Studies about fish assemblages in Brazilian streams have grown in recent years, however, it remai... more Studies about fish assemblages in Brazilian streams have grown in recent years, however, it remains unclear whether this increase is followed by increments in the diversity of addressed topics and theoretical frameworks adopted by researchers. We performed a systematic search for Brazilian studies on stream fish assemblages recording study region, publication year, objectives, and spatial and temporal scales adopted. The number of studies is unevenly distributed among regions. Most papers describe the general structure of local fish assemblages and their scientific objectives have not varied through time. Studies have been conducted mainly at small temporal and spatial scales, though the latter is increasing over time. We argue for the need of focusing on recently developed ecological theories and frameworks, and expanding the temporal and spatial scales of studies. These changes will improve regional and local conservation policies, and the visibility of aquatic Brazilian research in the global scientific community.
This study aimed to establish the presence of spatial synchrony for three riverine fish populatio... more This study aimed to establish the presence of spatial synchrony for three riverine fish populations (stone loach Barbatula barbatula L., European minnow Phoxinus phoxinus L. and gudgeon Gobio gobio L.) in two spatially-close sites of the Garonne River (SW France). Sampling was carried out by electrofishing from 1994 to 1999. The fish were split into two age classes (0+ and >0+) using length-frequency distribution analysis. No autocorrelation was present in our time series. There were significant correlations of densities between sites for stone loach (>0+) and gudgeon (0+), but not for European minnow. A significant positive relationship was observed between maximal flow values and 0+ gudgeon density. No significant associations between flow variables and density were observed for stone loach. These results emphasize the role of external factors in effecting population dynamics, and suggest that their influences differ according to life stage and life-history characteristics.
1. Synchronous fluctuations of the abundance of several populations at a regional scale can be a ... more 1. Synchronous fluctuations of the abundance of several populations at a regional scale can be a sign of a climatic effect on their dynamics (Moran effect). However, the interpretation of spatial synchrony is often complicated by the interaction between climatic disturbances and migrations between the studied populations. 2. We addressed this question by studying 24-year time-series of abundance estimates for four populations of four fish species in three different catchment basins in Côte d'Ivoire (West Africa). As localities from two different basins cannot exchange individuals, dispersal cannot be considered a synchronizing factor in this system.
1. Focusing on the current environmental characteristics, the ‘habitat template’ theory proposes ... more 1. Focusing on the current environmental characteristics, the ‘habitat template’ theory proposes that life-history strategies summarise how evolution has shaped species to cope with the temporal and spatial variability of their present environment. The hierarchical ‘landscape filters’ concept predicts that the distribution of species reflects their specific traits that allow them to pass through multiple habitat filters. Together, these theories showed the importance of identifying the functional relationships of species to selective habitat forces in order to predict the organisation and response of communities to the environment.2. We test the relationships between life-history traits of European freshwater fish species’ and their habitat preferences, to detect the strategies adopted by fish to cope with their current habitat. For this purpose, we use published data on species traits and habitat preferences (microhabitat hydraulics, temperature and oxygen level). We use multivariate analyses to classify fish species’ strategies and test the relationships between strategies and habitat preferences.3. We identified a continuum of life-history patterns between two extremes, with opportunistic and periodic species. Our study supports the idea that microhabitat hydraulics plays a more important role as a template for these species ecological strategies than temperature and oxygen level. Indeed, riffle habitats may select opportunistic species whereas weak relationships are found between species strategies and both their temperature and oxygen level preferences. In addition, the ratio between mortality and growth rate (dimensionless trait), reflecting a trade-off between growth and survival, varied among species according to the use of their hydraulic habitat, with species using deep habitats exhibiting the highest values.4. These general relationships between hydraulics and traits may be of importance in community ecology to develop predictive models to understand how fish communities change with the hydraulic environment.
Body size, ecological tolerance and potential for water quality bioindication in the genus Anacro... more Body size, ecological tolerance and potential for water quality bioindication in the genus Anacroneuria (Plecoptera: Perlidae) from South America. Knowledge about the biology and ecology of neotropical aquatic taxa is crucial to establish general ecological rules and water protection systems. Based mainly on published data, the present work shows the following biological and ecological characteristics of Anacroneuria species (Klapálek 1909): a) the wide range of environmental conditions of rivers where Anacroneuria species occur, b) species number decreases along an increasing elevation gradient, c) body size increases in relation to the maximum altitude of occurrence, d) altitudinal range increases with body size, e) there is a constant relationship between male and female body size, and finally, f) larger females lay larger eggs. In temperate countries, the family Perlidae in general, and the genus Anacroneuria in particular, are viewed as excellent water quality indicators. We suggest that, considering the complexity of the group's ecology in South America, it should not be automatically considered an excellent bioindicator in the Neotropical region. Rev. Biol. Trop. 55 (1): 67-81. Epub 2007 March. 31.
Spatial synchrony in species abundance is a general phenomenon that has been found in populations... more Spatial synchrony in species abundance is a general phenomenon that has been found in populations representing virtually all major taxa. Dispersal among populations and synchronous stochastic effects (the so called “Moran effect”) are the mechanisms most likely to explain such synchrony patterns. Very few studies have related the degree of spatial synchrony to the biological characteristics of species. Here we present a case where specific predictions can be made to relate river fish species characteristics and synchrony determined exclusively by a Moran effect through the expected sensitivity of species to the regional component of environmental stochasticity. By analyzing 23-year time series of abundance estimates in two isolated localities we show that species associated with synchronized reproduction during the wet season, high fecundity, small egg size and high gonado-somatic index (the so called “periodic” strategy) have a higher degree of spatial synchrony in population dynamics than species associated with the opposite traits (the so called “equilibrium” strategy). This is supported by significant relationships (P values <0.01) between species traits and the levels of synchrony after removing taxonomical relatedness. Spatial synchrony computed from summed annual total catches by groups of species, separated into strategy types also showed a significantly higher degree of synchrony for the periodic (r=0.83) than the equilibrium (r=0.46) group. Regional hydrological variability is likely to be partly responsible for the observed synchrony pattern and a regional discharge index showed better relationships with the periodic group, supporting the expected differential effect of regional environmental correlation on population dynamics.
We explored the relationships between diet and morphology in 30 fish species from forested tropic... more We explored the relationships between diet and morphology in 30 fish species from forested tropical streams of the Bolivian Amazon. These species were first assigned to eight broad trophic guilds based on stomach contents analysis. The relationships between diet and morphology were then examined using Redundancy Analysis, after having checked for potential phylogenetical effects. Results show that, independently of any phylogenetic constraints, some of the trophic guilds could be grossly predicted from few relevant morphological attributes (i.e. relative intestinal length, standard length and mouth orientation) and thus suggest a significant link between diet and morphology. In other words, species having similar diet tend to converge to some extent on some morphological attributes. This link was nevertheless rather weak, suggesting that even if morphology may set limits to patterns of resource use, these limits are broad enough to allow fishes changing their choice of prey resources to respond to local biotic and/or abiotic conditions. Résumé -Relations entre le régime alimentaire et les caractéristiques morphologiques des peuplements de poissons de petits cours d'eau forestiers de l'Amazonie bolivienne. Nous avons analysé les relations entre le régime alimentaire et la morphologie de 30 espèces de poissons présentes dans de petits cours d'eau forestiers de l'Amazonie bolivienne. Après une analyse de leurs contenus stomacaux, les 30 espèces ont été réparties, dans un premier temps, dans huit grandes guildes trophiques. Dans un deuxième temps, après avoir analysé les éventuelles contraintes phylogénétiques, nous avons examiné, par analyse multivariée, les relations entre le régime alimentaire et la morphologie des espèces. Les résultats montrent que, indépendamment de la phylogénie, certaines des guildes trophiques peuvent être prédites d'après quelques attributs morphologiques (i.e. longueur relative de l'intestin, longueur standard et orientation de la bouche). Cela étant, ce lien entre régime alimentaire et caractéristiques morphologiques reste relativement faible, ce qui suggère que même si la morphologie limite les possibilités d'utilisation des ressources, cette limite est assez large pour permettre aux espèces de s'adapter à différentes conditions biotiques ou abiotiques locales. fishes, gut length clearly distinguish algivores, detritivores and herbivores from carnivores . However, relationships between diet and morphology are equivocal since other studies found weak and indistinct results rather relating feeding and morphological variables to local environmental factors and 132 C. Ibañez et al.: Aquat. Living Resour. 20, 131-142 (2007)
The hypothesis of convergence takes the deterministic view that community (or assemblage) structu... more The hypothesis of convergence takes the deterministic view that community (or assemblage) structure can be predicted from the environment, and that the environment is expected to drive evolution in a predictable direction. Here we present results of a comparative study of freshwater fish assemblages from headwater streams in four continents (Europe, North America, Africa and South America), with the general objective of testing whether these assemblages display convergent structures under comparable environmental conditions (i.e. assemblage position in the stream longitudinal continuum). We tested this hypothesis by comparing species richness and trophic guilds of those stream fish assemblages represented in available data from multiple sites on each continent. Independent of phylogenetic and historical constraints, fish assemblage richness and trophic structure in the four continents converged along the stream continua to a substantial degree. For the four continents, assemblage richness increased, the proportion of invertivorous species decreased, and the proportion of omnivorous species increased from upstream to downstream, supporting theoretical predictions of the river continuum concept. However, the herbivore/detritivore and piscivore guilds were virtually absent from our small European and North American stream sites, unlike our African and South American stream sites. This divergence can be linked to differences in energy availability between temperate and tropical systems.
The River Continuum Concept (RCC) explains the structural and functional characteristics of strea... more The River Continuum Concept (RCC) explains the structural and functional characteristics of stream communities focusing on the gradually changing physical components from headwaters to downstream habitats of streams and rivers. The global value of the RCC is still uncertain, possibly because physical factors (e.g., altitude and then temperature, stream order, channel width) can vary differently in longitudinal river axes across the world. Moreover, RCC predictions in relation to different physical factors have not been tested adequately in different biomes, especially biomes outside of temperate North America. Here, we report on the functional structure of macroinvertebrate communities in neotropical streams from Bolivia along a broad altitudinal gradient (from 1120 to 4300 m a.s.l.), aiming to understand how altitude can affect the longitudinal changes in functional feeding groups (FFG) and richness predicted by the RCC. The RCC predictions for functional structure were not completely matched when analyzing FFGs in relation to an index of longitudinal stream gradient. However, after removing the effect of altitude by using residuals from regressions between FFGs and altitude, FFG patterns matched RCC predictions more closely. We detected signifi cant relationships between altitude and the relative abundance of collector-gatherers, shredders and scrapers which may be related to changes in temperature, UV radiation and canopy cover along the altitudinal gradient. Our results indicate that altitude combined with position along the longitudinal gradient is an important factor governing the FFG structure of macroinvertebrate communities in neotropical streams.
Productivity (trophic energy) is one of the most important factors promoting variation in species... more Productivity (trophic energy) is one of the most important factors promoting variation in species richness. A variety of species-energy relationships have been reported, including monotonically positive, monotonically negative, or unimodal (i.e. hump-shaped). The exact form of the relationship seems to depend, among other things, on the spatial scale involved. However, the mechanisms behind these patterns are still largely unresolved, although many hypotheses have been suggested. Here we report a case of local-scale positive species-energy relationship. Using 14 local fish assemblages in tropical forested headwater streams (Bolivia), and after controlling for major local abiotic factors usually acting on assemblage richness and structure, we show that rising energy availability through leaf litter decomposition rates allows trophically specialized species to maintain viable populations and thereby to increase assemblage species richness. By deriving predictions from three popular mechanistic explanations, i.e. the 'increased population size', the 'consumer pressure', and the 'specialization' hypotheses, our data provide only equivocal support for the latter. To cite this article: P.A. Tedesco et al., C. R. Biologies 330 (2007). Résumé Relation énergie disponible/richesse spécifique chez les peuplements de poissons de cours d'eau forestiers de l'Amazonie bolivienne. L'énergie disponible dans un écosystème a depuis toujours été considérée comme une contrainte fondamentale à la richesse spécifique animale et végétale qui lui est inféodée. Différentes relations entre richesse et énergie ont été rapportées jusqu'à maintenant, incluant des relations positives, négatives ou unimodales. La forme de la relation semble dépendre, entre autres, de A u t h o r ' s p e r s o n a l c o p y 256 P.A. Tedesco et al. / C. R. Biologies 330 (2007) 255-264
The precise number of extant fish species remains to be determined. About 28,900 species were lis... more The precise number of extant fish species remains to be determined. About 28,900 species were listed in FishBase in 2005, but some experts feel that the final total may be considerably higher. Freshwater fishes comprise until now almost 13,000 species (and 2,513 genera) (including only freshwater and strictly peripheral species), or about 15,000 if all species occurring from fresh to brackishwaters are included. Noteworthy is the fact that the estimated 13,000 strictly freshwater fish species live in lakes and rivers that cover only 1% of the earth’s surface, while the remaining 16,000 species live in salt water covering a full 70%. While freshwater species belong to some 170 families (or 207 if peripheral species are also considered), the bulk of species occur in a relatively few groups: the Characiformes, Cypriniformes, Siluriformes, and Gymnotiformes, the Perciformes (noteably the family Cichlidae), and the Cyprinodontiformes. Biogeographically the distribution of strictly freshwater species and genera are, respectively 4,035 species (705 genera) in the Neotropical region, 2,938 (390 genera) in the Afrotropical, 2,345 (440 genera) in the Oriental, 1,844 (380 genera) in the Palaearctic, 1,411 (298 genera) in the Nearctic, and 261 (94 genera) in the Australian. For each continent, the main characteristics of the ichthyofauna are briefly outlined. At this continental scale, ichthyologists have also attempted to identify ichthyological ‘‘provinces’’ that are regions with a distinctive evolutionary history and hence more or less characteristic biota at the species level. Ichthyoregions are currently identified in each continent, except for Asia. An exceptionally high faunal diversity occurs in ancient lakes, where one of the most noteworthy features is the existence of radiations of species that apparently result from intra-lacustrine speciation. Numerous fish-species flocks have been identified in various ancient lakes that are exceptional natural sites for the study of speciation. The major threats to fish biodiversity are intense and have been relatively well documented: overexploitation, flow modification, destruction of habitats, invasion by exotic species, pollution including the worldwide phenomena of eutrophication and sedimentation, all of which are interacting.
Aim Documentation of the ongoing effect of rain forest refuges at the last glacial maximum (LGM)... more Aim Documentation of the ongoing effect of rain forest refuges at the last glacial maximum (LGM) on patterns of tropical freshwater fish diversity.Location Tropical South and Central America, and West Africa.Methods LGM rain forest regions and species richness by drainage were compiled from published data. GIS mapping was applied to compile drainage area and contemporary primary productivity. We used multiple regression analyses, applied separately for Tropical South America, Central America and West Africa, to assess differences in species richness between drainages that were connected and disconnected to rain forest refuge zones during the LGM. Spatial autocorrelation of the residuals was tested using Moran's I statistic. We added an intercontinental comparison to our analyses to see if a historical signal would persist even when a regional historical effect (climate at the LGM) had already been accounted for.Results Both area and history (contact with LGM rain forest refuge) explained the greatest proportions of variance in the geographical pattern of riverine species richness. In the three examined regions, we found highest richness in drainages that were connected to the rain forest refuges. No significant residual spatial autocorrelation was detected after considering area, primary productivity and LGM rain forest refuges. These results show that past climatic events still affect West African and Latin American regional and continental freshwater fish richness. At the continental scale, we found South American rivers more species-rich than expected on the basis of their area, productivity and connectedness to rain forest refuge. Conversely, Central American rivers were less species-diverse than expected by the grouped model. African rivers were intermediate. Therefore, a historical signal persists even when a regional historical effect (climate at the LGM) had already been accounted for.Main conclusions It has been hypothesized that past climatic events have limited impact on species richness because species have tracked environmental changes through range shifts. However, when considering organisms with physically constrained dispersal (such as freshwater fish), past events leave a perceptible imprint on present species diversity. Furthermore, we considered regions that have comparable contemporary climatic and environmental characteristics, explaining the absence of a productivity effect. From the LGM to the present day (a time scale of 18,000 years), extinction processes should have played a predominant role in shaping the current diversity pattern. By contrast, the continental effects could reflect historical contingencies explained by differences in speciation and extinction rates between continents at higher time scales (millions of years).
Ecology Letters (2010) 13: 421–431Ecology Letters (2010) 13: 421–431AbstractIn this study, we tes... more Ecology Letters (2010) 13: 421–431Ecology Letters (2010) 13: 421–431AbstractIn this study, we test whether established non-native species induce functional changes in natural assemblages. We combined data on the body size of freshwater fish species and a worldwide data set of native and non-native fish species for 1058 river basins. We show that non-native fish species are significantly larger than their native counterparts and are a non-random subset of the worldwide set of fish species. We further show that the median body size of fish assemblages increases in the course of introductions. These changes are the opposite of those expected under several null models. Introductions shift body size patterns related to several abiotic factors (e.g. glacier coverage and temperature) in a way that modifies latitudinal patterns (i.e. Bergmann’s rule), especially in the southern hemisphere. Together, these results show that over just the last two centuries human beings have induced changes in the global biogeography of freshwater fish body size, which could affect ecosystem properties.In this study, we test whether established non-native species induce functional changes in natural assemblages. We combined data on the body size of freshwater fish species and a worldwide data set of native and non-native fish species for 1058 river basins. We show that non-native fish species are significantly larger than their native counterparts and are a non-random subset of the worldwide set of fish species. We further show that the median body size of fish assemblages increases in the course of introductions. These changes are the opposite of those expected under several null models. Introductions shift body size patterns related to several abiotic factors (e.g. glacier coverage and temperature) in a way that modifies latitudinal patterns (i.e. Bergmann’s rule), especially in the southern hemisphere. Together, these results show that over just the last two centuries human beings have induced changes in the global biogeography of freshwater fish body size, which could affect ecosystem properties.
We provide mitochondrial sequence variation of the invasive fish Gambusia holbrooki from 24 Europ... more We provide mitochondrial sequence variation of the invasive fish Gambusia holbrooki from 24 European populations, from Portugal to Greece. Phylogeographic structure in Europe was compared with genetic data from native samples (USA) and historical records were reviewed to identify introduction routes. Overall, data agree with records of historical introductions and translocations, and indicate that the most abundant haplotype throughout Europe originated from North Carolina and corresponded to the first introduction in 1921 to Spain, being transferred to Italy in 1922 and to many countries afterwards. Our results also show that at least another independent introduction occurred first in France and subsequently from France to Greece. Haplotypes of G. affinis were not detected in our European sampling effort but historical records and other data suggest that this species was introduced to Italy in 1927 and it might be present. At the continental scale, there is less diversity in Europe than in North America, in agreement with the low number of introduced fish. At the local scale, some European populations gained diversity from multiple introductions and from “de novo” mutations.
Aim To identify key research questions and challenges that will, if addressed in a timely manner... more Aim To identify key research questions and challenges that will, if addressed in a timely manner, significantly advance the field of freshwater fish biogeography and conservation.Location Globe.Methods By drawing on expertise from different regions of the world, we integrate an illustrative conspectus of recent scientific advancements in fish biogeography with a prospectus of needed areas of scientific inquiry to identify information gaps and priority research needs to advance the science.Results We identified the following core challenges: (1) Testing current and forging new theories in biogeography; (2) Advancing a trait-based biogeography of freshwater fishes; (3) Quantifying extinction risk and loss of fish species in a changing environment; (4) Evaluating the magnitude and geography of extinction debt for freshwater fishes; (5) Elucidating the patterns and drivers of freshwater fish invasions; (6) Forecasting the future geography of freshwater fishes; (7) Understanding the interactive effects of multiple stressors in freshwater ecosystems; (8) Quantifying new features of the biodiversity crisis: fish faunal homogenization and the emergence of novel assemblages; (9) Promoting scientific rigour in emerging freshwater fish conservation strategies and (10) Improving conservation planning strategies for freshwater fish species.Main conclusions By reflecting on recent scientific progress in fish conservation biogeography, we have identified a set of core challenges and priorities requiring future research investment.
Artificial macrophytes were experimentally deployed in Boadella Reservoir (NE Spain) and assessed... more Artificial macrophytes were experimentally deployed in Boadella Reservoir (NE Spain) and assessed for fish use throughout the first 3 months of the 2007 summer drawdown. In total, 1,832 individuals of seven fish species were recorded through visual censuses, with introduced perch Perca fluviatilis being the prevalent species. Fish richness and abundance were significantly higher in artificial macrophytes than in rocky shores and sandy beaches, displaying a unimodal variation through time. P. fluviatilis, Rutilus rutilus and Abramis brama were significantly more abundant in artificial macrophytes than in the other two naturally submersed habitats, where no individuals of these species were recorded. The abundances of Squalius laietanus, Lepomis gibbosus, Micropterus salmoides and Cyprinus carpio were overall greater in artificial macrophytes than in rocky shores but displayed significant habitat × time interactions. A decrease in predation risk was apparently the key-factor of the intensive use of artificial macrophytes by small fish (≤100 mm TL) in Boadella Reservoir, since most species reduced drastically or completely the use of submerged structures when body size increased. This study demonstrates that adding artificial structures mimicking aquatic macrophytes can be an interesting tool to mitigate the adverse effects of water level fluctuations on fish assemblages in structure-less and homogeneous ecosystems, and to understand the mechanisms affecting habitat use and species replacement.
1. Age-related changes in reproductive effort have been predicted by theoretical models and obser... more 1. Age-related changes in reproductive effort have been predicted by theoretical models and observed in a wide range of organisms. However, for indeterminate growers such as fish, an allometric relationship linking gonad weight to body size is commonly observed. There is often a positive linear relationship when these variables are log-transformed, which by implication reduces the influence of age on reproductive effort.2. Contrasting with this usual pattern, we report a nonlinear relationship between gonad weight and fish size (after log-transformation) in mosquitofish (Gambusia holbrooki), clearly resulting from age changes. The declining rate of increase of gonad mass as a function of body size revealed a higher reproductive effort for younger individuals relative to size.3. This size-independent age effect on reproductive effort was predicted based on previous studies of mosquitofish and is certainly related to their particular life-history strategy, combining an early maturation and short lifespan with the physiological costs of reproduction and over-wintering. Our findings probably apply to other small, short-lived species with similar life history.
Studies about fish assemblages in Brazilian streams have grown in recent years, however, it remai... more Studies about fish assemblages in Brazilian streams have grown in recent years, however, it remains unclear whether this increase is followed by increments in the diversity of addressed topics and theoretical frameworks adopted by researchers. We performed a systematic search for Brazilian studies on stream fish assemblages recording study region, publication year, objectives, and spatial and temporal scales adopted. The number of studies is unevenly distributed among regions. Most papers describe the general structure of local fish assemblages and their scientific objectives have not varied through time. Studies have been conducted mainly at small temporal and spatial scales, though the latter is increasing over time. We argue for the need of focusing on recently developed ecological theories and frameworks, and expanding the temporal and spatial scales of studies. These changes will improve regional and local conservation policies, and the visibility of aquatic Brazilian research in the global scientific community.
This study aimed to establish the presence of spatial synchrony for three riverine fish populatio... more This study aimed to establish the presence of spatial synchrony for three riverine fish populations (stone loach Barbatula barbatula L., European minnow Phoxinus phoxinus L. and gudgeon Gobio gobio L.) in two spatially-close sites of the Garonne River (SW France). Sampling was carried out by electrofishing from 1994 to 1999. The fish were split into two age classes (0+ and >0+) using length-frequency distribution analysis. No autocorrelation was present in our time series. There were significant correlations of densities between sites for stone loach (>0+) and gudgeon (0+), but not for European minnow. A significant positive relationship was observed between maximal flow values and 0+ gudgeon density. No significant associations between flow variables and density were observed for stone loach. These results emphasize the role of external factors in effecting population dynamics, and suggest that their influences differ according to life stage and life-history characteristics.
1. Synchronous fluctuations of the abundance of several populations at a regional scale can be a ... more 1. Synchronous fluctuations of the abundance of several populations at a regional scale can be a sign of a climatic effect on their dynamics (Moran effect). However, the interpretation of spatial synchrony is often complicated by the interaction between climatic disturbances and migrations between the studied populations. 2. We addressed this question by studying 24-year time-series of abundance estimates for four populations of four fish species in three different catchment basins in Côte d'Ivoire (West Africa). As localities from two different basins cannot exchange individuals, dispersal cannot be considered a synchronizing factor in this system.
1. Focusing on the current environmental characteristics, the ‘habitat template’ theory proposes ... more 1. Focusing on the current environmental characteristics, the ‘habitat template’ theory proposes that life-history strategies summarise how evolution has shaped species to cope with the temporal and spatial variability of their present environment. The hierarchical ‘landscape filters’ concept predicts that the distribution of species reflects their specific traits that allow them to pass through multiple habitat filters. Together, these theories showed the importance of identifying the functional relationships of species to selective habitat forces in order to predict the organisation and response of communities to the environment.2. We test the relationships between life-history traits of European freshwater fish species’ and their habitat preferences, to detect the strategies adopted by fish to cope with their current habitat. For this purpose, we use published data on species traits and habitat preferences (microhabitat hydraulics, temperature and oxygen level). We use multivariate analyses to classify fish species’ strategies and test the relationships between strategies and habitat preferences.3. We identified a continuum of life-history patterns between two extremes, with opportunistic and periodic species. Our study supports the idea that microhabitat hydraulics plays a more important role as a template for these species ecological strategies than temperature and oxygen level. Indeed, riffle habitats may select opportunistic species whereas weak relationships are found between species strategies and both their temperature and oxygen level preferences. In addition, the ratio between mortality and growth rate (dimensionless trait), reflecting a trade-off between growth and survival, varied among species according to the use of their hydraulic habitat, with species using deep habitats exhibiting the highest values.4. These general relationships between hydraulics and traits may be of importance in community ecology to develop predictive models to understand how fish communities change with the hydraulic environment.
Body size, ecological tolerance and potential for water quality bioindication in the genus Anacro... more Body size, ecological tolerance and potential for water quality bioindication in the genus Anacroneuria (Plecoptera: Perlidae) from South America. Knowledge about the biology and ecology of neotropical aquatic taxa is crucial to establish general ecological rules and water protection systems. Based mainly on published data, the present work shows the following biological and ecological characteristics of Anacroneuria species (Klapálek 1909): a) the wide range of environmental conditions of rivers where Anacroneuria species occur, b) species number decreases along an increasing elevation gradient, c) body size increases in relation to the maximum altitude of occurrence, d) altitudinal range increases with body size, e) there is a constant relationship between male and female body size, and finally, f) larger females lay larger eggs. In temperate countries, the family Perlidae in general, and the genus Anacroneuria in particular, are viewed as excellent water quality indicators. We suggest that, considering the complexity of the group's ecology in South America, it should not be automatically considered an excellent bioindicator in the Neotropical region. Rev. Biol. Trop. 55 (1): 67-81. Epub 2007 March. 31.
Spatial synchrony in species abundance is a general phenomenon that has been found in populations... more Spatial synchrony in species abundance is a general phenomenon that has been found in populations representing virtually all major taxa. Dispersal among populations and synchronous stochastic effects (the so called “Moran effect”) are the mechanisms most likely to explain such synchrony patterns. Very few studies have related the degree of spatial synchrony to the biological characteristics of species. Here we present a case where specific predictions can be made to relate river fish species characteristics and synchrony determined exclusively by a Moran effect through the expected sensitivity of species to the regional component of environmental stochasticity. By analyzing 23-year time series of abundance estimates in two isolated localities we show that species associated with synchronized reproduction during the wet season, high fecundity, small egg size and high gonado-somatic index (the so called “periodic” strategy) have a higher degree of spatial synchrony in population dynamics than species associated with the opposite traits (the so called “equilibrium” strategy). This is supported by significant relationships (P values <0.01) between species traits and the levels of synchrony after removing taxonomical relatedness. Spatial synchrony computed from summed annual total catches by groups of species, separated into strategy types also showed a significantly higher degree of synchrony for the periodic (r=0.83) than the equilibrium (r=0.46) group. Regional hydrological variability is likely to be partly responsible for the observed synchrony pattern and a regional discharge index showed better relationships with the periodic group, supporting the expected differential effect of regional environmental correlation on population dynamics.
We explored the relationships between diet and morphology in 30 fish species from forested tropic... more We explored the relationships between diet and morphology in 30 fish species from forested tropical streams of the Bolivian Amazon. These species were first assigned to eight broad trophic guilds based on stomach contents analysis. The relationships between diet and morphology were then examined using Redundancy Analysis, after having checked for potential phylogenetical effects. Results show that, independently of any phylogenetic constraints, some of the trophic guilds could be grossly predicted from few relevant morphological attributes (i.e. relative intestinal length, standard length and mouth orientation) and thus suggest a significant link between diet and morphology. In other words, species having similar diet tend to converge to some extent on some morphological attributes. This link was nevertheless rather weak, suggesting that even if morphology may set limits to patterns of resource use, these limits are broad enough to allow fishes changing their choice of prey resources to respond to local biotic and/or abiotic conditions. Résumé -Relations entre le régime alimentaire et les caractéristiques morphologiques des peuplements de poissons de petits cours d'eau forestiers de l'Amazonie bolivienne. Nous avons analysé les relations entre le régime alimentaire et la morphologie de 30 espèces de poissons présentes dans de petits cours d'eau forestiers de l'Amazonie bolivienne. Après une analyse de leurs contenus stomacaux, les 30 espèces ont été réparties, dans un premier temps, dans huit grandes guildes trophiques. Dans un deuxième temps, après avoir analysé les éventuelles contraintes phylogénétiques, nous avons examiné, par analyse multivariée, les relations entre le régime alimentaire et la morphologie des espèces. Les résultats montrent que, indépendamment de la phylogénie, certaines des guildes trophiques peuvent être prédites d'après quelques attributs morphologiques (i.e. longueur relative de l'intestin, longueur standard et orientation de la bouche). Cela étant, ce lien entre régime alimentaire et caractéristiques morphologiques reste relativement faible, ce qui suggère que même si la morphologie limite les possibilités d'utilisation des ressources, cette limite est assez large pour permettre aux espèces de s'adapter à différentes conditions biotiques ou abiotiques locales. fishes, gut length clearly distinguish algivores, detritivores and herbivores from carnivores . However, relationships between diet and morphology are equivocal since other studies found weak and indistinct results rather relating feeding and morphological variables to local environmental factors and 132 C. Ibañez et al.: Aquat. Living Resour. 20, 131-142 (2007)
The hypothesis of convergence takes the deterministic view that community (or assemblage) structu... more The hypothesis of convergence takes the deterministic view that community (or assemblage) structure can be predicted from the environment, and that the environment is expected to drive evolution in a predictable direction. Here we present results of a comparative study of freshwater fish assemblages from headwater streams in four continents (Europe, North America, Africa and South America), with the general objective of testing whether these assemblages display convergent structures under comparable environmental conditions (i.e. assemblage position in the stream longitudinal continuum). We tested this hypothesis by comparing species richness and trophic guilds of those stream fish assemblages represented in available data from multiple sites on each continent. Independent of phylogenetic and historical constraints, fish assemblage richness and trophic structure in the four continents converged along the stream continua to a substantial degree. For the four continents, assemblage richness increased, the proportion of invertivorous species decreased, and the proportion of omnivorous species increased from upstream to downstream, supporting theoretical predictions of the river continuum concept. However, the herbivore/detritivore and piscivore guilds were virtually absent from our small European and North American stream sites, unlike our African and South American stream sites. This divergence can be linked to differences in energy availability between temperate and tropical systems.
The River Continuum Concept (RCC) explains the structural and functional characteristics of strea... more The River Continuum Concept (RCC) explains the structural and functional characteristics of stream communities focusing on the gradually changing physical components from headwaters to downstream habitats of streams and rivers. The global value of the RCC is still uncertain, possibly because physical factors (e.g., altitude and then temperature, stream order, channel width) can vary differently in longitudinal river axes across the world. Moreover, RCC predictions in relation to different physical factors have not been tested adequately in different biomes, especially biomes outside of temperate North America. Here, we report on the functional structure of macroinvertebrate communities in neotropical streams from Bolivia along a broad altitudinal gradient (from 1120 to 4300 m a.s.l.), aiming to understand how altitude can affect the longitudinal changes in functional feeding groups (FFG) and richness predicted by the RCC. The RCC predictions for functional structure were not completely matched when analyzing FFGs in relation to an index of longitudinal stream gradient. However, after removing the effect of altitude by using residuals from regressions between FFGs and altitude, FFG patterns matched RCC predictions more closely. We detected signifi cant relationships between altitude and the relative abundance of collector-gatherers, shredders and scrapers which may be related to changes in temperature, UV radiation and canopy cover along the altitudinal gradient. Our results indicate that altitude combined with position along the longitudinal gradient is an important factor governing the FFG structure of macroinvertebrate communities in neotropical streams.
Productivity (trophic energy) is one of the most important factors promoting variation in species... more Productivity (trophic energy) is one of the most important factors promoting variation in species richness. A variety of species-energy relationships have been reported, including monotonically positive, monotonically negative, or unimodal (i.e. hump-shaped). The exact form of the relationship seems to depend, among other things, on the spatial scale involved. However, the mechanisms behind these patterns are still largely unresolved, although many hypotheses have been suggested. Here we report a case of local-scale positive species-energy relationship. Using 14 local fish assemblages in tropical forested headwater streams (Bolivia), and after controlling for major local abiotic factors usually acting on assemblage richness and structure, we show that rising energy availability through leaf litter decomposition rates allows trophically specialized species to maintain viable populations and thereby to increase assemblage species richness. By deriving predictions from three popular mechanistic explanations, i.e. the 'increased population size', the 'consumer pressure', and the 'specialization' hypotheses, our data provide only equivocal support for the latter. To cite this article: P.A. Tedesco et al., C. R. Biologies 330 (2007). Résumé Relation énergie disponible/richesse spécifique chez les peuplements de poissons de cours d'eau forestiers de l'Amazonie bolivienne. L'énergie disponible dans un écosystème a depuis toujours été considérée comme une contrainte fondamentale à la richesse spécifique animale et végétale qui lui est inféodée. Différentes relations entre richesse et énergie ont été rapportées jusqu'à maintenant, incluant des relations positives, négatives ou unimodales. La forme de la relation semble dépendre, entre autres, de A u t h o r ' s p e r s o n a l c o p y 256 P.A. Tedesco et al. / C. R. Biologies 330 (2007) 255-264
The precise number of extant fish species remains to be determined. About 28,900 species were lis... more The precise number of extant fish species remains to be determined. About 28,900 species were listed in FishBase in 2005, but some experts feel that the final total may be considerably higher. Freshwater fishes comprise until now almost 13,000 species (and 2,513 genera) (including only freshwater and strictly peripheral species), or about 15,000 if all species occurring from fresh to brackishwaters are included. Noteworthy is the fact that the estimated 13,000 strictly freshwater fish species live in lakes and rivers that cover only 1% of the earth’s surface, while the remaining 16,000 species live in salt water covering a full 70%. While freshwater species belong to some 170 families (or 207 if peripheral species are also considered), the bulk of species occur in a relatively few groups: the Characiformes, Cypriniformes, Siluriformes, and Gymnotiformes, the Perciformes (noteably the family Cichlidae), and the Cyprinodontiformes. Biogeographically the distribution of strictly freshwater species and genera are, respectively 4,035 species (705 genera) in the Neotropical region, 2,938 (390 genera) in the Afrotropical, 2,345 (440 genera) in the Oriental, 1,844 (380 genera) in the Palaearctic, 1,411 (298 genera) in the Nearctic, and 261 (94 genera) in the Australian. For each continent, the main characteristics of the ichthyofauna are briefly outlined. At this continental scale, ichthyologists have also attempted to identify ichthyological ‘‘provinces’’ that are regions with a distinctive evolutionary history and hence more or less characteristic biota at the species level. Ichthyoregions are currently identified in each continent, except for Asia. An exceptionally high faunal diversity occurs in ancient lakes, where one of the most noteworthy features is the existence of radiations of species that apparently result from intra-lacustrine speciation. Numerous fish-species flocks have been identified in various ancient lakes that are exceptional natural sites for the study of speciation. The major threats to fish biodiversity are intense and have been relatively well documented: overexploitation, flow modification, destruction of habitats, invasion by exotic species, pollution including the worldwide phenomena of eutrophication and sedimentation, all of which are interacting.
Aim Documentation of the ongoing effect of rain forest refuges at the last glacial maximum (LGM)... more Aim Documentation of the ongoing effect of rain forest refuges at the last glacial maximum (LGM) on patterns of tropical freshwater fish diversity.Location Tropical South and Central America, and West Africa.Methods LGM rain forest regions and species richness by drainage were compiled from published data. GIS mapping was applied to compile drainage area and contemporary primary productivity. We used multiple regression analyses, applied separately for Tropical South America, Central America and West Africa, to assess differences in species richness between drainages that were connected and disconnected to rain forest refuge zones during the LGM. Spatial autocorrelation of the residuals was tested using Moran's I statistic. We added an intercontinental comparison to our analyses to see if a historical signal would persist even when a regional historical effect (climate at the LGM) had already been accounted for.Results Both area and history (contact with LGM rain forest refuge) explained the greatest proportions of variance in the geographical pattern of riverine species richness. In the three examined regions, we found highest richness in drainages that were connected to the rain forest refuges. No significant residual spatial autocorrelation was detected after considering area, primary productivity and LGM rain forest refuges. These results show that past climatic events still affect West African and Latin American regional and continental freshwater fish richness. At the continental scale, we found South American rivers more species-rich than expected on the basis of their area, productivity and connectedness to rain forest refuge. Conversely, Central American rivers were less species-diverse than expected by the grouped model. African rivers were intermediate. Therefore, a historical signal persists even when a regional historical effect (climate at the LGM) had already been accounted for.Main conclusions It has been hypothesized that past climatic events have limited impact on species richness because species have tracked environmental changes through range shifts. However, when considering organisms with physically constrained dispersal (such as freshwater fish), past events leave a perceptible imprint on present species diversity. Furthermore, we considered regions that have comparable contemporary climatic and environmental characteristics, explaining the absence of a productivity effect. From the LGM to the present day (a time scale of 18,000 years), extinction processes should have played a predominant role in shaping the current diversity pattern. By contrast, the continental effects could reflect historical contingencies explained by differences in speciation and extinction rates between continents at higher time scales (millions of years).
Ecology Letters (2010) 13: 421–431Ecology Letters (2010) 13: 421–431AbstractIn this study, we tes... more Ecology Letters (2010) 13: 421–431Ecology Letters (2010) 13: 421–431AbstractIn this study, we test whether established non-native species induce functional changes in natural assemblages. We combined data on the body size of freshwater fish species and a worldwide data set of native and non-native fish species for 1058 river basins. We show that non-native fish species are significantly larger than their native counterparts and are a non-random subset of the worldwide set of fish species. We further show that the median body size of fish assemblages increases in the course of introductions. These changes are the opposite of those expected under several null models. Introductions shift body size patterns related to several abiotic factors (e.g. glacier coverage and temperature) in a way that modifies latitudinal patterns (i.e. Bergmann’s rule), especially in the southern hemisphere. Together, these results show that over just the last two centuries human beings have induced changes in the global biogeography of freshwater fish body size, which could affect ecosystem properties.In this study, we test whether established non-native species induce functional changes in natural assemblages. We combined data on the body size of freshwater fish species and a worldwide data set of native and non-native fish species for 1058 river basins. We show that non-native fish species are significantly larger than their native counterparts and are a non-random subset of the worldwide set of fish species. We further show that the median body size of fish assemblages increases in the course of introductions. These changes are the opposite of those expected under several null models. Introductions shift body size patterns related to several abiotic factors (e.g. glacier coverage and temperature) in a way that modifies latitudinal patterns (i.e. Bergmann’s rule), especially in the southern hemisphere. Together, these results show that over just the last two centuries human beings have induced changes in the global biogeography of freshwater fish body size, which could affect ecosystem properties.
We provide mitochondrial sequence variation of the invasive fish Gambusia holbrooki from 24 Europ... more We provide mitochondrial sequence variation of the invasive fish Gambusia holbrooki from 24 European populations, from Portugal to Greece. Phylogeographic structure in Europe was compared with genetic data from native samples (USA) and historical records were reviewed to identify introduction routes. Overall, data agree with records of historical introductions and translocations, and indicate that the most abundant haplotype throughout Europe originated from North Carolina and corresponded to the first introduction in 1921 to Spain, being transferred to Italy in 1922 and to many countries afterwards. Our results also show that at least another independent introduction occurred first in France and subsequently from France to Greece. Haplotypes of G. affinis were not detected in our European sampling effort but historical records and other data suggest that this species was introduced to Italy in 1927 and it might be present. At the continental scale, there is less diversity in Europe than in North America, in agreement with the low number of introduced fish. At the local scale, some European populations gained diversity from multiple introductions and from “de novo” mutations.
Aim To identify key research questions and challenges that will, if addressed in a timely manner... more Aim To identify key research questions and challenges that will, if addressed in a timely manner, significantly advance the field of freshwater fish biogeography and conservation.Location Globe.Methods By drawing on expertise from different regions of the world, we integrate an illustrative conspectus of recent scientific advancements in fish biogeography with a prospectus of needed areas of scientific inquiry to identify information gaps and priority research needs to advance the science.Results We identified the following core challenges: (1) Testing current and forging new theories in biogeography; (2) Advancing a trait-based biogeography of freshwater fishes; (3) Quantifying extinction risk and loss of fish species in a changing environment; (4) Evaluating the magnitude and geography of extinction debt for freshwater fishes; (5) Elucidating the patterns and drivers of freshwater fish invasions; (6) Forecasting the future geography of freshwater fishes; (7) Understanding the interactive effects of multiple stressors in freshwater ecosystems; (8) Quantifying new features of the biodiversity crisis: fish faunal homogenization and the emergence of novel assemblages; (9) Promoting scientific rigour in emerging freshwater fish conservation strategies and (10) Improving conservation planning strategies for freshwater fish species.Main conclusions By reflecting on recent scientific progress in fish conservation biogeography, we have identified a set of core challenges and priorities requiring future research investment.
Artificial macrophytes were experimentally deployed in Boadella Reservoir (NE Spain) and assessed... more Artificial macrophytes were experimentally deployed in Boadella Reservoir (NE Spain) and assessed for fish use throughout the first 3 months of the 2007 summer drawdown. In total, 1,832 individuals of seven fish species were recorded through visual censuses, with introduced perch Perca fluviatilis being the prevalent species. Fish richness and abundance were significantly higher in artificial macrophytes than in rocky shores and sandy beaches, displaying a unimodal variation through time. P. fluviatilis, Rutilus rutilus and Abramis brama were significantly more abundant in artificial macrophytes than in the other two naturally submersed habitats, where no individuals of these species were recorded. The abundances of Squalius laietanus, Lepomis gibbosus, Micropterus salmoides and Cyprinus carpio were overall greater in artificial macrophytes than in rocky shores but displayed significant habitat × time interactions. A decrease in predation risk was apparently the key-factor of the intensive use of artificial macrophytes by small fish (≤100 mm TL) in Boadella Reservoir, since most species reduced drastically or completely the use of submerged structures when body size increased. This study demonstrates that adding artificial structures mimicking aquatic macrophytes can be an interesting tool to mitigate the adverse effects of water level fluctuations on fish assemblages in structure-less and homogeneous ecosystems, and to understand the mechanisms affecting habitat use and species replacement.
1. Age-related changes in reproductive effort have been predicted by theoretical models and obser... more 1. Age-related changes in reproductive effort have been predicted by theoretical models and observed in a wide range of organisms. However, for indeterminate growers such as fish, an allometric relationship linking gonad weight to body size is commonly observed. There is often a positive linear relationship when these variables are log-transformed, which by implication reduces the influence of age on reproductive effort.2. Contrasting with this usual pattern, we report a nonlinear relationship between gonad weight and fish size (after log-transformation) in mosquitofish (Gambusia holbrooki), clearly resulting from age changes. The declining rate of increase of gonad mass as a function of body size revealed a higher reproductive effort for younger individuals relative to size.3. This size-independent age effect on reproductive effort was predicted based on previous studies of mosquitofish and is certainly related to their particular life-history strategy, combining an early maturation and short lifespan with the physiological costs of reproduction and over-wintering. Our findings probably apply to other small, short-lived species with similar life history.
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Papers by Pablo Tedesco