Herbivory is a fundamental biological process that can determine the structure and functioning of ecosystems. On temperate reefs worldwide, herbivory by grazing macro-invertebrates can cause extensive overgrazing of kelp beds when grazers reach hyperabundance. Rising to local dominance, typically it is the grazing activity of a single species amongst others that is responsible for overgrazed ‘barrens’. However, the potential for subordinate grazing species to impact kelp beds is less understood and often overlooked. Here we observe apparent ‘barren’ patches within kelp beds associated with local hyperabundance of a subordinate grazer, the turbinid periwinkle Lunella undulata, in eastern Tasmania. We demonstrate capacity for this periwinkle to overgraze by deploying a caging experiment on a ‘peri-barren’ patch, involving inclusion and exclusion treatments, plus cage and background control plots. Fleshy macroalgae proliferated in cages excluding periwinkles, reaching mean percentage cover of 47 ± 8
Phylogenetic distance between exotic and native plant species is a well documented predictor of insect herbivory, but whether it also influences predator-mediated (top-down) control remains unresolved. In this study, we manipulated predator access on 18 exotic oak (Quercus) species grown in a common garden, spanning a gradient of phylogenetic distance to four european oaks (Q. robur, Q. petraea, Q. suber, or Q. pyrenaica). We excluded three predator guild treatments: ground-dwelling arthropod predators (hereafter ant exclusion, because the sticky-barrier method used primarily excludes ants), vertebrate predators (mainly birds), and both predator groups combined. We quantified cumulative leaf herbivory and plant chemical traits (volatile organic compounds and phenolics). Under ambient predator access, herbivory declined with increasing phylogenetic distance from native oaks (r = − 0.49, P = 0.038), consistent with previous work in this system. This relationship disappeared following ant exclusion (r = − 0.08, P = 0.76), and a phylogenetic generalized least-squares model detected a significant treatment × phylogenetic distance interaction (F = 2.96, P = 0.033) that remained robust after accounting for phylogenetic non-independence among species (phylogenetic regression slope, P = 0.001). Excluding vertebrate predators increased herbivory consistently across the phylogenetic gradient. Total VOC emissions and phenolic concentrations were unrelated to phylogenetic distance; however, multivariate VOC composition diverged with phylogenetic distance (Mantel r = 0.26, P = 0.049), unlike phenolic composition (P = 0.62). These results indicate that ant-mediated predation, not bulk chemical defences, underlies the phylogenetic herbivory pattern, highlighting predator identity as an underappreciated axis of plant–herbivore–predator interactions in novel communities.
Cities and suburbs frequently plant native and non-native trees as foundation species, with non-natives cultivated in these areas for centuries while remaining non-invasive. Although previous research has found that native trees often host more arthropods, studies have not simultaneously looked across space and time to determine the consistency of tree origin on urban arthropods. We combined varied methods across spatial and temporal scales in New York City to test if native tree leaves consistently have more insect and mite interactions than long-established non-native trees, predicting stronger effect sizes for specialists (galling arthropods) than generalists (herbivory). We examined (1) congeneric species pairs, controlled for growing conditions and stoichiometry in an arboretum, (2) diverse oaks at a botanical garden, (3) community science records across Brooklyn, and (4) herbarium specimens from 1883 through present across the city. Across spatiotemporal scales, we found consistent results. Specialist interactions were striking: contemporary native trees supported numerous galling species, while only one congeneric non-native species hosted any galls. For generalists, contemporary native trees had equivalent to slightly greater herbivory. Over the last century, herbarium records showed that herbivory increased on non-native trees to nearly the level of natives, whereas native trees increased in gall abundance while non-native trees remained rarely galled. Our results demonstrate the impact of tree origin on tree-arthropod interactions in a real-world urban setting, with far fewer galls even when non-native tree species have been cultivated locally for centuries. Our findings will help city planners and property owners confidently choose native trees to promote arthropod biodiversity.
Measuring growth dynamics has been fundamental to understanding lichen biology and ecology. In this integrative analysis, I synthesize and reanalyze published data on three-dimensional growth in the foliose cephalolichen Lobaria pulmonaria transplanted in pristine North American forests, encompassing thallus area expansion, biomass accumulation, thallus thickening, and reproductive investment across multiple environmental gradients. Best subset regression selection and linear mixed models were applied to identify the principal internal and external factors influencing growth, specifically thallus area expansion and thickening, quantified as increases in specific thallus mass. The analyses reveal pronounced intrathalline growth heterogeneity, significant trade-offs between reproductive investment and growth, and the multifactorial influences of bark pH, elevation, light regime, and phosphorus availability. Light was often a limiting growth factor within forest interiors, whereas excessive stand openness caused chlorophyll bleaching and reduced growth. Initial phosphorus enrichment enhanced thallus thickness but did not consistently promote area or biomass expansion. Taken together, these finding highlight the habitat specialization of L. pulmonaria and the importance of bark pH, light, hydration, and reproductive investment in shaping growth dynamics. The study advances the understanding of growth strategies in L. pulmonaria and provides a foundation for predicting responses to environmental change and guiding conservation efforts.
Plant phenology is a key determinant of the productivity and trophic dynamics of tropical forests, yet the multi-scale variance structure and inter-annual consistency of community-level phenological patterns in perhumid systems remain poorly characterized. We analyzed 10 years of weekly phenological recordings from 480 trees across 20 transects in a perhumid forest fragment at Los Tuxtlas (Mexico), characterizing the seasonal patterns, multi-scale variance structure, inter-annual consistency, and temporal covariation of five phenophases: young leaves, mature leaves, unripe fruits, ripe fruits, and flowers. All phenophases deviated significantly from uniform annual distributions (Rayleigh test, all p < 0.05), with flowers showing the highest seasonal concentration (mean vector length r = 0.52, Fourier peak April, R2 = 0.93) and mature leaves the lowest (r = 0.08). Mixed-effects variance partitioning revealed that month-within-year (seasonal) variance dominated total phenological variation across all phenophases, while between-year variance was negligible for four of five phenophases and significant only for mature leaves (18.0
Controversy over whether coral reef sponges are controlled bottom-up or top-down has distracted attention from more nuanced questions about what circumstances promote either bottom-up or top-down control, and how coral reef ecosystems are affected by what controls their sponges. Experiments now suggest that predators do not control coral reef sponges in their home habitat, shifting attention to effects of variations in sponge food supply. Comparing growth and survival of eleven of the most common and ubiquitous Caribbean coral reef sponge species on reefs in Belize and Panama differing in water column richness revealed faster sponge growth (by factors of 1.79–3.22 depending on the species) in the more picoplankton/nutrient-rich water at the Panama site. This could: a) benefit reefs by increasing positive effects of sponges, or b) harm reefs by sponges overgrowing corals. ‘Sponges’ is not a homogeneous category, so the balance between benefit and harm to reefs by increases in ‘sponges’ depends on both the species involved and environmental context. Predictions are complicated because sponge responses to increased nutrients/picoplankton are not monotonic: moderate increases boost sponge growth rates, but very dense blooms can devastate reef sponge populations. The same sponge species which grew faster in a somewhat richer water column (2 times as much picoplankton) lost nearly 2/3 of their biomass during a dense (8 times denser than normal) cyanobacteria bloom on the Belize Barrier Reef, reducing their unique positive functional roles of promoting water column clarity, symbiont habitat, food for charismatic megafauna, coral survival, and reef regeneration.
Decomposition is the process by which dead plant biomass is recycled and made available again for uptake by other plants. It is largely mediated by microbes and soil invertebrates. Global decomposition studies have demonstrated that decomposition is primarily temperature-driven with rainfall playing a secondary role, although to date, all global decomposition studies have used a single substrate to measure decomposition meaning differences with substrate type may be missed. Here we explored the decomposition of wood, dung and grass along a semi-arid rainfall gradient (380–650 mm/year) at three savanna sites in north-eastern South Africa. As the three sites experience a similar temperature range, we effectively controlled for temperature allowing us to explore the effect of rainfall in isolation. We used decomposition bags - with and without termite access - and measured mass loss after set time intervals. We predicted that the absolute decomposition of all three substrates would increase along the rainfall gradient. This assumption held for dung and grass, but we found the reverse for wood. Our study highlights the importance of considering multiple substrates as decomposition patterns and dominant agents can vary. Unexpectedly low wood decomposition at our wettest site suggests that the amount of dead wood available, and therefore probability of discovery by termites, may be an important factor explaining findings from decomposition studies. Resource availability and termite discovery is a neglected subject within decomposition studies and warrants further investigation.
Ecosystem engineers influence abiotic and biotic properties of communities. However, environmental factors like stress or energy gradients could modify their influence. Furthermore, engineering effects include legacies that persist after the engineer’s death that may interact with gradients differently than the live engineer. Here, we show that live and legacy effects of the oyster Crassostrea virginica, a reef-building ecosystem engineer, act in opposing directions across a physical energy gradient, reversing oysters’ net engineering effect. When energy is low, live oysters primarily buffer erosional forces and increase habitat availability for cordgrass (Spartina alterniflora). When energy is high, legacy effects of oysters on cordgrass are negative, because high energy piles dead oyster shells onto cordgrass and smothers it. Thus, with increasing energy, net effects of engineering on cordgrass shift from positive live effects to negative legacy effects. Estuary wide, oysters have a net positive effect on cordgrass, because high energy coastlines – where negative effects predominate – are rare. Live and legacy engineering can have disparate, context-dependent effects; combined, they determine the overall effects of engineers on communities.
When and why embryos delay hatching in response to predation risk remains poorly understood, particularly across species experiencing different ecological contexts. Predator-induced hatching plasticity allows embryos to adjust hatching timing in response to predator cues, yet interspecific variation in delayed hatching has rarely been examined. Phytoseiid mites provide a useful system because delayed hatching can be induced by mechanical stimuli mimicking predator attacks, and predation risk from cannibalism and intraguild predation (IGP) in the vulnerable larval stage varies among species according to diet specialisation. We compared delayed hatching responses among four phytoseiid mite species differing in cannibalism and diet specialisation by exposing eggs to mechanical stimulation and recording hatching timing with unstimulated controls. Mechanical stimulation induced stronger delayed hatching responses in Neoseiulus californicus (odds ratio = 5.73) and Neoseiulus cucumeris (odds ratio = 7.83), a weaker response in Phytoseiulus persimilis (odds ratio = 3.11), and no detectable response in Typhlodromus bambusae (odds ratio = 0.99). The magnitude of delayed hatching corresponded to interspecific differences in cannibalism and diet specialisation, suggesting that variation in predation risk associated with intraguild interactions shapes hatching timing strategies. These findings support the hypothesis that delayed hatching is an adaptive life-history response to intraguild predation risk and suggest that interspecific variation in hatching plasticity may have important consequences for predator community dynamics and the establishment success of biological control agents.
The senescence of productive leaves is expected to decrease canopy photosynthesis, but it may allow plants to use resorbed nitrogen for new growth. If plants use leaf senescence as part of a competitive strategy, we expect that leaves with low competitive value would be sacrificed to supply nitrogen to leaves with high competitive value. However, when plants have multiple branches, it is unclear if plants can target leaves in shaded conditions for senescence and whether they prioritize the growth of their shaded or unshaded branches. We measured changes in leaf nitrogen in sunflowers (Helianthus annuus) grown with two symmetrical branches that were then subjected to either shaded or unshaded light conditions. We complemented the experiment with a mathematical model of leaf senescence to test whether our proposed physiological mechanisms could explain the results. When both branches were grown in low light, leaf senescence was inhibited relative to plants with both branches grown in high light. For plants with one branch in high light and one branch in low light, the senescence of older leaves was inhibited in the high-light branch, but accelerated in the low-light branch. This was associated with an increase in the growth rate of the youngest leaves in the low-light branch. Our mathematical model reproduced these results, suggesting that leaf senescence may be mediated by the carbon status of the plant. The pattern of leaf senescence and growth in this experiment was consistent with a strategy that prioritizes competing with neighbors for light rather than avoiding competition.
Competition, lack of space, and prolonged environmental change can lead animals to build refuges in areas that are (or become) exposed or otherwise offer poor protection. This is especially problematic for species that invest heavily in refuge construction and reside in that refuge long-term. We examined the consequences of refuge position in an iconic central place forager, the Australian meat ant (Iridomyrmex purpureus). Colonies excavate massive ground nests out of soil and can remain in those nests for a decade or more. We monitored the external and internal temperature of nests for over two years. These data were combined with a phylogenetic analysis of optimal brood incubation temperatures compiled from the literature to infer the probable incubation temperature for this species. Focussing on summertime extremes, our field data across consecutive years showed the spatial position of meat ant nests had critical impacts on the internal conditions of nests. In most instances, colonies would probably be able to protect broods by actively moving broods to different depths within the nest. However, this thermoregulation would unlikely fully compensate for the extreme temperatures experienced by the most exposed nest in our study. This exposed nest has in turn suffered a sustained decline in colony size over the last decade. Even for a central place forager believed to be resilient to environmental degradation, refuges could not protect against prolonged environmental change, with likely tangible impacts on fitness.
Vachellia tortilis (Forssk.) Hayne subsp. raddiana (Savi) Brenan, a drought-resistant tree native to arid and semi-arid regions of Africa and the Middle East, plays a crucial ecological and socioeconomic role by providing shade, forage, fuelwood, and contributing to soil stabilization and desertification control. To support scientific site selection for artificial planting and assess its current and potential distribution, we used the MaxEnt model combined with ArcGIS to evaluate climatic suitability across Africa based on occurrence records and environmental variables. After ten iterations, the model achieved high predictive accuracy with training and test AUC values of 0.942. Eight key bioclimatic factors shaped the distribution, with Mean Temperature of the Coldest Quarter (32.1
Climate-driven environmental change can alter both the structural and dynamic properties of ecological communities. With ongoing warming, high-latitude lakes experience reduced ice cover, higher growing-season temperatures, and altered hydrology, potentially triggering cascading effects across lake ecosystems. We investigated long-term variation (1994–2022) in ice phenology, temperature, magnitude of spring floods, and pelagic communities in an oligotrophic subalpine lake in Norway. We analysed the structure and dynamics of phytoplankton, zooplankton, and fish communities, as well as synchrony across trophic groups. Long-term records indicated declining ice-cover duration and increasing growing-season temperatures, although only the reduction in ice-cover duration was significant within the 1994–2022 study period. Phytoplankton richness and biovolume increased, zooplankton communities increased in diversity but declined in temporal stability, and fish community structure changed, with brown trout becoming more abundant at the expense of arctic char. We also observed shifts in synchrony between trophic groups, suggesting changes not only in community organisation but potentially in interspecific interactions. Given the observational, correlative nature of the study, causal attribution remains limited. Although some biological metrics showed significant associations with climate-related variables, several metrics that changed over time were not related to the measured abiotic drivers, indicating partial coupling between environmental variability and community structure and dynamics. This limited coupling may reflect the relatively modest magnitude of environmental change that occurred over the study period. Overall, our results document cross-trophic restructuring of pelagic communities in a high-latitude oligotrophic lake and underscore the importance of long-term monitoring for documenting and anticipating future shifts.
Biodiversity decline alters species interaction networks and can destabilise ecosystem functions. Fungal consumption by mammals supports ectomycorrhizal (ECM) spore dispersal, contributing to fungi-plant symbioses. The ecological impacts of losing mycophagous mammals and to what extent species roles are redundant or complementary remains poorly quantified. Using fungal ITS2 metabarcoding, we explore the fungal community in scats of a translocated fungal generalist, the eastern barred bandicoot (Perameles gunnii), on Phillip and French Island in southeast Australia. We compare: (1) fungi in bandicoot scats and soil; (2) soil fungi, soil properties and vegetation to compare possible fungal availability across habitats; and (3) fungi within the scats of two sympatric mammals, an endemic fungal generalist (swamp wallaby, Wallabia bicolor, on Phillip Island) and fungal specialist (long-nosed potoroo, Potorous tridactylus trisulcatus, on French Island). We found diverging patterns between soil fungi and mammal diet; and between soil fungi, soil properties and vegetation across sites. On French Island, bandicoot and potoroo scats had similar ECM fungal richness, although community composition differed, with less ECM observed in soils. On Phillip Island, only one scat from the wallaby contained ECM fungi, while soils were more ECM diverse than bandicoot scat. Our findings suggest the functional roles of mycophages should not be considered interchangeable across ecosystems. Translocated bandicoots may have the capacity to perform functionally unique roles compared to resident mycophages, highlighting that translocations could provide multiple ecosystem benefit. Adequately assessing functional redundancy or complementarity requires a site-specific characterisation and comparison of the cumulative roles of co-occurring mycophagous mammals.
Physiological traits related to water status and photosynthesis biophysically link plant performance to environmental conditions like light and water availability. By approaching the concept of species’ niches from a trait-based perspective, physiological traits can be used to characterize how trait syndromes diverge to limit direct resource competition and promote resource partitioning in sympatric species. Such traits could also inform broader studies of changing community composition in an era of drastic shifts in climate or disturbance regimes. However, the extent of inter/intraspecies trait variation and how such traits vary along local environmental gradients remains an open question in understanding physiological traits as species-level characteristics. To address this, we quantified hydraulic and gas exchange traits in four co-occurring Viburnum species while also quantifying local canopy coverage and soil conditions. All species displayed significant variation in gas-exchange traits, turgor loss point, and heavy carbon isotope discrimination along gradients of canopy openness. Specifically, plants in shadier environments exhibited higher photosynthetic rates at low light levels while individuals growing in gaps demonstrated higher drought tolerance and stricter stomatal regulation. Soil texture explained little variation in traits assessed. V. acerifolium displayed a more conservative, shade-tolerant trait syndrome, yet little significant difference was found in traits between the congeners, highlighting the potentially limited resolution of physiological traits to differentiate trait syndromes of closely related, co-occurring species.
Pollinator-mediated interactions shape the assembly and diversity of plant communities reliant on animal pollination. Such interactions can provide rare species with fitness advantages through facilitation while increasing intraspecific competition among abundant species. However, the roles of pollination generalisation and pollinator sharing in these dynamics remain unclear. To address this, we examined how plant rarity and pollination niche structure (breadth and overlap) influence pollination outcomes across 44 co-flowering species in Qinghai–Tibetan alpine grasslands. We measured plant abundance, floral traits, pollinator visitation, stigmatic pollen deposition, and seed production. Our results showed that rarer species exhibited broader pollination niches and greater niche overlap with co-flowering species, both associated with higher visitation and increased pollination outcomes. Pollination niche overlap, enhanced by greater floral trait similarity, emerged as a key mechanism promoting the persistence of rarer species through pollinator-mediated facilitation. Furthermore, asymmetric facilitation allowed rarer species to gain disproportionate conspecific pollen while abundant species experienced stronger intraspecific competition. Together, these results show that trait-mediated pollinator sharing enhances the persistence of rare species in pollinator-limited ecosystems and contributes to the maintenance of plant diversity.
A key assumption of the ideal free distribution theory is that animals select resources based on environmental cues that maximize fitness, thereby facilitating natural selection within a population. Habitat management and conservation practices are commonly based on results of resource selection models with the assumption that selection and fitness are correlated. This is concerning given that this critical assumption has been demonstrably violated in certain systems, where animals select resources that ultimately reduce vital rates. We studied how nocturnal habitat selection of 6 common landcover types influenced survival rates of Northern Bobwhite (Colinus virginianus) on public lands in southern Indiana, USA during the non-breeding season. We found that selection for woody cover had a positive effect on survival rates. Our results suggest that ideal free distribution is facilitated in this system by minimizing predation risk through the use of woody roosting cover. To develop more comprehensive knowledge on habitat selection for species, studies should examine the effects that selection has on one or more vital rates.
Predator-prey interactions are key to regulating lower trophic levels and stabilizing ecosystem processes. Therefore, understanding prey selection and prey composition of predators is essential, yet especially the small size and diverse diets of predatory arthropods present a significant challenge to conventional field methods. Here, we employed DNA metabarcoding on gut contents of over 1500 arboreal spiders in a subtropical forest in China to construct a high-resolution spider-prey interaction network. Subsequently, we compared prey diversity, composition, starvation rates, and network metrics (predator niche overlap, generality, and prey vulnerability) across different spider hunting guilds and families. Our results revealed an exceptionally broad diet for these spiders, with spiders themselves constituting a significant proportion of prey (i.e. spider on spider predation), besides a wide range of insects, particularly flies and moths. Although, prey composition was broadly similar at high taxonomic levels and functional groups, distinct dietary partitioning was evident at lower (MOTU) taxonomic level. Interaction networks revealed a broader and more generalized diet spectrum of active-hunters compared to web-builders, which resulted in higher diet overlap within the hunting guild (high prey vulnerability and niche overlap). However, network metrics for active hunters were lower than null expectations, suggesting a structuring role of intraspecific competition, while web-builders displayed greater random associations, possibly reflective of the passive mode of prey capture. Collectively, our study offers a high-resolution overview of the dietary niches of subtropical arboreal spiders, revealing how hunting mode shapes their ecological impact and providing significant implications for leveraging these predators in biological control strategies.
The decisions and conditions of animals often carry over to influence fitness in subsequent seasons or years. The condition, choices, and behaviors of parents may have a huge influence on offspring survival, not only when they are nutritionally dependent (i.e., pre-weaning or pre-fledgling), but also after they have reached independence but before adulthood (i.e., post-weaning or post-fledgling). Using a long-lived, iteroparous mammal, we evaluated the hypothesis that carryover effects of a mother's condition (i.e., age and nutritional condition) and her behavior and decisions during the first few months of her offspring's life will influence survival of juvenile deer after they reach nutritional independence-during their first migration and their first winter. Age of a mother and mass of her neonates at birth influenced if her offspring survived their first winter; mothers who were young or had high body fat produced offspring that were more likely to survive winter. Moreover, mothers could improve overwinter survival of their offspring by delaying the initiation of their autumn migration. Internal characteristics (i.e., body fat and age) and decisions of parents during their offspring's first year of life carried over to influence survival of those juveniles after they become nutritionally independent. Juvenile animals still carry the costs and face the consequences of their mother's decisions well into the period of their independence. The influence of parental characteristics on offspring survival once independent demonstrates the importance of considering how environmental and behavioral characteristics influence survival across generations.
Far-red (FR) light (700–750 nm) is strongly enriched beneath forest canopies, but its impact on photosynthesis in shade-adapted lichens is not well understood. We investigated the role of FR light in photosynthesis of Lobaria pulmonaria, an oldforest cephalolichen. Spectral measurements showed that FR photons contributed up to 32
