Basic and Applied Ecology最新文献

Plant diversity is an important driver of many ecosystem processes within and among trophic levels. There is growing evidence that the strength of plant diversity effects depends on the biotic and abiotic environmental conditions. Plant and soil history may be underlying mechanisms of an observed strengthening of biodiversity effects in aging biodiversity experiments. Temporal changes in biodiversity-ecosystem functioning (BEF) relationships have been observed primarily for plants, while dynamics of higher trophic levels are little studied. However, similar patterns can be expected for higher trophic levels because of the close links between producers and consumers. Here, we compare the effects of plant diversity on consumer communities (richness, abundance, diversity, and community composition) and consumer-mediated functions (herbivory and predation) in plant communities with different plant and soil histories. Across six study years, plant diversity had a positive effect on consumer richness, abundance, diversity, and herbivory, whereas the level of predation was not significantly affected by plant diversity. Furthermore, consumer community composition shifted significantly with increasing diversity of plant communities. In addition, consumer abundance, composition, and consumer functions (herbivory and predation) differed between plant communities of different histories. However, contrary to our expectations, plant and soil history caused no significant change in the effects of plant diversity on consumer communities and functions, indicating that these history effects do not provide a mechanistic explanation for plant diversity effects on aboveground invertebrate communities. Thus, our results suggest that plant diversity is a major driver of aboveground invertebrate communities and functions across grassland ages and should be maximized to protect and restore multitrophic biodiversity.

Global demand for vegetable oil is projected to expand to 28 Mt by 2028. Oilseed rape (OSR) is the predominant oilseed crop in Europe. Its nutritional value is determined by seed oil content and fatty acids (FAs) composition. Insect pollination increases seed oil content, however, its benefit on FAs composition remains unknown. In this study, we address this gap by investigating the variation of OSR seed oil content and FAs composition along a gradient of bee abundance in farmed OSR fields. We used a pollinator exclusion experiment to disentangle the contribution of pollination processes, i.e. wind, self and insect pollination. We show that bees improved OSR nutritional value by increasing amount of poly-unsaturated FAs and decreasing the amount saturated and trans-saturated FAs. In addition, oil content was higher in seeds with than without access to pollinators. Our study provides for the first time, to the best of our knowledge, evidence that insect pollination enhances the quality value of OSR oil by affecting FAs composition. Such effect implies potential negative consequences with any further decline of pollinator abundance. More investigations are also needed to better understand the mechanisms by which insect pollination affects FAs composition, and the way to enhance such mechanisms.

Seeds removed by animals have one of two mutually exclusive fates – they are either predated or dispersed and still alive. The quality of seed dispersal by animals and the number of predated seeds will therefore determine net interaction outcomes for plants. Yet, it is poorly understood what proportion of removed seeds animals can predate before benefits of dispersal no longer outweigh costs of seed loss.

Here, we calculated the mutualism-antagonism continuum for seed removal of the fleshy-fruited tree Frangula alnus by the seed-predating bird Coccothraustes coccothraustes in Białowieża Forest. We integrated effects of the bird during seed dispersal (fruit handling, seed predation, and seed deposition) into microhabitat-structured tree population models.

Results of our models showed that the probability of a seed of F. alnus reaching maturity after seed removal by C. coccothraustes decreased from 0.0028% to 0% as seed predation increased from 0% to 100%. Seed removal was beneficial when less than 63.7% of seeds were predated, and antagonistic when more than 72.0% of seeds were predated. Modifying key model parameters (here, the negative effect of fruit pulp on seedling recruitment and the frequency of forest gaps) decreased and increased rates of seed predation, at which costs of seed loss outweighed benefits of seed dispersal (from 37.9% to 80.7%).

Our findings highlight that benefits of animal seed dispersal can largely outweigh costs of seed predation in a fleshy-fruited tree. Yet, the mutualism-antagonism continuum of seed removal depends on intrinsic factors (e.g. variation in interactions among individuals) and extrinsic factors (e.g. the environment) of seed dispersal and plant demography. Because C. coccothraustes was observed predating at least 80% of removed seeds, it appears to be an antagonist of animal-dispersed plants and exploiter of the seed dispersal mutualism.

Janzen-Connell effects state that the accumulation of host-specific natural enemies near parent plants can negatively affect their offspring. Negative plant-soil feedbacks can produce patterns of seedling performance predicted by Janzen-Connell effects and influence plant populations, but their relevance in field conditions remains unclear. Here, using spatial point-pattern analysis, we examine the spatial distribution of Jacobaea vulgaris to assess whether distance- and density-dependent predictions of Janzen-Connell effects are evident in the field. We established 27 replicated 64 m² plots at two grassland sites and mapped positions of rosette-bearing and flowering J. vulgaris plants within each plot. To investigate temporal distribution patterns, we tracked plant positions repeatedly in three plots during a single season. Additionally, we tested whether these patterns are soil-mediated. Soil samples were collected underneath flowering plants and at a distance of 0.5 meter, and used to compare seed germination, seedling survival, and growth under controlled conditions. Furthermore, we measured J. vulgaris growth in soil from patches with high J. vulgaris densities and in soil from areas outside these patches. The density of rosette-bearing plants was lower at close distances from flowering plants than expected from null models, suggesting negative distance-dependent plant recruitment. The degree of clustering decreased over time from rosette-bearing to flowering plants, indicating density-dependent self-thinning. Seed germination was higher in soil further away from flowering J. vulgaris plants than in soil underneath plants at one site, but soil distance was not an overall significant factor in explaining seed germination. However, seedling mortality and biomass did not differ between soils collected at the two distances, and plants produced similar biomass in soil collected from inside and outside J. vulgaris patches. Our study demonstrates conspecific distance- and density-dependent plant recruitment in J. vulgaris in the field, but we found no evidence this depends on belowground natural enemies.

Plant protection products (PPPs) are among the many drivers that lead to the loss of biodiversity in agricultural landscapes and they are a contributing factor to the global decline of amphibians. The aim of the present study is to estimate the potential exposure of amphibian population networks to PPPs. Specifically, our goal is to describe the spatial overlap of amphibian population networks with agricultural crops where PPPs are potentially used. We estimate terrestrial habitat suitability for eleven amphibian species using a multi-scale species distribution modelling approach. Using the suitability maps as the basis for estimating landscape resistance, we then calculate potential dispersal corridors between known breeding sites for each species. Where available, we use local landscape genetic studies from the literature to validate and select the most appropriate resistance model for each species. By comparing the locations of suitable habitat and dispersal corridors with a parcel-scale database on agricultural land-use, we locate and quantify potential hotspots for PPP-exposure within the core habitat around each species’ breeding sites and along the movement routes between them. By highlighting differences among species, we identify species which are particularly at risk of exposure and gain insight into the mechanisms with which PPPs in terrestrial habitats may potentially influence these networks. Together, the maps provide policy makers with a flexible tool that can identify and prioritize regions for the implementation of locally adapted management strategies.

Small mustelids are an understudied group partly due to the challenges in detecting and monitoring their populations. Despite the classification as Least Concern for several small mustelid species, some studies indicate a population decline in parts of their range. Therefore, efficient and group-specific methods are essential to support monitoring efforts. Camera traps are widely used, particularly to monitor cryptic and nocturnal species such as most carnivores. However, they tend to miss small-sized and fast-moving species due to the sensitivity of the passive infrared sensor. The Mostela is a device which consists of a camera trap and a tracking tunnel inside a wooden box, designed specifically to detect small mustelids. Here, we propose testing the performance of this device and comparing it to a tree-mounted camera trap, using the least weasel (M. nivalis) as a case study. We used multi-scale occupancy models to estimate differences in the detection probability between devices. Although both methods detected the least weasel, the detection probability was higher with the Mostela (0.8, BCI: 0.52–0.97 vs 0.2, BCI: 0.03–0.48). Furthermore, we obtained a higher trapping rate when using a shorter distance between sampling stations (∼350 m). Although the Mostela performed better at detecting the weasel, the number of independent events was low (N = 11). Therefore, we present recommendations in terms of deployment and future research since the development and testing of new methods are essential for the conservation efforts of small mustelids.

Density dependent carry-over effects from one life history stage to another can affect the dynamics of populations. Here we study such carry-over effects from the tadpole to the postmetamorphic juvenile stage in an endangered amphibian, the natterjack toad (Epidalea calamita). We raised tadpoles in outdoor aquatic mesocosms at four densities and assessed juvenile performance after metamorphosis in terrestrial mesocosms. High larval density reduced mass at metamorphosis by 50 % and doubled the length of the larval period. Survival was reduced at the high densities. Larger metamorphs had higher survival in terrestrial mesocosms and remained larger than cohort members at the end of the 30-day experiment. Because juvenile survival drives amphibian population dynamics, density-dependent carry-over effects to the juvenile stage are likely to affect population viability. We discuss the implications of the results for amphibian conservation practice, both pond construction programs and surveys of amphibian populations.

Seedling recruitment is a key process of plant regeneration that often depends on plant functional traits, such as seed size. To optimize forest restoration efforts, we need to better understand how seedling recruitment of different seed sizes varies along environmental gradients with strong variation in abiotic and biotic factors. To understand these interacting effects, we conducted a sowing experiment with different-sized seeds in forests and pastures in the tropical mountains of southern Ecuador. We quantified seedling recruitment in relation to temperature, soil moisture and biotic pressures. We sowed seeds of five tree species of varying seed size at three elevations (1000, 2000 and 3000 m a.s.l.) in primary forest and pastures. We tested (1) how habitat type influences the recruitment of seedlings belonging to three small- and two large-seeded species, and (2) how abiotic and biotic factors limit seedling recruitment of species with different seed sizes. We found that seedlings of the two large-seeded species recruited better than seedlings of the three small-seeded species, but only in the forest habitat. Seedling recruitment of large seeds was primarily limited by high surface temperature, which explains lower recruitment of large seeds in pastures compared to forests. Our study shows that seed size can be a key trait mediating variability in seedling recruitment in tropical ecosystems. We conclude that restoration measures should aim to mitigate extreme temperatures in tropical pastures to aid the natural regeneration of large-seeded tree species.

Climate change might increase plant diseases, reduce crop yields and threaten the livelihoods of millions of smallholder farmers globally. It is thus important to understand the relationships between climate, disease levels and yield to improve management strategies for sustainable agroforestry in a changing climate. One of the major threats to coffee production in Africa is the coffee berry disease (Colletotrichum kahawae). To investigate the effects of climatic and management variables on coffee berry disease (CBD) incidence and yield, we recorded minimum and maximum temperature and relative humidity, as well as CBD and yield, along a broad environmental and management gradient in southwestern Ethiopia during two consecutive years. CBD was affected by several climatic and management variables. For example, CBD incidence increased with minimum temperature during the fruit expansion stage, and decreased with minimum temperature during the endosperm filling stage. CBD incidence was negatively affected by the proportion of resistant cultivars, whereas the coffee structure index (pruning) had no effect on disease incidence. Coffee yield decreased with increasing minimum temperature during the flowering period in 2018 and maximum temperature during the fruit developmental period in 2019. Coffee yield was negatively affected by canopy cover and positively affected by the coffee structure index in both years. Our findings highlight that CBD and yield were affected by different climatic and management variables. Yet, managing for low disease levels and high yield is practically difficult due to season-dependent effects of several climatic variables. One way to break the correlation of climatic variables between seasons might be to take advantage of differences among shade trees in the presence or timing of leaf drop. To reduce CBD incidence, using resistant cultivars is an effective strategy, but this might threaten the wild coffee genetic reservoir.