Resource Overlap Research Articles

Species traits, landscape quality and floral resource overlap with honeybees determine virus transmission in plant-pollinator networks.

Emerging infectious diseases pose a threat to pollinators. Virus transmission among pollinators via flowers may be reinforced by anthropogenic land-use change and concomitant alteration of plant-pollinator interactions. Here, we examine how species' traits and roles in flower-visitation networks and landscape-scale factors drive key honeybee viruses-black queen cell virus (BQCV) and deformed wing virus-in 19 wild bee and hoverfly species, across 12 landscapes varying in pollinator-friendly (flower-rich) habitat. Viral loads were on average more than ten times higher in managed honeybees than in wild pollinators. Viral loads in wild pollinators were higher when floral resource use overlapped with honeybees, suggesting these as reservoir hosts, and increased with pollinator abundance and viral loads in honeybees. Viral prevalence decreased with the amount of pollinator-friendly habitat in a landscape, which was partly driven by reduced floral resource overlap with honeybees. Black queen cell virus loads decreased with a wild pollinator's centrality in the network and the proportion of visited dish-shaped flowers. Our findings highlight the complex interplay of resource overlap with honeybees, species traits and roles in flower-visitation networks and flower-rich pollinator habitat shaping virus transmission.

Love thy neighbour: Feral buffalos show greater space use, resource overlap and encounters during the wet season in the Northern Territory.

Managing feral water buffalo in the Northern Territory is a formidable challenge. As an introduced species, buffalo are associated with a myriad of biosecurity, economic, cultural and environmental issues ranging from overgrazing, decreased water quality, disease vectors to the destruction of cultural assets. Nevertheless, the buffalo are also a harvestable resource that can support economic development of the region. To mitigate some of the biosecurity, economic, cultural and environmental risks they pose and manage buffalo effectively, we need a detailed understanding of their spatial and behavioural ecology. However, several factors make understanding how best to manage the dense populations of wild individuals challenging as buffalo inhabit remote areas with limited infrastructure and accessibility and their large size and often aggressive nature can make them difficult to observe in otherwise inaccessible areas. GPS tracking allows for high-frequency data collection and surveillance of individual buffalo. Here, we investigated how the different seasonal periods of a Northern Territory floodplain area shaped patterns of habitat use for 17 buffalo tracked over 16 months. We found in the dry season, buffalo space use is restricted, and the size of home ranges are significantly smaller than in the wet season. During the wet season, buffalo expand their home range area as well as their social encounter area with other buffalo. These differences in their space use and social patterns suggest that increased disease surveillance may be needed for the wet season when buffalo are more likely to share space and interact. During the dry season, however, buffalo movement is more predictable and restricted, suggesting greater optimisation opportunities for buffalo management. Results from these models can be used by land holders, Traditional Owners and wildlife managers to make evidence-based decisions to improve buffalo management with respect to disease risk, sustainable harvest and damage to environmental and cultural assets.

High Resource Overlap and a Consistently Generalised Pattern of Interactions in a Bat-Flower Network in a Seasonally Dry Landscape.

Pollination is an ecosystem process that is crucial to maintain biodiversity and ecosystem function. Bats are important pollinators in the tropics and are an integral part of complex plant-pollinator interaction networks. However, network analysis-based approaches are still scarce at the plant species and bat community levels. We used metabarcoding to identify plant taxa present in pollen from fur and faecal samples collected across 1 year from three nectar-feeding bat roosts in central Mexico. We calculated the frequency of occurrence of plant taxa and assembled a zoocentric network of bat-plant interactions. We constructed a year-long network, encompassing the entire period of sampling, two seasonal networks comprising the wet and dry seasons, and six individual networks from sampling at two-month intervals across the year. Four species of nectar-feeding bats interacted with 36 plant species from 16 families. We found highly generalised interaction patterns across networks corresponding with opportunistic feeding behaviour by bats, with little seasonal variation in network structure. There was high resource overlap between bat species, and bats visited a diverse range of plant species even during periods with a high abundance of particular resources in the landscape. The diverse diet of nectar-feeding bats emphasises the importance of floristically rich natural habitats in the landscape to provide reliable foraging resources year-round in a seasonally variable system. While a generalised network structure is thought to increase robustness, further research is necessary to understand how fluctuations in pollinator abundance and diversity in the face of land use and climate change may impact bat-flower networks and the consequences to plant communities.

Beta diversity patterns and driving mechanisms of stream bacteria and fungi on Mt. Kilimanjaro

Aquatic microbes, which are highly diverse in freshwater biofilms, play a vital role in shaping the structure and functioning of ecosystems. Nevertheless, the influence of environmental factors on aquatic microbes in different biogeographic ecosystems, especially in tropical mountains, is relatively unexplored. Here, we examined the relative influence of climate and physicochemical factors on beta diversity of stream bacteria and fungi using 16S rRNA amplicon sequencing at 40 sites on Mt. Kilimanjaro. Towards larger elevational distance, the total beta diversity and turnover of bacteria and fungi increased significantly, while nestedness decreased. The beta diversity of fungi showed greater spatial variation than that of bacteria, while the local contribution to beta diversity (LCBD) showed U-shaped elevational pattern for both taxa. Bacteria and fungi had strong positive relationships regarding the total beta diversity, LCBD and their components, except for nestedness, indicating similar environmental preferences and resource overlap. Among environmental variables, mean annual temperature, water depth and elevation predicted microbial beta diversity, while water depth, mean annual temperature and precipitation primarily affected LCBD. Overall, climate-related variables were the dominant factors for beta diversity and their effects were more pronounced for fungi than bacteria. The contrasting patterns of bacterial and fungal beta diversity and their ecological interactions in tropical aquatic ecosystems provide a rare dataset for assessing ecological functions in understudied aquatic ecosystems and predicting the impact of global change on microorganisms.

Resource overlap and infrequent predation on key pests show vulnerability in cotton biological control services

Promoting arthropod biodiversity to increase ecosystem services through ecological intensification is a challenge for agriculture. And recent evidence suggests that standard pesticide applications not only harm natural enemies but may also fail to deliver long-term pest control solutions. To fuel ecological intensification and build predictive frameworks for pest management incorporating estimates of pest abundance, natural enemy abundance and their associated interactions is essential. Within this framework, there is a need to shift the focus from a single pest and predator to consider the community of predatory arthropods that interact with communities of prey. We took a network-based approach to investigate community interactions of predatory arthropods that feed on key pests and alternative prey in cotton over a three-year period. We merged prey activity, generalist predator communities collected from cotton canopies, and reconstructed trophic interactions with DNA detection frequencies estimated from molecular gut content analysis. Overall, many predator diets overlap, resulting in similar foraging patterns on groups of cotton pests. Moreover, predation on key cotton pests, such as stink bugs and white flies, was low. Therefore, ecological intensification that increases specialized arthropod predators within the community should improve biological control service delivery.

Effect of Human Activity and Presence on the Behavior of Long-Tailed Macaques (Macaca fascicularis) in an Urban Tourism Site in Kuala Selangor, Malaysia.

The increasing overlap of resources between human and long-tailed macaque (Macaca fascicularis) (LTM) populations have escalated human-primate conflict. In Malaysia, LTMs are labeled as a 'pest' species due to the macaques' opportunistic nature. This study investigates the activity budget of LTMs in an urban tourism site and how human activities influence it. Observational data were collected from LTMs daily for a period of four months. The observed behaviors were compared across differing levels of human interaction, between different times of day, and between high, medium, and low human traffic zones. LTMs exhibited varying ecological behavior patterns when observed across zones of differing human traffic, e.g., higher inactivity when human presence is high. More concerning is the impact on these animals' welfare and group dynamics as the increase in interactions with humans takes place; we noted increased inactivity and reduced intra-group interaction. This study highlights the connection that LTMs make between human activity and sources of anthropogenic food. Only through understanding LTM interaction can the cause for human-primate conflict be better understood, and thus, more sustainable mitigation strategies can be generated.

Isotopic niche overlap among foraging marine turtle species in the Gulf of Mexico.

Sympatric species may overlap in their use of habitat and dietary resources, which can increase competition. Comparing the ecological niches and quantifying the degree of niche overlap among these species can provide insights into the extent of resource overlap. This information can be used to guide multispecies management approaches tailored to protect priority habitats that offer the most resources for multiple species. Stable isotope analysis is a valuable tool used to investigate spatial and trophic niches, though few studies have employed this method for comparisons among sympatric marine turtle species. For this study, stable carbon, nitrogen, and sulfur isotope values from epidermis tissue were used to quantify isotopic overlap and compare isotopic niche size in loggerhead (Caretta caretta), green (Chelonia mydas), and Kemp's ridley (Lepidochelys kempii) turtles sampled from a shared foraging area located offshore of Crystal River, Florida, USA. Overall, the results revealed high degrees of isotopic overlap (>68%) among species, particularly between loggerhead and Kemp's ridley turtles (85 to 91%), which indicates there may be interspecific competition for resources. Samples from green turtles had the widest range of isotopic values, indicating they exhibit higher variability in diet and habitat type. Samples from loggerhead turtles had the most enriched mean δ34S, suggesting they may forage in slightly different micro-environments compared with the other species. Finally, samples from Kemp's ridley turtles exhibited the smallest niche size, which is indicative of a narrower use of resources. This is one of the first studies to investigate resource use in a multispecies foraging aggregation of marine turtles using three isotopic tracers. These findings provide a foundation for future research into the foraging ecology of sympatric marine turtle species and can be used to inform effective multispecies management efforts.

Phenological overlap of terrestrial and marine food resources did not reduce salmon consumption by Kodiak brown bears

Climate change is altering the predictability of timing of resource pulses and how consumers interact with them, resulting in phenomena placed under the trophic mismatch hypothesis (TMH). This occurs when a consumer fails to overlap and capitalize on availability of a key food resource pulse. Such changes to predator-prey interactions can alter nutrient transfer, destabilize food webs, and reduce species reproduction and survival. Brown bears (Ursus arctos) on the Kodiak Archipelago, Alaska, USA, have purportedly altered their foraging toward increased use of terrestrial resources under TMH. We examined how the extent of within- and across-year overlap between abundances of Pacific salmon (Oncorhynchus spp.) and berries altered salmon assimilation by brown bears on the Kodiak Archipelago during 2015–2017. We further examined whether salmon consumption differed with brown bear sex and age. We found no decrease in salmon assimilation in response to variation in terrestrial and marine food overlap across and within years. Overall salmon assimilation was high, representing over 60% of brown bear diets in 2015 and 2017, with lower (44%) consumption of salmon in 2016 corresponding with a 28% reduction in salmon abundance. Within years, monthly salmon assimilation was lower in June when salmon began to enter the system, then increased and remained similar during July–October, despite 0–71% within month overlap in peak salmon and berry availability. Older brown bears, particularly males, consumed more salmon than did females and younger bears. While the potential ecosystem impacts of TMH may pose a lesser threat to brown bears than previously reported, possible future declines in Pacific salmon abundance due to climate change may adversely affect North American coastal brown bear populations by reducing abundance of this important food source.

Sperm and northern bottlenose whale interactions with deep-water trawlers in the western North Atlantic.

Commercial fisheries have increased in all the world's oceans with diverse unintended impacts on marine ecosystems. As a result of resource overlap, interactions between cetaceans and fisheries are a common occurrence and, in many cases, can give rise to significant conservation issues. Research on the distribution and types of such interactions is important for efficient management. In this study, we describe the behaviors of two whale species: sperm whales (Physeter macrocephalus) and northern bottlenose whales (Hyperoodon ampullatus), interacting with benthic trawlers fishing off the eastern Grand Banks of the western North Atlantic in 2007. Whale interactions were only observed when vessels were targeting Greenland halibut (Reinhardtius hippoglossoides) in deep-water fishing areas and were most common during net hauling. Sperm whales and northern bottlenose whales appeared to engage in feeding behavior close to the surface during hauling, especially during the latter stages, suggesting they targeted fish escapees rather than discards. Using photo-identification methods, seven individual sperm whales were identified with multiple resights of six individuals being recorded over an almost two month period. The maximum distance between two resights was 234 km, suggesting individual sperm whales were repeatedly targeting and even following fishing vessels over multiple days and between fishing areas. By contrast, there were no photographic resights of individual northern bottlenose whales within this study, or with substantial photo-identification catalogues from other adjacent high density areas, suggesting that individuals of this species may be less likely to follow vessels or move between areas. This study documents the earliest confirmed records of northern bottlenose whales in this remote region. These interactions and high encounter rates may indicate that adjacent populations are recovering from the previous century of commercial whaling. Our study provides new insights and details on whale-fisheries interactions, which can inform future research and help managers understand the real and perceived impacts of depredation behaviour on fisheries and whales.

Multi‐scale habitat overlap in two broad‐ranged sympatric Neotropical forest eagles reveals shared environmental space and habitat use

Quantifying resource partitioning between co‐occurring species can provide insight into processes facilitating coexistence by closely related species, a fundamental question in ecology. We tested whether the habitat requirements of two closely related Neotropical forest eagles, the Crested Eagle Morphnus guianensis and Harpy Eagle Harpia harpyja, differ at fine and coarse resolutions across their shared geographical range. Using landcover and topographical covariates, we quantified potential resource overlap first using higher resolution (30 arc‐s, ~ 1‐km2 data) generalized linear models (GLMs), and secondly using coarser‐grain (2.5 arc‐min, ~ 4.5‐km2 data) environmental ordination to capture the potential effect of scale on habitat overlap. The distribution of both eagles was largely explained by canopy tree species richness and canopy structural complexity, with peak suitability of 60–80% evergreen forest cover. Both eagles were negatively associated with mosaic forest and cultivated areas. From the GLMs, habitat overlap was >93% in geographical space but was reduced to 73% when considering environmental space, a proxy for resource overlap. From ordination (principal component analysis), resource overlap was 67% in environmental space, with randomization tests supporting equivalent environmental space for both eagles. Our results suggest that at the continental scale, Crested and Harpy Eagles share identical environmental space when quantified at fine and broad scales, with little difference in distribution and habitat use. At the continental scale used here, both eagles can coexist, presumably with sufficient habitat heterogeneity for coexistence when they occur in close proximity. Therefore, further research is required at the local level to capture fully where coexistence at the local scale is facilitated more by fine‐scale habitat selection, or difference in diet between two species with indistinguishable habitat use.

Construction group conflict under resource overlap: a game theory approach

Construction group conflict under resource overlap: a game theory approach

Metabolic resource overlap impacts competition among phyllosphere bacteria

The phyllosphere is densely colonised by microbial communities, despite sparse and heterogeneously distributed resources. The limitation of resources is expected to drive bacterial competition resulting in exclusion or coexistence based on fitness differences and resource overlap between individual colonisers. We studied the impact of resource competition by determining the effects of different bacterial colonisers on the growth of the model epiphyte Pantoea eucalypti 299R (Pe299R). Resource overlap was predicted based on genome-scale metabolic modelling. By combining results of metabolic modelling and pairwise competitions in the Arabidopsis thaliana phyllosphere and in vitro, we found that ten resources sufficed to explain fitness of Pe299R. An effect of both resource overlap and phylogenetic relationships was found on competition outcomes in vitro as well as in the phyllosphere. However, effects of resource competition were much weaker in the phyllosphere when compared to in vitro experiments. When investigating growth dynamics and reproductive success at the single-cell resolution, resource overlap and phylogenetic relationships are only weakly correlated with epiphytic Pe299R reproductive success, indicating that the leaf’s spatial heterogeneity mitigates resource competition. Although the correlation is weak, the presence of competitors led to the development of Pe299R subpopulations that experienced different life histories and cell divisions. In some in planta competitions, Pe299R benefitted from the presence of epiphytes despite high resource overlap to the competitor strain suggesting other factors having stronger effects than resource competition. This study provides fundamental insights into how bacterial communities are shaped in heterogeneous environments and a framework to predict competition outcomes.

Spatio-Temporal Coupling Analysis of Differences in Regional Grain–Economy–Population and Water Resources

In the context of climate change and the intensification of population activities, differences in regional water resources are the main drivers leading to these resources’ unbalanced development. This problem can be addressed by exploring spatial differences and spatio-temporal patterns. Based on the spatio-temporal trends of grain production, social economy, population, and water resources in the Tarim River Basin from 2005 to 2020, this paper uses the barycenter model coupling situation model to analyze the evolutionary trend of the barycenter, spatial overlap and spatio-temporal coupling degree for each index. The results show the following: (1) The spatio-temporal distribution of grain production was larger in the east than in the west. Grain production increased by 18.10% across the basin, and the migration rate of the grain center of gravity (CG) was 16.61 km/a. (2) The spatio-temporal distribution of the economy was greater in the south than in the north, with a cumulative migration of 323.10 km to the southwest. During the study period, the population remained concentrated in the western portion of the basin, increasing 25.18% compared to the population prior to 2005. The spatial variation range of total water resources was small, showing a trend of slow increase from west to east. (3) The overlap between GDP and population was enhanced, with the coupling showing a slow rising trend. The overlap of water resources and grain space also increased and the consistency index was high. From 2011 to 2020, the average consistency index was 0.594 and the coupling degree of the two factors was enhanced. By combining grain production, economy, population, and water resources with the center of gravity model, this paper reveals the spatial differences of relevant factors in the Tarim River Basin, providing an important reference value for regional socio-economic development and the rational allocation of water resources.

Growth Stages and Inter-Species Gut Microbiota Composition and Function in Captive Red Deer (Cervus elaphus alxaicus) and Blue Sheep (Pseudois nayaur)

Blue sheep and red deer, second-class key protected animals in China, are sympatric species with a high degree of overlap of food resources in the Helan Mountains, China. Previous studies with blue sheep and red deer in nature have shown that their physiology is closely related to their gut microbiota. However, growth stages and changes occurring in these species in captivity are still unknown. Thus, 16S rRNA gene sequencing was used to explore diversity, composition and function of the gut microbiota in these two animal species. The diversity and structure of the gut microbiota in captive blue sheep and red deer changed at different growth stages, but the dominant microbiota phyla in the gut microbiota remained stable, which was composed of the phyla Firmicutes, Bacteroidetes and Verrucomicrobia. Moreover, gut microbiota diversity in juvenile blue sheep and red deer was low, with the potential for further colonization. Functional predictions showed differences such as red deer transcription being enriched in adults, and blue sheep adults having a higher cell wall/membrane/envelope biogenesis than juveniles. Microbial changes between blue sheep and red deer at different growth stages and between species mainly depend on the abundance of the microbiota, rather than the increase and absence of the bacterial taxa.

Habitat Usage, Dietary Niche Overlap, and Potential Partitioning between the Endangered Spotted Turtle (Clemmys guttata) and Other Turtle Species

Habitat loss and degradation affect populations in isolation while also modifying the intensity of interspecific interactions, which may be especially relevant for species of conservation concern coexisting with more common species. We explored habitat preferences and potential interspecific resource competition in the endangered Spotted Turtle (Clemmys guttata). For habitat data, water quality measurements were recorded once per trapping session, while canopy cover and vegetation data were recorded once per field season. We also investigated niche overlap in habitat and food resources between C. guttata and other, more common, turtle species. Our data indicated that the abundance of C. guttata was negatively correlated with dissolved O2 and pH levels and positively correlated with body of water depth and canopy cover. The investigation of niche overlap revealed that Mud Turtles (Kinosternon subrubrum) and Painted Turtles (Chrysemys picta), but not Snapping Turtles (Chelydra serpentina), were negatively correlated with the abundance of C. guttata despite differences in characteristics of bodies of water used by each species. We used structural equation modeling to better understand if the relationships between C. guttata and other turtles were due to direct interactions or simply reflected environmental influences. We then used stable isotope analyses to compare similarities in δ13C and δ15N isotopes as proxies for diet overlap between C. guttata and other turtles and ultimately found that all species had similar, broad diets. The inverse relationship between abundance of C. guttata and other species, paired with the overlap in dietary niche space, suggests there is potential for interspecific interactions to negatively impact the abundance of C. guttata within turtle communities on the Atlantic Coastal Plain. The results of this study highlight that management efforts may need to consider that species of conservation concern coexist with more common species, especially as habitat loss decreases the breadth of habitat available.

Diet composition and resource overlap of sympatric native and introduced salmonids across neighboring streams during a peak discharge event.

Species assemblages composed of non-native and native fishes are found in freshwater systems throughout the world, and interactions such as interspecific competition that may negatively affect native species are expected when non-native species are present. In the Smith River watershed, Montana, rainbow trout were introduced by 1930. Native mountain whitefish and non-native rainbow trout have presumably occurred in sympatry since the introduction of rainbow trout; however, knowledge about how these two species compete with one another for food resources is sparse. We quantified diet compositions of rainbow trout and mountain whitefish in the mainstem Smith River and in a tributary to the Smith River-Sheep Creek-to determine the degree of overlap in the diets of mountain whitefish and rainbow trout in the Smith River and between the mainstem Smith River and a tributary stream. Rainbow trout and mountain whitefish had generalist feeding strategies, which probably contribute to the amicable coexistence of these species. Diet overlap between rainbow trout and mountain whitefish was high (Pianka's index value = 0.85) in the Smith River and moderate in Sheep Creek (Pianka's index value = 0.57). Despite overlap in diets, some resource partitioning may alleviate resource competition (e.g., rainbow trout consumed far more Oligochaeta than mountain whitefish but fewer Brachycentridae and Chironomidae). Diet composition of rainbow trout and mountain whitefish did not differ greatly between the Smith River and Sheep Creek. Prey categories most commonly used by mountain whitefish at the population and individual levels (i.e., Ephemeroptera and Trichoptera) are sensitive taxa and many species within these orders have experienced extinctions and population declines. Therefore, future changes in resource availability or competition could be of concern.

Establishment of a dermatology clinic serving both patients living with HIV/AIDS and transgender individuals (PRIDE clinic) in an urban academic setting: Demographics, evolution, and lessons learned

To the Editor: Given structural barriers, marginalized populations, including LGBTQ+ individuals and people living with HIV, deserve improved care access. 1 Gonzales G. Przedworski J. Henning-Smith C. Comparison of health and health risk factors between lesbian, gay, and bisexual adults and heterosexual adults in the United States: results from the National Health Interview Survey. JAMA Intern Med. 2016; 176: 1344-1351https://doi.org/10.1001/jamainternmed.2016.3432 Crossref PubMed Scopus (224) Google Scholar , 2 Reisner S.L. Poteat T. Keatley J. et al. Global health burden and needs of transgender populations: a review. Lancet. 2016; 388: 412-436https://doi.org/10.1016/S0140-6736(16)00684-X Abstract Full Text Full Text PDF PubMed Scopus (558) Google Scholar , 3 Geter A. Herron A.R. Sutton M.Y. HIV-related stigma by healthcare providers in the United States: a systematic review. AIDS Patient Care STDS. 2018; 32: 418-424https://doi.org/10.1089/apc.2018.0114 Crossref PubMed Scopus (85) Google Scholar , 4 Yeung H. Luk K.M. Chen S.C. Ginsberg B.A. Katz K.A. Dermatologic care for lesbian, gay, bisexual, and transgender persons: epidemiology, screening, and disease prevention. J Am Acad Dermatol. 2019; 80: 591-602https://doi.org/10.1016/j.jaad.2018.02.045 Abstract Full Text Full Text PDF PubMed Scopus (34) Google Scholar In 2014, we started monthly clinics within normal operations and clinic hours to serve patients living with HIV and associated dermatologic manifestations. These sessions were established as entry points to the system, to expedite access for new patients within 1 month of request, referred by partner clinic providers. Over time, a second population emerged from the same partner clinics: transgender and non-binary patients. The clinic slowly pivoted and rebranded to serve both communities: those living with HIV and transgender and non-binary patients. Importantly, these communities are distinct but show overlap in both population and resources used. 5 Becasen J.S. Denard C.L. Mullins et al. Estimating the prevalence of HIV and sexual behaviors among the US transgender population: a systematic review and meta-analysis, 2006–2017. Am J Public Health. 2019; 109: e1-e8https://doi.org/10.2105/ajph.2018.304727 Crossref PubMed Scopus (0) Google Scholar In 2020, the clinic was officially named PRoviding Integrated Dermatology for Everyone (PRIDE).

Seasonality can affect ecological interactions between fishes of different thermal guilds

Seasonality could play a crucial role in structuring species interactions. For example, many ectotherms alter their activity, habitat, and diet in response to seasonal temperature variation. Species also vary widely in physiological traits, like thermal preference, which may mediate their response to seasonal variation. How behavioral responses to seasonality differ between competing species and alter their overlap along multiple niche axes in space and time, remains understudied. Here, we used bulk carbon and nitrogen stable isotopes combined with stomach content analysis to determine the seasonal diet overlap between a native cold-water species [lake trout (Salvelinus namaycush)] and a range-expanding warm-water species [smallmouth bass (Micropterus dolomieu)] in two north-temperate lakes over 2 years. We coupled these analyses with fine-scale acoustic telemetry from one of the lakes to determine seasonal overlap in habitat use and activity levels. We found that dietary niche overlap was higher in the spring, when both species were active and using more littoral resources, compared to the summer, when the cold-water lake trout increased their reliance on pelagic resources. Telemetry data revealed that activity rates diverged in the winter, when lake trout remained active, but the warm-water smallmouth bass reduced their activity. Combining stable isotopes and stomach contents with acoustic telemetry was a powerful approach for demonstrating that species interactions are temporally and spatially dynamic. In our case, the study species diverged in their diet, habitat, and activity more strongly during certain times of the year than others, in ways that were consistent with their thermal preferences. Despite large differences in thermal preference, however, there were times of year when both species were active and sharing a common habitat and prey source (i.e., resource overlap was greater in spring than summer). Based on our findings, important ecological processes are occurring during all seasons, which would be missed by summer sampling alone. Our study stresses that quantifying multiple niche axes in both space and time is important for understanding the possible outcomes of altered seasonal conditions, including shorter winters, already arising under a changing climate.

Population dynamics and resource availability drive seasonal shifts in the consumptive and competitive impacts of introduced house mice (Mus musculus) on an island ecosystem.

BackgroundHouse mice (Mus musculus) are widespread and invasive on many islands where they can have both direct and indirect impacts on native ecological communities. Given their opportunistic, omnivorous nature the consumptive and competitive impacts of house mice on islands have the potential to vary over time in concert with resource availability and mouse population dynamics.MethodsWe examined the ecological niche of invasive house mice on Southeast Farallon Island, California, USA using a combination of mouse trapping, food resource surveys, and stable isotope analysis to better understand their trophic interactions with native flora and fauna. Specifically, we coupled the analysis of seasonal variation in resource availability over a 17-year period (2001–2017), carbon (δ13C) and nitrogen (δ15N) stable isotope values of mouse tissue and prey resources in a single year (2013), and isotopic niche and mixing models to quantify seasonal variation in mouse diets and the potential for resource overlap with native species.ResultsWe found that plants were the most important resource for house mice during the spring months when vegetation is abundant and mouse populations are low following heavy precipitation and declines in mouse abundance during the winter. While still consumed, plants declined in dietary importance throughout the summer and fall as mouse populations increased, and seabird and arthropod resources became relatively more available and consumed by house mice. Mouse abundance peaks and other resource availability are low on the island in the fall months when the isotopic niches of house mice and salamanders overlap significantly indicating the potential for competition, most likely for arthropod prey.DiscussionOur results indicate how seasonal shifts in both mouse abundance and resource availability are key factors that mediate the consumptive and competitive impacts of introduced house mice on this island ecosystem. As mice consume and/or compete with a wide range of native taxa, eradication has the potential to provide wide-reaching restoration benefits on Southeast Farallon Island. Post-eradication monitoring focused on plant, terrestrial invertebrate, salamander, and seabird populations will be crucial to confirm these predictions.

Reef fishes weaken dietary preferences after coral mortality, altering resource overlap.

The direct and indirect effects of climate change can affect, and are mediated by, changes in animal behaviour. However, we often lack sufficient empirical data to assess how large-scale disturbances affect the behaviour of individuals, which scales up to influence communities. Here, we investigate these patterns by focusing on the foraging behaviour of butterflyfishes, prominent coral-feeding fishes on coral reefs, before and after a mass coral bleaching event in Iriomote, Japan. In response to 65% coral mortality, coral-feeding fishes broadened their diets, showing a significant weakening of dietary preferences across species. Multiple species reduced their consumption of bleaching-sensitive Acropora corals, while expanding their diets to consume a variety of other coral genera. This resulted in decreased dietary overlap among butterflyfishes. Behavioural changes in response to bleaching may increase resilience of coral reef fishes in the short term. However, coral mortality has reduced populations of coral-feeders world-wide, indicating the changes in feeding behaviour we document here may not be sufficient to ensure long-term resilience of butterflyfishes on coral reefs.