Perturbation and abrupt shift in trophic control of biodiversity and productivity

Ecology is founded on the view that ecosystem properties like biodiversity and productivity change smoothly with changing environmental conditions. However, emerging theory predicts that environmental change may cause abrupt shifts to alternate states. In many ecosystems, top predators play a pivotal role in controlling plant productivity and diversity. Yet it remains uncertain if altering this control shifts systems to alternate states. I report on a test of the hypothesis that loss of predator control of ecosystem function causes abrupt state changes in diversity and productivity. In this meadow ecosystem, predators enhance plant diversity by causing a highly productive, competitively dominant plant species to be suppressed by herbivores. Experimental predator removal caused rapid proliferation of the competitively dominant plant. Moreover, temporally staggered predator reintroductions failed to restore the ecosystem. This loss of resilience confirmed that the ecosystem crossed a critical threshold and entrained into an alternate state.     

Frequency of prenatal loss in a macaque breeding colony

An accurate knowledge of the historical incidence of prenatal loss is essential for management of breeding colonies and for performing developmental toxicity studies in nonhuman primates. Data from the California Regional Primate Research Center indoor (timed-mated) and outdoor (random-mated) colonies of rhesus, cynomolgus, and bonnet macaques (Macaca mulatta, M. fascicularis, and M. radiata) were evaluated for a 10 year breeding period from 1984 to 1993. Pregnancy outcome data for the three species of macaques summarized in this report indicate that early pregnancy as well as term are vulnerable periods of gestation in terms of prenatal loss. Prematurity as well as twinning were additionally associated with elevated rates of loss during the prenatal or neonatal period. The incidence of pregnancy failure did not appear to be related to different housing/management conditions (i.e., indoor timed-mated vs. outdoor random-mated), parity, animal handling, shipping, or relocation. Some of the annual fluctuations in abortions could be related to disease outbreaks (e.g., measles, pneumonia) in the colony. These data will be invaluable in planning for research needs which focus on developmental biology and perinatology, and in interpreting the significance of abortions following exposure to experimental agents in small numbers of animals. © 1996 Wiley-Liss, Inc.     

Detritivory: stoichiometry of a neglected trophic level

Previous syntheses have identified the key roles that phylogeny, body size, and trophic level play in determining arthropod stoichiometry. To date, however, detritivores have been largely omitted from such syntheses, despite their importance in nutrient cycling, biodiversity, and food web interactions. Here, we report on a compiled database of the allometry and nutritional stoichiometry (N and P) of detritivorous arthropods. Overall, both N and P content for detritivores varied among major phylogenetic lineages. Detritivore N content was similar to the N content of herbivores, but below that of predators. By contrast, detritivore P content was independent of trophic level. Contrary to previous reports, neither nutrient varied with body size. This analysis places detritivores in the context of related herbivores and predators, and as such, sets the stage for future investigations into the causes and consequences of elemental (mis)matches between detritivores and their detrital resources. Holly M. Martinson and Katie Schneider are co-first author.     

Ultrafast evolution and loss of CRISPRs following a host shift in a novel wildlife pathogen, Mycoplasma gallisepticum

Measureable rates of genome evolution are well documented in human pathogens but are less well understood in bacterial pathogens in the wild, particularly during and after host switches. Mycoplasma gallisepticum (MG) is a pathogenic bacterium that has evolved predominantly in poultry and recently jumped to wild house finches (Carpodacus mexicanus), a common North American songbird. For the first time we characterize the genome and measure rates of genome evolution in House Finch isolates of MG, as well as in poultry outgroups. Using whole-genome sequences of 12 House Finch isolates across a 13-year serial sample and an additional four newly sequenced poultry strains, we estimate a nucleotide diversity in House Finch isolates of only ～2% of ancestral poultry strains and a nucleotide substitution rate of 0.8-1.2×10(-5) per site per year both in poultry and in House Finches, an exceptionally fast rate rivaling some of the highest estimates reported thus far for bacteria. We also found high diversity and complete turnover of CRISPR arrays in poultry MG strains prior to the switch to the House Finch host, but after the invasion of House Finches there is progressive loss of CRISPR repeat diversity, and recruitment of novel CRISPR repeats ceases. Recent (2007) House Finch MG strains retain only ～50% of the CRISPR repertoire founding (1994-95) strains and have lost the CRISPR-associated genes required for CRISPR function. Our results suggest that genome evolution in bacterial pathogens of wild birds can be extremely rapid and in this case is accompanied by apparent functional loss of CRISPRs.     

Arthropod biodiversity loss and the transformation of a tropical agro-ecosystem

The coffee (Coffea arabica) agro-ecosystem in the Central Valley of Costa Rica was formerly characterized by a high vegetational diversity. This complex system has been undergoing a major transformation to capital-intensive monocultural plantations where all shade trees are eliminated. In this study we examined the pattern of arthropod biodiversity loss associated with this transformation. Canopy arthropods were sampled in three coffee farms: a traditional plantation with many species of shade trees, a moderately shaded plantation with only Erythrina poeppigeana and coffee, and a coffee monoculture. An insecticidal fogging technique was used to sample both canopy and coffee arthropods. Data are presented on three major taxonomic groups: Coleoptera, non-formicid Hymenoptera, and Formicidae. Data demonstrate that the transformation of the coffee agro-ecosystem results in a significant loss of biological diversity of both canopy arthropods as well as arthropods living in coffee bushes. Percentage of species overlap was very small for all comparisons. Furthermore, species' richness on a per tree basis was found to be within the same order of magnitude as that reported for trees in tropical forests. If results presented here are generalizable, this means that conservation efforts to preserve biological diversity should also include traditional agro-ecosystems as conservation units.     

Consequences of variation in plant defense for biodiversity at higher trophic levels

Antagonistic interactions between insect herbivores and plants impose selection on plants to defend themselves against these attackers. Although selection on plant defense traits has typically been studied for pairwise plant-attacker interactions, other community members of plant-based food webs are unavoidably affected by these traits as well. A plant trait might, for example, affect parasitoids and predators feeding on the herbivore. Consequently, defensive plant traits structure the diversity and composition of the complex community associated with the plant, and communities as a whole also feed back to selection on plant traits. Here, we review recent developments in our understanding of how plant defense traits structure insect communities and discuss how molecular mechanisms might drive community-wide effects.     

Valuing biodiversity and nature conservation at a local level

At a time where much of the discussion about major issues in nature conservation is necessarily undertaken at a global level, it is still important to consider the needs of the smaller organizations who do much of the grass roots work in the protection of wildlife and biodiversity. This study focuses on one such group, and examines how the contingent valuation method can be used to help to inform its decisions relating to the management of its portfolio of reserves in order to maximize benefits to its members. This paper argues that at a local level, where actions will not have significant global effects, contingent valuation methodology can inform decisions by assessing the value of additional reserves or particular conservation programmes to members in terms of their willingness to pay to acquire or implement them.     

Status of the long-tailed macaque Macaca fascicularis in Singapore and implications for management

The long-tailed macaque (Macaca fascicularis) population of the island-state of Singapore consists of ca. 1,218–1,454 individuals. About seventy percent of the population (ca. 1,027 individuals) is concentrated in both Bukit Timah and Central Catchment Nature Reserves, a system of reservoirs and forest reserves located in the center of Singapore. This core population resides mainly along perimeter forest areas of the reserve system, which is bordered by residential and recreational areas (e.g., parks and golf courses) and encircled by expressways. Periphery sub-populations (ca. 427 individuals) persist in forest fragments throughout Singapore mainland and on 5 offshore islands. Much of the Singaporean macaque population overlaps with human settlement and these commensal groups are mainly distributed close to roads, parks and residential areas. At least 70% of these groups are habituated to human presence and at least 50% to food provisioning. Moreover, commensal groups have more individuals and have higher infant:adult female ratios than non-commensal groups. The close association of habituated macaque groups living in human environments has led to increasing human-macaque conflict in Singapore. The overlap is also associated with human-induced population loss resulting from road accidents (2.4%); and trapping efforts (14%) aimed at ameliorating conflict issues. Consequently, it is important to better understand how humans are affecting macaque populations. In order to mitigate human-macaque conflict and at the same maintain a sustainable macaque population in Singapore, there is an urgent need for wildlife management strategies aimed at minimizing the extent of human–macaque conflict. Such strategies should include designing appropriate buffers around reserve areas, revised urban development plans, and managing the behavior of people interfacing with macaques.     

Testing hypotheses of trophic level interactions: a boreal forest ecosystem

Models of community organization involve variations of the top-down (predator control) or bottom-up (nutrient limitation) hypotheses. Verbal models, however, can be interpreted in different ways leading to confusion. Therefore, we predict from first principles the range of possible trophic level interactions, and define mathematically the instantaneous effects of experimental perturbations. Some of these interactions are logically and biologically unfeasible. The remaining set of 27 feasible models is based on an initial assumption, for simplicity, of linear interactions between trophic levels. Many more complex and non-linear models are logically feasible but, for parsimony, simple ones are tested first. We use an experiment in the boreal forest of Canada to test predictions of instantaneous changes to trophic levels and distinguish between competing models. Seven different perturbations systematically removed each trophic level or, for some levels, supplemented them. The predictions resulting from the perturbations were concerned with the direction of change in biomass in the other levels. The direct effects of each perturbation produced strong top-down and bottom-up changes in biomass. At both the vegetation and herbivore levels top-down was stronger than bottom-up despite some compensatory growth stimulated by herbivory. The combination of experiments produced results consistent with two-way (reciprocal) interactions at each level. Indirect effects on one or two levels removed from the perturbation were either very weak or undetectable. Top-down effects were strong when direct but attenuated quickly. Bottom-up effects were less strong but persisted as indirect effects to higher levels. Although the 'pure reciprocal' model best fits our results for the boreal forest system different models may apply to different ecosystems around the world.     

The role of biodiversity for element cycling and trophic interactions: an experimental approach in a grassland community

The focus of a new experiment, set up in Jena in spring 2002, are the effects of biodiversity on element cycles and the interaction of plant diversity with herbivores and soil fauna. The experimental design explicitly addresses criticisms provoked by previous biodiversity experiments. In particular, the choice of functional groups, the statistical separation of sampling versus complementarity effects, and testing for the effects of particular functional groups differ from previous experiments. Based on a species pool of 60 plant species common to the Central European Arrhenatherion grasslands, mixtures of one to 16 (60) species and of one to four plant functional groups were established on 90 plots (20 m × 20 m) with nested experiments. In order to test specific hypotheses 390 additional small-area plots (3.5 m × 3.5 m) were set-up. Exact replicates of all species mixtures serve to assess the variability in ecosystem responses. In a dominance experiment, the effects of interactions among nine selected highly productive species are studied. Each species is grown as monoculture replicated once.Effekte der Biodiversität auf Elementkreisläufe und Wechselwirkungen der pflanzlichen Artenvielfalt mit Bodenfauna und Herbivoren stehen im Mitttelpunkt eines neuen Experiments, das im Frühjahr 2002 in Jena eingerichtet wurde. Das Versuchsdesign berücksichtigt ausdrücklich die Kritik, die an den Aufbau früherer Biodiversitätsversuche gerichtet wurde. Die Auswahl funktioneller Gruppen von Pflanzenarten, die statistischen Möglichkeiten, die Effekte des “Sampling” gegen Komplementarität zu trennen sowie den Einfluß funktioneller Gruppen zu überprüfen, unterscheiden dieses Experiment von früheren Versuchen. Sechzig typische Pflanzenarten der zentraleuropäischen Frischwiesen (Arrhenatherion) bilden den Artenpool für den Versuch. Auf 90 Flächen wurden Artenmischungen etabliert, die 1 bis 16 (60) Arten und 1 bis 4 funktionelle Gruppen dieser Pflanzenarten enthalten. Die Versuchsparzellen haben eine Größe von 20 m × 20 m, auf denen in genesteter Anordnung verschiedene Teilexperimente durchgeführt werden. Zusätzlich wurden 390 kleine Parzellen (3.5 m × 3.5 m) angelegt, um spezifische Hypothesen zu überprüfen. Alle Arten werden hier mit je einer Wiederholung als Monokulturen kultiviert. Identische Wiederholungen aller Artenmischungen sollen deren Variabilität untersuchen. In einem Dominanz-Versuch werden die Effekte der Wechselwirkungen zwischen 9 ausgewählten hochproduktiven Arten untersucht.     

太平湖水库的浮游藻类与营养型评价

研究了太平湖水库的浮游藻类与营养类型。共发现藻类175种。绿藻门的种类最多(87种),占种类总数的50％。硅藻和蓝藻次之(分别为34和33种),各占19.4％和18.8％。其它5门藻合计21种,仅占种类总数的11.8％。根据营养型分析结果,太平湖目前水质优良,属中营养型水体;但是藻类的优势种类和总氮含量两项指标已达富营养水平,而且微囊藻(Microcystis)水体较多出现,表明该水体已有向富营养化发展的趋势。含磷量较低(总磷0.012mg/L)是浮游藻类进一步大量繁殖的限制因子。为防止水质恶化,除了应控制含氮化合物的污染外,限制磷的输入尤为重要。     

A decade of fertility below replacement level in Singapore

This paper discusses fertility trends in Singapore during the decade 1975-1984. Fertility 1st dropped below the replacement level in 1975 when the gross reproduction rate reached 1.006 and fell further to the low of 0.772 in 1984. During the same period all of the 3 main races, Chinese, Malays, and Indians, experienced fertility below replacement level. The shortfall in the number of births required to ensure replacement fertility increased during the decade until it approached 1/4 in 1984. This indicates that Singapore has more than achieved its national demographic goal of fertility to attain 0 growth and to stabilize the population in the future. This study shows that the newly introduced population policies designed to improve the quality of the population may well in practice lead to fewer births. A declining population in the 21st century is very likely.     

Invertebrate biodiversity in maize following withdrawal of triazine herbicides

Responses of key invertebrates within Farm Scale Evaluations (FSEs) of maize reflected advantageous effects for weeds under genetically modified herbicide-tolerant (GMHT) management. Triazine herbicides constitute the main weed control in current conventional systems, but will be withdrawn under future EU guidelines. Here, we reappraise FSE data to predict effects of this withdrawal on invertebrate biodiversity under alternative management scenarios. Invertebrate indicators showed remarkably consistent and sensitive responses to weed abundance. Their numbers were consistently reduced by atrazine used prior to seedling emergence, but at reduced levels compared to similar observations for weeds. Large treatment effects were, therefore, maintained for invertebrates when comparing other conventional herbicide treatments with GMHT, despite reduced differences in weed abundance. In particular, benefits of GMHT remained under comparisons with best estimates of future conventional management without triazines. Pitfall trapped Collembola, seed-feeding carabids and a linyphiid spider followed closely trends for weeds and may, therefore, prove useful for modelling wider biodiversity effects of herbicides. Weaker responses to triazines applied later in the season, at times closer to the activity and capture of invertebrates, suggest an absence of substantial direct effects. Contrary responses for some suction-sampled Collembola and the carabid Loricera pilicornis were probably caused by a direct deleterious effect of triazines.     

Mountain biodiversity conservation and management: a paradigm shift in policies and practices in the Hindu Kush-Himalayas

Mountains occupy 24% of the global land surface area and are home to 12% of the world’s population. They have ecological, aesthetic, and socioeconomic significance, not only for people living in mountain areas, but for those living beyond. Mountains need specific attention for their contribution to global goods and services, especially by developing and implementing mountain specific policies. Conservation policies have evolved from the protection of charismatic species, to habitat and ecosystem/landscape conservation, and, finally, to people-oriented conservation approaches. This paper, with particular reference to paradigm shifts in the Hindu Kush-Himalayan (HKH) region, discusses the evolution of conservation policies, developments in conservation practices, the status of protected area management, wetland conservation initiatives and the landscape approach, community-based conservation initiatives, and the convergence of policies and practices. In the HKH region, conservation efforts now adopt participatory approaches, implement policies of decentralised governance for biodiversity management, and empower local communities in biodiversity management. The paradigm shift in the policies and practices related to conservation has been gradual and has included the acceptance of communities as an integral part of national level conservation initiatives, together with the integration of many global conventions. There are many successful pilots in the HKH region that deserve upscaling by the countries from the region. Realising the importance of mountains as hotspots of biodiversity, and due to their role as providers of global goods and services, the Convention on Biological Diversity adopted the Programme of Work on Mountain Biodiversity. Such a decision specific to mountains provides enormous opportunities for both conservation and development. Recent challenges posed by climate change need to be integrated into overall biodiversity conservation and management agendas, especially in mountain areas. The HKH region has been identified as a blank spot for data by the Inter-Governmental Panel on Climate Change, indicating the need to develop regional database and sharing mechanisms. This is a tall task, but one that holds enormous opportunity for the HKH countries and institutions with regional mandates to address the emerging challenges of climate change on biodiversity conservation by reducing scientific uncertainty.