Structure Of Natural Communities Research Articles

The Trace Metal Composition of Marine Phytoplankton

Trace metals are required for numerous processes in phytoplankton and can influence the growth and structure of natural phytoplankton communities. The metal contents of phytoplankton reflect biochemical demands as well as environmental availability and influence the distribution of metals in the ocean. Metal quotas of natural populations can be assessed from analyses of individual cells or bulk particle assemblages or inferred from ratios of dissolved metals and macronutrients in the water column. Here, we review the available data from these approaches for temperate, equatorial, and Antarctic waters in the Pacific and Atlantic Oceans. The data show a generalized metal abundance ranking of Fe≈Zn>Mn≈Ni≈Cu≫Co≈Cd; however, there are notable differences between taxa and regions that inform our understanding of ocean metal biogeochemistry. Differences in the quotas estimated by the various techniques also provide information on metal behavior. Therefore, valuable information is lost when a single metal stoichiometry is assumed for all phytoplankton.

Multiple competitive mechanisms underlie the effects of a strong invader on early‐ to late‐seral tree seedlings

Summary1. Certain non‐native invaders reduce the species diversity and alter the structure of natural communities by displacing native species with differing life histories, successional roles or resource requirements. Few studies have tested the potential for these ‘strong invaders’ to exert multiple mechanisms of control on natives that differ in these traits.2. We assessed the mechanisms by which bohemian knotweed (Polygonum × bohemicum) regulates seedling growth and survival among early‐, mid‐ and late‐seral tree species in a riparian forest ecosystem in western North America. We used general linear mixed models to compare seedling performance (survival, height and diameter growth, biomass allocation and ectomycorrhizal colonization of root systems) over two growing seasons in paired experimental plots from which knotweed was either removed or retained (controls). Seedling performance was assessed relative to the effects of knotweed on light and soil resources and the traits of the native species.3. Results from paired t‐tests suggest that knotweed had a significant effect on light availability (>85% reduction), but small, mostly non‐significant effects on measured soil properties. Knotweed imposed strong controls on growth and survival of all three tree species. The apparent mechanisms of interaction varied in a manner consistent with species’ ecophysiologies. Reduced survival of early‐ and mid‐seral species was correlated with light limitation beneath knotweed (≤ 7% of ambient levels): light transmittance was significantly higher (79%) above surviving seedlings. Knotweed also exerted strong controls on the late‐seral species, reducing survival by 24% and height and diameter growth by 91–122% and 37–55%. These effects were not correlated with reductions in light. Instead, in the presence of knotweed, ectomycorrhizal colonization was significantly reduced (64%) and root/shoot ratio was significantly increased, suggesting a disruption of soil mutualisms.4. Synthesis. We demonstrate that strong invaders can displace co‐occurring native species through multiple mechanisms that are consistent with the functional traits of native species. To our knowledge, this is the first study to relate community‐level impacts of an invader to the combined effects of resource exploitation and interference of below‐ground mutualisms. Where invaders have the ability to displace early‐ to late‐seral dominants, the consequences for community structure and ecosystem functioning can be profound.

Ecological Aspects of Coastal Sediment Management in the Gulf of Mexico

Reed, D.J.; Hijuelos, A.C., and Fearnley, S.M., 2012. Ecological aspects of coastal sediment management in the Gulf of Mexico. In: Khalil, S.M., Parson, L.E., and Waters, J.P. (eds.), Technical Framework for the Gulf Regional Sediment Management Master Plan (GRSMMP), Journal of Coastal Research, Special Issue No. 60, 51–65. Water and sediment resource planning is a vital facet of natural resource management. There have been many ecologically disruptive consequences from conventional resource management plans. In the northern Gulf of Mexico (GOM) nearby communities depend on water and sediment resources both ecologically as well as economically. The value of these resources is determined by habitat structure and ongoing sediment dynamics. This article explores how human activities have changed sediment dynamicsin relation to the ecology of the habitats present in the northern GOM. It further presents ideas to prevent future problems through sediment management plans that account for natural processes. The northern GOM contains several habitats that are affected by sediment/water resource management plans such as the shoreface (beaches and dunes), barrier islands, hardbottom (coral and oyster reefs), bays, marshes, and forested wetlands. Many common techniques for water/sediment resource management have been used in these areas such as dredging, hard structures (jetties, groins, seawalls, andbreakwaters),dams, diversions,levees,and coastaldevelopment. The implications of these different management techniques can lead to extensive changes in coastal habitats. Dredging causes disturbances to both borrow and placement sites and can change natural community structure at both sites. The installation of hard structures can cause severe changes in habitat structure that can lead to losses of species diversity. The impacts of river management structures (dams, levees, and diversions) alter the delivery of sediment needed by coastal habitats for growth and sustainability. Anthropogenic development in coastal regions prevents those areas from maturing naturally. Because of the importance of sediments to the ecology of the northern GOM coast and its vulnerability to natural and anthropogenic disturbances, several recommendations are made for holistic future sediment management plans.

Large-scale changes in community composition: determining land use and climate change signals.

Human land use and climate change are regarded as the main driving forces of present-day and future species extinction. They may potentially lead to a profound reorganisation of the composition and structure of natural communities throughout the world. However, studies that explicitly investigate both forms of impact—land use and climate change—are uncommon. Here, we quantify community change of Dutch breeding bird communities over the past 25 years using time lag analysis. We evaluate the chronological sequence of the community temperature index (CTI) which reflects community response to temperature increase (increasing CTI indicates an increase in relative abundance of more southerly species), and the temporal trend of the community specialisation index (CSI) which reflects community response to land use change (declining CSI indicates an increase of generalist species). We show that the breeding bird fauna underwent distinct directional change accompanied by significant changes both in CTI and CSI which suggests a causal connection between climate and land use change and bird community change. The assemblages of particular breeding habitats neither changed at the same speed and nor were they equally affected by climate versus land use changes. In the rapidly changing farmland community, CTI and CSI both declined slightly. In contrast, CTI increased in the more slowly changing forest and heath communities, while CSI remained stable. Coastal assemblages experienced both an increase in CTI and a decline in CSI. Wetland birds experienced the fastest community change of all breeding habitat assemblages but neither CTI nor CSI showed a significant trend. Overall, our results suggest that the interaction between climate and land use changes differs between habitats, and that comparing trends in CSI and CTI may be useful in tracking the impact of each determinant.

Recreational fish feeding inside Brazilian MPAs: impacts on reef fish community structure

Although the practice of recreational feeding of fish by tourists is widespread within marine protected areas (MPAs), the ecological consequences of this activity have received little attention. This research aimed to investigate the influence of artificial feeding on reef fish communities of two Brazilian MPAs. Visual censuses were performed in areas not visited by tourists, in order to characterize the natural community structure of each reef system. In the Maracajaú reefs, the effect of artificial feeding was assessed below a moored floating dock found in the area. Stationary visual censuses were carried out before, during and after the fish feeding activity. In the Maragogi reefs, areas with presence and absence of tourism visitation were established. Transect methodology was employed in each of these areas. On both MPAs, fish feeding was a formal activity and occurred on a daily basis during the course of this study. Within the MPAs, 88 species belonging to 40 families were recorded. In Maracajaú, fish, shrimps and squids were provided by the tourists on the floating dock, which favoured mobile invertebrate feeders, whereas in Maragogi, animal ration and human food were used, causing aggregations of omnivores. Differences were observed in terms of abundance between before and after feeding in Maracajaú and between the control and impacted areas of Maragogi. The data are consistent with fish feeding leading to attraction of determined species, causing an increase in their abundance, also indicating that both the type of food and the extension of activity area are important factors determining the effects on fish communities.

First record of the non-indigenous portunid crab Charybdis variegata from the western Atlantic coast

Biological invasions are a present and growing environmental problem because non-indigenous organisms may affect the structure and functioning of native communities. In the marine environment there are records of invasive species in almost all phyla, including crustaceans, and the portunid crabs of the genus Charybdis are among the most widespread invasive groups. We report the first record of Charybdis variegata (Fabricius, 1798) from the western Atlantic coast. This species was collected on an intertidal rocky shore near Santos Harbor, Sao Paulo state, Brazil. Of 311 portunid crabs sampled, 309 individuals belonged to the non-indigenous Charybdis hellerii (A. Milne Edwards, 1867), one was a native Cronius ruber (Lamarck, 1818), and one was identified as the non-indigenous Charybdis variegata. This individual was a juvenile female measuring 27.5 mm in carapace width. The taxonomic traits used for species identification, as well as a morphological comparison between C. hellerii and C. variegata are presented. The introduction route and establishment status of this species are also discussed.

An integrated analytical approach for assessing the biological status of the soil microbial community

An integrated multicriteria analytical procedure for rapid, cost-effective characterisation of the biological status of soil bacterial community was developped. Commercially-available, light emission-based bioassays were selected for measuring cell density, activity, and diversity. All but Terminal Restriction Fragment Length Polymorphism (T-RFLP) were designed for multiwell-plate formats and high-throughput screening potential. Adenosine Tri Phosphate (ATP) was measured using a bioluminescence assay. Dehydrogenase activity (DHA) was measured on growing cells. Kinetic measurements of the formation of a coloured formazan derivative was used after nutrient broth addition to estimate initial cell concentrations by reference to Escherichia coli added as internal standard. Compared to conventional ATP and DHA determinations in soils, the procedures described here do not require extraction of ATP or formazan derivative from the soil matrix. Metabolic diversity was characterised using the Biolog™ system. T-RFLP was chosen for assessing bacterial community structure. The bioassays were performed on microbial preparations obtained after either direct dilution of soil suspensions or prior density-gradient separation of microbial cells from the soil matrix. Dilution maintains the original structure of native dominant microbial communities. Density-gradient separation of microbial cells is highly selective, drastically modifying metabolic (CLP Profiles) and species (T-RFLP patterns) diversity, as well as activity parameters.

Benthic communities on hard substrates covered by Limnoperna fortunei Dunker (Bivalvia, Mytilidae) at an estuarine beach (Río de la Plata, Argentina)

The structure and composition of benthic communities on hard substrates covered by the nonindigenous bivalve Limnoperna fortunei Dunker, the golden mussel, were quantified in the middle zone of the Río de la Plata Estuary (Argentina) from April 2001 through March 2002. A total of 26 taxa were recorded. L. fortunei and Nematoda were the central and dominant groups, with a prodigious abundance of over 80%. The prevalence of L. fortunei, rather than the environmental variables, regulated the dynamics of the associated invertebrate fauna. The golden mussel alters both the structure and function of benthic native communities on hard substrates, allows a higher surface available for colonization and refuge, and provides food source to deposit-feeding organisms in the form of organic or residual material. The mussel also increases the abundance and diversity of taxa on hard substrata - such as Oligochaeta, Hirudinea, Tardigrada, Chironomidae, Copepoda, Tanaidacea, and Hydrachnidia. Similarities and nonparametric multidimensional-scaling analyses indicated that the benthic composition had a seasonal variation. L. fortunei has an environmental impact, an ability to invade new freshwater ambiences worldwide and ecological characteristic comparable to those of Dreissena polymorpha Pallas (the zebra mussel) of North America and Europe.

Initial size structure of natural phytoplankton communities determines the response to Daphnia diel vertical migration

Diel vertical migration (DVM) is a common behavior of many pelagic herbivorous zooplankton species in response to predation pressure. It is characterized by a twice daily habitat shift of the zooplankton species: staying in the epilimnion only during night time and migrating down in the crack of dawn in deeper water layers, staying there during the day time. This causes a discontinuous grazing regime and previous studies have shown that the direction and strength of phytoplankton community responses to zooplankton DVM most probably depends on the size of phytoplankton species. To examine the influence of zooplankton DVM on different sized phytoplankton communities, we designed an experiment where we manipulated the size distribution of a natural phytoplankton community a priori in field mesocosms. We investigated the influence of DVM of the cladoceran Daphnia hyalina on two different phytoplankton communities, by the use of deep (10 m) field enclosures. Epilimnetic lake water, containing a summer phytoplankton community, was filtered with two different mesh sizes (11 mm and 64 mm). The 11 mm phytoplankton community (“small”) contained mainly small algal species, while the 64 mm community (“large”) had a wider range of phytoplankton sizes. To simulate zooplankton DVM, D. hyalina were placed in mesh cages that were lowered or raised (“migration”) as dictated by the study design; a “no migration” (representing absence of DVM) treatment was also tested. Phytoplankton abundance was measured using chlorophyll-a and biovolume; size distribution of the algae and nutrient availability was also determined in each treatment. The results indicated that DVM had contrasting effects on the two evaluated phytoplankton communities. Comparison of “migration” and “no migration” zooplankton treatments showed that nutrient availability and total phytoplankton biovolume was higher in (1) “no migration” treatments with phytoplankton communities comprising mainly small algae and (2) “migration” treatments with phytoplankton communities of a broader size spectrum of algae. Hence our study showed two different mechanisms of how zooplankton DVM may influence the phytoplankton community dynamics. Nutrient cycling was an important factor in phytoplankton communities of mainly small algae, whereas the refuge effect was the main driver of phytoplankton dynamics in phytoplankton communities of a large size spectrum of algae.

Lantana camara invasion in a heterogeneous landscape: patterns of spread and correlation with changes in native vegetation

The effects of invasive species on community structure remain under-investigated due to the lack of long-term data. Our objectives were to examine the correlation between Lantana camara L. invasion and native species abundance, distribution, diversity, and population structure, across different forest types in a heterogeneous landscape. We examined changes in native vegetation and L. camara between 1997 and 2008. We used existing vegetation data from 134 plots spread across the 540 km2 landscape from 1997 and re-censused these plots in 2008. We then examined the change in species richness, Shannon’s diversity, evenness, and population structure of native species from 1997 to 2008. We also examined the relationship between L. camara density and species richness, diversity, evenness, and population structure. The presence and abundance of L. camara increased dramatically from 1997 to 2008. L. camara occurred in 81% of plots by 2008, compared with only 41% of plots in 1997. Similarly, the mean density of L. camara increased almost fourfold from 1997 to 2008. This was accompanied by a change in native community structure. Species richness, diversity and evenness declined significantly in some forest types, and at the landscape scale. There were also changes in the population structure of native tree species, with reductions in the density of tree saplings, possibly due to competition with L. camara. We demonstrate the pervasive threat posed by L. camara to native vegetation at the scale of individual forest types, and at the larger landscape scale, in our study area. These changes have long-term consequences for forest structure and composition.

Bacteriophages with Potential for Inactivation of Fish Pathogenic Bacteria: Survival, Host Specificity and Effect on Bacterial Community Structure

Phage therapy may represent a viable alternative to antibiotics to inactivate fish pathogenic bacteria. Its use, however, requires the awareness of novel kinetics phenomena not applied to conventional drug treatments. The main objective of this work was to isolate bacteriophages with potential to inactivate fish pathogenic bacteria, without major effects on the structure of natural bacterial communities of aquaculture waters. The survival was determined in marine water, through quantification by the soft agar overlay technique. The host specificity was evaluated by cross infection. The ecological impact of phage addition on the structure of the bacterial community was evaluated by DGGE of PCR amplified 16S rRNA gene fragments. The survival period varied between 12 and 91 days, with a higher viability for Aeromonas salmonicida phages. The phages of Vibrio parahaemolyticus and of A. salmonicida infected bacteria of different families with a high efficacy of plating. The specific phages of pathogenic bacteria had no detectable impact on the structure of the bacterial community. In conclusion, V. parahaemolyticus and A. salmonicida phages show good survival time in marine water, have only a moderated impact on the overall bacterial community structure and the desired specificity for host pathogenic bacteria, being potential candidates for therapy of fish infectious diseases in marine aquaculture systems.

Natural and anthropogenic factors shape metazoan parasite community structure in mummichog (Fundulus heteroclitus) from two estuaries in New Brunswick, Canada

Previously published multidisciplinary studies in the Miramichi and Bouctouche rivers (New Brunswick, Canada) noted significant changes in fish health parameters, including elevated tissue levels of organic contaminants and a wide range of physiological disturbances, in mummichog Fundulus heteroclitus (L.) from a site on the Miramichi River that received bleached kraft pulpmill and municipal effluent. The present study reports differences in the abundance of individual parasite species, as well as parasite infracommunity and component community composition, in mummichog from both rivers. These differences were evaluated in relation to host (size, condition, immune function, tissue organochlorine contaminant levels) and environmental (faecal coliform counts, salinity, temperature) data derived from the previously published studies. Overall, 18 parasite species were identified, the most common of which were Ascocotyle sp. larv., Ornithodiplostomum sp. larv., Posthodiplostomum sp. larv., and Proteocephalus filicollis (Rudolphi, 1802). There were broad differences in parasite community structure and composition between rivers and within rivers, the most prominent pattern being a pronounced difference between sites in the upper and lower estuary of each river that was likely driven by salinity. Mean infracommunity richness was also positively related to faecal coliforms (considered here as a surrogate measure of eutrophication via municipal sewage), and both were highest at the most polluted site. We noted no other significant relationships. Thus our data suggest that the parasite communities in these two estuaries were primarily structured by large upstream/downstream ecological gradients in salinity, and secondarily by eutrophication due to pollution by municipal and industrial effluents. Overall, our results highlight the value of coordinated multidisciplinary studies for understanding the factors that shape parasite abundance and community structure.

Role of essential lipids in determining food quality for the invasive freshwater clam Corbicula fluminea

The invasive clam Corbicula fluminea has become a widespread benthic invertebrate in many freshwater ecosystems throughout Europe and North and South America. Invasive bivalves can dramatically alter the structure of native benthic communities, so understanding the factors responsible for successful invasion is important. We investigated C. fluminea nutritional requirements for essential lipids in a standardized growth experiment. Juvenile clams were fed different cyanobacteria (Aphanizomenon flos-aquae, Anabaena variabilis, Synechococcus elongatus) or eukaryotic algae (Scenedesmus obliquus, Cryptomonas sp.). Somatic growth rates were then correlated with elemental (C∶N and C∶P) and biochemical (sterol and fatty acid content) components of the food sources and clam tissue. Somatic growth rates were significantly higher when juveniles were fed eukaryotic algae than when fed cyanobacteria. Linear regression analyses revealed significant positive relationships between somatic growth rates and dietary sterol and polyunsaturated fatty acid content. Somatic growth rates also were highly correlated with the total sterol and α-linolenic acid content of clam tissues. This result suggests that the growth of C. fluminea is partially dependent on the availability of these essential lipids in the diet. Algal nutritional value may influence the successful geographic spread of this highly invasive species because food quality and quantity are changing as a result of global warming.

Effects of gypsy moth establishment and dominance in native caterpillar communities of northern oak forests

AbstractLittle research has addressed the impacts of invasive-species establishment on native forest insect communities. Such information is lacking even for gypsy moth,Lymantria dispar(L.) (Lepidoptera: Erebidae), the most thoroughly studied invasive forest insect. We investigated the ecological impacts of gypsy moth on native species at sites in north-central Ontario, Canada, with and without significant histories of gypsy moth defoliation over a 2-year period. Patterns in native forest caterpillar communities are described using measures of species diversity and multivariate analysis. We documented a transition from low-level to dominant gypsy moth populations. Sites with different gypsy moth outbreak histories exhibited differences in rank-abundance distributions and dominance structures in the first year of the study; by the second year, gypsy moth was dominant at sites of both types irrespective of their previous defoliation history. Contrary to our predictions, we found that gypsy moth outbreak history had no significant effects on native caterpillar community diversity or structure. However, sites with currently high gypsy moth abundance demonstrated significant shifts in late-season caterpillar community structure. Our results suggest that observed community differences were due to the presence of a highly abundant folivore, and not to permanent shifts in the native community because of the introduction of an invasive species.

Invasive mussels induce community changes by increasing habitat complexity

Habitat complexity is among the most important factors affecting the diversity, structure, and density of natural communities. The invasive byssate bivalves zebra mussel (Dreissena polymorpha (Pallas, 1771)) and golden mussel (Limnoperna fortunei (Dunker, 1857)) are sessile suspension feeders that form aggregations (druses), physically changing sediments and increasing habitat complexity, and providing shelter and food for other benthic organisms. In this study, we explored the impact of the change in habitat complexity on benthic community created by druses of L. fortunei and D. polymorpha, formed on various sediments. D. polymorpha was studied in Europe (Naroch Lake, Belarus) and in North America (Glen Lake and Lower Nashotah Lake, USA), and L. fortunei was studied in South America (Rio Tercero Reservoir, Argentina). Druses of D. polymorpha or L. fortunei and samples of bare nearby sediment (without druses of exotic mussels) were collected at each sampling site. We found significant changes in species richness, density, biomass, taxonomic, and trophic structure of communities formed in druses compared to the nearby bare sediments. Community taxonomic richness increased threefold, and density increased sevenfold with increasing complexity of habitat from sand to druse. The feeding functional group approach indicated that the impact of increased complexity was reinforced by an increase in food supply in D. polymorpha and L. fortunei druses. Along with increasing species richness and densities, byssate bivalves homogenized benthic communities.

AS Alliance based security enhancement for inter-domain routing protocol

The Internet routing system as a complex system is faced with many challenges. Attacks against Border Gateway Protocol (BGP), the only wide-area routing protocol between different Autonomous Systems (AS), are increasing in number and severity. Most security mechanisms based on public key cryptography are far from deployment due to performance, trust model and other issues. Self-organization is a promising mechanism to control the complexity in large scale and dynamic networks. This paper proposes the notion of AS Alliance, a natural community structure self-organized based on commercial, political or other social relationships and taking advantage of the power-law and rich-club features of AS-level topology. A new trust model, Trust Translator Model (TTM), is designed based on AS Alliance to improve the security of BGP. TTM avoids the global distribution of certificates by trust translating of hub nodes between different trust domains, and yields much less memory overhead and a shorter validation chain than the traditional solutions. We develop a novel SE-BGP (Security Enhanced BGP) protocol extension exploiting TTM model. It introduces new path attributes to carry origin certificates and path signatures, and the algorithms to process origin authentication and path authentication. Our analysis and experiment results show that SE-BGP is a viable solution.

Testing multiple assembly rule models in avian communities on islands of an inundated lake, Zhejiang Province, China

Aim A fundamental question in community ecology is whether general assembly rules determine the structure of natural communities. Although many types of assembly rules have been described, including Diamond';s assembly rules, constant body-size ratios, favoured states, and nestedness, few studies have tested multiple assembly rule models simultaneously. Therefore, little is known about the relative importance of potential underlying factors such as interspecific competition, inter-guild competition, selective extinction and habitat nestedness in structuring community composition. Here, we test the above four assembly rule models and examine the causal basis for the observed patterns using bird data collected on islands of an inundated lake. Location Thousand Island Lake, China. Methods We collected data on presence-absence matrices, body size and functional groups for bird assemblages on 42 islands from 2007 to 2009. To test the above four assembly rule models, we used null model analyses to compare observed species co-occurrence patterns, body-size distributions and functional group distributions with randomly generated assemblages. To ensure that the results were not biased by the inclusion of species with extremely different ecologies, we conducted separate analyses for the entire assemblage and for various subset matrices classified according to foraging guilds. Results The bird assemblages did not support predictions by several competitively structured assembly rule models, including Diamond';s assembly rules, constant body-size ratios, and favoured states. In contrast, bird assemblages were highly significantly nested and were apparently shaped by extinction processes mediated through area effects and habitat nestedness. The nestedness of bird assemblages was not a result of passive sampling or selective colonization. These results were very consistent, regardless of whether the entire assemblage or the subset matrices were analysed. Main conclusions Our results suggest that bird assemblages were shaped by extinction processes mediated through area effects and habitat nestedness, rather than by interspecific or inter-guild competition. From a conservation point of view, our results indicate that we should protect both the largest islands with the most species-rich communities and habitat-rich islands in order to maximize the number of species preserved.

Metacommunity assembly and sorting in newly formed lake communities

new habitats are created, community assembly may follow independent trajectories, since the relative importance of dispersal limitation, priority effects, species interactions, and environmental gradients can vary as assembly proceeds. Unfortunately, tracking community colonization and composition across decades is challenging. We compiled a multiyear community composition data set and reconstructed past communities with remains from sediment cores to investigate cladoceran assembly dynamics in six older (1920s) and two more recently formed (1950s) lakes. We found that current communities cluster along a gradient of thermal stratification that is known to influence predation intensity. Assembling communities showed evidence for a greater influence of species sorting and a reduced influence of spatial structure since the first colonizations. However, lake community trajectories varied considerably, reflecting different colonization sequences among lakes. In the older lakes, small-bodied cladocerans often arrived much earlier than large-bodied cladocerans, while the two younger lakes were colonized much more rapidly, and one was quickly dominated by a large-bodied species. Thus, by combining contemporary community data with paleoecological records, we show that assembly history influences natural community structure for decades while patterns of ecological sorting develop.

Changes within Small Mammal Communities since the 1988 Huckleberry Mountain Fire

This study is a continuation of investigations conducted at Huckleberry Mountain to determine the effect of the 1988 Greater Yellowstone fire on the small mammal community, and document changes in this community over the 22 years since this natural disturbance. Previous research was conducted in 1993, 1994, 1997, and 1998 and we sampled the same communities in 2009 and again in 2010 using the identical sampling methodology. During the summer of 2010 we live trapped 252 Southern Red-backed Vole (Myodes gapperi), 57 North American Deermouse (Peromyscus maniculatu), 22 Least Chipmunk (Tamias minimus), 12 Western Jumping Mouse (Zapus princeps), four Montane Vole (Microtus montanus), one Northern Pocket Gopher (Thomomys talpoides), four Cinereus Shrew (Sorex cinereus), and five Dusky Shrew (S. monticolus). These results are similar to our results from 2009 and corroborate findings from other investigations indicating early dominance of P. maniculatus in burned forests and M. gapperi in control unburned areas. M. gapperi and P. maniculatus accounted for the majority (87%) of captures. In addition more M. gapperi were found in control sites than P. maniculatus, and as the burned habitat recovers over time, the relative numbers of P. maniculatus are decreasing, and the number of M. gapperi are increasing, suggesting that the burned habitats are returning to a more natural pre-disturbance community structure. However, community diversity indices (which include all mammal species and their relative proportions) suggest that there are still considerable differences between burned and unburned sites. Despite the numbers of voles and deermice changing over time (as predicted), the burned and control small mammal communities are still quite different from one another even after 22 years.

Multitrophic interactions below and above ground: en route to the next level

Summary 1. Plants mediate multiple interactions between below‐ground (BG) and above‐ground (AG) heterotrophic communities that have no direct physical contact. These interactions can be positive or negative from the perspective of each player, can go from the BG to the AG community or vice versa, and comprise representatives of different phyla. Here we highlight emerging general patterns and discuss future research directions. 2. Ecologists initially postulated that root herbivores induce general stress responses, which increase the levels of primary (nutritional) compounds in the undamaged plant compartment and thereby facilitate future attack by AG herbivores. However, damage can also reduce the levels of primary compounds or increase contents of secondary (defensive) metabolites. Both effects may cause resistance phenotypes that play an important role in mediating BG–AG interactions. Systemically induced resistance does not only affect other herbivores but also pathogens in the AG and BG compartment and may inhibit beneficial organisms such as natural enemies of herbivores, microbial root symbionts and pollinators. Conversely, symbiotic mutualists such as mycorrhiza and rhizobia may affect AG and BG defence levels. Finally, BG–AG interactions may be costly if they impede optimal defence strategies in the undamaged compartment. 3. Synthesis. In order to better understand the adaptive value of BG–AG induced responses for the players involved and to identify the driving evolutionary forces, we need a better integration of studies at the community level with experiments on model systems that allow unravelling the genetic and physiological mechanisms of BG–AG interactions. Experiments preferably should be carried out at realistic densities and using the natural temporal sequence at which the various associations are established, because we can expect plants to be adapted only to events that are common over evolutionary time spans. Detailed mechanistic knowledge will help to reproduce relevant interactions in experiments that study multiple species in the field. This step will ultimately allow us to evaluate the importance of plant‐mediated interactions between BG and AG communities for the fitness of the species involved and for the structuring of natural communities.