Lluís Jover | Universitat de Barcelona (original) (raw)

Papers by Lluís Jover

Diversity and Distributions, 2011

Archives of Environmental Contamination and Toxicology, 2013

The Birama Swamp is the second largest wetland in the Caribbean region and it is inhabited by lar... more The Birama Swamp is the second largest wetland in the Caribbean region and it is inhabited by large populations of waterbirds. Here we report, for the first time, the foraging ecology and pollutant levels of three Ardeidae species: Cattle egret (Bubulcus ibis), Snowy egret (Egretta thula), and Tricolored heron (E. tricolor) breeding in this wetland using stable-isotope (d 15 N and d 13 C) and trace elements [mercury (Hg), lead (Pb), and selenium (Se)] analysis of chick feathers. Our results showed that individuals from all species occupied similar trophic levels. However, we found significant differences for d 13 C, with the highest values in cattle egret indicating its use of terrestrial habitats and a generalist and opportunist behavior. No significant differences were found for Pb among species. Yet, Hg levels were greater and similar in tricolored heron and snowy egret than in cattle egret, which was associated with their greater use of aquatic environments. Snowy egret had the lowest values of Se differing significantly with the other two species suggesting a different relative use of prey type. Modeling log-Hg concentration in relation to d 15 N and d 13 C showed an independent and significant relationship among species but without interaction with species level indicating that within a particular

Hepatology, 1994

Our uncontrolled phase II study was aimed at assessing the efficacy of transarterial embolization... more Our uncontrolled phase II study was aimed at assessing the efficacy of transarterial embolization in patients with hepatocellular carcinoma and to determine the parameters associated with a favorable response to treatment, improved survival or both. Fifty consecutive patients (25 corresponding to Okuda's stage I and 25 to stage II) with hepatocellular carcinoma (41 being multinodular or massive) were included. Transarterial embolization induced a self-limited postembolization syndrome that was well tolerated. Nevertheless, three patients died shortly after the procedure because of tumor progression (two cases) or progressive liver failure. A favorable response (extensive necrosis with reduction of tumor area greater than 50%) was achieved in 81% of the cases, and this result was independently (p < 0.05) related to a preserved performance status and to a lower alphafetoprotein concentration. The survival of the patients at 1 and 2 yr was 65% and 38%, respectively, better than the expected survival according to a mathematical model obtained from a historical series of untreated cases (42% and 20%, respectively). Cox regression analysis disclosed that both a favorable therapeutic response and a preserved physical condition (reflected by performance status of 0 or 1) were independently associated with better survival (regression coefficient -2.248 and 0.869, respectively). These data indicate that transarterial embolization has a marked antitumoral effect in patients with inoperable hepatocellular carcinoma and that the therapeutic success is associated with improved survival. Nevertheless, because the potential benefit for survival observed in this uncontrolled study appears to be moderate, prospective controlled trials to ascertain the real usefulness of this therapeutic approach are mandatory. (HEPATOLOGY 1994;20:643-650).

Statistics in Medicine, 2005

In any field in which decisions are subject to measurements, interchangeability between the metho... more In any field in which decisions are subject to measurements, interchangeability between the methods used to obtain these measurements is essential. To consider methods as interchangeable, a certain degree of agreement is needed between the measurements they provide. The concordance correlation coefficient is an index that assesses the strength of agreement and it has been widely applied in situations in which measurements are made on a continuous scale. Recently the concordance correlation coefficient has been defined as a specific intraclass correlation coefficient estimated by the variance components of a Normal–Normal mixed linear model. Although this coefficient was defined for the continuous scale case, it may also be used with a discrete scale. In this case the data are often transformed and normalized, and the concordance correlation is applied. This study discusses the expression of the concordance correlation coefficient for discrete Poisson data by means of the Poisson–Normal generalized linear mixed model. The behaviour of the concordance correlation coefficient estimate is assessed by means of a simulation study, in which the estimates were compared using four models: three Normal–Normal mixed models with raw data, log-transformed data and square-root transformed data, and the Poisson–Normal generalized linear mixed model. An example is provided in which two different methods are used to measure CD34+ cells. Copyright © 2005 John Wiley & Sons, Ltd.

Biometrics, 2003

The intraclass correlation coefficient (ICC) and the concordance correlation coefficient (CCC) ar... more The intraclass correlation coefficient (ICC) and the concordance correlation coefficient (CCC) are two of the most popular measures of agreement for variables measured on a continuous scale. Here, we demonstrate that ICC and CCC are the same measure of agreement estimated in two ways: by the variance components procedure and by the moment method. We propose estimating the CCC using variance components of a mixed effects model, instead of the common method of moments. With the variance components approach, the CCC can easily be extended to more than two observers, and adjusted using confounding covariates, by incorporating them in the mixed model. A simulation study is carried out to compare the variance components approach with the moment method. The importance of adjusting by confounding covariates is illustrated with a case example.

BMC Bioinformatics, 2008

Background: MLPA method is a potentially useful semi-quantitative method to detect copy number al... more Background: MLPA method is a potentially useful semi-quantitative method to detect copy number alterations in targeted regions. In this paper, we propose a method for the normalization procedure based on a non-linear mixed-model, as well as a new approach for determining the statistical significance of altered probes based on linear mixed-model. This method establishes a threshold by using different tolerance intervals that accommodates the specific random error variability observed in each test sample.

Journal of Biopharmaceutical Statistics, 2007

The concordance correlation coefficient (CCC) is an index that assesses the agreement between con... more The concordance correlation coefficient (CCC) is an index that assesses the agreement between continuous measures made by different observers. At least four methods are used to estimate the CCC: two (Lin's method, Variance Components) which are defined on the basis that data are normally distributed, and the two others (U-statistics, GEE) which do not assume any particular distribution of the data. Here the four methods are compared with skewed data from a model in which the subject means follow a log-normal distribution while the within-subject variability is assumed to be normally distributed. An example of alcohol consumption is considered and a simulation study is performed.

Public Health Nutrition, 2007

Objectives: To analyse trends in energy and nutrient intakes and nutritional adequacy from 1992 t... more Objectives: To analyse trends in energy and nutrient intakes and nutritional adequacy from 1992 to 2003. Design: Two consecutive cross-sectional studies carried out on random samples of the Catalan population ENCAT 1992-93 and ENCAT 2002-03. Dietary intake was assessed by means of two 24-hour recalls on non-consecutive days. Spanish food consumption tables were used. Energy and nutrient data were adjusted for intraindividual variability, and the Spanish recommend nutrient intakes (RNIs) were used in the analysis. Setting: Catalonia region, North Eastern Spain. Subjects: Analysis is based on a total of 4701 individuals; 2641 from ENCAT 1992-93 (1210 men and 1431 women) and 2060 from ENCAT 2002-03 (954 men and 1106 women), aged 10-75 years. Results: No relevant changes in energy intake trends were observed, although a decrease was observed in the daily consumption of proteins (27 g), cholesterol (256 mg), potassium (2245 mg), vitamin A (2283 RE mg), retinoids (271 mg), carotenoids (21520 mg), niacin (229 mg), folates (215 mg), vitamin B 12 (21.6 mg) vitamin D (20.5 mg), fibre and iron, and an increase in the consumption of calcium (157 mg) and a slight increase in lipids and fatty acids (% energy). In general, the most outstanding trends were those of vitamin A (as a result of the decreased consumption of offal), proteins, vitamin D and B 12 (due to the decreased consumption of meat and fish) and calcium (as a consequence of the increased consumption of dairy products). Conclusion: No changes were observed in the energy intake of males or females; therefore, the obesity changes may possibly be attributed to changes in physical activity patterns. However, an increase in energy sources of a poorer nutritional profile has been identified, especially for between meal snacks.

Waterbirds, 2003

Avoidance of predators has long been regarded as a major benefit in colonial breeding. Neverthele... more Avoidance of predators has long been regarded as a major benefit in colonial breeding. Nevertheless, field and comparative studies have not shown a clear relationship between predation and coloniality. In the present study, we examine the association between aerial egg predation on the Common Tern ( Sterna hirundo ), and sub-colony size, nest aggregation and reproductive synchrony. Fieldwork was carried out at the Ebro Delta colony (north-western Mediterranean), where Common Terns breed syntopically with potential predators. Sub-colonies placed in a small area were used instead of distant colonies in an attempt to minimize site effects, e.g., the abundance of predators. We used logistic regression with random effect (i.e., sub-colony) to test simultaneously the effect of the studied factors on the risk of predation. In addition, the random effect allowed us to account for the extra-binomial variability due to the potential non-independence of nests of the same sub-colony (clustered observations). Our results support the contention that both breeding in large colonies and in aggregated territories confers protection against aerial predators. In addition, synchrony in relation to the whole colony had no effect on the risk of egg predation. However, birds breeding asynchronously earlier in the season than the average in their own sub-colony were more likely to suffer egg predation than eggs from late asynchronous nesters.

Bulletin of Environmental Contamination and Toxicology, 1997

Ibis, 1998

A significant decrease in the body size of Audouin's Gulls Larus audouinii breeding at the Chafar... more A significant decrease in the body size of Audouin's Gulls Larus audouinii breeding at the Chafarinas Islands is reported. The decrease in linear measurements in the current breeding population ranged from 2.5% to 5.6% in males and from 0.61% to 4.4% in females. This was detected when assessing the reliability of a sex-discriminating function derived for the same colony 13 years earlier. When applied to the current population, this function failed to predict the sex of a large proportion of males (44%). The relative decrease in mean size was significantly greater in males than in females for culmen, nalospi and tarsus lengths, while for bill depth at culmen, wing length and body mass the relative decrease was similar in both sexes. Since the extent of differences depended on sex, these differences cannot be attributed to a systematic between-observer bias. Mean body size reduction might be either the result of a greater proportion of small breeding birds in the current population, because of increased availability of nesting sites (competition relaxation hypothesis), or an outcome of environmental factors affecting growth parameters (environmental constraint hypothesis). According to the first hypothesis, the changes observed would be associated with higher variability values. Conversely, if the second is true, the degree of variability should be similar. Since there are no significant differences in the degree of variability shown in the two data sets, our results support the second hypothesis. The environmental constraint acting via growth parameters is probably related to the increase in the number of Audouin's Gull breeding pairs while food availability was depleted. Our data suggest that changes in the duration of the growth period, rather than in the growth rates themselves, are involved in the body size differences found.

Environmental Pollution, 1996

Concentrations of cadmium, copper and zinc have been analyzed in muscle, liver and kidney tissues... more Concentrations of cadmium, copper and zinc have been analyzed in muscle, liver and kidney tissues of fin whales (Balaenoptera physalus) from two locations in the North Atlantic, Iceland and Spain. The concentrations of zinc in the muscle and that of cadmium in the liver and the kidney were significantly higher in fin whales from Iceland. Other differences between whales from the two areas concern the dynamics of cadmium in the organism. These findings support the hypothesis that fin whales from the two sites belong to different stocks and that cadmium in the organism can be used as a complementary tool in studies of population identity.

Oecologia, 1997

The diets of two potential competitor species, Audouin's Larus audouinii and yellow-legged gulls ... more The diets of two potential competitor species, Audouin's Larus audouinii and yellow-legged gulls Larus cachinnans, were examined while they bred at the Chafarinas Islands during 1993, 1994, and 1995. Data were collected during two commercial fishing regimes: (1) trawling and purse seine fisheries, and (2) diurnal trawlers only. Since the food supply for the gulls in this area was heavily reliant on the activity of purse seine fisheries, these contrasting situations allowed us to analyze short-term effects, induced by daily changes in food supply, on niche width, dietary shift, and niche overlap between the two species. Overall, both species relied mainly on fish for food, especially Clupeiforms, in the case of Audouin's gull irrespective of the fishing situation, and in the case of the yellow-legged gull, only when purse seine fishing was in operation. When purse seine boats did not operate (food shortage), yellow-legged gulls broadened their niche, consuming equal amounts of all the feeding resources, and they showed a dietary shift toward a greater consumption of prey from refuse tips. In contrast, Audouin's gulls did not change their niche width, but showed a slight dietary shift away from the consumption of epipelagic fish, compensated by an increase in reliance on benthic-mesopelagic resources. Niche overlap was clearly higher on days when both fishing fleets operated, probably because a superabundant food resource facilitates high overlap without affecting coexistence between the two species. Since our study was developed on the basis of daily variations in food supply, and competition effects are to be expected on a longer-term basis, these changes can be seen as the outcome of the coexistence of two species in stable competitive equilibrium.

Science of The Total Environment, 1995

Levels of PCBs, DDT and HCB were determined in 56 eggs belonging to 26 complete clutches of Audou... more Levels of PCBs, DDT and HCB were determined in 56 eggs belonging to 26 complete clutches of Audouin's Gull (Lams audouinii) breeding in the Ebro Delta (Northeast Spain). DDT levels were comparable to those found in other areas of the region, while those of PCBs were far more variable being more site dependent. Variability in pollutant load was analysed for both intra-and inter-clutch effects. A case clutch approach was used to assess pollutant differences among clutch sizes and whether a laying order effect on egg xenobiotic contents exists. Two-egg clutches presented a significant female effect, whilst in three-egg clutches this was only sign&ant for the second and third eggs. The environmental relevance of these results for monitoring programs and the usefulness of seabird eggs as biological indicators are discussed.

Journal of Avian Biology, 2000

Solís, J. 2000. How costly is clutch formation in the Audouin's Gull Larus audouinii? -J. Avian B... more Solís, J. 2000. How costly is clutch formation in the Audouin's Gull Larus audouinii? -J. Avian Biol. 31: 467-575.

Marine Pollution Bulletin, 1993

Total and organic mercury concentrations were determined in muscle, liver and kidney of thirty-si... more Total and organic mercury concentrations were determined in muscle, liver and kidney of thirty-six fin whales (Balaenoptera physalus) of the Northeast Atlantic. Age, sex and length relationships for both forms of metal were examined. Tissue concentrations were lower than those of toothed whales and seals. A slight increase with age was observed for total mercury concentrations in muscle and liver and organic mercury concentrations in liver, which suggests a low rate of excretion for the metal, even at low concentrations. No differences between sexes were found regarding mercury concentrations, nor to their accumulation pattern.

Archives of Environmental Contamination and Toxicology, 2000

We determined mercury and selenium in 43 eggs (eggshell, albumen, and yolk) which belong to diffe... more We determined mercury and selenium in 43 eggs (eggshell, albumen, and yolk) which belong to different clutch sizes of Audouin's gull from the Chafarinas Islands. The results were compared with those obtained previously with the same species at the Ebro Delta. Both, the intra- and the interclutch sources of variability have been examined. There is an effect of the female on mercury and selenium concentrations in a clutch, which supports the use of eggs as monitoring tools. The distribution pattern of mercury among albumen, yolk and eggshell, the dynamics of this element during the laying process, as well as data concerning egg formation strategies suggest that the mercury in the albumen corresponds mainly to the mercury acquired by the female while feeding in the breeding area. The mercury and selenium levels of the eggs from the Chafarinas Islands were lower than those of the Ebro Delta, which can be due to differences in both the marine contamination and the diet in the two colonies.

Archives of Environmental Contamination and Toxicology, 2003

The main goal of the present work has been to study the use of egret eggs to assess environmental... more The main goal of the present work has been to study the use of egret eggs to assess environmental pollution by POPs (HCB, HCHs, cyclodienes, DDTs and PCBs) in three Pakistani wetlands that are presumed to be affected by different types of pollution. Taunsa Barrage, affected mainly by agricultural pollutants; Karachi Harbor because of the supposed exposure to industrial activity-related POPs; and Haleji Lake as a relatively pristine area because of its location in a stony desert. Taunsa Barrage and Haleji Lake are wetlands of international importance according to the Ramsar Convention, while the Karachi Harbor is of interest because of the large human population living there. Eggs of the white (Egretta garzetta garzetta) and dark (Egretta garzetta gularis) morphs of Little Egrets were used as monitoring tools. Concentrations were also determined in several prey in this species' diet and in the sediments collected in their foraging areas. Differences in egg pollutant content among the three localities were significant for all the compounds. Overall, the eggs from Haleji Lake and Karachi showed, respectively, the lowest and highest percentages of detection and organochlorine concentrations. Biomagnification from sediments to prey and then to eggs has been documented in the three areas studied and is accompanied by higher percentages of detection of different compounds through the compartments. Differences in the biomagnification factor among the areas were small, even when differences in pollutant concentrations were high, suggesting that eggs are reliable indicators of POPs in the environment. The values found were generally lower than those reported for the eggs of large herons from North America or the Mediterranean basin, and are about the same order of magnitude that those of other medium-sized egrets from other parts of the world.

Archives of Environmental Contamination and Toxicology, 1997

Heavy metal (Zn, Cu, Mn, Cd, Pb, Hg) and Se concentrations were analyzed in 57 Audouin's gull (La... more Heavy metal (Zn, Cu, Mn, Cd, Pb, Hg) and Se concentrations were analyzed in 57 Audouin's gull (Larus audouinii) eggs belonging to different clutch sizes. Inter- and intraclutch variability in metal concentrations was investigated as a potential source of bias in the assessment of pollution levels. Moreover, we analyzed the relationship between metal levels in the shell and in the contents, to evaluate the reliability of museum eggshells as indicators of historical changes of these pollutants. An outstanding female effect and/or a laying order effect underlies egg Hg levels; the fact that eggs in a clutch are not independent observations needs to be taken into account both when designing sampling strategies and when performing any analysis or interpretation of the results. The relationship between Hg in shells and contents is not sufficiently accurate to allow the use of egg-shell concentration as a reliable predictor of egg-contents concentration. However, if changes in the ecosystems are large enough it could be used to trace gross historical trends of these pollutants.