Niche partitioning in an assemblage of granivorous rodents, and the challenge of community-level conservation

Coexistence of competing species in the same foraging guild has long puzzled ecologists. In particular, how do small subordinate species persist with larger dominant competitors? This question becomes particularly important when conservation interventions, such as reintroduction or translocation, become necessary for the smaller species. Exclusion of dominant competitors might be necessary to establish populations of some endangered species. Ultimately, however, the goal should be to conserve whole communities. Determining how subordinate species escape competitive exclusion in intact communities could inform conservation decisions by clarifying the ecological conditions and processes required for coexistence at local or regional scales. We tested for spatial and temporal partitioning among six species of native, granivorous rodents using null models, and characterized the microhabitat of each species using resource-selection models. We found that the species’ nightly activity patterns are aggregated temporally but segregated spatially. As expected, we found clear evidence that the larger-bodied kangaroo rats drive spatial partitioning, but we also found species-specific microhabitat associations, which suggests that habitat heterogeneity is part of what enables these species to coexist. Restoration of natural disturbance regimes that create habitat heterogeneity, and selection of translocation sites without specific competitors, are among the management recommendations to consider in this case. More generally, this study highlights the need for a community-level approach to conservation and the usefulness of basic ecological data for guiding management decisions.

Counteracting Forces of Introgressive Hybridization and Interspecific Competition Shape the Morphological Traits of Cryptic Lberian Eptesicus Bats

Cryptic species that coexist in sympatry are likely to simultaneously experience strong competition and hybridization. The first phenomenon would lead to character displacement, whereas the second can potentially promote morphological similarity through adaptive introgression. The main goal of this work was to investigate the effect of introgressive hybridization on the morphology of cryptic Iberian Eptesicus bats when facing counteracting evolutionary forces from interspecific competition. We found substantial overlap both in dentition and in wing morphology traits, though mainly in individuals in sympatry. The presence of hybrids contributes to a fifth of this overlap, with hybrids showing traits with intermediate morphometry. Thus, introgressive hybridization may contribute to species adaptation to trophic and ecological space responding directly to the macro-habitats characteristics of the sympatric zone and to local prey availability. On the other hand, fur shade tended to be browner and brighter in hybrids than parental species. Colour differences could result from partitioning of resources as an adaptation to environmental factors such as roost and microhabitats. We argue that a balance between adaptive introgression and niche partitioning shapes species interactions with the environment through affecting morphological traits under selection.

Patchy Distributions and Distinct Niche Partitioning of Mycoplankton Populations across a Nearshore to Open Ocean Gradient

Fungi are an important, but understudied, group of heterotrophic microbes in marine environments. Traditionally, fungi in the coastal ocean were largely assumed to be derived from terrestrial inputs.

Mycorrhizal symbiosis changes host nitrogen source use

Purpose The ecological importance of arbuscular mycorrhizal fungi (AMF) in plant acquisition of inorganic and organic sources of nitrogen (N) is not clear. To improve understanding of the plant N nutrition ecology, we tested the effect of intraspecific competition and AMF in plant N source use in growth and N acquisition. Methods Solidago virgaurea was grown in microcosms in a fully factorial experiment under greenhouse conditions. The factors tested were intraspecific competition between seedlings and adult plants (yes, no), N source (NH4, glycine) and AMF (inoculated with Glomus hoi, not inoculated). Results When grown separately, non-mycorrhizal seedling growth was highest when grown with ammonium, but non-mycorrhizal adults grew best with glycine as the sole N source. Mycorrhizal symbiosis with Glomus hoi evened out this initial niche partitioning in terms of differences in N source use and all mycorrhizal plants grew best with ammonium. Competition shaped plant benefit from mycorrhizal symbiosis depending on the N source. Competition reduced mycorrhizal growth benefit in glycine-grown seedlings, but not in adults. Plant performance did not show uniform relationship with δ15N, but δ15N was affected by life stage, competition and mycorrhiza. Conclusions Plant competition and AMF shape plant N source use. Plant and AMF benefit of the symbiosis depend on the N source.

Niche Partitioning of 5 Sympatric Bornean Ungulates in Response to Spatiotemporal Variation in Fruit Availability and Resulting Implications for Predator-Prey Interactions

<p>Borneo’s rainforests are experiencing some of the fastest deforestation rates worldwide and are home to increasingly vulnerable species, most of which remain poorly understood. Bornean rainforests exhibit dramatic fluctuations in fruit and seed availability during mast-fruiting events which can exert considerable influence on frugivore ecology. Comprehensive spatiotemporal assessments of habitat use, resource partitioning, and responses to fruit availability in mast-fruiting rainforests are lacking for most species, including ungulates. The distribution and habitat use of an apex predator, the Sunda clouded leopard (Neofelis diardi), may be largely shaped by the availability of these ungulates. Yet, factors driving the spatial ecology of this elusive felid remain uncertain. I aimed to quantify spatiotemporal habitat use dynamics of these species and consequently inform effective conservation planning. Specifically, I quantified the effects of human activity, forest type, elevation, and mast-induced fluctuations in resources on the habitat use of lesser mousedeer (Tragulus kanchil), greater mousedeer (T. napu), Bornean yellow muntjacs (Muntiacus atherodes), red muntjacs (M. muntjak), and bearded pigs (Sus barbatus) in Gunung Palung National Park, West Kalimantan, Indonesian Borneo. I applied data from an extensive camera trapping study (n = 42,610 trap nights) to a modified single-season occupancy model to evaluate habitat use over space and time. I then applied estimates of occurrence (Ψ) of the five ungulate species to quantify if habitat use of the Sunda clouded leopard was influenced by prey occurrence and thus if this apex predator responded to bottom-up effects of resource variability. The results from the ungulate modelling revealed that forest type was an important predictor of habitat use of all ungulate species, each preferring different forest habitats. Habitat use estimates were highest in peat swamp forests for lesser mousedeer (Ψ = 0.92 ± 0.05), alluvial bench forests for greater mousedeer (Ψ = 0.52 ± 0.08), lowland granite forests for yellow (Ψ = 0.95 ± 0.07) and red muntjacs (Ψ = 0.98 ± 0.09), and freshwater swamp forests for bearded pigs (Ψ = 0.84 ± 0.07). Bearded pigs exhibited a link between variation in fruit availability and habitat use, indicating an ability to respond to resource variability. Occupancy modelling for Sunda clouded leopards revealed forest type, fruit availability, and bearded pig occurrence as the best predictors of habitat use. The highest estimates were associated with lowland granite forests (Ψ = 0.87 ± 0.09). My results reveal a novel pattern of niche partitioning through both food and habitat resources among five sympatric ungulate species and demonstrate that Sunda clouded leopards may use fruiting events as a cue for abundant prey. My research sheds light on important factors influencing habitat use of understudied ungulates and an apex predator and can be used to refine estimates of habitat suitability across a greater landscape to inform conservation practice amidst continually shrinking remnant forests in Indonesian Borneo.</p>

Niche Partitioning of 5 Sympatric Bornean Ungulates in Response to Spatiotemporal Variation in Fruit Availability and Resulting Implications for Predator-Prey Interactions

<p>Borneo’s rainforests are experiencing some of the fastest deforestation rates worldwide and are home to increasingly vulnerable species, most of which remain poorly understood. Bornean rainforests exhibit dramatic fluctuations in fruit and seed availability during mast-fruiting events which can exert considerable influence on frugivore ecology. Comprehensive spatiotemporal assessments of habitat use, resource partitioning, and responses to fruit availability in mast-fruiting rainforests are lacking for most species, including ungulates. The distribution and habitat use of an apex predator, the Sunda clouded leopard (Neofelis diardi), may be largely shaped by the availability of these ungulates. Yet, factors driving the spatial ecology of this elusive felid remain uncertain. I aimed to quantify spatiotemporal habitat use dynamics of these species and consequently inform effective conservation planning. Specifically, I quantified the effects of human activity, forest type, elevation, and mast-induced fluctuations in resources on the habitat use of lesser mousedeer (Tragulus kanchil), greater mousedeer (T. napu), Bornean yellow muntjacs (Muntiacus atherodes), red muntjacs (M. muntjak), and bearded pigs (Sus barbatus) in Gunung Palung National Park, West Kalimantan, Indonesian Borneo. I applied data from an extensive camera trapping study (n = 42,610 trap nights) to a modified single-season occupancy model to evaluate habitat use over space and time. I then applied estimates of occurrence (Ψ) of the five ungulate species to quantify if habitat use of the Sunda clouded leopard was influenced by prey occurrence and thus if this apex predator responded to bottom-up effects of resource variability. The results from the ungulate modelling revealed that forest type was an important predictor of habitat use of all ungulate species, each preferring different forest habitats. Habitat use estimates were highest in peat swamp forests for lesser mousedeer (Ψ = 0.92 ± 0.05), alluvial bench forests for greater mousedeer (Ψ = 0.52 ± 0.08), lowland granite forests for yellow (Ψ = 0.95 ± 0.07) and red muntjacs (Ψ = 0.98 ± 0.09), and freshwater swamp forests for bearded pigs (Ψ = 0.84 ± 0.07). Bearded pigs exhibited a link between variation in fruit availability and habitat use, indicating an ability to respond to resource variability. Occupancy modelling for Sunda clouded leopards revealed forest type, fruit availability, and bearded pig occurrence as the best predictors of habitat use. The highest estimates were associated with lowland granite forests (Ψ = 0.87 ± 0.09). My results reveal a novel pattern of niche partitioning through both food and habitat resources among five sympatric ungulate species and demonstrate that Sunda clouded leopards may use fruiting events as a cue for abundant prey. My research sheds light on important factors influencing habitat use of understudied ungulates and an apex predator and can be used to refine estimates of habitat suitability across a greater landscape to inform conservation practice amidst continually shrinking remnant forests in Indonesian Borneo.</p>

The effect of plant-fungi interaction generalism on plant community productivity

<p>Plant-plant productivity relationships within ecosystem and community ecology are contentiously debated in the literature due to the numerous factors involved making conclusions hard to draw and disentangle. There are several widely established and supported plant-plant productivity relationships. Increasing species richness can allow for greater niche complementarity, which in turn increases overall above and below ground productivity. Plants with different functional traits can differentially affect a plant community depending on the arrival time of the plant. These priority effects allow certain plants to outcompete others and persist in a community across different temporal scales. Plant species differ in their ability to interact with certain species of symbiotic partners in the soil (Arbuscular mycorrhizal fungi, AMF). This interaction generalism of a plant species indicates the ability of a plant to host many or few AMF species (generalist or specialist, respectively). However, there remains a limited understanding of plant-fungi relationships especially with respect to community productivity and the temporal effects of adding contrasting types of interaction generalism into an established community. The aim of this study was to determine the effects of the addition of an interaction specialist or generalist plant species into an established plant community on the overall community productivity. Three communities that differed in plant species richness were grown for 38 days at which point either a generalist or specialist was added. Community treatments were carried out in field soil, sterile soil and sterile soil reinoculated with viable field soil, separating the effects of plant niche-partitioning for plant-fungi interaction partners from the effects of niche-partitioning for other resources (e.g. soil nutrients). Community productivity was tested using different productivity measures; 1) carbon flux as the Net Ecosystem Exchange (NEE) of the community, 2) total above and below ground plant biomass, 3) neutral lipid fatty acid (NLFA) AMF biomarker, 16:1w5, extracted from total soil and total root mass to assess AMF biomass. It was difficult to disentangle the effects of species richness and interaction generalism on carbon flux in communities, with soil type clearly impacting these relationships. In all soil types, an increase in community plant richness had the greatest effect on carbon draw down and biomass productivity with respect to both plant and AMF biomass. In non-sterilised soil, interaction generalism, specifically the addition of a specialist alongside increased species richness corresponded to increased carbon drawdown. In the context of previous research, this study further highlighted the complexity of factors driving plant-plant-fungi relationships, but clearly identifies the positive role that species richness is having. Although the role of plant-fungi relationships in overall community productive remains unclear, this study provides a platform for future research to be undertaken.</p>