Niche Resource Partitioning Research Articles

Limitation by a shared mutualist promotes coexistence of multiple competing partners

Although mutualisms are often studied as simple pairwise interactions, they typically involve complex networks of interacting species. How multiple mutualistic partners that provide the same service and compete for resources are maintained in mutualistic networks is an open question. We use a model bacterial community in which multiple ‘partner strains’ of Escherichia coli compete for a carbon source and exchange resources with a ‘shared mutualist’ strain of Salmonella enterica. In laboratory experiments, competing E. coli strains readily coexist in the presence of S. enterica, despite differences in their competitive abilities. We use ecological modeling to demonstrate that a shared mutualist can create temporary resource niche partitioning by limiting growth rates, even if yield is set by a resource external to a mutualism. This mechanism can extend to maintain multiple competing partner species. Our results improve our understanding of complex mutualistic communities and aid efforts to design stable microbial communities.

Small differences in root distributions allow resource niche partitioning.

Deep roots have long been thought to allow trees to coexist with shallow‐rooted grasses. However, data demonstrating how root distributions affect water uptake and niche partitioning are uncommon.We describe tree and grass root distributions using a depth‐specific tracer experiment six times over two years in a subtropical savanna, Kruger National Park, South Africa. These point‐in‐time measurements were then used in a soil water flow model to simulate continuous water uptake by depth and plant growth form (trees and grasses) across two growing seasons. This allowed estimates of the total amount of water a root distribution could absorb as well as the amount of water a root distribution could absorb in excess of the other rooting distribution (i.e., unique hydrological niche).Most active tree and grass roots were in shallow soils: The mean depth of water uptake was 22 cm for trees and 17 cm for grasses. Slightly deeper rooting distributions provided trees with 5% more soil water than the grasses in a drier season, but 13% less water in a wetter season. Small differences also provided each rooting distribution (tree or grass) with unique hydrological niches of 4 to 13 mm water.The effect of rooting distributions has long been inferred. By quantifying the depth and timing of water uptake, we demonstrated how even small differences in rooting distributions can provide plants with resource niches that can contribute to species coexistence. Differences in total water uptake and unique hydrological niche sizes were small in this system, but they indicated that tradeoffs in rooting strategies can be expected to contribute to tree and grass coexistence because 1) competitive advantages change over time and 2) plant growth forms always have access to a soil resource pool that is not available to the other plant growth form.

Spatiotemporal niche partitioning in a specious silphid community (Coleoptera: Silphidae Nicrophorus).

Resource niche partitioning mediates the coexistence of similar species by reducing the chance of competitive encounters. For co-occurring species that share an ephemeral resource, contrasting activity in space and time may facilitate their persistence. Burying beetles (Silphidae: Nicrophorus) depend entirely on small vertebrate carcasses to reproduce. Given the unpredictability of this resource, and its value to congeners and other scavenger species, burying beetles likely endure intense competition to secure a carcass. Here, contrasting spatial and temporal niche patterns are explored as resource allocation strategies among five sympatric species of burying beetles (N. americanus, N. marginatus, N. pustulatus, N. orbicollis, and N. tomentosus). Specifically, the space-use and daily activity patterns are measured, at a fine scale, across species pairs to extrapolate contrasting niche-use patterns within a nicrophorine-rich grassland community in North-Central Oklahoma, USA. The results of this study reveal an important interplay between space-use and daily temporal activity in mediating the scramble competition associated with carrion resources. Where spatial or temporal overlap between burying beetle species is high, direct competition is mediated along an alternative niche dimension. For instance, N. americanus and N. orbicollis, a species dyad thought to be in direct competition, do overlap temporally but were found to have segregated space-use patterns. Our findings provide key insights into the competitive interactions within a necrophilous community and further inform our broader understanding of the spatial and temporal resource dimensions that drive the ecological niche.

Oribatid mites reveal that competition for resources and trophic structure combine to regulate the assembly of diverse soil animal communities.

The role of niche partitioning in structuring species‐rich soil animal communities has been debated for decades and generated the “enigma of soil animal diversity.” More recently, resource‐based niche partitioning has been hypothesized to play a very limited role in the assembly of soil animal communities. To test this hypothesis, we applied a novel combination of stable isotopes and null models of species co‐occurrence to quantify the extent of resource niche partitioning on a diverse oribatid mite community sampled from mature oak woodland.We asked whether species aggregate or segregate spatially and how these patterns correlated with the abundance of estimated trophic guilds. We also estimated the effects of environmental variables on community structure.All measured environmental variables accounted for 12% of variance in community structure, including 8% of pure spatial structure unrelated to measured environmental factors and 2% of pure environmental variance unrelated to spatial variation. Co‐occurrence analysis revealed 10 pairs of species that aggregated and six pairs of species that were spatially segregated. Values of δ15N indicated that five out of the 10 pairs of aggregated species occupied the same trophic guild, while values of δ13C indicated that species in these five pairs consumed resources of different quality, supporting a significant role of resource‐based niche partitioning. Also, one of the five pairs of segregated species occupied the same trophic guild but had overlapping δ13C values suggesting that these species do not co‐occur locally and thus minimize competition for shared resources.Partitioning of resources plays an underestimated role in soil microarthropod communities and different local communities consisted of the same trophic guilds with species identity changing from place to place. The sum of resource partitioning, multi‐trophic interactions, and microscale environmental variability in the environment is a viable solution to the enigma of soil animal diversity.

Niche partitioning on Sumatran Elephant (Elephas maximus sumatranus) and human in space and resources in Riau, Indonesia

Abstract. Sukmantoro YW, Alikodra HS, Kartono AP, Efransjah. 2019. Niche partitioning on Sumatran Elephant (Elephas maximus sumatranus) and human in space and resources in Riau, Indonesia. Biodiversitas 20: 1362-1373. Research on elephant and human niches at Balai Raja and Tesso Nilo have been done for 6 years (2012-2017). The study was conducted by recording the distribution of elephants and communities. The distribution of elephants was identified through an installed GPS Collar in 3 groups of elephants (Butet, Angelina and Desma) since 2012. In 2016, data collection of resources was done through OLI 8+ Landsat imagery and records from the field. From the results of the study, elephants (Desma, Angelina and Butet groups) and humans have significantly different niches in space, but in terms of resources, all three elephant groups are almost the same to use them. In the context of niche partitioning of resources, Desma group used more thenatural forest, swamp and wasteland areas than the communities. InTesso Nilo, elephants groups used more open land than the communities.The overlapping between elephant and human creates human-elephant conflicts. For this reason, strengthening the niche partitioning strategy in space and resources can be a solution to conflict reduction. In addition, if elephants with humans are forced to live in the same space and resources, they develop strategies of neutralism or coexistence. For the community, converting plant commodities in the direction of an elephant's dislike (still of economic value) can reduce losses for the community and create a non-disturbing relationship between elephant and human. Examples of what the community has done are cassava cultivation and timber industry concession strategy in planting Acacia which is relatively not detrimental to the company even though the plant is damaged by an elephant.

Variation of the biotic neighbourhood and topographic effects on tree survival in an old‐growth temperate forest

AbstractAimsTree mortality can determine forest dynamics and succession, alter nutrient cycling and contribute to tree species co‐existence. Understanding the mechanisms that maintain species diversity is a central goal of community ecology. In this study, we incorporated survival data from a 10‐yr interval census to determine whether there is significant interspecies variation in the effects of biotic neighbourhood variables and whether there is significant spatial variation in the effects of topographic variables on tree survival in a broadleaved‐Korean pine temperate forest.LocationTemperate forest, northeast China.MethodsWe used GLMM and geographically weighted GLM as well as their corresponding test approaches to determine whether there is significant interspecies variation in the effects of biotic neighbourhood variables over variable neighbourhood radii and whether there is significant spatial variation in the effects of topographic variables on tree survival across multiple spatial scales in an old‐growth temperate forest dynamics plot in northeast China.ResultsOur results showed that the effects of neighbourhood variables on tree survival varied among species and effects of topography varied over space. However, the results depended on the neighbourhood radius and spatial scale. The neighbourhood radius affected detection of variation in neighbourhood effects among species, and the spatial scale similarly affected detection of spatial variation in the effects of topography. The effect of conspecific neighbour density on survival varied more widely among species than that of the average phylogenetic dissimilarity of heterospecific neighbours, regardless of the neighbourhood radius. Moreover, the effect of elevation varied more widely over space than those of convexity and hill shade at any quadrat scale.ConclusionsOur findings highlight that future studies should account for variations in the neighbourhood radius among species and/or circumstances as well as the spatial scale when assessing factors that contribute to species co‐existence in long‐lived organisms. Species leaf phenology, shade and drought tolerance and environmental filtering may explain these variations in the effects of neighbourhood and topographic variables on tree survival. Overall, our results indicate that both density dependence and resource niche partitioning are important mechanisms for maintaining biodiversity in this broad‐leaved Korean pine temperate forest.

Ecomorphological diversification in reef fish of the genus Abudefduf (Percifomes, Pomacentridae)

Coral reefs are home to the most diverse fish assemblages on earth. This high diversity has been hypothesized to partially result from fine-scale niche partitioning of resources. Because niche partitioning might be facilitated by phenotypic diversity, analysis of the morphological variation in an evolutionary context can contribute to our understanding of the speciation and diversification of reef fish. Damselfishes (Pomacentridae) are an extremely diverse group of reef fishes, and Abudefduf genus is one of the youngest clades of this family. Abudefduf is basal clade group benthic feeders, feeding on algae, small benthic invertebrates and zooplankton. In contrast, more derived clades feed primarily on zooplankton. In this study, we examine the relation between morphological and ecological variation to determine the main forces driving diversification in Abudefduf. Results support clear ecomorphological segregation among basal and derived clades, indicating evolution from benthic feeders to zooplanktivorous feeders, suggesting that the shift to a new trophic niche was an important event driving diversification in Abudefduf, and also evidenced by the presence of morphological traits that represent specialized adaptations to chase plankton in the water column. Our analysis demonstrates the utility of morphological and ecological studies to understand the diversification process of reef fish.

Metatranscriptome analyses indicate resource partitioning between diatoms in the field

Diverse communities of marine phytoplankton carry out half of global primary production. The vast diversity of the phytoplankton has long perplexed ecologists because these organisms coexist in an isotropic environment while competing for the same basic resources (e.g., inorganic nutrients). Differential niche partitioning of resources is one hypothesis to explain this "paradox of the plankton," but it is difficult to quantify and track variation in phytoplankton metabolism in situ. Here, we use quantitative metatranscriptome analyses to examine pathways of nitrogen (N) and phosphorus (P) metabolism in diatoms that cooccur regularly in an estuary on the east coast of the United States (Narragansett Bay). Expression of known N and P metabolic pathways varied between diatoms, indicating apparent differences in resource utilization capacity that may prevent direct competition. Nutrient amendment incubations skewed N/P ratios, elucidating nutrient-responsive patterns of expression and facilitating a quantitative comparison between diatoms. The resource-responsive (RR) gene sets deviated in composition from the metabolic profile of the organism, being enriched in genes associated with N and P metabolism. Expression of the RR gene set varied over time and differed significantly between diatoms, resulting in opposite transcriptional responses to the same environment. Apparent differences in metabolic capacity and the expression of that capacity in the environment suggest that diatom-specific resource partitioning was occurring in Narragansett Bay. This high-resolution approach highlights the molecular underpinnings of diatom resource utilization and how cooccurring diatoms adjust their cellular physiology to partition their niche space.

Quantifying resource use complementarity in grassland species: A comparison of different nutrient tracers

Abstract Stable isotopes (e.g. 15 N) and rare elements (e.g. Li + , Rb + , Sr 2+ ) have been applied to trace nutrient uptake in plants. Tracer methods are increasingly used to quantify soil resource niche partitioning in multi-species communities. Niche partitioning allows for complementarity in nutrient uptake. Spatial complementarity is most frequently measured on separate plots, which bears a risk of between plot variations. This could be avoided with a method that allows for quantification of nutrient partitioning within the same plot. However, there is uncertainty whether uptake is sufficiently similar among different tracers to allow for direct comparison. Therefore we tested uptake similarity between Li + and Rb + to determine if they can serve as analogues to quantify nutrient uptake from different soil depths. We found a strong overall correlation between Li + and Rb + accumulation, irrespective of the duration of tracer exposition and plant species identity. However, the slope of the regression between both elements was different in roots and shoots and between different functional groups, pointing to the need of correction factors. Comparisons with other tracers showed that Li + and Rb + accumulation is clearly more similar to each other than to Sr 2+ and 15 N accumulation. We therefore conclude: Li + and Rb + have a strong potential to be used as tracers for quantifying spatial complementarity within one given plot under field conditions.

Niche Divergence Among Sex and Age Classes in Black-and-White Snub-nosed Monkeys (Rhinopithecus bieti)

A wide range of dimorphic species exhibit intraspecific differences in feeding ecology and habitat use; however, studies comparing resource partitioning between males and females and between age groups occur mainly at the community and species level. We here classified the main habitat of black-and-white snub-nosed monkeys (Rhinopithecus bieti) –fir tree crown– into six microhabitats; examined the lichen-load of the microhabitats; and investigated the microhabitat use of age–sex groups within one-male units (OMUs: an adult male, several females, and juveniles) of R. bieti using instantaneous scanning sampling methods to test whether there is resource niche partitioning in social units of this sexually dimorphic primate in a reserve in Yunnan, China. Our results showed that adult females and juveniles often foraged in the outer layer of the fir tree crown, whereas adult males often foraged in the inner layer, closer to the trunk where food abundance was highest. Adult females and juveniles, however, both shifted microhabitat-use patterns to the inner layer of the fir tree crown when the adult male was absent from the tree. We suggested that the preference for and benefit of the central layer of fir tree crown lies in food availability, but that adult male competitively excluded group members. Microhabitat segregation may serve to maximize the fitness of the group members by reducing intragroup competition, while also increasing interindividual distance, thereby reducing the possible effects of scramble competition.

Root niche partitioning among grasses, saplings, and trees measured using a tracer technique

Niche partitioning of resources by plants is believed to be a fundamental aspect of plant coexistence and biogeochemical cycles; however, measurements of the timing and location of resource use are often lacking because of the difficulties of belowground research. To measure niche partitioning of soil water by grasses, planted saplings, and trees in a mesic savanna (Kruger National Park, South Africa), we injected deuterium oxide into 102,000 points in 15, 154-m(2) plots randomly assigned to one of five depths (0-120 cm) and one of three time periods during the 2008/2009 growing season. Grasses, saplings and trees all demonstrated an exponential decline in water uptake early in the season when resources were abundant. Later in the season, when resources were scarce, grasses continued to extract the most water from the shallowest soil depths (5 cm), but saplings and trees shifted water uptake to deeper depths (30-60 cm). Saplings, in particular, rapidly established roots to at least 1 m and used these deep roots to a greater extent than grasses or trees. Helping to resolve contradictory observations of the relative importance of deep and shallow roots, our results showed that grasses, saplings and trees all extract the most water from shallow soils when it is available but that woody plants can rapidly shift water uptake to deeper soils when resources are scarce. Results highlight the importance of temporal changes in water uptake and the problems with inferring spatial and temporal partitioning of soil water uptake from root biomass measurements alone.

Diet of demersal sharks and chimaeras inferred by fatty acid profiles and stomach content analysis

Obtaining adequate dietary information for many shark and chimaera species has long been a challenge for ecosystem managers, largely due to logistical difficulties in the collection of large sample sizes required for stomach content analyses. Here, we use multivariate analysis of signature fatty acid (FA) profiles as a complementary method to examine the diet composition of 16 demersal shark and chimaera species, collected off south eastern Australia. Comparative results of FA profiles of potential prey and chondrichthyan species mostly agree with the stomach content data. Multivariate analysis correctly classified chimaeras as prominent low-order and benthic consumers, medium-sized dogfish as predators of mid-trophic fish and squid, catsharks as dominant cephalopod consumers, and larger and deeper dwelling dogfish as feeders of bathypelagic fish, squid and feeding on higher order species (cetaceans and seals). Our results demonstrate that signature FA analysis can be applied in dietary studies of sharks and chimaeras to (1) distinguish interspecific differences in general resource (diet and habitat) use patterns; (2) identify degrees of dietary specialisation; and (3) detect niche partitioning of resources by co-occurring species. The FA profiling approach is particularly valuable where sample numbers are likely to be low, such as for these deep-sea and threatened organisms.

Effect of slug grazing on biomass production of a plant community during a short-term biodiversity experiment

While recent theoretical work has demonstrated several mechanisms whereby more diverse communities can exhibit greater resistance against herbivore pressure, empirical examinations have been few and the subject of much debate. The aim of this microcosm experiment was to determine how selectivity of grazing by herbivores affected relationships between plant species number and productivity within artificially created grassland communities. The influence of the slug, Arion lusitanicus, was assessed at four levels of plant species diversity (one, two, four and six species per aquarium). The proportion of biomass of particular species eaten by a slug was estimated on the basis of comparison of paired plots. The biomass in control (ungrazed) plots was compared with the biomass in grazed plots. A significant interaction between the number of plant species and slug grazing for aboveground biomass was found, indicating a gradual decrease in the effect of grazing pressure with increased species richness. Positive average values of the complementarity effect and overyielding index, and negative values of the selection effect, indicated niche resource partitioning between species in grazed plots. The electivity index of food selectivity suggested that food selectivity was more pronounced under higher plant species diversity.