Optimization of embryonic thermal programming confirms increased liver fattening in mule ducks and changes in lipid metabolism

Introduction: The embryonic thermal programming (TM) in birds has been shown to impact several physiological parameters such as resistance to thermal stress, muscle growth or immunity. In mule ducks, it has recently been shown that TM can induce metabolic programming resulting in increased liver weight and fat storage after overfeeding. However, a decrease in hatchability and foie gras quality was also observed, suggesting that this technique needs to be optimized. Here, we tested a new thermal manipulation condition determined with the objective of avoiding negative impacts while maintaining or improving liver properties. Methods: The eggs of the control group were incubated at 37.6°C during the whole incubation period while those of the experimental group (TM group) were incubated at 39.3°C 16 h/24 h from the 11^th day of incubation to the 21^st. After hatching, all the animals were fed and raised under the same conditions until the age of 12 weeks. At this stage, one part of the animals was overfed and then slaughtered 2 h (to measure rapid changes in metabolism) or 10 h after the last meal (to obtain the best technological yields), while the other part was ration-fed and slaughtered 2 h after the last meal, at the same age. Results: An 8% increase in foie gras production was measured in the TM group compared to the control group without altering the quality of the final product (nor hatchability), confirming the successful optimization of the metabolic programming. Interestingly, these results allowed us not to reject the previously suggested hypothesis of a potential delay in metabolic processes involved in liver fattening in programmed animals, in particular by measuring a trend reversal regarding the amount of total hepatic lipids in both groups at 2 h and then 10 h after the last meal. Discussion: This study therefore validates the optimization of metabolic programming by embryonic thermal manipulation for duck liver fattening. The understanding of the mechanisms of embryonic thermal programming in birds remains today very incomplete and the search for epigenetic marks (main hypothesis of the concept of programming) at the origin of the observed phenotypes could be the next step of this work.

Fasting/refeeding: an experimental model to study the impact of early thermal manipulation on hepatic metabolism in mule ducks

An increase in egg incubation temperature was previously shown to enhance the metabolism of mule ducks and increase liver fattening after overfeeding, through a metabolic programming mechanism. Here, we examined whether fasting (F) followed by refeeding (RF) in 11-wk-old mule ducks could become an accelerated model to study the mechanisms of metabolic programming following embryonic thermal manipulation. This study investigated the hepatic response of mule ducks subjected to 23 h of fasting and 1 h of refeeding, in control or thermally programmed animals (with an increase of 1°C, 16 h per day from days 13 to 27 of embryogenesis). Liver weight and energy composition, hepatocyte structure, plasma parameters, and gene expression levels were measured at 1, 2, and 4 h after RF. All these parameters were strongly affected by RF, whereas significant impacts of embryonic programming were measured in cell size (+1 µm on average), lipid composition (+4.2% of saturated fatty acids 4 h after the meal), and relative gene expressions (including HK1, SCD1, ELOVL6, and FASN). In addition to confirming previously identified molecular targets of thermal manipulation, this study revealed new ones, thanks to kinetic sampling after RF. Finally, the detailed description of the impact of the F/RF challenge on the liver structure, composition, and gene expression, but also on plasma parameters allowed us to draw a parallel with these same traits measured during overfeeding. This comparative analysis suggests that this protocol could become a pertinent model to study the mechanisms involved in embryonic liver thermal programming, without overfeeding.

Glucose injection into the yolk influences intermediary metabolism in adult Nile tilapia fed with high levels of carbohydrates

Nutritional programming is a concept proposed to be applied in the field of fish nutrition to improve the use of new diets in aquaculture. This study aimed to investigate for the first time the effects of a glucose injection into the yolk at the alevin stage on intermediary metabolism and growth in adult Nile tilapia (Oreochromis niloticus) at 32-37 weeks later in the life. The early stimulus was performed through direct microinjection of 2 M glucose into yolk sacs of Nile tilapia alevin. Subsequently, in adult tilapia, the long-term effects of glucose stimulus on growth performance, blood metabolites, chemical composition in the liver and muscle, expression of genes involved in glucose transport and metabolism (glycolysis and gluconeogenesis) and related pathways (amino acid catabolism and lipogenesis) were investigated. Our results showed that, even though early glucose injection had no effect on growth performance in adult fish, very few significant effects on glucose metabolism were observed. Furthermore, to evaluate the potential metabolic programming after a dietary challenge, a 2 × 2 factorial design with two early stimuli (0.85% NaCl or 2 M glucose) and two different dietary carbohydrate intakes (medium-carbohydrate diet, CHO-M; high-carbohydrate diet, CHO-H) was performed between weeks 33 and 37. As expected, compared with the CHO-M diet, the CHO-H diet led to decreased growth performance, higher glyceamia and triglyceridemia, higher glycogen and lipid levels in the liver as well as down-regulation of gluconeogenesis and amino acid catabolism gene expressions. More interestingly, although early glucose injection had no significant effect on growth performance, it enhanced the capacities for lipogenesis, glycolysis and gluconeogenesis, particularly in fish that were fed the CHO-H diet. Thus, the nutritional programming of tilapia linked to glucose injection into the yolk of alevins is always visible at the adult stage albeit less intense than what we previously observed in juvenile.

Glucose Injection Into Yolk Positively Modulates Intermediary Metabolism and Growth Performance in Juvenile Nile Tilapia (Oreochromis niloticus)

The aim of this study was to explore for the first time in omnivorous fish the concept of nutritional programming. A nutritional stimulus was accomplished by microinjecting 2 M glucose into yolk reserves during the alevin stage in Nile tilapia (Oreochromis niloticus). At the molecular level in fry, at 1 week post-injection, glucose stimuli were associated with the up-regulation of genes involved in glycolysis (pklr, hk1, hk2, and pkma), glucose transport (glut4) pathways and down-regulation of genes related to gluconeogenesis (g6pca1, g6pca2, and pck1) and amino acid catabolism (asat, alat) (P < 0.05), demonstrating that the larvae well received the glucose stimulus at a molecular level. Moreover, 20 weeks after glucose injection, early glucose stimuli were always linked to permanent effects in juvenile fish, as reflected by a higher level of glycolytic enzymes [gck, hk1 and hk2 at both mRNA and enzymatic levels and pyruvate kinase (PK) activity]. Finally, the effects of the glucose stimulus history were also examined in fish fed with two different dietary carbohydrate/protein levels (medium-carbohydrate diet, CHO-M; high-carbohydrate diet, CHO-H) in juvenile fish (during weeks 20-24). As expected, the CHO-H diet induced the expression of glycolytic and lipogenic genes (gck, pklr, hk1, hk2, fpkma, fasn, and g6pd) and suppressed the expression of gluconeogenic and amino acid catabolism genes (g6pca1, pck1, pck2, asat, alat, and gdh). Nevertheless, the early glucose stimulus led to persistent up-regulation of glycolytic enzymes (gck, pklr, hk1, and hk2) at both the mRNA and enzyme activity levels and glucose transporter glut4 as well as lower gluconeogenic pck1 gene expression (P < 0.05). More interestingly, the early glucose stimulus was associated with a better growth performance of juvenile fish irrespective of the diets. These permanent changes were associated with DNA hypomethylation in the liver and muscles, suggesting the existence of epigenetic mechanisms at the origin of programming. In conclusion, for the first time in tilapia, early glucose stimuli were found to be clearly associated with a positive metabolic programming effect later in life, improving the growth performance of the fish.

DNA methylation of the promoter region of bnip3 and bnip3l genes induced by metabolic programming

BACKGROUND

Environmental changes of biotic or abiotic nature during critical periods of early development may exert a profound influence on physiological functions later in life. This process, named developmental programming can also be driven through parental nutrition. At molecular level, epigenetic modifications are the most likely candidate for persistent modulation of genes expression in later life.

RESULTS

In order to investigate epigenetic modifications induced by programming in rainbow trout, we focused on bnip3 and bnip3l paralogous genes known to be sensitive to environmental changes but also regulated by epigenetic modifications. Two specific stimuli were used: (i) early acute hypoxia applied at embryo stage and (ii) broodstock and fry methionine deficient diet, considering methionine as one of the main methyl-group donor needed for DNA methylation. We observed a programming effect of hypoxia with an increase of bnip3a and the four paralogs of bnip3l expression level in fry. In addition, parental methionine nutrition was correlated to bnip3a and bnip3lb1 expression showing evidence for early fry programming. We highlighted that both stimuli modified DNA methylation levels at some specific loci of bnip3a and bnip3lb1.

CONCLUSION

Overall, these data demonstrate that methionine level and hypoxia stimulus can be of critical importance in metabolic programming. Both stimuli affected DNA methylation of specific loci, among them, an interesting CpG site have been identified, namely - 884 bp site of bnip3a, and may be positively related with mRNA levels.

Long-term programming effect of embryonic hypoxia exposure and high-carbohydrate diet at first feeding on glucose metabolism in juvenile rainbow trout

Environmental conditions experienced during early life play an important role in the long-term metabolic status of individuals. The present study investigated whether hypoxia exposure [for 24 h: 2.5 mg O₂ l^-1 (20% dissolved O₂)] during the embryonic stage alone (hypoxic history) or combined with a 5-day high-carbohydrate (60%) diet stimulus at first feeding (HC dietary history) can affect glucose metabolism later in life, i.e. in juvenile fish. After 19 weeks of growth, we observed a decrease in final body mass in fish with an HC dietary history. Feed efficiency was significantly affected by both hypoxic and HC dietary histories. After a short challenge test (5 days) performed with a 30% carbohydrate diet in juvenile trout, our results also showed that, in trout that experienced hypoxic history, mRNA levels of gluconeogenic genes in liver and glucose transport genes in both liver and muscle were significantly increased at the juvenile stage. Besides, mRNA levels of glycolytic genes were decreased in fish with an HC dietary history. Both hypoxic and dietary histories barely affected plasma metabolites or global epigenetic modifications in juvenile fish after the challenge test. In conclusion, our results demonstrated that an acute hypoxic stimulus during early development alone or combined with a hyperglucidic stimulus at first feeding can modify growth performance and glucose metabolism at the molecular level in juvenile trout.

Responses in Micro-Mineral Metabolism in Rainbow Trout to Change in Dietary Ingredient Composition and Inclusion of a Micro-Mineral Premix

Responses in micro-mineral metabolism to changes in dietary ingredient composition and inclusion of a micro-mineral premix (Fe, Cu, Mn, Zn and Se) were studied in rainbow trout. In a 2 x 2 factorial design, triplicate groups of rainbow trout (initial weight: 20 g) were fed over 12 weeks at 17°C a fishmeal-based diet (M) or a plant-ingredient based diet (V), with or without inclusion of a mineral premix. Trout fed the V vs. M diet had lower feed intake, growth, hepato-somatic index, apparent availability coefficient (AAC) of Fe, Cu, Mn and Zn and also lower whole body Se and Zn concentration, whereas whole body Fe and Cu and plasma Fe concentrations were higher. Feeding the V diet increased intestinal ferric reductase activity; at transcriptional level, hepatic hepcidin expression was down-regulated and ferroportin 1 was up-regulated. Transcription of intestinal Cu-transporting ATPases and hepatic copper transporter1 were higher in V0 compared to other groups. Among the hepatic metalo-enzyme activities assayed, only Se-dependent glutathione peroxidase was affected, being lower in V fed fish. Premix inclusion reduced the AAC of Fe, Cu and Zn; increased the whole body concentration of all micro- minerals; up-regulated hepatic hepcidin and down-regulated intestinal ferroportin 1 transcription; and reduced the transcription of Cu-transporting ATPases in the intestine. Overall, the regulation of micro-mineral metabolism in rainbow trout, especially Fe and Cu, was affected both by a change in ingredient composition and micro-mineral premix inclusion.

Frequency and distribution of mixed Plasmodium falciparum-vivax infections in French Guiana between 2000 and 2008

Background

The two main plasmodial species in French Guiana are Plasmodium vivax and Plasmodium falciparum whose respective prevalence influences the frequency of mixed plasmodial infections. The accuracy of their diagnosis is influenced by the sensitivity of the method used, whereas neither microscopy nor rapid diagnostic tests allow a satisfactory evaluation of mixed plasmodial infections.

Methods

In the present study, the frequency of mixed infections in different part of French Guiana was determined using real time PCR, a sensitive and specific technique.

Results

From 400 cases of malaria initially diagnosed by microscopy, real time PCR showed that 10.75 % of the cases were mixed infections. Their prevalence varied considerably between geographical areas. The presence, in equivalent proportions, of the two plasmodial species in eastern French Guiana was associated with a much higher prevalence of mixed plasmodial infections than in western French Guiana, where the majority of the population was Duffy negative and thus resistant to vivax malaria.

Conclusion

Clinicians must be more vigilant regarding mixed infections in co-endemic P. falciparum/P. vivax areas, in order to deliver optimal care for patients suffering from malaria. This may involve the use of rapid diagnostic tests capable of detecting mixed infections or low density single infections. This is important as French Guiana moves towards malaria elimination.

High or low dietary carbohydrate:protein ratios during first-feeding affect glucose metabolism and intestinal microbiota in juvenile rainbow trout

Based on the concept of nutritional programming in mammals, we tested whether an acute hyperglucidic-hypoproteic stimulus during first feeding could induce long-term changes in nutrient metabolism in rainbow trout. Trout alevins received during the five first days of exogenous feeding either a hyperglucidic (40% gelatinized starch + 20% glucose) and hypoproteic (20%) diet (VLP diet) or a high-protein (60%) glucose-free diet (HP diet, control). Following a common 105-day period on a commercial diet, both groups were then challenged (65 days) with a carbohydrate-rich diet (28%). Short- and long-term effects of the early stimuli were evaluated in terms of metabolic marker gene expressions and intestinal microbiota as initial gut colonisation is essential for regulating the development of the digestive system. In whole alevins (short term), diet VLP relative to HP rapidly increased gene expressions of glycolytic enzymes, while those involved in gluconeogenesis and amino acid catabolism decreased. However, none of these genes showed persistent molecular adaptation in the liver of challenged juveniles (long term). By contrast, muscle of challenged juveniles subjected previously to the VLP stimulus displayed downregulated expression of markers of glycolysis and glucose transport (not seen in the short term). These fish also had higher plasma glucose (9 h postprandial), suggesting impaired glucose homeostasis induced by the early stimulus. The early stimulus did not modify the expression of the analysed metabolism-related microRNAs, but had short- and long-term effects on intestinal fungi (not bacteria) profiles. In summary, our data show that a short hyperglucidic-hypoproteic stimulus during early life may have a long-term influence on muscle glucose metabolism and intestinal microbiota in trout.

Sensitive and specific detection of Trypanosoma cruzi DNA in clinical specimens using a multi-target real-time PCR approach

Background

The laboratory diagnosis of Chagas disease is challenging because the usefulness of different diagnostic tests will depend on the stage of the disease. Serology is the preferred method for patients in the chronic phase, whereas PCR can be successfully used to diagnose acute and congenital cases. Here we present data using a combination of three TaqMan PCR assays to detect T. cruzi DNA in clinical specimens.

Methods/Principal Findings

Included in the analysis were DNA extracted from 320 EDTA blood specimens, 18 heart tissue specimens, 6 umbilical cord blood specimens, 2 skin tissue specimens and 3 CSF specimens. For the blood specimens both whole blood and buffy coat fraction were analyzed. The specimens were from patients living in the USA, with suspected exposure to T. cruzi through organ transplantation, contact with triatomine bugs or laboratory accidents, and from immunosuppressed patients with suspected Chagas disease reactivation. Real-time PCR was successfully used to diagnose acute and Chagas disease reactivation in 20 patients, including one case of organ-transmitted infection and one congenital case. Analysis of buffy coat fractions of EDTA blood led to faster diagnosis in six of these patients compared to whole blood analysis. The three real-time PCR assays produced identical results for 94% of the specimens. The major reason for discrepant results was variable sensitivity among the assays, but two of the real-time PCR assays also produced four false positive results.

Conclusions/Significance

These data strongly indicate that at least two PCR assays with different performances should be combined to increase the accuracy. This evaluation also highlights the benefit of extracting DNA from the blood specimen's buffy coat to increase the sensitivity of PCR analysis.

Chagas disease is endemic in several Latin American countries and affects approximately 8 to 11 million people. The protozoan parasite, Trypanosoma cruzi, is the agent of Chagas disease, a zoonotic disease that can be transmitted to humans by blood-sucking triatomine bugs. Other routes of infection include congenital transmission, blood transfusion, organ transplantation, accidental inoculation of the parasite during laboratory research and by consuming food and juice contaminated with the parasite. This study focused on the evaluation of three quantitative PCR (QPCR) assays for the diagnosis of Chagas disease. The evaluation was based on the analysis of 349 specimens submitted for confirmatory diagnosis of Chagas disease to the Centers for Disease Control and Prevention from 2008 to 2010. By using such assays we were able to diagnose acute and Chagas disease reactivation in 20 patients, including one case of organ-transmitted infection and one congenital case. The paper also highlights the benefit of extracting DNA from the blood specimen's buffy coat to increase the sensitivity of diagnostic PCR analysis. The results obtained in this study strongly indicate that at least two QPCR assays with different performance characteristics should be combined to increase diagnostic accuracy.

Histoplasma capsulatum in Cayenne, French Guiana

We carried out a soil sampling survey in September 2008 in central Cayenne, French Guiana, using molecular methods to assess the presence of the dimorphic fungus Histoplasma capsulatum. Four of the 31 samples collected (12.9 %) tested positive by PCR, with confirmation of the result by DNA sequencing. H. capsulatum is therefore present in urban environments in French Guiana. These results provide additional support for the primary prophylaxis of AIDS-related histoplasmosis in French Guiana.

Multiple independent introductions of Plasmodium falciparum in South America

The origin of Plasmodium falciparum in South America is controversial. Some studies suggest a recent introduction during the European colonizations and the transatlantic slave trade. Other evidence--archeological and genetic--suggests a much older origin. We collected and analyzed P. falciparum isolates from different regions of the world, encompassing the distribution range of the parasite, including populations from sub-Saharan Africa, the Middle East, Southeast Asia, and South America. Analyses of microsatellite and SNP polymorphisms show that the populations of P. falciparum in South America are subdivided in two main genetic clusters (northern and southern). Phylogenetic analyses, as well as Approximate Bayesian Computation methods suggest independent introductions of the two clusters from African sources. Our estimates of divergence time between the South American populations and their likely sources favor a likely introduction from Africa during the transatlantic slave trade.

International study to evaluate PCR methods for detection of Trypanosoma cruzi DNA in blood samples from Chagas disease patients

Background

A century after its discovery, Chagas disease still represents a major neglected tropical threat. Accurate diagnostics tools as well as surrogate markers of parasitological response to treatment are research priorities in the field. The purpose of this study was to evaluate the performance of PCR methods in detection of Trypanosoma cruzi DNA by an external quality evaluation.

Methodology/Findings

An international collaborative study was launched by expert PCR laboratories from 16 countries. Currently used strategies were challenged against serial dilutions of purified DNA from stocks representing T. cruzi discrete typing units (DTU) I, IV and VI (set A), human blood spiked with parasite cells (set B) and Guanidine Hidrochloride-EDTA blood samples from 32 seropositive and 10 seronegative patients from Southern Cone countries (set C). Forty eight PCR tests were reported for set A and 44 for sets B and C; 28 targeted minicircle DNA (kDNA), 13 satellite DNA (Sat-DNA) and the remainder low copy number sequences. In set A, commercial master mixes and Sat-DNA Real Time PCR showed better specificity, but kDNA-PCR was more sensitive to detect DTU I DNA. In set B, commercial DNA extraction kits presented better specificity than solvent extraction protocols. Sat-DNA PCR tests had higher specificity, with sensitivities of 0.05–0.5 parasites/mL whereas specific kDNA tests detected 5.10⁻³ par/mL. Sixteen specific and coherent methods had a Good Performance in both sets A and B (10 fg/µl of DNA from all stocks, 5 par/mL spiked blood). The median values of sensitivities, specificities and accuracies obtained in testing the Set C samples with the 16 tests determined to be good performing by analyzing Sets A and B samples varied considerably. Out of them, four methods depicted the best performing parameters in all three sets of samples, detecting at least 10 fg/µl for each DNA stock, 0.5 par/mL and a sensitivity between 83.3–94.4%, specificity of 85–95%, accuracy of 86.8–89.5% and kappa index of 0.7–0.8 compared to consensus PCR reports of the 16 good performing tests and 63–69%, 100%, 71.4–76.2% and 0.4–0.5, respectively compared to serodiagnosis. Method LbD2 used solvent extraction followed by Sybr-Green based Real time PCR targeted to Sat-DNA; method LbD3 used solvent DNA extraction followed by conventional PCR targeted to Sat-DNA. The third method (LbF1) used glass fiber column based DNA extraction followed by TaqMan Real Time PCR targeted to Sat-DNA (cruzi 1/cruzi 2 and cruzi 3 TaqMan probe) and the fourth method (LbQ) used solvent DNA extraction followed by conventional hot-start PCR targeted to kDNA (primer pairs 121/122). These four methods were further evaluated at the coordinating laboratory in a subset of human blood samples, confirming the performance obtained by the participating laboratories.

Conclusion/Significance

This study represents a first crucial step towards international validation of PCR procedures for detection of T. cruzi in human blood samples.

A century after its discovery, Chagas disease, caused by the parasite Trypanosoma cruzi, still represents a major neglected tropical threat. Accurate diagnostics tools as well as surrogate markers of parasitological response to treatment are research priorities in the field. The polymerase chain reaction (PCR) has been proposed as a sensitive laboratory tool for detection of T. cruzi infection and monitoring of parasitological treatment outcome. However, high variation in accuracy and lack of international quality controls has precluded reliable applications in the clinical practice and comparisons of data among cohorts and geographical regions. In an effort towards harmonization of PCR strategies, 26 expert laboratories from 16 countries evaluated their current PCR procedures against sets of control samples, composed by serial dilutions of T.cruzi DNA from culture stocks belonging to different lineages, human blood spiked with parasite cells and blood samples from Chagas disease patients. A high variability in sensitivities and specificities was found among the 48 reported PCR tests. Out of them, four tests with best performance were selected and further evaluated. This study represents a crucial first step towards device of a standardized operative procedure for T. cruzi PCR.

Multiplex real-time PCR detection of P. falciparum, P. vivax and P. malariae in human blood samples

Two duplex real-time PCR assays were developed to diagnose three human parasites: Plasmodium falciparum, Plasmodium vivax and Plasmodium malariae. TaqMan duplex real-time PCR was evaluated in 263 blood samples of suspected malaria patients by comparing results against those obtained with microscopy and nested PCR. Compared with nested PCR, duplex real-time PCR assays showed 100% sensitivity and specificity. Duplex real-time PCR detected all mixtures of P. falciparum and P. vivax DNA, except at threshold detection limits for both parasites in which P. vivax was not amplified. Threshold detection limits of real-time PCR were 3.1, 0.3 and 0.8 parasites per microlitre of blood for P. falciparum, P. vivax and P. malariae, respectively. Duplex real-time PCR allows the detection of malarial cases, including mixed species infection, it simplifies analysis and reduces cost. Thus, this protocol may prove invaluable for use in the diagnosis of human infection, trial treatments and epidemiologic studies in which high-throughput analyses are often required.

Recovery and use of Plasmodium DNA from malaria rapid diagnostic tests

The purpose of this study was to show that individual malaria rapid diagnosis tests (MRDTs) could also be used to isolate Plasmodium DNA for genetic studies. We extracted and amplified Plasmodium DNA using two commercial MRDT kits. Phenol/chloroform extraction followed by a nested polymerse chain reaction (PCR) can be used to identify Plasmodium falciparum and Plasmodium vivax from MRDTs. The PCR on MRDT-isolated DNA was more sensitive than antigen capture by MRDT. Satisfactory results were also obtained if older MRDT tests were used, even after long periods of storage at ambient temperature, with no special preservation.

Fine-scale genetic structure and gene dispersal inferences in 10 neotropical tree species

The extent of gene dispersal is a fundamental factor of the population and evolutionary dynamics of tropical tree species, but directly monitoring seed and pollen movement is a difficult task. However, indirect estimates of historical gene dispersal can be obtained from the fine-scale spatial genetic structure of populations at drift-dispersal equilibrium. Using an approach that is based on the slope of the regression of pairwise kinship coefficients on spatial distance and estimates of the effective population density, we compare indirect gene dispersal estimates of sympatric populations of 10 tropical tree species. We re-analysed 26 data sets consisting of mapped allozyme, SSR (simple sequence repeat), RAPD (random amplified polymorphic DNA) or AFLP (amplified fragment length polymorphism) genotypes from two rainforest sites in French Guiana. Gene dispersal estimates were obtained for at least one marker in each species, although the estimation procedure failed under insufficient marker polymorphism, limited sample size, or inappropriate sampling area. Estimates generally suffered low precision and were affected by assumptions regarding the effective population density. Averaging estimates over data sets, the extent of gene dispersal ranged from 150 m to 1200 m according to species. Smaller gene dispersal estimates were obtained in species with heavy diaspores, which are presumably not well dispersed, and in populations with high local adult density. We suggest that limited seed dispersal could indirectly limit effective pollen dispersal by creating higher local tree densities, thereby increasing the positive correlation between pollen and seed dispersal distances. We discuss the potential and limitations of our indirect estimation procedure and suggest guidelines for future studies.