Quantifying the dynamics of marine invertebrate metacommunities: What processes can maintain high diversity with low densities in the Mediterranean Sea?

The Mediterranean Sea hosts 5.6% of the world benthic invertebrate species on 0.82% of the ocean surface. Mediterranean ecosystems are also characterized by low densities (and biomasses) compared to other oceanic ecosystems, a feature often attributed to their oligotrophic environment. Oligotrophic conditions can induce lower growth rates and higher mortality rates, and a stronger competition for food between individuals. A theoretical model was developed in order to study the diversity vs. density patterns in coastal benthic invertebrate species. This model describes their minimal population dynamics including basic processes (growth, mortality, reproduction and effects of competitive interactions between individuals) and incorporating fluxes of larvae (finally recruited as juveniles) between a mosaic of local habitats. Populations are therefore structured in a metacommunity. The connectivity between local communities is ensured by passive pelagic larval dispersal. In the Mediterranean Sea, because of the microtidal regime, the connectivity between coastal habitats is lower and more variable than in macrotidal basins. Mathematical properties of the model revealed that competitive interactions (intra- and interspecific competitions) have a stabilizing effect on interacting organisms when gains by recruitment are higher than losses by mortality. In addition, low mortality rates and low connectivity which decreases negative local interactions maintains high regional species diversity with low local densities. This property suggested that oligotrophy cannot be the only factor leading to the high diversity–low density pattern observed in the Mediterranean Sea.     

Phenology and population radiation of the nettle caterpillar, Darna pallivitta (Moore) (Lepidoptera: Limacodidae) in Hawai’i

The nettle caterpillar, Darna pallivitta (Moore) (Lepidoptera: Limacodidae), is an invasive pest with established populations on three Hawai’ian islands. Indigenous to Southeast Asia, D. pallivitta caterpillars cause defoliation of ornamental nursery stock and pose a human health hazard due to their urticating hairs that can cause painful skin reactions. Identification of the pheromone component n-butyl (E)-7,9-decadienoate (E7,9-10:COOnBu) from D. pallivitta has made it possible to investigate the phenology and population dynamics using baited traps. Male captures in Jackson traps baited with E7,9-10:COOnBu showed a vegetation preference for tall-grass fields and forest/grass interfaces over forest areas. Microlocation preferences were also found for trap height, with over 65% of males being caught in traps suspended at 1 m, compared with the traps at 3 and 5 m. Captures of male moths in traps baited with live females, and direct observations of female calling behavior, showed peak activities 6–7 h after the onset of scotophase. This is a much later communication period than for D. bradleyi and D. trima and may provide a mechanism by which D. pallivitta maintains reproductive isolation in areas where all three species are present. Coastal and inland transects established in eastern Hawai’i measured aspects of population fluctuations and radiation into new areas with relation to elevation and microclimate. Population expansion was measured by comparing moth population means and 80% population boundaries over time. Both population measures showed a higher expansion for the coastal transect. Differences in population expansion may be attributed in part to temperature and elevation, while precipitation does not seem to have a strong effect. Both the behavioral and ecological data collected can be used to optimize deployment of detection/control strategies and to predict population expansion/risk assessment for establishing quarantine protocols for the nettle caterpillar.     

Generation time and the maximum growth rate for populations with age-specific fecundities and unknown juvenile survival

In age-classified population models where all parameters are known, the generation time and growth rate are calculated in a straightforward manner. For many populations, some parameters, such as juvenile survival, are difficult to estimate accurately. In a simplified population model where fecundity and survival are constant from the onset of breeding, it is known that generation time may be calculated given only adult survival, age at first reproduction, and the population growth rate. However, the assumption of constant fecundity from the onset of breeding does not hold for many populations. An extended population model allows calculation of generation time with the additional knowledge of the ratio of age-specific fecundities compared to a maximum fecundity rate. When these relative fecundities are unknown, an ad hoc adjustment to the simplified model performs well.When the study population is in an ideal environment, the optimal generation time and maximum growth rate are linked, and both may be approximated knowing only adult survival, age at first reproduction, and the relative fecundities. The maximum growth rate has important conservation implications, and calculating it correctly is therefore important. Improper use of the simplified population model to calculate the maximum growth rate, combined with a simple decision rule, leads to an average overharvest of 36%, and >60% for three of six bird species studied, compared to the full population model. By comparison, using the approximation from the extended or adjusted models results in average overharvests of only 8% (extended model) and 5% (adjusted model), and <50% for all six species (either model).     

Choosing classes for size projection matrix models

Projection matrix models are intensely used in ecology to model the dynamics of structured populations. When dealing with size-structured populations, there is no satisfactory algorithm to partition size into discrete classes. We show that the Vandermeer-Moloney algorithm for choosing classes is inconsistent with the Usher model, and systematically selects the finest classes. Considering that the matrix model is a discrete approximation of a continuous model, we define an approximation error as the sum of a distribution error (the difference between the discrete distribution and its continuous counterpart), and a sample error. The optimal partition of size into classes is the one that minimizes the approximation error. This method for choosing classes also shows that the choice of the class width cannot be disconnected from the choice of the time step. When applied to 520 trees of Dicorynia guianensis in French Guiana, this algorithm identified 8 classes of 11.4 cm in width, which is in agreement with the empirical choice of foresters.     

Estimating biodiversity impacts without field surveys: A case study in northern Borneo

In many regions of the world, biodiversity surveys are not routinely conducted prior to activities that lead to land conversion, such as development projects. Here we use top-down methods based on global range maps and bottom-up methods based on macroecological scaling laws to illuminate the otherwise hidden biodiversity impacts of three large hydroelectric dams in the state of Sarawak in northern Borneo. Our retrospective impact assessment finds that the three reservoirs inundate habitat for 331 species of birds (3 million individuals) and 164 species of mammals (110 million individuals). A minimum of 2100 species of trees (900 million individuals) and 17 700 species of arthropods (34 billion individuals) are estimated to be affected by the dams. No extinctions of bird, mammal, or tree species are expected due to habitat loss following reservoir inundation, while 4–7 arthropod species extinctions are predicted. These assessment methods are applicable to any data-limited system undergoing land-use change.

Electronic supplementary material

The online version of this article (doi:10.1007/s13280-015-0683-3) contains supplementary material, which is available to authorized users.     

The environmental impacts of regional disparity in population and wealth distribution in Nigeria

The disparity in both population and wealth distribution in Nigeria by geo-political zones is well recognized. There is also the recognition that some of the environmental problems in certain sections of the country can be attributed to the imbalance in both population and wealth distribution. Hence the various agitations for environmental resource control in the country. What is lacking however is the research that shows the magnitude of the linkages between the disparity and the environmental degradation in regional context. This provides the basis for this research. To achieve the aim of the research, a STIRPAT model was employed as an analytical tool. The findings show that the southern geopolitical zones are generally more densely populated and wealthier than the northern zones. The south is also experiencing a higher degree of environmental resource degradation attributable to anthropogenic factors. Thus, there is congruence between population density, wealth distribution and environmental degradation in Nigeria. Therefore the achievement of sustainable environment and development in Nigeria requires deliberate policies to mitigate the impact of population concentration and wealth creation on the environment. Readers should send their comments on this paper to: BhaskarNath@aol.com within 3 months of publication of this issue.     

A study on the carrying capacity of the available habitat for the Rhinopithecus bieti population at Mt. Laojun in Yunnan, China

Background, aim, and scope  The Yunnan snub-nosed monkey is one of the most endangered primates in the world. It is experiencing a range of ongoing threats and the persisting effects of past disturbances. The prospects for this species are not very optimistic because habitat corridors are severely damaged by logging, grazing, and mining. Each group of the monkeys in different areas is facing a unique variety of threats. Based on genetic analysis, Rhinopithecus bieti should be separated into three management units for conservation, of which the Mt. Laojun management unit involves the most endangered primates. Despite the fact that the vegetation on Mt. Laojun is in a relatively pristine state, only two groups of monkeys, of a total of fewer than 300, survive in the area. With this paper, we aimed to address the capacity of the monkeys’ habitat at the study site and the possible reasons for the small populations. Materials and methods  Rapid ecological assessment based on a SPOT 5 image and field survey was used to simulate the vegetation of the whole area based on reference ecological factors of the GIS system. The vegetation map of the site was thus derived from this simulation. Based on the previous studies, the three vegetation types were identified as the suitable habitat of the monkeys. The confusion matrix-based field GPS points were applied to analyze the precision of the habitat map. Based on the map of suitable habitat of the monkeys, the utilization of the habitat and the carrying capacity were analyzed in the GIS. Results  The confusion matrix-based field GPS points were applied to the habitat analysis process, and it was found that the habitat map was 81.3% precise. Then, with the current habitat map, we found that the mixed forest currently used by the monkeys is only a very small fraction (2.65%) of the overall potential habitat of the population, while the dark conifer forest is 4.09%. Discussion  Poaching is the greatest short-term threat to this species, particularly in the southern range where local residents have a strong tradition of hunting. Quite a few individual monkeys are still trapped accidentally due to the high density of traps. These problems are hard to mitigate because it is difficult to enforce laws due to the extremely rugged terrain. Conclusions  The results show that there is a great ecological capacity of the area for the monkey’s survival and a great potential for an expansion of the monkey population at the site. Based on the current population and its geographical range, it can be estimated that the suitable habitat area defined by this study can support more monkeys, about many times the current population. Thus, at least in the Mt. Laojun Area, poaching pressure is the main factor to be responsible for the low density of Yunnan snub-nosed monkeys instead of habitat alteration. Recommendations and perspectives  Based on these results, some suggestions relating to conservation can be made: Focus conservation efforts on the current distribution area of the monkeys and create a 20 km buffer zone; design a long-term plan for the suitable habitat outside the buffer zone to set up a wildlife corridor in the long run; establish an association for the local hunters exploiting, their knowledge on the animals to promote monkey conservation and stop poaching. Also, the map derived from the study helps managers to allocate conservation resources more efficiently and enhances the overall outcomes of conservation measures.     

水源水及底泥中细菌总数及其优势种群初探

经测定广州市西村水厂水源水及底泥中的细菌总数分别为2.3×10~3个/mL和2.7×10~6个/g。底泥中的NH_4-N降解菌总数为1.31×10~6个/g,占底泥中细菌总数的48.5％。从水中分离出优势菌41株,经鉴定分别为芽胞杆菌属(Bacillus)、假单胞杆菌属(Pseudomonas)、气单胞杆菌属(Aeromonas)、亚硝化杆菌属(Nitrosococcus)、硝化杆菌属(Nitrobacter)、黄单胞杆菌属(Xanthomonas)、棒状杆菌属(Corynebactertium)、产碱菌属(Alcaligener)等8个属。用亚硝化培养基从底泥中分离了NH_4-N降解优势菌20株,经鉴定,分别为Bacillus、节杆菌属(Arthrobacter)、Pseudomonas、Xanthomonas、Nitrosococcus和Nitrobacter等6个属。     

云南地震死亡人数定量估算

本文给出了多震区的地区性指数，并通过分析龙陵地震前的预报、警报、强烈有感前震在减轻伤亡中的作用和通海地震伤亡达到最重的实例，提出了人口户外率的概念。