Showing papers on "Biodiversity published in 2000"

Biodiversity hotspots for conservation priorities

Abstract: Conservationists are far from able to assist all species under threat, if only for lack of funding. This places a premium on priorities: how can we support the most species at the least cost? One way is to identify 'biodiversity hotspots' where exceptional concentrations of endemic species are undergoing exceptional loss of habitat. As many as 44% of all species of vascular plants and 35% of all species in four vertebrate groups are confined to 25 hotspots comprising only 1.4% of the land surface of the Earth. This opens the way for a 'silver bullet' strategy on the part of conservation planners, focusing on these hotspots in proportion to their share of the world's species at risk.

Global biodiversity scenarios for the year 2100.

Abstract: Scenarios of changes in biodiversity for the year 2100 can now be developed based on scenarios of changes in atmospheric carbon dioxide, climate, vegetation, and land use and the known sensitivity of biodiversity to these changes. This study identified a ranking of the importance of drivers of change, a ranking of the biomes with respect to expected changes, and the major sources of uncertainties. For terrestrial ecosystems, land-use change probably will have the largest effect, followed by climate change, nitrogen deposition, biotic exchange, and elevated carbon dioxide concentration. For freshwater ecosystems, biotic exchange is much more important. Mediterranean climate and grassland ecosystems likely will experience the greatest proportional change in biodiversity because of the substantial influence of all drivers of biodiversity change. Northern temperate ecosystems are estimated to experience the least biodiversity change because major land-use change has already occurred. Plausible changes in biodiversity in other biomes depend on interactions among the causes of biodiversity change. These interactions represent one of the largest uncertainties in projections of future biodiversity change.

Consequences of changing biodiversity

Abstract: Human alteration of the global environment has triggered the sixth major extinction event in the history of life and caused widespread changes in the global distribution of organisms. These changes in biodiversity alter ecosystem processes and change the resilience of ecosystems to environmental change. This has profound consequences for services that humans derive from ecosystems. The large ecological and societal consequences of changing biodiversity should be minimized to preserve options for future solutions to global environmental problems.

The diversity–stability debate

Abstract: There exists little doubt that the Earth's biodiversity is declining. The Nature Conservancy, for example, has documented that one-third of the plant and animal species in the United States are now at risk of extinction. The problem is a monumental one, and forces us to consider in depth how we expect ecosystems, which ultimately are our life-support systems, to respond to reductions in diversity. This issue--commonly referred to as the diversity-stability debate--is the subject of this review, which synthesizes historical ideas with recent advances. Both theory and empirical evidence agree that we should expect declines in diversity to accelerate the simplification of ecological communities.

Biodiversity. Extinction by numbers

Abstract: Habitat destruction, especially of the humid forests in the tropics, is the main cause of the species extinctions happening now New work documents the uneven, highly clumped distribution of vulnerable species on the Earth, and pinpoints 25 so-called ‘biodiversity hotspots’ Seventeen of them are tropical forest areas, and here reduction of natural habitat is disproportionately high Nonetheless, identification of this pattern should enable resources for conservation to be better focused

Getting the measure of biodiversity

Abstract: The term 'biodiversity' is a simple contraction of 'biological diversity', and at first sight the concept is simple too: biodiversity is the sum total of all biotic variation from the level of genes to ecosystems. The challenge comes in measuring such a broad concept in ways that are useful. We show that, although biodiversity can never be fully captured by a single number, study of particular facets has led to rapid, exciting and sometimes alarming discoveries. Phylogenetic and temporal analyses are shedding light on the ecological and evolutionary processes that have shaped current biodiversity. There is no doubt that humans are now destroying this diversity at an alarming rate. A vital question now being tackled is how badly this loss affects ecosystem functioning. Although current research efforts are impressive, they are tiny in comparison to the amount of unknown diversity and the urgency and importance of the task.

Human population in the biodiversity hotspots.

Abstract: Biologists have identified 25 areas, called biodiversity hotspots, that are especially rich in endemic species and particularly threatened by human activities. The human population dynamics of these areas, however, are not well quantified. Here we report estimates of key demographic variables for each hotspot, and for three extensive tropical forest areas that are less immediately threatened. We estimate that in 1995 more than 1.1 billion people, nearly 20% of world population, were living within the hotspots, an area covering about 12% of Earth's terrestrial surface. We estimate that the population growth rate in the hotspots (1995-2000) is 1.8% yr(-1), substantially higher than the population growth rate of the world as a whole (1.3% yr(-1)) and above that of the developing countries (1.6% yr(-1)). These results suggest that substantial human-induced environmental changes are likely to continue in the hotspots and that demographic change remains an important factor in global biodiversity conservation. The results also underline the potential conservation significance of the continuing worldwide declines in human fertility and of policies and programs that influence human migration.

Pervasive density-dependent recruitment enhances seedling diversity in a tropical forest

Abstract: Negative density-dependent recruitment of seedlings, that is, seeds of a given species are less likely to become established seedlings if the density of that species is high, has been proposed to be an important mechanism contributing to the extraordinary diversity of tropical tree communities1,2,3 because it can potentially prevent any particular species from usurping all available space, either in close proximity to seed sources or at relatively larger spatial scales1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18. However, density-dependent recruitment does not necessarily enhance community diversity14. Furthermore, although density-dependent effects have been found at some life stages in some species3,4,5,6,7,8,9,10,11,12,13, no study has shown that density-dependent recruitment affects community diversity14,15. Here we report the results of observations in a lowland, moist forest in the Republic of Panama in which the species identities of 386,027 seeds that arrived at 200 seed traps were compared with the species identities of 13,068 seedlings that recruited into adjacent plots over a 4-year period. Across the 200 sites, recruit seedling diversity was significantly higher than seed diversity. Part of this difference was explained by interspecies differences in average recruitment success. Even after accounting for these differences, however, negative density-dependent recruitment contributes significantly to the increase in diversity from seeds to seedling recruits.

Biodiversity and ecosystem functioning: recent theoretical advances

Abstract: The relationship between biodiversity and ecosystem functioning has emerged as a major scientific issue today. As experiments progress, there is a growing need for adequate theories and models to provide robust interpretations and generalisations of experimental results, and to formulate new hypotheses. This paper provides an overview of recent theoretical advances that have been made on the two major questions in this area: (1) How does biodiversity affect the magnitude of ecosystem processes (short-term effects of biodiversity)? (2) How does biodiversity contribute to the stability and maintenance of ecosystem processes in the face of perturbations (long-term effects of biodiversity)? Positive short-term effects of species diversity on ecosystem processes, such as primary productivity and nutrient retention, have been explained by two major types of mechanisms: (1) functional niche complementarity (the complementarity effect), and (2) selection of extreme trait values (the selection effect). In both cases, biodiversity provides a range of phenotypic trait variation. In the complementarity effect, trait variation then forms the basis for a permanent association of species that enhances collective performance. In the selection effect, trait variation comes into play only as an initial condition, and a selective process then promotes dominance by species with extreme trait values. Major differences between within-site effects of biodiversity and across-site productivity–diversity patterns have also been clarified. The local effects of diversity on ecosystem processes are expected to be masked by the effects of varying environmental parameters in across-site comparisons. A major reappraisal of the paradigm that has dominated during the last decades seems necessary if we are to account for long-term effects of biodiversity on ecosystem functioning. The classical deterministic, equilibrium approaches to stability do not explain the reduced temporal variability of aggregate ecosystem properties that has been observed in more diverse systems. On the other hand, stochastic, nonequilibrium approaches do show two types of biodiversity effects on ecosystem productivity in a fluctuating environment: (1) a buffering effect, i.e., a reduction in the temporal variance; and (2) a performance-enhancing effect, i.e., an increase in the temporal mean. The basic mechanisms involved in these long-term insurance effects are very similar to those that operate in short-term biodiversity effects: temporal niche complementarity, and selection of extreme trait values. The ability of species diversity to provide an insurance against environmental fluctuations and a reservoir of variation allowing adaptation to changing conditions may be critical in a long-term perspective. These recent theoretical developments in the area of biodiversity and ecosystem functioning suggest that linking community and ecosystem ecology is a fruitful avenue, which paves the way for a new ecological synthesis.

Indicators of biodiversity for ecologically sustainable forest management

Abstract: The conservation of biological diversity has become one of the important goals of managing for- ests in an ecologically sustainable way. Ecologists and forest resource managers need measures to judge the success or failure of management regimes designed to sustain biological diversity. The relationships between potential indicator species and total biodiversity are not well established. Carefully designed studies are re- quired to test relationships between the presence and abundance of potential indicator species and other taxa and the maintenance of critical ecosystem processes in forests. Other indicators of biological diversity in forests, in addition or as alternatives to indicator species, include what we call structure-based indicators. These are stand-level and landscape-level (spatial) features of forests such as stand structural complexity and plant species composition, connectivity, and heterogeneity. Although the adoption of practices to sustain (or recreate) key characteristics of forest ecosystems appear intuitively sensible and broadly consistent with cur- rent knowledge, information is lacking to determine whether such stand- and landscape-level features of for- ests will serve as successful indices of (and help conserve) biodiversity. Given our limited knowledge of both indicator species and structure-based indicators, we advocate the following four approaches to enhance biodiversity conservation in forests: (1) establish biodiversity priority areas (e.g., reserves) managed prima- rily for the conservation of biological diversity; (2) within production forests, apply structure-based indica- tors including structural complexity, connectivity, and heterogeneity; (3) using multiple conservation strate- gies at multiple spatial scales, spread out risk in wood production forests; and (4) adopt an adaptive management approach to test the validity of structure-based indices of biological diversity by treating man- agement practices as experiments. These approaches would aim to provide new knowledge to managers and improve the effectiveness of current management strategies.

Hotspots: Earth's Biologically Richest and Most Endangered Terrestrial Ecoregions

Abstract: Polynesia, the mountains of south-central China, the coastal forest of Tanzania, New Zealand - all are breathtakingly beautiful sites with a crucial fact in common. They are four of the Earth's 25 "hotspots", geographical areas which, according to scientists and naturalists, are home to the world's greatest plant and animal diversity. The numbers are staggering: fully 60 percent of all terrestrial animal and plant species are found in these hotspots, which are themselves only 1.4 percent of the Earth's surface; they contain 54 percent of amphibian species and nearly half of all the plant species on Earth. They are the richest and most threatened reservoirs of plant and animal life on Earth. "Hotspots" is the definitive compilation and status report on these 25 areas. Russell Mittermeier, Cristina Goettsch Mittermeier and Norman Myers, who pioneered the "hotspots" concept, take you through each of these regions, describing the various ecosystems and the threats to their existence. They have gathered the work of more than one hundred international experts on plant and animal life together with hundreds of spectacular colour photographs, essentially creating a tour of the magnificent array of life found in each region. How we address and reverse the tide of destruction in coming decades will determine the planet's course for centuries to come, and "Hotspots" actually offers hope that this destruction can be slowed. By showcasing the specific areas that contain the greatest diversity, it demonstrates that we can conserve a major share of this terrestrial biodiversity by focusing efforts on relatively small geographical areas. "Hotspots" is not only an important work for conservationists; it is also an extraordinary view of life on Earth.

Encyclopedia of Biodiversity

Abstract: First used in 1980, "biodiversity" often describes the abundance, variety, and genetic constitution of native animals and plants, and has been linked with politics and environmental technology. Although the 1986 National forum on biodiversity brought issues of biodiversity to the fore, the inescapable need to know more about the diversity of life on Earth continues to remain unmet. In recent years, biodiversity has influenced important scientific considerations, international agreements, conventions, conservation initiatives, political debates, and socio-economic implications. Knowledge derived from the study of biodiversity will affect the quality of life enjoyed in the future by influencing decision-making processes and aiding new discoveries. The science of biodiversity has become the science of our future. Our awareness of the loss of biodiversity has brought a long overdue appreciation of the magnitude of our loss and a determination to develop the tools to protect our future. "The Encyclopedia of Biodiversity, 2/e" has been updated to provide a timely study of the dimensions of diversity. It examines the services biodiversity provides, and the measures in which to protect it. Major themes of the work include the evolution of biodiversity, systems for classifying and defining biodiversity, ecological patterns and theories of biodiversity, and an assessment of contemporary patterns and trends in biodiversity. This Revised edition includes over 100 new articles and 226 updated articles covering this multidisciplinary field - from evolution to habits to economics. The editors for this second edition are all well respected, instantly recognizable academics operating at the top of their respective fields in biodiversity research. Readers can be assured that they are reading material that has been meticulously checked and reviewed by experts. Approximately 1,000 figures and tables complement the text, and more than 3,000 glossary entries explain key terms.

Abundance–occupancy relationships

Abstract: 1. The abundance and distribution of species tend to be linked, such that species declining in abundance often tend also to show declines in the number of sites they occupy, while species increasing in abundance tend also to be increasing in occupancy. Therefore, intraspecific abundance–occupancy relationships are commonly positive. 2. The intraspecific pattern is mirrored by more general positive interspecific abundance–occupancy relationships: widespread species tend to be abundant, and narrowly distributed species rare. 3. Here, we review recent research on these patterns based on the flora and fauna of the British Isles. We assess their generality, describe what is currently known about their structure, and summarize the results of tests of the several hypotheses proposed to explain their existence. 4. The positive form generally exhibited by abundance–occupancy relationships, intraspecific or interspecific, has consequences for several areas of applied ecology, including conservation, harvesting, biological invasions and biodiversity inventorying. These implications are discussed briefly.

Linking biodiversity to ecosystem function: implications for conservation ecology

Abstract: We evaluate the empirical and theoretical support for the hypothesis that a large proportion of native species richness is required to maximize ecosystem stability and sustain function. This assessment is important for conservation strategies because sustenance of ecosystem functions has been used as an argument for the conservation of species. If ecosystem functions are sustained at relatively low species richness, then arguing for the conservation of ecosystem function, no matter how important in its own right, does not strongly argue for the conservation of species. Additionally, for this to be a strong conservation argument the link between species diversity and ecosystem functions of value to the human community must be clear. We review the empirical literature to quantify the support for two hypotheses: (1) species richness is positively correlated with ecosystem function, and (2) ecosystem functions do not saturate at low species richness relative to the observed or experimental diversity. Few empirical studies demonstrate improved function at high levels of species richness. Second, we analyze recent theoretical models in order to estimate the level of species richness required to maintain ecosystem function. Again we find that, within a single trophic level, most mathematical models predict saturation of ecosystem function at a low proportion of local species richness. We also analyze a theoretical model linking species number to ecosystem stability. This model predicts that species richness beyond the first few species does not typically increase ecosystem stability. One reason that high species richness may not contribute significantly to function or stability is that most communities are characterized by strong dominance such that a few species provide the vast majority of the community biomass. Rapid turnover of species may rescue the concept that diversity leads to maximum function and stability. The role of turnover in ecosystem function and stability has not been investigated. Despite the recent rush to embrace the linkage between biodiversity and ecosystem function, we find little support for the hypothesis that there is a strong dependence of ecosystem function on the full complement of diversity within sites. Given this observation, the conservation community should take a cautious view of endorsing this linkage as a model to promote conservation goals.

How do depth, duration and frequency of flooding influence the establishment of wetland plant communities?

Abstract: In many temporary wetlands such as those on the Northern Tablelands of New South Wales Australia, the development of plant communities is largely the result of germination and establishment from a long-lived, dormant seed bank, and vegetative propagules that survive drought. In these wetlands the pattern of plant zonation can differ from year to year and season to season, and depth is not always a good indicator of the plant community composition in different zones. In order to determine which aspects of water regime (depth, duration or frequency of flooding) were important in the development of plant communities an experiment using seed bank material from two wetlands was undertaken over a 16 week period in late spring–early summer 1995–1996. Seed bank samples were exposed to 17 different water-level treatments with different depths, durations and frequencies of flooding. Species richness and biomass of the communities that established from the seed bank were assessed at the end of the experiment and the data were examined to determine which aspects of water regime were important in the development of the different communities. It was found that depth, duration and frequency of inundation influenced plant community composition, but depth was least important, and also that the duration of individual flooding events was important in segregating the plant communities. Species were grouped according to their ability to tolerate or respond to fluctuations in flooding and drying. The highest biomass and species richness developed in pots that were never flooded. Least biomass and species richness developed in pots that were continuously flooded. Short frequent floods promoted high species richness and biomass especially of Amphibious fluctuation-tolerator species and Amphibious fluctuation-responder species that have heterophylly. Terrestrial species were able to establish during dry phases between short floods. Depth was important in determining whether Amphibious fluctuation-tolerator or Amphibious fluctuation-responder species had greater biomass. Longer durations of flooding lowered species richness and the biomass of terrestrial species. Experiments of this kind can assist in predicting vegetation response to water-level variation in natural and modified wetlands.

Umbrellas and flagships: Efficient conservation surrogates or expensive mistakes?

Abstract: The use of umbrella and flagship species as surrogates for regional biota whose spatial distributions are poorly known is a popular conservation strategy. Yet many assumptions underlying the choice of surrogate species remain untested. By using biodiversity databases containing spatial incidence data for species of concern for (i) the southern California coastal sage scrub habitat, (ii) the Columbia Plateau ecoregion, and (iii) the continental United States, we evaluate the potential effectiveness of a range of conservation surrogate schemes (e.g., big carnivores, charismatic species, keystone species, wide-ranging species), asking how many species potentially are protected by each scheme and at what cost in each habitat area. For all three databases, we find that none of the surrogate schemes we evaluated performs significantly better than do a comparable number of species randomly selected from the database. Although some surrogate species may have considerable publicity value, based on the databases we analyzed, representing diverse taxa on three different geographic scales, we find that the utility of umbrella and flagship species as surrogates for regional biodiversity may be limited.

Introduction: The Brazilian Atlantic Forest1

Abstract: The year 2000 marks 500 years of massive destruction for the Brazilian Atlantic Forest, as a consequence of the European colonization of Brazil. Today, the Atlantic Forest is restricted to ca 98,800 km2 of remnants, or 7.6 percent of its original extension. The Atlantic Forest continues to suffer under severe anthropogenic pressure, risking imminent extinction of the remaining species. Our current knowledge indicates that this complex biome contains a species diversity higher than most of the Amazon forests, and also has high levels of endemism. The 13 selected articles in this special issue present data on the natural history, ecology, sustainable management, and conservation of the Atlantic Forest. These articles represent a sample of the research conducted to date in the region and suggest avenues of future research, particularly with regard to conservation alternatives for the remaining portions of the Atlantic Forest. This special issue represents one of the first general references pertaining to the Brazilian Atlantic Forest.

Ecosystem response of pasture soil communities to fumigation-induced microbial diversity reductions: an examination of the biodiversity-ecosystem function relationship

Abstract: A technique based on progressive fumigation was used to reduce soil microbial biodiversity, and the effects of such reductions upon the stability of key soil processes were measured. Mineral soil samples from a grassland were fumigated with chloroform for up to 24 h and then incubated for 5 months to allow recolonisation by surviving organisms. The diversity of cultivable and non-cultivable bacteria, protozoa and nematodes was progressively reduced by increasing fumigation times, as was the number of trophic groups, phyla within trophic groups, and taxa within phyla. Total microbial biomass was similar within fumigated soils, but lower than for unfumigated soil. There was no direct relationship between biodiversity and function. Some broad-scale functional parameters increased as biodiversity decreased, e.g. thymidine incorporation, growth on added nutrients, and the decomposition rate of plant residues. Other more specific parameters decreased as biodiversity decreased, e.g. nitrification, denitrification and methane oxidation. Thus specific functional parameters may be a more sensitive indicator of environmental change than general parameters. Although fumigation reduced soil microbial biodiversity, there was evidence to suggest that it selected for organisms with particular physiological characteristics. The consequences of this for interpreting biodiversity – function relationships are discussed. The stability of the resulting communities to perturbation was further examined by imposing a transient (brief heating to 40°C) or a persistent (addition of CuSO4) stress. Decomposition of grass residues was determined on three occasions after such perturbations. The soils clearly demonstrated resilience to the transient stress; decomposition rates were initially depressed by the stress and recovered over time. Resilience was reduced in the soils with decreasing biodiversity. Soils were not resilient to the persistent stress, there was no recovery in decomposition rate over time, but the soils with the highest biodiversity were more resistant to the stress than soils with impaired biodiversity. The study of functional stability under applied perturbation is a powerful means of examining the effects of biodiversity.

Elevated CO2 increases productivity and invasive species success in an arid ecosystem.

Abstract: Arid ecosystems, which occupy about 20% of the earth's terrestrial surface area, have been predicted to be one of the most responsive ecosystem types to elevated atmospheric CO2 and associated global climate change1,2,3. Here we show, using free-air CO2 enrichment (FACE) technology in an intact Mojave Desert ecosystem4, that new shoot production of a dominant perennial shrub is doubled by a 50% increase in atmospheric CO2 concentration in a high rainfall year. However, elevated CO2 does not enhance production in a drought year. We also found that above-ground production and seed rain of an invasive annual grass increases more at elevated CO2 than in several species of native annuals. Consequently, elevated CO2 might enhance the long-term success and dominance of exotic annual grasses in the region. This shift in species composition in favour of exotic annual grasses, driven by global change, has the potential to accelerate the fire cycle, reduce biodiversity and alter ecosystem function in the deserts of western North America.

Large-scale processes and the Asian bias in species diversity of temperate plants

Abstract: An important issue in the study of biodiversity is the extent to which global patterns of species richness reflect large-scale processes and historical contingencies1,2. Ecological interactions in local assemblages may constrain the number of species that can coexist3,4, but differences in diversity in similar habitats within different regions (diversity anomalies) suggest that this limit is not firm. Variation in rate of species production could influence regional and perhaps local diversity independently of the ecological capacity of an area to support coexisting species, thereby creating diversity anomalies5,6. Temperate Zone genera of plants that are disjunct between similar environments in eastern Asia and eastern North America (EAS-ENA) have twice as many species in Asia as in North America7. Because lineages of these genera in Asia and North America are mostly sister pairs8, they share a common history of adaptation and ecological relationship before disjunction. Thus, the diversity anomaly in EAS-ENA genera is not an artefact of taxon or habitat sampling but reflects differences in the net diversification (speciation–extinction) of the lineages in each of the continents. Here we propose that the most probable cause of the EAS-ENA anomaly in diversity is the extreme physiographical heterogeneity of temperate eastern Asia, especially compared with eastern North America, which in conjunction with climate and sea-level change has provided abundant opportunities for evolutionary radiation through allopatric speciation.

Causes, consequences and ethics of biodiversity

Abstract: The existence of so great a diversity of species on Earth remains a mystery, the solution to which may also explain why and how biodiversity influences the functioning of ecosystems. The answer may lie in quantifying the trade-offs that organisms face in dealing with the constraints of their environment. Societal responses to the loss of biodiversity also involve trade-offs, and the elaboration of these will be essential in developing wiser environmental ethics and policy.

The diversity of parasites.

Abstract: Parasitism is one of the most successful modes of life displayed by living organisms, as measured by how often it evolved and how many parasitic species are presently in existence. Studying the diversity of parasites is particularly relevant because sympatric diversification may be important in some parasite taxa, and because of the opportunity for independent tests of evolutionary hypotheses in the many separate lineages in which parasitism evolved. Our incomplete knowledge of existing parasite species--the result of a range of phenomena that includes inadequate sampling effort or the lumping of different cryptic species under one name--is not always a major obstacle for the study of parasite diversity. Patterns in the diversity of parasites may be associated with either host or parasite characteristics. The distribution of parasite diversity among host taxa does not simply reflect the species diversity of the host taxa themselves; life history and ecological traits of hosts appear to play important roles. These may determine the likelihood that hosts are colonized by parasite species over evolutionary time. It is not yet clear whether some host traits also favor intrahost speciation and diversification of parasites, and the formation of new parasite species. Certain features of parasites may also be associated with speciation and diversification. Only parasite body size has received much attention; the patterns observed are not greatly different from those of free-living species, with small-bodied parasite taxa being more speciose than related large-bodied taxa. Epidemiological parameters such as the basic reproductive rate of parasites, or R0, can also generate predictions regarding the distribution or evolution of parasite diversity. For instance, parasite taxa characterized by high R0 values may be more speciose than related taxa with lower values of R0; such predictions remain untested. Large-scale biogeographical patterns of diversity have only been well studied for metazoan parasites of marine fish; for these parasites, latitudinal patterns can be explained by effects of temperature on speciation rates and epidemiological variables, though other causes are possible. The emphasis for future research must shift from pattern description to the elucidation of the processes responsible for the structure and diversity of parasite faunas. A better integration of ecological and historical (or phylogenetic) approaches to the study of parasite diversity should make this objective possible.

Nonrandom Extinction and the Loss of Evolutionary History

Abstract: The hierarchical nature of phylogenies means that random extinction of species affects a smaller fraction of higher taxa, and so the total amount of evolutionary history lost may be comparatively slight. However, current extinction risk is not phylogenetically random. We show the potentially severe implications of the clumped nature of threat for the loss of biodiversity. An additional 120 avian and mammalian genera are at risk compared with the number predicted under random extinction. We estimate that the prospective extra loss of mammalian evolutionary history alone would be equivalent to losing a monotypic phylum.

The relationship in lake communities between primary productivity and species richness

Abstract: An understanding of the relationship between species richness and productivity is crucial to understanding biodiversity in lakes. We investigated the relationship between the primary productivity of lake ecosystems and the number of species for lacustrine phytoplankton, rotifers, cladocerans, copepods, macrophytes, and fish. Our study includes two parts: (1) a survey of 33 well-studied lakes for which data on six major taxonomic groups were available; and (2) a comparison of the effects of short- and long-term whole-lake nutrient addition on primary productivity and planktonic species richness. In the survey, species richness of all six taxa showed a significant quadratic response to increased annual primary productivity ( 14 C estimate, g C-m -2 -yr -1 ) when lake area is taken into account. However, the richness-productivity relationship for phytoplankton and fish was strongly dependent on lake area. The relationship for phytoplankton, rotifers, cladocerans, copepods, and macrophytes was significantly unimodal. Species richness generally peaked at levels of primary productivity in the range of 30-300 g C-m -2 -yr -1 . For the average lake size, the highest biodiversity tended to occur in lakes with relatively low primary productivity, such as those found in the Northern Temperate Lakes Long-Term Ecological Research (LTER) site in the upper Midwest (United States) and in the Experimental Lakes Area of Ontario (Canada). Based on short-term (3 yr) and long-term (21-24 yr) experiments, we tested whether individual lakes respond to whole-lake enrichment experiments in the manner suggested by analyses of survey data. Experimental addition of nutrients produced varied and unpredictable responses in species richness, probably due to transient dynamics and time lags. Responses to nutrient addition were taxon and lake specific. Phytoplankton showed a variety of relationships between species richness and pelagic primary productivity (PPR), depending on the history of enrichment and recovery. No significant effect of primary productivity on rotifer richness occurred in any of the experimental lakes, whereas richness of crustacean zooplankton was negatively correlated with primary productivity in both the short- and long-term experiments.

Bat Diversity and Abundance as Indicators of Disturbance in Neotropical Rainforests

Abstract: Evaluating the degree of disturbance of any region to determine its relative importance for conservation purposes requires procedures that are relatively inexpensive and that yield accurate results fast. Because bats are abundant, diverse, and easy to sample, especially in the Neotropical rainforest, they fulfill several of the requirements of indicator species as identified in the literature. For 10 months we sampled bat communities in the Selva Lacandona in Chiapas, Mexico, at 15 sites representing five habitats. We also measured 10 variables representing vegetation structure and diversity at each site. With fuzzy-set techniques we produced a gradient classification of disturbance for the 15 sites based on the vegetation data. We explored the relationship between vegetation conditions, described as the membership degrees in the construct “fuzzy forest set” (the complementary fuzzy set of “disturbance”), and four bat community variables. Bat species richness, number of rare bat species, and the bat diversity index were positively correlated with the vegetation scores, and relative abundance of the most abundant bat species was negatively correlated with vegetation scores. A high number of phyllostomine species in a community is a good indicator of low levels of disturbance. Although a single indicator group will probably not be sufficient for decision-making processes in conservation, evaluating bat populations may be a good first step in assessing an area's conservation value, especially in rainforest regions.