Ruderal Strategy Research Articles

Seaweed functional strategies, functional groups, and taxon dynamics through a 213-year historical series of Rio De Janeiro Bay

From Darwin’s visit to nowadays, we analyzed the changes in species- and genus-level richness and turnover, equity, diversity, composition, as well as functional group and functional strategy dynamics over a 213-year historical series of the seaweed assemblage from Rio de Janeiro Bay. We developed new analysis methods to serve as a protocol for worldwide functional and bioindicator assessment of seaweed assemblages. Over the two centuries of changes tracked, the integration of taxonomic, functional group, and functional strategy analyses unraveled a trajectory of seaweed assemblage restructuring under human disturbance. Our taxonomic analyses showed a high species and genus turnover and a decline in richness, with the local extinction of the Sargassum genus, responsible for warm temperate kelp forests in the Western Atlantic. Seaweed functional group data presented a trend of morphological simplification and miniaturization, with the decline of marine forest canopy and subcanopy-forming groups favoring filamentous and crustose algae dominance. Functional strategy data showed the historical decline of competitive structuring as an assemblage driver in favor of disturbance and stress-structuring, as highlighted by the competitive strategy decrease, coupled with stress-tolerant and ruderal strategies rise across metrics. These changes were successfully portrayed by the new ecological index we proposed, the C/SR index. It is the first quantitative index for seaweed assemblages, designed to be a trackable metric for conservation, monitoring, and restoration efforts.

CSR strategies seasonal cycling: A new mechanism for coexistence among seaweeds

The stable maintenance of high biological diversity remains a major puzzle in biology. We propose a new mechanism involving the cyclical use of Competitive, Stress-tolerant, and Ruderal (CSR) strategies to explain high biodiversity maintenance. This study examines the interactions among three morphs of the cosmopolitan and commercially important seaweed Ulva Linnaeus. We measured biomass productivity, effective quantum yield, carbohydrate concentration, and nutrient competition across all seasons for one year and matched trait value combinations to CSR strategies. Our findings reveal that the Ulva morphs exhibited significant competitive interactions under eutrophic conditions, in a scramble competition dynamic. However, competition did not significantly affect their functional traits under naturally prevalent oligotrophic conditions. Season-by-season analysis revealed that each morph employed temporal niche partitioning by cyclically adopting different CSR strategies, thereby avoiding direct competition. This cyclical strategy, akin to a rock-paper-scissors game, prevents any single strategy from dominating year-round, maintaining the three-morph polymorphism. Our study further highlights the importance of year-long functional trait measurements to encompass seasonal changes in functional responses. Our CSR cycling conceptual model offers new insights useful for monitoring and conservation efforts.

Variation in CSR plant strategies along soil and climate gradients: A comparison between rocky outcrops and nearby rangelands

AbstractQuestionRocky outcrops in mountains represent unique ecosystems characterized by a series of stress‐inducing features on living organisms. Despite numerous studies focusing on plant diversity and species community composition in these ecosystems, less attention has been given to understanding plant strategies in response to their challenging environment. This is essential, especially considering the existence of numerous endemic species facing climate change and human disturbances.LocationThe study was conducted in six sites located in rocky outcrops and their nearby rangelands across a rainfall gradient (160–910 mm) and under different soil fertility levels in northern Iran.MethodsWe used competitor, stress tolerator and ruderal (CSR) strategies as functional groups to examine the responses of plant communities to environmental variation. The composition of plant species and functional traits were evaluated in ninety 1‐m2 plots. The influence of 10 soil and 5 bioclimatic factors on CSR plant strategies was examined along the rainfall gradient.ResultsOur results showed changes in CSR strategies from stress‐tolerant species (S) in rocky outcrops toward intermediate strategies (S/CSR) in rangelands. Soil organic carbon, electrical conductivity and sand were consistently correlated with shifts from S towards C and R strategies in rangelands. Silt and sodium (Na) affected the presence of S strategies in outcrops. The stressful conditions induced by a fine soil texture and Na in outcrops were particularly effective in establishing the dominance of the S strategy.ConclusionsWe identified patterns of shifts in CSR plant strategies that align with changes in environmental gradients. Although stress‐tolerant species (S) were the dominant strategy in most cases, this shifted towards intermediate strategies (SR and CSR) under more benign environmental conditions. In outcrops, these changes were primarily aligned with soil parameters, whereas in rangelands, both soil and climate variables were correlative. However, these correlations varied between soil and climate factors, as well as between outcrop and rangeland landscapes.

Cenomanian terrestrial paleoenvironments from the Bohemian Cretaceous Basin in Central Europe and their implications for angiosperm paleoecology

In this paper, we reconstruct the vegetation communities of five terrestrial paleoenvironments from the Cretaceous (Cenomanian) Peruc-Korycany Formation of the Bohemian Cretaceous Basin in Czechia. Reconstructions are based on a synthesis of numerous studies of paleobotany, palynology, paleoecology, sedimentology and geochemistry analyses. Ordered in a transect from coastal marine settings to elevated hinterland regions, paleoenvironments and plant assemblages are reconstructed as follows: (1) Saltmarsh vegetation comprising a Frenelopsis-Classopollis assemblage; (2) Coastal freshwater swamp vegetation comprising a Cunninghamites-Taxodiaceaepollenites assemblage; (3) Meandering river floodplain vegetation comprising a Myrtophyllum-Perucipollis assemblage; (4) Braided river floodplain vegetation comprising a Eucalyptolaurus-Mauldinia assemblage; and (5) Vegetation of drier upland areas comprising fern prairies with angiosperms and Bennettitales - a Zamites-Ephedripites assemblage. Our study shows that in Cenomanian times, angiosperms were diversified, particularly in alluvial plains, where lauroid and platanoid angiosperms prevailed. Comparison of these Cenomanian paleoenvironments in Czechia with other Cenomanian paleoenvironments across Europe show a widespread dominance of angiosperms in the vegetation of alluvial plains across much of the continent. This contrasts with Barremian-Albian times when angiosperms occupied only disturbed habitats, and our findings suggest that angiosperm exchanged a ruderal (disturbed) strategy for a competitive strategy during the Albian-Cenomanian transition. Conversely, conifers dominated alluvial plains in Early Cretaceous times, while they rose to dominate saltmarshes and swamps in the Bohemian Cenomanian, exchanging a competitive strategy for a stress-tolerant strategy.

Temporal dynamics of Grime's CSR strategies in plant communities during 60 years of succession.

Grime's competitive, stress-tolerant, ruderal (CSR) theory predicts a shift in plant communities from ruderal to stress-tolerant strategies during secondary succession. However, this fundamental tenet lacks empirical validation using long-term continuous successional data. Utilizing a 60-year longitudinal data of old-field succession, we investigated the community-level dynamics of plant strategies over time. Our findings reveal that while plant communities generally transitioned from ruderal to stress-tolerant strategies during succession, initial abandonment conditions crucially shaped early successional strategies, leading to varied strategy trajectories across different fields. Furthermore, we found a notable divergence in the CSR strategies of alien and native species over succession. Initially, alien and native species exhibited similar ruderal strategies, but in later stages, alien species exhibited higher ruderal and lower stress tolerance compared to native species. Overall, our findings underscore the applicability of Grime's predictions regarding temporal shifts in CSR strategies depending on both initial community conditions and species origin.

Environmental filtering is the primary driver of community assembly in forest–grassland mosaics: A case study based on CSR strategies

AbstractAimsEcological strategies can provide information about plant community assembly and its main drivers. Our aim was to reveal the dominant strategies of the vegetation types of forest–grassland mosaics and to deduce the assembly processes responsible for their species composition.LocationHungary.MethodsWe investigated eight vegetation types of Hungarian forest–steppes. The trade‐off between three key traits related to leaf size and economics was used to calculate Grime's competitive–stress tolerance–ruderal (CSR) value for each species, based on which the mean value for each vegetation type was determined. Detrended correspondence analysis (DCA) ordination was used to reveal the compositional differences among the vegetation types under study. To analyze how ecological strategies correlate with the compositional gradient, we used linear regression between plot ordination scores (the first DCA scores) and each strategy (C, S, and R). Linear mixed‐effect models were used to evaluate the differences between the vegetation types regarding each strategy (C, S, and R).ResultsEach vegetation type was dominated by the stress‐tolerator strategy, indicating the prominent role of environmental filtering in community assembly. However, ecological strategies differed significantly among the communities. The importance of the stress‐tolerator strategy decreased toward the less harsh end of the gradient (i.e., from grasslands to forests), while the competitor strategy showed a reverse pattern. The ruderal strategy was weakly correlated with the gradient, although its proportion increased toward the harsh end of the gradient.ConclusionsWith ongoing climate change, an increasing importance of environmental filtering is expected in the assembly of the vegetation types in the studied forest–grassland mosaics. We suggest that CSR strategies offer a useful tool for studying plant‐community assembly rules along environmental gradients.

Influence of local environmental gradients on ecological strategies of herbaceous communities in riverine side channels

AbstractQuestionsIn riverine side channels (secondary and former arms), the alternation of lotic, lentic and dry phases produces disturbance and resource gradients that filter species and community strategies. To better understand the impact of this alternation of functioning on plant communities at a fine spatial scale, we tested for the effects of elevation (linked to water level), slope, longitudinal position, light availability and sediment grain size on (i) taxonomic composition and (ii) competition, stress tolerance, and ruderal strategies (C, S and R strategies) at the community level. We hypothesized that fewer resources would increase the stress‐tolerant prevalence (i.e., community‐weighted mean value), while topographic gradients would affect ruderal prevalence. In addition, we hypothesized that strong and directional environmental filtering should reduce the co‐occurrence of species with different CSR strategy values (i.e., low C, S and R functional dispersion).LocationFourteen side channels on the lower reach of the Loire river (France).MethodsTaxonomic composition of the herb layer and environmental variables were assessed on 474 plots. The relations between species composition and environmental gradients were investigated by a constrained analysis of principal coordinates. The effects of environmental gradients on community CSR strategies were assessed using mixed‐effects models and a model‐averaging procedure.ResultsTaxonomic community composition was shaped mainly by light availability, topographic elevation and sediment grain size. Slope and the interaction between light and elevation influenced the community‐weighted mean and functional dispersion values of S and R strategies. Among other interactions, those involving sediment grain size shaped the dispersion values for C and R strategies.ConclusionThe study identified shading and fine sediment grain size as key drivers of biotic homogenization in the riverscape. Increasing the disturbance frequency and magnitude would limit the progression of the ecological succession and favor the co‐occurrence of taxonomically and functionally diverse communities within the side channels.

Community-level differentiation of Grime's CSR strategies along a post-abandonment secondary successional gradient

Understanding the ecological processes and the mechanisms of community assembly during secondary succession of vegetation has been a central topic of ecological research. In the last decades, it has also been rendered as a necessity for wildlife management due to the ongoing vegetation succession caused by land abandonment in many parts of the world. Here, we investigated the taxonomic and life strategies diversity patterns among vegetation communities representing a large part of a natural succession gradient, in a (sub-) mountainous area of northwestern Greece (northern Pindus). Sampling of grassland and forest vegetation plots was conducted across an area submitted to high levels of land abandonment during the last 70 years, accompanied with sampling of new functional trait data. The Grime's CSR model of plant strategies was employed to investigate functional diversity of communities, while climatic, edaphic and topographic factors were employed to identify potential drivers of alternative life strategies diversity. Additionally, alpha and beta taxonomic and life strategies diversity of communities were calculated. Variation partitioning analyses attributed functional and taxonomic differentiation of communities mainly to the legacy of land use cover. Overall, grasslands and forests were functionally differentiated, with forest communities having higher levels of the competitive strategy, and grasslands having higher levels of the ruderal strategy. Nevertheless, parallel trends of occurrence of plant life strategies were found for both grasslands and forests. Community level competitive and stress-tolerating plant life strategies were found to be strongly and negatively correlated with soil organic content, soil nitrogen, soil pH and slope, while ruderalism was largely related to the disturbance regime of each community. The derived information of functional strategies diversity can provide valuable data that can guide management actions and contribute to the optimization of systematic conservation planning in such high nature value and threatened ecosystems.

Non-native vascular flora of alpine areas in the White Mountains, New Hampshire, USA

ABSTRACT Arctic-alpine vegetation in the eastern United States is unique to northern New England and New York and is disjunct from similar areas in eastern Canada. We present the first study of the non-native flora in the region, specifically focusing on New Hampshire’s White Mountains. By combining literature and herbaria searches, field surveys, and a seventeen-year evaluation at an alpine hut in a hypothesis-driven framework, we document the composition, chronology, and persistence of non-native plant species establishments, regress richness in relation to elevation and disturbed area, and evaluate similarities to nineteen other alpine floras globally. Our results indicate that the White Mountains support one of the most species-rich non-native alpine floras known in the world, with 58 species detected at thirty-one sites since 1874, comprising 19 percent of 300 species documented in New Hampshire’s 22 km2 of alpine tundra. There is a negative relationship between non-native alpine plant richness and elevation along a mountain road on Mt. Washington. Moreover, elevation predicts richness per unit area in proximity to clusters of built structures in alpine areas. The compositions, geographic origins, and dominant ruderal strategies of non-native species are similar to those of Arctic and other alpine non-native floras globally. Sørenson similarity index and nonmetric multidimensional scaling ordination of twenty alpine regions reveals the White Mountains have highest similarity with widely separated mountain regions in Australia, Hawaii, the Rocky Mountains, the Andes, Southern Africa, and Iceland, driven by shared species of Eurasian origin. We report the unexpected discovery of Plagiobothrys hispidulus, a borage native to western North America not previously reported from New Hampshire. These findings have important implications for managers of alpine areas in eastern North America and may facilitate the early detection, monitoring, and control of non-native species, minimizing their establishment and spread.

Plant water use related to leaf traits and CSR strategies of 10 common European green roof species

The vegetation layer contributes to multiple functions of green roofs including their hydrological function as plants remove water from substrates between rainfall events through evapotranspiration, restoring the green roofs storage capacity for rainfall retention. While individual traits have been related to water use strategies of green roof plants, these traits are inconsistent, suggesting the importance of trait combinations which may be reflected in CSR (competitor, stress tolerator, ruderal) strategies. Therefore, relating plant water use to leaf traits and CSR strategies could help facilitate green roof plant selection into new geographical regions where green roof technology is developing. For example, in high latitude northern European regions with long daylight during the growing season. Growth (shoot biomass, relative growth rate and leaf area), leaf traits (leaf dry matter content, specific leaf area and succulence) and CSR strategies were determined of 10 common European green roof plants and related to their water use under well-watered (WW) and water-deficit (WD) conditions. All three succulent species included in the experiment showed mostly stress tolerant traits and their water loss was less than the bare unplanted substrate, likely due to mulching of the substrate surface. Plants with greater water use under WW conditions had more ruderal and competitive strategies, and greater leaf area and shoot biomass, than species with lower WW water use. However, the four species with the highest water use under WW conditions were able to downregulate their water use under WD, indicating that they could both retain rainfall and survive periods of water limitations. This study indicates that, for optimal stormwater retention, green roof plant selection in high latitude regions like northern Europe, should focus on selecting non-succulent plants with predominantly competitive or ruderal strategies to make the most of the long daylight during the short growing season.

Characterization of an Italian landrace of Cyclanthera pedata (L.) Schrad. of herbal and horticultural interest

Caigua (Cyclanthera pedata (L.) Schrad.) is a native species of the Andes. Its fruits are recently gaining attention as herbal and healthy product. A landrace of Caigua traditionally cultivated in Camonica Valley (Italian Alps), called “Ciuenlai” (or “Milione/Milioncino”), is almost unknown. For this reason, the phytochemical, nutritional and ecological (functional strategy) characterization of “Ciuenlai” was carried out. Phytochemical and nutritional analyses were performed considering its fruits, leaves, sprouts, and seeds, and compared with commercial South American plant material. Fruits of “Ciuenlai” showed a similar content of phenolic compounds but a lower content of saponins and flavanones and dihydroflavonols than the comparison samples. Conversely, the content in caffeoylquinic acid (frequently considered a quality marker for herbal use) was four times higher for “Ciuenlai” (0.64 ± 0.04%) comparing with the commercial variety grown in the same area (0.15 ± 0.01%). Interestingly, leaves and sprouts of “Ciuenlai” resulted rich in secondary metabolites, including saponins and flavanones and dihydroflavonols, suggesting that these parts could be eligible for herbal use. Considering the ecological and agronomical features, “Ciuenlai” showed a more ruderal strategy, and different growth, producing more fruits earlier in the season, much smaller than the South American variety. “Ciuenlai” could have developed an ecological adaptation to the peculiar climatic conditions of the mountain areas of Camonica Valley, different from the native area. The herbal use of “Ciuenlai” could be a useful strategy for its valorisation, other than the promotion of this product as typical food.

Effects of grazing versus mowing on the vegetation of wet grasslands in the northern Pre‐Alps, Switzerland

AbstractQuestionWet grasslands are among the most threatened habitats in Central Europe and are subject to loss of their unique species assemblages. Grazing and mowing are important conservation management tools for such semi‐natural habitats. The aim of this study was to investigate and compare the influence of grazing and mowing on the diversity and species composition of wet grassland vegetation.LocationMontane wet grasslands in the Gantrisch Nature Park, Switzerland.MethodsWe sampled 18 pairs of vegetation plots along land‐use borders between grazing and mowing (fence‐line contrasts), distributed over six fens, mostly belonging to the phytosociological alliance Calthion palustris. We tested for differences in structural parameters, biodiversity indices, mean ecological indicator values and the frequency of individual species. In addition, a detrended correspondence analysis was carried out.ResultsManagement type had no influence on species richness, Shannon index or Shannon evenness. Maximum microrelief, vegetation height, mean nutrient indicator value and mean competitive strategy were significantly higher with grazing, whereas the mean aeration indicator value and the mean ruderal strategy were significantly higher with mowing. Cirsium oleraceum, Filipendula ulmaria, Geum rivale and Juncus effusus, species of nutrient‐rich wet meadows, were more frequent under grazing, whereas mowing favoured grassland species with wide ecological amplitude, such as Plantago lanceolata and Trifolium pratense.ConclusionsAt the plot scale, vascular plant diversity did not differ between these management regimes. Thus, from the conservation point of view, in the study region, there is no clear preference for either management type, and both should be eligible for subsidies. At the landscape scale, it is beneficial to have both management types present to ensure high gamma‐diversity, as they favour different species.

The CSR strategies of alpine plants and community functional diversity in the Eastern Qinghai-Tibetan mountains

Many alpine communities of the Tibetan plateau experience both harsh climates and heavy grazing, and the adaptations to such environment are realized in plant functional traits and strategies. We tested, which leaf traits allow to dominate in the two wide-spread alpine communities of the Eastern Qinghai-Tibetan mountains, Kobresia alpine meadows and alpine fens, and do meadows and fens differ by community-weighted dominance-linked traits, strategy affinities, and functional diversity. Lower leaf dry matter content (LDMC) and higher specific leaf area (SLA) provides the species dominance in Kobresia alpine meadows, while size traits do not influence the dominance. Both LDMC and SLA have low functional evenness and divergence in the two communities. The prevail of stress-tolerators reflects the abiotic environment of alpine plants, but high affinities to ruderal strategy are possibly related to grazing.

Alien species affect the abundance and richness of native species in tropical forests: The role of adaptive strategies

AbstractUnderstanding the role of alien species in forest communities, and how native and alien species interact to shape the composition and structure of contemporary forests, is of critical importance to invasion ecology and natural resource management. We used vegetation data collected over a 20‐year period in 341 permanent plots representing remnants of closed‐canopy forests and post‐agricultural secondary forests across Puerto Rico to compare changes in the composition and abundance of native and alien woody species in plots with and without aliens across different forest types and to assess whether aliens and natives show divergence or convergence regarding functional roles and ecological strategies. We also tested the applicability of Grime's CSR (competitive, stress‐tolerant, and ruderal strategies) theory to explain naturalization success. Species richness and abundance of natives are consistently lower in plots in which aliens are present compared with those without them. This negative association between aliens and natives has been consistent over the 20 years and across all forest types. Both native and total richness slightly increased over the 20 years, but the increase in native species richness was three times lower in plots with aliens relative to those without aliens. The CSR classification provided insight into the naturalization success of aliens. Corroborating the “join the locals” hypothesis, aliens use the same functional spaces as natives. The exception is in dry forests, where aliens and natives differ in the use of functional spaces, a result that corroborates the “try harder” hypothesis. Generally, aliens were better competitors compared with natives, and natives were more stress‐tolerant than aliens. Our combined results suggest that alien species may inhibit population growth or even drive local changes in native plant communities by transforming the assembly and dynamics of tropical forests. Ultimately, modifications linked to invasive species may have significant implications for local forests, affecting their regeneration and productivity. More definitive conclusions require additional plot censuses, and analyses of disturbance regimes and stand‐age structure to reveal the long‐term implications of alien species on regenerating tropical forests, including their vulnerability, resilience, and adaptive capacity to cope with various aspects of climate change.

Taxonomic, functional, and phylogenetic diversity of communities hosting Ionopsidium savianum (Brassicaceae) growing on serpentine and limestone substrates

We analysed two different plant communities hosting Ionopsidium savianum (Brassicaceae), a species of EU interest included in the Habitats Directive 92/43/CEE annexes, for which specific studies on the ecology of communities where the species grows are lacking and more in-depth knowledge is needed. We examined two important sites of occurrence of this species in Tuscany with different soil types, namely limestone (Mt. Calvi) and serpentine (Mt. Pelato), to determine the structural and functional profile of the communities hosting this species in such different contexts. At each site, we surveyed the plant communities with I. savianum in ten 1 m2 quadrats to determine information on communities' species composition and total plant cover, as well as taxonomic (species richness, and Shannon H’ index), phylogenetic (phylogenetic diversity, mean nearest taxon distance and mean pairwise distance) and functional diversity (focusing on Rao’s Q, leaf functional traits and adaptive strategies community weighted mean). We took into account site location, soil type, slope aspect and microrelief as plot-level environmental factors. The two communities were highly diverging from multiple points of view. Differences were in species composition, richness and diversity, with Mt. Calvi hosting higher diversity. The indices of phylogenetic diversity were influenced significantly by site and microrelief, allowing the presence of peculiar niches occupied by the fern Asplenium ceterach. From the functional point of view, communities at Mt. Calvi showed a higher functional diversity and a higher specific leaf area. Plant height was influenced by the slope aspect and was higher on north-facing slopes. In terms of Grime’s adaptive strategies, the Mt. Pelato communities resulted to be more stress tolerant than those surveyed at Mt. Calvi. Here, a decrease in stress-tolerant strategy associated with an increase in ruderal strategy was detected in communities on north-facing slopes.

Adaptive strategy biases in engineered ecosystems: Implications for plant community dynamics and the provisioning of ecosystem services to people

Abstract Plant communities in green stormwater infrastructure (GSI) such as biofilters play an integral role in ecosystem services provisioning, such that many design manuals now feature plant lists that guide vegetation selection. This study looks at the implications of those lists for biofilter plant communities and their services, focusing on (1) how plants are selected across US climate zones, (2) whether selected plants exhibit adaptive strategy biases (i.e. towards competitive, stress tolerant or ruderal strategies that might impact ecosystem services provisioning) and (3) whether human‐induced selection or natural climatic processes underly any biases revealed. Our results suggest that biofilter plant strategies are significantly biased towards stress tolerance or competitiveness (depending on the climate zone) and away from ruderalness relative to the broader pool of native and wetland‐adapted native species. Competitive bias was evident in humid‐continental climates and stress‐tolerant bias in hot coastal/arid climates, with some degree of anti‐ruderal bias present across all zones. These biases are correlated with human concerns related to water availability and climate (water conservation; p < 0.05, irrigation; p < 0.1, climate extremes; p < 0.1). They do not appear to reflect strict climatological limits (i.e. limits that are independent of preferences or design constraints imposed by people) because they are not also evident for native plants. The benefits and costs of relaxing these biases are discussed, focusing on the implications for water quality, hydrologic, and cultural services provisioning and the dynamicity of GSI ecosystems, particularly their capacity to self‐repair, a prerequisite for the development of self‐sustaining GSI. Read the free Plain Language Summary for this article on the Journal blog.

The leaf anatomical trade-offs associated with plant ecological strategy variation

Plant functioning depends on variation in resource economics traits (acquisition vs. conservation) and the size of plants and their parts (the ‘global spectrum of plant form and function’). The anatomical basis of single traits (e.g., leaf mass per area; LMA) is generally understood, but little is known regarding the relationship between anatomical trade-offs and ecological strategies (representing integrated suites of traits). We hypothesised correlations between the relative extent of leaf tissue types and Grime’s Competitor Stress-tolerator Ruderal (CSR) strategies, principally a trade-off between structural (mechanical/fibro-vascular) vs. photosynthetic (chlorenchyma and intercellular airspace; ICAS) tissues, for ecologically contrasting herbaceous angiosperms in northern Italy. Specifically, that in the lamina portion, the trade-off represents the economics spectrum (S-R selection), but in the midvein portion, it reflects the mechanical constraints inherent to supporting large leaves (i.e., varies with C-selection). We used microscopy and image analysis to determine the relative cross-sectional area of tissues from transverse leaf sections (lamina and midvein portions) of angiosperms of contrasting CSR strategies. Principal components analysis (PCA) determined that the main trade-off (PCA1) was between mechanical/fibro-vascular tissues vs. ICAS/epidermis/chlorenchyma, but that this was associated with the economics spectrum (R- to S-selection) in the lamina, and with size (C-selection) for the midvein. A secondary trade-off in both lamina and midvein portions involved ICAS (i.e., the internal gas diffusion pathway) vs. chlorenchyma/epidermis (light capture), associated with S- to R-selection, respectively. Our results confirm the expectation that ecological strategy variation has a basis in underlying trade-offs between tissues with contrasting metabolic/architectural (i.e., economics/size-related) roles.

Consistent response of weeds according to Grime's CSR strategies along disturbance and resource gradients in Bordeaux vineyards

AbstractVineyards are an appropriate model for testing the filtering effect of management practices on weed communities, as a wide range of practices (tillage, herbicides and mowing) is implemented. The aim of this study is to highlight which trait values are selected by each practice in different environmental conditions, with special references to Grime's CSR strategies. A combination of a multivariate analysis (RLQ) and the fourth‐corner analysis was used to analyse 400 floristic samples belonging to 100 vineyards in the wine‐growing region of Bordeaux (France). The main structure of vineyard weed communities was shaped by the opposition between mowing, favouring hemicryptophytes with a competitive strategy, and soil tillage, favouring therophytes and nutrient‐demanding species with a ruderal strategy. Secondly, the vineyard weed communities differed according to the trophic status of the soil. Vineyards on acidic, sandy soils with low organic matter were characterised by small‐seeded annuals with a stress‐tolerant strategy whereas vineyards with clayey, calcareous soils rich in organic matter, harboured larger perennial nitrophilous species with large seeds and a competitive strategy. Our study is the first to show that weed species responded consistently to two independent gradients with specific traits associated with disturbance (life cycle and SLA) and soil resources (plant height and seed mass) gradients. Based on knowledge of the soil characteristics, it becomes possible to predict which type of weeds will develop according to the combination of practices applied on the vineyard rows and inter‐rows.

Competitive ability depends on mating system and ploidy level across Capsella species.

Background and AimsSelf-fertilization is often associated with ecological traits corresponding to the ruderal strategy, and selfers are expected to be less competitive than outcrossers, either because of a colonization/competition trade-off or because of the deleterious genetic effects of selfing. Range expansion could reduce further competitive ability while polyploidy could mitigate the effects of selfing. If pollinators are not limited, individual fitness is thus expected to be higher in outcrossers than in selfers and, within selfers, in polyploids than in diploids. Although often proposed in the botanical literature and also suggested by meta-analyses, these predictions have not been directly tested yet.MethodsIn order to compare fitness and the competitive ability of four Capsella species with a different mating system and ploidy level, we combined two complementary experiments. First, we carried out an experiment outdoors in north-west Greece, i.e. within the range of the obligate outcrossing species, C. grandiflora, where several life history traits were measured under two different disturbance treatments, weeded plots vs. unweeded plots. To better control competition and to remove potential effects of local adaptation of the outcrosser, we also performed a similar competition experiment but under growth chamber conditions.Key ResultsIn the outdoor experiment, disturbance of the environment did not affect the phenotype in any of the four species. For most traits, the obligate outcrossing species performed better than all selfing species. In contrast, polyploids did not survive or reproduce better than diploids. Under controlled conditions, as in the field experiment, the outcrosser had a higher fitness than selfing species and was less affected by competition. Finally, contrary to the outdoor experiment where the two behaved identically, polyploid selfers were less affected by competition than diploid selfes.ConclusionsIn the Capsella genus, selfing induces lower fitness than outcrossing and can also reduce competitive ability. The effect of polyploidy is, however, unclear. These results highlight the possible roles of ecological context in the evolution of selfing species.

Relative importance of region, seasonality and weed management practice effects on the functional structure of weed communities in French vineyards

Winegrowers have diversified their weed management practices over the last two decades changing the structure and the composition of weed communities. Complementary to taxonomic studies, trait-based approaches are promising ways for a better understanding of weed community responses to environmental and agronomic filters. In the present study, the impacts of climate, soil characteristics, seasons and weed management practices (chemical weeding, tillage and mowing) were assessed on weed communities from 46 plots in three French wine-growing regions (Champagne, Languedoc and Rhône valley). These agro-environmental gradients structuring weed communities according to their combinations of traits were highlighted using multivariate analysis (RLQ). The impacts of these filters on Community Weighted Means (CWM) and Community Weighted Variance (CWV) of weed communities were analysed using mixed and null modelling. Our results showed that spatio-temporal and weed management practice variables explained from 13% to 48% of the total variance of CWM (specific leaf area, maximum height, seed mass, flowering onset and duration and lateral spread). Region, seasonality and management practices explained 53%, 28% and 19% of CWM marginal variance, respectively. Weed management impacted CWM and CWV through two main gradients: (i) a soil disturbance gradient with high mechanical disturbance of soil in tilled plots and low mechanical disturbance in chemically weeded plots and (ii) a vegetation cover gradient with high vegetation abundance in mowed plots compared to barer soils in tilled and chemically weeded plots. In Languedoc, chemical weeding filtered weed communities with ruderal strategy trait values (low seed mass, small-stature) while mowed communities were more competitive (higher seed mass, higher stature and lower SLA). In Languedoc and Champagne, tillage favoured communities with high seed mass that increases the viability of buried seeds and high lateral spread values associated to the ability to resprout after tillage. This study demonstrated that trait-based approaches can be successfully applied to perennial cropping systems such as vineyards, in order to understand community assembly to better guide weed management practices.