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Abstract Megaherbivore carcasses represent sporadic but energetically rewarding resources for carnivores, offering a unique opportunity to study coexistence dynamics between facultative scavengers. South African fenced protected areas, such as Madikwe Game Reserve (Madikwe hereafter), host viable populations of large carnivores and high densities of elephants, Loxodonta africana. However, high carnivore densities can lead to potentially fatal interspecific encounters and increased competition, particularly around high‐quality trophic resources. This study explores the temporal partitioning and co‐detection strategies of carnivores at six elephant carcasses in Madikwe, aiming to understand how the increased carrion biomass available at elephant carcasses influences coexistence dynamics. Camera traps were deployed to monitor carcasses during two periods (2019 and 2020), revealing occurrences of six carnivore species. Carnivores, particularly black‐backed jackals, Lupulella mesomelas, (hereafter jackal), lions, Panthera leo, and spotted hyaenas, Crocuta crocuta, comprised 56.7% of carcass observations, highlighting their pivotal roles in scavenging dynamics. Pairwise co‐detection analysis demonstrated consistent association and shared peak activity periods between jackals and spotted hyaenas, indicating potential resource sharing. However, the minimal co‐detection rates between lions and other carnivores highlight their resource domination. There was some evidence of temporal partitioning between carnivores, with most species exhibiting earlier peaks in nocturnal activity to avoid temporal overlap with lions. This study emphasises the importance of elephant carcasses in the diet of multiple species and coexistence techniques utilised to exploit this ephemeral resource. As fenced protected areas become crucial for conserving intact carnivore guilds globally, further research into carnivore behavioural adaptations at carcasses is recommended to shed light on their coexistence strategies.

Abstract Southern hemisphere blue (Balaenoptera musculus intermedia) and fin (Balaenoptera physalus) whales are the largest predators in the Southern Ocean, with similarities in morphology and distribution. Yet, understanding of their life history and foraging is limited due to current low abundances and limited ecological data. To address these gaps, historic Antarctic blue (n = 5) and fin (n = 5) whale baleen plates, collected in 1947–1948 and recently rediscovered in the Smithsonian National Museum of Natural History, were analyzed for bulk (δ13C and δ15N) stable isotopes. Regular oscillations in isotopic ratios, interpreted as annual cycles, revealed that baleen plates contain approximately 6 years (14.35 ± 1.20 cm year−1) of life history data in blue whales and 4 years (16.52 ± 1.86 cm year−1) in fin whales. Isotopic results suggest that: (1) while in the Southern Ocean, blue and fin whales likely fed at the same trophic level but demonstrated niche differentiation; (2) fin whales appear to have had more regular annual migrations; and (3) fin whales may have migrated to ecologically distinct sub‐Antarctic waters annually while some blue whales may have resided year‐round in the Southern Ocean. These results reveal differences in ecological niche and life history strategies between Antarctic blue and fin whales during a time period when their populations were more abundant than today, and before major human‐driven climatic changes occurred in the Southern Ocean.

Abstract Forest soils are a critical component of terrestrial ecosystems and host a large number of animal decomposer species. One diverse and abundant decomposer taxon is oribatid mites (Acari: Oribatida), whose species composition varies with forest type and tree species composition. We used functional traits that indicate different niche dimensions, to infer assembly processes of oribatid mite communities in monocultures and mixed forests of native and introduced tree species. We found that coexisting species differed more in the resource‐related niche dimension, i.e., reproductive mode and trophic guild, than in the morphological dimension, e.g., body length and width, sclerotization and concealability. These results suggest that both filtering and partitioning processes structure oribatid mite communities. In native European beech forests, but not in non‐native Douglas fir forests, oribatid mites were mainly structured by filtering processes acting via traits related both to environmental tolerance and to resources. Furthermore, oribatid mite trait diversity, but not phylogenetic diversity, differed significantly between monocultures and mixed forests, demonstrating that multidimensional diversity indices provide additional information on soil biodiversity. Overall, the study provides evidence that traits representing different niche dimensions need to be considered for understanding assembly processes in soil animal communities and thereby soil biodiversity.

Abstract Species distribution and resource utilization are a fundamental aspect of ecology. By analyzing the tree space usage by birds and determining the species composition of birds across different parts of trees, our study could shed light on the mechanisms shaping co‐occurrence patterns in bird communities. Therefore, our study aimed to determine the species composition of birds across different parts of trees. We investigated whether species richness differs between positions on a tree and how these positions influence the probability of occurrence of the 10 most frequently observed bird species. To achieve this, we observed birds within permanent plots in Białowieża National Park (BNP) and analyzed the distribution patterns of birds within six vertical and three horizontal sectors of trees. The compositional dissimilarity between tree sectors was assessed using detrended correspondence analysis. We employed generalized linear mixed‐effects models to examine differences in species richness. The majority of the BNP bird community was associated with the branches, while other birds occupied the tree crown trunks and the understory trunks. Species richness was the highest on branches in the crown part of trees, followed by lower species richness on trunks associated with crowns, and the lowest richness was observed on branches and trunks in the understory. These results indicate that branches in the middle and lower parts of the crown serve as avian diversity hotspots on trees, likely due to the abundance of various food sources. The differing patterns of tree usage by specific bird species may suggest the avoidance of interspecific competition for resources. The study results of tree usage by bird species obtained in the primeval forest provides a reference point for studies conducted in human‐altered woods.

In territorial raptors, breeding performance and foraging behaviour are affected by territory characteristics as the abundance and availability of different prey species varies between habitats. In this study, we examined the diet of two White-tailed Eagle pairs, occupying neighbouring territories in two adjacent inland lakes in Northern Greece. We assess the diet composition of the species in the southernmost part of its European range and evaluate any intraspecific differences in the diet that may reflect resource and/or niche partitioning between territories. We found that birds and specifically waterbirds comprise the largest and quantitatively most important part of the White-tailed Eagle´s diet, with fish being the second most important prey group that was only found in the nest remains from one territory. There was high diet overlap between the two territories and when considering only avian prey our results suggest that the species predates on heavier (and the most common) waterbird species. A main factor that could be driving differences in the abundance and availability of different prey species between territories could be lake physiography, as our results point to a segregation and a subsequent resource partitioning between territories, with each pair utilizing an adjacent lake and its associated habitats. Competition and territoriality therefore seem to be important intraspecific interactions that along with prey availability could promote changes in territory size and ultimately affect individual fitness.

Pelagic sharks are top predators with key role in the structure and functioning of ocean ecosystems. However, little is known on their assemblage-wide trophic ecology. Specifically, fundamental data gaps exist over how trophic niches of pelagic sharks diverge both intra- and inter-specifically. To address this question, multi-tissue stable isotope analysis is a powerful tool that enables the quantification of trophic dynamics of mobile predators throughout ontogeny and across species. In this study, we utilized stable isotope analysis of carbon (δ13C) and nitrogen (δ15N) of tissues with varying turnover rates (muscle, red blood cells, liver, and plasma) to assess individual niche trajectories (i.e., temporal isotopic variation), population isotopic niche width, and isotopic niche overlap across five shark species (n = 155) in the eastern tropical Pacific Ocean: silky (Carcharhinus falciformis), blue (Prionace glauca), smooth hammerhead (Sphyrna zygaena), bigeye thresher (Alopias superciliosus), and the pelagic thresher shark (A. pelagicus). Overall, the relationship between isotopic niche trajectory length and body size was not significant, indicating that the magnitude of ontogenetic dietary variation does not increase in larger individuals. Pelagic sharks had variable feeding strategies over short-long time scales, likely reflecting species-specific responses to seasonality of prey availability and foraging location. Observed interspecific differences in isotope values indicate a degree of trophic niche partitioning across the five pelagic shark species. These data suggest ontogenetic niche shifts in pelagic sharks potentially differ from more coastal tied species and reveal species-specific ecological roles, but further studies on the diet and fine-scale habitat use are required to verify these results.

The Andaman and Nicobar Islands, India, a geographically remote region, harbor a diverse island ecosystem. Limited exploration has hindered our understanding of marine floral biodiversity in this area. To address this gap, we investigated seagrass meadows in the Andaman and Nicobar Islands to understand their spatial distribution, species composition, and habitat characteristics. We assessed 66 seagrass meadows, including 32 newly discovered ones, filling data gaps in the region’s seagrass coldspots. Seagrasses were found across a wide range of depths, with the majority occurring in shallow subtidal waters (< 8 m). Large-sized species such as Thalassia hemprichii, Enhalus acoroides, Cymodocea rotundata, Cymodocea serrulata, and Syringodium isoetifolium dominated the littoral and shallow subtidal zones, while smaller species such as Halophila spp. and Halodule spp. exhibited broader depth distributions. H. beccarii and H. decipiens were strictly intertidal and subtidal species, respectively. Water depth significantly influenced seagrass occurrence (p < 0.0001), cover (β = -0.2759; SE = 0.02471; p < 0.0001), shoot densities (β = -0.3556; SE = 0.1231; p = 0.005), and biomass (β = -0.3526; SE = 0.1159; p = 0.003). Sand availability emerged as the second significant predictor of seagrass distribution, cover, and biomass (p values < 2e-16, < 2e-16, and 0.01, respectively). Habitat heterogeneity decreased with increasing water depth, and seagrass species exhibited strong preferences for specific substrata, resulting in spatial niche partitioning. Our study provides novel insights into the seagrass spatial diversity, habitat characteristics, and seagrass-environment relationship in the Andaman and Nicobar Islands. Further, it highlights the importance of water depth, habitat characteristics, and substratum heterogeneity in seagrass distribution and growth. Lastly, our findings imply that any change to the benthic profile of the meadows will influence the seagrass species distribution and growth. Understanding these factors is crucial for seagrass conservation and management in the region, aiding the development of targeted strategies to protect these valuable marine habitats and associated biodiversity.

This article, published in the Journal of Experimental Botany, explores the role of light quality in the photosynthetic acclimation of Ostreococcus, a small green algae found in the ocean. The study focuses on two ecotypes of Ostreococcus, one habituated in shallow water and the other in deep water, and examines their genetic and physiological responses to different light conditions. The findings suggest that genetic modifications play a role in an organism's ability to adapt to environmental niches, and provide insights into the molecular mechanisms of photosynthetic acclimation in Ostreococcus. The study also identifies differentially expressed genes that may contribute to photosynthetic acclimation in Ostreococcus, but further research is needed to fully understand the process. Overall, this research contributes to our understanding of plant evolution, photosynthetic acclimations, and the conservation of marine ecosystems. [Extracted from the article]

Phytoplankton are exposed to dramatic variations in light quality when cells are carried by upwelling or downwelling currents or encounter sediment. We investigated the potential impact of light quality changes in Ostreococcus , a key marine photosynthetic picoeukaryote, by analysing changes in its transcriptome, pigment content, and photophysiology after acclimation to monochromatic red, green, or blue light. The clade B species RCC809, isolated from the deep euphotic zone of the tropical Atlantic Ocean, responded to blue light by accelerating cell division at the expense of storage reserves and by increasing the relative level of blue-light-absorbing pigments. It responded to red and green light by increasing its potential for photoprotection. In contrast, the clade A species OTTH0595, which originated from a shallow water environment, showed no difference in photosynthetic properties and minor differences in carotenoid contents between light qualities. This was associated with the loss of candidate light-quality responsive promoter motifs identified in RCC809 genes. These results demonstrate that light quality can have a major influence on the physiology of eukaryotic phytoplankton and suggest that different light quality environments can drive selection for diverse patterns of responsiveness and environmental niche partitioning. [ABSTRACT FROM AUTHOR]

Shifts in species' interactions are implicated as an important proximate cause underpinning climate-change-related extinction. However, there is little empirical evidence on the pathways through which climate conditions, such as ambient temperature, impact community dynamics. The timing of activities is a widespread behavioural adaptation to environmental variability, and temporal partitioning is a key mechanism that facilitates coexistence, especially within large carnivore communities. We investigated temperature impacts on community dynamics through its influence on the diel activity of, and temporal partitioning amongst, four sympatric species of African large carnivores: lions (Panthera leo), leopards (Panthera pardus), cheetahs (Acinonyx jubatus) and African wild dogs (Lycaon pictus). Activity of all species was shaped by a combination of light availability and temperature, with most species becoming more nocturnal and decreasing activity levels with increasing temperatures. A nocturnal shift was most pronounced in cheetahs, the most diurnal species during median temperatures. This shift increased temporal overlap between cheetahs and other carnivore species by up to 15.92%, highlighting the importance of considering the responses of interacting sympatric species when inferring climate impacts on ecosystems. Our study provides evidence that temperature can significantly affect temporal partitioning within a carnivore guild by generating asymmetrical behavioural responses amongst functionally similar species. [ABSTRACT FROM AUTHOR]

We investigated palaeofood web structures using stable isotope analyses on animal bone collagen from four Upper Palaeolithic sites dated to the Early Gravettian (Krems‐Hundssteig and Krems‐Wachtberg: 33–31k cal a bp, Langenlois: 31–29k cal a bp) and to the Early Epigravettian (Kammern‐Grubgraben: 24–20k cal a bp). In both periods, δ13C values show niche partitioning between hare, horse and mammoth on one side, and reindeer and ibex on the other, indicating different diets and habitats between both herbivore groups. The δ15N differences between carnivores and herbivores suggest a difference of one trophic level during the pre‐Last Glacial Maximum (pre‐LGM) period at the Early Gravettian sites and a tendency towards secondary carnivores during the LGM at Kammern‐Grubgraben. δ15N values of pre‐LGM mammoths are elevated in relation to other herbivores but shifted to the level of other herbivores in the LGM. A general δ15N value shift in herbivores of 3.3‰ from the pre‐LGM to the LGM is related to climatic deterioration. This may have led to the disappearance of certain ecological niches and to a shift from broader to overlapping ecological herbivore niches shortly before the LGM, as demonstrated by SIBER analyses. [ABSTRACT FROM AUTHOR]

Ecological theory predicts that closely-related species must occupy different niches to coexist. How marine top predators achieve this during breeding, when they often gather in large multi-species colonies and are constrained to central-place foraging, has been mostly studied in productive temperate and polar oceans with abundant resources, but less so in poorer, tropical waters. Here, we track the foraging movements of two closely-related sympatric seabirds—the white-tailed and red-tailed tropicbirds Phaethon lepturus and P. rubricauda—breeding on Aldabra Atoll, Seychelles, to investigate potential mechanisms of niche segregation and shed light on their contrasting population trends. Combining data from GPS, immersion, depth and accelerometry loggers, we show that the two species have similar behaviour at sea, but are completely segregated spatially, with red-tailed tropicbirds flying further to feed and using different feeding areas than white-tailed tropicbirds. Using nest-based camera traps, we show that low breeding success of both species—which likely drives observed population declines—is caused by high nest predation. However, the two species are targeted by different predators, with native avian predators mainly targeting red-tailed tropicbird nests, and invasive rats raiding white-tailed tropicbird nests when they leave their eggs unattended. Our findings provide new insight into the foraging ecology of tropicbirds and have important conservation implications. The extensive range and spatial segregation highlight the importance of considering large-scale protection of waters around tropical seabird colonies, while the high level of nest predation provides evidence in support of rat eradication and investigating potential nest protection from native avian predators. [ABSTRACT FROM AUTHOR]

Closely related species are predicted to have similar fundamental niches, and therefore to compete locally and possibly be constrained to occur allopatrically. Over time, niche differentiation should lead to divergent use of niche axes, such as food or habitat. Most studies of niche divergence or of niche conservatism have focused on multiple species at large spatial scales. We studied two species of closely related chipmunks at two spatial scales in the northern Sierra Nevada. The Long-eared Chipmunk (Tamias quadrimaculatus) and the Shadow Chipmunk (T. senex) are subcryptic species that exhibit extensive geographic overlap in the northern and central Sierra Nevada. Habitat use at the macrohabitat scale was similar, with both species reaching their highest mean abundance in Red Fir (Abies magnifica) forests, but exhibiting divergent secondary affinities. Additionally, macrohabitat associations of T. senex appear to differ from those reported 50 years ago within the same forest, suggesting flexibility in the face of structural habitat changes resulting from forest management actions, climate change, or other factors. At a finer spatial scale, habitat affinities of these chipmunks differed modestly, suggesting that local distribution emphasizes slightly different microhabitat characteristics. We conclude that these species exhibit niche conservatism overall, but whether microhabitat differences reflect competition or niche divergence requires further study. Because T. quadrimaculatus has the smallest geographic range of any Sierra Nevada sciurid, it may be at risk of local extirpation or substantial range restriction in the face of climate change, large-scale high-severity wildfires, and other stochastic threats; the present research sheds light on the ecology of these species, but has important relevance for regional resource managers as well. [ABSTRACT FROM AUTHOR]

Mesopredators play an important role in shaping communities, especially when apex predators are no longer present. To persist, mesopredators must confront competition by developing different coexistence strategies. In this study, we used detection and activity data derived from remote cameras to investigate the seasonal coexistence of mesopredators and their interactions with prey in a region of Southwest China where apex predators have been extirpated. We found that Siberian weasels (Mustela sibirica) occupied the entire study area, whereas masked palm civets (Paguma larvata) were restricted to <1,900 m in fall, and expanded their ranges up by about 600 m in spring to likely prey on small mammals. We detected weasels at almost all locations where civets were present, but detection rates and activity patterns for both species suggested avoidance of larger-bodied civets by weasels. We found that weasels were active at all hours and overlapped with all prey both spatially and temporally, whereas civets were nocturnal and crepuscular, which only overlapped with murid rodents. Although we did not directly observe intraguild or predator–prey interactions, evidence suggested that masked palm civets and Siberian weasels seem to coexist due to different seasonal dietary preferences, hunting strategies, and activity patterns. [ABSTRACT FROM AUTHOR]

Aims: Colonization by non‐native ants represents one of the gravest potential threats to island ecosystems. It is necessary to identify general mechanisms by which non‐native species are able to colonize and persist in order to inform future prevention and management. We studied a model‐island assemblage of 17 non‐native ant species with aim of identifying the spatial source of introductions and assessing how such a diversity of species are able to coexist. Location: Data were collected on Ascension Island: an ideal study system for its intermediate area, compact shape, spatial heterogeneity, lack of native ant species, and availability of non‐native ant records dating back to the 1800s. Methods: We collected over 47,000 individual ants from 73 sites using a range of baited traps and survey techniques. We combined this novel data with past occurrence records in order to determine whether human settlements have historically been the source of ant introductions and to quantify the mean rate at which species have dispersed across the island. Analysis of standardized field data revealed the extent to which ants were partitioning ecological niche space via (1) habitat separation, (2) fine‐scale resource partitioning and (3) climatic heterogeneity. Results: Ants were radiating at a linear rate of approximately 0.5 km2 per year from human settlements on this island, with the most widespread species having been introduced earliest. After accounting for incomplete colonization, we found no evidence to suggest habitat separation between species. Instead, we found significant niche separation through resource partitioning and weather‐dependent activity patterns. Main Conclusions: Our results indicate that non‐native ants can coexist in very close proximity and are therefore capable of existing at great diversity on even small islands. It is inevitable that ant colonization will continue without increased biosecurity measures, habitat restoration around settlements and conservation of native species populations. [ABSTRACT FROM AUTHOR]

Mesopredators including coyotes (Canis latrans) and red foxes (Vulpes vulpes) often co-occur in urban environments, but how niche partitioning facilitates their coexistence remains unclear. Highly urbanized areas can be spatial refuges for smaller mesopredators (i.e., spatial human shield effect), however these species also may coexist through temporal niche partitioning. We used camera traps (n = 110 sites) across an urbanization gradient in Chicago to examine coyote-fox interactions from 2011 to 2018. We analyzed spatial partitioning through multi-season occupancy models and structural equation modeling (SEM), and quantified temporal overlap between canids and with humans. Coyotes most often occurred in natural areas, and urbanization reduced their colonization rates and increased their extinction rates. Initial occupancy for red foxes was negatively impacted by urbanization, but their extinction rates depended on a surprising interaction between coyotes and humans. When coyotes were rare, fox extinction was related positively to human activity; but when coyotes were more common, fox extinction was related negatively to human activity. This outcome may reflect a human shield effect at a within-site scale. The SEM further supported the negative impact of urbanization on both canids, and lack of an effect of coyotes on the distribution of foxes. Diel activity of coyotes and red foxes indicated temporal niche partitioning intensified at more urbanized sites. Our results suggest the spatial human shield effect is not operating across sites in Chicago. Instead, coyotes and red foxes may share green spaces, especially in highly urbanized areas, where species coexistence is promoted by temporal niche partitioning. [ABSTRACT FROM AUTHOR]

The three‐dimensional structure of habitats is a critical component of species' niches driving coexistence in species‐rich ecosystems. However, its influence on structuring and partitioning recruitment niches has not been widely addressed. We developed a new method to combine species distribution modelling and structure from motion, and characterized three‐dimensional recruitment niches of two ecosystem engineers on Caribbean coral reefs, scleractinian corals and gorgonians. Fine‐scale roughness was the most important predictor of suitable habitat for both taxa, and their niches largely overlapped, primarily due to scleractinians' broader niche breadth. Crevices and holes at mm scales on calcareous rock with low coral cover were more suitable for octocorals than for scleractinian recruits, suggesting that the decline in scleractinian corals is facilitating the recruitment of octocorals on contemporary Caribbean reefs. However, the relative abundances of the taxa were independent of the amount of suitable habitat on the reef, emphasizing that niche processes alone do not predict recruitment rates. [ABSTRACT FROM AUTHOR]

Competition shapes animal communities, but the strength of the interaction varies spatially depending on the availability and aggregation of resources and competitors. Among carnivores, competition is particularly pronounced with the strongest interactions between similar species with intermediate differences in body size. While ecologists have emphasized interference competition among carnivores based on dominance hierarchies from body size (smaller = subordinate; larger = dominant), the reciprocity of exploitative competition from subordinate species has been overlooked even though efficient exploitation can limit resource availability and influence foraging.Across North America, fishers Pekania pennanti and martens (Martes spp.) are two phylogenetically related forest carnivores that exhibit a high degree of overlap in habitat use and diet and differ in body size by a factor of 2–5×, eliciting particularly strong interspecific competition. In the Great Lakes region, fishers and martens occur both allopatrically and sympatrically; where they co‐occur, the numerically dominant species varies spatially. This natural variation in competitors and environmental conditions enables comparisons to understand how interference and exploitative competition alter dietary niche overlap and foraging strategies.We analysed stable isotopes (δ13C and δ15N) from 317 martens and 132 fishers, as well as dietary items (n = 629) from 20 different genera, to compare niche size and overlap. We then quantified individual diet specialization and modelled the response to environmental conditions that were hypothesized to influence individual foraging.Martens and fishers exhibited high overlap in both available and core isotopic δ‐space, but no overlap of core dietary proportions. When the competitor was absent or rare, both martens and fishers consumed more smaller‐bodied prey. Notably, the dominant fisher switched from being a specialist of larger to smaller prey in the absence of the subordinate marten. Environmental context also influenced dietary specialization: increasing land cover diversity and prey abundance reduced specialization in martens whereas vegetation productivity increased specialization for both martens and fishers.Despite an important dominance hierarchy, fishers adjusted their niche in the face of a subordinate, but superior, exploitative competitor. These findings highlight the underappreciated role of the subordinate competitor in shaping the dietary niche of a dominant competitor. [ABSTRACT FROM AUTHOR]

One of the most invoked mechanisms mediating the positive effect of pollinator diversity on plant reproduction is pollinator's niche complementarity (i.e. partitioning of resource use by different pollinator species). However, the influence of spatial and temporal pollinator's niche complementarity on crop pollination function is rarely tested. We investigated the influence of spatial and temporal niche complementary in explaining sunflower crop production by comparing pollination activity at the edge and centre of crop fields and over the day. We found weaker evidence for spatial niche complementarity than for temporal niche complementarity in pollinator visitation rates. Only the visitation rate of hoverflies slightly differed between the centre and the edge of the fields. Nevertheless, we observed no differences in seed weight between the edge and the centre of the fields, but interestingly, plants allowed to be pollinated only by small-sized pollinators experienced a decline in seed production with distance from the edge. Pollinators did show complementary peak activity periods throughout the day, with Bombus terrestris and honeybees preferring to forage early in the day and at cooler temperatures than B. lapidarius and solitary bees. Unexpectedly, only morning- and only afternoon-pollinated plants produced similar seed weights, but these were higher than in all-day exposed plants. These findings indicate that sunflower fields shelter a small number of complementary pollinator species groups, which become rapidly redundant as diversity increases. Overall, we show that temporal and spatial niche complementarity effects on yield can unfold in unexpected ways, which are hard to predict without testing for the specific mechanisms.

Understanding the relative importance of different sources of selection (e.g., the environment, social/sexual selection) on the divergence or convergence of reproductive communication can shed light on the origin, maintenance, or even disappearance of species boundaries. Using a multistep approach, we tested the hypothesis that two presumed sister species of wolf spider with overlapping ranges and microhabitat use, yet differing degrees of sexual dimorphism, have diverged in their reliance on modality-specific courtship signaling. We predicted that male Schizocosa crassipalpata (no ornamentation) rely predominantly on diet-dependent vibratory signaling for mating success. In contrast, we predicted that male S. bilineata (black foreleg brushes) rely on diet-dependent visual signaling. We first tested and corroborated the sister-species relationship between S. crassipalpata and S. bilineata using phylogenomic scale data. Next, we tested for species-specific, diet-dependent vibratory and visual signaling by manipulating subadult diet and subsequently quantifying adult morphology and mature male courtship signals. As predicted, vibratory signal form was diet-dependent in S. crassipalpata, while visual ornamentation (brush area) was diet-dependent in S. bilineata. We then compared the species-specific reliance on vibratory and visual signaling by recording mating across artificially manipulated signaling environments (presence/absence of each modality in a 2 × 2 full factorial design). In accordance with our diet dependence results for S. crassipalpata, the presence of vibratory signaling was important for mating success. In contrast, the light and vibratory environment interacted to influence mating success in S. bilineata, with vibratory signaling being important only in the absence of light. We found no differences in overall activity patterns. Given that these species overlap in much of their range and microhabitat use, we suggest that competition for signaling space may have led to the divergence and differential use of sensory modalities between these sister species.

Neotropical shade-grown coffee systems are renowned for their potential to conserve avian biodiversity. Yet, little is known about food resources consumed by insectivorous birds in these systems, the extent of resource competition between resident and migratory birds, or how management of shade trees might influence diet selection. We identified arthropods in stomach contents from obligate and generalist insectivorous birds captured in mist-nets at five coffee farms in Chiapas, Mexico between 2001-2003. Overall stomach contents from 938 individuals revealed dietary differences resulting from changes in seasons, years, and foraging guilds. Of four species sampled across all management systems, Yellow-green Vireo (Vireo flavoviridis) prey differed depending on coffee shade management, consuming more ants in shaded monoculture than polyculture systems. Diets of obligate and generalist resident insectivores were 72% dissimilar with obligate insectivores consuming more Coleoptera and Araneae, and generalist insectivores consuming more Formicidae and other Hymenoptera. This suggests that obligate insectivores target more specialized prey whereas generalist insectivores rely on less favorable, chemically-defended prey found in clumped distributions. Our dataset provides important natural history data for many Nearctic-Neotropical migrants such as Tennessee Warbler (Leiothlypis peregrina; N = 163), Nashville Warbler (Leiothlypis ruficapilla; N = 69), and Swainson's Thrush (Catharus ustulatus; N = 68) and tropical residents including Red-legged Honeycreepers (Cyanerpes cyaneus; N = 70) and Rufous-capped Warblers (Basileuterus rufifrons; N = 56). With declining arthropod populations worldwide, understanding the ecological interactions between obligate and generalist avian insectivores gives researchers the tools to evaluate community stability and inform conservation efforts.

IntroductionMicrobial residents of the human oral cavity have long been a major focus of microbiology due to their influence on host health and intriguing patterns of site specificity amidst the lack of dispersal limitation. However, the determinants of niche partitioning in this habitat are yet to be fully understood, especially among taxa that belong to recently discovered branches of microbial life.ResultsHere, we assemble metagenomes from tongue and dental plaque samples from multiple individuals and reconstruct 790 non-redundant genomes, 43 of which resolve to TM7, a member of the Candidate Phyla Radiation, forming six monophyletic clades that distinctly associate with either plaque or tongue. Both pangenomic and phylogenomic analyses group tongue-specific clades with other host-associated TM7 genomes. In contrast, plaque-specific TM7 group with environmental TM7 genomes. Besides offering deeper insights into the ecology, evolution, and mobilome of cryptic members of the oral microbiome, our study reveals an intriguing resemblance between dental plaque and non-host environments indicated by the TM7 evolution, suggesting that plaque may have served as a stepping stone for environmental microbes to adapt to host environments for some clades of microbes. Additionally, we report that prophages are widespread among oral-associated TM7, while absent from environmental TM7, suggesting that prophages may have played a role in adaptation of TM7 to the host environment.ConclusionsOur data illuminate niche partitioning of enigmatic members of the oral cavity, including TM7, SR1, and GN02, and provide genomes for poorly characterized yet prevalent members of this biome, such as uncultivated Flavobacteriaceae.

An individual's foraging ecology can affect its growth and survival. Stable isotope analysis has been commonly used to investigate the foraging ecology of marine turtles. However, only a few studies have provided isotopic values for the critically endangered Kemp's ridley turtle (Lepidochelys kempii). This study presents the first characterization of δ13C and δ15N values from Kemp's ridley epidermal tissue in the coastal Gulf of Mexico, Florida, USA (28.834953°N, 82.761966°W) and investigates potential size-related differences in foraging ecology. Samples were collected from 64 neritic individuals between 2016 and 2021 and divided into two groups based on straight carapace length (SCL): a smaller (< 40 cm, n = 17) and a larger (> 40 cm, n = 47) size class. When analyzing all the data together, significant correlations were found between SCL and δ13C, but not SCL and δ15N. However, significant differences were found between size classes, with the larger size class exhibiting higher δ13C and lower δ15N values than the smaller size class, which may indicate niche partitioning between size classes. To compliment these findings, an animal-borne camera was deployed on a Kemp's ridley, and its foraging activity was documented. These results provide insights into the trophic and spatial dynamics of an understudied population and can be used to facilitate future research. Continued stable isotope analysis of Kemp's ridley epidermis, coupled with dietary studies and satellite telemetry, can expand on these findings to elucidate more about the foraging ecology of Kemp's ridleys and explore how dietary preferences may differ by individual size, which can guide conservation initiatives for foraging areas. [ABSTRACT FROM AUTHOR]

Changes in ecological preference, often driven by spatial and temporal variation in resource distribution, can expose populations to environments with divergent information content. This can lead to adaptive changes in the degree to which individuals invest in sensory systems and downstream processes, to optimize behavioural performance in different contexts. At the same time, environmental conditions can produce plastic responses in nervous system development and maturation, providing an alternative route to integrating neural and ecological variation. Here, we explore how these two processes play out across a community of Heliconius butterflies. Heliconius communities exhibit multiple Mullerian mimicry rings, associated with habitat partitioning across environmental gradients. These environmental differences have previously been linked to heritable divergence in brain morphology in parapatric species pairs. They also exhibit a unique dietary adaptation, known as pollen feeding, that relies heavily on learning foraging routes, or trap‐lines, between resources, which implies an important environmental influence on behavioural development. By comparing brain morphology across 133 wild‐caught and insectary‐reared individuals from seven Heliconius species, we find strong evidence for interspecific variation in patterns of neural investment. These largely fall into two distinct patterns of variation; first, we find consistent patterns of divergence in the size of visual brain components across both wild and insectary‐reared individuals, suggesting genetically encoded divergence in the visual pathway. Second, we find interspecific differences in mushroom body size, a central component of learning and memory systems, but only among wild caught individuals. The lack of this effect in common‐garden individuals suggests an extensive role for developmental plasticity in interspecific variation in the wild. Finally, we illustrate the impact of relatively small‐scale spatial effects on mushroom body plasticity by performing experiments altering the cage size and structure experienced by individual H. hecale. Our data provide a comprehensive survey of community level variation in brain structure, and demonstrate that genetic effects and developmental plasticity contribute to different axes of interspecific neural variation. [ABSTRACT FROM AUTHOR]

By understanding how assemblages segregate according to food types, it is possible to depict and understand species distribution and exploitation of similar food resources. Although it is well known that dung beetles may feed on carrion, but the attractiveness of different carrion types for these beetles is still poorly understood. In this study, we compared the dung beetle (Coleoptera: Scarabaeidae: Scarabaeinae) diversity attracted to two carrion types in different habitats in an Amazonian landscape. Dung beetles were captured by using pitfall traps baited with decaying cattle beef and cattle liver in native forest, peach palm plantation, teak plantation and exotic pasture. Overall, we captured 582 dung beetles of 43 species, where Canthidium aff. lentum was classified as a specialist of cattle beef, Deltochilum sp. One was considered specialist of liver carrion, 11 were considered generalists and for the 30 remaining species, it was not possible to determine their carrion preference due to the low number. Abundance, but not species richness, was affected by carrion type, and a higher number of beetles was recorded in beef‐baited traps compared to liver‐baited traps. According to functional groups, endocoprid beetles were more abundant in traps baited with decaying beef, while paracoprid and telecoprid beetles did not show preference for any carrion type. This study suggests a novel scenario of intra‐resource segregation, where species vary their preferences depending to the part of the dead corpse being exploited. The amount of food resource, the maintenance of stable populations and trophic preference mediated by chemical cues are some mechanisms that may explain the segregation of dung beetles among carrion types. [ABSTRACT FROM AUTHOR]

Changing ecological conditions along environmental gradients influence patterns of biodiversity and ecosystem functioning. However, how networks of interacting species respond to these changes remains unclear. We quantified aquatic food webs along longitudinal stream gradients spanning the Rocky Mountain–Great Plains ecotone using community composition, functional traits, and stable isotopes. We predicted that increasing ecosystem size, productivity, and species richness along the gradient would positively influence aquatic trophic diversity (e.g., expanded vertical and horizontal trophic niche breadths). We also predicted that trophic redundancy among fish species would decrease moving downstream as species partition food resources (e.g., reduced trophic niche overlap). Consumer stable isotope data (δ13C and δ15N) revealed nonlinear changes in trophic diversity along the gradient. Invertebrate trophic diversity had a dome‐shaped relationship with the gradient, strongly linked to an expanding then contracting δ13C range. Fish trophic diversity initially increased and then plateaued downstream, despite linearly expanding δ13C and δ15N ranges. Trophic redundancy within the fish community decreased downstream along the gradient. However, trophic redundancy also showed a nonlinear relationship with fish species richness; it initially declined, then began to increase when more than nine species were present, indicating a shift from niche partitioning to niche packing at intermediate species richness levels. This result suggests that while δ13C and δ15N ranges for fish communities increased across the gradient, niche packing within communities in the Great Plains caused overall trophic diversity to saturate. Our results demonstrate that food web structure along stream gradients reflects an interaction between factors that decrease trophic redundancy, such as increased living space and niche partitioning, versus factors that increase trophic redundancy, such as increased species richness and niche packing. Our study helps to explain how multiple mechanisms shape food web properties along longitudinal stream gradients, and where niche partitioning or niche packing may be dominant. Understanding the functional roles of organisms across similar environmental gradients in other ecosystems will be increasingly important because they determine how food webs, and thus ecosystem function, will respond to environmental change, biodiversity loss, or species invasions. [ABSTRACT FROM AUTHOR]

Research from terrestrial communities shows that diminished predation risk is a principal driver of heterospecific grouping behavior, with foraging ecology predicting the roles that species play in groups, as more vulnerable foragers preferentially join more vigilant ones from whom they can benefit. Meanwhile, field studies examining the adaptive significance of heterospecific shoaling among marine fish have focused disproportionately on feeding advantages such as scrounging or prey-flushing. Juvenile bonefish (Albula vulpes) occur almost exclusively among mojarras (Eucinostomus spp.) and even elect to join them over conspecifics, suggesting they benefit from doing so. We evaluated the roles of risk-related and food-related factors in motivating this pattern of affiliation, estimating: (1) the relative levels of risk associated with each species' search and prey capture activities, via behavioral vulnerability traits discerned from in situ video of heterospecific shoals, and (2) resource use redundancy, using stable isotopes (δ13C, δ15N, and δ34S) to quantify niche overlap. Across four distinct metrics, bonefish behaviors implied a markedly greater level of risk than those of mojarras, typified by higher activity levels and a reduced capacity for overt vigilance; consistent with expectations if their association conformed to patterns of joining observed in terrestrial habitats. Resource use overlap inferred from stable isotopes was low, indicating that the two species partitioned resources and making it unlikely that bonefish derived substantive food-related benefits. Collectively, these findings suggest that the attraction of juvenile bonefish to mojarras is motivated primarily by antipredator advantages, which may include the exploitation of risk-related social cues. [ABSTRACT FROM AUTHOR]

Theory posits that the persistence of species in ecological communities is shaped by their interactions within and across trophic guilds. However, we lack empirical evaluations of how the structure, strength and sign of biotic interactions drive the potential to coexist in diverse multi‐trophic communities. Here, we model community feasibility domains, a theoretically informed measure of multi‐species coexistence probability, from grassland communities comprising more than 45 species on average from three trophic guilds (plants, pollinators and herbivores). Contrary to our hypothesis, increasing community complexity, measured either as the number of guilds or community richness, did not decrease community feasibility. Rather, we observed that high degrees of species self‐regulation and niche partitioning allow for maintaining larger levels of community feasibility and higher species persistence in more diverse communities. Our results show that biotic interactions within and across guilds are not random in nature and both structures significantly contribute to maintaining multi‐trophic diversity. [ABSTRACT FROM AUTHOR]

Lava tubes are key targets in the search for life on Mars. Their basaltic walls provide protection from radiation and changing environmental conditions, which could enable life or preservation of previous life in an otherwise harsh environment. We can understand the potential for Martian life in lava tubes by studying the habitability of analog environments on Earth. In this study, we present the first characterization of the microbial life inside a pristine Mauna Loa lava tube. This study is the first to combine 16S SSU rRNA sequencing and whole genome shotgun sequencing to map the taxonomic makeup and functional potential of any lava tube community in Hawaii, enabling a deep understanding of the types of microbes that thrive in this unique environment and the metabolisms they use. We find a surprisingly high degree of niche partitioning over small spatial scales and discuss implications for life detection strategies. Based on recent bioinformatic advancements in metagenomics, we also assemble dozens of high‐quality metagenome assembled genomes from the microbes living in the lava tubes, including several novel species. Plain Language Summary: In the search for life on Mars, lava tubes are targets for astrobiology. Lava tubes provide an underground shelter, protected from radiation and the harsh climate. Analog studies here on Earth can help us understand what types of microbes live in these terrains and how best to find them. In this study, we investigate the microbial communities in a previously unexplored lava tube on the Mauna Loa volcano in Hawaii. We set out to characterize the microbes that live there and what capabilities enable them to survive, such as how they acquire nutrients from their environment to produce energy. We collected mineral samples in the lava tube and sequenced the DNA that we found in the minerals. We used DNA sequences to identify which microbes are present as well as which metabolisms they can use. We found that there are significant differences in the microbial make‐up of each of the samples, even though some are taken within several centimeters of each other, with implications for how to assay a region of interest on Mars. We also found several novel species. Key Points: In this undisturbed environment, communities were characterized by multiple microniches, varying widely over the scale of metersThe lava tube contained high amounts of "microbial dark matter" or uncultivated microbes that remain unclassified in taxonomic databasesAlthough the mineralogy of many of the samples we studied was sulfate‐rich, metabolisms unrelated to sulfur dominated the metagenome [ABSTRACT FROM AUTHOR]

Microbes are ubiquitous throughout the world's oceans, yet the manner and extent of their influence on the ecology and evolution of large, mobile fauna remains poorly understood. Here, we establish the intestinal microbiome as a hidden, and potentially important, 'functional trait' of tropical herbivorous fishes-a group of large consumers critical to coral reef resilience. Using field observations, we demonstrate that five common Caribbean fish species display marked differences in where they feed and what they feed on. However, in addition to space use and feeding behaviour-two commonly measured functional traits-we find that interspecific trait differences are even more pronounced when considering the herbivore intestinal microbiome. Microbiome composition was highly species specific. Phylogenetic comparison of the dominant microbiome members to all known microbial taxa suggest that microbiomes are comprised of putative environmental generalists, animal-associates and fish specialists (resident symbionts), the latter of which mapped onto host phylogeny. These putative symbionts are most similar to-among all known microbes-those that occupy the intestines of ecologically and evolutionarily related herbivorous fishes in more distant ocean basins. Our findings therefore suggest that the intestinal microbiome may be an important functional trait among these large-bodied consumers.

Animal populations take advantage of environmental heterogeneity to partition themselves into microhabitat niches. Such partitioning plays an important role in regulating interspecific competition and community structure by allowing multiple species to coexist. Atlantic Canada has many small coastal staging sites that host southbound migrant shorebirds. However, most shorebird studies in the region have been focused on larger sites in the Bay of Fundy, resulting in limited knowledge about staging ecology at these small sites, which often host more diverse shorebird assemblages. We examined niche partitioning by shorebirds on the Northumberland Strait, New Brunswick, Canada, to better understand how small coastal staging sites support diverse shorebird populations. We found evidence of partitioning on three niche dimensions: space, foraging behaviour, and diet. Most species specialized in at least one dimension, with foraging constraints based on bill morphology and habitat access based on species size likely driving segregation. Environmental heterogeneity at sites on the Northumberland Strait created multiple dimensions for segregation and fulfilled the niche requirements of diverse shorebird species during migratory staging. These findings broaden our understanding of staging ecology of multispecies flocks and suggest that conservation of small coastal sites is important for success of migratory shorebirds in Atlantic Canada.

Tropical rainforest communities are often characterized by a small number of species‐rich genera that contribute disproportionately to the alpha diversity in these habitats. In the Pacific Basin, there are nearly 200 species of Cyrtandra, most of which are white‐flowered woody shrubs that are single‐island endemics. Within these island communities, multiple Cyrtandra species are commonly observed to occur sympatrically in wet forest understories, forming swarms of what appear to be ecologically similar taxa. The aim of this study was to determine whether species of these plants are randomly assembled with respect to phylogenetic relatedness and traits that are ecologically relevant. I examined assembly patterns across three Pacific archipelagoes using a combination of 10 functional traits and a well‐resolved phylogeny comprising 34 species of Cyrtandra. Coexisting species were found to be more closely related and more phenotypically similar than would be expected by chance. This pattern was observed at both regional (island) and local (site) spatial scales. The retention of phylogenetic signal in floral traits and the strong influence of these traits on the observed degree of phylogenetic clustering may indicate that generalist insect pollinators act as a biotic filter on oceanic islands, driving selection for similar floral morphology among closely related species of Pacific Cyrtandra. Phylogenetic signal was also detected in leaf size, which contributed to niche clustering at both spatial scales. Coupled with a propensity for long‐distance dispersal, and the restricted distribution of Cyrtandra to rainforest understories, this finding suggests that environmental filtering along this trait axis may be more important than dispersal limitation in determining species assemblages. This study supports the theory that plant species are not randomly assembled, and instead, that niche‐based processes structure biodiversity at regional and local spatial scales in diverse congeneric species assemblages. [ABSTRACT FROM AUTHOR]

Ecological theory posits that higher species richness should be associated with greater exploitation of resources and niche packing resulting from either increasing species niche overlap or specialization of species' niches. Research evaluating niche theory in animals tends to focus on organisms among functional feeding guilds, while resource partitioning might be more critical within functional groups. Freshwater mussels (Family: Unionidae) are a diverse and imperiled group of animals that are ideal models to test niche occupancy due to their functional similarity as filter‐feeders and their occurrence in spatially and temporally stable multispecies aggregations. We evaluated the relationship between species richness and the trophic niche area for 25 mussel species occurring in 22 aggregations in the southeastern United States using stable isotope analysis (δ13C and δ15N) of soft tissue (n = 1057). Mean species standard ellipse area decreased with species richness, whereas ellipse overlap was not related to richness, indicating increased niche specialization may be the primary mechanism allowing coexistence in species‐rich communities. Total community isotopic area increased with richness, suggesting species‐rich communities also use a broader range of resources and may not be species‐saturated. Overall, our data support the niche‐packing hypothesis by illustrating the importance of niche partitioning within a species‐rich guild of aquatic animals. [ABSTRACT FROM AUTHOR]

Burying beetles of the genus Nicrophorus have become a model for studying the evolution of complex parental care in laboratory studies. Nicrophorus species depend on small vertebrate carcasses to breed, which they process and provision to their begging offspring. However, vertebrate carcasses are highly sought after by a wide variety of species and so competition is expected to be critical to the evolution of parental care. Despite this, the competitive environment for Nicrophorus is rarely characterized in the wild and remains a missing factor in laboratory studies. Here, we performed a systematic sampling of Nicrophorus orbicollis living near the southern extent of their range at Whitehall Forest in Clarke County, Georgia, USA. We determined the density of N. orbicollis and other necrophilous species that may affect the availability of this breeding resource through interference or exploitation competition. In addition, we characterize body size, a key trait involved in competitive ability, for all Nicrophorus species at Whitehall Forest throughout the season. Finally, we compare our findings to other published natural history data for Nicrophorines. We document a significantly longer active season than was observed 20 years previously at Whitehall Forest for both N. orbicollis and Nicrophorus tomentosus, potentially due to climate change. As expected, the adult body size of N. orbicollis was larger than N. tomentosus, the only other Nicrophorus species that was captured in 2022 at Whitehall Forest. The other most prevalent insects captured included species in the families Staphylinidae, Histeridae, Scarabaeidae, and Elateridae, which may act as competitors or predators of Nicrophorus young. Together, our results indicate significant variation in intra‐ and interspecific competition relative to populations within the N. orbicollis range. These findings suggest that the competitive environment shows extensive spatiotemporal variation, providing the basis to make predictions for how ecology may influence parenting in this species. [ABSTRACT FROM AUTHOR]

Biological invasions are usually examined in the context of their impacts on native species. However, few studies have examined the dynamics between invaders when multiple exotic species successfully coexist in a novel environment. Yet, long‐term coexistence of now established exotic species has been observed in North American lady beetle communities. Exotic lady beetles Harmonia axyridis and Coccinella septempunctata were introduced for biological control in agricultural systems and have since become dominant species within these communities. In this study, we investigated coexistence via spatial and temporal niche partitioning among H. axyridis and C. septempunctata using a 31‐year data set from southwestern Michigan, USA. We found evidence of long‐term coexistence through a combination of small‐scale environmental, habitat, and seasonal mechanisms. Across years, H. axyridis and C. septempunctata experienced patterns of cyclical dominance likely related to yearly variation in temperature and precipitation. Within years, populations of C. septempunctata peaked early in the growing season at 550 degree days, while H. axyridis populations grew in the season until 1250 degree days and continued to have high activity after this point. C. septempunctata was generally most abundant in herbaceous crops, whereas H. axyridis did not display strong habitat preferences. These findings suggest that within this region H. axyridis has broader habitat and abiotic environmental preferences, whereas C. septempunctata thrives under more specific ecological conditions. These ecological differences have contributed to the continued coexistence of these two invaders. Understanding the mechanisms that allow for the coexistence of dominant exotic species contributes to native biodiversity conservation management of invaded ecosystems. [ABSTRACT FROM AUTHOR]

Animals are integrated into the wider ecosystem via their foraging and behavior. The compensation hypothesis predicts that animals target their foraging efforts (i) toward nutrients that are scarce in the environment and (ii) toward nutrients that are not present in the usual diet of species, which varies across trophic levels. Understanding how foraging for resources varies locally, such as across habitat strata, and trophic levels will help to elucidate the links between the local environment and communities to the ecological functions that animals mediate. We examined whether the relative resource use of ants varies consistently along a habitat strata gradient and across trophic levels across Neotropical biomes. We placed 4500 baited tubes, each containing one of five liquid resources (sugar, amino acid, lipid, sodium, and distilled water) in one of three habitat strata (subterranean, epigaeic, and arboreal) across 60 transects in Amazon, Atlantic Forest, Caatinga, Cerrado, Pampa, and Pantanal biomes. We assessed the relative resource use of all ants across the habitat strata and among two different trophic groups across biomes. The relative preference for sugar increased from subterranean to arboreal strata in all biomes, while the relative preference for lipids decreased at this gradient in five biomes. We also found that in general sugar‐consuming ants foraged more for sugar and less for lipids than predatory ants across biomes. Conversely, we found no consistency across biomes in nutrient preference of amino acid and sodium across habitat strata or trophic levels. Overall, our results indicate sugar limitation in the arboreal stratum and lipid limitation on the ground across biomes and that the trophic level of ants strongly determines their foraging efforts—possibly because ants try to fix their dietary nutrient imbalances. Hence, our findings suggest strong local niche partitioning of sugar and lipid use across habitat strata and trophic levels and that other large spatial scale processes influence the local amino acid and sodium dynamics. [ABSTRACT FROM AUTHOR]

While biotic–abiotic interactions are increasingly documented in nature, a process‐based understanding of how such interactions influence community assembly is lacking in the ecological literature. Perhaps the most emblematic and pervasive example of such interactions is the synergistic threat to biodiversity posed by climate change and invasive species. Invasive species often out‐compete or prey on native species. Despite this long‐standing and widespread issue, little is known about how abiotic conditions, such as climate change, will influence the frequency and severity of negative biotic interactions that threaten the persistence of native fauna.Treefrogs are a globally diverse group of amphibians that climb to complete life‐cycle processes, such as foraging and reproduction, as well as to evade predators and competitors, resulting in frog communities that are vertically partitioned. Furthermore, treefrogs adjust their vertical position to maintain optimal body temperature and hydration in response to environmental change. Here, utilizing this model group, we designed a novel experiment to determine how extrinsic abiotic and biotic factors (changes to water availability and an introduced predator, respectively) interact with intrinsic biological traits, such as individual physiology and behaviour, to influence treefrogs' vertical niche.Our study found that treefrogs adjusted their vertical niche through displacement behaviours in accordance with abiotic resources. However, biotic interactions resulted in native treefrogs distancing themselves from abiotic resources to avoid the non‐native species. Importantly, under altered abiotic conditions, both native species avoided the non‐native species 33%–70% more than they avoided their native counterpart. Additionally, exposure to the non‐native species resulted in native species altering their tree climbing behaviours by 56%–78% and becoming more vertically dynamic to avoid the non‐native antagonist.Our experiment determined that vertical niche selection and community interactions were most accurately represented by a biotic–abiotic interaction model, rather than a model that considers these factors to operate in an isolated (singular) or even additive manner. Our study provides evidence that native species may be resilient to interacting disturbances via physiological adaptations to local climate and plasticity in space‐use behaviours that mediate the impact of the introduced predator. [ABSTRACT FROM AUTHOR]

The coexistence of multiple species competing for a finite set of resources is a widely debated topic in community ecology. Species with strongly overlapping niches are expected to drive each other towards exclusion, but such species may also coexist if they have similar competitive abilities. This compromise can lead to a peculiar pattern of clumped coexistence, where multiple species share similar niches, leaving gaps open in the theoretically available niche space. Large mammal herbivores may be a good example of this, where species' dietary niches clump as either grazers, browsers, or intermediate-feeders, rather than being continuously distributed over the resource gradient. Here, we develop a model of such emergent neutrality amongst species competing for a set of predefined resources each distributed along a finite niche axis. The model is commensurate with stable isotope niches, thus allowing us to compare its predictions with empirical evidence for changes in community niche structure over evolutionary time. We present stable carbon and oxygen isotope evidence for six discontinuous Late Quaternary assemblages from the central interior of South Africa, demonstrating the emergence of a clumped niche structure from an initial pattern of strongly overlapping diets. We show that species tend to cluster on parts of the niche axis where resource availability is highest, mirroring the proliferation of grazer species as landscapes became more grass-dominated. However, the presence of competition means that species' niches continue to differentiate, explaining the persistence of browser and intermediate-feeder species even in these open, predominantly treeless landscapes. These results highlight that species interactions are a necessary factor for robust inferences about the evolutionary dynamics of palaeocommunities. [ABSTRACT FROM AUTHOR]

Summary: Savannas cover a significant fraction of the Earth's land surface. In these ecosystems, C3 trees and C4 grasses coexist persistently, but the mechanisms explaining coexistence remain subject to debate. Different quantitative models have been proposed to explain coexistence, but these models make widely contrasting assumptions about which mechanisms are responsible for savanna persistence. Here, we show that no single existing model fully captures all key elements required to explain tree–grass coexistence across savanna rainfall gradients, but many models make important contributions. We show that recent empirical work allows us to combine many existing elements with new ideas to arrive at a synthesis that combines elements of two dominant frameworks: Walter's two‐layer model and demographic bottlenecks. We propose that functional rooting separation is necessary for coexistence and is the crux of the coexistence problem. It is both well‐supported empirically and necessary for tree persistence, given the comprehensive grass superiority for soil moisture acquisition. We argue that eventual tree dominance through shading is precluded by ecohydrological constraints in dry savannas and by fire and herbivores in wet savannas. Strong asymmetric grass–tree competition for soil moisture limits tree growth, exposing trees to persistent demographic bottlenecks. [ABSTRACT FROM AUTHOR]

Bite force is often associated with specific morphological features, such as sagittal crests. The presence of a pronounced sagittal crest in some tapirs (Perissodactyla: Tapiridae) was recently shown to be negatively correlated with hard‐object feeding, in contrast with similar cranial structures in carnivorans. The aim of this study was to investigate bite forces and sagittal crest heights across a wide range of modern and extinct tapirs and apply a comparative investigation to establish whether these features are correlated across a broad phylogenetic scope. We examined a sample of 71 specimens representing 15 tapir species (5 extant, 10 extinct) using the dry‐skull method, linear measurements of cranial features, phylogenetic reconstruction, and comparative analyses. Tapirs were found to exhibit variation in bite force and sagittal crest height across their phylogeny and between different biogeographical realms, with high‐crested morphologies occurring mostly in Neotropical species. The highest bite forces within tapirs appear to be driven by estimates for the masseter–pterygoid muscle complex, rather than predicted forces for the temporalis muscle. Our results demonstrate that relative sagittal crest height is poorly correlated with relative cranial bite force, suggesting high force application is not a driver for pronounced sagittal crests in this sample. The divergent biomechanical capabilities of different contemporaneous tapirids may have allowed multiple species to occupy overlapping territories and partition resources to avoid excess competition. Bite forces in tapirs peak in Pleistocene species, independent of body size, suggesting possible dietary shifts as a potential result of climatic changes during this epoch. [ABSTRACT FROM AUTHOR]

Large carnivore community structure is affected by direct and indirect interactions between intra‐guild members. Co‐existence between different species within a carnivore guild may occur through diet, habitat or temporal partitioning. Since carnivore species are highly dependent on availability and accessibility of prey, diet partitioning is potentially one of the most important mechanisms in allowing carnivores to co‐exist. Intra‐guild interactions may vary over time as carnivore prey preference and diet overlap can change due to seasonal changes in resource availability. We conducted scat analysis to compare the seasonal changes in prey preference, diet partitioning and niche breadth of four large carnivore species, namely leopard Panthera pardus, spotted hyena Crocuta crocuta, brown hyena Parahyaena brunnea and wild dog Lycaon pictus in central Tuli, Botswana. Large carnivores in central Tuli display a high dietary overlap, with spotted hyena and brown hyena displaying almost complete dietary overlap and the other carnivore species displaying slightly lower but still significant dietary overlap. Dietary niche breadth for both hyena species was high possibly due to their flexible foraging strategies, including scavenging, while leopard and wild dog showed a relatively low niche breadth, suggesting a more specialised diet. High dietary overlap in central Tuli is possibly explained by the high abundance of prey species in the area thereby reducing competition pressure between carnivore species. Our research highlights the need to assess the influence of diet partitioning in structuring large carnivore communities across multiple study sites, by demonstrating that in prey rich environments, the need for diet partitioning by carnivores to avoid competition may be limited. [ABSTRACT FROM AUTHOR]

One of the most invoked mechanisms mediating the positive effect of pollinator diversity on plant reproduction is pollinator's niche complementarity (i.e. partitioning of resource use by different pollinator species). However, the influence of spatial and temporal pollinator's niche complementarity on crop pollination function is rarely tested. We investigated the influence of spatial and temporal niche complementary in explaining sunflower crop production by comparing pollination activity at the edge and centre of crop fields and over the day. We found weaker evidence for spatial niche complementarity than for temporal niche complementarity in pollinator visitation rates. Only the visitation rate of hoverflies slightly differed between the centre and the edge of the fields. Nevertheless, we observed no differences in seed weight between the edge and the centre of the fields, but interestingly, plants allowed to be pollinated only by small-sized pollinators experienced a decline in seed production with distance from the edge. Pollinators did show complementary peak activity periods throughout the day, with Bombus terrestris and honeybees preferring to forage early in the day and at cooler temperatures than B. lapidarius and solitary bees. Unexpectedly, only morning- and only afternoon-pollinated plants produced similar seed weights, but these were higher than in all-day exposed plants. These findings indicate that sunflower fields shelter a small number of complementary pollinator species groups, which become rapidly redundant as diversity increases. Overall, we show that temporal and spatial niche complementarity effects on yield can unfold in unexpected ways, which are hard to predict without testing for the specific mechanisms. [ABSTRACT FROM AUTHOR]

Mycorrhizal symbiosis has been related to the coexistence and community assembly of coexisting orchids in few studies despite their obligate dependence on mycorrhizal partners to establish and survive. In hyper-diverse environments like tropical rain forests, coexistence of epiphytic orchids may be facilitated through mycorrhizal fungal specialization (i.e., sets of unique and dominant mycorrhizal fungi associated with a particular host species). However, information on the role of orchid mycorrhizal fungi (OMF) in niche differentiation and coexistence of epiphytic orchids is still scarce. In this study, we sought to identify the variation in fungal preferences of four co-occurring epiphytic orchids in a tropical rainforest in Costa Rica by addressing the identity and composition of their endophytic fungal and OMF communities across species and life stages. We show that the endophytic fungal communities are formed mainly of previously recognized OMF taxa, and that the four coexisting orchid species have both a set of shared mycorrhizal fungi and a group of fungi unique to an orchid species. We also found that adult plants keep the OMF of the juvenile stage while adding new mycobionts over time. This study provides evidence for the utilization of specific OMF that may be involved in niche segregation, and for an aggregation mechanism where adult orchids keep initial fungal mycobionts of the juvenile stage while adding others. [ABSTRACT FROM AUTHOR]

ABSTRACT The intra-host composition of horizontally transmitted microbial symbionts can vary across host populations due to interactive effects of host genetics, environmental, and geographic factors. While adaptation to local habitat conditions can drive geographic subdivision of symbiont strains, it is unknown how differences in ecological characteristics among host-symbiont associations influence the genomic structure of symbiont populations. To address this question, we sequenced metagenomes of different populations of the deep-sea mussel Bathymodiolus septemdierum, which are common at Western Pacific deep-sea hydrothermal vents and show characteristic patterns of niche partitioning with sympatric gastropod symbioses. Bathymodiolus septemdierum lives in close symbiotic relationship with sulfur-oxidizing chemosynthetic bacteria but supplements its symbiotrophic diet through filter-feeding, enabling it to occupy ecological niches with little exposure to geochemical reductants. Our analyses indicate that symbiont populations associated with B. septemdierum show structuring by geographic location, but that the dominant symbiont strain is uncorrelated with vent site. These patterns are in contrast to co-occurring Alviniconcha and Ifremeria gastropod symbioses that exhibit greater symbiont nutritional dependence and occupy habitats with higher spatial variability in environmental conditions. Our results suggest that relative habitat homogeneity combined with sufficient symbiont dispersal and genomic mixing might promote persistence of similar symbiont strains across geographic locations, while mixotrophy might decrease selective pressures on the host to affiliate with locally adapted symbiont strains. Overall, these data contribute to our understanding of the potential mechanisms influencing symbiont population structure across a spectrum of marine microbial symbioses that occupy contrasting ecological niches. IMPORTANCE Beneficial relationships between animals and microbial organisms (symbionts) are ubiquitous in nature. In the ocean, microbial symbionts are typically acquired from the environment and their composition across geographic locations is often shaped by adaptation to local habitat conditions. However, it is currently unknown how generalizable these patterns are across symbiotic systems that have contrasting ecological characteristics. To address this question, we compared symbiont population structure between deep-sea hydrothermal vent mussels and co-occurring but ecologically distinct snail species. Our analyses show that mussel symbiont populations are less partitioned by geography and do not demonstrate evidence for environmental adaptation. We posit that the mussel's mixotrophic feeding mode may lower its need to affiliate with locally adapted symbiont strains, while microhabitat stability and symbiont genomic mixing likely favors persistence of symbiont strains across geographic locations. Altogether, these findings further our understanding of the mechanisms shaping symbiont population structure in marine environmentally transmitted symbioses.