Spatial Resource Partitioning Research Articles

Divide and conquer: Spatial and temporal resource partitioning structures benthic cyanobacterial mats.

Benthic cyanobacterial mats are increasing in abundance worldwide with the potential to degrade ecosystem structure and function. Understanding mat community dynamics is thus critical for predicting mat growth and proliferation and for mitigating any associated negative effects. Carbon, nitrogen, and sulfur cycling are the predominant forms of nutrient cycling discussed within the literature, while metabolic cooperation and viral interactions are understudied. Although many forms of nutrient cycling in mats have been assessed, the links between niche dynamics, microbial interactions, and nutrient cycling are not well described. Here, we present an updated review on how nutrient cycling and microbial community interactions in mats are structured by resource partitioning via spatial and temporal heterogeneity and succession. We assess community interactions and nutrient cycling at both intramat and metacommunity scales. Additionally, we present ideas and recommendations for research in this area, highlighting top-down control, boundary layers, and metabolic cooperation as important future directions.

Spatial and temporal resource partitioning in a mixed-species colony of avian echolocators.

Resource partitioning may facilitate the coexistence of sympatric species with similar ecological requirements. Here, we study a colony of unusual echolocating birds called swiftlets, which nest underground on an island off the coast of Singapore. The colony comprises two congeneric swiftlet species, black-nest swiftlets (Aerodramus maximus) and edible-nest swiftlets (A.fuciphagus), nesting at high densities and in close proximity. Bioacoustic recordings and monitoring of nesting biology at the site across multiple seasons revealed significant differences in echolocation calls as well as survival rates between the species, with the larger black-nest swiftlet nesting at locations with the highest fledging rates. We also observe an additional off-season breeding peak by the smaller species, the edible-nest swiftlet. Unexpectedly, off-season egg-hatching rates were significantly higher compared with the rates during the shared breeding season (mean difference=14%). Our study on the breeding biology of these echolocating cave-dwelling birds provides an example of spatial and temporal strategies that animals employ to partition resources within a confined habitat.

Temporal and interspecific dietary variation in wintering ducks in agricultural landscapes.

Farmlands are becoming more important as waterfowl foraging habitats, while natural wetlands are being lost globally. However, it is unclear how waterfowl coexist in agricultural landscapes by resource partitioning. We evaluated the diets of seven sympatric dabbling ducks foraging in rice paddy and lotus fields around Lake Kasumigaura, the second largest lake in Japan, during two wintering seasons (from November to February) by faecal DNA metabarcoding using chloroplast trnL and mitochondrial CO1 region sequences. We examined 420 faecal samples and found different patterns of dietary diversity and composition among the duck species. The pattern also differed between plant and invertebrate food. Dietary niche partitioning was clear in plant food. Large-bodied ducks intensively use crop plants, and other ducks might mediate competition by using terrestrial and aquatic plants that are suitable for their foraging behaviours or microhabitats. Dietary segregation among species was the most apparent in February, when the abundance of foraging ducks was the largest. This study illustrated the complex pattern of dietary niche partitioning of dabbling ducks in agricultural landscapes, which might be difficult to evaluate by conventional approaches. The availability of crop plants, as well as other plant food resources in flooted areas and farmland dikes, may enable ducks to coexist by spatial or behavioural resource partitioning.

Performance and challenges of Bi-directional resource allocation in multi-core space division multiplexing elastic optical networks

In space division multiplexing-elastic optical networks (SDM-EONs), crosstalk and fragmentation are the significant factors determining overall resource utilization. Crosstalk and fragmentation management spectral resource allocation schemes can enhance the overall resource utilization in SDM-EONs. This paper proposes three crosstalk and fragmentation management bi-directional resource allocation schemes for multi-core SDM-EONs to suppress inter-core crosstalk and network fragmentation. A spatial resource partitioning method is presented to mitigate inter-core crosstalk, and this paper adopts a k-shortest path routing method to suppress fragmentation while spectral resource allocation. To the best of our knowledge, there is no such scheme that handles both crosstalk and fragmentation together while allocating spectral resources in a counter-propagating manner for multi-core fiber (MCF) SDM-EONs. The estimated result shows that the proposed scheme outperforms the traditional co-propagation method and enhances existing resource utilization by reducing blocked requests.

Trophic Ecology and Resource Partitioning of Common Snook and Mexican Snook in the Usumacinta River Delta

AbstractCoexisting species often develop resource‐partitioning mechanisms to reduce their direct competition and optimize energy harvesting. Common Snook Centropomus undecimalis and Mexican Snook C. poeyi are carnivorous fish that coexist in estuaries of the Usumacinta River delta, in the southern Gulf of Mexico, and play an important role for fisheries and economy in this region. We analyzed spatial, temporal, and ontogenetic variability in trophic dynamics and distribution of Common and Mexican snooks. To identify patterns of trophic resource partitioning, we analyzed stomach content and stable isotopes (δ13C, δ15N) of the two species. Fifty‐one prey items were identified, with fish remains being the most abundant component (>35%). The two snook species appeared to be specialized carnivores of the third or fourth trophic level. Diet comparison indicated significant differences among species: Common Snook presented a higher proportion of fish from the families Engraulidae, Clupeidae, and Elopidae, while Mexican Snook consumed a higher fraction of fish from the families Cichlidae, Poeciliidae, and Loricariidae. The diet also presented significant variations between size‐classes. Small‐sized (<350 mm SL) Common Snook showed significantly higher reliance on invertebrates than large‐sized fish (>500 mm SL). Medium‐sized (351–499 mm SL) Mexican Snook consumed a higher proportion of Poeciliidae fish than small‐sized or large‐sized fish. The diet of the two snook species also presented important differences among seasons and sites. Trophic niche overlap between Common and Mexican snooks varied among systems, with higher overlap in the Pom−Atasta system than in the Palizada River. This study indicates that Common Snook and Mexican Snook have developed strategies for spatial partitioning of resources that favor their coexistence in the Usumacinta River delta.

Evidence for spatial and temporal resource partitioning of sharks at Roca Partida, an isolated pinnacle in the eastern Pacific

Evidence for spatial and temporal resource partitioning of sharks at Roca Partida, an isolated pinnacle in the eastern Pacific

Fine-scale coexistence between Mediterranean mesocarnivores is mediated by spatial, temporal, and trophic resource partitioning.

The partition of the ecological niche can enhance the coexistence of predators due to differences in how they exploit three main resources: food, space, and time, the latter being an axis that often remains unexplored.We studied niche segregation in a Mediterranean mesocarnivore community composed by Vulpes vulpes, Genetta genetta, Meles meles, and Herpestes ichneumon, addressing simultaneously different niche axes: the temporal, trophic, and spatial axes.We assessed temporal segregation between mesopredators and prey and between potential competitors, using camera trap data between 2018 and 2020 in a Mediterranean landscape in Southern Spain. We deployed camera traps in 35 stations in three sites with varying vegetation cover within Doñana National Park. We further examined the spatial overlap in activity centers and trophic preferences between potential competitors using diet information from studies performed in the study area.We found an overall temporal segregation between trophic generalist species, with species showing higher temporal overlap differing in their trophic preferences and/or showing limited spatial overlap. Furthermore, we observed an overall high overlap between the activity patterns of predators and their major prey in the area (the common genet vs. small mammals and the red fox vs. European rabbit).Our study suggests that coexistence of the different species that compose the mesocarnivore assemblage in Mediterranean landscapes can be facilitated by subtle differences along the three main niche axes, with temporal segregation being a most pronounced mechanism. Our findings reinforce the idea that the coexistence mechanisms underlying community structure are multidimensional.

Early positive biodiversity effects on total biomass in experimental tree seedling assemblages with and without water limitation

AbstractQuestionsWhile positive effects of tree diversity on tree community biomass have often been reported in mature stands, the debate on whether diversity effects may be detectable at the seedling level persists, with opposing outcomes found so far. We still lack a comprehensive evaluation of the biodiversity effects (so‐called ‘complementarity’ and ‘selection’ effects), as well as the phenotypic drivers at play, underlying early‐community biomass. Even less is known about whether such biodiversity effects may change under water‐limited conditions.LocationSeeds from four tree species coexisting in a Mediterranean forest (Spain).MethodsWe built experimental tree seedling assemblages with three diversity levels — monocultures, two‐species and four‐species mixtures — and under two soil moisture conditions. We quantified the extent to which species richness, species identity, community‐weighted mean (CWM) and functional dissimilarity (FD) influence complementarity and selection effects. We computed CWM and FD for seven functional traits related to water and light acquisition; and we calculated the complementarity and selection effects from above‐ and below‐ground biomass measures at the community level.ResultsOur results showed that complementarity drove the greater biomass in more diverse assemblages at the seedling stage. This pattern was largely favored by a particular species, Quercus faginea, with distinct phenotypic traits (great height, lateral ramification and root biomass with high dry matter content), which induced a positive effect of CWM on community biomass. Moreover, our study showed that the water deficit limited the production of above‐ground biomass without interacting with the community’s species richness.ConclusionOur study provides evidence that positive biodiversity effects on community biomass occur early, at the seedling stage, and it highlights the essential role that certain tree species play from their initial development stages by favoring spatial resource partitioning. Our work motivates future studies to apply integrated approaches in assessing both the community‐wide and species‐specific effects to understand the biodiversity–biomass relationship.

Focusing on individual plants to understand community scale biodiversity effects: the case of root distribution in grasslands

Spatial resource partitioning between species via differences in rooting depth is one of the main explanations for the positive biodiversity–productivity relationship. However, evidence for the importance of this mechanism is limited. This may be due to the community scale at which these interactions are often investigated. Community measures represent net outcomes of species interactions and may obscure the mechanisms underlying belowground interactions. Here, we assess the performance of ~1700 individual plants and their heterospecific neighbours over three growing seasons in experimental grassland plots containing one, four or sixteen different plant species and tested whether their performance in mixtures compared to monocultures was related to their own rooting depth versus the rooting depth of their heterospecific neighbours. Overall, individuals of deep‐rooting species performed better in mixtures and this effect significantly increased when surrounded by more shallow‐rooting species. This effect was not apparent for the shallow rooting species. Together, including both deep and shallow rooting species increased mixture performance. Our results show that taking the perspective of the individual rather than the community can elucidate the interactions between species that contribute to positive biodiversity effects, emphasizing the need for studies at different scales to disentangle the myriad interactions that take place in diverse communities.

Effects of human-altered landscapes on a reintroduced ungulate: Patterns of habitat selection at the rangeland-wildland interface

Successful species reintroductions require land managers to balance the goal of viable wildlife populations with potential risks to human enterprise. Such risks are particularly acute at the wildland-agriculture interface, where native and domestic species are likely to come into contact. In a national park in northern California, we combined insights from three lines of evidence – long-term visual surveys, short-term GPS telemetry, and satellite remote sensing-based animal detections – to characterize spatial overlap between reintroduced tule elk (Cervus canadensis nannodes) and domestic cattle and to estimate the importance of multiple environmental features as predictors of habitat selection by elk. Our results indicate that, at large spatial scales (i.e., home-range level), cattle were the primary driver of habitat selection, with the occurrence of elk being negatively associated with cattle across all seasons. In addition, elk consistently selected for grasslands on gentle, south-facing slopes that occurred at high elevation and close to ponds. NDVI was a seasonally important, positive predictor of habitat selection, with a marked reversal when this resource was concentrated inside of fenced cow pastures during the dry summer months. By contrast, a novel analysis of satellite-derived animal locations yielded no evidence of avoidance of cattle by elk (within pasture areas commonly used by elk), indicating that this population has acclimated to the presence of cattle through spatial partitioning of resources. Thus, this once-imperiled native ungulate exhibits patterns of habitat selection that reduce the potential for grazing conflicts with cattle, even in cases where access to forage is limited.

Effect of dominant parabiotic Ant‐Garden ants on the understory and ground‐dwelling ant assemblage in the Amazon rainforest

ABSTRACT Camponotus femoratus (Fabricius, 1804) and Crematogaster levior Longino, 2003 are Amazonian ants that jointly live in a parabiotic association in arboreal nests that are known as Ant‐Gardens (AGs). Both species are locally abundant and aggressive, which forage on the ground and on the vegetation. We evaluated, with extensive sampling, the effect of Ca. femoratus and Cr. levior on the ground and the understory dwelling of ant assemblages in the southern Amazon using pit‐fall traps, beating‐tray sampling, and baiting. We found that Ca. femoratus and Cr. levior caused a decrease in both the abundance and the species richness of the ground ants, changing the assemblage composition, and causing a nestedness pattern. Yet, AG ants seem to not promote significant changes in the assemblage of ants in the understory, with the exception of canopy openness and region, indicating a spatial resource partitioning. Our results showed that the frequency of these parabiotic AG ant pairs can modify the regional assemblage of the ground‐dwelling ants. As ants are ecological engineers and interact with numerous organisms in tropical habitats, the effect of the parabiotic ants can be extended to other organisms that inhabit the gaps along succession.

Effects of tree species richness on fine root production varied with stand density and soil nutrients in subtropical forests

Fine root production accounts for a large proportion of net primary production (NPP) in forest ecosystems that is highly responsive to environmental and biotic changes. The underlying mechanisms of the relationship between tree species richness and fine root production have not been fully examined. Here we hypothesized that: (i) the relationship between aboveground species richness and fine root production could be attributable to belowground spatial resource partitioning; (ii) either symmetrical or asymmetrical root proliferation to obtain nutrients leads to increased fine root production; and (iii) stand density affects the relationship between species richness and fine root production. We used an ingrowth core method to estimate fine root production coupled to molecular approaches for identifying the tree species of sampled fine roots within each ingrowth core. There was a significant and positive relationship between aboveground species richness and fine root production. The increase in fine root production might partially be attributed to asymmetrical root proliferation rather than belowground spatial resource partitioning. A piecewise structural equation model (SEM) linking stand density and soil nutrients revealed that both factors play dominant roles in mediating the effects of aboveground species richness on fine root production. Moreover, fine root production and relative abundance of fine root distribution within-layers both depended on the effects of aboveground species richness × stand density × soil phosphorus (P) interactions. Therefore, soil P concentration and stand density partially explained the positive aboveground species richness–fine root production relationship.

Limited evidence for spatial resource partitioning across temperate grassland biodiversity experiments.

Locally, plant species richness supports many ecosystem functions. Yet, the mechanisms driving these often-positive biodiversity-ecosystem functioning relationships are not well understood. Spatial resource partitioning across vertical resource gradients is one of the main hypothesized causes for enhanced ecosystem functioning in more biodiverse grasslands. Spatial resource partitioning occurs if species differ in where they acquire resources and can happen both above- and belowground. However, studies investigating spatial resource partitioning in grasslands provide inconsistent evidence. We present the results of a meta-analysis of 21 data sets from experimental species-richness gradients in grasslands. We test the hypothesis that increasing spatial resource partitioning along vertical resource gradients enhances ecosystem functioning in diverse grassland plant communities above- and belowground. To test this hypothesis, we asked three questions. (1) Does species richness enhance biomass production or community resource uptake across sites? (2) Is there evidence of spatial resource partitioning as indicated by resource tracer uptake and biomass allocation above- and belowground? (3) Is evidence of spatial resource partitioning correlated with increased biomass production or community resource uptake? Although plant species richness enhanced community nitrogen and potassium uptake and biomass production above- and belowground, we found that plant communities did not meet our criteria for spatial resource partitioning, though they did invest in significantly more aboveground biomass in higher canopy layers in mixture relative to monoculture. Furthermore, the extent of spatial resource partitioning across studies was not positively correlated with either biomass production or community resource uptake. Our results suggest that spatial resource partitioning across vertical resource gradients alone does not offer a general explanation for enhanced ecosystem functioning in more diverse temperate grasslands.

Mussels partition resources from natural waters under flowing conditions

The feeding of three co-occurring freshwater mussel species (Ptychobranchus fasciolaris, Quadrula quadrula and Potamilus alatus) of differing conservation status on river water from their collection site was examined under static and ecologically relevant flow conditions using three characteristics of the suspended river seston from a turbid river (Sydenham River, Ontario): (1) Chlorophyll a fluorescence; (2) size of fluorescent particles determined under flow cytometry; and (3) individual algal taxa identified under flow cytometry. Differences in the clearance rate (CR; water volume cleared of material per mussel and time) based on changes in chlorophyll a concentration were observed among species (P. alatus > Q. quadrula). Mussels had higher CR under flowing conditions and higher CR were observed on four of the nine algal taxa under flowing conditions. Feeding electivity analysis indicated that all mussel species selected for larger particles (28–35 μm size fraction) while rejecting smaller ones (12–19 μm). Whereas mussels did not appear to partition resources by size, mussel species exhibited resource partitioning of algal taxa (i.e., selectively feeding on different algal species; under flowing conditions: small centric diatoms were preferred by P. fasciolaris and Q. quadrula and avoided by P. alatus; Cryptomonas were preferred by P. fasciolaris and avoided by Q. quadrula and P. alatus; Chloromonas were preferred by P. alatus and avoided by P. fasciolaris). This study provides a novel mechanism, hydrodynamically mediated resource partitioning, in which the partitioning of resources occurs from within a flowing fluid rather than through the spatial or temporal partitioning of resources by organisms exploiting different microhabitats, to explain the existence of high mussel species richness within the same river reach (i.e., 24 species in this study). Unfortunately the species specific relationships noted above are likely vulnerable to climate change and changes in land use practice due to agriculture and urbanization.

Carnivore space use shifts in response to seasonal resource availability

AbstractEstimating spatial and temporal resource use and partitioning among carnivore species varies based on life history and is critical to understanding ecological relationships of sympatric carnivores and their prey. Temporal variation in food availability can have a substantial influence on distribution, foraging behavior, prey selection, and population dynamics of carnivores. We investigated shifts in space use of black bears (Ursus americanus), bobcats (Lynx rufus), coyotes (Canis latrans), and gray wolves (C. lupus) in response to seasonal availability of white‐tailed deer (Odocoileus virginianus) fawns in Michigan, USA, May–August 2009–2011. We used generalized linear mixed models to identify whether probabilistic fawn space use resulted in shifts in carnivore space use from deer pre‐parturition (PPP, 1 May–24 May) to fawn limited mobility (LMP, 25 May–30 June) and social mobility (SMP, 1 July–31 August) periods. We developed a rule‐based algorithm to identify “clusters” of carnivore GPS locations and investigated carnivore clusters to identify fawn predation sites. Carnivores shifted space use among periods, but responses varied among species regarding fawn space use. Black bears selected against areas with greater fawn use during LMP and selected areas with greater fawn use during SMP. We suggest black bear space use was unrelated to fawn space use and reflected availability of vegetative forage. Bobcats selected areas with greater fawn use during LMP and SMP. Coyotes were indifferent to areas where fawns occurred during LMP but selected against areas with greater fawn use during SMP, likely foraging on alternative prey. Coyotes were spatially constrained by wolves, selecting against areas with greater wolf use during LMP and SMP. Wolves selected against areas with greater fawn use during LMP and SMP and selected areas near habitat edges and areas containing livestock carcasses. Carnivore responses to fawn white‐tailed deer distribution and vulnerability were congruent with life history strategies, resulting in space use shifts in response to temporarily abundant resources. Carnivores did not overall rely predominantly on fawns, likely shifting their space use to maximize intake of other seasonal resources. These events provide additional insight into life history strategies among co‐occurring species and dynamics of multi‐species predator–prey systems.

Beaver activity increases habitat complexity and spatial partitioning by steelhead trout

Freshwater habitat restoration is a major conservation objective, motivating efforts to restore habitat complexity and quality for fishes. Restoration based on the engineering activities of beavers (Castor canadensis) increases fish habitat complexity, but how this affects fish habitat use and movement behaviours is not well known. We used a network of passive integrated transponder antennas to quantify small-scale movement and microhabitat use of 175 individual juvenile steelhead (Oncorhynchus mykiss) in a stream channel with a complex bathymetric profile resulting from a beaver impoundment and in a simplified channel devoid of beaver activity. Our results show that juvenile steelhead exploit microhabitat heterogeneity by employing a range of behaviours that maximizes available habitat via spatial and temporal partitioning among individuals. These results suggest spatial resource partitioning as a potential mechanism for the previously established positive correlations among steelhead density, survival, and production with beaver-based restoration within the study watershed. More broadly, our findings provide insight as to how populations can exploit habitat complexity through spatial partitioning that can be informative for planning restoration and management actions.

Trophic niche separation in sympatric rocky shore crabs

AbstractWhere two species occupy the same habitat and similar niches, competition is likely to drive small-scale spatial niche separation or resource partitioning that may not be immediately apparent. A stable isotope approach was used to investigate potential trophic niche separation between co-existing rocky shore crabs in the North-West (NW) Arabian Gulf. Leptodius exaratus and Pilumnopeus convexus which occupy similar shore height on the same rocky intertidal habitats. We also investigated conspecific differences between males vs females and adults vs juveniles. δ15N results indicated that adults of both species occupy a high trophic level in the rocky shore community, suggesting similar functional roles and potential for competition for food resources, while significant differences in δ13C values indicated differences in dietary sources between the two species, and also changes in diet between juveniles and adults in both species. MixSIAR analysis of δ15N and δ13C data confirmed field observations that both species are generalist omnivores, with potential for direct competition including adult predation on juveniles, including conspecifics. Differentiation in isotopic niches (SIBER analysis) was mainly driven by the significant differences in δ13C values, suggesting that co-existence of the two crab species is at least in part mediated by trophic niche separation or dietary resource partitioning, with some (unquantified) potential for spatial resource partitioning at the microhabitat level.

Habitat partitioning and diurnal-nocturnal transition in the elasmobranch community of a North Carolina estuary

In marine communities, resource partitioning can be as important as abiotic environmental preferences in determining habitat use patterns. Elasmobranchs are generally assumed to be crepuscular or nocturnal, but diel temporal habitat partitioning is poorly studied in this group. We attempted to identify habitat preferences and find evidence of resource partitioning among the elasmobranch community in Back and Core Sounds, North Carolina, using a multi-gear, fishery-independent survey with a temporal focus on the diurnal-nocturnal transition. Gillnet, longline, drumline, and rod-and-reel sampling captured a total of 160 elasmobranchs, representing 12 species within the estuary, and differences between the seven most abundant species were assessed in terms of temporal, environmental, and spatial habitat factors. The elasmobranch community was broadly divided into cool and warm temperature assemblages. Most species showed evidence of generalist habitat preferences, but spatial overlap between species was generally low. Blacknose sharks [Carcharhinus acronotus (Poey,1860)] appeared to be nocturnal, and aggregations of smooth dogfish [Mustelus canis (Mitchill,1815)] and spiny dogfish (Squalus acanthias Linnaeus, 1758) were found during mid-afternoon hours. Blacknose sharks and blacktip sharks [ Carcharhinus limbatus (Muller and Henle,1839)] showed evidence of spatial resource partitioning based on distance from the nearest inlet. Temperature appears to be a strong influence on the presence of elasmobranch species within Back and Core Sounds, but behavioral interspecific avoidance may be a greater influence on fine-scale habitat use by elasmobranchs in this estuarine system.

The roles of habitat and intraguild predation by coyotes on the spatial dynamics of kit foxes

AbstractIntraguild predation (IGP) by a dominant predator can drive the spatial dynamics of a subordinate predator and may explain space‐use patterns that deviate from theoretical predictions that species will use areas that maximize the availability of limited resources (resource availability hypothesis). Intraguild predation may suppress the distribution and abundance of mesopredators, but spatial resource partitioning may facilitate coexistence, with the subordinate carnivore utilizing suboptimal habitats. In arid systems, free‐standing water was historically scarce, limiting the distribution of larger‐bodied predators and offering large areas of refugia for smaller, arid‐adapted species, such as the kit fox (Vulpes macrotis). In these systems, the development of artificial water sources may facilitate an increase in the distribution and abundance of larger carnivores (e.g., coyotes [Canis latrans]), perhaps to the detriment of kit foxes. We coupled noninvasive genetic sampling and dynamic occupancy models to evaluate the spatial dynamics of kit foxes and their intraguild predators, coyotes, in western Utah, United States. We evaluated the influence of habitat characteristics on coyote occupancy patterns, and then investigated the role of habitat and coyotes on kit fox space use at multiple scales. Coyote occupancy was unrelated to water availability, but was positively related to the proportion of shrubland and woodland cover, a pattern consistent with predictions of the resource availability hypothesis. Supporting predictions of IGP theory, kit fox occupancy was negatively related to shrubland and woodland cover, minimizing overlap with land‐cover types favoring coyote occupancy. Furthermore, kit fox probability of local extinction was positively related to coyote activity. Interestingly, kit fox detection was positively related to coyote activity (i.e., kit fox detection was higher on spatial surveys with greater coyote sign), suggesting that at finer scales, kit foxes utilized riskier habitats to secure sufficient resources. Our results identified two alternative states predicted by IGP theory (i.e., intraguild predator dominated and coexistence of intraguild predator and intraguild prey) in a single system and elucidated the importance of considering dynamic processes and scale when investigating IGP.

The influence of evolutionary history and body size on partitioning of habitat resources by mammalian herbivores in south-eastern Australia

Habitat use is the most common dimension along which sympatric species partition resources to reduce competition. We conducted faecal pellet counts at Wilsons Promontory National Park, Victoria, to examine habitat use by an assemblage of mammalian herbivores with disparate evolutionary histories and varying body size: introduced European rabbit (Oryctolagus cuniculus) and hog deer (Axis porcinus), and native eastern grey kangaroo (Macropus giganteus), swamp wallaby (Wallabia bicolor) and common wombat (Vombatus ursinus). Overlap in habitat use was low between four pairs of species, suggesting spatial partitioning of resources to reduce the potential for interspecific competition. More generally, however, overlap in habitat use was high, particularly between native and introduced grazers. These results indicate the potential for competition if resources were limiting and suggest that assemblages of species with independent evolutionary histories have inherently less resource partitioning to facilitate coexistence than assemblages of species with common evolutionary histories. Despite evidence of high overlap in habitat use between native and introduced species at a broad scale, and variation in the competitive ability of species, coexistence was likely facilitated by niche complementarity, including temporal and fine-scale partitioning of spatial resources. There was no relationship between body size and the diversity of habitats used. In contemporary assemblages of native and introduced species, evolutionary history is likely to have a strong influence on resource partitioning.