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Species that form complex biogenic structures may increase niche space for many others and are assumed to be paramount for whole‐assemblage stability and ecosystem functioning. Because they often ameliorate physical conditions, ecosystem engineering species are also predicted to become more important with environmental stress. Testing this hypothesis, however, has proven difficult because isolating facilitation effects along the entire stress gradient is challenging. Here we addressed motile invertebrate assemblages associated to the mid‐intertidal chthamalid barnacle cover at four rocky shores, either with ('facilitated') or without ('control') a secondary natural cover of small mussels (Mytilaster solisianus and Brachidontes darwinianus). Following a factorial balanced design, replicate samples were taken at three tidal heights in all sites, encompassing a clear gradient of thermal stress and desiccation potential along the vertical range of the mussel‐enriched zone. While observations on general abundance were mostly consistent with stress‐independent facilitation, results for richness, diversity and assemblage structure indicated overarching stress‐dependent responses. All these later three response variables steadily declined from the low to the high level in the control barnacle habitat but remained unaltered in the mussel‐facilitated habitat. Increased facilitation higher on the shore is mostly due to retention of stress‐vulnerable groups such as polychaetes, flatworms and large nematodes which virtually collapse in the higher control habitat, further indicating that mechanisms of mussel facilitation involve relief of environmental stress rather than protection from higher‐order consumers. Our results suggest that mussel ecosystem engineering was fully preserved during the summer season when sampling took place. Ongoing research simulating heat waves compatible to climate‐change scenarios will test whether mussel facilitation would hold over the coming decades. [ABSTRACT FROM AUTHOR]

Plants minimize fitness losses through grazing by three fundamental strategies: tolerance, avoidance and escape. Annual species have been traditionally assumed to escape grazing through their short life cycle and seed dormancy; however, their grazing response strategies remain almost unexplored. How traits and their coordination affect species' grazing responses, and whether the generalized grazing model, which posits convergent filtering by grazing and drought, is applicable to this ecologically and economically important species group thus remain unclear.We used a trait‐based approach to evaluate grazing response strategies of winter annuals from the Middle East. Across 23 species, we examined the coordination of 16 traits hypothesized to be relevant for grazing responses, and linked them to species' fecundity responses, as proxy for fitness responses, to simulated grazing in controlled conditions, to species' abundance responses to grazing in the field and to species' distribution along a large‐scale rainfall gradient.Winter annuals exhibited both grazing escape and to a lesser extent tolerance indicated by (a) independent coordination of escape and tolerance traits, and (b) maintenance of higher fecundity in species with more pronounced escape or tolerance traits under simulated grazing. In the natural habitat, species with a more pronounced escape but not tolerance strategy maintained higher abundance under grazing in dry habitats, indicating convergent favouring of escape by both grazing and drought. However, this finding at the local scale was not mirrored by a strategy shift along a large‐scale rainfall gradient.Synthesis. The convergent favouring of escape traits by grazing and drought in annuals is consistent with the generalized grazing model. This model, which has been developed for perennials based on the avoidance strategy, can thus be extended to annuals based on escape, a finding that should facilitate projecting consequences of global change in drylands dominated by annuals. [ABSTRACT FROM AUTHOR]

Aim: Alexander von Humboldt observed that plant communities on different continents but under similar climatic conditions shared few common species but often contained representatives of the same genera or higher taxonomic groups. To test if this observation can be extended to substrate type, we explored whether a phylogenetic signature could be seen among floras growing on ultramafic substrates that present challenging edaphic conditions for plant growth and are well‐known for their distinctive vegetation. Location: Cuba, Madagascar, New Caledonia. Taxon: Angiosperms. Methods: We compared the floras of Cuba, Madagascar and New Caledonia to test whether the same plant families were under‐ or over‐represented on the ultramafic substrates of the three islands. Results: Pairwise comparisons showed that plant orders and families tended to have the same behaviour on the three islands, i.e. ultramafic substrates filtered (in favour of or against) the same plant groups in the three biogeographical distinct areas. The COM clade (comprising Celastrales, Oxalidales and Malpighiales) appears to be over‐represented on ultramafic substrates in all three islands and contains over half of the world's known nickel hyperaccumulators. Main conclusions: Our analyses provide support for Humboldt's observation by showing that ecological sorting can favour the same plant lineages in similar environments in different biogeographical regions. [ABSTRACT FROM AUTHOR]

Abstract: Floral colour is a fundamental signal that shapes plant–pollinator interactions. Despite theoretical reasons why floral colours might shift in representation along biotic and abiotic gradients, few studies have examined community‐level shifts in colour, and even fewer significant patterns have been detected. We examined floral colour on six replicated transects spanning 1,300 m in the Rocky Mountains of Colorado, USA. Along these transects, there is a hypothesized shift from bee‐dominated to fly‐dominated pollination with increasing elevation. The reflectance of flowers of 110 forb and shrub species was measured using a spectrophotometer, and was used to estimate three components of colour (hue, saturation and brightness) in relevant pollinator visual spaces. Percent cover data were collected from 67 sites and used to obtain community‐weighted mean (cwm) estimates of floral colour. We found strong patterns of elevational change in floral colour. Reflectancecwm of shorter wavelengths (UVB through human blue, 300–500 nm) generally decreased linearly with elevation, while reflectancecwm of longer wavelengths (human green through red, 500–700 nm) showed hump‐shaped patterns with highest reflectance at intermediate elevations. With respect to pollinators, saturationcwm increased significantly with elevation in both bee and fly visual spaces, while brightness contrastcwm showed a hump‐shaped pattern in bee space and a decline with elevation in fly visual space. For hue, cover of species perceived as bee‐blue declined with elevation, while cover of bee‐UV‐green species showed a hump‐shaped pattern. In comparison, we detected no elevational shifts in floral hues as perceived by flies. Synthesis. Hue patterns are consistent with the hypothesis that bee pollinators have shaped the geography of floral colour. The roles of fly pollinators and of abiotic drivers are more difficult to infer, although the drop in floral brightness at high elevations is consistent with predictions that low temperatures and more intense ultraviolet radiation should favour increased pigment concentrations there. Our results indicate that floral colour can be dynamic yet predictable across the landscape, a pattern that provides opportunities to tease apart the ecological and evolutionary drivers of this important plant trait. [ABSTRACT FROM AUTHOR]

Because establishing a new population often depends critically on finding mates, individuals capable of uniparental reproduction may have a colonization advantage. Accordingly, there should be an over-representation of colonizing species in which individuals can reproduce without a mate, particularly in isolated locales such as oceanic islands. Despite the intuitive appeal of this colonization filter hypothesis (known as Baker's law), more than six decades of analyses have yielded mixed findings., We assembled a dataset of island and mainland plant breeding systems, focusing on the presence or absence of self-incompatibility. Because this trait enforces outcrossing and is unlikely to re-evolve on short timescales if it is lost, breeding system is especially likely to reflect the colonization filter., We found significantly more self-compatible species on islands than mainlands across a sample of > 1500 species from three widely distributed flowering plant families (Asteraceae, Brassicaceae and Solanaceae). Overall, 66% of island species were self-compatible, compared with 41% of mainland species., Our results demonstrate that the presence or absence of self-incompatibility has strong explanatory power for plant geographical patterns. Island floras around the world thus reflect the role of a key reproductive trait in filtering potential colonizing species in these three plant families. [ABSTRACT FROM AUTHOR]

Abstract: Weedy species provide excellent opportunities to examine the process of successful colonization of novel environments. Despite the influence of the sexual system on a variety of processes from reproduction to genetic structure, how the sexual system of species influences weediness has received only limited consideration. We examined the hypothesis that weedy plants have an increased likelihood of being self‐compatible compared with nonweedy plants; this hypothesis is derived from Baker's law, which states that species that can reproduce uniparentally are more likely to successfully establish in a new habitat where mates are lacking. We combined a database of the weed (weedy/nonweedy) and introduction status (introduced/native) of plant species found in the USA with a database of plant sexual systems and determined whether native and introduced weeds varied in their sexual systems compared with native and introduced nonweeds. We found that introduced weeds are overrepresented by species with both male and female functions present within a single flower (hermaphrodites) whereas weeds native to the USA are overrepresented by species with male and female flowers present on a single plant (monoecious species). Overall, our results show that Baker's law is supported at the level of the sexual system, thus providing further evidence that uniparental reproduction is an important component of being either a native or introduced weed. [ABSTRACT FROM AUTHOR]

Aims The study of naturally discontinuous forest systems could help further our understanding of the relative roles of abiotic factors and spatial connectivity in influencing species turnover and plant metacommunity structure, compared to continuous forest formations, where local communities are often arbitrarily defined and where 'mass effects' and source-sink dynamics tend to confound the roles of dispersal and environment. Here we studied a tropical montane landscape where old-growth evergreen forest occurs as patchy formations in a matrix of natural grasslands, to test the influence of environment and connectivity on species turnover and woody plant metacommunity structure. Location Western and southern regions of the Upper Nilgiri Plateau, Western Ghats, southern India. Methods We sampled 85 vegetation plots located across a 600-km2 landscape, assembled environmental data, constructed contrasting spatial connectivity models, including models for the effects of topography on structural connectivity, and used RDA-based variation partitioning to assess the relative influence of environment and space on woody plant metacommunity structure. Results Considering several environmental and multi-scale spatial predictors, we could explain half of the variation in plant community structure. Environmental and habitat factors such as precipitation, temperature seasonality, elevation, fragment size and landscape context play a dominant role, explaining approximately 40% of variation. Spatial predictors based on Euclidean distance performed better than those that accounted for topographic resistance. Spatial predictors accounted for only 9% of the variation in plant metacommunity structure. Conclusion Our results support the species sorting paradigm of metacommunity structure, as abiotic effects and biotic interactions play dominant roles in influencing community structure and species turnover in these old-growth forests, with a comparatively small influence of spatial connectivity. Effective management of woody species diversity would therefore require conservation of these forests across the range of environmental conditions under which they occur. [ABSTRACT FROM AUTHOR]

The species composition within communities is highly dependent on the rate of species immigration and whether immigrating species possess the functional traits required by the prevailing environmental conditions. Once established, random fluctuations in birth and death rates may reduce the diversity of ecologically equivalent species if local populations are not replenished by immigrating individuals. Consequently, three key processes drive community assembly: dispersal limitation, ecological filtering, and ecological drift. However, disentangling the relative contribution of these processes remains a challenge in community ecology. We used a binomial generalized linear mixed model to test whether the occurrences of solitary bees within 46 communities in southeast Norway were driven by (1) dispersal limitation, that is, the geographic distance to the nearest site where conspecifics occurred; (2) ecological filtering, that is, if forb species richness selected for non-Ericaceae-affiliated species; and (3) ecological drift, that is, if small, isolated communities were dominated by regionally common species. The regression slopes from the model for each potential driver of community composition were compared with those expected under a null model, in which species were treated as ecologically equivalent. Both dispersal limitation and ecological filtering influenced the probability of species occurring within communities. The occurrence of species decreased with elevation, and this relationship depended on the relative commonness of species and their floral preferences. For non-Ericaceae-affiliated species, the patterns of occurrence mirrored that expected under the null (neutral) model, resulting in the same patterns as would be expected under ecological drift. In contrast, the response of Ericaceae-affiliated species differed from what would be expected from the null model. Our results also indicate that processes leading to neutral dynamics in species compositions drive a large part of the gradient in species richness in Norwegian bee communities. These processes seem related to sampling effects so that large and interconnected communities have a higher probability of including regionally rare species than small, isolated communities. Our results suggest that targeting habitats—where the influence of ecological filtering is expected to be greater than that of neutral dynamics—can increase the success of habitat management plans aimed at promoting rare species. [ABSTRACT FROM AUTHOR]

Evolutionary processes such as adaptation, ecological filtering, and niche conservatism involve the interaction of organisms with their environment and are thus commonly studied along environmental gradients. Elevational gradients have become among the most studied environmental gradients to understand large-scale patterns of species richness and composition because they are highly replicated with different combinations of geographical, environmental and historical factors. We here review the literature on using elevational gradients to understand evolutionary processes in ferns. Some phylogenetic studies of individual fern clades have considered elevation in the analysis or interpretation and postulated that fern diversification is linked to the colonization of mountain habitats. Other studies that have linked elevational community composition and hence ecological filtering with phylogenetic community composition and morphological traits, usually only found limited phylogenetic signal. However, these studies are ultimately only correlational, and there are few actual tests of the evolutionary mechanisms leading to these patterns. We identify a number of challenges for improving our understanding of how evolutionary and ecological processes are linked to elevational richness patterns in ferns: i) limited information on traits and their ecological relevance, ii) uncertainties on the dispersal kernels of ferns and hence the delimitation of regional species pools from which local assemblages are recruited, iii) limited genomic data to identify candidate genes under selection and hence actually document adaptation and selection, and iv) conceptual challenges in developing clear and testable hypotheses to how specific evolutionary processes can be linked to patterns in community composition and species richness. [ABSTRACT FROM AUTHOR]

PREMISE OF THE STUDY: Plant distributions have long been understood to be correlated with the environmental conditions to which species are adapted. Climate is one of the major components driving species distributions. Therefore, it is expected that the plants coexisting in a community are reflective of the local environment, particularly climate. METHODS: Presented here is a method for the estimation of climate from local plant species coexistence data. The method, Climate Reconstruction Analysis using Coexistence Likelihood Estimation (CRACLE), is a likelihood-based method that employs specimen collection data at a global scale for the inference of species climate tolerance. CRACLE calculates the maximum joint likelihood of coexistence given individual species climate tolerance characterization to estimate the expected climate. KEY RESULTS: Plant distribution data for more than 4000 species were used to show that this method accurately infers expected climate profiles for 165 sites with diverse climatic conditions. Estimates differ from the WorldClim global climate model by less than 1.5°C on average for mean annual temperature and less than ~250 mm for mean annual precipitation. This is a significant improvement upon other plant-based climate-proxy methods. CONCLUSIONS: CRACLE validates long hypothesized interactions between climate and local associations of plant species. Furthermore, CRACLE successfully estimates climate that is consistent with the widely used WorldClim model and therefore may be applied to the quantitative estimation of paleoclimate in future studies. [ABSTRACT FROM AUTHOR]

Question We tested whether co-existing tree species in tropical dwarf forests were deterministically assembled along gradients of air temperature, relative humidity and light availability, according to two important functional traits, specific leaf area ( SLA) and maximum species height ( Hmax). Location Tropical montane cloud forest, Bawangling Nature Reserve, Hainan Island, south China. Methods Null model analyses were used in conjunction with trait and species composition data collected to test our hypotheses at four plot sizes (25 m2, 100 m2, 400 m2 and 900 m2), addressing whether the consistent importance of variation in SLA and Hmax extends to these unique forests, as well as theoretical predictions concerning how patterns change with plot size. Results Low SLA species were significantly over-represented within forest communities for the two largest plot sizes, and taller-growing tree species were over-represented across all four plot sizes. Plot-level analyses indicated that low SLA species were associated with lower temperatures. Conclusions Our results show that tropical dwarf forests are deterministically assembled with respect to these two traits, and are consistent with other studies indicating that SLA responds to abiotic filters. Co-existing tree species were not significantly divergent for these two traits, indicating that variation in these two traits among trees does not contribute to niche differences (i.e. limiting similarity) and therefore co-existence within forest plots. Finally, our study demonstrates that patterns of community assembly change with plot size; however, trait convergence did not increase with plot size as previously predicted. [ABSTRACT FROM AUTHOR]

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Question It is presumed that environmental stress is more pronounced at higher altitudes in Andean forests due to lower rates of temperature-constrained processes of growth, nutrient uptake and decomposition. Because community assembly theory predicts a low variation in viable traits under conditions of strong ecological filtering, we asked if the diversity in plant traits related to productivity and reproduction would decrease upslope. Location Guaramacal National Park in the Andes of Venezuela (9°05-21′N, 70°-20′W). Methods We studied altitudinal patterns in the number of trait states of seven categorical traits found among vascular plants ( DBH ≥ 2.5 cm) in 35 0.1-ha plots between 1330 and 2890 m. Information on plant traits was obtained from literature and herbaria. To test the altitudinal correlations, we permuted the plot-to-species matrix by randomly selecting species from the entire species pool (conserving the species richness and the species-abundance pattern in each plot), applying no restrictions and by creating plot-wise null assemblages of species that most likely occurred near a particular plot. In addition, the altitudinal pattern of trait states was examined using fourth-corner analysis. Results Both null model tests yielded similar results. The trait state diversity in fruit size decreased upslope. Plants with small fruits were mostly, but not exclusively, found at higher altitudes, whereas plants with large fruits occurred only at lower elevations. Leaf size showed more states at higher altitudes but this pattern disappeared when rare leaf size classes were down-weighted. The upslope decrease in fruit size might be explained by the relatively low tree height of the upper montane rain forests, the increased selection for large seeds at high temperatures downslope, and the upslope decrease of large-leaved taxa (in view of Corner's rule). Conclusions The functional diversity of important plant traits changed with altitude at Guaramacal. Altitudinal effects on plant trait responses should be controlled for in studies that monitor the degradation of functional diversity in Andean forests in relation to human influence. [ABSTRACT FROM AUTHOR]

• Premise of the study: Hawaii is home to 238 native and 35 alien fern and lycophyte taxa distributed across steep gradients in elevation and resource availability. The fern flora spans a wide range of growth forms, with extraordinary diversity in morphology and plant size. Yet the potential factors underlying this diversity have remained enigmatic. • Methods: We used a trait database generated from the most recent and comprehensive survey of Hawaiian ferns and lycophytes to test hypotheses of size-scaling and trait associations with environment and growth form as factors underlying this diversity. We also tested relationships among morphology, taxon abundance and distribution and identified key differences between native and alien taxa. • Key results: Strong trait--trait relationships included geometric scaling of plant dimensions with a tendency for more divided fronds in larger ferns. Trait--environment relationships independent of size included more divided fronds at higher elevation, longer blades in shaded habitats, and fronds with shorter stipes and fewer pinnae in drier habitats. Growth forms differed in mean size with epiphytic and epipetric taxa smaller than terrestrial ferns. Plant size was independent of taxon abundance and distribution across islands, and native and alien ferns did not differ in mean size. Alien taxa were more abundant, especially at lower elevations, apparently due to human land use. • Conclusions: These relationships point to linkages of fern form and demography with biogeography and highlight potential flora-scale physiological and morphological adaptations in ferns across contrasting environments. [ABSTRACT FROM AUTHOR]