 0.73) and liver (r2 = 0.68) thiamine concentration increased. Walleye egg thiamine does not appear to be connected to poor natural reproduction in Tennessee walleyes. Threadfin shad Dorosoma petenense, which are found in all three reservoirs, had higher thiaminase activity than alewives. Six fatty acids differed among the walleye eggs for the three reservoirs. Two were physiologically important fatty acids, arachidonic acid (20:4(n-6)) and docosahexaenoic acid (22:6(n-3)), which are important eicosanoid precursors involved in the regulation of biological functions, such as immune response and reproduction.
DETERMINANTS OF REPRODUCTIVE COSTS IN THE LONG‐LIVED BLACK‐LEGGED KITTIWAKE: A MULTIYEAR EXPERIMENT
Authors: Golet Gregory H. , Schmutz Joel A. , Irons David B. , Estes James A. 
Published: June 2007

We studied reproductive costs of Black‐legged Kittiwakes (Rissa tridactyla) in Prince William Sound, Alaska (USA) by removing entire clutches from randomly selected nests over four successive years, and then contrasting survival and fecundity of adults from manipulated and unmanipulated nests in each subsequent year. To elucidate mechanisms that lead to the expression of reproductive costs, we simultaneously characterized several behavioral and physiological parameters among adults in the two treatment groups. We also examined naturally nonbreeding adults that previously bred to determine their survival and future nonbreeding probabilities.Food availability varied during the study, being generally poor at the onset, and improving in later years. Adult nest attendance and body condition (assessed late in the chick‐ rearing period) varied accordingly among years, and between adults raising chicks and adults that had their eggs removed. Adults from unmanipulated nests incurred significant survival costs in all years, although fecundity costs were strongly expressed in only one of four years. Neither survival nor fecundity costs were strongly influenced by body condition or food availability, and no difference in reproductive costs was detected between the sexes. Although unmanipulated breeders survived at lower rates than manipulated breeders due to costs of reproduction, their survival rates were elevated compared to those of natural nonbreeders, presumably due to differences in individual ability. These findings indicate that models of adult survival must consider not only an organism's reproductive state, but also the factors that lead to that state.Although body condition appeared to be weakly related to survival, it was insufficient to explain the full magnitude of survival costs observed. We suggest that other parameters that were found to differ between treatment groups (e.g., rates of energy turnover, baseline levels of stress, and patterns of allocating body reserves) may be important mechanistic determinants of reproductive costs in kittiwakes, and potentially other long‐lived species. Future efforts should move beyond simple assessments of body condition and toward more integrated measures of physiological condition when attempting to identify factors that influence how long‐lived species balance the costs and benefits of reproduction.
BRIDGING THE GAP: INFLUENCE OF SEED DEPOSITION ON SEEDLING RECRUITMENT IN A PRIMATE–TREE INTERACTION
Authors: Balcomb Sophia R. , Chapman Colin A. 
Published: June 2007

Frugivores are thought to influence plant recruitment by creating initial seed deposition templates. However, post‐deposition processes (e.g., predation) may obscure these initial patterns. Few studies have examined successive life‐history stages of animal‐dispersed plants to evaluate how initial frugivore seed deposition influences early life stages of plant recruitment. We addressed this issue by quantifying seed removal and seedling recruitment of Monodora myristica (Annonaceae), a tropical, low‐fecundity, forest tree in Kibale National Park, Uganda. Fruit morphology suggests that this species is dispersed by only the largest arboreal frugivores. We determined which frugivores removed fruit during focal tree watches and quantified seed fate in experiments designed to mimic natural deposition. We estimated stage‐specific transition probabilities of survivorship to seedling establishment and determined expected seedling recruitment from each deposition condition. To evaluate spatial and temporal variation, these methods were conducted at two sites, 15 km apart, over two years. Finally, we compared frugivore abundance between sites to expected seedling and standing seedling, sapling, and pole abundances. We found that large‐bodied primates were critical for seed dispersal. They were the only frugivores that opened the hard‐husked fruits and were estimated to disperse >85% of mature seeds. Seeds placed away from parents had higher germination and establishment probabilities than those under parents, indicating that seed dispersal is advantageous. Single seeds away from parents (mimicking small‐bodied primate seed spitting) had the highest cumulative seedling recruitment probability. However, in three of four site‐by‐year combinations, 86–94% of estimated recruits came from seeds placed in clumps in dung (mimicking large‐bodied primates). High recruitment in the latter condition is due to the large number of seeds estimated to be deposited by large‐bodied primates. Despite this concordance, germination and establishment probabilities were highly variable between sites and years. Germination was a limiting step in recruitment, and high seed mortality from beetles and rodents indicates the importance of predation. The site with higher frugivorous primate abundance had higher standing seedling abundance, but lower expected seedling recruitment and lower sapling and pole abundances. Thus, even in a system where frugivores are critical for dispersal, spatial and temporal variation in post‐deposition processes reduces predictability of frugivore actions on seedling recruitment.Corresponding Editor: E. S. Menges
MULTIPLE TRAIT ASSOCIATIONS IN RELATION TO HABITAT DIFFERENTIATION AMONG 17 FLORIDIAN OAK SPECIES
Authors: Cavender-Bares Jeannine , Kitajima Kaoru , Bazzaz F. A. 
Published: June 2007

Differentiation of species distributions along environmental gradients and phenotypic specialization help explain the co‐presence of 17 oak species that might otherwise be expected to competitively exclude one another. In an effort to understand the role of niche differentiation in the co‐presence of these congeneric species in north‐central Florida, we examined the community structure of oak‐dominated forests in this region in relation to environmental variables and a suite of life history and physiological traits. Landscape distribution patterns of oaks and other woody species were determined from randomly established plots in three state parks. Soil moisture, nutrient availability, and fire regime were found to be critical factors influencing community structure, and the distribution of oak species was strongly correlated with these gradients. Detrended correspondence analysis of species' distributions supported the grouping of oak species into three major community types: (1) hammock, (2) sandhill, and (3) scrub. Principal components of multiple traits also supported differentiation of oak species into these three groups.There is clear evidence for ecological sorting among the oaks in these forests as species partition environmental gradients more than expected by chance, and most functional traits of species correspond to species distributions as predicted based on a priori understanding of trait function. Across phylogenetic lineages, species showed evolutionary convergence in function and habitat preference. In contrast, leaf‐level traits were conserved within phylogenetic lineages and were not well correlated with local habitat factors, but rather with the broader geographic distributions and northern range limits of species. The cumulative results reported here provide strong evidence that oak species specialize for particular niches via trade‐offs in functional traits, and such niche partitioning contributes to the high diversity of oak species at the landscape level. At smaller spatial scales, phylogenetic diversity among the oaks is likely to be important in promoting their coexistence through other mechanisms.
A NEIGHBORHOOD ANALYSIS OF TREE GROWTH AND SURVIVAL IN A HURRICANE‐DRIVEN TROPICAL FOREST
Authors: Uriarte María , Canham Charles D. , Thompson Jill , Zimmerman Jess K. 
Published: June 2007

We present a likelihood‐based regression method that was developed to analyze the effects of neighborhood competitive interactions and hurricane damage on tree growth and survival. The purpose of the method is to provide robust parameter estimates for a spatially explicit forest simulator and to gain insight into the processes that drive the patterns of species abundance in tropical forests. We test the method using census data from the 16‐ha Luquillo Forest Dynamics Plot in Puerto Rico and describe effects of the spatial configuration, sizes, and species of neighboring trees on the growth and survival of 12 dominant tree species representing a variety of life history strategies. Variation in size‐dependent growth and mortality suggests a complex relationship between size, growth, and survival under different regimes of light availability. Crowding effects on growth and survival appear to be idiosyncratic to each individual species, and with the exception of pioneers, there is little commonality among species that share similar life histories.We also explain the implications of differential susceptibility to hurricane damage on species' growth and survival and on their ability to respond to damage to neighboring trees. Tree species in the Luquillo Forest Dynamics Plot differ strikingly in both their susceptibility to hurricane disturbance and the nature of their recovery from wind disturbance, through response of both adult plants and juveniles to enhanced resource availability. At the stand level, intense competitive thinning of densely packed saplings that grew after hurricane damage accounted for the majority of post‐hurricane mortality, particularly for shade‐intolerant species. At the individual species level, effects of previous hurricane damage on growth and survival depended primarily on variation in the quantity and quality of hurricane damage sustained by target species and their interaction with life history characteristics of these individual species.Finally, we compare models that make different assumptions about the effects of competing species on tree growth and survival (e.g., equivalence of competitors vs. distinct species‐specific effects). Size effects alone could not account for growth and survival for the majority of target species. Our results also demonstrate that competing species have distinct per capita effects on growth of dominant target species. In contrast, we found moderate support for a model that assumed functional equivalence of competitors on survival.
SPECIES INTERACTION STRENGTH: TESTING MODEL PREDICTIONS ALONG AN UPWELLING GRADIENT
Authors: Menge Bruce A. , Blanchette Carol , Raimondi Pete , Freidenburg Tess , Gaines Steve , Lubchenco Jane , Lohse Dave , Hudson Greg , Foley Melissa , Pamplin Jacque 
Published: June 2007

A recent model predicts that species interactions in benthic marine communities vary predictably with upwelling regimes. To test this model, we studied thePisaster–Mytilusinteraction at 14 rocky intertidal sites distributed among three oceanographic regions along a 1300‐km stretch of the U.S. West Coast. Regions included an intermittent‐upwelling region (northern), a persistent‐upwelling region (central), and a region of weak and infrequent upwelling (southern). We quantified predation rates by the sea starPisaster ochraceuson its main preyMytilus californianusby transplanting mussels into the sea star's low‐zone foraging range and comparing the rate of mussel loss in +Pisasterplots to those in −Pisasterplots. To evaluate the relation between predation rates and key ecological processes and conditions, we quantified phytoplankton concentration and rates of mussel recruitment, mussel growth, mussel abundance, and sea star abundance.Predictions of the model are expressed as responses of predator and prey abundance, and species interaction strength (per capita and per population or total impact at the population level). As predicted by theory,per capitapredation rates were independent of upwelling regime, with no variation with region. Contrary to expectation however, per‐population predation rates were similar between intermittent‐ and persistent‐upwelling regions but were greater under strong upwelling than under weak upwelling conditions. The greatest variation inper‐populationpredation rates was at the level of site within region. Also contrary to theory, average abundances of prey (mussel cover) and predators (sea stars) were similar among oceanographic regions and varied mostly at the site level.As expected from theory, predation rate was high where sea star density was high, a condition that often coincided with a high food supply (phytoplankton) for filter feeders, including larvae, and high recruitment. With the exception of two sites having dense sea star populations and thus high predation, low values of either or both were associated with low predation, suggesting that the supply of prey often depended on conditions that favored subsidies of both phytoplankton and new larvae to prey populations. The occurrence of high predator density and high predation at sites of low inputs of particulate food and propagules suggests that understanding sea star life history is a key to a fuller understanding of variation in predation on a coastal scale. Evidence suggests that often sporadic recruitment of sea stars along the coast is balanced by great longevity, which tends to even out predation impact on coastal intertidal communities.
SEAWEEDS UNDER STRESS: MANIPULATED STRESS AND HERBIVORY AFFECT CRITICAL LIFE‐HISTORY FUNCTIONS
Authors: Dethier Megan N. , Williams Susan L. , Freeman Aaren 
Published: June 2007

Terrestrial plants respond in complex ways to the interaction of stress and herbivory, but much less is known about responses of seaweeds. We studied the common intertidal rockweed Fucus gardneri to determine how stress and herbivory interact to influence its survival, growth, reproduction, and the concentration of phlorotannins, which can deter herbivory and constitute substantial mass. We manipulated stress and herbivory both in the field and in outdoor mesocosms over 2–4 months during spring and summer. In the field, disruptive stress was reduced in the upper range of the seaweed's distribution with awnings made of screen. Temperatures and relative humidities were more extreme in the no‐awnings locations. This treatment was crossed with a limpet‐removal treatment. In mesocosms, the tidal period was controlled so that half of the experimental thalli were exposed to air daily for 3–4 hours longer (greater limitation stress) than the other half, and three levels of isopod grazing were maintained. Grazing intensity was effectively reduced in the field and increased in the mesocosms. Net rates of photosynthesis were used as independent measures of seaweed stress.Fucus gardneri in the locations without awnings exhibited significant reductions in net photosynthesis, survival, and final size compared to thalli under awnings. The mesocosm environment was more benign; all individuals survived longer and grew larger. However, results from both experiments were generally consistent. Stress resulted in slightly lower growth and substantially reduced phlorotannin mass. Severe stress had a negative effect on reproductive output in the field experiment, but mild stress had a small positive effect in the mesocosms. Herbivory resulted in reduced thallus mass, slightly reduced growth, and reduced reproduction, but it had no effect on phlorotannin levels in either experiment. Herbivory and stress thus influenced different performance indicators in Fucus. Stress had more dramatic effects on phlorotannins than it did on growth, whereas herbivory more strongly influenced growth and reproduction. Few interactive effects were found, unlike in many terrestrial studies. If stress and herbivory act largely independently, as they appear to do here and in the limited number of other seaweed studies, predicting the effects of changes in the intertidal physical environment and in herbivory might be simpler than anticipated. The physiological basis for the observed responses to stress and herbivory is suspected to involve trade‐offs in resource allocation among these key life‐history parameters.
QUANTIFYING SPATIAL PATTERN WITH EVENNESS INDICES
Authors: Payne Laura X. , Schindler Daniel E. , Parrish Julia K. , Temple Stanley A. 
Published: June 2007

Quantifying the spatial distributions of organisms in simple and meaningful ways is important for understanding the ecology and habitat needs of species subject to anthropogenic disturbances. Most multi‐species conservation and management programs do not yet account for the variation of space‐use patterns exhibited by species preferring the same habitat type. To measure species' space‐use patterns as a step toward determining habitat needs, we suggest using evenness indices. Although commonly used in characterizing communities (i.e., as a measure of species diversity), these indices are suitable for characterizing many other ecological patterns, including patterns of site use by individuals.We investigate the statistical properties of five indices (Camargo's index of evenness, E′; Simpson's index of evenness, E1/D^; Lloyd's index of mean crowding, J; Smith‐Wilson index Evar; and Dispersion index, DL, a variant of the Shannon diversity index) to evaluate their utility for quantifying broad‐scale spatial patterns of migratory shorebirds. We use a Monte Carlo simulation approach to compare these indices for their (1) ability to characterize a wide range of spatial patterns (from even to patchy); (2) ability to discriminate among distributions; and (3) robustness to incomplete sampling. In addition, we compare the ability of these indices to characterize spatial dispersion for four species of shorebirds migrating through the United States: Killdeer (Charadrius vociferus), Semipalmated Plover (C. semipalmatus), Sanderling (Calidris alba), and Red Knot (C. canutus).Overall, we recommend Camargo, Simpson, and Lloyd indices for quantifying spatial dispersion. All three indices gave precise and unbiased estimates once 35 or more sites (3.5% of 1000 simulated sites) were sampled randomly, regardless of the degree of patchiness. Nonrandom sampling resulted in biased estimates until a much greater proportion of sites (at least 30–50%) were sampled, highlighting the importance of site selection in sampling programs. Our analysis of shorebird spatial patterns revealed that evenness indices discriminate well among the species we considered, ranking Killdeer as most dispersed and Red Knot as most aggregated. Our results agree with earlier (independent) assessments of these species' migration strategies and illustrate how simple univariate metrics may be useful tools for characterizing complex spatial patterns.
GENETICALLY ENGINEERED ORGANISMS AND THE ENVIRONMENT: CURRENT STATUS AND RECOMMENDATIONS1
Authors: Snow A. A. , Andow D. A. , Gepts P. , Hallerman E. M. , Power A. , Tiedje J. M. , Wolfenbarger L. L. 
Published: June 2007

The Ecological Society of America has evaluated the ecological effects of current and potential uses of field‐released genetically engineered organisms (GEOs), as described in this Position Paper. Some GEOs could play a positive role in sustainable agriculture, forestry, aquaculture, bioremediation, and environmental management, both in developed and developing countries. However, deliberate or inadvertent releases of GEOs into the environment could have negative ecological effects under certain circumstances.Possible risks of GEOs could include: (1) creating new or more vigorous pests and pathogens; (2) exacerbating the effects of existing pests through hybridization with related transgenic organisms; (3) harm to nontarget species, such as soil organisms, non‐pest insects, birds, and other animals; (4) disruption of biotic communities, including agroecosystems; and (5) irreparable loss or changes in species diversity or genetic diversity within species. Many potential applications of genetic engineering extend beyond traditional breeding, encompassing viruses, bacteria, algae, fungi, grasses, trees, insects, fish, and shellfish. GEOs that present novel traits will need special scrutiny with regard to their environmental effects.The Ecological Society of America supports the following recommendations. (1) GEOs should be designed to reduce environmental risks. (2) More extensive studies of the environmental benefits and risks associated with GEOs are needed. (3) These effects should be evaluated relative to appropriate baseline scenarios. (4) Environmental release of GEOs should be prevented if scientific knowledge about possible risks is clearly inadequate. (5) In some cases, post‐release monitoring will be needed to identify, manage, and mitigate environmental risks. (6) Science‐based regulation should subject all transgenic organisms to a similar risk assessment framework and should incorporate a cautious approach, recognizing that many environmental effects are GEO‐ and site‐specific. (7) Ecologists, agricultural scientists, molecular biologists, and others need broader training and wider collaboration to address these recommendations.In summary, GEOs should be evaluated and used within the context of a scientifically based regulatory policy that encourages innovation without compromising sound environmental management. The Ecological Society of America is committed to providing scientific expertise for evaluating and predicting the ecological effects of field‐released transgenic organisms.