Acta Oecologica-International Journal of Ecology最新文献

Perennials has been proposed as new crops because their root syndrome offers more ecosystem services and a better use of resources than the annual one. Objective: To compare the ontogenetic trajectory of root syndromes of annual (P. gracilis and P. angustifolia) and perennial (P. pinetorum and P. mendocina) species of Physaria (Brassicaceae) and their root trait relationships.

Results and Conclusion

Roots became conservative as plants grew, independently of the life cycle of the species. However, perennials invested initially more resources in increasing storage capacity (bigger and thicker roots) while annuals favored increasing the exploration capacity (higher SRL). During first anthesis we found tradeoffs between acquisitive and conservative traits, as expected according to the Root Economic Spectrum (RES), but after the first year, those tradeoffs disappeared and perennials were able to combine a thick and deep taproot and high investment in C reserves with some well-developed acquisitive traits such as higher SRL and total length. This suggest that root traits should be selected during the second year, when no tradeoff exist. Differences between annuals and perennials in most structural taproot traits remained constant along the ontogenetic trajectory, thus the relative position of species in the RES did not change over time. We found a gradient of root strategies supported by the RES theory: from acquisitive in the annual P. gracilis (high SRL, STD and total length) to conservative in the perennial P. mendocina (high root biomass, root diameter, tissue density and storage) with intermediate strategies in P. angustifolia and P. pinetorum.

The capability of plants to modify phenotypic characteristics through interactions with the environment can contribute to functional stability, particularly when this plasticity influences traits associated with survival, rendering it a pivotal mechanism for adaptation. Grime's CSR theory is employed to classify plants based on functional traits dictating competitive, stress, and ruderal tolerance strategies, as these traits serve as indicators of plant responses to environmental stimuli. This study examines the variation in plant functional traits (morphophysiological and phytochemical) within herbaceous communities across a chronosequence of natural regeneration after land-use alteration and abandonment. We investigate whether a correlation exists between regeneration duration and community-weighted mean values through principal component analysis and canonical correspondence analysis. Intraspecific variability of traits is assessed using one-way ANOVA and Tukey's post-hoc test at a significance level of 5% for mean comparisons. Generally, with progressing regeneration, intraspecific differences emerge, including elevated carbon:nitrogen ratio, phenolic compounds, and carbon assimilation, alongside reductions in leaf area, plant height, leaf succulence, individual biomass, and leaf nitrogen content. Consequently, pasture and initial regeneration communities harbor species with functional traits akin to ruderal species, whereas species inhabiting later stages exhibit traits associated with competitors. Analysis of intraspecific variation demonstrates that species occupying sites at different regeneration stages exhibit phenotypic plasticity. The findings underscore how alterations in environmental conditions during natural regeneration influence functional trait values, and underscore the utility of CSR theory for quantifying, comparing, and predicting community structure based on adaptive plant strategies.

In invaded regions, the introduced non-native plants Reynoutria japonica and Impatiens glandulifera show little grazing damage, most likely due to the absence of specialized herbivores and the deterrent effect of secondary metabolites on generalist herbivores. The low degree of grazing damage has been explained by the non-mutually exclusive enemy-release and novel weapon hypotheses. We tested assumptions of these hypotheses by conducting a series of preference tests in which leaf samples from R. japonica, I. glandulifera, and the native Urtica dioica were offered to five species of generalist gastropods (the native Arianta arbustorum, Cepaea nemoralis and Fruticicola fruticum, and the non-native invasive Hygromia cinctella and Arion vulgaris). In addition, we determined the C/N-ratio and total phenolic compounds (as a surrogate of secondary metabolites) of the plant species. In the choice experiment with fresh leaf samples, all snail species showed a preference for U. dioica, with the exception of the non-native invasive slug A. vulgaris, which ate leaf tissue from I. gladulifera almost as much as from U. dioica. The snails’ preference of U. dioica was even more pronounced when the fresh weight of leaf material eaten was considered. No-choice tests with either fresh or dead R. japonica leaves showed that most individuals of all species ate small amounts of fresh leaves, but less of dead leaves. In contrast, no-choice tests with either fresh or senescent I. glandulifera leaf tissue showed that individuals of all five gastropod species consumed larger amounts of senescent leaves than fresh leaves, probably because secondary compounds have been broken down or leached or the leaf texture has changed. The low susceptibility of these non-native invasive plants to the gastropods can most likely be explained by a combination of chemical and physical plant characteristics.

Cities are expanding rapidly and emerging as complex ecosystems. This expansion of urbanized areas has resulted in the alteration and fragmentation of several natural habitats. Recent studies have shown that cities support a significant level of biodiversity. This unexpected role of cities holds promise for advancing knowledge of urban ecosystems and promoting their conservation. In particular, the connectivity of plant populations through pollen transfer is crucial for the long-term persistence of insect-pollinated plant species. In this study, we tracked pollen movement areas in four isolated patches of urban greenery in urbanized area using quantum dots. We studied Fritillaria imperialis (spring) and Hemerocallis sp. (mid-summer). Our research revealed frequent pollen transfer between small, isolated flowering patches, even when these locations were not connected by green corridors. Common elements found in urban ecosystems, such as streets, trails, and pavements, do not stop the dispersion of pollen grains. Moreover, the migration pathways of pollen grains vary for each species according to different factors. For F. imperialis, we identified the proportion of green areas in proximity to the study location as a key factor in shaping pollen transfer. For Hemerocallis, we discovered that the proportion of green areas, the distance between study sites, and the frequency of pollinator visits are influential factors. Our study demonstrates that small isolated plant populations exchange pollen due to pollinator movement, indicating that these small populations may serve as stepping stones for pollinators among larger populations.

Effects of fires on carnivores are still poorly understood, particularly in the fire-prone Mediterranean basin. For instance, whether the effects are mainly mediated by prey abundance (Prey Abundance Hypothesis, PAH), prey catchability (Prey Catchability Hypothesis, PCH) or habitat suitability is unclear. Our objective was to investigate the role of fire, mammalian prey abundance, habitat suitability and their interactions in shaping the use of space and time of two carnivores, i.e., the red fox Vulpes vulpes and the stone marten Martes foina. The study area was Monte Pisano (Italy), where 12 km² of surface burned in 2018. In early summer 2021 a stratified random sampling design was implemented, with fire and forest type as main strata. Fifty sites were selected, and two infrared cameras were placed at each site. Camera data were used to develop single-species occupancy models for the two predators, whereas time overlap between theme and their prey was evaluated through the Mardia-Watson-Wheeler test. Fox occupancy decreased with increasing herbaceous cover, but only when “mouse and voles” abundance was medium to high, regardless of habitat type. Fox also had significant differences in temporal activity between burnt and unburnt areas, not coupled by a similar pattern for its prey. In contrast, stone marten occupancy mainly depended on canopy cover. The fox could have adapted its hunting strategy to features of the environment and prey abundance, somehow supporting both PCH and PAH. In time, this species could optimize its activity in burnt and unburnt areas according to the brightness of the night. Differences in activity in “mice and voles” were interpreted as anti-predatory responses to the fox. Lastly, the stone marten did not pursue its prey in open areas. In conclusion, carnivores’ habitat use and mammalian predator-prey relationships were overall influenced by fire and post-fire successions.

There is still no consensus regarding the ultimate cause of the famous 3–4-year population cycles of lemmings. According to the plant stress hypothesis, herbivore population peaks are caused by stress factors that force plants to reallocate stored defensive proteins to transportable and easily digestible N-compounds. One possible plant stress factor is ionization caused by exhalation of the radioactive noble gas radon, which is enhanced after spring tides, i.e., tides at new or full Moon. I hypothesized that increased ionization caused by radon accumulation in the subnivean space after peak spring tides, which occur close to perihelion (31 December–05 January, when the Earth–Sun distance is shortest), and at 3.8-year intervals, results in increased protein digestibility of mosses, which are important food for lemmings. Population outbreaks of Norway lemming Lemmus lemmus occurred two years after peak spring tides during 1871–1910, when also perigee (the time when the Earth–Moon distance is shortest) coincided with spring tides and perihelion. Thereafter this relationship weakened, and lemming peaks became less pronounced and more related to plant seed indices. As we have now entered a new 30-year period with coincidence of spring tide, perihelion and perigee, I predict more regular and pronounced lemming outbreaks in the next decades, unless radon accumulation is prevented by frequent lack of a stable snow cover due to global warming.

The mutualism between the fig tree and the pollinating fig wasps is a keystone interaction in tropical forests. However, many antagonistic interactions also occur in the system, taking advantage of the fig trees and the pollinator. One such example is an antagonistic gall midge (Cecidomyiidae) that develops inside figs. Gall midges inside figs have been documented in a few Ficus species around the world, but to our knowledge they have not previously been observed in Panama. In this study the newly observed Panamanian fig gall midge is documented, together with its parasitoid wasp. The fig gall midge was only found in Ficus citrifolia figs. We investigated the effect of fig gall midge presence on the number of seeds and the number of pollinating wasps (Pegoscapus tonduzi) in a fig and aimed to identify the species based on morphology and barcoding of the COI region. We found that the fig gall midge had no, or a negligible effect, on the reproduction of the fig tree - fig wasp mutualism. The fig gall midge most likely belongs to the genus Ficiomyia, close to Ficiomyia perarticulata. The parasitoid belongs to the genus Physothorax, close to Physothorax russelli. This study suggests that the potentially newly arrived fig gall midge currently has no major effect on the fig tree - fig wasp mutualism. However, should infestation rates increase, it is likely that the fig gall midge would affect the mutualism negatively as it has in other parts of the world. More studies on the fig gall midge species distributions in this region would be valuable and would connect these newly observed species to a larger community, adding yet another species to this complex but classic example of a mutualism.

Many plant functional traits exhibit variations along spatial gradients, and exploring such geographical variations is of great reference value for understanding the evolutionary process of plant distribution and response mechanisms to biotic and abiotic factors. Fruit type (fleshy vs. dry fruits), a key reproductive characteristic of plants, plays an important role in seed dispersal processes. Environmental factors, plant growth form, and phylogeny are the most frequently discussed factors that explain the geographical patterns of fruit type. Disentangling the relative contribution of each factor is challenging, and previous studies have not been consistent. In the present study, we compiled a dataset of 2668 plant species from 22 ecological research stations of the Chinese Ecosystem Research Network, including diverse ecosystems across 26° latitude. The pattern of fruit type divergence (i.e., flesh vs. dry fruits) was primarily explained by phylogeny (partial R²_lik = 65.60%), whereas growth form and environmental factors revealed little variation. Interestingly, the relative contribution of phylogeny in explaining fruit-type divergence was larger in the flora at low latitudes than that at high latitudes. Temperature variables, particularly low-temperature variables, were correlated with partial R²_lik, with the results revealing that the higher the temperature, the stronger the explanatory degree of phylogeny. Our findings provide a detailed explanation for the ecological and evolutionary patterns underlying the divergence of fruit types, shedding light on understanding the geographic distribution of fruit types.

The foraging behavior of ants may be linked to the body size of workers, which serves as an adaptation to suboptimal external temperatures. The relationship between foraging behavior and body size is especially noticeable in polymorphic species, which display a broad range of variation in worker body size. An increasing number of studies have found that body size plays an important role in the division of labor among monomorphic ants, which do not display physical subcastes of workers. This study aimed to investigate whether the workers of the monomorphic ant Lasius niger respond to temperature in a similar way to polymorphic species. Surprisingly, our findings indicate that the mean body size of workers foraging in high temperatures during the afternoon is significantly smaller than that of workers foraging in much lower temperatures during the morning. Our study supports the idea, proposed by other authors, that simple radiative heat transfer does not fully explain the significance of body size for thermal tolerance. We hypothesize that allocating smaller workers when the temperature is high protects the colony from overheating.

Competition for nest site resources among sympatric bird species leads to differences in occupying superior resources, which can directly influence their breeding performance. However, how sympatric congeneric bird species alleviate interspecific competition in nest site selection and achieve coexistence remains unclear. Therefore, we conducted a long-term investigation on the nest site selection and breeding performance of two sympatric congeneric species, Scaly-breasted Munia (Lonchura striata) and White-rumped Munia (Lonchura punctulata) in Xishuangbanna, Yunnan Province, southwest China, from 2017 to 2021. Our findings revealed that White-rumped Munia and Scaly-breasted Munia shared overlapped breeding period, but had significant spatial segregation. Regarding the impact of nest site selection on the breeding performance of these two bird species, we found that increasing nest concealment led to higher nestling numbers, fledgling numbers, and breeding success rate. Conversely, greater proximity to nests of heterologous species was correlated with reduced nestling numbers, hatching rates, and breeding success rates. Additionally, nests located in closer proximity to water edges exhibited reduced fledgling numbers, whereas choosing trees with larger diameter at breast height positively correlated with higher fledgling numbers. Compared to White-rumped Munia, Scaly-breasted Munia were inclined to occupy more concealed nests, tree with larger diameters, and closer to heterologous nests. Therefore, the nestling numbers, the fledgling rate, and the breeding success rate of the Scaly-breasted Munia were significantly higher than those of the White-rumped Munia. This study further showed that the increase of nest concealment and decrease of nearest distance to the nest of heterologous species decreased nest predation rate, therefore, increased the breeding success rate. Our study unveiled that, by spatial segregation and different nest site selection, two sibling bird species with highly overlapped breeding period can achieve coexistence in tropical areas.