Threats and biodiversity in the mediterranean biome

Aim Global conservation assessments recognize the mediterranean biome as a priority for the conservation of the world's biodiversity. To better direct future conservation efforts in the biome, an improved understanding of the location, magnitude and trend of key threats and their relationship with species of conservation importance is needed. Location Mediterranean‐climate regions in California‐Baja California, Chile, South Africa, Australia and the Mediterranean Basin. Methods We undertook a systematic, pan‐regional assessment of threats in the mediterranean biome including human population density, urban area and agriculture. To realize the full implications of these threats on mediterranean biodiversity, we examined their relationship with species of conservation concern: threatened mammals at the global scale and threatened plants at the subecoregional scale in California, USA. Results Across the biome, population density and urban area increased by 13% and agriculture by 1% between 1990 and 2000. Both population density and urban area were greatest in California‐Baja California and least in Australia while, in contrast, agriculture was greatest in Australia and least in California‐Baja California. In all regions lowlands were most affected by the threats analysed, with the exception of population density in the Chilean matorral. Threatened species richness had a significant positive correlation with population density at global and subecoregional scales, while threatened species were found to increase with the amount of urban area and decrease as the amount of natural area and unfragmented core area increased. Main conclusions Threats to mediterranean biodiversity have increased from 1990 to 2000, although patterns vary both across and within the five regions. The need for future conservation efforts is further underlined by the positive correlation between species of conservation concern and the increase in population density over the last decade. Challenges to reducing threats extend beyond those analysed to include human–environmental interactions and their synergistic effects, such as urbanization and invasive species and wildfires.     

Global species richness of hydrobiid snails determined by climate and evolutionary history

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Determinants of fine‐scale homogenization and differentiation of native freshwater fish faunas in a Mediterranean Basin: implications for conservation

Aim Increasing threats to freshwater biodiversity are rapidly changing the distinctiveness of regional species pools and local assemblages. Biotic homogenization/differentiation processes are threatening the integrity and persistence of native biodiversity patterns at a range of spatial scales and pose a challenge for effective conservation planning. Here, we evaluate the extent and determinants of fine‐scale alteration in native freshwater fish assemblages among stream reaches throughout a large river basin and consider the implications of these changes for the long‐term conservation of native fishes. Location Guadiana River basin (South‐Western Iberian Peninsula). Methods We quantified the magnitude of change in compositional similarity between observed and reference assemblages and its potential effect on natural patterns of compositional distinctiveness. Reference assemblages were defined as the native species expected to occur naturally (in absence of anthropogenic alterations) and were reconstructed using a multivariate adaptive regression splines predictive model. We also evaluated the role of habitat degradation and introduced species as determinants of biotic homogenization/differentiation. Results We found a significant trend towards homogenization for native fish assemblages. Changes in native fish distributions led to the loss of distinctiveness patterns along natural environmental gradients. Introduced species were the most important factor explaining the homogenization process. Homogenization of native assemblages was stronger in areas close to reservoirs and in lowland reaches where introduced species were more abundant. Main conclusions The implementation of efficient conservation for the maintenance of native fish diversity is seriously threatened by the homogenization processes. The identification of priority areas for conservation is hindered by the fact that the most diverse communities are vanishing, which would require the selection of broader areas to adequately protect all the species. Given the principal role that introduced species play in the homogenization process and their relation with reservoirs, special attention must be paid to mitigating or preventing these threats.     

Multiple drivers of decline in the global status of freshwater crayfish (Decapoda: Astacidea)

Rates of biodiversity loss are higher in freshwater ecosystems than in most terrestrial or marine ecosystems, making freshwater conservation a priority. However, prioritization methods are impeded by insufficient knowledge on the distribution and conservation status of freshwater taxa, particularly invertebrates. We evaluated the extinction risk of the world''s 590 freshwater crayfish species using the IUCN Categories and Criteria and found 32% of all species are threatened with extinction. The level of extinction risk differed between families, with proportionally more threatened species in the Parastacidae and Astacidae than in the Cambaridae. Four described species were Extinct and 21% were assessed as Data Deficient. There was geographical variation in the dominant threats affecting the main centres of crayfish diversity. The majority of threatened US and Mexican species face threats associated with urban development, pollution, damming and water management. Conversely, the majority of Australian threatened species are affected by climate change, harvesting, agriculture and invasive species. Only a small proportion of crayfish are found within the boundaries of protected areas, suggesting that alternative means of long-term protection will be required. Our study highlights many of the significant challenges yet to come for freshwater biodiversity unless conservation planning shifts from a reactive to proactive approach.     

Freshwater fish introductions in mediterranean‐climate regions: are there commonalities in the conservation problem?

Aim To compare patterns and drivers of freshwater fish introductions across five climatically similar regions and evaluate similarities and differences in the non‐native species introduced. Location Five mediterranean‐climate regions: California (USA), central Chile, south‐western Australia, the Iberian peninsula (Spain and Portugal) and the south‐western Cape (South Africa). Methods Species presence–absence for native and non‐native fishes were collated across the regions, and patterns of faunal change were examined using univariate and multivariate statistical approaches. Taxonomic patterns in freshwater fish introductions were evaluated by comparing the number of species introduced by order to the numbers expected from binomial probabilities. Factors influencing multiple introductions of freshwater fish species in mediterranean regions were determined using generalized linear modelling. Results High levels of endemism (70–90%) were revealed for south‐western Cape, south‐western Australia and Chile. Despite their high rates of endemism, all regions currently have more non‐native species than endemic species. Taxonomic selection was found for five orders, although this was only significant for Salmoniformes across regions. The average increase in regional compositional similarity of fish faunas resulting from non‐native fish introductions was 8.0%. Important factors predicting multiple introductions of a species include previous introduction success and mean latitude of its distribution Main conclusions The mediterranean‐climate regions of the world, separated by vast distances, originally had a few fish species in common but are now more similar, owing to species introductions, illustrating the extent and importance of taxonomic homogenization. Introductions are largely driven by taxonomically biased human interests in recreational fisheries, aquaculture and ornamental pet species.     

Response to De Silva et al. (2007): Endemic freshwater finfish of Asia: distribution and conservation status

De Silva et al . (2007) present an overview of the distribution and conservation status of the endemic freshwater fish of Asia. Within that review they use data from the IUCN Red List of Threatened Species™ (2006) to conduct an analysis of the conservation status of those endemic fish species. Their analysis is incorrect and provides a very misleading impression of the level of threat to Asian freshwater fish and to freshwater fish at the global scale. The errors stem from a misinterpretation of the data presented on the IUCN Red List. The sources of errors are discussed below and the opportunity is taken to clarify what the information on the IUCN Red List represents.     

A macroecological perspective of diversity patterns in the freshwater realm

1. The aim of this paper is to review literature on species diversity patterns of freshwater organisms and underlying mechanisms at large spatial scales. 2. Some freshwater taxa (e.g. dragonflies, fish and frogs) follow the classical latitudinal decline in regional species richness (RSR), supporting the patterns found for major terrestrial and marine organism groups. However, the mechanisms causing this cline in most freshwater taxa are inadequately understood, although research on fish suggests that energy and history are major factors underlying the patterns in total species and endemic species richness. Recent research also suggests that not all freshwater taxa comply with the decline of species richness with latitude (e.g. stoneflies, caddisflies and salamanders), but many taxa show more complex geographical patterns in across‐regions analyses. These complexities are even more profound when studies of global, continental and regional extents are compared. For example, clear latitudinal gradients may be present in regional studies but absent in global studies (e.g. macrophytes). 3. Latitudinal gradients are often especially weak in the across‐ecosystems analyses, which may be attributed to local factors overriding the effects of large‐scale factors on local communities. Nevertheless, local species richness (LSR) is typically linearly related to RSR (suggesting regional effects on local diversity), although saturating relationships have also been found in some occasions (suggesting strong local effects on diversity). Nestedness has often been found to be significant in freshwater studies, yet this pattern is highly variable and generally weak, suggesting also a strong beta diversity component in freshwater systems. 4. Both geographical location and local environmental factors contribute to variation in alpha diversity, nestedness and beta diversity in the freshwater realm, although the relative importance of these two groups of explanatory variables may be contingent on the spatial extent of the study. The mechanisms associated with spatial and environmental control of community structure have also been inferred in a number of studies, and most support has been found for species sorting (possibly because many freshwater studies have species sorting as their starting point), although also dispersal limitation and mass effects may be contributing to the patterns found. 5. The lack of latitudinal gradients in some freshwater taxa begs for further explanations. Such explanations may not be gained for most freshwater taxa in the near future, however, because we lack species‐level information, floristic and faunistic knowledge, and standardised surveys along extensive latitudinal gradients. A challenge for macroecology is thus to use the best possible species‐level information on well‐understood groups (e.g. fish) or use surrogates for species‐level patterns (e.g. families) and then develop hypotheses for further testing in the freshwater realm. An additional research challenge concerns understanding patterns and mechanisms associated with the relationships between alpha, beta and gamma components of species diversity. 6. Understanding the mechanistic basis of species diversity patterns should preferably be based on a combination of large‐scale macroecological and landscape‐scale metacommunity research. Such a research approach will help in elucidating patterns of species diversity across regional and local scales in the freshwater realm.     

The Mediterranean Sea as a ‘cul‐de‐sac’ for endemic fishes facing climate change

The Mediterranean Sea is a hotspot of biodiversity, and climate warming is expected to have a significant influence on its endemic fish species. However, no previous studies have predicted whether fish species will experience geographic range extensions or contractions as a consequence of warming. Here, we projected the potential future climatic niches of 75 Mediterranean Sea endemic fish species based on a global warming scenario implemented with the Mediterranean model OPAMED8 and a multimodel inference, which included uncertainty. By 2070–2099, the average surface temperature of the Mediterranean Sea was projected to warm by 3.1 °C. Projections for 2041–2060 are that 25 species would qualify for the International Union for the Conservation of Nature and Natural Resources (IUCN) Red List, and six species would become extinct. By 2070–2099, 45 species were expected to qualify for the IUCN Red List whereas 14 were expected to become extinct. By the middle of the 21st century, the coldest areas of the Mediterranean Sea (Adriatic Sea and Gulf of Lion) would act as a refuge for cold‐water species, but by the end of the century, those areas were projected to become a ‘cul‐de‐sac’ that would drive those species towards extinction. In addition, the range size of endemic species was projected to undergo extensive fragmentation, which is a potentially aggravating factor. Since a majority of endemic fishes are specialists, regarding substratum and diet, we may expect a reduced ability to track projected climatic niches. As a whole, 25% of the Mediterranean Sea continental shelf was predicted to experience a total modification of endemic species assemblages by the end of the 21st century. This expected turnover rate could be mitigated by marine protected areas or accelerated by fishing pressure or competition from exotic fishes. It remains a challenge to predict how these assemblage modifications might affect ecosystem function.     

Protected and threatened components of fish biodiversity in the Mediterranean sea

The Mediterranean Sea (0.82% of the global oceanic surface) holds 4%-18% of all known marine species (~17,000), with a high proportion of endemism [1, 2]. This exceptional biodiversity is under severe threats [1] but benefits from a system of 100 marine protected areas (MPAs). Surprisingly, the spatial congruence of fish biodiversity hot spots with this MPA system and the areas of high fishing pressure has not been assessed. Moreover, evolutionary and functional breadth of species assemblages [3] has been largely overlooked in marine systems. Here we adopted a multifaceted approach to biodiversity by considering the species richness of total, endemic, and threatened coastal fish assemblages as well as their functional and phylogenetic diversity. We show that these fish biodiversity components are spatially mismatched. The MPA system covers a small surface of the Mediterranean (0.4%) and is spatially congruent with the hot spots of all taxonomic components of fish diversity. However, it misses hot spots of functional and phylogenetic diversity. In addition, hot spots of endemic species richness and phylogenetic diversity are spatially congruent with hot spots of fishery impact. Our results highlight that future conservation strategies and assessment efficiency of current reserve systems will need to be revisited after deconstructing the different components of biodiversity.     

黄河流域淡水鱼类多样性和保护

本文介绍了黄河流域鱼类研究的历史、淡水鱼类的物种组成、整体分布格局、特有性、濒危性, 以及鱼类多样性在黄河上、中、下游等的特点。历史上对于黄河鱼类多样性的研究, 历经了四个阶段, 从最初的零星记录一直到现阶段的深入研究。综合历史记录和野外调查, 已知黄河流域分布的淡水鱼类共计147种, 隶属于12目21科78属, 其中鲤形目种类占据绝对优势。另外, 全流域黄河特有种计有27种, 受危物种24种, 分别占总数的18.37%和16.32%。同中国主要江河相比, 黄河鱼类在高级分类阶元上的多样性较高, 但物种多样性则处在较低水平; 尽管黄河特有鱼类和受危物种比例低于全国平均水平, 但上游特有鱼类和珍稀濒危鱼类的占比很高。目前黄河鱼类多样性大幅降低, 现状调查仅能采获历史记录种类的53.06%。梯级水电开发、水资源过度利用、外来物种、水域污染和过度捕捞都是威胁鱼类多样性的重要因素, 但对各河段和支流的影响不一, 应做出有针对性的保护部署。     

Freshwater biodiversity in the rivers of the Mediterranean Basin

We review the diversity of freshwater organisms in the Mediterranean Basin (hereafter Med), particularly from streams and rivers. We present available information on the richness, endemicity, and distribution of each freshwater organism group within the Med, and make a comparison with Palearctic diversity. Approximately 35% of known Palearctic freshwater species and more than 6% of the World’s freshwater species are present in the Med. A high degree of endemicity is found in the Med freshwater biota. These data, together with the degree to which many freshwater species are threatened, support the inclusion of the Med among World biodiversity hotspots. Nevertheless, knowledge of Med biodiversity is still incomplete, particularly for some taxa. Regarding to the spatial distribution of species within the Med, the richest area is the North, although patterns differ among groups. A comparison of the ecological and biological traits of endemic and non-endemic species of three riverine groups (Ephemeroptera, Plecoptera, and Trichoptera) revealed that endemic species have several strategies and mechanisms to face typical mediterranean-climate conditions, such as drought, when compared to non-endemic species. We briefly analyse the conservation status of the region’s biodiversity. Finally, we present some future challenges regarding the knowledge and protection of Med freshwater biodiversity.     

Analysing freshwater fish biodiversity records and respective conservation areas in Spain

The number of threatened freshwater fish species in Spain is among the highest recorded in Europe and includes a high percentage of endemic taxa. Investigated were the distribution of Spanish freshwater fish to identify priority areas for conservation and assess the extent to which freshwater fish are included in the existing network of protected areas. Considered were those threatened species recorded in the Spanish National inventories. From these data, several biodiversity indices were calculated and analysed. The results reveal important discrepancies between the national and international assessments of conservation status, whereby the current Spanish national catalogue needs updating to reconcile these inconsistencies. Several important areas for the conservation of freshwater fish lie outside protected areas. The results encourage the establishment of protected areas specifically for freshwater environments. An extensive database of Spanish freshwater fish species is needed to redefine priority areas and to maintain freshwater biodiversity.     

马铁菊头蝠捕食活动与猎物资源的关系

捕食者与猎物的关系研究对了解物种捕食行为及种群空间格局具有重要意义。采用Avisoft Bioacoustics超声波仪录制马铁菊头蝠自然状态下的声波以确定其捕食活动强度,用灯诱法、扫网法和飞行阻隔法相结合采集昆虫,搜集蝙蝠粪便并分析其食物组成。结果表明,马铁菊头蝠在8月份活动最频繁,昆虫丰富度在8月份最丰富,马铁菊头蝠捕食活动与鳞翅目丰富度呈显著正相关。马铁菊头蝠主要以鳞翅目和鞘翅目为食,但食性存在明显的月份变化。卡方检验结果表明,马铁菊头蝠捕食的猎物与环境中可利用的昆虫猎物存在显著差异。在食物资源丰富时,马铁菊头蝠选择性地捕食营养丰富的鞘翅目昆虫。     

Phylogeography,historical demography and habitat suitability modelling of freshwater fishes inhabiting seasonally fluctuating Mediterranean river systems: a case study using the Iberian cyprinid Squalius valentinus

The Mediterranean freshwater fish fauna has evolved under constraints imposed by the seasonal weather/hydrological patterns that define the Mediterranean climate. These conditions have influenced the genetic and demographic structure of aquatic communities since their origins in the Mid‐Pliocene. Freshwater species in Mediterranean‐type climates will likely constitute genetically well‐differentiated populations, to varying extents depending on basin size, as a consequence of fragmentation resulting from drought/flood cycles. We developed an integrative framework to study the spatial patterns in genetic diversity, demographic trends, habitat suitability modelling and landscape genetics, to evaluate the evolutionary response of Mediterranean‐type freshwater fish to seasonal fluctuations in weather. To test this evolutionary response, the model species used was Squalius valentinus, an endemic cyprinid of the Spanish Levantine area, where seasonal weather fluctuations are extreme, although our findings may be extrapolated to other Mediterranean‐type species. Our results underscore the significant role of the Mediterranean climate, along with Pleistocene glaciations, in diversification of S. valentinus. We found higher nuclear diversity in larger drainage basins, but higher mitochondrial diversity correlated to habitat suitability rather than basin size. We also found strong correlation between genetic structure and climatic factors associated with Mediterranean seasonality. Demographic and migration analyses suggested population expansion during glacial periods that also contributed to the current genetic structure of S. valentinus populations. The inferred models support the significant contribution of precipitation and temperature to S. valentinus habitat suitability and allow recognizing areas of habitat stability. We highlight the importance of stable habitat conditions, fostered by typical karstic springs found on the Mediterranean littoral coasts, for the preservation of freshwater species inhabiting seasonally fluctuating river systems.     

Data uncertainty and the selectivity of extinction risk in freshwater invertebrates

Aim

To investigate the impact of different treatments of the IUCN Data Deficient (DD) category on taxonomic and geographical patterns of extinction risk in crayfish, freshwater crabs and dragonflies.

Location

Global.

Methods

We used contingency tables to evaluate taxonomic and geographical selectivity of data deficiency and extinction risk for three invertebrate taxonomic groups (crayfish, dragonflies and damselflies, and freshwater crabs) based on their IUCN Red List status. We investigated differences in patterns of data deficiency and extinction risk among taxonomic families, geographical realms and taxonomic families within geographical realms for each of the three groups. At each level, we evaluated the impact of uncertainty conferred by the conservation status of DD species on extinction risk patterns exhibited by that group. We evaluated three scenarios: excluding DD species, treating all DD species as non‐threatened and treating all DD species as threatened.

Results

At the global scale, DD species were taxonomically non‐randomly distributed in freshwater crabs and dragonflies, and geographically non‐randomly distributed in all three taxonomic groups. Although the presence of under‐ or over‐threatened families and biogeographical realms was generally unchanging across scenarios, the strength of taxonomic and geographical selectivity of extinction risk varied. There was little consistent evidence for taxonomic selectivity of extinction risk at sub‐global scales in freshwater crabs and dragonflies, either among biogeographical realms or among scenarios.

Main conclusions

Global patterns of taxonomic selectivity and geographical selectivity were generally consistent with one another and robust to different treatments of DD species. However, sub‐global scale conservation prioritization from these types of data sets will require increased investment to make accurate decisions. Given the current levels of data uncertainty, the relative importance of biological characteristics and threatening processes in driving extinctions in freshwater invertebrates cannot be easily determined. We recommend that DD species should be given high research priority to determine their true status.     

Potential impacts of future land use and climate change on the Red List status of the Proteaceae in the Cape Floristic Region, South Africa

Using spatial predictions of future threats to biodiversity, we assessed for the first time the relative potential impacts of future land use and climate change on the threat status of plant species. We thus estimated how many taxa could be affected by future threats that are usually not included in current IUCN Red List assessments. Here, we computed the Red List status including future threats of 227 Proteaceae taxa endemic to the Cape Floristic Region, South Africa, and compared this with their Red List status excluding future threats. We developed eight different land use and climate change scenarios for the year 2020, providing a range of best‐ to worst‐case scenarios. Four scenarios include only the effects of future land use change, while the other four also include the impacts of projected anthropogenic climate change (HadCM2 IS92a GGa), using niche‐based models. Up to a third of the 227 Proteaceae taxa are uplisted (become more threatened) by up to three threat categories if future threats as predicted for 2020 are included, and the proportion of threatened Proteaceae taxa rises on average by 9% (range 2–16%), depending on the scenario. With increasing severity of the scenarios, the proportion of Critically Endangered taxa increases from about 1% to 7% and almost 2% of the 227 Proteaceae taxa become Extinct because of climate change. Overall, climate change has the most severe effects on the Proteaceae, but land use change also severely affects some taxa. Most of the threatened taxa occur in low‐lying coastal areas, but the proportion of threatened taxa changes considerably in inland mountain areas if future threats are included. Our approach gives important insights into how, where and when future threats could affect species persistence and can in a sense be seen as a test of the value of planned interventions for conservation.     

Impact of terrestrial protected areas on the fish diversity and habitat quality: Evidence from tropical river Pranhita,India

The conservation and management of inland fish and freshwater ecosystems immensely contribute to global sustainable development. The existing ‘Protected Area’ (PA) network does not represent freshwater resources well and seldom considers its fish communities, while designating PAs. A study was undertaken to quantitatively assess the role played by the three terrestrial PAs (IUCN category IV) in conserving fish diversity and preserving habitat quality in the river reaches bordering the three PAs of the river Pranhita. It is a unique river system in the Indian Deccan Plateau in terms of fish diversity and community structure. Field surveys were conducted during the non-monsoon and monsoon seasons in 2020–21, that recorded 53 species including endemic and threatened fishes from river Pranhita, which represent more than one-third the number of fish species of Telangana state. The higher diversity and lower dominance index value (p < 0.01) reported in PAs compared to Eco Sensitive Zones and unprotected areas during the non-monsoon season indicate the role of intact physical habitat in providing refuges to the fish species in monsoon dependent tropical rivers. The optimal water quality revealed no significant difference (p > 0.0001) between protected and unprotected river reaches, and healthy biotic integrity assessed on the basis of fish community structure was attributed to the contiguous flow and less anthropogenic disturbance. This study supports that it can be considered as a representative zone for the conservation and protection of indigenous and endemic fish species of the Godavari Basin. The results concluded that the scope of the terrestrial PA network in India could be potentially extended to their bordering aquatic ecosystems, especially rivers to maintain pristine habitat conditions and conserve the fish genetic resources to ensure the flow of ecosystem services.     

Dead Shrimp Blues: A Global Assessment of Extinction Risk in Freshwater Shrimps (Crustacea: Decapoda: Caridea)

We present the first global assessment of extinction risk for a major group of freshwater invertebrates, caridean shrimps. The risk of extinction for all 763 species was assessed using the IUCN Red List criteria that include geographic ranges, habitats, ecology and past and present threats. The Indo-Malayan region holds over half of global species diversity, with a peak in Indo-China and southern China. Shrimps primarily inhabit flowing water; however, a significant subterranean component is present, which is more threatened than the surface fauna. Two species are extinct with a further 10 possibly extinct, and almost one third of species are either threatened or Near Threatened (NT). Threats to freshwater shrimps include agricultural and urban pollution impact over two-thirds of threatened and NT species. Invasive species and climate change have the greatest overall impact of all threats (based on combined timing, scope and severity of threats).     

A conservation appraisal of the rare and endemic vascular plants of Pitcairn Island

The flora of the Pitcairn Islands consists of 81 species, of which 10 are endemic. IUCN Red List threat categories show that over 60% of the indigenous flora is threatened within the island, and over 20% is threatened globally. To provide a more objective regional assessment that could prioritise conservation management, a system of threat scores was applied to each taxon based on potential threat due to habitat damage or exploitation. The main threats affecting the flora and vegetation are posed by habitat clearance, spread of invasive species, small population sizes or restricted distributions, erosion, lack of a frugivorous bird and exploitation. Addressing these threats by means of a system of nature reserves, species-specific recovery plans and control of invasive species, erosion and exploitation, will start to combat these problems. However, any conservation activities must be implemented in conjunction with the interests of the local community, and in consultation with them, in order to ensure success.