bluuebunny/crossref_metadata_2025 huggingface dataset:
Induced responses to competition and herbivory: natural selection on multi‐trait phenotypic plasticity
Authors: Boege Karina
Published: June 2010

Herbivory and competition are two of the most common biotic stressors for plants. When occurring simultaneously, responses to one interaction can constrain the induction of responses to the other interaction due to resource limitation and other interactive effects. Thus, to maximize fitness when interacting with competitors and herbivores, plants are likely to express particular combinations of plastic responses. This study reports the interactive effects of herbivory and competition on responses induced in Tithonia tubaeformis plants and describes how natural selection acts on particular plastic responses and on their different combinations. Competition induced a stem elongation response, expressed through an increase in height and mean internode length, together with a decrease in basal diameter. Interestingly, realized resistance increased in both competition and herbivory treatments, suggesting a plastic response in both constitutive and induced resistance traits. Particular combinations of plastic responses defined three plant phenotypes: vigorous, elongated, and resistant plants. The ecological context in which plants grew modified the traits and the particular combinations of plastic responses that were favored by selection. Vigorous plants were favored by selection in all environments, except when they were damaged by herbivores in the absence of neighbors. The combination of responses defining an elongated plant phenotype was favored by selection in crowded conditions. Resistance was negatively selected in the absence of competition and herbivory but favored in the presence of both interactions. In addition, contextual analyses detected that population structure in heterogeneous environments can also influence the outcomes of selection. These findings suggest that natural selection can act on particular combinations of plastic responses, which may allow plants to adjust their phenotypes to those that promote greater fitness under particular ecological conditions.
Global contribution of echinoderms to the marine carbon cycle: CaCO3 budget and benthic compartments
Authors: Lebrato Mario , Iglesias-Rodríguez Debora , Feely Richard A. , Greeley Dana , Jones Daniel O. B. , Suarez-Bosche Nadia , Lampitt Richard S. , Cartes Joan E. , Green Darryl R. H. , Alker Belinda
Published: June 2010

The contribution of carbonate‐producing benthic organisms to the global marine carbon budget has been overlooked, the prevailing view being that calcium carbonate (CaCO3) is predominantly produced and exported by marine plankton in the “biological pump.” Here, we provide the first estimation of the global contribution of echinoderms to the marine inorganic and organic carbon cycle, based on organism‐level measurements from species of the five echinoderm classes. Echinoderms' global CaCO3 contribution amounts to ~0.861 Pg CaCO3/yr (0.102 Pg C/yr of inorganic carbon) as a production rate, and ~2.11 Pg CaCO3 (0.25 Pg C of inorganic carbon) as a standing stock from the shelves, slopes, and abyssal depths. Echinoderm inorganic carbon production (0.102 Pg C/yr) is less than the global pelagic production (0.4–1.8 Pg C/yr) and similar to the estimates for carbonate shelves globally (0.024–0.120 Pg C/yr). Echinoderm CaCO3 production per unit area is ~27.01 g CaCO3·m−2·yr−1 (3.24 g C·m−2·yr−1 as inorganic carbon) on a global scale for all areas, with a standing stock of ~63.34 g CaCO3/m2 (7.60 g C/m2 as inorganic carbon), and ~7.97 g C/m2 as organic carbon. The shelf production alone is 77.91 g CaCO3·m−2·yr−1 (9.35 g C·m−2·yr−1 as inorganic carbon) in contrast to 2.05 g CaCO3·m−2·yr−1 (0.24 g C·m−2·yr−1 as inorganic carbon) for the slope on a global scale. The biogeography of the CaCO3 standing stocks of echinoderms showed strong latitudinal variability. More than 80% of the global CaCO3 production from echinoderms occurs between 0 and 800 m, with the highest contribution attributed to the shelf and upper slope. We provide a global distribution of echinoderm populations in the context of global calcite saturation horizons, since undersaturated waters with respect to mineral phases are surfacing. This shallowing is a direct consequence of ocean acidification, and in some places it may reach the shelf and upper slope permanently, where the highest CaCO3 standing stocks from echinoderms originate. These organism‐level data contribute substantially to the assessment of global carbonate inventories, which at present are poorly estimated. Additionally, it is desirable to include these benthic compartments in coupled global biogeochemical models representing the “biological pump” and its feedbacks, since at present all efforts have focused on pelagic processes, dominated by coccolithophores. The omission of the benthic processes from modeling will only diminish the understanding of elemental fluxes at large scales and any future prediction of climate change scenarios.
Associations of plant fitness, leaf chemistry, and damage suggest selection mosaic in plant–herbivore interactions
Authors: Muola Anne , Mutikainen Pia , Lilley Marianna , Laukkanen Liisa , Salminen Juha-Pekka , Leimu Roosa
Published: June 2010

The geographic mosaic theory of coevolution states that variation in species interactions forms the raw material for coevolutionary processes, which take place over large geographic scales. One key assumption underlying the process of coevolution in plant–herbivore interactions is that herbivores exert selection on their host plants and that this selection varies among plant populations. We examined spatial variation in the existence and strength of phenotypic selection on host plant resistance exerted by specialist herbivores in 17 archipelago populations of the perennial herbVincetoxicum hirundinaria(Asclepiadaceae). In these highly fragmented populations,V. hirundinariais consumed by the larvae of two specialist herbivores: the folivorous mothAbrostola asclepiadisand the seed predatorEuphranta connexa. Selection imposed on host plants by these herbivores was examined by analyzing the associations between levels of herbivory, plant fitness, and contents of a number of leaf chemicals reflecting plant resistance to and quality for the herbivores. We found extensive spatial variation in the levels of herbivory and in plant fitness. More importantly, the impact of both leaf herbivory and seed predation on plant fitness varied among plant populations, indicating spatial variation in phenotypic selection. In addition, leaf chemistry varied widely among plant populations, reflecting spatial variation in plant quality as food for the herbivores. However, leaf compounds influenced folivory similarly in all the studied plant populations, and interestingly, some of the compounds were associated with the intensity of seed predation. Finally, some of the leaf compounds were associated with plant fitness, and the strength and direction of these associations varied among plant populations. The observed spatial variation in the strength of the interactions betweenV. hirundinariaand its specialist herbivores suggests a geographic selection mosaic. Because the occurrence and strength of spatial variation varied between the two specialist herbivores, our results highlight the importance of considering multiple enemies when trying to understand evolution of interactions between plants and their herbivores.
A statistical approach for estimating fish diet compositions from multiple data sources: Gulf of California case study
Authors: Ainsworth Cameron H. , Kaplan Isaac C. , Levin Phillip S. , Mangel Marc
Published: June 2010

Trophic ecosystem models are one promising tool for providing ecosystem‐based management advice. Diet and interaction rate parameters are critical in defining the behavior of these models, and will greatly influence any predictions made in response to management perturbations. However, most trophic ecosystem models must rely on a patchwork of data availability and must contend with knowledge gaps and poor quantification of uncertainty. Here we present a statistical method for combining diet information from field samples and literature to describe trophic relationships at the level of functional groups. In this example, original fieldwork in the northern Gulf of California, Mexico, provides gut content data for targeted and untargeted fish species. The field data are pooled with diet composition information from FishBase, an online data repository. Diet information is averaged across stomachs to represent an average predator, and then the data are bootstrapped to generate likelihood profiles. These are fit to a Dirichlet function, and from the resulting marginal distributions, maximum‐likelihood estimates are generated with confidence intervals representing the likely contribution to diet for each predator–prey combination. We characterize trophic linkages into two broad feeding guilds, pelagic and demersal feeders, and explore differentiation within those guilds. We present an abbreviated food web for the northern Gulf of California based on the results of this study. This food web will form the basis of a trophic dynamic model. Compared to the common method of averaging diet compositions across predators, this statistical approach is less influenced by the presence of long tails in the distributions, which correspond to rare feeding events, and is therefore better suited to small data sets.
Nitrogen and phosphorus additions negatively affect tree species diversity in tropical forest regrowth trajectories
Authors: Siddique Ilyas , Vieira Ima Célia Guimarães , Schmidt Susanne , Lamb David , Carvalho Cláudio José Reis , Figueiredo Ricardo de Oliveira , Blomberg Simon , Davidson Eric A.
Published: June 2010

Nutrient enrichment is increasingly affecting many tropical ecosystems, but there is no information on how this affects tree biodiversity. To examine dynamics in vegetation structure and tree species biomass and diversity, we annually remeasured tree species before and for six years after repeated additions of nitrogen (N) and phosphorus (P) in permanent plots of abandoned pasture in Amazonia. Nitrogen and, to a lesser extent, phosphorus addition shifted growth among woody species. Nitrogen stimulated growth of two common pioneer tree species and one common tree species adaptable to both high‐ and low‐light environments, while P stimulated growth only of the dominant pioneer tree Rollinia exsucca (Annonaceae). Overall, N or P addition reduced tree assemblage evenness and delayed tree species accrual over time, likely due to competitive monopolization of other resources by the few tree species responding to nutrient enrichment with enhanced establishment and/or growth rates. Absolute tree growth rates were elevated for two years after nutrient addition. However, nutrient‐induced shifts in relative tree species growth and reduced assemblage evenness persisted for more than three years after nutrient addition, favoring two nutrient‐responsive pioneers and one early‐secondary tree species. Surprisingly, N + P effects on tree biomass and species diversity were consistently weaker than N‐only and P‐only effects, because grass biomass increased dramatically in response to N + P addition. The resulting intensified competition probably prevented an expected positive N + P synergy in the tree assemblage. Thus, N or P enrichment may favor unknown tree functional response types, reduce the diversity of coexisting species, and delay species accrual during structurally and functionally complex tropical rainforest secondary succession.
Aridity and grazing as convergent selective forces: an experiment with an Arid Chaco bunchgrass
Authors: Quiroga R. Emiliano , Golluscio Rodolfo A. , Blanco Lisandro J. , Fernández Roberto J.
Published: June 2010

It has been proposed that aridity and grazing are convergent selective forces: each one selects for traits conferring resistance to both. However, this conceptual model has not yet been experimentally validated. The aim of this work was to experimentally evaluate the effect of aridity and grazing, as selective forces, on drought and grazing resistance of populations of Trichloris crinita, a native perennial forage grass of the Argentinean Arid Chaco region. We collected seeds in sites with four different combinations of aridity and grazing history (semiarid/subhumid × heavily grazed/lightly grazed), established them in pots in a common garden, and subjected the resulting plants to different combinations of drought and defoliation. Our results agreed with the convergence model. Aridity has selected T. crinita genotypes that respond better to drought and defoliation in terms of sexual reproduction and leaf growth, and that can evade grazing due to a lower shoot : root ratio and a higher resource allocation to reserves (starch) in stem bases. Similarly, grazing has selected genotypes that respond better to drought and defoliation in terms of sexual reproduction and that can evade grazing due to a lower digestibility of leaf blades. These results allow us to extend concepts of previous models in plant adaptation to herbivory to models on plant adaptation to drought. The only variable in which we obtained a result opposite to predictions was plant height, as plants from semiarid sites were taller (and with more erect tillers) than plants from subhumid sites; we hypothesize that this result might have been a consequence of the selection exerted by the high solar radiation and soil temperatures of semiarid sites. In addition, our work allows for the prediction of the effects of dry or wet growing seasons on the performance of T. crinita plants. Our results suggest that we can rely on dry environments for selecting grazing‐resistant genotypes and on high grazing pressure history environments for selecting drought‐resistant ones.
Active adaptive conservation of threatened species in the face of uncertainty
Authors: McDonald-Madden Eve , Probert William J. M. , Hauser Cindy E. , Runge Michael C. , Possingham Hugh P. , Jones Menna E. , Moore Joslin L. , Rout Tracy M. , Vesk Peter A. , Wintle Brendan A.
Published: June 2010

Adaptive management has a long history in the natural resource management literature, but despite this, few practitioners have developed adaptive strategies to conserve threatened species. Active adaptive management provides a framework for valuing learning by measuring the degree to which it improves long‐run management outcomes. The challenge of an active adaptive approach is to find the correct balance between gaining knowledge to improve management in the future and achieving the best short‐term outcome based on current knowledge. We develop and analyze a framework for active adaptive management of a threatened species. Our case study concerns a novel facial tumor disease affecting the Australian threatened species Sarcophilus harrisii: the Tasmanian devil. We use stochastic dynamic programming with Bayesian updating to identify the management strategy that maximizes the Tasmanian devil population growth rate, taking into account improvements to management through learning to better understand disease latency and the relative effectiveness of three competing management options. Exactly which management action we choose each year is driven by the credibility of competing hypotheses about disease latency and by the population growth rate predicted by each hypothesis under the competing management actions. We discover that the optimal combination of management actions depends on the number of sites available and the time remaining to implement management. Our approach to active adaptive management provides a framework to identify the optimal amount of effort to invest in learning to achieve long‐run conservation objectives.
Functional diversity in resource use by fungi
Authors: McGuire Krista L. , Bent Elizabeth , Borneman James , Majumder Arundhati , Allison Steven D. , Treseder Kathleen K.
Published: June 2010

Fungi influence nutrient cycling in terrestrial ecosystems, as they are major regulators of decomposition and soil respiration. However, little is known about the substrate preferences of individual fungal species outside of laboratory culture studies. If active fungi differ in their substrate preferences in situ, then changes in fungal diversity due to global change may dramatically influence nutrient cycling in ecosystems. To test the responses of individual fungal taxa to specific substrates, we used a nucleotide‐analogue procedure in the boreal forest of Alaska (USA). Specifically, we added four organic N compounds commonly found in plant litter (arginine, glutamate, lignocellulose, and tannin–protein) to litterbags filled with decomposed leaf litter (black spruce and aspen) and assessed the responses of active fungal species using qPCR (quantitative polymerase chain reaction), oligonucleotide fingerprinting of rRNA genes, and sequencing. We also compared the sequences from our experiment with a concurrent warming experiment to see if active fungi that targeted more recalcitrant compounds would respond more positively to soil warming. We found that individual fungal taxa responded differently to substrate additions and that active fungal communities were different across litter types (spruce vs. aspen). Active fungi that targeted lignocellulose also responded positively to experimental warming. Additionally, resource‐use patterns in different fungal taxa were genetically correlated, suggesting that it may be possible to predict the ecological function of active fungal communities based on genetic information. Together, these results imply that fungi are functionally diverse and that reductions in fungal diversity may have consequences for ecosystem functioning.
Comparing ecosystem engineering efficiency of two plant species with contrasting growth strategies
Authors: Bouma T. J. , Vries M. B. De , Herman P. M. J.
Published: June 2010

Many ecosystems are greatly affected by ecosystem engineering, such as coastal salt marshes, where macrophytes trap sediment by reducing hydrodynamic energy. Nevertheless, little is known about the costs and benefits that are imposed on engineering species by the traits that underlie their ecosystem engineering capacity. We addressed this topic by comparing ecosystem engineering efficiency defined as the benefit–cost ratio per unit of biomass investment for two species from the intertidal habitat: the stiff grass Spartina anglica and the flexible grass Puccinellia maritima. These species were selected for their ability to modify their habitat by trapping large quantities of sediment despite their contrasting growth form. On a biomass basis, dissipation of hydrodynamic energy from waves (a proxy for benefits associated with ecosystem engineering capability as it relates to the sediment trapping capability) was strikingly similar for both salt marsh species, indicating that both species are equally effective in modifying their habitat. The drag forces per unit biomass (a proxy for costs associated with ecosystem engineering ability as it relates to the requirements on tissue construction and shoot anchoring to prevent breaking and/or washing away) were slightly higher in the species with flexible shoots. As a result, stiff Spartina vegetation had slightly higher ecosystem engineering efficiency, due to lower engineering costs rather than to a higher engineering effect. Thus, Spartina is a slightly more efficient rather than a more effective ecosystem engineer. Ecosystem engineering efficiency was found to be a species‐specific characteristic, independent of vegetation density and relatively constant in space. Analyzing ecosystem engineering by quantifying trade‐offs offers a useful way toward developing a better understanding of different engineering strategies.
Looking deeper into the soil: biophysical controls and seasonal lags of soil CO2production and efflux
Authors: Vargas Rodrigo , Baldocchi Dennis D. , Allen Michael F. , Bahn Michael , Black T. Andrew , Collins Scott L. , Yuste Jorge Curiel , Hirano Takashi , Jassal Rachhpal S. , Pumpanen Jukka , Tang Jianwu
Published: June 2010

We seek to understand how biophysical factors such as soil temperature (Ts), soil moisture (θ), and gross primary production (GPP) influence CO2fluxes across terrestrial ecosystems. Recent advancements in automated measurements and remote‐sensing approaches have provided time series in which lags and relationships among variables can be explored. The purpose of this study is to present new applications of continuous measurements of soil CO2efflux (F0) and soil CO2concentrations measurements. Here we explore how variation inTs, θ, and GPP (derived from NASA's moderate‐resolution imaging spectroradiometer [MODIS]) influenceF0and soil CO2production (Ps). We focused on seasonal variation and used continuous measurements at a daily timescale across four vegetation types at 13 study sites to quantify: (1) differences in seasonal lags between soil CO2fluxes andTs, θ, and GPP and (2) interactions and relationships between CO2fluxes withTs, θ, and GPP. Mean annualTsdid not explain annualF0andPsamong vegetation types, but GPP explained 73% and 30% of the variation, respectively. We found evidence that lags between soil CO2fluxes andTsor GPP provide insights into the role of plant phenology and information relevant about possible timing of controls of autotrophic and heterotrophic processes. The influences of biophysical factors that regulate dailyF0andPsare different among vegetation types, but GPP is a dominant variable for explaining soil CO2fluxes. The emergence of long‐term automated soil CO2flux measurement networks provides a unique opportunity for extended investigations intoF0andPsprocesses in the near future.
Revealing ecological networks using Bayesian network inference algorithms
Authors: Milns Isobel , Beale Colin M. , Smith V. Anne
Published: June 2010

Understanding functional relationships within ecological networks can help reveal keys to ecosystem stability or fragility. Revealing these relationships is complicated by the difficulties of isolating variables or performing experimental manipulations within a natural ecosystem, and thus inferences are often made by matching models to observational data. Such models, however, require assumptions—or detailed measurements—of parameters such as birth and death rate, encounter frequency, territorial exclusion, and predation success. Here, we evaluate the use of a Bayesian network inference algorithm, which can reveal ecological networks based upon species and habitat abundance alone. We test the algorithm's performance and applicability on observational data of avian communities and habitat in the Peak District National Park, United Kingdom. The resulting networks correctly reveal known relationships among habitat types and known interspecific relationships. In addition, the networks produced novel insights into ecosystem structure and identified key species with high connectivity. Thus, Bayesian networks show potential for becoming a valuable tool in ecosystem analysis.
Loss of foundation species increases population growth of exotic forbs in sagebrush steppe
Authors: Prevéy Janet S. , Germino Matthew J. , Huntly Nancy J.
Published: June 2010

The invasion and spread of exotic plants following land disturbance threatens semiarid ecosystems. In sagebrush steppe, soil water is scarce and is partitioned between deep‐rooted perennial shrubs and shallower‐rooted native forbs and grasses. Disturbances commonly remove shrubs, leaving grass‐dominated communities, and may allow for the exploitation of water resources by the many species of invasive, tap‐rooted forbs that are increasingly successful in this habitat. We hypothesized that exotic forb populations would benefit from increased soil water made available by removal of sagebrush, a foundation species capable of deep‐rooting, in semiarid shrub‐steppe ecosystems. To test this hypothesis, we used periodic matrix models to examine effects of experimental manipulations of soil water on population growth of two exotic forb species, Tragopogon dubius and Lactuca serriola, in sagebrush steppe of southern Idaho, USA. We used elasticity analyses to examine which stages in the life cycle of T. dubius and L. serriola had the largest relative influence on population growth. We studied the demography of T. dubius and L. serriola in three treatments: (1) control, in which vegetation was not disturbed, (2) shrubs removed, or (3) shrubs removed but winter–spring recharge of deep‐soil water blocked by rainout shelters. The short‐term population growth rate (λ) of T. dubius in the shrub‐removal treatment was more than double that of T. dubius in either sheltered or control treatments, both of which had limited soil water. All L. serriola individuals that emerged in undisturbed sagebrush plots died, whereas λ of L. serriola was high (λ > 2.5) in all shrub‐removal plots, whether they had rainout shelters or not. Population growth of both forbs in all treatments was most responsive to flowering and seed production, which are life stages that should be particularly reliant on deep‐soil water, as well as seedling establishment, which is important to most plant populations, especially during invasion. These data indicate the importance of native species, in this case the dominant shrub, in influencing soil resources and restricting population growth of exotic plants. These results argue that management of invasive plants should focus not only on removal of nonnatives, but also on reestablishment of important native species.
POC plots: calibrating species distribution models with presence‐only data
Authors: Phillips Steven J. , Elith Jane
Published: June 2010

Statistical models are widely used for predicting species' geographic distributions and for analyzing species' responses to climatic and other predictor variables. Their predictive performance can be characterized in two complementary ways: discrimination, the ability to distinguish between occupied and unoccupied sites, and calibration, the extent to which a model correctly predicts conditional probability of presence. The most common measures of model performance, such as the area under the receiver operating characteristic curve (AUC), measure only discrimination. In contrast, we introduce a new tool for measuring model calibration: the presence‐only calibration plot, or POC plot. This tool relies on presence‐only evaluation data, which are more widely available than presence–absence evaluation data, to determine whether predictions are proportional to conditional probability of presence. We generalize the predicted/expected curves of Hirzel et al. to produce a presence‐only analogue of traditional (presence–absence) calibration curves. POC plots facilitate visual exploration of model calibration, and can be used to recalibrate badly calibrated models. We demonstrate their use by recalibrating models made by the DOMAIN modeling method on a comprehensive set of 226 species from six regions of the world, significantly improving DOMAIN's predictive performance.
Simulating greenhouse gas budgets of four California cropping systems under conventional and alternative management
Authors: Gryze Steven De , Wolf Adam , Kaffka Stephen R. , Mitchell Jeff , Rolston Dennis E. , Temple Steven R. , Lee Juhwan , Six Johan
Published: June 2010

Despite the importance of agriculture in California's Central Valley, the potential of alternative management practices to reduce soil greenhouse gas (GHG) emissions has been poorly studied in California. This study aims at (1) calibrating and validating DAYCENT, an ecosystem model, for conventional and alternative cropping systems in California's Central Valley, (2) estimating CO2, N2O, and CH4 soil fluxes from these systems, and (3) quantifying the uncertainty around model predictions induced by variability in the input data. The alternative practices considered were cover cropping, organic practices, and conservation tillage. These practices were compared with conventional agricultural management. The crops considered were beans, corn, cotton, safflower, sunflower, tomato, and wheat. Four field sites, for which at least five years of measured data were available, were used to calibrate and validate the DAYCENT model. The model was able to predict 86–94% of the measured variation in crop yields and 69–87% of the measured variation in soil organic carbon (SOC) contents. A Monte Carlo analysis showed that the predicted variability of SOC contents, crop yields, and N2O fluxes was generally smaller than the measured variability of these parameters, in particular for N2O fluxes. Conservation tillage had the smallest potential to reduce GHG emissions among the alternative practices evaluated, with a significant reduction of the net soil GHG fluxes in two of the three sites of 336 ± 47 and 550 ± 123 kg CO2‐eq·ha−1·yr−1 (mean ± SE). Cover cropping had a larger potential, with net soil GHG flux reductions of 752 ± 10, 1072 ± 272, and 2201 ± 82 kg CO2‐eq·ha−1·yr−1. Organic practices had the greatest potential for soil GHG flux reduction, with 4577 ± 272 kg CO2‐eq·ha−1·yr−1. Annual differences in weather or management conditions contributed more to the variance in annual GHG emissions than soil variability did. We concluded that the DAYCENT model was successful at predicting GHG emissions of different alternative management systems in California, but that a sound error analysis must accompany the predictions to understand the risks and potentials of GHG mitigation through adoption of alternative practices.
Saproxylic and non‐saproxylic beetle assemblages in boreal spruce forests of different age and forestry intensity
Authors: Stenbacka Fredrik , Hjältén Joakim , Hilszczański Jacek , Dynesius Mats
Published: June 2010

Current clear‐cutting forestry practices affect many boreal organisms negatively, and those dependent on dead wood (saproxylics) are considered as particularly vulnerable. The succession of species assemblages in managed forest habitats regenerating after clear‐cutting is, however, poorly known. We compared beetle assemblages in three successional stages of managed boreal spruce forests established after clear‐cutting and two types of older spruce forests that had not been clear‐cut. We also assessed whether saproxylic and non‐saproxylic beetle assemblages show similar biodiversity patterns among these forest types. Beetles were collected in window traps in nine study areas, each encompassing a protected old‐growth forest (mean forest age ~160 years, mean dead wood volume 34 m3/ha), an unprotected mature forest (~120 years old, 15 m3/ha), a middle‐aged commercially thinned forest (53 years old, 3 m3/ha), a young unthinned forest (30 years old, 4 m3/ha), and a clearcut (5–7 years after harvest, 11 m3/ha). Saproxylic beetles, in particular red‐listed species, were more abundant and more species rich in older forest types, whereas no significant differences among forest types in these variables were detected for non‐saproxylics. The saproxylic assemblages were clearly differentiated; with increasing forest age, assemblage compositions gradually became more similar to those of protected old‐growth forests, but the assemblage composition in thinned forests could not be statistically distinguished from those of the two oldest forest types. Many saproxylic beetles adapted to late‐successional stages were present in thinned middle‐aged forests but absent from younger unthinned forests. In contrast, non‐saproxylics were generally more evenly distributed among the five forest types, and the assemblages were mainly differentiated between clearcuts and forested habitats. The saproxylic beetle assemblages of unprotected mature forests were very similar to those of protected old‐growth forests. This indicates a relatively high conservation value of mature boreal forests currently subjected to clear‐cutting and raises the question of whether future mature forests will have the same qualities. Our results suggest a high beetle conservation potential of developing managed forests, provided that sufficient amounts and qualities of dead wood are made available (e.g., during thinning operations). Confirming studies of beetle reproduction in dead wood introduced during thinning are, however, lacking.
Finding needles (or ants) in haystacks: predicting locations of invasive organisms to inform eradication and containment
Authors: Schmidt Daniel , Spring Daniel , Nally Ralph Mac , Thomson James R. , Brook Barry W. , Cacho Oscar , McKenzie Michael
Published: June 2010

To eradicate or effectively contain a biological invasion, all or most reproductive individuals of the invasion must be found and destroyed. To help find individual invading organisms, predictions of probable locations can be made with statistical models. We estimated spread dynamics based on time‐series data and then used model‐derived predictions of probable locations of individuals. We considered one of the largest data sets available for an eradication program: the campaign to eradicate the red imported fire ant (Solenopsis invicta) from around Brisbane, Australia. After estimating within‐site growth (local growth) and inter‐site dispersal (saltatory spread) of fire ant nests, we modeled probabilities of fire ant presence for >600 000 1‐ha sites, including uncertainties about fire ant population and spatial dynamics. Such a high level of spatial detail is required to assist surveillance efforts but is difficult to incorporate into common modeling methods because of high computational costs. More than twice as many fire ant nests would have been found in 2008 using predictions made with our method rather than those made with the method currently used in the study region. Our method is suited to considering invasions in which a large area is occupied by the invader at low density. Improved predictions of such invasions can dramatically reduce the area that needs to be searched to find the majority of individuals, assisting containment efforts and potentially making eradication a realistic goal for many invasions previously thought to be ineradicable.
A new parameterization for estimating co‐occurrence of interacting species
Authors: Waddle J. Hardin , Dorazio Robert M. , Walls Susan C. , Rice Kenneth G. , Beauchamp Jeff , Schuman Melinda J. , Mazzotti Frank J.
Published: June 2010

Models currently used to estimate patterns of species co‐occurrence while accounting for errors in detection of species can be difficult to fit when the effects of covariates on species occurrence probabilities are included. The source of the estimation problems is the particular parameterization used to specify species co‐occurrence probability. We develop a new parameterization for estimating patterns of co‐occurrence of interacting species that allows the effects of covariates to be specified quite naturally without estimation problems. In our model, the occurrence of one species is assumed to depend on the occurrence of another, but the occurrence of the second species is not assumed to depend on the presence of the first species. This pattern of co‐occurrence, wherein one species is dominant and the other is subordinate, can be produced by several types of ecological interactions (predator–prey, parasitism, and so on).

A simulation study demonstrated that estimates of species occurrence probabilities were unbiased in samples of 50–100 locations and three surveys per location, provided species are easily detected (probability of detection ≥ 0.5). Higher sample sizes (>200 locations) are needed to achieve unbiasedness when species are more difficult to detect. An analysis of data from treefrog surveys in southern Florida indicated that the occurrence of Cuban treefrogs, an invasive predator species, was highest near the point of its introduction and declined with distance from that location. Sites occupied by Cuban treefrogs were 9.0 times less likely to contain green treefrogs and 15.7 times less likely to contain squirrel treefrogs compared to sites without Cuban treefrogs. The detection probabilities of native treefrog species did not depend on the presence of Cuban treefrogs, suggesting that the native treefrog species are naive to the introduced species.
Trait‐mediated interactions and lifetime fitness of the invasive plant Centaurea solstitialis
Authors: Swope Sarah M. , Parker Ingrid M.
Published: June 2010

Plants interact with numerous enemies and mutualists simultaneously and sequentially. Such multispecies interactions can give rise to trait‐mediated indirect effects that are likely to be common in nature but which are also inherently difficult to predict. Understanding multispecies interactions is also important in the use of biological control agents to control invasive plants because modern approaches to biocontrol rely on releasing multiple agents for each target weed. Centaurea solstitialis is one of the most problematic invasive weeds in California, USA, and the weevil Eustenopus villosus is its dominant biological control agent. We conducted a field experiment to quantitatively assess the direct effect of the recently approved biocontrol pathogen Puccinia jaceae f.s. solstitialis on plant performance and any indirect effects that might arise by altering the plant's interactions with Eustenopus or its pollinators (principally the nonnative Apis mellifera). We documented both synergy and interference between the two biocontrol agents depending on the life stage of the weevil. Puccinia infection increased the impact of bud‐feeding by the adult weevils but reduced the impact of seed‐feeding by larval weevils. Neither infection nor Eustenopus attack had an effect on pollinator visitation. The net effect was that attack by both the pathogen and the weevil did not reduce plant fitness relative to plants attacked only by the weevil. Because the consequence to the plant of interacting with one species may depend on the presence or absence of other interacting species, a careful consideration of multispecies interactions may be necessary for the selection of biocontrol agents that act in a complementary manner to reduce plant fitness. Likewise, relatively tractable weed–biocontrol systems allow us to examine multispecies interactions that can be difficult to study experimentally in native systems that are composed of numerous species with well‐established populations.
Foliar fungal pathogens and grassland biodiversity
Authors: Allan Eric , van Ruijven Jasper , Crawley Michael J.
Published: June 2010

By attacking plants, herbivorous mammals, insects, and belowground pathogens are known to play an important role in maintaining biodiversity in grasslands. Foliar fungal pathogens are ubiquitous in grassland ecosystems, but little is known about their role as drivers of community composition and diversity. Here we excluded foliar fungal pathogens from perennial grassland by using fungicide to determine the effect of natural levels of disease on an otherwise undisturbed plant community. Importantly, we excluded foliar fungal pathogens along with rabbits, insects, and mollusks in a full factorial design, which allowed a comparison of pathogen effects along with those of better studied plant enemies. This revealed that fungal pathogens substantially reduced aboveground plant biomass and promoted plant diversity and that this especially benefited legumes. The scale of pathogen effects on productivity and biodiversity was similar to that of rabbits and insects, but different plant species responded to the exclusion of the three plant enemies. These results suggest that theories of plant coexistence and management of biodiversity in grasslands should consider foliar fungal pathogens as potentially important drivers of community composition.
Regional avian species declines estimated from volunteer‐collected long‐term data using List Length Analysis
Authors: Szabo Judit K. , Vesk Peter A. , Baxter Peter W. J. , Possingham Hugh P.
Published: June 2010

Long‐term systematic population monitoring data sets are rare but are essential in identifying changes in species abundance. In contrast, community groups and natural history organizations have collected many species lists. These represent a large, untapped source of information on changes in abundance but are generally considered of little value. The major problem with using species lists to detect population changes is that the amount of effort used to obtain the list is often uncontrolled and usually unknown. It has been suggested that using the number of species on the list, the “list length,” can be a measure of effort. This paper significantly extends the utility of Franklin's approach using Bayesian logistic regression. We demonstrate the value of List Length Analysis to model changes in species prevalence (i.e., the proportion of lists on which the species occurs) using bird lists collected by a local bird club over 40 years around Brisbane, southeast Queensland, Australia. We estimate the magnitude and certainty of change for 269 bird species and calculate the probabilities that there have been declines and increases of given magnitudes.

List Length Analysis confirmed suspected species declines and increases. This method is an important complement to systematically designed intensive monitoring schemes and provides a means of utilizing data that may otherwise be deemed useless. The results of List Length Analysis can be used for targeting species of conservation concern for listing purposes or for more intensive monitoring. While Bayesian methods are not essential for List Length Analysis, they can offer more flexibility in interrogating the data and are able to provide a range of parameters that are easy to interpret and can facilitate conservation listing and prioritization.
Landscape matrix and species traits mediate responses of Neotropical resident birds to forest fragmentation in Jamaica
Authors: Kennedy Christina M. , Marra Peter P. , Fagan William F. , Neel Maile C.
Published: June 2010

Land cover and land use surrounding fragmented habitat can greatly impact species persistence by altering resource availability, edge effects, or the movement of individuals throughout a landscape. Despite the potential importance of the landscape matrix, ecologists still have limited understanding of the relative effects of different types of land cover and land uses on species patterns and processes in natural systems. Here we investigated whether Neotropical resident bird communities in limestone forest patches differed if they were embedded in three different human‐dominated matrix types (agriculture, peri‐urban development, and bauxite mining) relative to sites in continuous forest in central Jamaica. We found that species richness, community composition, and abundances were matrix‐dependent, with agricultural landscapes supporting greater avian diversity and more intact community assemblages than either peri‐urban or bauxite landscapes. Abundance of almost 70% of species differed in forest embedded in the different landscape matrix types. Traits related to resource use best predicted species responses, including diet guild, nest height, habitat association, and foraging strata. Insectivores, frugivores, canopy nesters, understory and canopy foragers, and forest‐restricted species rarely observed in matrix habitats had lower abundances in forest fragments embedded in human‐dominated matrix types than in continuous forest. In contrast, nectarivores, omnivores, granivores, ground and multi‐strata nesters, ground foragers, and species regularly in matrix habitats were least sensitive to forest fragmentation. Results suggest that structure, composition, and land use disturbance regimes in matrix areas impact overall habitat quality in landscapes by potentially mediating resource availability inside as well as outside forest habitat. This study reinforces the importance of differentiating among land cover and land uses in fragmentation research and lends support to the hypothesis that resource availability may be a primary factor driving Neotropical bird responses to fragmentation.
Decision analysis for designing marine protected areas for multiple species with uncertain fishery status
Authors: White J. Wilson , Botsford Louis W. , Moffitt Elizabeth A. , Fischer Douglas T.
Published: June 2010

Marine protected areas (MPAs) are growing in popularity as a conservation tool, and there are increasing calls for additional MPAs. Meta‐analyses indicate that most MPAs successfully meet the minimal goal of increasing biomass inside the MPA, while some do not, leaving open the important question of what makes MPAs successful. An often‐overlooked aspect of this problem is that the success of fishery management outside MPA boundaries (i.e., whether a population is overfished) affects how well MPAs meet both conservation goals (e.g., increased biomass) and economic goals (e.g., minimal negative effects on fishery yield). Using a simple example of a system with homogeneous habitat and periodically spaced MPAs, we show that, as area in MPAs increases, (1) conservation value (biomass) may initially be zero, implying no benefit, then at some point increases monotonically; and (2) fishery yield may be zero, then increases monotonically to a maximum beyond which further increase in MPA area causes yield to decline. Importantly, the points at which these changes in slope occur vary among species and depend on management outside MPAs. Decision makers considering the effects of a potential system of MPAs on multiple species are confronted by a number of such cost–benefit curves, and it is usually impossible to maximize benefits and minimize costs for all species. Moreover, the precise shape of each curve is unknown due to uncertainty regarding the fishery status of each species. Here we describe a decision‐analytic approach that incorporates existing information on fishery stock status to present decision makers with the range of likely outcomes of MPA implementation. To summarize results from many species whose overfishing status is uncertain, our decision‐analysis approach involves weighted averages over both overfishing uncertainty and species. In an example from an MPA decision process in California, USA, an optimistic projection of future fishery management success led to recommendation of fewer and smaller MPAs than that derived from a more pessimistic projection of future management success. This example illustrates how information on fishery status can be used to project potential outcomes of MPA implementation within a decision analysis framework and highlights the need for better population information.
Independent effects of patch size and structural complexity on diversity of benthic macroinvertebrates
Authors: Matias Miguel G. , Underwood A. J. , Hochuli D. F. , Coleman R. A.
Published: June 2010

Despite a long history of work on relationships between area and number of species, the details of mechanisms causing patterns have eluded ecologists. The general principle that the number of species increases with the area sampled is often attributed to a sampling artifact due to larger areas containing greater numbers of individuals. We manipulated the patch size and surface area of experimental mimics of macro‐algae to test several models that can explain the relationship between abundance and species richness of assemblages colonizing different habitats. Our results show that patch size and structural complexity have independent effects on assemblages of macroinvertebrates. Regardless of their structural complexity, larger habitats were colonized by more species. Patch size did not have a significant effect on numbers of individuals, so the increased number of species in larger habitats was not simply a result of random placement associated with sampling increased number of individuals. Similarly, random placement alone could not explain differences in numbers of species among habitats with different structural complexity, contrary to suggestions that the relationship between number of species and surface area might also be a sampling artifact due to more complex habitats having larger areas and therefore sampling more individuals. Future progress would benefit from manipulating properties of habitat in conjunction with experimental manipulations of area.