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Summary There is a growing need for scientific synthesis in ecology and evolution. In many cases, meta-analytic techniques can be used to complement such synthesis. However, missing data are a serious problem for any synthetic efforts and can compromise the integrity of meta-analyses in these and other disciplines. Currently, the prevalence of missing data in meta-analytic data sets in ecology and the efficacy of different remedies for this problem have not been adequately quantified. We generated meta-analytic data sets based on literature reviews of experimental and observational data and found that missing data were prevalent in meta-analytic ecological data sets. We then tested the performance of complete case removal (a widely used method when data are missing) and multiple imputation (an alternative method for data recovery) and assessed model bias, precision and multimodel rankings under a variety of simulated conditions using published meta-regression data sets. We found that complete case removal led to biased and imprecise coefficient estimates and yielded poorly specified models. In contrast, multiple imputation provided unbiased parameter estimates with only a small loss in precision. The performance of multiple imputation, however, was dependent on the type of data missing. It performed best when missing values were weighting variables, but performance was mixed when missing values were predictor variables. Multiple imputation performed poorly when imputing raw data which were then used to calculate effect size and the weighting variable. We conclude that complete case removal should not be used in meta-regression and that multiple imputation has the potential to be an indispensable tool for meta-regression in ecology and evolution. However, we recommend that users assess the performance of multiple imputation by simulating missing data on a subset of their data before implementing it to recover actual missing data.

Detrimental effects of parasitism on host fitness are frequently attributed to parasite-associated perturbations to host energy budgets. It has therefore been widely hypothesized that energetic costs of infection may be manifest as changes in host resting metabolic rate (RMR). Attempts to quantify these effects have yielded contradictory results across host- parasite systems. We used a meta-analysis of the literature to test the effects of parasites on mass-specific (n = 22) and whole-body (n = 15) host RMR. Parasites resulted in a qualitative increase in host RMR in the majority of studies; how- ever, the overall effect of parasites on host RMR was small and statistically nonsignificant. Additionally, substantial among- study variation in host RMR could not be explained by any of the tested covariates. We conclude that the lack of an overall effect of parasites on host metabolism reflects inconsistent directionality and varying magnitudes of parasite-associated ef- fects across studies, rather than an absence of system-specific effects. We contend that a general understanding of parasite effects on host energetics may be best achieved through identifying mechanisms underlying among-system variance in para- site effects on host RMR and relating parasite-associated perturbations of host energy budgets to robust estimates of host fit- ness. Resume : On attribue frequemment les effets nefastes du parasitisme sur la fitness de l'hote aux perturbations des bilans energetiques de l'hote associees au parasite. On emet donc souvent l'hypothese qui veut que les couts energetiques de l'in- fection peuvent se manifester comme des modifications du taux metabolique au repos (RMR) de l'hote. Les tentatives pour mesurer ces effets ont donne des resultats contradictoires dans l'ensemble des systemes hotes-parasites. Nous entreprenons une meta-analyse de la litterature afin de verifier les effets des parasites sur le RMR specifique a la masse (n = 22) et le RMR du corps entier (n = 15) chez les hotes. Dans la plupart des etudes, les parasites causent une augmentation qualitative du RMR de l'hote, mais l'effet global des parasites sur le RMR des hotes est faible et statistiquement non significatif. De plus, il n'a pas ete possible d'expliquer l'importante variation dans le MRM des hotes entre les etudes par les covariables testees. Nous concluons que l'absence d'effet global des parasites sur le metabolisme des hotes demontre une direction in- constante et des ordres de grandeur variables des effets associes aux parasites dans l'ensemble des etudes, plutot qu'une ab- sence d'effets specifiques au systeme. Nous croyons qu'une comprehension generale des effets des parasites sur le systeme energetique des hotes pourra etre obtenue le plus efficacement en identifiant les mecanismes sous-jacents a la variance des effets des parasites sur le RMR des hotes entre les systemes et en mettant en relation les perturbations des bilans energeti- ques associees aux parasites et des estimations robustes de la fitness des hotes. (Traduit par la Redaction)

Empirical studies often reveal deleterious effects of parasites on host survival, but the ecological and environmental pro cesses modulating parasite-associated host mortality are not well understood. We conducted meta-analysis of experimental studies assessing parasite-associated mortality (n52) to evaluate broad-scale patterns in host mortality risk relative to host or parasite taxon, parasite life cycle, or local environmental conditions. Overall, likelihood of host mortality was ~2.6 times higher among infected individuals when compared with hosts that either lacked parasites or had experimentally-reduced parasite burdens. Parasites with complex life cycles reliant on predation-mediated transmission generally were associated with higher mortality risk than those exploiting other transmission strategies. We also detected a negative relationship between parasite-associated host mortality and latitude; host mortality risk declined by ~2.6% with each degree increase in latitude. This result indicated the likely importance of abiotic factors in determining parasite effects. Host taxonomy fur ther influenced parasite-associated mortality risk, with amphibian, fish, and mollusc hosts generally having higher hazard than arthropod, mammal, and bird hosts. Our results suggest patterns that conform to the predicted link between host mortality and parasite transmissibility, and pathogenicity. The relationship between host mortality and latitude in particu lar may portend marked shifts in host–parasite relationships pursuant to ongoing and projected global climate change.

Techniques most commonly used to estimate migratory shorebird abundance often yield estimates with a wide margin of error, and fail to consider extent of habitat use. This study was designed to investigate whether observation of percentage of a given area covered by shorebird footprints may be useful in obtaining accurate estimates of habitat use. Flocks of Semipalmated Sandpipers (Calidris pusilla) foraging on mudflats in the upper Bay of Fundy, Canada, were videotaped and percent-cover by footprints was observed upon their departure. Through review of the videotapes, habitat use was determined in bird-seconds m-2 (sum of time each individual was present divided by the area observed). There was a strong positive, non-linear relationship between percent-cover and habitat use, which suggests that the former can be used to estimate the latter. A theoretical value for habitat use resulting in 100% footprint cover, beyond which the method would be ineffective, was calculated. Observed values did not ...

X-ray photoemission electron microscopy using synchrotron radiation illumination has been used to measure the spatial distributions of albumin on a phase-segregated polystyrene/poly(methyl methacrylate) (PS/PMMA) polymer thin film following adsorption from unbuffered, deionized aqueous solutions under a range of solution concentrations and exposure times. Chemical mapping of the albumin, PS, and PMMA shows that the distribution of albumin on different adsorption sites (PS, PMMA, and the interface between the PS and PMMA domains) changes depending on the concentration of the albumin solution and the exposure time. The preferred sites of absorption at low concentration and short exposure are the PS/PMMA interfaces. Albumin shows a stronger preference for the PS domains than the PMMA domains. The exposure-time dependence suggests that a dynamic equilibrium between albumin in solution and adsorbed on PS domains is established in a shorter time than is required for equilibrating albumin between the solution and the PMMA domains. The explanation of these preferences in terms of possible adsorption mechanisms is discussed.