Species In Natural Communities Research Articles

Implementing high-throughput insect barcoding in microbiome studies: impact of non-destructive DNA extraction on microbiome reconstruction.

Symbiotic relationships with diverse microorganisms are crucial for many aspects of insect biology. However, while our understanding of insect taxonomic diversity and the distribution of insect species in natural communities is limited, we know much less about their microbiota. In the era of rapid biodiversity declines, as researchers increasingly turn towards DNA-based monitoring, developing and broadly implementing approaches for high-throughput and cost-effective characterization of both insect and insect-associated microbial diversity is essential. We need to verify whether approaches such as high-throughput barcoding, a powerful tool for identifying wild insects, would permit subsequent microbiota reconstruction in these specimens. High-throughput barcoding ("megabarcoding") methods often rely on non-destructive approaches for obtaining template DNA for PCR amplification by leaching DNA out of insect specimens using alkaline buffers such as HotSHOT. This study investigated the impact of HotSHOT on microbial abundance estimates and the reconstructed bacterial community profiles. We addressed this question by comparing quantitative 16S rRNA amplicon sequencing data for HotSHOT-treated or untreated specimens of 16 insect species representing six orders and selected based on the expectation of limited variation among individuals. We find that in 13 species, the treatment significantly reduced microbial abundance estimates, corresponding to an estimated 15-fold decrease in amplifiable 16S rRNA template on average. On the other hand, HotSHOT pre-treatment had a limited effect on microbial community composition. The reconstructed presence of abundant bacteria with known significant effects was not affected. On the other hand, we observed changes in the presence of low-abundance microbes, those close to the reliable detection threshold. Alpha and beta diversity analyses showed compositional differences in only a few species. Our results indicate that HotSHOT pre-treated specimens remain suitable for microbial community composition reconstruction, even if abundance may be hard to estimate. These results indicate that we can cost-effectively combine barcoding with the study of microbiota across wild insect communities. Thus, the voucher specimens obtained using megabarcoding studies targeted at characterizing insect communities can be used for microbiome characterizations. This can substantially aid in speeding up the accumulation of knowledge on the microbiomes of abundant and hyperdiverse insect species.

Body size modulates demographic patterns of top predators and their native and invasive prey: A biomathematical approach

The arrival of invasive species in native communities impacts the structure and functioning of ecosystems, and is considered a critical indicator of loss of biodiversity. Exploring the effects of new species in communities presents challenges addressable through theoretical ecology. Species body size not only shapes trophic relationships, but may also impact predator success and facilitate species coexistence. However, little attention has been paid to the effects of differences in species body size on interactions between native and invasive primary consumers, which could be relevant to their coexistence with higher-level predators. Our aim is to investigate demographic patterns using a dynamic, mechanistic model of two age-structured primary consumers (one invasive and one native) sharing a plant resource and preyed upon by a common predator. In our model, we highlight three crucial phenomena: the structuring of primary consumers into adults and juveniles, reproduction occurring in discrete pulses, and the seasonal addition of new individuals to the population. Hence, the success of one species over the other relies on its reproductive capacity to incorporate individuals in each reproductive cycle. Our simulations reveal that abundance patterns are influenced by body size, suggesting that changes in predator body size could serve as key indicators of shifts in community structure.

Soil nutrient limitation and natural enemies promote the establishment of alien species in native communities.

The invasion of alien plant species threatens the composition and diversity of native communities. However, the invasiveness of alien plants and the resilience of native communities are dependent on the interactions between biotic and abiotic factors, such as natural enemies and nutrient availability. In our study, we simulated the invasion of nine invasive plant species into native plant communities using two levels of nutrient availability and suppression of natural enemies. We evaluated the effect of biotic and abiotic factors on the response of alien target species and the resistance of native communities to invasion. The results showed that the presence of enemies (enemy release) increased the biomass proportion of alien plants while decreasing that of native communities in the absence of nutrient addition. Furthermore, we also found that the negative effect of enemy suppression on the evenness of the native community and the root-to-shoot ratio of alien target species was greatest under nutrient addition. Therefore, nutrient-poor and natural enemies might promote the invasive success of alien species in native communities, whereas nutrient addition and enemy suppression can better enhance the resistance of native plant communities to invasion.

Spatial variation in the sensitivity of freshwater macroinvertebrate assemblages to chemical stressors

Assessing spatial variation in the chemical sensitivity of natural assemblages will enhance ecological relevance and reduce uncertainty in ecological risk assessments and the derivation of environmental quality standards (EQSs). However, the majority of species in natural communities have not undergone toxicity testing for any chemical, which poses a major challenge when assessing their sensitivity. We investigated spatial variation and patterns in the sensitivity of 4084 freshwater macroinvertebrate assemblages across England to 5 general-acting chemicals (heavy metals) and 13 specifically acting chemicals (insecticides) using a novel hierarchical species sensitivity distribution method based on taxonomic relatedness. Furthermore, we explored how river typology relates to spatial variation in assemblage sensitivity to chemicals and the potential impacts of such variation on current EQSs. Our findings revealed that, whereas assemblages with similar taxonomic compositions exhibit comparable sensitivity distributions, assemblages with different taxonomic compositions could have very similar or very different sensitivity distributions. The variation in assemblage sensitivity was greater for specifically acting chemicals than for general-acting chemicals and exhibited spatial clustering patterns. These spatial clustering patterns varied depending on the chemical, and the regions where assemblages were most sensitive to metals were generally not the same as the regions where assemblages were most sensitive to insecticides. Spatial variation in assemblage sensitivity was related to river typology with sensitive assemblages being more common than expected in lowland calcareous (or mixed geology) rivers within very small to small catchments. Comparing spatial variation in assemblage-specific chemical sensitivity to EQSs, we found that the operational EQSs in England would protect most study assemblages (i.e., > 99.5 %), although a small proportion of assemblages may face potential risks associated with azinphos-methyl, copper, and malathion. In many cases the EQSs were very precautionary, potentially requiring expensive control measures or restricting beneficial chemical use with no additional environmental benefit. The development of spatially defined EQSs, possibly based on river types, could be developed to target areas that require the highest level of protection and thus strike a balance between the benefits of chemical use and environmental protection.

Tracking phenological distributions and interaction potential across life stages

Climate change is shifting the phenological timing, duration, and temporal overlap of interacting species in natural communities, reshaping temporal interaction networks worldwide. Despite much recent progress in documenting these phenological shifts, little is known about how the phenologies of species interactions are tracked across different life history stages. Here we analyze four key phenological traits and the pairwise interaction potential of nine amphibian species for the adult (calling/breeding) and subsequent larval (tadpole) stage at eight different sites over six years. We found few strong correlations among phenological traits within species, but the strength of these correlations varied across species. As a consequence, phenological trait combinations of both stages varied substantially across species without clear signs of multidimensional clustering, indicating a distinct and diverse range of species‐specific phenological strategies. Despite this considerable variation in the phenologies across species, the temporal overlap between species was largely preserved through the two life history stages. Further, we also detected significant correlations among the duration and temporal overlap of interactions with other species across stages in five species, demonstrating that temporal patterns of species interactions are mirrored across life history stages. For these species, these results indicate a strong tracking of phenologies and species interactions across life history stages even in species with complex life cycles where stages occupy completely different environments. This suggests that phenological shifts in one stage can impact the temporal dynamics and structure of interaction networks across developmental stages.

State-of-the-art approach on the management of invasive faunistic aquatic alien species: The American bullfrog in Belgium

Invasive alien species are worldwide one of the main reasons for the decline of species in native communities and hence biodiversity. Control or eradication programs are often fragmented leading to cost-inefficient and inadequate results. This paper addresses a state-of-the-art framework of an integrated management approach based on the case study on the control of the American bullfrog in the Flemish region in Belgium. This approach is based on the close cooperation of scientists, policymakers, field managers and conservationists to create a science-based policy in the management of invasive alien species. Innovative applied research poses an important foundation in the steering process to establish efficient control measures. These are integrated in the management process that is coincided with raising awareness and dissemination of information throughout the whole plan. The results are based on 10 years of experience and cooperation in the management of the American bullfrog in Flanders, Belgium. The several stages of which this framework is built are crucial in the strategy to tackle the invasion in the most integrated way and can be transposed to control other invasive aquatic alien animals.

Functional assembly of grassland plant species in native communities in Spain and recipient communities in California

Abstract A major aim in invasion ecology is to understand the role of exotic species in plant communities. Whereas most studies have explored the traits of exotic species in the context of the introduced community, functional comparisons of entire assemblages of species in their native and introduced communities have rarely been analysed. Taking advantage of the unidirectional invasion of plant species of European origin (i.e. colonizers) into California, this study aims to investigate the relative importance of plant traits, environmental factors and invasion status in biological invasions. We compared the functional structure (i.e. trait composition and diversity) along resource availability gradients in recipient and native Mediterranean grassland communities in California and Spain, respectively. Traits were related to resource use in above‐ground and below‐ground organs and reproductive strategy. We also investigated how niche differences vary along environmental gradients between coexisting colonizer and native species assemblages within communities. There were clear differences in the functional structure of Mediterranean grassland communities between regions, which were associated with the resource availability gradient. Paradoxically, the most acquisitive communities occurred in resource‐poor sites, highlighting that rapid acquisition and use of resources permit species to cope with environmental stress through stress avoidance. In Spain, colonizer species had greater specific leaf area than non‐colonizers. Yet, differences between colonizer and non‐colonizer species in Spain for other traits were mostly absent and did not change along the gradient. This might be a result of the greater native species richness as a consequence of the agricultural practices that have taken place in Europe for millennia and reflect that the entire species pool of grasslands is adapted to agricultural landscapes. In comparison, in California, colonizer species were more acquisitive in their use of resources than natives under favourable conditions, but functionally converged in resource‐limited sites. Synthesis. These results underscore that the importance of niche differences between native and colonizer species as a community assembly mechanism is strongly subjected to the influence of habitat filtering. Trait comparisons are context dependent, and a correct interpretation of filtering processes in community assembly requires a regional perspective.

Estimating competition in metacommunities: accounting for biases caused by dispersal

Abstract Estimating the strength of interactions among species in natural communities has always been a challenge for empirical ecologists. Sessile organisms, like plants or corals, often occur in metacommunities where they compete only with their immediate neighbours but disperse propagules over a wider area. To estimate the strength of competitive interactions, ecologists often count abundances in cells on a spatial grid for at least two time‐points. This data is then analysed using regression, by modelling the change in population size as a function of local densities, using cells as independent data‐points: a technique known as space‐for‐time substitution. These analyses generate estimates of competition coefficients; however, the method ignores dispersal among cells. To determine the impact of ignoring dispersal, we derived the bias that would arise when we apply regression methods to a metacommunity in which a fraction of seeds disperse beyond their natal cells but this dispersal is ignored in the model fitting process. We present results from a range of population models that make different assumptions about the nature of competition and assess the performance of our bias formulae by analysing data from simulated metacommunities. We reveal that: estimates of competition coefficients are biased when dispersal is not properly accounted for; and the resulting bias is often correlated with abundance, with rare species suffering the greatest overestimation. We also provide a standardized metric of competition that allows the bias to be calculated for a broad range of other population models. Our study suggests that regression methods that ignore dispersal produce biased estimates of competition coefficients when using space‐for‐time substitution. Our analytical bias formula allows empirical ecologists to potentially correct for biases, but it requires either tailored experiments in controlled conditions or an estimate of the average dispersal rate in a natural community, so may be challenging to apply to real datasets.

Food web functional responses

This article reviews the nature of functional responses that have commonly been used to represent feeding relationships in the ecological literature. It compares these with the range of functional response forms that are likely to characterize species in natural communities. The latter set of responses involves many more variables. The article reviews the history of functional response models, and examines previous work that has allowed the functional response of a predator to a single type of prey to depend on additional variables beyond the abundance of that prey type. While a number of more complex functional responses have been discussed over the years, many variables affecting feeding rates are still typically omitted from models of food webs. The influences on functional responses from trophic levels above that of the predator or below that of the prey are particularly likely to be ignored, although models and data have suggested that they can have large effects on the functional response. The influences of adaptive behavior and of the time-scale of response measurement are also too often ignored. Some of the known and unknown consequences of these omissions are discussed.

More on the Spread of Nonnative Ferns in Georgia and the Southeastern United States

Relative to other vascular plants, ferns have been overlooked with respect to the potential for nonnatives to spread into natural areas and potentially displace native species. An unusual site in the Piedmont of northeast Georgia was found to harbor two species of nonnative ferns that have clearly become naturalized. A third species at the site represents the appearance in a natural setting of another nonnative fern species whose cultivars and hybrids are being more widely planted as ornamentals. Examination of herbarium specimens from Georgia and the Southeastern United States clarified the status of some earlier records and some overlooked records, based on misidentifications or questionable status as naturalized. The species involved (Arachniodes simplicior, Polystichum polyblepharum, and Anisocampium niponicum (=Athyrium niponicum)) are all introductions from temperate regions in East Asia and probably represent escapes from cultivation via spores. The appearance of these species in natural communities raises questions about their potential to spread farther and to become pests by crowding out native flora. The invasive potential of these three species and five other species discussed in a previous paper is evaluated based on field observations as well as information about their status as an epiphyte or ground dweller, reproductive plasticity, ecological requirements, and popularity as horticultural ornamentals.

An experimental test of stabilizing forces in the field niche.

Modern coexistence theory holds that stabilizing mechanisms, whereby species limit the growth of conspecifics more than that of other species, are necessary for species to coexist. Here, we used experimental and observational approaches to assess stabilizing forces in eight locally co-occurring, annual, legume species in the genus Trifolium. We experimentally measured self-limitation in the field by transplanting Trifolium species into each other's field niches while varying competition and related these patterns to the field coexistence dynamics of natural Trifolium populations. We found that Trifolium species differed in their responses to local environmental gradients and performed best in their home environments, consistent with habitat specialization and presenting a possible barrier to coexistence at fine scales. We found significant self-limitation for 5 of 42 pairwise species combinations measured experimentally with competitors absent, indicating stabilization through plant-soil feedbacks and other indirect interactions, whereas self-limitation was largely absent when neighbors were present, indicating destabilizing effects of direct plant-plant interactions. The degree of self-limitation measured in our field experiment explained year-to-year dynamics of coexistence by Trifolium species in natural communities. By assessing stabilizing forces and environmental responses in the full n-dimensional field niche, this study sheds light on the roles of habitat specialization, plant-soil feedbacks, and plant interactions in determining species coexistence at local scales.

甘肃南部7种高寒杜鹃生物量模拟

精确测定与模拟高山-亚高山灌丛生物量是了解陆地生态系统碳功能的重要基础工作。以甘肃南部高山-亚高山地区常见的7种高寒杜鹃（Rhododendron spp.）灌木为对象，通过标准植株收获法，建立易测因子与各器官生物量及总生物量的方程并检验拟合精度，筛选最优拟合方程。结果表明：（1）自变量和函数的类型对杜鹃生物量的模拟效果影响较大，700组方程中以D和D²H为自变量和以幂函数为模型拟合的R²相对集中、中位数都较高。（2）遴选出的35组单物种最优生物量模型的R²介于0.66-0.99之间、中位数为0.92，除山光杜鹃（Rh.oreodoxa）的茎、叶生物量和地上生物量模型为线性函数、麻花杜鹃（Rh.maculiferum）的所有模型为指数函数外，其余的生物量模型均为幂函数；D和D²H是单物种生物量模型的最佳预测变量，H仅是黄毛杜鹃（Rh.rufum）除根外、美容杜鹃（Rh.calophytum）叶生物量的最佳预测变量。（3）混合物种最优模型是以D²H为自变量的幂函数，除对叶生物量的模拟精度相对较低外，对其它生物量的模拟均较好。甘肃南部7种高寒杜鹃灌木生物量模型的建立为高寒地区灌丛生态系统碳汇功能的研究提供了支撑。;Rhododendron species are broad-leaved evergreen woody shrubs belonging to Ericaceae, and are an important constituent of alpine and subalpine ecosystems. Rh. species are endemic to Tibetan Plateau and surrounding areas. Unlike for trees, biomass estimation models are virtually lacking for Rh. species in natural communities. Therefore, accurate measurement and modeling of biomass for alpine-subalpine Rh. species is a fundamental work for quantifying carbon functions of terrestrial ecosystems. This study aimed to develop allometric models for the estimation of biomass storage of seven Rh. species' in the alpine-subalpine region of southern Gansu Province. Investigated species included Rh. rufum, Rh. przewalskii, Rh. alophytum, Rh. oreodoxa, Rh. taibaiense, Rh. capitatum and Rh. maculiferum. A total of 312 individuals were harvested for the measurements of above- and belowground biomass. Commonly used models, such as linear, logarithmic, power-law and exponential functions were used for estimating biomass, and basal diameter (D), height (H), canopy (C), crown volume (V) and square of basal diameter×plant height (D²H) from field measurements were used as independent variables, and leaf biomass, stem biomass, aboveground biomass, root biomass and total biomass were treated as dependent variables. Among a total number of 700 models tested, significant relationships were detected between biomass components and field measurements of predictors for the seven studied woody species (all P<0.01). Using D and D²H as independent variables and the power function resulted in a relatively narrow distribution and a high median of R² values. The R² values of the selected 35 optimal models for individual species from the 700 sets varied between 0.66 and 0.99, with a median of 0.92.The models for stem biomass, leaf biomass and aboveground biomass of Rh. oreodoxa were linear functions, for each of these biomass of Rh. maculiferum were exponential functions, while the rest of the biomass models were power functions. The plant height (H) was the best independent variable for the estimation of stem biomass, leaf biomass and aboveground biomass of Rh. rufum and leaf biomass of Rh. calophytum. The results also showed that the power function with D²H as the independent variable was the best model for mixed species, but the predictive power for leaf biomass was relatively low using the mixed-species' model. The establishment of seven alpine rhododendron shrub biomass models in southern Gansu Provide can serve as an important tool for the study of the carbon sink function of shrub ecosystems in alpine regions. In addition, these models may be applied to Rh. woodland elsewhere in eastern Tibetan Plateau.

THE COMPOSITION AND CONTENT OF PHENOLIC COMPOUNDS IN THE LEAVES OF A POTENTIALLY INVA-SIVE SPECIES PHYSOCARPUS OPULIFOLIUS (L.) MAXIM. AND ITS ORNAMENTAL CULTIVARS

The expansion of alien plant species in natural communities is now taking a global scale. Since most invasive plants have economically valuable properties, many researchers agree that these plants must be used as new sources of biological resources. The composition and content of biologically active compounds were studied in the leaves of potentially invasive species of Novosibirsk – Physocarpus opulifolius (L.) Maxim. and its ornamental cultivars Ph. opulifolius ‘Diabolo’, Ph. opulifolius ‘Luteus’ by the method of High-Performance Liquid Chromatography. For the first time an analysis of phenolic profiles of introduced, self-sown and cultivated Ph. opulifolius plants has been performed. Presence of 22 phenolic compounds represented by several groups of substances with predominating flavanols (hyperoside, rutin, astragalin and quercetin) has been established. Avicularin has been only revealed in the leaves of cultivars. The sum of identified flavonols greatly varies in different samples, the highest content is in the cultivar Ph. opulifolius ‘Diabolo’ (14.68 mg/g) and self-sown plants of Ph. opulifolius (14.22 mg/g). The content of the sum of identified flavons (vitexin, isovitexin, baicalin) and phenolic acid (сhlorogenic and caffeic acids) is almost the same in all Ph. opulifolius samples under study. The data obtained will allow to widen the idea of the resource potential of the aggressive invasive species and its ornamental cultivars in the secondary areal.

Pilferer, murderer of innocents or prey? The potential impact of killer shrimp (Dikerogammarus villosus) on crayfish

Freshwater ecosystems worldwide are facing the establishment of non-native species, which, in certain cases, exhibit invasive characteristics. The impacts of invaders on native communities are often detrimental, yet, the number and spread of non-native invasive species is increasing. This is resulting in novel and often unexpected combinations of non-native and native species in natural communities. While the impact of invaders on native species is increasingly well-documented, the interactions of non-native invaders with other non-native invaders are less studied. We assessed the potential of an invasive amphipod, the killer shrimp Dikerogammarus villosus (Sowinsky, 1894), to cope with other established invaders in European waters: North American crayfish of the Astacidae family—represented by signal crayfish Pacifastacus leniusculus (Dana, 1852), and the Cambaridae family—represented by marbled crayfish Procambarus virginalis Lyko, 2017. The main goal of this study was to investigate if killer shrimp, besides their role as prey of crayfish, can significantly influence their stocks by predating upon their eggs, hatchlings and free-moving early juveniles. Our results confirmed that killer shrimp can predate on crayfish eggs and hatchlings even directly from females abdomens where they are incubated and protected. As marbled crayfish have smaller and thinner egg shells as well as smaller juveniles than signal crayfish, they were more predated upon by killer shrimp than were signal crayfish. These results confirmed that the invasive killer shrimp can feed on different developmental stages of larger freshwater crustaceans and possibly other aquatic organisms.

Pollen grain size associated with pollinator feeding strategy.

Angiosperm pollen grain diameter varies greatly from a few microns to over 100, but the selective forces driving the interspecific variation in pollen size remain unclear. Although both pre- and post-pollination hypotheses have been proposed, empirical evidence remains scarce. Here we propose that visits by pollen-foraging pollinators have selected against large pollen grains. An association between pollinator behaviour and pollen grain size was confirmed by field studies of 80 flowering species in natural communities, showing that pollinators positively collected pollen in those species with relatively smaller pollen grains but rarely did so in species with larger ones. Allowing for the confounding effects of pollinator type, flower size or style length and pollen grain number, we found a significant effect of pollen-foraging behaviour on variation in pollen grain size, particularly in bee-pollinated plants. While these results suggest that many plant species whose pollen is collected or consumed by pollinators produce small pollen grains, it remains unclear whether pollen grain size is directly affected by pollinator foraging habit or indirectly mediated by pollen number trade-offs.

Being popular or freak: how alien plants integrate into native plant-frugivore networks

The generalist diet of most frugivores opens a window of opportunity to the invasion of alien plants whit fleshy-fruits. The outcome of the new relationships between alien plants and native frugivores depends both on traits of the invaders and of the mutualist partners in the recipient community. Two contrasting hypotheses attempt to explain the integration of alien species in native communities. “Darwin’s naturalization hypothesis” proposes that alien species more different from native species are more likely to integrate in the community. The “similarity hypothesis” proposes the opposite, that alien species more similar to native species are more likely to integrate the native community. By comparing chemical and morphological traits of 12 alien and 48 native fleshy-fruited species, we tested both hypothesis as assembly rules of alien species in subtropical Andean forests. We did not find differences in most chemical or morphological traits between alien and native fruit species. The multidimensional variation of alien fruit traits was nested within that of native species. However, alien fruits tended to score high in the range of variation of native chemical traits. Accordingly, we propose the “fraction similarity hypothesis” as a main force that drive the assembly of alien species in mutualistic networks, i.e. alien species benefit from existing mutualistic interactions that involve fruit species with traits selected by the frugivores to invade native communities. The striking similarity in fruit traits between alien and native species highlights the potential role of seed dispersers as ecological filters to the invasion of alien plants. In turn, this similarity suggests that alien fruits can be functionally equivalent to native ones in terms of their interaction with fruit-eating birds.

Coexistence of many species in random ecosystems.

Rich ecosystems harbour thousands of species interacting in tangled networks encompassing predation, mutualism and competition. Such widespread biodiversity is puzzling, because in ecological models it is exceedingly improbable for large communities to stably coexist. One aspect rarely considered in these models, however, is that coexisting species in natural communities are a selected portion of a much larger pool, which has been pruned by population dynamics. Here we compute the distribution of the number of species that can coexist when we start from a pool of species interacting randomly, and show that even in this case we can observe rich, stable communities. Interestingly, our results show that, once stability conditions are met, network structure has very little influence on the level of biodiversity attained. Our results identify the main drivers responsible for widespread coexistence in natural communities, providing a baseline for determining which structural aspects of empirical communities promote or hinder coexistence.

Resource limitation alters effects of phenological shifts on inter-specific competition.

Phenological shifts can alter the relative arrival time of competing species in natural communities, but predicting the consequences for species interactions and community dynamics is a major challenge. Here we show that differences in relative arrival time can lead to predictable priority effects that alter the outcome of competitive interactions. By experimentally manipulating the relative arrival time of two competing tadpole species across a resource gradient, we found that delaying relative arrival of a species reduced the interaction asymmetry between species and could even reverse competitive dominance. However, the strength of these priority effects was contingent on the abundance of the shared resource. Priority effects were generally weak when resources were limited, but increased at higher resource levels. Importantly, this context dependency could be explained by a shift in per capita interaction strength driven by a shift in relative body sizes of competitors. These results shed new light into the mechanisms that drive variation in priority effects and help predict consequences of phenological shifts across different environments.

Related herbivore species show similar temporal dynamics.

Within natural communities, different taxa display different dynamics in time. Why this is the case we do not fully know. This thwarts our ability to predict changes in community structure, which is important for both the conservation of rare species in natural communities and for the prediction of pest outbreaks in agriculture. Species sharing phylogeny, natural enemies and/or life-history traits have been hypothesized to share similar temporal dynamics. We operationalized these concepts into testing whether feeding guild, voltinism, similarity in parasitoid community and/or phylogenetic relatedness explained similarities in temporal dynamics among herbivorous community members. Focusing on two similar datasets from different geographical regions (Finland and Japan), we used asymmetric eigenvector maps as temporal variables to characterize species- and community-level dynamics of specialist insect herbivores on oak (Quercus). We then assessed whether feeding guild, voltinism, similarity in parasitoid community and/or phylogenetic relatedness explained similarities in temporal dynamics among taxa. Species-specific temporal dynamics varied widely, ranging from directional decline or increase to more complex patterns. Phylogeny was a clear predictor of similarity in temporal dynamics at the Finnish site, whereas for the Japanese site, the data were uninformative regarding a phylogenetic imprint. Voltinism, feeding guild and parasitoid overlap explained little variation at either location. Despite the rapid temporal dynamics observed at the level of individual species, these changes did not translate into any consistent temporal changes at the community level in either Finland or Japan. Overall, our findings offer no direct support for the notion that species sharing natural enemies and/or life-history traits would be characterized by similar temporal dynamics, but reveal a strong imprint of phylogenetic relatedness. As this phylogenetic signal cannot be attributed to guild, voltinism or parasitoids, it will likely derive from shared microhabitat, microclimate, anatomy, physiology or behaviour. This has important implications for predicting insect outbreaks and for informing insect conservation. We hope that future studies will assess the generality of our findings across plant-feeding insect communities and beyond, and establish the more precise mechanism(s) underlying the phylogenetic imprint.

Phylogenetic relatedness of native and exotic plants along climate gradients in California, USA

AbstractAimOne hypothesis of Darwin's naturalization conundrum, the pre‐adaptation hypothesis, proposed that exotics that are more closely related to species in native communities might be more successful invaders because close relatives share similar traits and might be favoured in similar environments. We test this prediction using regional angiosperm assemblages that have been heavily invaded by exotic species and relating patterns of phylogenetic relatedness to potential environmental drivers—temperature and precipitation.LocationCalifornia, USA.MethodsUsing a massive, dated phylogeny of angiosperm plants, we assessed differences in phylogenetic structure between native, naturalized exotic and full floras of 35 bioregions in California. We quantified phylogenetic relatedness using the net relatedness index (NRI) and the nearest taxon index (NTI) at varying phylogenetic extent. We measured changes in phylogenetic structure using a metric (phylogenetic relatedness anomaly), which is calculated as the phylogenetic relatedness of the full flora of a bioregion minus that of the native flora of the bioregion. We assessed correlations between phylogenetic structure measures and temperature or precipitation.ResultsIn general, introduction of exotic species decreased phylogenetic clustering when considering NRI but increased phylogenetic clustering when considering NTI. However, patterns of phylogenetic relatedness for some families were opposite to those for other families (e.g., NRI anomalies for Amaranthaceae, Caryophyllaceae, Fabaceae and Poaceae were opposite to those for Brassicaceae, Asteraceae and all angiosperms combined). Native communities were more phylogenetically clustered in dry regions, while exotic phylogenetic structure was less clearly related to climate.Main conclusionsExotic species tend to come from clades that are poorly represented but not completely absent from the native flora. Within families, NTI patterns tended to be fairly similar between native and exotic species, suggesting shared responses to the environment, particularly temperature and precipitation, in these two groups.