Ecology最新文献

Disturbance is fundamental to ecosystem dynamics, and its management is foundational to effective ecosystem management for the conservation of biodiversity. Fire is a key agent of disturbance influencing faunal communities in many terrestrial ecosystems, and it underpins the conservation management of fire-prone ecosystems. However, we have a limited understanding of how faunal communities in fire-prone ecosystems respond to variation in fire frequency. Here, we use a long-term fire experiment to investigate the effect of fire frequency on lizard assemblages in an Australian tropical savanna. We sampled lizards using pitfall traps, funnel traps, and direct searches in replicate (n = 3) 1-ha plots that had been burnt every 1, 3, or 5 years or left unburnt for 18 years. We found no significant variation in total lizard abundance or the collective abundances of mesic, semiarid, or widespread biogeographic groups. The abundance of only one of the five most common species was significantly related to fire frequency. Species richness decreased with increased fire frequency and showed a humped relationship with woody cover. Species composition was slightly better explained by variation in woody cover than by fire frequency, with both effects relatively weak. Although woody cover declined with increasing fire frequency, it varied markedly both within and among plots experiencing the same fire treatment, which explains why fire frequency was not as strong a predictor of variation in lizard assemblages as woody cover. Our findings show that the diverse lizard assemblage in our tropical savanna system exhibits a very limited response to variation in long-term fire frequency and attribute this to the marked small-scale variation in woody cover that was inherent under any fire treatment. We conclude that small-scale patchiness in vegetation cover plays a critical role in the responses to fire of faunal species with relatively small foraging territories, reducing a need for larger scale fire mosaics under a “pyrodiversity begets biodiversity” paradigm.

Climate warming can destabilize ecological communities by altering species interactions. Population outbreaks, defined as rapid, exponential increases in population size within a given spatiotemporal scale, are naturally occurring phenomena with significant ecosystem-wide consequences. Such outbreaks are expected to increase in frequency under climate change, yet their ecological consequences under warming remain poorly understood. Here, we conducted a large-scale pond mesocosm experiment (48 mesocosms, each of 2500 L in volume) to show that warming significantly reduced the growth and impeded the regenerative capacity of aquatic plants following the outbreak of an aquatic moth (Parapoynx diminutalis). These effects were driven by warming magnifying herbivory, which substantially diminished the growth and recovery of macrophytes, leading to a turbid state dominated by phytoplankton. Our findings provide strong evidence that global warming can destabilize freshwater ecosystems under population outbreaks, risking the loss of basal resources that provide both food and habitat complexity. The cascading effects on the wider food web could lead to widespread loss of taxonomic and functional diversity, impairing essential ecosystem functions and services.

Plant invasions may alter disease vector abundance by several mechanistic pathways, including modifying microclimates that influence vector survival or changing habitats to influence host use. Here, we used a field experiment and observational data to evaluate multiple mechanistic pathways (tick survival and host abundance) by which plant invasions may alter vector-borne disease risk using the common disease vector lone star tick (Amblyomma americanum), its preeminent host white-tailed deer (Odocoileus virginianus), and the widespread invasive cogongrass (Imperata cylindrica) in the southeastern United States. In the field experiment, ticks survived over 50% longer in areas dominated by the invasive plant compared to those with only native plant species. Invaded areas had lower temperatures and higher relative humidity, yielding a lower vapor pressure deficit (VPD) that likely reduced tick desiccation. The observational study showed similar average tick abundance in native and invaded plant communities and no difference in wildlife host (white-tailed deer) activity between plant communities. However, there was a positive relationship between tick abundance and white-tailed deer activity, but only in native areas. Together, these results suggest that more favorable microclimate conditions resulting in greater tick longevity are the dominant driver of tick abundance in invaded areas, while tick abundance in native-dominated areas may be promoted, at least in part, by white-tailed deer activity. Our results demonstrate that plant invasions can affect multiple, potentially counteracting mechanistic pathways that contribute to tick exposure risk. The complexity of these relationships highlights the need for a better understanding of how invasive species and other global change drivers influence disease vectors and, ultimately, disease transmission.

Many insects damage leaves, a phenomenon that is foundational to their impacts on terrestrial ecosystems. Leaf traits, including chemistry, shape these interactions. In turn, leaf-surface (phylloplane) microbes can act directly or in concert with leaf chemistry to influence leaf choice, especially by insects whose reproductive success is tied to prolonged contact with leaf surfaces. Leafcutter bees (Megachile spp.) cut disks from leaves to line their nests, with leaves and their associated microbes forming the environment in which bees' offspring develop. We hypothesized that phylloplane microbial communities act in concert with leaf chemistry to mediate interactions between the leafcutter bee M. lippiae and the plants they cut. We surveyed phylloplane communities on rose (Rosa × hybrida, Rosaceae) leaflets that were cut versus not cut by wild M. lippiae. Microbial communities differed between cut and non-cut leaflets, with Aspergillus spp. overrepresented on cut leaflets, and Alternaria sp. and Bacillus sp. overrepresented on non-cut leaflets. Then, we inoculated rose leaves in the field to test the effect of these microbial taxa on cutting. When inoculated onto rose leaves, Alternaria and Bacillus had no effect on cutting, but Aspergillus resulted in twice as many cuts as on sham-inoculated leaves. To test whether Aspergillus could protect bee nests against pathogens, we grew Aspergillus with two pathogenic fungi: the generalist insect pathogen Beauveria bassiania and three strains of Ascosphaera that cause chalkbrood disease in bee larvae. Aspergillus did not inhibit the growth of Beauveria, but it markedly slowed the growth of Ascosphaera. To clarify whether these phylloplane microbes reflect differences in leaf chemistry or are instead independent cues that influence leaf cutting, we used liquid chromatography-mass spectroscopy to characterize the metabolome of cut and non-cut leaflets. Chemistry did not differ between cut and non-cut leaflets, nor did it vary as a function of microbial community composition. Our results suggest that Aspergillus, a common member of rose phylloplane communities, mediates interactions between leafcutter bees and roses, potentially affecting the fitness of both partners. This study reveals a previously unexplored role for phylloplane microbes in plant–insect associations.

Ectotherms with lower maintenance costs and broader environmental tolerances are generally more resilient in human-altered landscapes and under current climate change, enhancing their chances of survival and colonization. In this study, we explored how habitat use and foraging strategy are associated with the resting metabolic rate (RMR) of spiders from habitats with significant temperature variability due to anthropogenic disturbance: native forests and young pine plantations, both in the Southern Atlantic Forest. Using open-flow respirometry at 25°C, we measured CO₂ production in immobile spiders to calculate their RMR. Key findings include: (1) all spiders showed 22%–57% lower RMR than predicted by standard metabolic equations; (2) continuous gas exchange patterns, typical of mesic-adapted species, were observed in all cases; (3) the metabolic rate scaling exponent was 0.65; (4) there were no significant RMR differences between habitats, but a negative correlation between RMR and microhabitat thermal amplitude was noted; and (5) active foragers had higher RMRs than passive foragers. These findings enhance our understanding of spider biology, physiology, and ecology, particularly in their responses to anthropogenic stressors.

Galls play a significant role in the plant–insect interactions in various ecosystems worldwide. Consequently, research on gall-inducing insects and their host plants has garnered considerable attention in recent years, with a wealth of uncompiled data. This dataset, comprising 2,059 records of 868 native species, 361 genera, and 106 families of host plants, provides valuable information regarding the Atlantic Forest biome, one of the world's most important rainforests. The five most common botanical families represented in the dataset are Myrtaceae, Asteraceae, Fabaceae, Melastomataceae, and Rubiaceae, accounting for 40.41% of all records and 40.21% of the total number of species. In addition, exotic host plant species from families such as Anacardiaceae, Asteraceae, Fabaceae, Myrtaceae, and Verbenaceae are presented. The dataset also includes 204 species of gall-inducing insects, with a large predominance of Diptera (189 species), followed by seven species of Hemiptera, four species of Lepidoptera, and two species each of Coleoptera and Thysanoptera. This study is the first to compile inventories of plant-galling insect communities and information on the diversity and distribution of insect galls and their host plants in the Atlantic Forest. The dataset highlights areas for further research on patterns of diversity and distribution and offers a foundation for developing and testing new ecological hypotheses. Researchers are encouraged to cite this data paper when utilizing the information in their publications and to inform us of the application of the data. No copyright restrictions were applied to the dataset.

Predator use of resource subsidies can strengthen top-down effects on prey when predators respond numerically to subsidies. Although allochthonous subsidies are generally transported along natural gradients, consumers can cross ecosystem boundaries to acquire subsidies, thereby linking disparate ecosystems. In coastal Arctic ecosystems, terrestrial predators like Arctic foxes (Vulpes lagopus) cross into the marine environment (sea ice) during winter to access marine resources. Arctic foxes kill seal pups and scavenge seal carrion (often remains from polar bear Ursus maritimus kills), especially when rodent abundance is low. Terrestrial predator use of marine subsidies may strengthen the top-down control of tundra food webs, but this hypothesis remained untested. We evaluated tundra food web dynamics at the terrestrial–marine interface from an ecosystem-level perspective by assessing: (1) how winter environmental conditions affect rodent abundance and marine subsidy availability, (2) the response of the Arctic fox population to this seasonal food variability, and (3) the subsequent effects of Arctic foxes on Canada goose (Branta canadensis interior) reproduction. Arctic foxes responded numerically to rodent abundance, which was positively related to snow persistence. Arctic fox abundance was positively related to polar bear body condition metrics, which were used as a proxy for marine subsidy availability. Canada goose reproductive success, in turn, was negatively related to Arctic fox abundance. Long-term trends in goose reproduction and snow persistence also indicate an ongoing phenological mismatch between nesting initiation and spring onset. Our results reveal near-term apparent competition between rodents and geese through a shared predator, Arctic foxes, contrasting with prior studies evaluating rodent–goose–predator relationships. Moreover, we establish a link between tundra and sea ice food webs by demonstrating how seal availability can affect goose reproduction indirectly by increasing Arctic fox predation on goose nests via a population response of foxes to marine resources. These marine resources are often provisioned by polar bears, and with both Arctic foxes and polar bears undergoing long-term regional declines evidently driven by climate-related changes in prey abundance and availability, we contextualize our study within ongoing climate change and highlight the vulnerability of this likely widespread terrestrial–marine linkage in a warming Arctic.

Viruses have the potential to impact host populations, but our picture of host–virus relationships is largely colored by virulent pathogens that lead to easily detectable epizootic events. Modern molecular methods have demonstrated that viruses are ubiquitous in animal populations, and the influence of these “cryptic” viruses is largely unexplored. Insects provide an ideal system to examine population-level impacts of novel, “cryptic” viruses—short generation times allow for meaningful population-level field studies over a relatively short timeframe, and their abundance and small size facilitate experimental manipulation across each life stage. Many insect species are capable of high population growth rates, potentially buffering them from pathogen-driven declines in the face of high pathogen prevalence. We explored the impacts of a recently detected non-occluded densovirus (Junonia coenia DV, JcDV) on the demography of a nymphalid butterfly, Euphydryas phaeton (Baltimore checkerspot). E. phaeton populations are known to have the capacity for rapid growth and to exhibit large, often unexplained population fluctuations. We used a field mesocosm experiment to measure the vital rates of E. phaeton under a range of levels of viral exposure over 2 years (2021 and 2022) and used these vital rates to parameterize a demographic model of population growth in each year. We found that JcDV reduced E. phaeton post-diapause larval survival, skewed sex ratios toward a male bias, and reduced fecundity in surviving females. JcDV reduced estimated population growth rates in both years, but only led to population decline in 2022. This increased impact was associated with a substantial regional drought, suggesting that the potential for this non-occluded virus to cause population decline is influenced by climatic factors. The findings of our controlled study parallel trends observed in a wild population of E. phaeton, supporting the hypothesis that JcDV can drive population decline. This study demonstrates that cryptic viruses likely influence butterfly population dynamics, especially when their effects are compounded with additional environmental stressors.