Freshwater mussel (Mollusca: Bivalvia: Unionoida) richness and endemism in the ecoregions of Africa and Madagascar based on comprehensive museum sampling

The objective of this study was to assess freshwater mussel (Mollusca: Bivalvia: Unionoida) species distributions among the freshwater ecoregions of Africa and Madagascar to discover areas of high richness and endemism. These are among the top criteria for identifying biodiversity hotspots and establishing conservation priorities. Distributions were determined from museum specimens in 17 collections. In total, 5,612 records for 87 unionoid species could each be assigned to one of 90 freshwater ecoregions. The majority of species (55%) are known from only one (34 spp.) or two (14) ecoregions. Only three are known from more than 20 ecoregions: Etheria elliptica (38 ecoregions), Chambardia wahlbergi (25), and Mutela rostrata (21). The most species-rich ecoregions are Lake Victoria Basin (17 spp.), Upper Nile (16), Upper Congo (14), Senegal–Gambia (13), and Sudanic Congo–Oubangi (13). Those with the most endemic species are Lake Tanganyika (8 spp.), Lake Victoria Basin (6), Bangweulu–Mweru (4), and Lake Malawi (3). Twenty-five ecoregions have no known freshwater mussels. These patterns are significantly correlated with fish and general freshwater mollusk richness. Unionoid richness also varies significantly among major habitat types. These patterns are relevant to biogeography and conservation and indicate areas in need of further research. We argue that freshwater mussels are valuable as focal species for conservation assessments, and they themselves merit management consideration for their ecosystem functions and distributions in imperiled habitats. It is recommended that field surveys be conducted to determine the current status of species in all areas of Africa and Madagascar.     

The global decline of freshwater megafauna

Freshwater ecosystems are among the most diverse and dynamic ecosystems on Earth. At the same time, they are among the most threatened ecosystems but remain underrepresented in biodiversity research and conservation efforts. The rate of decline of vertebrate populations is much higher in freshwaters than in terrestrial or marine realms. Freshwater megafauna (i.e., freshwater animals that can reach a body mass ≥30 kg) are intrinsically prone to extinction due to their large body size, complex habitat requirements and slow life‐history strategies such as long life span and late maturity. However, population trends and distribution changes of freshwater megafauna, at continental or global scales, remain unclear. In the present study, we compiled population data of 126 freshwater megafauna species globally from the Living Planet Database and available literature, and distribution data of 44 species inhabiting Europe and the United States from literature and databases of the International Union for Conservation of Nature and NatureServe. We quantified changes in population abundance and distribution range of freshwater megafauna species. Globally, freshwater megafauna populations declined by 88% from 1970 to 2012, with the highest declines in the Indomalaya and Palearctic realms (?99% and ?97%, respectively). Among taxonomic groups, mega‐fishes exhibited the greatest global decline (?94%). In addition, freshwater megafauna experienced major range contractions. For example, distribution ranges of 42% of all freshwater megafauna species in Europe contracted by more than 40% of historical areas. We highlight the various sources of uncertainty in tracking changes in populations and distributions of freshwater megafauna, such as the lack of monitoring data and taxonomic and spatial biases. The detected trends emphasize the critical plight of freshwater megafauna globally and highlight the broader need for concerted, targeted and timely conservation of freshwater biodiversity.     

Spatio-temporal changes in habitat potential of endangered freshwater fish in Japan

In recent years, biodiversity conservation and ecosystem restoration have been key issues of watershed management in many countries. To maintain or restore the environmental quality of watersheds, we need to assess the impact of anthropogenic changes on stream ecosystems with accuracy. In addition, watershed conservation planners have to make strategic plans and determine priorities of each conservation activity.

A new monitoring methodology to evaluate the change of habitat condition for freshwater fish based on a predictive habitat model using logistic regression was developed and applied to the whole of Japan. The main contributions of our approach were 1) the construction of a Geographical Information System (GIS) database that integrates many types of data, including freshwater fish species, water quality, habitat fragmentation by damming, geology, and climate; 2) spatial analysis for quantitative assessment and predictive habitat modeling using logistic regression to combine fish survey data and environmental habitat factors to determine critical and major habitat variables for each target fish; and 3) digital mapping and changes detection of fish habitat potential for targeted endangered fish species to show habitat distribution and spatio-temporal changes of habitat potential over a 25-year period (from 1977 to 2002). We found that predicted suitable habitat and actual fish habitat showed high overlap, and that habitat conditions and distribution patterns of target freshwater fish had been affected by major habitat variables to target species respectively.     

Experimental design and taxonomic scope of fragmentation studies on European mammals: current status and future priorities

• 1 Habitat loss, habitat fragmentation and habitat degradation are the greatest threats to mammals in Europe and the rest of the world. Despite the fact that extensive literature exists, no comprehensive review or synthesis is available to date and this may slow down scientific progress and hamper conservation efforts.
• 2 The goal of this study is to understand if and in what direction progress has been made in the study of the effects of habitat loss and fragmentation on the spatial distribution of European terrestrial mammals. Firstly, we carry out a general synthesis which is structured around 11 key points. The aim of this point‐by‐point analysis is to identify trends, knowledge gaps and any significant bias in the available literature, and to highlight strengths and shortfalls of the different approaches which have to date been applied. Secondly, we follow a species‐specific systematic approach: for each species, we synthesise key results.
• 3 Our results show how substantial progress has been hampered for several reasons including: a large predominance of small‐scale field studies of short duration, and a generalised lack of control of: (i) confounding variables; (ii) spatial autocorrelation; and (iii) false absences. Also, despite the relatively high number of studies, few were theoretical studies and even fewer were meta‐analyses. The lack of meta‐analyses is likely to be due to the small amount of crucial details included in the publications, such as model parameters or information on the landscape context (such as the amount of residual forest cover).
• 4 We synthesise the main results for 14 species. The level of progress is highly variable: for some species, such as the red squirrel Sciurus vulgaris, a series of long‐term, large‐scale process‐oriented studies has allowed an in‐depth understanding of its ecology in fragmented landscapes. On the other hand, with other species such as the bank vole Myodes glareolus, despite a relatively large number of field studies, little progress has been made.

     

GBIF information is not enough: national database improves the inventory completeness of Amazonian epiphytes

Distribution data sharing in global databases (e.g. GBIF) allowed the knowledge synthesis in several biodiversity areas. However, their Wallacean shortfalls still reduce our capacity to understand distribution patterns. Including exclusive records from other databases, such as national ones (e.g. SpeciesLink), could mitigate these shortfall problems, but it remains not evaluated. Therefore, we assessed whether (i) the inventory completeness, (ii) taxonomic contribution and (iii) spatial biases could be improved when integrating both global and national biodiversity databases. Using Amazonian epiphytes as a model, we compared the available taxonomic information spatially between GBIF and SpeciesLink databases using a species contribution index. We obtained the inventory completeness from sources using species accumulation curves and assessed their spatial biases by constructing spatial autoregressive models. We found that both databases have a high amount of exclusive records (GBIF: 36.7%; SpeciesLink: 21.7%) and species (17.8%). Amazonia had a small epiphyte inventory completeness, but it was improved when we analyzed both databases together. Individually, both database records were biased to sites with higher altitude, population and herbarium density. Together, river density appeared as a new predictor, probably due to the higher species contribution of SpeciesLink along them. Our findings provide strong evidence that using both global and national databases increase the overall biodiversity knowledge and reduce inventory gaps, but spatial biases may persist. Therefore, we highlight the importance of aggregating more than one database to understand biodiversity patterns, to address conservation decisions and direct shortfalls more efficiently in future studies.

     

An assessment of animal species diversity in continental waters

There is a need for monitoring the status and trends of freshwater biodiversity in order to quantify the impacts of human actions on freshwater systems and to improve freshwater biodiversity conservation. Current projects carrying assessment of freshwater biodiversity focus mainly on leading-better-known groups such as fish, or identify keystone species and/or endemic freshwater systems for conservation purposes. Our purpose is to complete these existing projects by providing quantitative estimates of species number for all freshwater groups on each continent and/or major eco-regions. This article present the results of the first implementation phase carried out from September 2002 to June 2003 and which addressed only freshwater animal species. The project consisted of: (1) compiling existing data from literature, web sites and museum collections; (2) contacting scientific experts of each group to provide a ‘to the best of their knowledge, estimates of species numbers. In this study, we consider as true freshwater species, those that complete part or all of their life cycle in freshwater, and water-dependant species those that need freshwater for food or that permanently use freshwater habitats. The current order of magnitude for known freshwater animal species world wide is 100 000, of which half are insects. Among other groups, there are some 20 000 vertebrate species; 10 000 crustacean species and 5000 mollusc species that are either true freshwater or water-dependant species. The study highlighted gaps in the basic knowledge of species richness at continental and global scales: (1) Some groups such as Protozoa, nematodes or annelids have been less studied and data on their diversity and distribution is scarce. Because current richness estimates for these groups are greatly biased by knowledge availability, we can expect that real species numbers might be much higher. (2) Continents are not equal in the face of scientific studies: South America and Asia are especially lacking global estimates of species richness for many groups, even for some usually well-known ones such as molluscs or insects. The second phase of the project will address freshwater plants and algae. The present status should be considered as a first sketch of the global picture of freshwater biodiversity. We hope that this project will initiate interactive exchange of data to complete and update this first assessment.     

Inferring Processes from Spatial Patterns: The Role of Directional and Non–Directional Forces in Shaping Fish Larvae Distribution in a Freshwater Lake System

Larval dispersal is a crucial factor for fish recruitment. For fishes with relatively small-bodied larvae, drift has the potential to play a more important role than active habitat selection in determining larval dispersal; therefore, we expect small-bodied fish larvae to be poorly associated with habitat characteristics. To test this hypothesis, we used as model yellow perch (Perca flavescens), whose larvae are among the smallest among freshwater temperate fishes. Thus, we analysed the habitat association of yellow perch larvae at multiple spatial scales in a large shallow fluvial lake by explicitly modelling directional (e.g. due to water currents) and non-directional (e.g. due to aggregation) spatial patterns. This allowed us to indirectly assess the relative roles of drift (directional process) and potential habitat choice on larval dispersal. Our results give weak support to the drift hypothesis, whereas yellow perch show a strong habitat association at unexpectedly small sizes, when compared to other systems. We found consistent non-directional patterns in larvae distributions at both broad and medium spatial scales but only few significant directional components. The environmental variables alone (e.g. vegetation) generally explained a significant and biologically relevant fraction of the variation in fish larvae distribution data. These results suggest that (i) drift plays a minor role in this shallow system, (ii) larvae display spatial patterns that only partially covary with environmental variables, and (iii) larvae are associated to specific habitats. By suggesting that habitat association potentially includes an active choice component for yellow perch larvae, our results shed new light on the ecology of freshwater fish larvae and should help in building more realistic recruitment models.     

Life histories of closely related amphidromous and non‐migratory fish species: a trade‐off between egg size and fecundity

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Drivers and stressors of freshwater biodiversity patterns across different ecosystems and scales: a review

The present review with focus on the last decade (2000–2010) aims to (i) collecting the major hypotheses explaining freshwater biodiversity patterns, (ii) identifying the main stressors affecting freshwater biodiversity, and (iii) revealing information gaps regarding ecosystem types, organism groups, spatial and temporal scales to highlight research needs to better propose sound conservation measures. The comparative analysis addresses six organism groups ranging from microorganisms to fish in basins, rivers, lakes, wetlands, ponds and groundwater. Short-term studies at ecoregion and catchment scale focusing on invertebrates, macrophytes and fish in Palaearctic and Nearctic regions dominated. The most frequent hypotheses tested were the landscape filter concept, the species–area relationship, the metacommunity concept. Dominating natural drivers were area, heterogeneity and disturbance. Land use, eutrophication and habitat destruction were identified as most important stressors. Generally, freshwater biodiversity declined in response to these stressors in contrast to increasing biodiversity determined by natural drivers across all ecosystems. Preferred organism groups were fish and invertebrates, most frequently studied in rivers, in contrast to smaller organisms (e.g. bacteria) and, e.g. groundwater being underrepresented. Hypotheses originating from the last century are still tested in freshwater research, while novel concepts are either missing or untested. Protection of freshwater biodiversity is the ultimate challenge since it supports valuable ecosystems services ensuring perpetuation of mankind. For that, comprehensive large-scale studies with holistic approaches are urgently needed.     

Biogeography,ecoregions, and geomorphology affect fish species composition in streams of eastern Oklahoma,USA

Stream fish assemblages are structured by biogeographical, physical and biological factors acting on different spatial scales. We determined how physical factors, geomorphology and stream habitat, influenced fish species composition (presence–absence) in eastern Oklahoma, USA relative to the ecoregion and biogeographic effects previously reported. We sampled fish assemblages and surveyed geomorphology and habitat at 107 stream sites in the Boston Mountains, Ouachita Mountains, and Ozark Highlands ecoregions in eastern Oklahoma. Partial canonical correspondence analyses (pCCAs) and variance partitioning showed that patterns of endemism related to drainage basins and ecoregions explained important variation in fish species composition in all streams, but stream size and local channel morphology explained more variation overall. Stream size effects were most important in explaining variability in fish species composition in both northeastern and southeastern Oklahoma streams. Local channel morphology and substrate characteristics were secondarily important. Variables typically considered important as fish habitat (aquatic vegetation, etc.) had little effect on fish species composition.     

DNA barcoding and morphological identification of neotropical ichthyoplankton from the Upper Paraná and São Francisco

The identification of fish larvae from two neotropical hydrographic basins using traditional morphological taxonomy and DNA barcoding revealed no conflicting results between the morphological and barcode identification of larvae. A lower rate (25%) of correct morphological identification of eggs as belonging to migratory or non‐migratory species was achieved. Accurate identification of ichthyoplankton by DNA barcoding is an important tool for fish reproductive behaviour studies, correct estimation of biodiversity by detecting eggs from rare species, as well as defining environmental and management strategies for fish conservation in the neotropics.     

Does within-population variation in fish egg size reflect maternal influences on optimal values?

Various models that assume correlations between maternal phenotype and offspring environment predict adaptive variation in egg size within populations. Here we conduct a comparative test of these models using published data on fish egg size. Intrapopulation variation in egg size was most pronounced in fish with demersal eggs and larvae (median coefficient of variation [CV] at family level = 6.5%), where offspring environment is likely influenced by maternal phenotype, and least so in fish with pelagic eggs (CV = 3.6%), which experience a relatively stochastic spatial distribution during incubation. This difference was significant at various taxonomic levels, was robust to variation in mean egg size and habitat (i.e., freshwater or marine), and was mirrored in independent paired contrasts. Fish with demersal eggs and pelagic larvae were not significantly different from those with pelagic eggs (CV = 3.8%), indicating that selection favoring within-population variation in egg size occurs mainly posthatching and that any such selection occurring prehatching may be less intense. These results suggest that patterns of within-population variation in egg size among fish taxa reflect adaptive processes and that maternal effects on the egg size-fitness function may explain apparent discrepancies from the single-optima Smith-Fretwell model.     

Climate‐induced changes in the distribution of freshwater fish: observed and predicted trends

1. Climate change could be one of the main threats faced by aquatic ecosystems and freshwater biodiversity. Improved understanding, monitoring and forecasting of its effects are thus crucial for researchers, policy makers and biodiversity managers. 2. Here, we provide a review and some meta‐analyses of the literature reporting both observed and predicted climate‐induced effects on the distribution of freshwater fish. After reviewing three decades of research, we summarise how methods in assessing the effects of climate change have evolved, and whether current knowledge is geographically or taxonomically biased. We conducted multispecies qualitative and quantitative analyses to find out whether the observed responses of freshwater fish to recent changes in climate are consistent with those predicted under future climate scenarios. 3. We highlight the fact that, in recent years, freshwater fish distributions have already been affected by contemporary climate change in ways consistent with anticipated responses under future climate change scenarios: the range of most cold‐water species could be reduced or shift to higher altitude or latitude, whereas that of cool‐ and warm‐water species could expand or contract. 4. Most evidence about the effects of climate change is underpinned by the large number of studies devoted to cold‐water fish species (mainly salmonids). Our knowledge is still incomplete, however, particularly due to taxonomic and geographic biases. 5. Observed and expected responses are well correlated among families, suggesting that model predictions are supported by empirical evidence. The observed effects are of greater magnitude and show higher variability than the predicted effects, however, indicating that other drivers of changes may be interacting with climate and seriously affecting freshwater fish. 6. Finally, we suggest avenues of research required to address current gaps in what we know about the climate‐induced effects on freshwater fish distribution, including (i) the need for more long‐term data analyses, (ii) the assessment of climate‐induced effects at higher levels of organisation (e.g. assemblages), (iii) methodological improvements (e.g. accounting for uncertainty among projections and species’ dispersal abilities, combining both distributional and empirical approaches and including multiple non‐climatic stressors) and (iv) systematic confrontation of observed versus predicted effects across multi‐species assemblages and at several levels of biological organisation (i.e. populations and assemblages).     

Relative need for conservation assessments of vascular plant species among ecoregions

Aim (1) To determine the relative need for conservation assessments of vascular plant species among the world’s ecoregions given under‐assessed species distributions; (2) to evaluate the challenge posed by the lack of financial resources on species assessment efforts; and (3) to demonstrate the utility of nonlinear mixed‐effects models with both homoscedastic and heteroscedastic error structures in the identification of species‐rich ecoregions. Location Global. Methods We identified the world’s ecoregions that contain the highest vascular plant species richness after controlling for area using species–area relationship (SAR) models built within a mixed‐effects multi‐model framework. Using quantitative thresholds, ecoregions with the highest plant species richness, historical habitat loss and projected increase in human population density were deemed to be most in need of conservation assessments of plant species. We used generalized linear models to test if countries that overlap with highly important ecoregions are poorer compared with others. Results We classed ecoregions into nine categories based on the relative need for conservation assessments of vascular plant species. Ecoregions of highest relative need are found mostly in the tropics, particularly Southeast Asia, Central America, Tropical Andes and the Cerrado of South America, and the East African montane region and its surrounding areas. Countries overlapping with ecoregions deemed important for conservation assessments are poorer as measured by their capita gross national income than the other countries. The nonlinear mixed modelling framework was effective in reducing residual spatial autocorrelation compared with nonlinear models comprised of only fixed effects. In contrasting multiple SAR models to identify species‐rich ecoregions, there was not one SAR model that fitted best across all biomes. Not all SAR models displayed homoscedastic errors; therefore it is important to consider models with both homoscedastic and heteroscedastic error structures. Main conclusions We propose that conservation assessments should be conducted first in ecoregions with the greatest predicted species richness, historical habitat loss and future human population increase. As ecoregions deemed to be important for conservation assessments are located in the poorest countries, we urge international aid agencies and botanic gardens to cooperate with both local and international scientists to fund and implement conservation assessment programmes there.     

Hung out to dry: choice of priority ecoregions for conserving threatened neotropical anurans depends on life-history traits

Background

In the Neotropics, nearly 35% of amphibian species are threatened by habitat loss, habitat fragmentation, and habitat split; anuran species with different developmental modes respond to habitat disturbance in different ways. This entails broad-scale strategies for conserving biodiversity and advocates for the identification of high conservation-value regions that are significant in a global or continental context and that could underpin more detailed conservation assessments towards such areas.

Methodology/Principal Findings

We identified key ecoregion sets for anuran conservation using an algorithm that favors complementarity (beta-diversity) among ecoregions. Using the WWF''s Wildfinder database, which encompasses 700 threatened anuran species in 119 Neotropical ecoregions, we separated species into those with aquatic larvae (AL) or terrestrial development (TD), as this life-history trait affects their response to habitat disturbance. The conservation target of 100% of species representation was attained with a set of 66 ecoregions. Among these, 30 were classified as priority both for species with AL and TD, 26 were priority exclusively for species with AL, and 10 for species with TD only. Priority ecoregions for both developmental modes are concentrated in the Andes and in Mesoamerica. Ecoregions important for conserving species with AL are widely distributed across the Neotropics. When anuran life histories were ignored, species with AL were always underrepresented in priority sets.

Conclusions/Significance

The inclusion of anuran developmental modes in prioritization analyses resulted in more comprehensive coverage of priority ecoregions–especially those essential for species that require an aquatic habitat for their reproduction–when compared to usual analyses that do not consider this life-history trait. This is the first appraisal of the most important regions for conservation of threatened Neotropical anurans. It is also a first endeavor including anuran life-history traits in priority area-selection for conservation, with a clear gain in comprehensiveness of the selection process.     

Distribution and abundance of fish eggs and larvae in three tributaries of the Upper Uruguay River (Brazil)

The present study aimed to investigate the distribution and abundance of fish eggs and larvae in three important tributaries (Chapecó, Peixe, and Ligeiro rivers) of the Upper Uruguay River. The spatial and temporal distribution of fish eggs and larvae were studied as well as the correlation between environmental parameters and the abundance of ichthyoplankton species. The study was conducted between October 2005 and September 2006. Ichthyoplankton samples were collected at night with cylindroconical 0.5-mm mesh plankton nets every 5 days. Of the 591 samples collected, 170 contained ichthyoplankton organisms, resulting in the capture of 12,847 fish eggs and 962 fish larvae. Twenty-seven fish species were observed, of which 69% were Characiforms and 27% were Siluriforms. Among the fish species captured, the representatives were predominantly young forms of small and medium size fishes, with rheophilic species occurring infrequently. Eggs occurred exclusively between October and January, while the highest larvae occurrence was observed between November and December. Fish larvae assemblage structure was shown to be related to some environmental variables. There was a tendency of higher values of water temperature and velocity at the lower sampling sites than at the upper ones, as well an increase number of eggs and larvae. The study tributaries serve as reproduction sites and nursery areas for several fish species of the Upper Uruguay River; thus, the maintenance of their integrity is important for the preservation of diversity and enhancement of fisheries in the region.     

Communication gaps in knowledge of freshwater fish biodiversity: implications for the management and conservation of Mexican biosphere reserves

To detect differences in the information available on freshwater fish species found in Mexican biosphere reserves, the number of species considered in three sources of information: management programmes, Global Biodiversity Information Facility (GBIF) and the scientific literature were compared. Additionally, management actions for the reserves were evaluated. More than 55% of freshwater fish species registered for the reserves were found only in one of the three sources of information, while just 12% was shared among all the three. Fifteen threatened species were registered in GBIF and the scientific literature that were not found in management programmes. Although all the management programmes described conservation actions, none of them gave details about how they would be implemented. Lack of communication among the sources studied, unawareness of the existence of threatened species and the absence of detailed management actions hinder the development of adequate conservation strategies.     

DNA barcoding reveals the temporal community composition of drifting fish eggs in the lower Hongshui River,China

Determining the temporal community composition of fish eggs in particular regions and understanding the reproductive times of regional fish taxa are key aspects of the management and regulation of regional fish stocks. However, it is extremely difficult to accurately identify fish eggs due to the absence of diagnostic morphological characters. We sampled fish eggs in the lower Hongshuihe River (an upper mainstem of the Pearl River) between May and September 2020. We then used DNA barcoding to determine the species composition of the egg pool and to predict the spawning periods of the identified species. A total of 641 eggs and 17 larvae were chosen for molecular identification; 397 eggs and 17 larvae yielded high‐quality barcoding sequences. The high failure rate (~38%) was most likely due to long‐term storage in low concentrations of ethanol prior to molecular analysis. We successfully classified 392 eggs into 10 species and 13 larvae into four species using public databases. Most of the species identified in the egg pool were small and/or benthic, and migratory species were rare. This may partially reflect the adverse effects of hydropower cascade development in this river section. We also found that spawning periods tended to be species‐specific. Our study provides a reference for the conservation and management of regional fishery stocks.     

Do hotspots fall within protected areas? A Geographic Approach to Planning analysis of regional freshwater biodiversity

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Nation-wide indicators of ecological integrity in Mexico: The status of mammalian apex-predators and their habitat

Ecological indicators that evaluate the status and trends of mammalian apex predators are necessary for monitoring the ecological integrity of landscapes. Several nation-wide spatial indicators that describe the status of apex predators after habitat transformation have been developed for México. These spatial indicators show the condition of the remnant natural landscape for maintaining the complexity of predator-prey interactions and habitat selection and use. The indicators were obtained using the concept of ecological integrity, that characterize the landscape based upon manifest and latent variables of naturalness, stability and self-organization, according with the measures of spatial distribution of species and natural habitat. When the current status is evaluated for individual species of apex predators, all species showed less than 50% of their distribution areas with a high degree of ecological integrity. Neotropical predators (such as jaguars and ocelots) are more threatened by the transformation of natural habitat, than their counterparts in Nearctic regions (e.g., bears, cougars, bobcats, and coyotes), which showed nonetheless, a high amount of their distribution areas with a high proportion of degraded habitat. The indicators allowed evaluating the status of still extant top predators in the landscape and their habitat condition within major ecoregions in the country.