Basic and Applied Ecology最新文献

Agricultural intensification and expansion are regarded as main drivers of biodiversity loss. This conclusion is mainly based on observed declines of local diversity (α-diversity), while effects on community composition homogenization (decrease of β-diversity) at a larger spatial scale are less well understood. Carabid beetles and spiders represent two widespread guilds and are important predators of pest species. Here we surveyed carabid beetles and spiders in 66 winter wheat fields in four northwestern European countries (Germany, the Netherlands, Sweden and UK) and analyzed how their community composition was related to geographic distance (separation distance between any pairwise fields) and three environmental variables: crop yield (proxy for land-use intensity), percentage cropland (proxy for landscape complexity) and soil organic carbon content (proxy for local soil conditions). We further analyzed whether the relationship between carabid beetle and spider community composition and geographic distance was influenced by environmental variables. We found that, 55 % and 75 % of all observed carabid and spider individuals, respectively, belonged to species that occurred in all four countries. However, individuals of species that were unique to a particular country only accounted for 3 % of all collected individuals for both taxa. Furthermore, we found a negative relationship between distance and similarity of spider communities but not for carabid beetle communities. None of the environmental variables were related to similarity of carabid beetle and spider communities, nor moderated the effects of distance. Our study indicates that across a great part of the European continent, arthropod communities (especially carabid beetles) in agricultural landscapes are composed of very similar species that are robust to current variations in environment and land-use.

Nitrogen (N) fixation by moss-cyanobacteria associations has been recognized as an important N input pathway in many ecosystems from arctic tundra to tropical forests. However, the transfer of fixed N₂ from mosses to the soil as well as the effects of rainfall frequency and volume on this N transfer has hardly been studied – even though mosses can leach nutrients upon rewetting. In this study, we investigated the transfer of fixed N₂ by moss-cyanobacteria associations in one month under four watering regimes with a combination of high and low volume and frequency. For this, we used two morphologically similar moss species collected from ecosystems with different climate and N availability (subarctic - Hylocomium splendens; and tropical - Thuidium delicatulum). Acetylene reduction assays were conducted as a measure of N₂ fixation rates in mosses, and ¹⁵N-N₂ tracing was used to follow the fixed N₂ from moss to the underlying substrate. Nitrogen fixation rates were higher in T. delicatulum than in H. splendens, but rainfall volume and frequency did not show strong effects on N₂ fixation rates. Nonetheless, the extent of N leached from mosses was more sensitive to an increase in rainfall volume than to an increase in frequency, and more N was lost from T. delicatulum under high volume precipitation than from H. splendens. Both total nitrogen and ¹⁵N enrichment results demonstrate that the fixed N₂ was mostly stored in moss tissues with less than 1 % leached to the substrate. Our results show that both moss species retain almost all fixed N₂ within their tissues under small rainfall disturbances within one month, while increased N availability under higher precipitation volume renders some moss species an important N source for the soil.

Agricultural intensification decreases the heterogeneity of the landscape and leads to a decline in hedgerows. As hedgerows provide important habitats for many taxa, this contributes to the loss of biodiversity in agroecosystems. However, the extent to which hedgerows, and in particular their habitat quality in terms of structural characteristics, also influence biodiversity-based ecosystem services is poorly studied. Here, we conducted a systematic review of the Scopus and other literature databases focusing on Central European and UK studies examining (1) the influence of hedgerow habitat quality on the biodiversity of arthropods, earthworms, birds, bats and small mammals and (2) the relationship between selected hedgerow parameters, animal taxa, and ecosystem services such as pollination, seed dispersal, pest and disease control and soil quality regulation. A total of 2260 studies (cut-off date: 13 September 2022) published between 1974 and 2022 were found. After sorting based on inclusion criteria related to the research focus, 89 studies remained for evaluation. Arthropods, birds, and small mammals were studied most frequently, earthworms and bats least frequently. The selected studies showed that structural diversity, layering, woody biomass and density were strongly positively correlated with animal species diversity, while hedgerow length, width and age showed less relevant relationships. Hedgerow connectivity, density, structural diversity, and layering were strongly positive associated with the provision of ecosystem services. We conclude that the structural diversity of hedgerows needs to be increased if their impact on biodiversity and ecosystem service provision is to be improved. It is therefore recommended that hedgerow management measures should specifically consider the ecological importance of the structural diversity of hedgerows.

Faced with pollinator declines, cities could serve as refuges for biodiversity conservation by managing floral resources in public green spaces. Ornamental plants could play an important role in attracting pollinators because they form part of urban floral management. However, knowledge of how their floral traits respond to drought is lacking, and it is unknown whether they will be suitable for pollinators under future climates. The main objective of this study was to determine the covariation of floral traits of ornamental plant species and effects of drought on them. To this end, in a city greenhouse we measured floral traits of eight ornamental species commonly used in urban green spaces in France. We subjected the plants to a control treatment or a drought treatment, reducing the volume and frequency of watering. We observed interspecific variability in floral traits among these species and a change in covariation between the traits pollen quantity and nectar quantity in the drought treatment. Drought influenced morphological traits related to floral display more than other floral traits, with mean decreases of 28 % in floral height, 35 % in floral area and 58 % in the number of floral units. Ornamental plants seemed attractive to different morphotypes of pollinators depending on their floral unit number, nectar sugar concentration or nectar tube depth, with most visits made by Hymenoptera. These results are expected to encourage green-space managers to select urban plants according to their functional characteristics and adapt their choice of plants to climate change.

The introduction of carnivores to islands affects the conservation status of native prey. For two decades, American mink (Neogale vison) has expanded its distribution in the sub-Antarctic archipelago of Austral Patagonia, while preying on nests of solitary ground-nesting birds. Here, upland geese (Chloephaga picta) and flightless steamer ducks (Tachyeres pteneres) are naïve to such predation risk because of the lack of native terrestrial predators. We used nest occupancy models to reveal preferred breeding habitats of those two ground-nesting waterbirds to prioritize areas for future mink control programs. We searched for nests along 80 transects on Navarino Island, southernmost Chile, and 11 transects on 10 nearby islets (3 ± 2.9 ha). Our results showed that islets were essential for breeding in comparison to the main island (5.3 nests/km versus 0.8 nests/km, respectively). The occupancy models revealed that islets were particularly important for flightless steamer ducks, endemic to western Patagonia. As breeding habitat, upland geese preferred medium-dense shrubland, and flightless steamer ducks preferred rocky coastlines. Nest detection was negatively affected by dense vegetation and, in the case of the upland geese, towards the end of the survey. Ten camera traps (n = 385 trap nights) revealed mink presence on all islets, highlighting their capacity to swim in cold water, up to 340 m distance from the main island. We conclude that islets represent breeding refuges for ground-nesting waterbirds and therefore advocate allocating resources for mink control during the warm season on islets. We also provide predictive maps of nesting habitat preference of upland geese and flightless steamer ducks for conservation managers to focus their often scarce human and financial resources on areas critical for breeding. Finally, we argue that detection probability should be an integral part of bird breeding studies, which can be methodologically achieved through targeting transects, not nests, as sample units.

Plant-pollinator interactions are key for the reproduction of wild plants and for food security. However, the role nocturnal pollinators play in wild plant communities is not yet clear. Specifically, it has rarely been studied whether nocturnal pollinators are comparable to diurnal ones in the pollination services they deliver in plant communities. We tested whether nocturnal pollinators have the potential to provide high pollination services to the plants they visit by carrying high conspecific pollen loads. We studied pollen loads carried by nocturnal and diurnal pollinators captured over 24-hour cycles in co-flowering plant communities in Swiss ruderal meadows. Pollen load was less diverse at night, and the proportion of conspecific pollen carried by nocturnal pollinators was higher than that of diurnal ones. Because the majority of plant species visited at night were also visited during the day, floral resource availability could drive the observed patterns in pollen load and amount of conspecific pollen. Nevertheless, nocturnal pollinators do not only carry pollen but can remove and potentially deposit conspecific pollen to the plants they visit. Therefore, pollinators active at night might be an important pollination vector for more plant species than previously thought and should not be neglected in pollination studies.

As the globe gets more urbanised, the question about how natural biodiversity is structured in cities becomes increasingly pertinent. To contribute to an answer, we studied species richness and spatio-temporal structure of bees in a North European metropolitan area. A gradient of 13 sites in the city of Aarhus, Denmark, was censused from April to September 2016. Forty species, i.e. 29 solitary species (40 % of all individuals), ten Bombus species (28 %), and Apis mellifera (32 %), were sampled monthly in pan traps. (i) Information about species traits was extracted from the literature, and trait values were correlated and used to characterize the fauna. Most were soil-nesters, pollen generalists, and common. (ii) Habitat diversity within five concentric circles with trap at the centre and radii from 50 m to 1000 m was related to bee α diversity. The relationship was significant only within 1,000 m for all bees and for bumblebees. Solitary bee diversity was uncorrelated with habitat diversity at all spatial levels. (iii) Spatio-temporal structure was analysed as two networks, one for bees linked to sites, and one for bees linked to months. Link patterns were analysed for levels of nestedness, modularity, and spatio-temporal β diversity. The two networks were weakly and non-significantly nested, but strongly modular, being composed of five and four modules of co-occurring bees, respectively. (iv) Finally, we studied total β diversity, β_TOTAL, being the sum of species turnover, β_TURN, and species loss/gain or nestedness, β_NEST. For both site and season, β_TURN was higher than β_NEST, and site β_TOTAL was higher than season β_TOTAL. One reason for this metacommunity structure may be a high spatio-temporal habitat patchiness, sustaining a rich biodiversity. Thus, a few large areas may not compensate for the loss of several small patches. Consequently, establishment of many green, even small habitats is recommended.

Tens of thousands of plant species globally are harvested to varying extents as non-timber forest products (NTFPs). Local populations of many NTFPs face significant pressures from harvesters, often leading to calls for harvesting guidelines to promote sustainable offtakes. However, most studies to determine sustainable harvest levels implicitly assume that the entire population is available to harvesters. Yet, certain areas or portions of particular NTFP populations outside of protected areas may not be open to harvesting because they are in some sort of cultural or spatial refuge. Using a mixed-methods approach we assessed the prevalence and efficacy of refugia for 70 NTFP plant species at seven communal land sites in south-eastern South Africa. Based on reports from local harvesters, approximately 10 % of the 70 species had part of their population in a refuge. For most of these, populations within a refuge showed lower levels of harvesting and were in a better condition than adjacent populations not in a refuge. These results demonstrate that studies assessing the sustainability of harvesting of NTFP populations should account for whether refugia are present.

Biological invasions are a major threat to biodiversity because of invasive alien species’ high population growth rates and spread in new ranges. The inherent superiority hypothesis states that particular characteristics of alien species cause them to perform better than native species. Using a meta-analysis of 127 studies and more than 900 experimental observations comparing alien and native plant performance, we investigated, whether: (1) studies comparing alien and native performance generally support the inherent superiority hypothesis; (2) the direction and magnitude of superiority depend on the choice of performance measure; and (3) it depends on other aspects of the study design or species. We found that the inherent superiority hypothesis was overall supported, although the strength of this result depended on the chosen measure of effect size (a significant effect for the standardized mean difference SMD (Hedge's g) but not for the log response ratio LRR). Alien plant species were more likely to be found superior compared to natives if performance was measured in terms of growth, reproduction or response to natural enemies. Measuring survival or abundance was less likely to result in alien superiority, while for measurements of physiology and response to mutualists results were mixed. Furthermore, aspects of experimental design, selection and number of study species played an important role. We thus quantitatively showed across a broad range of conditions how choice of performance measure and experimental design affect the direction and magnitude of alien superiority found in small-scale studies. Furthermore, our review pointed out a lack of studies that assessed population growth as a direct determinant of true superiority. Conducting studies using performance measures relevant for superiority, while also considering other potentially important factors such as residence time, will shed more light on how common true alien superiority is and in which contexts it is to be expected.