Parasites and Dung Beetles as Ecosystem Engineers in a Forest Ecosystem

Dung beetles serve as the intermediate host for Streptopharagus pigmentatus, a nematode parasite that infects an old world primate, the Japanese Macaque (Macaca fuscata). This study compares the behaviors of infected and uninfected beetles in both transmission dynamics and the ecological role of the parasite. The results suggest that parasitism does not alter the beetle’s use of shelter or choice of substrate on Yakushima Island, Japan. However, infected beetles consume significantly less feces. Dung beetles remove the majority of fecal material in this forest ecosystem, eliminating breeding grounds for many insect pests and burying nutrients that are essential for plant health. Thus, the nematode parasite S. pigmentatus, by altering its host’s behavior, changes the availability of fecal resources to both plant and animal communities and should therefore be classified as an ecosystem engineer.     

Large-Scale Spatial Distribution Patterns of Gastropod Assemblages in Rocky Shores

Gastropod assemblages from nearshore rocky habitats were studied over large spatial scales to (1) describe broad-scale patterns in assemblage composition, including patterns by feeding modes, (2) identify latitudinal pattern of biodiversity, i.e., richness and abundance of gastropods and/or regional hotspots, and (3) identify potential environmental and anthropogenic drivers of these assemblages. Gastropods were sampled from 45 sites distributed within 12 Large Marine Ecosystem regions (LME) following the NaGISA (Natural Geography in Shore Areas) standard protocol (www.nagisa.coml.org). A total of 393 gastropod taxa from 87 families were collected. Eight of these families (9.2%) appeared in four or more different LMEs. Among these, the Littorinidae was the most widely distributed (8 LMEs) followed by the Trochidae and the Columbellidae (6 LMEs). In all regions, assemblages were dominated by few species, the most diverse and abundant of which were herbivores. No latitudinal gradients were evident in relation to species richness or densities among sampling sites. Highest diversity was found in the Mediterranean and in the Gulf of Alaska, while highest densities were found at different latitudes and represented by few species within one genus (e.g. Afrolittorina in the Agulhas Current, Littorina in the Scotian Shelf, and Lacuna in the Gulf of Alaska). No significant correlation was found between species composition and environmental variables (r≤0.355, p>0.05). Contributing variables to this low correlation included invasive species, inorganic pollution, SST anomalies, and chlorophyll-a anomalies. Despite data limitations in this study which restrict conclusions in a global context, this work represents the first effort to sample gastropod biodiversity on rocky shores using a standardized protocol across a wide scale. Our results will generate more work to build global databases allowing for large-scale diversity comparisons of rocky intertidal assemblages.     

Ecosystem Level Impacts of Invasive Acacia saligna in the South African Fynbos

Recent efforts to clear invasive plants from the fynbos of South Africa forces managers to think about how N₂‐fixing invasives have altered ecosystem processes and the implications of these changes for community development. This study investigated the changes in nitrogen (N) cycling regimes in fynbos with the invasion of Acacia saligna, the effects of clear‐cutting acacia stands on soil microclimate and N cycling, and how altered N resources affected the growth of a weedy grass species. Litterfall, litter quality, soil nutrient pools, and ion exchange resin (IER)‐available soil N were measured in uninvaded fynbos, intact acacia, and cleared acacia stands. In addition, a bioassay experiment was used to ascertain whether the changes in soil nutrient availability associated with acacia would enhance the success of a weedy grass species. Acacia plots had greater amounts of litterfall, which had higher concentrations of N. This led to larger quantities of organic matter, total N, and IER‐available N in the soil. Clearing acacia stands caused changes in soil moisture and temperature, but did not result in differences in IER‐available N. The alteration of N availability by acacias was shown to increase growth rates of the weedy grass Ehrharta calycina, suggesting that secondary invasions by nitrophilous weedy species may occur after clearing N₂‐fixing alien species in the fynbos. It is suggested that managers use controlled burns, the addition of mulch, and the addition of fynbos seed after clearing to lower the levels of available N in the soil and initiate the return of native vegetation.     

125 Changing Environmental Conditions and Changes in the Abundances of Rocky Intertidal Seaweeds on Southern California Shores

In a recent study of the North American biogeography of the red algae genus Hildenbrandia , the presence of group I introns were noted in the nuclear SSU rRNA gene of the marine species H. rubra (Hildenbrandiales). Group I introns in the nuclear encoded rRNAs have been previously reported in the Hildenbrandiales as well as the Bangiales. All reported introns within the red algae have been identified as belonging to the IC1 subclass and occur at two insertion sites in the nuclear small subunit rRNA (516 and 1506). However, an unclassified intron was discovered at position 989 in the nuclear SSU rRNA gene of a collection of H. rubra from British Columbia, Canada. We have determined that the intron is a member of the IE subclass and this is the first report of an IE intron and an intron in position 989 in the red algae. Phylogenetic analyses of the intron sequences reveal a close relationship between this group IE intron and similar ascomycete and basidiomycete fungal IE introns in the nuclear SSU rRNA genes at positions 989 and 1199. In addition, a common unique helix (structural signature) in the P13 domain of the Hildenbrandia intron and those of the fungi at the 989 and 1199 IE positions in the nuclear SSU rRNA gene also indicates a close relationship. Hence, this study provides evidence for a possible lateral transfer of the IE intron in position 989 between fungal and red algal nuclear SSU rRNA genes.     

Non-Linear Interactions between Consumers and Flow Determine the Probability of Plant Community Dominance on Maine Rocky Shores

Although consumers can strongly influence community recovery from disturbance, few studies have explored the effects of consumer identity and density and how they may vary across abiotic gradients. On rocky shores in Maine, recent experiments suggest that recovery of plant- or animal- dominated community states is governed by rates of water movement and consumer pressure. To further elucidate the mechanisms of consumer control, we examined the species-specific and density-dependent effects of rocky shore consumers (crabs and snails) on community recovery under both high (mussel dominated) and low flow (plant dominated) conditions. By partitioning the direct impacts of predators (crabs) and grazers (snails) on community recovery across a flow gradient, we found that grazers, but not predators, are likely the primary agent of consumer control and that their impact is highly non-linear. Manipulating snail densities revealed that herbivorous and bull-dozing snails (Littorina littorea) alone can control recovery of high and low flow communities. After ∼1.5 years of recovery, snail density explained a significant amount of the variation in macroalgal coverage at low flow sites and also mussel recovery at high flow sites. These density-dependent grazer effects were were both non-linear and flow-dependent, with low abundance thresholds needed to suppress plant community recovery, and much higher levels needed to control mussel bed development. Our study suggests that consumer density and identity are key in regulating both plant and animal community recovery and that physical conditions can determine the functional forms of these consumer effects.     

Biogeographic patterns of the East African coastal forest vertebrate fauna

The archipelago-like coastal forest of East Africa is one of the highest priority ecosystems for biodiversity conservation worldwide. Here we investigate patterns of species richness and biogeographic distribution among birds, mammals and reptiles of these forests, using distribution data obtained from recently published reviews and information collated by the WWF Eastern Africa Coastal Forest Ecoregion Programme. Birds and mammals species were divided into forest specialists and generalists, and forest specialist reptiles into ‘coastal’ and ‘forest’ endemics. The species richness of birds and generalist mammals increased with area, and is probably a result of area-dependent extinction. Only in birds, however, species richness increased with decreasing isolation, suggesting possible isolation-dependent colonization. Forest diversity, associated to altitudinal range, is important for specialist birds and mammals, whose species richness increased with wider altitudinal range. The number of relict coastal endemic and forest endemic reptiles was higher in forests with wider altitudinal ranges and on relatively higher altitude, respectively. Such forests have probably provided a suitable (and perhaps stable) environment for these species through time, thus increasing their persistence. Parsimony analysis of distributions (PAD) and cluster analyses showed geographical distance and general ecological similarity among forests as a determinant factor in bird distribution patterns, with compositional similarity decreasing with increasing inter-forest distance. Compositional similarity patterns of mammals among the forests did not show a strong geographical correspondence or a significant correlation with inter-forest distance, and those of reptiles were not resolved, with very low similarity levels among forest faunas. Our results suggest that the relative importance (and causal relationship) of forest attributes affecting the distribution of the East African coastal forest vertebrate fauna varies depending on life history traits such as dispersal ability and forest specialization. The groupings in PAD are partly congruent with some of the previous classifications of areas of endemism for this region, supporting the ‘naturalness’ of these regions.     

Genetic Variability in Markers of HLA-C Expression in Two Diverse South African Populations

An insertion-deletion (indel) polymorphism within the 3′ untranslated region (UTR) of HLA-C has been shown to be involved in the regulation of HLA-C expression. Individuals who carry a deletion at this position exhibit increased HLA-C expression, which associates with lower viral set point in HIV-1 infected individuals. This 263 indel (rs67384697) is reported to be in strong linkage disequilibrium (LD) with a single nucleotide polymorphism (SNP) 35 kilobases upstream of HLA-C (-35T/C; rs9264942) in Caucasian individuals, making this SNP a potential marker for both HLA-C expression and HIV-1 disease progression. We therefore examined genetic variation within the HLA-C 3′ UTR of 265 Black and Caucasian South Africans by direct sequencing and identified haplotypes encompassing the 263 indel and another indel at position 230 in both populations. Concomitant evaluation of variability at the −35 SNP revealed this polymorphism to be an inappropriate marker for the 263 indel in these populations. These findings provide important insights into genetic variability within the regulatory regions of HLA-C that have potential implications for our understanding of the regulation of HLA-C expression and its impact on HIV-1 disease progression.     

The Role of Giant Armadillos (Priodontes maximus) as Physical Ecosystem Engineers

Through their excavations, giant armadillos (Priodontes maximus) alter their physical surroundings and create new habitats, which influence resources for at least 24 other species of vertebrates in the Brazilian Pantanal. The role of this poorly known species as an ecosystem engineer may be of high value to the community of vertebrates.     

Effect of Food Concentration Inside Eelgrass Beds on the Energy Balance of the Invasive Mussel Musculista Senhousia

Samples of Musculista senhousia, 20 mm in length, were gathered from San Diego Bay and fed on three different food concentrations: 0.2, 0.4 and 0.8 mg AFDW L m 1, and their energy balance studied. Food concentration ranges were selected to reflect those observed in the field where the invasive mussel M. senhousia co-occurs with the angiosperm, Zostera marina. The lowest and intermediate concentrations correspond to concentrations described in and over large eelgrass patches, respectively. The upper concentration is equivalent to that occurring during the spring phytoplankton blooms. Ingestion rates varied between 81.6 µg AFDW h m 1 for the mussels fed on the lowest concentration, 191.2 µg AFDW h m 1 when the concentration rose to 0.4 mg AFDW L m 1, and 164.0 µg AFDW h m 1 for the highest concentration. Food concentration had a significant effect on absorption efficiency, which was approximately 70% at the intermediate and upper concentrations, but rose to over 80% at the lowest concentration. The food absorption rate varied with food concentration in a manner similar to that of the ingestion rate, i.e., with a maximum value of 142.34 µg AFDW h m 1 for the mussels fed on the intermediate concentration, this being higher than the values for both the highest concentration (114.72 µg AFDW h m 1) and the lowest (65.89 µg AFDW h m 1). Respiration rates were 54 µg O 2 h m 1 for the mussels fed on the lowest concentration and 74 µg O 2 h m 1 for those fed on the intermediate concentration. These results show a close relationship between respiration and ingestion rates, which can be fitted to the following equation: RR = e (m 0.42 + 0.10 IR) (r = 0.5703, R 2 = 32.53, p <0.01). Scope for growth (SFG) estimations were higher for those mussels fed at the intermediate and upper concentrations (1.95 J h m 1 and 1.50 J h m 1, respectively), between which no significant difference was observed (p > 0.05), whilst SFG for the lowest food concentration was only 0.69 J h m 1. The physiological rate with the greatest effect on growth was the absorption rate. Its relation to SFG is described by the equation SFG = 0.67 + 0.90AR (r = 0.977, R 2 = 95.56%, p <0.01). The discussion of these results is based on the growth rates that have been described for this mussel in its natural environment where habitat structure, such as the canopy provided by the eelgrass, can affect the success of the invasive mussel.     

Effect of Season on the Impact of Ecosystem Engineers in the New River, NC

The importance of biotic interactions in structuring communities can depend on seasonal changes in abiotic context. The crayfish and benthic-feeding fish of the headwaters of the New River have been shown to be ecosystem engineers due to their ability to reduce the amount of sediment accumulation in cobble beds during the summer. However, the temperature-driven seasonal reduction in the activity level of these organisms may reduce their impacts during the colder months. I measured the impact of benthic-feeding fish and crayfish on sediment accrual in the headwaters of the New River during the winter using a field exclosure experiment. I found that during the winter there was no effect of benthic-feeding fish and crayfish on the amount of sediment accumulating in cobble beds in the headwaters of the New River. These findings suggest that seasonal changes in the effect of ecosystem engineers need to be quantified for a complete understanding of the effect of these organisms.     

Oceanographic Conditions Limit the Spread of a Marine Invader along Southern African Shores

Invasive species can affect the function and structure of natural ecological communities, hence understanding and predicting their potential for spreading is a major ecological challenge. Once established in a new region, the spread of invasive species is largely controlled by their dispersal capacity, local environmental conditions and species interactions. The mussel Mytilus galloprovincialis is native to the Mediterranean and is the most successful marine invader in southern Africa. Its distribution there has expanded rapidly and extensively since the 1970s, however, over the last decade its spread has ceased. In this study, we coupled broad scale field surveys, Ecological Niche Modelling (ENM) and Lagrangian Particle Simulations (LPS) to assess the current invaded distribution of M. galloprovincialis in southern Africa and to evaluate what prevents further spread of this species. Results showed that all environmentally suitable habitats in southern Africa have been occupied by the species. This includes rocky shores between Rocky Point in Namibia and East London in South Africa (approx. 2800 km) and these limits coincide with the steep transitions between cool-temperate and subtropical-warmer climates, on both west and southeast African coasts. On the west coast, simulations of drifting larvae almost entirely followed the northward and offshore direction of the Benguela current, creating a clear dispersal barrier by advecting larvae away from the coast. On the southeast coast, nearshore currents give larvae the potential to move eastwards, against the prevalent Agulhas current and beyond the present distributional limit, however environmental conditions prevent the establishment of the species. The transition between the cooler and warmer water regimes is therefore the main factor limiting the northern spread on the southeast coast; however, biotic interactions with native fauna may also play an important role.     

The Use of Extant Non-Indigenous Tortoises as a Restoration Tool to Replace Extinct Ecosystem Engineers

We argue that the introduction of non-native extant tortoises as ecological replacements for extinct giant tortoises is a realistic restoration management scheme, which is easy to implement. We discuss how the recent extinctions of endemic giant Cylindraspis tortoises on the Mascarene Islands have left a legacy of ecosystem dysfunction threatening the remnants of native biota, focusing on the island of Mauritius because this is where most has been inferred about plant–tortoise interactions. There is a pressing need to restore and preserve several Mauritian habitats and plant communities that suffer from ecosystem dysfunction. We discuss ongoing restoration efforts on the Mauritian offshore Round Island, which provide a case study highlighting how tortoise substitutes are being used in an experimental and hypothesis-driven conservation and restoration project. The immediate conservation concern was to prevent the extinction and further degradation of Round Island's threatened flora and fauna. In the long term, the introduction of tortoises to Round Island will lead to valuable management and restoration insights for subsequent larger-scale mainland restoration projects. This case study further highlights the feasibility, versatility and low-risk nature of using tortoises in restoration programs, with particular reference to their introduction to island ecosystems. Overall, the use of extant tortoises as replacements for extinct ones is a good example of how conservation and restoration biology concepts applied at a smaller scale can be microcosms for more grandiose schemes and addresses more immediate conservation priorities than large-scale ecosystem rewilding projects.     

Interactive Effects of Three Ecosystem Engineers on Infiltration in a Semi-Arid Mediterranean Grassland

The redistribution of water in semi-arid environments is critical for the maintenance and survival of vegetation patches. We used a systems approach to examine the interactive effects of three engineers—Stipa tenacissima, biological soil crusts, and the European rabbit (Oryctolagus cuniculus)—on infiltration processes in a model gypseous semi-arid Mediterranean grassland. We measured the early (sorptivity) and later (steady-state infiltration) stages of infiltration at two supply potentials using disk permeameters, which allowed us to determine the relative effects of different engineers and soil micropores on water flow through large macropores. We detected few effects under tension when flow was restricted to matrix pores, but under ponding, sorptivity and steady-state infiltration adjacent to Stipa tussocks were 2–3 times higher than in intact or rabbit-disturbed biological soil crusts. Structural Equation Modeling (SEM) showed that both Stipa and biological soil crust cover exerted substantial and equal positive effects on infiltration under ponding, whereas indirectly, rabbit disturbance negatively affected infiltration by reducing crust cover. Under tension, when macropores were prevented from conducting water, Stipa had a direct negative effect and biological soil crust cover was relatively unimportant. More complex SEM models demonstrated that (1) Stipa primarily influenced biological soil crusts by reducing their richness, (2) rabbits exerted a small negative effect on crust richness, and (3) lichens were negatively, and mosses positively, correlated with a derived “infiltration” axis. Our results highlight the importance of biological soil crusts as key players in the maintenance of infiltration processes in Stipa grasslands, and demonstrate the modulating role played by rabbits through their surface disturbances.     

Intrinsic Variability in Shell and Soft Tissue Growth of the Freshwater Mussel Lampsilis siliquoidea

Freshwater mussels are ecologically and economically important members of many aquatic ecosystems, but are globally among the most imperiled taxa. Propagation techniques for mussels have been developed and used to boost declining and restore extirpated populations. Here we use a cohort of propagated mussels to estimate the intrinsic variability in size and growth rate of Lampsilis siliquoidea (a commonly propagated species). Understanding the magnitude and pattern of variation in data is critical to determining whether effects observed in nature or experimental treatments are likely to be important. The coefficient of variation (CV) of L. siliquoidea soft tissues (6.0%) was less than the CV of linear shell dimensions (25.1–66.9%). Size-weight relationships were best when mussel width (the maximum left-right dimension with both valves appressed) was used as a predictor, but 95% credible intervals on these predictions for soft tissues were ∼145 mg wide (about 50% of the mean soft tissue mass). Mussels in this study were treated identically, raised from a single cohort and yet variation in soft tissue mass at a particular size class (as determined by shell dimensions) was still high. High variability in mussel size is often acknowledged, but seldom discussed in the context of mussel conservation. High variability will influence the survival of stocked juvenile cohorts, may affect the ability to experimentally detect sublethal stressors and may lead to incongruities between the effects that mussels have on structure (via hard shells) and biogeochemical cycles (via soft tissue metabolism). Given their imperiled status and longevity, there is often reluctance to destructively sample unionid mussel soft tissues even in metabolic studies (e.g., studies of nutrient cycling). High intrinsic variability suggests that using shell dimensions (particularly shell length) as a response variable in studies of sublethal stressors or metabolic processes will make confident identifications of smaller effect sizes difficult.     

Variability of Primary Production in an Antarctic Marine Ecosystem as Estimated Using a Multi-scale Sampling Strategy

A major objective of the multidisciplinary Palmer Long TermEcological Research (LTER) program is to obtain a comprehensiveunderstanding of various components of the Antarctic marineecosystem—the assemblage of plants, animals, ocean, seaice, and island components south of the Antarctic Convergence.Phytoplankton production plays a key role in this polar ecosystem,and factors that regulate production include those that controlcell growth (light, temperature, nutrients) and those that controlcell accumulation rate and hence population growth (water columnstability, advection, grazing, and sinking). Several of thesefactors are mediated by the annual advance and retreat of seaice. In this study, we examine the results from nearly a decade(1991–2000) of ecological research in the western AntarcticPeninsula region. We evaluate the spatial and temporal variabilityof phytoplankton biomass (estimated as chlorophyll-a concentration)and primary production (determined in-situ aboard ship as wellas estimated from ocean color satellite data). We also presentthe spatial and temporal variability of sea ice extent (estimatedfrom passive microwave satellite data). While the data recordis relatively short from a long-term perspective, evidence isaccumulating that statistically links the variability in seaice to the variability in primary production. Even though thismarine ecosystem displays extreme interannual variability inboth phytoplankton biomass and primary production, persistentspatial patterns have been observed over the many years of study(e.g., an on to offshore gradient in biomass and a growing seasoncharacterized by episodic phytoplankton blooms). This high interannualvariability at the base of the food chain influences organismsat all trophic levels.     

Patella measurements of South African whites as sex assessors.

This study uses metrical characteristics of the patella to derive population specific equations for sex determination in South Africa. Six measurements were taken from 120 normal and undamaged left patellae in a sample of known race, equally distributed by sex, obtained from the Raymond A Dart collection of human skeletons. These data were subjected to discriminant analysis. Maximum height and maximum breadth were selected in the stepwise analysis with an average accuracy of 83% in correct sex classification. Four functions were derived from the direct analysis with a range of average accuracy between 77% and 85%. While most individual variables showed high misclassification rates and may not be useful on their own, maximum height and maximum breadth have an average accuracy of 85 and 79%, respectively.     

污染对华南植物园水生生态系统的影响

华南植物园水体８０年代前水质较好。进入８０年代后,由于水源受污染、厕所排放和枯枝落叶进入水塘腐解等因素导致水体严重富营养化,水体的透明度为０．４ｍ,ｐＨ值为６．８６,ＤＯ为３．３ｍｇ／Ｌ,ＢＯＤ为１０．０ｍｇ／Ｌ,电导率为１８９．９μｓ／ｃｍ,浮游生物为２５００万个／Ｌ,总Ｐ的质量含量为０．２５ｍｇ／Ｌ,总Ｎ的质量含量为２．０ｍｇ／Ｌ,叶绿素总质量含量为０．３３ｍｇ／Ｌ,水体中高等植物的多样性及其