Melanie L. J. Stiassny

Freshwater biodiversity: importance, threats, status and conservation challenges

Freshwater biodiversity is the over‐riding conservation priority during the International Decade for Action ‐‘Water for Life’ ‐ 2005 to 2015. Fresh water makes up only 0.01% of the Worlds water and approximately 0.8 % of the Earths surface, yet this tiny fraction of global water supports at least 100 000 species out of approximately 1.8 million ‐ almost 6% of all described species. Inland waters and freshwater biodiversity constitute a valuable natural resource, in economic, cultural, aesthetic, scientific and educational terms. Their conservation and management are critical to the interests of all humans, nations and governments. Yet this precious heritage is in crisis. Fresh waters are experiencing declines in biodiversity far greater than those in the most affected terrestrial ecosystems, and if trends in human demands for water remain unaltered and species losses continue at current rates, the opportunity to conserve much of the remaining biodiversity in fresh water will vanish before the ‘Water for Life’ decade ends in 2015. Why is this so, and what is being done about it? This article explores the special features of freshwater habitats and the biodiversity they support that makes them especially vulnerable to human activities. We document threats to global freshwater biodiversity under five headings: overexploitation; water pollution; flow modification; destruction or degradation of habitat; and invasion by exotic species. Their combined and interacting influences have resulted in population declines and range reduction of freshwater biodiversity worldwide. Conservation of biodiversity is complicated by the landscape position of rivers and wetlands as ‘receivers’ of land‐use effluents, and the problems posed by endemism and thus non‐substitutability. In addition, in many parts of the world, fresh water is subject to severe competition among multiple human stakeholders. Protection of freshwater biodiversity is perhaps the ultimate conservation challenge because it is influenced by the upstream drainage network, the surrounding land, the riparian zone, and ‐ in the case of migrating aquatic fauna ‐ downstream reaches. Such prerequisites are hardly ever met. Immediate action is needed where opportunities exist to set aside intact lake and river ecosystems within large protected areas. For most of the global land surface, trade‐offs between conservation of freshwater biodiversity and human use of ecosystem goods and services are necessary. We advocate continuing attempts to check species loss but, in many situations, urge adoption of a compromise position of management for biodiversity conservation, ecosystem functioning and resilience, and human livelihoods in order to provide a viable long‐term basis for freshwater conservation. Recognition of this need will require adoption of a new paradigm for biodiversity protection and freshwater ecosystem management ‐ one that has been appropriately termed ‘reconciliation ecology’.

Freshwater Ecoregions of the World: A New Map of Biogeographic Units for Freshwater Biodiversity Conservation

ABSTRACT We present a new map depicting the first global biogeographic regionalization of Earths freshwater systems. This map of freshwater ecoregions is based on the distributions and compositions of freshwater fish species and incorporates major ecological and evolutionary patterns. Covering virtually all freshwater habitats on Earth, this ecoregion map, together with associated species data, is a useful tool for underpinning global and regional conservation planning efforts (particularly to identify outstanding and imperiled freshwater systems); for serving as a logical framework for large-scale conservation strategies; and for providing a global-scale knowledge base for increasing freshwater biogeographic literacy. Preliminary data for fish species compiled by ecoregion reveal some previously unrecognized areas of high biodiversity, highlighting the benefit of looking at the worlds freshwaters through a new framework.

Balancing hydropower and biodiversity in the Amazon, Congo, and Mekong

Basin-scale planning is needed to minimize impacts in mega-diverse rivers The worlds most biodiverse river basins—the Amazon, Congo, and Mekong—are experiencing an unprecedented boom in construction of hydropower dams. These projects address important energy needs, but advocates often overestimate economic benefits and underestimate far-reaching effects on biodiversity and critically important fisheries. Powerful new analytical tools and high-resolution environmental data can clarify trade-offs between engineering and environmental goals and can enable governments and funding institutions to compare alternative sites for dam building. Current site-specific assessment protocols largely ignore cumulative impacts on hydrology and ecosystem services as ever more dams are constructed within a watershed (1). To achieve true sustainability, assessments of new projects must go beyond local impacts by accounting for synergies with existing dams, as well as land cover changes and likely climatic shifts (2, 3). We call for more sophisticated and holistic hydropower planning, including validation of technologies intended to mitigate environmental impacts. Should anything less be required when tampering with the worlds great river ecosystems?

Taxonomic Impediment or Impediment to Taxonomy? A Commentary on Systematics and the Cybertaxonomic-Automation Paradigm

Marcelo R. de Carvalho AE Flavio A. Bockmann AE Dalton S. Amorim AE Carlos Roberto F. Brandao AE Mario de Vivo AE Jose L. de Figueiredo AE Heraldo A. Britski AE Mario C. C. de Pinna AE Naercio A. Menezes AE Fernando P. L. Marques AE Nelson Papavero AE Eliana M. Cancello AE Jorge V. Crisci AE John D. McEachran AE Robert C. Schelly AE John G. Lundberg AE Anthony C. Gill AE Ralf Britz AE Quentin D. Wheeler AE Melanie L. J. Stiassny AE Lynne R. Parenti AE Larry M. Page AE Ward C. Wheeler AE Julian Faivovich AE Richard P. Vari AE Lance Grande AE Chris J. Humphries AE Rob DeSalle AE Malte C. Ebach AE Gareth J. Nelson

Conserving Madagascar's Freshwater Biodiversity

Abstract The island nation of Madagascar, an international conservation priority, is now also recognized as a global hotspot for freshwater biodiversity. Three emerging characteristics of Madagascars threatened freshwater biota deserve increased attention from the scientific and conservation communities. First, species richness is not low, as was once assumed for both the freshwater fishes and the invertebrates. Second, many species are restricted to a specific region or even to single river basins. Often these species are also limited to streams or rivers draining primary forest habitat. Finally, many of the islands freshwater fishes are basal taxa, having diverged earlier than any other extant members of their clade. As such, these taxa assume disproportional phylogenetic importance. In the face of ongoing environmental threats, links among microendemism, forest stream specialization, and basal phylogenetic position highlight the importance and vulnerability of these species and provide a powerful incentive for immediate conservation action.

Genome-wide interrogation advances resolution of recalcitrant groups in the tree of life

Much progress has been achieved in disentangling evolutionary relationships among species in the tree of life, but some taxonomic groups remain difficult to resolve despite increasing availability of genome-scale data sets. Here we present a practical approach to studying ancient divergences in the face of high levels of conflict, based on explicit gene genealogy interrogation (GGI). We show its efficacy in resolving the controversial relationships within the largest freshwater fish radiation (Otophysi) based on newly generated DNA sequences for 1,051 loci from 225 species. Initial results using a suite of standard methodologies revealed conflicting phylogenetic signal, which supports ten alternative evolutionary histories among early otophysan lineages. By contrast, GGI revealed that the vast majority of gene genealogies supports a single tree topology grounded on morphology that was not obtained by previous molecular studies. We also reanalysed published data sets for exemplary groups with recalcitrant resolution to assess the power of this approach. GGI supports the notion that ctenophores are the earliest-branching animal lineage, and adds insight into relationships within clades of yeasts, birds and mammals. GGI opens up a promising avenue to account for incompatible signals in large data sets and to discern between estimation error and actual biological conflict explaining gene tree discordance.

Atavisms, Phylogenetic Character Reversals, and the Origin of Evolutionary Novelties

The occurrence of spontaneous atavisms (rare atavistic anomalies in individual specimens) and phylogenetic character reversals (expressed in all members of a given clade) are manifestations of the same phenomenon. The potential of the former to lend insight into underlying formative processes is generally recognized, but this is not the case with the latter. The way in which taxic atavisms (phylogenetic character reversals) are distributed within clades is of considerable interest. Part of this interest derives from the fact that within any lineage there is (potentially) a vast reservoir of plesiomorphic morphologies which may be re-expressed at various levels. The manner in which these features can and do reappear, often after protracted periods of time and over large taxonomic distances, should be of the greatest interest to evolutionary biologists. In addition to illuminating aspects of evolutionary transformation it is suggested that taxic atavism may be a mechanism of considerable importance in generating morphological variation within clades.

An Overview of Freshwater Biodiversity: With Some Lessons from African Fishes

Abstract As the twentieth century draws to a close, arguments about the viability of continued population growth, agricultural development, industrialization, and exhaustive resource use are intensifying. In perhaps no scientific arena are these issues more urgent than in the management of freshwater usage and aquatic conservation. As human populations continue to burgeon, the limits of the Earths freshwater resources are revealed more and more in the increasingly intense conflicts between human consumptive usage and the maintenance of aquatic health and biodiversity. Despite the fact that freshwater habitats comprise less than one-hundredth of a percent of the Earths water, the rivers, lakes, and wetlands of the planet harbor exceptional concentrations of biodiversity. While globally the true degree of aquatic impoverishment is largely unknown, these losses are doubtless already great. Much attention has been focused on worldwide losses of terrestrial biodiversity, particularly in tropical ecosystems, ...

Genetic isolation and morphological divergence mediated by high-energy rapids in two cichlid genera from the lower Congo rapids

BackgroundIt is hypothesized that one of the mechanisms promoting diversification in cichlid fishes in the African Great Lakes has been the well-documented pattern of philopatry along shoreline habitats leading to high levels of genetic isolation among populations. However lake habitats are not the only centers of cichlid biodiversity - certain African rivers also contain large numbers of narrowly endemic species. Patterns of isolation and divergence in these systems have tended to be overlooked and are not well understood.ResultsWe examined genetic and morphological divergence among populations of two narrowly endemic cichlid species, Teleogramma depressum and Lamprologus tigripictilis, from a 100 km stretch of the lower Congo River using both nDNA microsatellites and mtDNA markers along with coordinate-based morphological techniques. In L. tigripictilis, the strongest genetic break was concordant with measurable phenotypic divergence but no morphological disjunction was detected for T. depressum despite significant differentiation at mtDNA and nDNA microsatellite markers.ConclusionsThe genetic markers revealed patterns of philopatry and estimates of genetic isolation that are among the highest reported for any African cichlid species over a comparable geographic scale. We hypothesize that the high levels of philopatry observed are generated and maintained by the extreme hydrology of the lower Congo River.

The Quiet Crisis

Throughout most of human history, freshwater resources have been more than adequate to serve human needs while maintaining the integrity and biological diversity of Earth’s ecosystems. However, an exponentially increasing human population is placing ever greater demands on Earth’s limited supply of fresh waters. Already more than half of all accessible surface fresh water is put to use by humanity with concomitant degradation or loss of habitat such that Earth’s freshwater ecosystems have been altered more profoundly than have terrestrial ecosystems (Allan and Flecker, 1993; Postel et al., 1996; Stiassny, 1996, in press; Pimentai et al., 1997; Vitousek et al., 1997). Some particular examples serve to illustrate the gravity of the situation. In the United States, 98% of an estimated 5.2 million km of streams are sufficiently degraded to be unworthy of federal designation as wild or scenic rivers (Benke, 1990); industrial agriculture around the Aral Sea in the last 30 years has resulted in an approximate halving of the lake’s surface area and depth, and a tripling of its salinity (Mainguet and Letolle, 1997; Pimentai et al., 1997); only 2 of Japan’s 30,000 rivers are neither dammed nor modified in some way (McAllister et al., 1997). Undoubtedly these types of habitat degradation, often coupled with the deleterious effects of the introduction of exotic species (Courtenay and Moyle, 1992), have profound impacts on the resident biota. Although the precise degree of freshwater impoverishment remains to be fully documented, there can be little doubt that the losses are already great.