Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 39
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
J Environ Manage ; 347: 119197, 2023 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-37797520

RESUMO

Due to global changes, e.g., climate change and trade globalization, China is facing an increasingly severe threat from invasive freshwater fish species, which have the potential to cause negative impacts across various aspects and pose significant challenges for their eradication once established. Therefore, prioritizing the understanding of invasive species' potential ranges and their determinants is vital for developing more targeted management strategies. Moreover, it is equally essential to consider the transitory range dynamics of invasive species that reflect changes in habitat availability and accessibility. Here, we used species distribution models (the maximum entropy algorithm) to assess the potential distributions of six notorious invasive fish species (i.e., Coptodon zillii, Cyprinus carpio, Gambusia affinis, Hemiculter leucisculus, Oreochromis mossambicus, and Oreochromis niloticus) in current and future (i.e., the 2030s, 2050s, and 2070s) periods along with their determinants, under two Shared Socio-economic Pathways scenarios (SSP1-2.6 and SSP5-8.5; global climate model: MRI-ESM2-0). Our results showed that the habitat suitability for the six species substantially benefited from temperature conditions (i.e., annual mean temperature or maximum temperature of warmest month). Throughout the given time periods, dramatic range expansions would occur for C. zillii, G. affinis, O. mossambicus, and O. niloticus, ranging from 38.61% to 291.90%. In contrast, the range of C. carpio would change slightly and irregularly, while H. leucisculus would contract marginally, with losses ranging from 1.06% to 12.60%. By the 2070s, species richness of these species would be relatively high in South, Central, and East China and parts of Southwest China. Furthermore, transitory fluctuations in the species ranges for all six species were observed throughout the entire time period (the 2030s-2070s). Given the range shifts for each species during different time periods, as well as time costs and budgets, adaptation strategies should be developed and implemented in the areas where they are most needed in each time period.


Assuntos
Carpas , Espécies Introduzidas , Animais , Ecossistema , China , Mudança Climática
2.
J Environ Manage ; 344: 118374, 2023 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-37331311

RESUMO

Over the past centuries, freshwater fish introductions and extinctions have been the major environmental and ecological crises in various water bodies in China. However, consequences of such crises on freshwater fish biodiversity in China remain only partially or locally studied. Furthermore, identifications of relatively sensitive areas along with stressors (i.e., environmental and anthropogenic drivers) influencing freshwater fish biodiversity patterns are still pending. Taxonomic, functional, and phylogenetic facets of biodiversity can well describe and evaluate the underlying processes affecting freshwater fish biodiversity patterns under different dimensionalities. Here we thus evaluated temporal changes in these facets of freshwater fish biodiversity as well as a new developed biodiversity index, multifaceted changes in fish biodiversity, for over a century at the basin level throughout China using both alpha and beta diversity approaches. We also identified the drivers influencing the changes in fish biodiversity patterns using random forest models. The results showed that fish assemblages in Northwest and Southwest China (e.g., Ili River basin, Tarim basin, and Erhai Lake basin) experienced extreme temporal and multifaceted changes in the facets of biodiversity compared with other regions, and environmental factors (e.g., net primary productivity, average annual precipitation, and unit area) largely drove these changes. Since fish faunas in over 80% of China's water bodies covering more than 80% of China's surface were currently undergoing taxonomic, functional, and phylogenetic homogenization, targeted conservation and management strategies should be proposed and implemented, especially for the areas with relatively high changes in biodiversity.


Assuntos
Efeitos Antropogênicos , Biodiversidade , Animais , Filogenia , Lagos , Peixes , China , Água , Ecossistema
3.
Sci Total Environ ; 891: 164624, 2023 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-37277043

RESUMO

Overexploitation, habitat fragmentation, and flow alteration are major threats to freshwater biodiversity that can lead to fisheries collapse and species extinction. These threats are particularly alarming in poorly monitored ecosystems where resource use supports the livelihoods of numerous people. The Tonle Sap Lake in Cambodia is such an ecosystem, supporting one of the world's largest freshwater fisheries. Tonle Sap Lake fishes are the focus of indiscriminate harvest affecting species stocks, community composition and food-web structure. Changes in the magnitude and timing of the seasonal flood pulse have also been linked to declines in fish stocks. Yet, changes in fish abundance and species-specific temporal trends remain poorly documented. Analyzing 17 years' time series of fish catch data for 110 species, we show that fish populations have declined by 87.7 %, owing to a statistically significant decline for >74 % species, particularly the largest ones. Despite large variations in species-specific trends - going from locally extinct to >1000 % increase - declines were found across most migratory behaviors, trophic positions or IUCN threat categories, though uncertainty regarding the magnitude of effect precluded us drawing conclusions in some cases. These results, reminiscent of alarming declines in fish stocks in many marine fisheries, provide unequivocal evidence that Tonle Sap fish stocks are increasingly depleted. The consequences of this depletion on ecosystem function are unknown but will undoubtedly affect the livelihoods of millions of people, stressing the need to set-up management strategies aimed to protect both the fishery and its associated diversity. Flow alteration, habitat degradation / fragmentation - especially deforestation of seasonally inundated areas and overharvest - have been reported as major drivers in population dynamics and community structure, highlighting the need for management efforts aimed at preserving the natural flood pulse, protecting flooded forest habitats, and reducing overfishing.


Assuntos
Ecossistema , Pesqueiros , Animais , Conservação dos Recursos Naturais/métodos , Lagos , Peixes
4.
Nat Ecol Evol ; 7(7): 1072-1078, 2023 07.
Artigo em Inglês | MEDLINE | ID: mdl-37264200

RESUMO

Climate warming can negatively affect the body size of ectothermic organisms and, based on known temperature-size rules, tends to benefit small-bodied organisms. Our understanding of the interactive effects of climate warming and other environmental factors on the temporal changes of body size structure is limited. We quantified the annual trends in size spectra of 583 stream fish communities sampled for more than 20 years across France. The results show that climate warming steepened the slope of the community size spectrum in streams with limited impacts from other human pressures. These changes were caused by increasing abundance of small-bodied individuals and decreasing abundance of large-bodied individuals. However, opposite effects of climate warming on the size spectrum slopes were observed in streams facing high levels of other human pressures. This demonstrates that the effects of temperature on body size structure can depend on other human pressures, disrupting the natural patterns of size spectra in wild communities with potentially strong implications for the fluxes of energy and nutrients in ecosystems.


Assuntos
Ecossistema , Rios , Animais , Humanos , Peixes , Mudança Climática , Temperatura
5.
Ecol Appl ; 33(4): e2845, 2023 06.
Artigo em Inglês | MEDLINE | ID: mdl-36922403

RESUMO

Evaluating the effects of anthropogenic pressures on several biodiversity metrics can inform the management and monitoring of biodiversity loss. However, the type of disturbances can lead to different responses in different metrics. In this study, we aimed at disentangling the effects of different types of anthropogenic disturbances on freshwater fish communities. We calculated diversity indices for 1109 stream fish communities across France by computing richness and evenness components for ecological, morphological, and phylogenetic diversity, and used null models to estimate standardized effect sizes. We used generalized linear mixed models to assess the relative effects of environmental and anthropogenic drivers in driving those diversity indices. Our results demonstrated that all diversity indices exhibited significant responses to both climatic conditions and anthropogenic disturbances. While we observed a decrease of ecological and phylogenetic richness with the intensity of disturbance, a weak increase in morphological richness and evenness was apparent. Overall, our results demonstrated the importance of disentangling various types of disturbances when assessing human-induced ecological impacts and highlighted that different facets of diversity are not impacted identically by anthropogenic disturbances in stream fish communities. This calls for further work seeking to integrate biodiversity responses to human disturbances into a multifaceted framework, and could have beneficial implications when planning conservation action in freshwater ecosystems.


Assuntos
Biodiversidade , Ecossistema , Animais , Humanos , Filogenia , Água Doce , Rios , Peixes/fisiologia
6.
PeerJ ; 10: e12857, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35228906

RESUMO

BACKGROUND: Population dynamics are driven by a number of biotic (e.g., density-dependence) and abiotic (e.g., climate) factors whose contribution can greatly vary across study systems (i.e., populations). Yet, the extent to which the contribution of these factors varies across populations and between species and whether spatial patterns can be identified has received little attention. METHODS: Here, we used a long-term (1982-2011), broad scale (182 sites distributed across metropolitan France) dataset to study spatial patterns in the population's dynamics of three freshwater fish species presenting contrasted life-histories and patterns of elevation range shifts in recent decades. We used a hierarchical Bayesian approach together with an elasticity analysis to estimate the relative contribution of a set of biotic (e.g., strength of density dependence, recruitment rate) and abiotic (mean and variability of water temperature) factors affecting the site-specific dynamic of two different size classes (0+ and >0+ individuals) for the three species. We then tested whether the local contribution of each factor presented evidence for biogeographical patterns by confronting two non-mutually exclusive hypotheses: the "range-shift" hypothesis that predicts a gradient along elevation or latitude and the "abundant-center" hypothesis that predicts a gradient from the center to the edge of the species' distributional range. RESULTS: Despite contrasted life-histories, the three species displayed similar large-scale patterns in population dynamics with a much stronger contribution of biotic factors over abiotic ones. Yet, the contribution of the different factors strongly varied within distributional ranges and followed distinct spatial patterns. Indeed, while abiotic factors mostly varied along elevation, biotic factors-which disproportionately contributed to population dynamics-varied along both elevation and latitude. CONCLUSIONS: Overall while our results provide stronger support for the range-shift hypothesis, they also highlight the dual effect of distinct factors on spatial patterns in population dynamics and can explain the overall difficulty to find general evidence for geographic gradients in natural populations. We propose that considering the separate contribution of the factors affecting population dynamics could help better understand the drivers of abundance-distribution patterns.


Assuntos
Clima , Ecossistema , Animais , Teorema de Bayes , Água Doce , Dinâmica Populacional , Peixes
7.
J Environ Manage ; 284: 111998, 2021 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-33540195

RESUMO

Considering local adaptation has been increasingly involved in forecasting species distributions under climate change and the management of species conservation. Herein, we take the critically endangered Chinese giant salamander (Andrias davidianus) that has both a low dispersal ability and distinct population divergence in different regions as an example. Basin-scale models that represent different populations in the Huanghe River Basin (HRB), the Yangtze River Basin (YRB), and the Pearl River Basin (PRB) were established using ensemble species distribution models. The species ranges under the future human population density (HPD) and climate change were predicted, and the range loss was evaluated for local basins in 2050 and 2070. Our results showed that the predominant factors affecting species distributions differed among basins, and the responses of the species occurrence to HPD and climate factors were distinctly different from northern to southern basins. Future HPD changes would be the most influential factor that engenders negative impacts on the species distribution in all three basins, especially in the HRB. Climate change will likely be less prominent in decreasing the species range, excluding in the YRB and PRB under the highest-emissions scenario in 2050. Overall, the high-emissions scenario would more significantly aggravate the negative impacts produced by HPD change in both 2050 and 2070, with maximum losses of species ranges in the HRB, YRB, and PRB of 83.4%, 60.0%, and 53.5%, respectively, under the scenarios of the combined impacts of HPD and climate changes. We proposed adapted conservation policies to effectively protect the habitat of this critically endangered animal in different basins based on the outcomes. Our research addresses the importance of incorporating local adaptation into species distribution modeling to inform conservation and management decisions.


Assuntos
Mudança Climática , Espécies em Perigo de Extinção , Aclimatação , Animais , Conservação dos Recursos Naturais , Ecossistema , Humanos , Rios
9.
Science ; 370(6520)2020 11 27.
Artigo em Inglês | MEDLINE | ID: mdl-33243858

RESUMO

Zellweger et al (Reports, 15 May 2020, p. 772) claimed that forest plant communities' response to global warming is primarily controlled by microclimate dynamics. We show that community thermophilization is poorly explained by the underlying components of microclimate, and that global warming primarily controls the climatic lag of plant communities. Deconstructing the underlying components of microclimate provides insights for managers.


Assuntos
Florestas , Microclima , Aquecimento Global , Plantas
10.
Sci Total Environ ; 735: 139543, 2020 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-32485455

RESUMO

The Chinese giant salamander, Andrias davidianus, the world's largest amphibian, is critically endangered and has an extremely unique evolutionary history. Therefore, this species represents a global conservation priority and will be impacted by future climate and human pressures. Understanding the range and response to environmental change of this species is a priority for the identification of targeted conservation activities. We projected future range shifts of the Chinese giant salamander under the independent and combined impacts of climate change and human population density (HPD) variations by using ensemble species distribution models. We further evaluated the sustainability of existing nature reserves and identified priority areas for the mitigation or prevention of such pressures. Both climate change and increasing HPD tended to reduce the species range, with the latter leading to greater range losses and fragmentation of the range. Notably, 65.6%, 18.0% and 18.4% of the range loss were attributed solely to HPD change, solely to climate change and to their overlapping impacts, respectively. Overall, the average total and net losses of the species range were 52.5% and 23.4%, respectively, and HPD and climate changes were responsible for 71.4% and 28.6% of the net losses, respectively. We investigated the stability of the remaining species range and found that half of the nature reserves are likely vulnerable, with 57.1% and 66.7% of them likely to lose their conservation value in 2050 and 2070, respectively. To effectively protect this salamander, conservation policies should address both pressures simultaneously, especially considering the negative impact of human pressures in both contemporary periods and the near future. The species range shifts over space and time projected by this research could help guide long-term surveys and the sustainable conservation of wild habitats and populations of this ancient and endangered amphibian.


Assuntos
Mudança Climática , Conservação dos Recursos Naturais , Anfíbios , Animais , Ecossistema , Espécies em Perigo de Extinção , Humanos , Urodelos
11.
Nat Ecol Evol ; 4(8): 1044-1059, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32451428

RESUMO

There is mounting evidence of species redistribution as climate warms. Yet, our knowledge of the coupling between species range shifts and isotherm shifts remains limited. Here, we introduce BioShifts-a global geo-database of 30,534 range shifts. Despite a spatial imbalance towards the most developed regions of the Northern Hemisphere and a taxonomic bias towards the most charismatic animals and plants of the planet, data show that marine species are better at tracking isotherm shifts, and move towards the pole six times faster than terrestrial species. More specifically, we find that marine species closely track shifting isotherms in warm and relatively undisturbed waters (for example, the Central Pacific Basin) or in cold waters subject to high human pressures (for example, the North Sea). On land, human activities impede the capacity of terrestrial species to track isotherm shifts in latitude, with some species shifting in the opposite direction to isotherms. Along elevational gradients, species follow the direction of isotherm shifts but at a pace that is much slower than expected, especially in areas with warm climates. Our results suggest that terrestrial species are lagging behind shifting isotherms more than marine species, which is probably related to the interplay between the wider thermal safety margin of terrestrial versus marine species and the more constrained physical environment for dispersal in terrestrial versus marine habitats.


Assuntos
Mudança Climática , Clima , Animais , Ecossistema , Oceanos e Mares , Plantas
12.
Sci Total Environ ; 711: 134661, 2020 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-31812402

RESUMO

Invasive species have imposed huge negative impacts on worldwide aquatic ecosystems and are generally difficult or impossible to be eradicated once established. Consequently, it becomes particularly important to ascertain their invasion risk and its determinants since such information can help us formulate more effective preventive or management actions and direct these measures to those areas where they are truly needed so as to ease regulatory burdens. Here, we examined the global invasion risk and its determinants of sharpbelly (Hemiculter leucisculus), one freshwater fish which has a high invasive potential, by using species distribution models (SDMs) and a layer overlay method. Specifically, first an ensemble species distribution model and its basal models (developed from seven machine learning algorithms) were explored to forecast the global habitat-suitability and variables importance for this species, and then a global invasion risk map was created by combining habitat-suitability with a proxy for introduction likelihood (entailing propagule pressure and dispersal constraints) of exotic sharpbelly. The results revealed that (1) the ensemble model had the highest predictive power in forecasting sharpbelly's global habitat-suitability; (2) areas with high invasion risk by sharpbelly patchily spread over the world except Antarctica; and (3) the Human Influence Index (HII), rather than any of the bioclimatic variables, was the most important factor influencing sharpbelly' future invasion. Based on these results, the present study also attempted to propose a series of prevention and management strategies to eliminate or alleviate the adverse effects caused by this species' further expansion.


Assuntos
Cyprinidae , Espécies Introduzidas , Animais , Regiões Antárticas , Ecossistema , Água Doce , Humanos
13.
Proc Natl Acad Sci U S A ; 116(27): 13434-13439, 2019 07 02.
Artigo em Inglês | MEDLINE | ID: mdl-31209040

RESUMO

Identifying the drivers and processes that determine globally the geographic range size of species is crucial to understanding the geographic distribution of biodiversity and further predicting the response of species to current global changes. However, these drivers and processes are still poorly understood, and no ecological explanation has emerged yet as preponderant in explaining the extent of species' geographical range. Here, we identify the main drivers of the geographic range size variation in freshwater fishes at global and biogeographic scales and determine how these drivers affect range size both directly and indirectly. We tested the main hypotheses already proposed to explain range size variation, using geographic ranges of 8,147 strictly freshwater fish species (i.e., 63% of all known species). We found that, contrary to terrestrial organisms, for which climate and topography seem preponderant in determining species' range size, the geographic range sizes of freshwater fishes are mostly explained by the species' position within the river network, and by the historical connection among river basins during Quaternary low-sea-level periods. Large-ranged fish species inhabit preferentially lowland areas of river basins, where hydrological connectivity is the highest, and also are found in river basins that were historically connected. The disproportionately high explanatory power of these two drivers suggests that connectivity is the key component of riverine fish geographic range sizes, independent of any other potential driver, and indicates that the accelerated rates in river fragmentation might strongly affect fish species distribution and freshwater biodiversity.


Assuntos
Peixes , Animais , Biodiversidade , Demografia , Ecossistema , Água Doce , Geografia , Hidrologia , Rios
14.
PeerJ ; 7: e6772, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31011492

RESUMO

Despite being the most dominant and widespread small fish species in the lakes along the middle and lower reaches of the Yangtze River basin, Toxabramis swinhonis has been paid little attention by fisheries scientists and little is known about its population characteristics. For this reason, we estimated age, growth, mortality and recruitment of this species based on three shallow lakes, Biandantang Lake, Shengjin Lake and Kuilei Lake (BDT, SJH and KLH, respectively) in this region. A total of 13,585 (8,818 in BDT, 2,207 in SJH and 2,560 in KLH) individuals were collected during monthly sampling from July 2016 to September 2017. The results revealed that the age structures of T. swinhonis consisted of four age groups (0+-3+), with 0+-1+ year old fish comprising more than 98% of the samples. Allometric growth patterns were displayed by fish from all sampling sites and the von Bertalanffy growth functions estimated were L t = 173.25 (1 - e-1.20 (t + 1.09)): BDT; L t = 162.75 (1 - e-1.20 (t + 1.08)): SJH and L t = 215.25 (1 - e-1.20 (t + 1.12)): KLH, respectively. The rates of total mortality (Z), natural mortality (M) and fishing mortality (F) at BDT, SJH and KLH were computed as 5.82, 5.50 and 4.55 year-1; 1.89, 1.87 and 1.75 year-1; 3.93, 3.63 and 2.80 year-1, respectively. Meanwhile, growth performance indices (φ') were 0.68 (in BDT), 0.66 (in SJH) and 0.62 (in KLH), which indicated that T. swinhonis were overfished slightly in all study areas. Area-specific recruitment patterns were similar to each other, displaying evidence of batch spawning, with major peaks in April and August, accounting for 92.21% (BDT), 88.21% (SJH) and 88.73% (KLH) of total recruitment, respectively. These results showed that brief generation-time, fast growth rate, relatively high natural mortality rate and strong reproductive capacity (r-strategies) are reasons why this species became the most dominant species in many lakes of China.

15.
Mol Ecol Resour ; 19(1): 27-46, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-29768738

RESUMO

Determining the species compositions of local assemblages is a prerequisite to understanding how anthropogenic disturbances affect biodiversity. However, biodiversity measurements often remain incomplete due to the limited efficiency of sampling methods. This is particularly true in freshwater tropical environments that host rich fish assemblages, for which assessments are uncertain and often rely on destructive methods. Developing an efficient and nondestructive method to assess biodiversity in tropical freshwaters is highly important. In this study, we tested the efficiency of environmental DNA (eDNA) metabarcoding to assess the fish diversity of 39 Guianese sites. We compared the diversity and composition of assemblages obtained using traditional and metabarcoding methods. More than 7,000 individual fish belonging to 203 Guianese fish species were collected by traditional sampling methods, and ~17 million reads were produced by metabarcoding, among which ~8 million reads were assigned to 148 fish taxonomic units, including 132 fish species. The two methods detected a similar number of species at each site, but the species identities partially matched. The assemblage compositions from the different drainage basins were better discriminated using metabarcoding, revealing that while traditional methods provide a more complete but spatially limited inventory of fish assemblages, metabarcoding provides a more partial but spatially extensive inventory. eDNA metabarcoding can therefore be used for rapid and large-scale biodiversity assessments, while at a local scale, the two approaches are complementary and enable an understanding of realistic fish biodiversity.


Assuntos
Biodiversidade , Código de Barras de DNA Taxonômico/métodos , DNA/genética , DNA/isolamento & purificação , Peixes/classificação , Água Doce/química , Metagenômica/métodos , Animais , DNA/química , Peixes/genética , Guiana
16.
Ecol Lett ; 21(11): 1649-1659, 2018 11.
Artigo em Inglês | MEDLINE | ID: mdl-30187690

RESUMO

Global spread of non-native species profoundly changed the world biodiversity patterns, but how it translates into functional changes remains unanswered at the world scale. We here show that while in two centuries the number of fish species per river increased on average by 15% in 1569 basins worldwide, the diversity of their functional attributes (i.e. functional richness) increased on average by 150%. The inflation of functional richness was paired with changes in the functional structure of assemblages, with shifts of species position toward the border of the functional space of assemblages (i.e. increased functional divergence). Non-native species moreover caused shifts in functional identity toward higher body sized and less elongated species for most of assemblages throughout the world. Although varying between rivers and biogeographic realms, such changes in the different facets of functional diversity might still increase in the future through increasing species invasion and may further modify ecosystem functioning.


Assuntos
Biodiversidade , Peixes , Espécies Introduzidas , Animais , Ecossistema , Água Doce , Rios
17.
Sci Rep ; 8(1): 10058, 2018 07 03.
Artigo em Inglês | MEDLINE | ID: mdl-29968797

RESUMO

Climate change metrics have been used to quantify the exposure of geographic areas to different facets of change and relate these facets to different threats and opportunities for biodiversity at a global scale. In parallel, a suite of indicators have been developed to detect approaching transitions between alternative stable states in ecological systems at a local scale. Here, we explore whether particular geographic areas over the world display evidence for upcoming critical transitions in the temperature regime using five Early Warning Indicators (EWIs) commonly used in the literature. Although all EWIs revealed strong spatial variations regarding the likelihood of approaching transitions we found differences regarding the strength and the distribution of trends across the world, suggesting either that different mechanisms might be at play or that EWIs differ in their ability to detect approaching transitions. Nonetheless, a composite EWI, constructed from individual EWIs, showed congruent trends in several areas and highlighted variations across latitudes, between marine and terrestrial systems and among ecoregions within systems. Although the underlying mechanisms are unclear, our results suggest that some areas over the world might change toward an alternative temperature regime in the future with potential implications for the organisms inhabiting these areas.

18.
Sci Rep ; 8(1): 8947, 2018 06 12.
Artigo em Inglês | MEDLINE | ID: mdl-29895943

RESUMO

While human impacts like fishing have altered marine food web composition and body size, the status of the world's important tropical inland fisheries remains largely unknown. Here, we look for signatures of human impacts on the indiscriminately fished Tonle Sap fish community that supports one of the world's largest freshwater fisheries. By analyzing a 15-year time-series (2000-2015) of fish catches for 116 species obtained from an industrial-scale 'Dai' fishery, we find: (i) 78% of the species exhibited decreasing catches through time; (ii) downward trends in catches occurred primarily in medium to large-bodied species that tend to occupy high trophic levels; (iii) a relatively stable or increasing trend in catches of small-sized species, and; (iv) a decrease in the individual fish weights and lengths for several common species. Because total biomass of the catch has remained remarkably resilient over the last 15 years, the increase in catch of smaller species has compensated for declines in larger species. Our finding of sustained production but altered community composition is consistent with predictions from recent indiscriminate theory, and gives a warning signal to fisheries managers and conservationists that the species-rich Tonle Sap is being affected by heavy indiscriminate fishing pressure.


Assuntos
Biomassa , Ecossistema , Pesqueiros/estatística & dados numéricos , Peixes/fisiologia , Cadeia Alimentar , Animais , Camboja , Conservação dos Recursos Naturais/estatística & dados numéricos , Conservação dos Recursos Naturais/tendências , Pesqueiros/tendências , Peixes/classificação , Humanos , Lagos , Dinâmica Populacional
19.
Glob Chang Biol ; 24(9): 4417-4427, 2018 09.
Artigo em Inglês | MEDLINE | ID: mdl-29788536

RESUMO

Ecological theory suggests that communities are not random combinations of species but rather the results of community assembly processes filtering and sorting species that are able to coexist together. To date, such processes (i.e., assembly rules) have been inferred from observed spatial patterns of biodiversity combined with null model approaches, but relatively few attempts have been made to assess how these processes may be changing through time. Specifically, in the context of the ongoing biodiversity crisis and global change, understanding how processes shaping communities may be changing and identifying the potential drivers underlying these changes become increasingly critical. Here, we used time series of 460 French freshwater fish communities and assessed both functional and phylogenetic diversity patterns to determine the relative importance of two key assembly rules (i.e., habitat filtering and limiting similarity) in shaping these communities over the last two decades. We aimed to (a) describe the temporal changes in both functional and phylogenetic diversity patterns, (b) determine to what extent temporal changes in processes inferred through the use of standardized diversity indices were congruent, and (c) test the relationships between the dynamics of assembly rules and both climatic and biotic drivers. Our results revealed that habitat filtering, although already largely predominant over limiting similarity, became more widespread over time. We also highlighted that phylogenetic and trait-based approaches offered complementary information about temporal changes in assembly rules. Finally, we found that increased environmental harshness over the study period (especially higher seasonality of temperature) led to an increase in habitat filtering and that biological invasions increased functional redundancy within communities. Overall, these findings underlie the need to develop temporal perspectives in community assembly studies, as understanding ongoing temporal changes could provide a better vision about the way communities could respond to future global changes.


Assuntos
Biota , Ecossistema , Peixes/fisiologia , Filogenia , Animais , França , Água Doce , Modelos Biológicos , Dinâmica Populacional , Estações do Ano
20.
Proc Biol Sci ; 285(1877)2018 04 25.
Artigo em Inglês | MEDLINE | ID: mdl-29695444

RESUMO

Intraspecific diversity informs the demographic and evolutionary histories of populations, and should be a main conservation target. Although approaches exist for identifying relevant biological conservation units, attempts to identify priority conservation areas for intraspecific diversity are scarce, especially within a multi-specific framework. We used neutral molecular data on six European freshwater fish species (Squalius cephalus, Phoxinus phoxinus, Barbatula barbatula, Gobio occitaniae, Leuciscus burdigalensis and Parachondrostoma toxostoma) sampled at the riverscape scale (i.e. the Garonne-Dordogne river basin, France) to determine hot- and coldspots of genetic diversity, and to identify priority conservation areas using a systematic conservation planning approach. We demonstrate that systematic conservation planning is efficient for identifying priority areas representing a predefined part of the total genetic diversity of a whole landscape. With the exception of private allelic richness (PA), classical genetic diversity indices (allelic richness, genetic uniqueness) were poor predictors for identifying priority areas. Moreover, we identified weak surrogacies among conservation solutions found for each species, implying that conservation solutions are highly species-specific. Nonetheless, we showed that priority areas identified using intraspecific genetic data from multiple species provide more effective conservation solutions than areas identified for single species or on the basis of traditional taxonomic criteria.


Assuntos
Conservação dos Recursos Naturais/métodos , Peixes/genética , Variação Genética , Animais , Ecossistema , França
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...