Ecology最新文献

Species interactions shape biodiversity patterns, community assemblage, and the dynamics of wildlife populations. Ecological theory posits that the strength of interspecific interactions is fundamentally underpinned by the population sizes of the involved species. Nonetheless, prevalent approaches for modeling species interactions predominantly center around occupancy states. Here, we use simulations to illuminate the inadequacies of modeling species interactions solely as a function of occupancy, as is common practice in ecology. We demonstrate erroneous inference into species interactions due to error in parameter estimates when considering species occupancy alone. To address this critical issue, we propose, develop, and demonstrate an abundance-mediated interaction framework designed explicitly for modeling species interactions involving two or more species from detection/non-detection data. We present Markov chain Monte Carlo (MCMC) samplers tailored for diverse ecological scenarios, including intraguild predation, disease- or predator-mediated competition, and trophic cascades. Illustrating the practical implications of our approach, we compare inference from modeling the interactions in a three-species network involving coyotes (Canis latrans), fishers (Pekania pennanti), and American marten (Martes americana) in North America as a function of occupancy states and as a function of abundance. When modeling interactions as a function of abundance rather than occupancy, we uncover previously unidentified interactions. Our study emphasizes that accounting for abundance-mediated interactions rather than simple co-occurrence patterns can fundamentally alter our comprehension of system dynamics. Through an empirical case study and comprehensive simulations, we demonstrate the importance of accounting for abundance when modeling species interactions, and we present a statistical framework equipped with MCMC samplers to achieve this paradigm shift in ecological research.

Young tropical secondary forests play an important role in the local and global carbon cycles because of their large area and rapid biomass accumulation rates. This study examines how environmental conditions and forest attributes shape biomass compartments and the productivity of young tropical secondary forests. We compared 36 young secondary forest stands that differed in the time since agricultural land abandonment (2.3–3.6 years) from dry and wet regions in Ghana. We quantified biomass stocks in living and dead stems, roots, and soil, and aboveground biomass and litter productivity. We used structural equation models to evaluate how macroclimate, soil nutrients (N, P), and forest attributes (structure, diversity, and functional composition) affect ecosystem functioning. After three years of succession, tropical wet forests stored on average 115 t biomass ha⁻¹ (the sum of aboveground living and dead biomass, belowground fine root biomass, and soil organic matter), and dry forests stored 99 t ha⁻¹. These values represent 31% (in the wet forest) and 39% (in the dry forest) of the biomass compared with neighboring old-growth forests. The majority of forest ecosystem biomass was stored in the soil (70%) and aboveground living vegetation (25%). Macroclimate strongly shaped forest attributes, which in turn determined biomass stocks and productivity. Soil phosphorus strongly increased litter production and soil organic matter, confirming that it is a limiting element in tropical ecosystems. Tree density and species diversity increased forest biomass stocks, suggesting crown packing and complementary resource use enhance forest functioning. A more conservative trait composition (high wood density) increased biomass stocks but reduced productivity, indicating that quantity, identity, and quality of species affect ecosystem functioning.

Although invertebrate herbivores commonly impact terrestrial plant diseases by facilitating transmission of plant pathogens and increasing host susceptibility to infection via wounding, less is known about the role of herbivores in marine plant disease dynamics. Importantly, transmission via herbivores may not be required in the ocean since saline ocean waters support pathogen survival and transmission. Through laboratory experiments with eelgrass (Zostera marina), we showed that isopods (Pentidotea wosnesenskii) and snails (Lacuna spp.) created grazing scars that increased disease severity and thus indirectly facilitated transmission of Labyrinthula zosterae (Lz), a protist that causes seagrass wasting disease. Experiments also quantified different feeding preferences among herbivores: Amphipods (Ampithoe lacertosa) selectively consumed diseased eelgrass, while isopods and snails selectively grazed asymptomatic leaves, suggesting different herbivore taxa may have contrasting impacts on disease dynamics. Our experiments show no sign that herbivores directly vector Lz from diseased to asymptomatic eelgrass. However, we isolated live Lz from isopod, amphipod, and snail feces and detected Lz with quantitative polymerase chain reaction in amphipods and snails, suggesting that herbivores eating diseased eelgrass could pass the live pathogen. Finally, field surveys demonstrated a close association between seagrass wasting disease and invertebrate grazing scars; disease prevalence was 29 ± 4.7% (95% CI) higher on eelgrass leaves with herbivore scars. Collectively, these findings show that some herbivores can increase eelgrass disease risk by facilitating the spread of an important pathogen via wounding, but not via direct transmission. Thus, herbivores may play different roles in plant disease dynamics in terrestrial versus marine ecosystems depending on the pathogen's ability to survive and transmit without a vector.

Two hypotheses have been used to explain the loss of plant diversity with nutrient addition. The nutrient identity hypothesis posits that biodiversity loss is due to a specific limiting nutrient, such as nitrogen (N) or phosphorus (P), while the niche dimension hypothesis posits that adding a larger number of limiting nutrients, regardless of their identity, results in biodiversity loss. These two hypotheses have not previously been tested together simultaneously. Here, we conduct that analysis to enable their relative effect sizes to be compared. We manipulated the supply of eight nutrients in the same experimental meadow grassland site to isolate the effects of the identity of added nutrients versus the number of added nutrients on biodiversity loss. We found support for both hypotheses, with the largest negative effects on biodiversity measures being due to N, or N and P treatment, with additional more minor effects of the number of added nutrients. Structural equation models (SEMs) suggested both identity and number of added nutrients had direct negative effects on biodiversity, likely caused by species' innate ability to competitively respond to nutrients, especially in response to disease, herbivory, and stress. SEMs also suggested indirect effects arising from nutrient-driven increases in aboveground biomass, which resulted in intensified competition for light and the competitive exclusion of short-statured species. These effects were exacerbated by the nutrients N and P which caused a shift in biomass accumulation from belowground to aboveground. The results highlight that a multi-nutrient perspective will improve our ability to effectively manage, monitor, and restore ecosystems.

Diel partitioning of animals within ecological communities is widely acknowledged, yet rarely quantified. Investigation of most ecological patterns and processes involves convenient daylight sampling, with little consideration of the contributions of nocturnal taxa, particularly in marine environments. Here we assess diel partitioning of reef faunal assemblages at a continental scale utilizing paired day and night visual census across 54 shallow tropical and temperate reefs around Australia. Day–night differences were most pronounced in the tropics, with fishes and invertebrates displaying distinct and opposing diel occupancy on coral reefs. Tropical reefs in daytime were occupied primarily by fishes not observed at night (64% of all species sighted across day and night, and 71% of all individuals). By night, substantial emergence of invertebrates not otherwise detected during sunlit hours occurred (56% of all species, and 45% of individuals). Nocturnal emergence of tropical invertebrates corresponded with significant declines in the richness and biomass of predatory and herbivorous diurnal fishes. In contrast, relatively small diel changes in fishes active on temperate reefs corresponded to limited nocturnal emergence of temperate invertebrates. This reduced partitioning may, at least in part, be a result of strong top-down pressures from fishes on invertebrate communities, either by predation or competitive interference. For shallow reefs, the diel cycle triggers distinct emergence and retreat of faunal assemblages and associated trophic patterns and processes, which otherwise go unnoticed during hours of regular scientific monitoring. Improved understanding of reef ecology, and management of reef ecosystems, requires greater consideration of nocturnal interactions. Without explicit sampling of nocturnal patterns and processes, we may be missing up to half of the story when assessing ecological interactions.

As long-lived tropical trees grow into the multi-layered canopy and face different environmental conditions, the relationships between leaf traits and whole-plant survival can vary over ontogeny. We tested the strength and direction of the relationships between leaf traits and long-term survival data across life stages for woody species from a subtropical forest in Puerto Rico. Trait–survival relationships were largely consistent across ontogeny with conservative traits leading to higher survival rates. The stage-specific relationship R² increased by up to one order of magnitude compared to studies not considering ontogenetic trait variations. Stage-specific traits were significant predictors of their corresponding stage-specific survival: Seedlings traits were better predictors of seedling survival than adult traits, and adult traits were better predictors of maximum adult survival than seedling traits. Our results suggest that stage-specific leaf traits reflect different strategies over ontogeny and can substantially improve predictability of survival models in tropical forests.

Urbanization in temperate climates often advances the beginning and peak of biological events due to multiple factors, especially urban heat islands. However, the effect of urbanization on insect phenology remains understudied in more tropical areas, where temperature may be a weaker phenological cue. We surveyed moths across an urban gradient in a subtropical city weekly for a year to test how impervious surface and canopy cover impact phenology at the caterpillar and adult life stages. For macro-moths, we also examine how these effects vary with life history traits. When pooling all individuals, we found no effect of urbanization proxy variables on timing of caterpillar or adult phenology. At the species-specific level, we found timing of peak adult macro-moths is influenced by canopy cover, which also interacts with two traits: temperature niche and body size. Cold-adapted species delay timing of peak abundance in more shaded sites, while warm-adapted species were not affected. Smaller species, associated with lower dispersal ability, were more phenologically sensitive to canopy cover than larger bodied species. These results highlight the importance of canopy cover within cities and its interaction with species' traits in mediating impact of urbanization on moth phenology in subtropical systems.

Substantial evidence suggests that biodiversity can stabilize ecosystem function, but how it does this is less clear. In very general terms, the hypothesis is that biodiversity stabilizes function because having more species increases the role of compensatory dynamics, which occur when species in a community show different responses to the environment. Here, we focus on two forms of compensatory dynamics, cross-scale redundancy (CSR) and response diversity (RD). CSR occurs when species respond to a disturbance at different scales such that scale-specific disturbances do not negatively affect all species. RD occurs when species contributing to the same function show different responses to an environmental change. We developed a new analytical approach that can compare the strength of CSR and RD in the same dataset and used it to study native bee pollination of blueberry at 16 farms that varied in surrounding agricultural land use. We then asked whether CSR and RD among bee species are associated with the stability of blueberry pollination. Although CSR and RD were both present, only RD was associated with higher stability of pollination. Furthermore, the effects of RD on stability were due to a single widespread species, Andrena bradleyi, that is a specialist on blueberry and, unlike other bee species, was highly abundant at farms surrounded by intensive blueberry agriculture. Thus, the stabilizing effect we observed was attributable to an “identity effect” more than to species richness per se. Our results demonstrate how CSR and RD can be empirically measured and compared and highlight how the theoretical expectations of the biodiversity–ecosystem functioning field are not always upheld when confronted with real-world data.