Ecosphere最新文献

Alternative ecological theories make divergent predictions about the relationship between predators and their prey. If predators exert top-down ecosystem control, increases in predation should diminish prey abundance and could either diminish or enhance community diversity of prey species. However, if bottom-up ecosystem controls predominate, predator populations should track underlying variation in prey diversity and abundance, which ultimately should reflect available energy. Past research, both across islands and comparing islands with the mainland, has frequently invoked the importance of predation in regulating lizard abundance and diversity, suggesting an important role of top-down control when predators are present. However, others have posited a stronger role of food limitation, via competition or bottom-up forces. If top-down control predominates, then negative correlations between prey abundance and predator occurrence should emerge within and among islands. Using data from eBird, we inferred landscape-level presence data for bird species on the islands of Jamaica and Hispaniola. By summing occurrence probabilities of all known anole-predator birds, we estimated total avian predation pressure and combined these estimates with anole community data from a mark-recapture study that spanned spatial and climatic gradients on both islands. Avian predators and anole lizards were both affected by climate, with total predator occurrence, anole abundance and anole species richness increasing with mean annual temperature. Anole abundance and predator occurrence showed a curvilinear relationship, where abundance and predator occurrence increased together until predator occurrence became sufficiently high that anole abundance was negatively impacted. This indicates that bottom-up ecosystem controls drive richness of both anoles and their predators, mitigating the negative effects predators might have on their prey, at least until predator occurrence reaches a threshold. We did not detect consistent evidence of predator occurrence reducing anole community richness. These findings support past research showing that islands with more predators tend to have lower prey abundances, but it does not seem that these top-down forces are strongly limiting species coexistence. Instead, bottom-up forces linked with climate may be more important drivers of diversity in both lizards and their avian predators on these islands.

Biological assessments typically involve field surveys that are time-consuming and require taxonomic expertise. Floristic Quality Assessment, a popular bioassessment method for wetlands and other ecosystems, generally assumes a comprehensive or representative species list for accurate implementation. We explored this long-held belief by analyzing an essential floristic quality metric (mean conservatism) across real and simulated gradients of species representation in two disparate case studies. In one study, we incrementally removed species at random from an exhaustive floristic survey of a suburban wetland complex in northeast Ohio. Bootstrapping mean conservatism at each removal step, precision scarcely decreased with 10%–30% species loss, becoming noticeable only when about 50% or fewer species remained. For the other study, we exploited varying percentages of dominant species available from hundreds of single-visit wetland determination surveys throughout Illinois. Comparing dominants-only mean conservatism with total species mean conservatism, the relationship steadily improved as dominants covered progressively larger fractions of native richness, ranging from r² = 0.12 at ≤10% dominants to 0.74 at >40% dominants. Both exercises suggest that community size is more important than taxonomic representation or inventory completeness per se in determining accuracy. Our results indicate that full or representative checklists are not a prerequisite for reliable Floristic Quality Assessment, supporting the investigation and potential use of taxonomic shortcuts and empowering a wide range of users beyond expert field botanists.

In recent decades, research on biodiversity in community ecology has been marked by the consideration of species' evolutionary histories and functional traits. Among the different spatial levels at which functional or phylogenetic (hereafter FP) diversity can be quantified, the definition of the general concept of between-community (β) diversity has been given less attention than that of local, within-community (α) and regional, merged-community (γ) diversities. Here, we develop a new method for partitioning FP β diversity into elementary components to determine how and why FP β diversity differs from species β diversity, with the latter reflecting only differences in species' abundances between communities. As a reference example, we consider two distinct measures of FP β diversity: Rao's dissimilarity coefficient (Q_β), which expresses the average FP dissimilarity between communities, and its transformation (E_β), which expresses the effective number of distinct communities. Through analytical partitioning and simulations, we show that Q_β and E_β are connected differently to typical patterns of community structure. The search for the ecological and evolutionary processes that drive community assembly and the assessment of community resilience and stability have indeed revealed typical community structures: the local clustering of species with similar traits or shared evolutionary histories and the local (α) or regional (γ) presence of functionally or phylogenetically redundant versus unique species. We show that while Q_β and E_β are both increasing functions of species β diversity and FP γ uniqueness, Q_β increases with FP clustering, while E_β increases with FP α redundancy. We also show that the component of FP clustering included in Q_β partitioning formula allows the detection of an overall trend of overdispersion or clustering in a dataset without the need to use null models. To facilitate and secure the selection of an index of β diversity for a given study, we call, through our study, for the development of formal and precise definitions for FP β diversity in light of the concepts of clustering versus overdispersion and redundancy versus uniqueness. In particular, we call for further research on when and why FP β diversity should increase with FP clustering.

Warming and more variable climates threaten to upend historical tree ranges, climatic sensitivity, and vigor. In western North America, the species Picea engelmannii var. engelmannii Parry ex Engelmann (Engelmann spruce) and Picea pungens Engelmann (Colorado blue spruce) are widespread spruce that act as foundational species in their montane to subalpine habitats. However, there is currently a lack of knowledge on P. pungens climatic responses, and how it differs from P. engelmannii. To address this gap, we assessed the climatic sensitivity and correlates of tree growth in a co-occurring old-growth stand of P. engelmannii and P. pungens, at high elevation in southern Utah, USA. We report the putative oldest cross-dated P. pungens, with 457 rings, and sampled multiple P. pungens >400 years old. Both Picea populations had strongly positive growth responses to May–July precipitation and negative responses to maximum May–July temperature. Notably, October in the previous year had the strongest correlation with growth for both Picea species. Neither population exhibited signs of directional changes in climate–growth responses. Spectral analysis identified peaks associated with El Niño–Southern Oscillation at 3–4 years and quasi-decadal oscillations (18–20 years) in both species. Cumulatively, our results highlight the growth–climate relationships of two frequently understudied subalpine tree species. In particular, P. pungens may warrant further study across its range and identification of other ancient populations.

Participatory science (i.e., “community science” or “citizen science”) platforms are increasingly used at every level of ecological and conservation research, including disease monitoring. Here, we used a comprehensive, ground-truthed mortality dataset to judge how well participatory science data from iNaturalist represented the magnitude, taxonomic, temporal, and spatial patterns of waterbird mortality associated with a mass mortality event following the incursion of highly pathogenic avian influenza in eastern Canada in 2022. The iNaturalist dataset was effective at identifying species with high mortality (especially Northern Gannets, Morus bassanus), along with the time period and spatial regions with high concentrations of avian deaths. However, iNaturalist data severely underestimated the magnitude, overestimated the taxonomic breadth, and poorly represented the full geographic scope of disease-related deaths. Our results suggest iNaturalist can be used to identify the species, timing, and location of relatively high mortality in situations where no other information is available and to supplement conventional sources of data. However, iNaturalist alone can neither quantify the magnitude nor pinpoint the mechanisms of mortality and therefore is not a viable substitute for comprehensive mortality assessments.

An increase in predation risk triggers a trait response of prey, which alters the interactions between the prey and other species, ultimately affecting other species in the ecosystem. Such predator-driven trait-mediated indirect effects (TMIEs) may have been shaped by long-term evolutionary processes involving the organisms involved, but learning may also be important, especially in contemporary ecosystems experiencing repeated biological invasions. The apple snail Pomacea canaliculata is an important introduced pest of rice, Oryza sativa. Recently, the carrion crow Corvus corone has been found to prey on this species only in some areas, suggesting that learning is involved in this predation. In addition, apple snails can learn to escape from predators and exhibit predator-specific responses. Thus, the “chain of learning” by the crow and the snail may shape novel TMIEs in the rice ecosystem. We conducted field and mesocosm experiments to test this hypothesis. In the field experiment, we simulated predation by crows in rice fields and investigated the behavior of apple snails. The snails exhibited escape behaviors in response to the simulated predation, and both the proportion of individuals showing the escape response and the degree of escape response were greater in fields with predation by crows than those without predation. In the mesocosm experiment, apple snails from fields with and without predation by crows were separately introduced into mesocosms simulating rice fields, and the behaviors of the snails and the number of remaining rice plants were recorded for 16 days at three levels of predation risk (daily, every 4 days, or no predation). Both the presence/absence of predation in the collection fields and simulated predation affected the escape responses of the snails. Moreover, damage to rice was more severe in mesocosms containing snails from fields without predation than those containing snails from fields with predation. These results suggest that the “chain of learning” causes TMIEs in agroecosystems.

Reintroductions are often needed to recover carnivore populations and restore ecological processes. Felids are common subjects of reintroduction efforts, but published population models informing felid reintroduction plans are uncommon, and poor planning has sometimes caused issues in felid reintroduction programs. In the United States, ocelots (Leopardus pardalis pardalis) are classified as endangered, and recovery requires population expansion into historic habitat. A multi-organization effort is underway to establish a new ocelot population in Texas by releasing ocelots into an area of 478 km² of suitable habitat in ocelots' historic but now unoccupied range. In this study, we used population viability analyses to compare different ocelot reintroduction strategies for the identified reintroduction area. Based on a potential ocelot breeding program's limitations, we modeled reintroduction using a founding population of no more than six ocelots and no more than four ocelots released per year for no more than 15 subsequent years. Within these limitations, we assessed projected population abundances and extinction risks after 30 years for 20 different reintroduction strategies. We found that long-term releases are necessary to establish a viable population; under conservative model assumptions, releasing six ocelots in the initial year and then releasing four individuals annually for an additional 10–15 years is necessary for attaining a projected population greater than 36.62 ocelots (baseline) with <6% extinction risk. We also found that ocelot population abundance is about equally sensitive to post-release mortality and inbreeding depression. This highlights the importance of not only supporting reintroduced ocelots' survival but also managing for high genetic diversity in the reintroduction program. Further, we found that realistic but more liberal assumptions on the carrying capacity of the reintroduction area and the age of first reproduction for ocelots increase projected population abundances (53.95 individuals and 61.26 individuals, respectively), and thus reintroduction success. The model's sensitivity to carrying capacity suggests that long-term habitat protection and expansion are among the most important management actions to support ocelot reintroduction. Our study establishes the first population viability model for an ocelot reintroduction plan anywhere across the species' wide geographic range, and it reinforces several key considerations for wildlife reintroduction efforts worldwide.

Chondrichthyans (sharks, rays, skates, and chimaeras) make up one of the oldest and most ecologically diverse vertebrate groups, yet they face severe threats from fishing, necessitating improved management strategies. To effectively manage these species, we need to understand their spatial interactions with fisheries. However, this understanding is often challenged by limited data on chondrichthyan catches and species identification. In such cases, assessing potential risks from fishing activities can provide valuable insights into these spatial interactions. Here, we propose a method combining geostatistical models fitted to a fishery-independent dataset with vessel monitoring system (VMS) data to estimate the spatial overlap between chondrichthyans and fishing. Our case study focuses on the western Adriatic Sea in the Mediterranean, examining the overlap between bottom trawling (including otter bottom trawling and beam trawling) and demersal chondrichthyans. We find that the northwestern part of the basin is a hotspot where threatened chondrichthyans (classified as Vulnerable, Endangered, or Critically Endangered by the International Union for Conservation of Nature Red List) greatly overlap with bottom trawling activities. Moreover, some areas, such as the northernmost part of the Adriatic and the “area dei fondi sporchi” in the north-central offshore part, exhibit minimal overlap between threatened chondrichthyans and bottom trawling, potentially serving as refuges. We recommend prioritizing the management of otter bottom trawling in the northwestern basin to protect these threatened species, while also paying attention to the possible impacts of beam trawling on skates and chondrichthyan habitats. Despite certain limitations, our findings demonstrate that combining geostatistical models of species distributions with VMS data is a promising method for identifying areas of concern for species vulnerable to fishing. This approach can inform targeted management measures and cost-effective onboard monitoring programs.

Heat waves, brief periods of unusually high temperatures, are damaging to agroecosystems and are increasing in frequency and intensity due to climate change. Despite growing appreciation for the threat that heat waves pose to agricultural sustainability, we have a poor understanding of what determines their impact on agroecological interactions in the field. Here, we report the results of a field experiment that examined how heat waves and their timing interact with crop pest resistance to influence the interactions between potato (Solanum tuberosum) and its most damaging pest, the Colorado potato beetle (CPB; Leptinotarsa decemlineata). We used open-top chambers and ceramic heaters to generate heat wave conditions in field plots with pest-resistant and pest-susceptible potato varieties at four CPB developmental stages. We then assessed CPB performance, leaf herbivory, and tuber yield. The neonate-stage heat wave reduced larval survival by 10%, but the surviving larvae were 18% larger and developed 15% faster. However, these effects occurred only on the susceptible variety; both larval survival and growth were unaffected by the heat wave in the pest-resistant variety. Moreover, the neonate-stage heat wave reduced adult survival by 15%, suggesting negative carry-over effects of early-life heat exposure. Heat wave events after the neonate stage had no effects on CPB performance, crop damage, or tuber yield. Our results indicate that timing and pest resistance in crops are essential for understanding the impacts of extreme heat events on crop-pest dynamics. Agroecological pest management in an increasingly variable and extreme climate will likely benefit from the development of strategies that account for the seasonal timing of potential heat events and from the continued use of crop varieties bred for pest resistance, which our results suggest may dampen the impacts of extreme temperatures on crop-pest interactions.

Ontogenetic changes in area use, habitat use, and trophic interactions play an important role in the ecology, demography, and ultimately population dynamics of many species. Assumed to be driven by shifting life-history requirements, trophic niche shifts in white sharks (Carcharodon carcharias) are well documented, but the timing of the spatial niche shift that is hypothesized to occur with the trophic niche shift remains poorly understood. To document how fine-scale area use varies as sharks age and the timing of the ontogenetic spatial shift of this top predator, we tracked individual white sharks tagged as young-of-the-year or young juveniles over multiple years. Using data from juvenile white sharks detected over multiple years in a nursery habitat with a high-density receiver array, we found no difference in area use with age. However, using a coast-wide receiver array including nursery and adult habitat, we found the probability of detecting a juvenile white shark in nursery habitat decreased with age, with a concurrent increasing probability of detection in adult habitat. As the conservation and management of this species relies on understanding nursery habitat use and age-related movements, data presented here address an important knowledge gap for the understudied juvenile to subadult life stages and the ontogenetic habitat shift of this species.