Phylogenetic structure of Floridian plant communities depends on taxonomic and spatial scale

Phylogeny structures species' interactions in experimental ecological communities

Species' traits and interactions are products of evolutionary history. Despite the long-standing hypothesis that closely related species possess similar traits, and thus experience stronger competition, measuring the effect of evolutionary history on the ecology of natural communities remains challenging. We propose a novel framework to test whether phylogeny influences patterns of coexistence and abundance of species assemblages. In our approach, phylogenetic trees are used to parameterize species' interactions, which in turn determine the abundance of species in a given assemblage. We use likelihoods to score models parameterized with a given phylogeny, and contrast them with models built using random trees, allowing us to test whether phylogenetic information helps to predict species' abundances. Our statistical framework reveals that interactions are indeed structured by phylogeny in a large set of experimental plant communities. Our results confirm that evolutionary history can help predict, and potentially manage or conserve, the structure and function of complex ecological communities.

Variation in near-surface soil temperature drives plant assemblage differentiation across aspect

Quantifying assemblage variation across environmental gradients provides insight into the ecological and evolutionary mechanisms that differentiate assemblages locally within a larger climate regime. We assessed how vascular plant functional composition and diversity varied across microenvironment to identify ecological differences in assemblages in a mountainous fieldsite in northeastern Utah, USA. Then, we looked at how life-history strategies and information about phylogenetic differences affect the relationship between functional metrics and environment. We found less functionally dispersed assemblages that were shorter and more resource-conservative on south-facing slopes where intra-annual soil temperature was hotter and more variable. In contrast, we found more functionally dispersed assemblages, that were taller and more resource-acquisitive on north-facing slopes where intra-annual temperature was cooler and less variable. Herbaceous and woody perennials drove these trends. Additionally, including information about phylogenetic differences in a dispersion metric indicated that phylogeny accounts for traits we did not measure. At this fieldsite, soil temperature acts as an environmental filter across aspect. If soil temperature increases and becomes more variable, intra-annually, the function of north- versus south-facing assemblages may be at risk for contrasting reasons. On south-facing slopes, assemblages may not have the variance in functional diversity needed to respond to more intense, stressful conditions. Conversely, assemblages on north-facing slopes may not have the resource-conservative strategies needed to persist if temperatures become hotter and more variable intra-annually. Given these results, we advocate for the inclusion of aspect differentiation in studies seeking to understand species and assemblage shifts in response to changing climate conditions.

Phylogenetic indices and temporal and spatial scales shape the neighborhood effect on seedling survival in a mid-mountain moist evergreen broad-leaved forest, Gaoligong Mountains, Southwestern China

Density dependence and habitat filtering have been proposed to aid in understanding community assembly and species coexistence. Phylogenetic relatedness between neighbors was used as a proxy for assessing the degree of ecological similarity among species. There are different conclusions regarding the neighborhood effect in previous studies with different phylogenetic indices or at different spatiotemporal scales. However, the effects of density dependence, neighbor phylogenetic relatedness, and habitat filtering on seedling survival with different phylogenetic indices or at different temporal and spatial scales are poorly understood. We monitored 916 seedlings representing 56 woody plant species within a 4-ha forest dynamics plot for 4 years (from 2020 to 2023) in a subtropical mid-mountain moist evergreen broad-leaved forest in the Gaoligong Mountains, Southwestern China. Using generalized linear mixed models, we tested whether and how four phylogenetic indices: total phylogenetic distance (TOTPd), average phylogenetic distance (AVEPd), relative average phylogenetic distance (APd'), and relative nearest taxon phylogenetic distance (NTPd'), three temporals (1, 2, and 3 years), and spatial scales (1, 2, and 4 ha) affect the effect of density dependence, phylogenetic density dependence, and habitat filtering on seedling survival. We found evidence of the effect of phylogenetic density dependence in the 4-ha forest dynamics plot. The effects of density dependence, phylogenetic density dependence, and habitat filtering on seedling survival were influenced by phylogenetic indices and temporal and spatial scales. The effects of phylogenetic density dependence and habitat filtering on seedling survival were more conspicuous only at 1-year intervals, compared with those at 2- and 3-year intervals. We did not detect any effects of neighborhood or habitat factors on seedling survival at small scales (1 and 2 ha), although these effects were more evident at the largest spatial scale (4 ha). These findings highlight that the effects of local neighborhoods and habitats on seedling survival are affected by phylogenetic indices as well as temporal and spatial scales. Our study suggested that phylogenetic index APd', shortest time scale (1 year), and largest spatial scales (4 ha) were suitable for neighborhood studies in a mid-mountain moist evergreen broad-leaved forest in Gaoligong Mountains. Phylogenetic indices and spatiotemporal scales have important impacts on the results of the neighborhood studies.

Environmental determinants of phylogenetic diversity in vernal pool habitats

Phylogenetic diversity offers critical insights into the ecological dynamics shaping species composition and ecosystem function, thereby informing conservation strategies. Despite its recognized importance in ecosystem management, the assessment of phylogenetic diversity in endangered habitats, such as vernal pools, remains limited. Vernal pools, characterized by cyclical inundation and unique plant communities, present an ideal system for investigating the interplay between ecological factors and phylogenetic structure. This study aims to characterize the phylogenetic patterns of vernal pools and their associated vegetation zones, addressing questions about taxonomic and phylogenetic community discreteness, the role of flooding as a habitat filter, the influence of invasive species on phylogenetic structure, and the impact of seasonal variation on phylogenetic diversity. I find that zones-of-vegetation exhibit high between zone taxonomic and phylogenetic beta diversity whereas each zone forms a unique cluster, suggesting that zones are taxonomically and phylogenetically discrete units. Regions of high-inundation pressure exhibit phylogenetic clustering, indicating that flooding is a habitat filter in vernal pool habitats. Competition between native species conform to the 'competitive relatedness hypothesis' and, conversely, communities dominated by invasive Eurasian grass species are phylogenetically clustered. In addition, I find that phylogenetic diversity within zones fluctuates across the spring season in response to changing water levels, precipitation, and temperature. By analyzing three pools within the Merced Vernal Pool and Grassland Reserve, this research elucidates the phylogenetic dynamics of vernal pools. The findings underscore the need for tailored conservation strategies that account for the unique ecological characteristics of each vegetation zone within vernal pool habitats.

Cushions serve as conservation refuges for the Himalayan alpine plant diversity: Implications for nature-based environmental management

Globally, rapid climate and land-use changes in alpine environments are posing severe risks to their bountiful biodiversity and ecosystem services. Currently, nature-based solutions are fast-emerging as the preferred approach to address the challenges of environmental sustainability. In alpine environments, cushion plants owing to their unique architecture and adaptability offer a potential nature-based system to plan biodiversity conservation and habitat restoration strategies. Here, we employed an analytical framework to test whether and how the cushion plants facilitate the sustenance of alpine plant diversity in Kashmir Himalaya. We specifically aimed to answer: what are the effects of the cushion plants on the patterns of alpine species richness and phylogenetic diversity, and whether these effects vary across spatial scales (local versus landscape), cushion types, and changing elevation. We randomly selected pairs of cushion and neighbouring non-cushion plots (size 100 m2) across 34 different alpine sites in the study region. Within each plot, we randomly laid three 5 m2 quadrats for vegetation sampling, and sampled a total of 204 quadrats in 68 plots with seven cushion types along elevation ranging from 3100 to 3850 m. Our results revealed positive effects of the cushions by supporting a higher community species richness (SR) and phylogenetic diversity (PD). The effects were consistent both at the local (i.e., quadrat) and landscape (i.e., plot) scales, but varied significantly with the cushion type. Interestingly, SR and PD showed an increasing trend with increase in elevation in cushion communities, thereby supporting stress gradient hypothesis. Along the elevational gradient, the cushion communities showed phylogenetic overdispersion, but clustering by non-cushions. Overall, our study provides empirical evidence to reinforce the role of the cushions as conservation refugia for an imperilled alpine plant diversity in the Himalaya. Looking ahead, we highlight the far-reaching implications of our findings in guiding the nature-based environmental management of alpine ecosystems worldwide.

Foliar spectra accurately distinguish most temperate tree species and show strong phylogenetic signal

PREMISE

Spectroscopy is a powerful remote sensing tool for monitoring plant biodiversity over broad geographic areas. Increasing evidence suggests that foliar spectral reflectance can be used to identify trees at the species level. However, most studies have focused on only a limited number of species at a time, and few studies have explored the underlying phylogenetic structure of leaf spectra. Accurate species identifications are important for reliable estimations of biodiversity from spectral data.

METHODS

Using over 3500 leaf-level spectral measurements, we evaluated whether foliar reflectance spectra (400-2400 nm) can accurately differentiate most tree species from a regional species pool in eastern North America. We explored relationships between spectral, phylogenetic, and leaf functional trait variation as well as their influence on species classification using a hurdle regression model.

RESULTS

Spectral reflectance accurately differentiated tree species (κ = 0.736, ±0.005). Foliar spectra showed strong phylogenetic signal, and classification errors from foliar spectra, although present at higher taxonomic levels, were found predominantly between closely related species, often of the same genus. In addition, we find functional and phylogenetic distance broadly control the occurrence and frequency of spectral classification mistakes among species.

CONCLUSIONS

Our results further support the link between leaf spectral diversity, taxonomic hierarchy, and phylogenetic and functional diversity, and highlight the potential of spectroscopy to remotely sense plant biodiversity and vegetation response to global change.

A slow-fast trait continuum at the whole community level in relation to land-use intensification

Organismal functional strategies form a continuum from slow- to fast-growing organisms, in response to common drivers such as resource availability and disturbance. However, whether there is synchronisation of these strategies at the entire community level is unclear. Here, we combine trait data for >2800 above- and belowground taxa from 14 trophic guilds spanning a disturbance and resource availability gradient in German grasslands. The results indicate that most guilds consistently respond to these drivers through both direct and trophically mediated effects, resulting in a 'slow-fast' axis at the level of the entire community. Using 15 indicators of carbon and nutrient fluxes, biomass production and decomposition, we also show that fast trait communities are associated with faster rates of ecosystem functioning. These findings demonstrate that 'slow' and 'fast' strategies can be manifested at the level of whole communities, opening new avenues of ecosystem-level functional classification.

Direct development in Atlantic Forest anurans: What can environmental and biotic influences explain about its evolution and occurrence?

Different environmental and biological factors can originate and support different alternative life histories in different taxonomic groups. Likewise, these factors are important for the processes that assemble and structure communities. Amphibians, besides being highly susceptible to environmental conditions, have various reproductive strategies, such as the direct development of individuals. Several hypotheses have been raised about possible selective pressures related to the emergence of direct development in anurans, as well as the relationship between environmental characteristics and the occurrence of these species. Such investigations, however, have mainly focused on specific clades and/or regions. Here, we use structural equation modelling to investigate the relationships between different abiotic (temperature, precipitation, humidity, and terrain slope) and biotic (phylogenetic composition and functional diversity) factors and the proportion of species with direct development in 766 anuran communities of the Atlantic Forest, a biome with a vast diversity of anuran species and high environmental complexity. Anuran communities with higher proportions of direct developing species were found to be mainly influenced by low potential evapotranspiration, low temperature seasonality, and high functional diversity. Phylogenetic composition and terrain slope were also found to be important in determining the occurrence of these species in Atlantic Forest communities. These results show the importance of these factors in the structuring of these communities and provide important contributions to the knowledge of direct development in anurans.

Phylogenetic relatedness can influence cover crop-based weed suppression

Cover crops are plants grown to provide regulating, supporting, and cultural ecosystem services in managed environments. In agricultural systems, weed suppression services from cover crops can be an important tool to promote sustainability as reliance on herbicides and tillage for weed management has caused pollution, biodiversity loss, and human health issues. However, to effectively use weed suppression services from cover crops, farmers must carefully select species that fit within their rotations and suppress their problematic weeds. Understanding how the relatedness between cover crops and weeds affects their interactions will help farmers select cover crops for targeted weed management. The phylogenetic distance between species reflects their relatedness and was studied through a series of field experiments that compared weed suppression in winter and summer cover crops with tilled controls. This study demonstrates that cover crops can reduce up to 99% of weed biomass and alter weed community structure by suppressing phylogenetically related weed species. Results also suggest that cover crop planting season can influence weed community structure since only overwintering treatments affected the phylogenetic distance of weed communities. In an applied context, these results help develop cover crop-based weed management systems, demonstrating that problematic weeds can be managed by selecting phylogenetically related cover crop species. More broadly, this study provides a framework for evaluating weed communities through a phylogenetic perspective, which provides new insight into plant interactions in agriculture.

Species phylogeny, ecology, and root traits as predictors of root exudate composition

Root traits including root exudates are key factors affecting plant interactions with soil and thus play an important role in determining ecosystem processes. The drivers of their variation, however, remain poorly understood. We determined the relative importance of phylogeny and species ecology in determining root traits and analyzed the extent to which root exudate composition can be predicted by other root traits. We measured different root morphological and biochemical traits (including exudate profiles) of 65 plant species grown in a controlled system. We tested phylogenetic conservatism in traits and disentangled the individual and overlapping effects of phylogeny and species ecology on traits. We also predicted root exudate composition using other root traits. Phylogenetic signal differed greatly among root traits, with the strongest signal in phenol content in plant tissues. Interspecific variation in root traits was partly explained by species ecology, but phylogeny was more important in most cases. Species exudate composition could be partly predicted by specific root length, root dry matter content, root biomass, and root diameter, but a large part of variation remained unexplained. In conclusion, root exudation cannot be easily predicted based on other root traits and more comparative data on root exudation are needed to understand their diversity.

Phylogenetic and functional trait-based community assembly within Pacific Cyrtandra (Gesneriaceae): Evidence for clustering at multiple spatial scales

Tropical rainforest communities are often characterized by a small number of species-rich genera that contribute disproportionately to the alpha diversity in these habitats. In the Pacific Basin, there are nearly 200 species of Cyrtandra, most of which are white-flowered woody shrubs that are single-island endemics. Within these island communities, multiple Cyrtandra species are commonly observed to occur sympatrically in wet forest understories, forming swarms of what appear to be ecologically similar taxa. The aim of this study was to determine whether species of these plants are randomly assembled with respect to phylogenetic relatedness and traits that are ecologically relevant. I examined assembly patterns across three Pacific archipelagoes using a combination of 10 functional traits and a well-resolved phylogeny comprising 34 species of Cyrtandra. Coexisting species were found to be more closely related and more phenotypically similar than would be expected by chance. This pattern was observed at both regional (island) and local (site) spatial scales. The retention of phylogenetic signal in floral traits and the strong influence of these traits on the observed degree of phylogenetic clustering may indicate that generalist insect pollinators act as a biotic filter on oceanic islands, driving selection for similar floral morphology among closely related species of Pacific Cyrtandra. Phylogenetic signal was also detected in leaf size, which contributed to niche clustering at both spatial scales. Coupled with a propensity for long-distance dispersal, and the restricted distribution of Cyrtandra to rainforest understories, this finding suggests that environmental filtering along this trait axis may be more important than dispersal limitation in determining species assemblages. This study supports the theory that plant species are not randomly assembled, and instead, that niche-based processes structure biodiversity at regional and local spatial scales in diverse congeneric species assemblages.

A spatially explicit trait-based approach uncovers changes in assembly processes under warming

The re-assembly of plant communities during climate warming depends on several concurrent processes. Here, we present a novel framework that integrates spatially explicit sampling, plant trait information and a warming experiment to quantify shifts in these assembly processes. By accounting for spatial distance between individuals, our framework allows separation of potential signals of environmental filtering from those of different types of competition. When applied to an elevational transplant experiment in the French Alps, we found common signals of environmental filtering and competition in all communities. Signals of environmental filtering were generally stronger in alpine than in subalpine control communities, and warming reduced this filter. Competition signals depended on treatments and traits: Symmetrical competition was dominant in control and warmed alpine communities, while hierarchical competition was present in subalpine communities. Our study highlights how distance-dependent frameworks can contribute to a better understanding of transient re-assembly dynamics during environmental change.

Effect of sampling design on estimation of phylogenetic diversity metrics of fish community

Phylogenetic diversity has been widely used to explore diversity patterns and assess processes governing the species composition in community. The estimates of many metrics depend on high-quality data collected from well-designed sampling surveys. However, knowledge of impacts of sampling design on estimation of phylogenetic diversity metrics remains unclear. This study is aim to evaluate the influence of sampling design on phylogenetic diversity metrics estimation of fish community. Simple random sampling (SRS), systematic sampling (SS) and stratified random sampling (StRS) with different sampling intensities were chosen and mean pairwise distances (MPD), mean nearest taxon distance (MNTD), phylogenetic diversity (PD), phylogenetic species variability (PSV), phylogenetic species evenness (PSE) and phylogenetic species richness (PSR) were selected. SRS and StRS showed similar impact on phylogenetic diversity indices estimation and performed relatively well for collecting data to estimate phylogenetic diversity. The accuracy and precision of the estimation increased with sampling intensity under SRS and StRS except SS. MNTD was the only metric not underestimated in four seasons. Metrics strongly influenced by species richness were underestimated when sampling intensity was insufficient. MPD, PSV and PSE showed an obvious seasonal change, which was due to the seasonal differences in fish species composition. In cases where under-sampling is suspected or logistically unavoidable, phylogenetic diversity metrics that are relatively insensitive to sampling design (e.g., MPD and PSV) should be prioritized, especially for exploring the temporal variation in fish community. This study reveals it is indispensable to evaluate sampling design when estimating phylogenetic diversity metrics, especially those indices susceptible to species richness.

The global spectrum of plant form and function: enhanced species-level trait dataset

Here we provide the 'Global Spectrum of Plant Form and Function Dataset', containing species mean values for six vascular plant traits. Together, these traits -plant height, stem specific density, leaf area, leaf mass per area, leaf nitrogen content per dry mass, and diaspore (seed or spore) mass - define the primary axes of variation in plant form and function. The dataset is based on ca. 1 million trait records received via the TRY database (representing ca. 2,500 original publications) and additional unpublished data. It provides 92,159 species mean values for the six traits, covering 46,047 species. The data are complemented by higher-level taxonomic classification and six categorical traits (woodiness, growth form, succulence, adaptation to terrestrial or aquatic habitats, nutrition type and leaf type). Data quality management is based on a probabilistic approach combined with comprehensive validation against expert knowledge and external information. Intense data acquisition and thorough quality control produced the largest and, to our knowledge, most accurate compilation of empirically observed vascular plant species mean traits to date.

Functional traits mediate individualistic species-environment distributions at broad spatial scales while fine-scale species associations remain unpredictable

PREMISE

Numerous processes influence plant distributions and co-occurrence patterns, including ecological sorting, limiting similarity, and stochastic effects. To discriminate among these processes and determine the spatial scales at which they operate, we investigated how functional traits and phylogenetic relatedness influence the distribution of temperate forest herbs.

METHODS

We surveyed understory plant communities across 257 forest stands in Wisconsin and Michigan (USA) and applied Bayesian phylogenetic linear mixed-effects models (PGLMMs) to quantify how functional traits and phylogenetic relatedness influence the environmental distribution of 139 herbaceous plant species along broad edaphic, climatic, and light gradients. These models also allowed us to test how functional and phylogenetic similarity affect species co-occurrence within microsites.

RESULTS

Leaf height, specific leaf area, and seed mass all influenced individualistic plant distributions along landscape-scale gradients in soil texture, soil fertility, light availability, and climate. In contrast, phylogenetic relationships did not consistently predict species-environment relationships. Neither functionally similar nor phylogenetically related herbs segregated among microsites within forest stands.

CONCLUSIONS

Trait-mediated ecological sorting appears to drive temperate-forest community assembly, generating individualistic plant distributions along regional environmental gradients. This finding links classic studies in plant ecology and prior research in plant physiological ecology to current trait-based approaches in community ecology. However, our results fail to support the common assumption that limiting similarity governs local plant co-occurrences. Strong ecological sorting among forest stands coupled with stochastic fine-scale interactions among species appear to weaken deterministic, niche-based assembly processes at local scales.

Exploring fine-scale assembly of ectomycorrhizal fungal communities through phylogenetic and spatial distribution analyses

Ectomycorrhizal fungi (EMF) form symbiotic relationship with the roots of host plants. EMF communities are composed of highly diverse species; however, how they are assembled has been a long-standing question. In this study, we investigated from a phylogenetic perspective how EMF communities assemble on Pinus densiflora seedlings at different spatial scales (i.e., seedling scale and root tip scale). P. densiflora seedlings were collected from different habitats (i.e., disturbed areas and mature forests), and their EMF communities were investigated by morphotype sequencing and next-generation sequencing (NGS). To infer assembly mechanisms, phylogenetic relatedness within the community (i.e., phylogenetic structure) was estimated and spatial distribution of EMF root tips was analyzed. The EMF communities on pine seedlings were largely different between the two habitats. Phylogenetically restricted lineages (Amphinema, /suillus-rhizopogon) were abundant in the disturbed areas, whereas species from diverse lineages were abundant in the mature forests (Russula, Sebacina, /tomentella-thelephora, etc.). In the disturbed areas, phylogenetically similar EMF species were aggregated at the seedling scale, suggesting that disturbance acts as a powerful abiotic filter. However, phylogenetically similar species were spatially segregated from each other at the root tip scale, indicating limiting similarity. In the mature forest seedlings, no distinct phylogenetic signals were detected at both seedling and root tip scale. Collectively, our results suggest that limiting similarity may be an important assembly mechanism at the root tip scale and that assembly mechanisms can vary across habitats and spatial scales.

Can evolutionary history predict plant plastic responses to climate change?

Plant plastic responses are critical to the adaptation and survival of species under climate change, but whether they are constrained by evolutionary history (phylogeny) is largely unclear. Plant leaf traits are key in determining plants' performance in different environments, and if these traits and their variation are phylogenetically dependent, predictions could be made to identify species vulnerable to climate change. We compiled data on three leaf traits (photosynthetic rate, specific leaf area, and leaf nitrogen content) and their variation under four environmental change scenarios (warming, drought, elevated CO₂ , or nitrogen addition) for 434 species, from 210 manipulation experiments. We found phylogenetic signal in the three traits but not in their variation under the four scenarios. This indicates that closely related species show similar traits but that their plastic responses could not be predicted from species relatedness under environmental change. Meanwhile, phylogeny weakened the slopes but did not change the directions of conventional pairwise trait relationships, suggesting that co-evolved leaf trait pairs have consistent responses under contrasting environmental conditions. Phylogeny can identify lineages rich in species showing similar traits and predict their relationships under climate change, but the degree of plant phenotypic variation does not vary consistently across evolutionary clades.

Hierarchical phylogenetic community assembly of soil protists in a temperate agricultural field

Protists are abundant, diverse and perform essential functions in soils. Protistan community structure and its change across time or space are traditionally studied at the species-level but the relative importance of the processes shaping these patterns depends on the taxon phylogenetic resolution. Using 18S rDNA amplicon data of the Cercozoa, a group of dominant soil protists, from an agricultural field in western Germany, we observed a turnover of relatively closely related taxa (from sequence variants to genus-level clades) across soil depth; while across soil habitats (rhizosphere, bulk soil, drilosphere) we observed turnover of relatively distantly related taxa, confirming Paracercomonadidae as a rhizosphere-associated clade. We extended our approach to show that closely related Cercozoa encounter divergent AM fungi across soil depth and that distantly related Cercozoa encounter closely related AM fungi across soil compartments. This study suggests that soil Cercozoa community assembly at the field-scale is driven by niche-based processes shaped by evolutionary legacy of adaptation to conditions primarily related to soil compartment, followed by soil layer, giving a deeper understanding on the selection pressures that shaped their evolution.

The acquisitive-conservative axis of leaf trait variation emerges even in homogeneous environments

BACKGROUND AND AIMS

The acquisitive-conservative axis of plant ecological strategies results in a pattern of leaf trait covariation that captures the balance between leaf construction costs and plant growth potential. Studies evaluating trait covariation within species are scarcer, and have mostly dealt with variation in response to environmental gradients. Little work has been published on intraspecific patterns of leaf trait covariation in the absence of strong environmental variation.

METHODS

We analysed covariation of four leaf functional traits [specific leaf area (SLA) leaf dry matter content (LDMC), force to tear (Ft) and leaf nitrogen content (Nm)] in six Poaceae and four Fabaceae species common in the dry Chaco forest of Central Argentina, growing in the field and in a common garden. We compared intraspecific covariation patterns (slopes, correlation and effect size) of leaf functional traits with global interspecific covariation patterns. Additionally, we checked for possible climatic and edaphic factors that could affect the intraspecific covariation pattern.

KEY RESULTS

We found negative correlations for the LDMC-SLA, Ft-SLA, LDMC-Nm and Ft-Nm trait pairs. This intraspecific covariation pattern found both in the field and in the common garden and not explained by climatic or edaphic variation in the field follows the expected acquisitive-conservative axis. At the same time, we found quantitative differences in slopes among different species, and between these intraspecific patterns and the interspecific ones. Many of these differences seem to be idiosyncratic, but some appear consistent among species (e.g. all the intraspecific LDMC-SLA and LDMC-Nm slopes tend to be shallower than the global pattern).

CONCLUSIONS

Our study indicates that the acquisitive-conservative leaf functional trait covariation pattern occurs at the intraspecific level even in the absence of relevant environmental variation in the field. This suggests a high degree of variation-covariation in leaf functional traits not driven by environmental variables.

Representing plant diversity in land models: An evolutionary approach to make "Functional Types" more functional

Plants are critical mediators of terrestrial mass and energy fluxes, and their structural and functional traits have profound impacts on local and global climate, biogeochemistry, biodiversity, and hydrology. Yet, Earth System Models (ESMs), our most powerful tools for predicting the effects of humans on the coupled biosphere-atmosphere system, simplify the incredible diversity of land plants into a handful of coarse categories of "Plant Functional Types" (PFTs) that often fail to capture ecological dynamics such as biome distributions. The inclusion of more realistic functional diversity is a recognized goal for ESMs, yet there is currently no consistent, widely accepted way to add diversity to models, that is, to determine what new PFTs to add and with what data to constrain their parameters. We review approaches to representing plant diversity in ESMs and draw on recent ecological and evolutionary findings to present an evolution-based functional type approach for further disaggregating functional diversity. Specifically, the prevalence of niche conservatism, or the tendency of closely related taxa to retain similar ecological and functional attributes through evolutionary time, reveals that evolutionary relatedness is a powerful framework for summarizing functional similarities and differences among plant types. We advocate that Plant Functional Types based on dominant evolutionary lineages ("Lineage Functional Types") will provide an ecologically defensible, tractable, and scalable framework for representing plant diversity in next-generation ESMs, with the potential to improve parameterization, process representation, and model benchmarking. We highlight how the importance of evolutionary history for plant function can unify the work of disparate fields to improve predictive modeling of the Earth system.

Climatic and soil factors explain the two-dimensional spectrum of global plant trait variation

Plant functional traits can predict community assembly and ecosystem functioning and are thus widely used in global models of vegetation dynamics and land-climate feedbacks. Still, we lack a global understanding of how land and climate affect plant traits. A previous global analysis of six traits observed two main axes of variation: (1) size variation at the organ and plant level and (2) leaf economics balancing leaf persistence against plant growth potential. The orthogonality of these two axes suggests they are differently influenced by environmental drivers. We find that these axes persist in a global dataset of 17 traits across more than 20,000 species. We find a dominant joint effect of climate and soil on trait variation. Additional independent climate effects are also observed across most traits, whereas independent soil effects are almost exclusively observed for economics traits. Variation in size traits correlates well with a latitudinal gradient related to water or energy limitation. In contrast, variation in economics traits is better explained by interactions of climate with soil fertility. These findings have the potential to improve our understanding of biodiversity patterns and our predictions of climate change impacts on biogeochemical cycles.

Edaphic heterogeneity and the evolutionary trajectory of Amazonian plant communities

We investigated how the phylogenetic structure of Amazonian plant communities varies along an edaphic gradient within the non-inundated forests. Forty localities were sampled on three terrain types representing two kinds of soil: clayey soils of a high base cation concentration derived from the Solimões formation, and loamy soils with lower base cation concentration derived from the Içá formation and alluvial terraces. Phylogenetic community metrics were calculated for each locality for ferns and palms both with ferns as one group and for each of three fern clades with a crown group age comparable to that of palms. Palm and fern communities showed significant and contrasting phylogenetic signals along the soil gradient. Fern species richness increased but standard effect size of mean pairwise distance (SES.MPD) and variation of pairwise distances (VPD) decreased with increasing soil base cation concentration. In contrast, palm communities were more species rich on less cation-rich soils and their SES.MPD increased with soil base cation concentration. Species turnover between the communities reflected the soil gradient slightly better when based on species occurrences than when phylogenetic distances between the species were considered. Each of the three fern subclades behaved differently from each other and from the entire fern clade. The fern clade whose phylogenetic patterns were most similar to those of palms also resembled palms in being most species-rich on cation-poor soils. The phylogenetic structuring of local plant communities varies along a soil base cation concentration gradient within non-inundated Amazonian rain forests. Lineages can show either similar or different phylogenetic community structure patterns and evolutionary trajectories, and we suggest this to be linked to their environmental adaptations. Consequently, geological heterogeneity can be expected to translate into a potentially highly diverse set of evolutionarily distinct community assembly pathways in Amazonia and elsewhere.

Remotely sensed between-individual functional trait variation in a temperate forest

Trait-based ecology holds the promise to explain how plant communities work, for example, how functional diversity may support community productivity. However, so far it has been difficult to combine field-based approaches assessing traits at the level of plant individuals with limited spatial coverage and approaches using remote sensing (RS) with complete spatial coverage but assessing traits at the level of vegetation pixels rather than individuals. By delineating all individual-tree crowns within a temperate forest site and then assigning RS-derived trait measures to these trees, we combine the two approaches, allowing us to use general linear models to estimate the influence of taxonomic or environmental variation on between- and within-species variation across contiguous space.We used airborne imaging spectroscopy and laser scanning to collect individual-tree RS data from a mixed conifer-angiosperm forest on a mountain slope extending over 5.5 ha and covering large environmental gradients in elevation as well as light and soil conditions. We derived three biochemical (leaf chlorophyll, carotenoids, and water content) and three architectural traits (plant area index, foliage-height diversity, and canopy height), which had previously been used to characterize plant function, from the RS data. We then quantified the contributions of taxonomic and environmental variation and their interaction to trait variation and partitioned the remaining within-species trait variation into smaller-scale spatial and residual variation. We also investigated the correlation between functional trait and phylogenetic distances at the between-species level. The forest consisted of 13 tree species of which eight occurred in sufficient abundance for quantitative analysis.On average, taxonomic variation between species accounted for more than 15% of trait variation in biochemical traits but only around 5% (still highly significant) in architectural traits. Biochemical trait distances among species also showed a stronger correlation with phylogenetic distances than did architectural trait distances. Light and soil conditions together with elevation explained slightly more variation than taxonomy across all traits, but in particular increased plant area index (light) and reduced canopy height (elevation). Except for foliage-height diversity, all traits were affected by significant interactions between taxonomic and environmental variation, the different responses of the eight species to the within-site environmental gradients potentially contributing to the coexistence of the eight abundant species.We conclude that with high-resolution RS data it is possible to delineate individual-tree crowns within a forest and thus assess functional traits derived from RS data at individual level. With this precondition fulfilled, it is then possible to apply tools commonly used in field-based trait ecology to partition trait variation among individuals into taxonomic and potentially even genetic variation, environmental variation, and interactions between the two. The method proposed here presents a promising way of assessing individual-based trait information with complete spatial coverage and thus allowing analysis of functional diversity at different scales. This information can help to better understand processes shaping community structure, productivity, and stability of forests.

Spatial Scale Dependence of Ecological Factors That Regulate Functional and Phylogenetic Assembly in a Mediterranean High Mountain Grassland

Understanding how functional and phylogenetic patterns vary among scales and along ecological gradients within a given species pool is critical for inferring community assembly processes. However, we lack a clear understanding of these patterns in stressful habitats such as Mediterranean high mountains where ongoing global warming is expected to affect species fitness and species interactions, and subsequently species turnover. In this study, we investigated 39 grasslands with the same type of plant community and very little species turnover across an elevation gradient above the treeline at Sierra de Guadarrama National Park in central Spain. In particular, we assessed functional and phylogenetic patterns, including functional heterogeneity, using a multi-scale approach (cells, subplots, and plots) and determined the relevance of key ecological factors (i.e., elevation, potential solar radiation, pH, soil organic carbon, species richness, and functional heterogeneity) that affect functional and phylogenetic patterns at each spatial scale. Overall, at the plot scale, coexisting species tended to be more functionally and phylogenetically similar. By contrast, at the subplot and cell scales, species tended to be more functionally different but phylogenetically similar. Functional heterogeneity at the cell scale was comparable to the variation across plots along the gradient. The relevance of ecological factors that regulate diversity patterns varied among spatial scales. An increase in elevation resulted in functional clustering at larger scales and phylogenetic overdispersion at a smaller scale. The soil pH and organic carbon levels exhibited complex functional patterns, especially at small spatial scales, where an increase in pH led to clustering patterns for the traits related to the leaf economic spectrum (i.e., foliar thickness, specific leaf area, and leaf dry matter content). Our findings confirm the presence of primary environmental filters (coldness and summer drought at our study sites) that constrain the regional species pool, suggesting the presence of additional assembly mechanisms that act at the smallest scale (e.g., micro-environmental gradients and/or species interactions). Functional and phylogenetic relatedness should be determined using a multi-scale approach to help interpret community assembly processes and understand the initial community responses to environmental changes, including ongoing global warming.

Long term relationship between farming damselfish, predators, competitors and benthic habitat on coral reefs of Moorea Island

Understanding the processes that shape biodiversity is essential for effective environmental management. Across the world's coral reefs, algal farming damselfish (Stegastes sp.) modify the surrounding benthic community through their creation of algae "farms". Using a long-term monitoring dataset (2005-2019) from Moorea Island, French Polynesia, we investigated whether the density of dusky damselfish (Stegastes nigricans) is associated with benthic habitat composition, the density of predators and/or competitors, and whether the survey area was inside or outside of a Marine Protected Area (MPA). We found no evidence that benthic cover or number of competitors were associated with dusky damselfish densities, both inside and outside MPAs. In contrast, fluctuations in dusky damselfish densities were negatively associated with the density of predators (e.g. Serranidae, Muraenidae and Scorpaenidae) in the preceding year in non-MPA areas, and both within and outside of MPAs when predator densities were high (2005-2010). These results suggest that healthy predator populations may be important for regulating the abundances of keystone species, such as algal farming damselfish, especially when predator densities are high.

Abundance, not diversity, of host beetle communities determines abundance and diversity of parasitoids in deadwood

Most parasites and parasitoids are adapted to overcome defense mechanisms of their specific hosts and hence colonize a narrow range of host species. Accordingly, an increase in host functional or phylogenetic dissimilarity is expected to increase the species diversity of parasitoids. However, the local diversity of parasitoids may be driven by the accessibility and detectability of hosts, both increasing with increasing host abundance. Yet, the relative importance of these two mechanisms remains unclear. We parallelly reared communities of saproxylic beetle as potential hosts and associated parasitoid Hymenoptera from experimentally felled trees. The dissimilarity of beetle communities was inferred from distances in seven functional traits and from their evolutionary ancestry. We tested the effect of host abundance, species richness, functional, and phylogenetic dissimilarities on the abundance, species richness, and Shannon diversity of parasitoids. Our results showed an increase of abundance, species richness, and Shannon diversity of parasitoids with increasing beetle abundance. Additionally, abundance of parasitoids increased with increasing species richness of beetles. However, functional and phylogenetic dissimilarity showed no effect on the diversity of parasitoids. Our results suggest that the local diversity of parasitoids, of ephemeral and hidden resources like saproxylic beetles, is highest when resources are abundant and thereby detectable and accessible. Hence, in some cases, resources do not need to be diverse to promote parasitoid diversity.

Soil microbiome predictability increases with spatial and taxonomic scale

Soil microorganisms shape ecosystem function, yet it remains an open question whether we can predict the composition of the soil microbiome in places before observing it. Furthermore, it is unclear whether the predictability of microbial life exhibits taxonomic- and spatial-scale dependence, as it does for macrobiological communities. Here, we leverage multiple large-scale soil microbiome surveys to develop predictive models of bacterial and fungal community composition in soil, then test these models against independent soil microbial community surveys from across the continental United States. We find remarkable scale dependence in community predictability. The predictability of bacterial and fungal communities increases with the spatial scale of observation, and fungal predictability increases with taxonomic scale. These patterns suggest that there is an increasing importance of deterministic versus stochastic processes with scale, consistent with findings in plant and animal communities, suggesting a general scaling relationship across biology. Biogeochemical functional groups and high-level taxonomic groups of microorganisms were equally predictable, indicating that traits and taxonomy are both powerful lenses for understanding soil communities. By focusing on out-of-sample prediction, these findings suggest an emerging generality in our understanding of the soil microbiome, and that this understanding is fundamentally scale dependent.

Chemical Similarity of Co-occurring Trees Decreases With Precipitation and Temperature in North American Forests

Plant diversity varies immensely over large-scale gradients in temperature, precipitation, and seasonality at global and regional scales. This relationship may be driven in part by climatic variation in the relative importance of abiotic and biotic interactions to the diversity and composition of plant communities. In particular, biotic interactions may become stronger and more host specific with increasing precipitation and temperature, resulting in greater plant species richness in wetter and warmer environments. This hypothesis predicts that the many defensive compounds found in plants’ metabolomes should increase in richness and decrease in interspecific similarity with precipitation, temperature, and plant diversity. To test this prediction, we compared patterns of chemical and morphological trait diversity of 140 woody plant species among seven temperate forests in North America representing 16.2°C variation in mean annual temperature (MAT), 2,115 mm variation in mean annual precipitation (MAP), and from 10 to 68 co-occurring species. We used untargeted metabolomics methods based on data generated with liquid chromatography-tandem mass spectrometry to identify, classify, and compare 13,480 unique foliar metabolites and to quantify the metabolomic similarity of species in each community with respect to the whole metabolome and each of five broad classes of metabolites. In addition, we compiled morphological trait data from existing databases and field surveys for three commonly measured traits (specific leaf area [SLA], wood density, and seed mass) for comparison with foliar metabolomes. We found that chemical defense strategies and growth and allocation strategies reflected by these traits largely represented orthogonal axes of variation. In addition, functional dispersion of SLA increased with MAP, whereas functional richness of wood density and seed mass increased with MAT. In contrast, chemical similarity of co-occurring species decreased with both MAT and MAP, and metabolite richness increased with MAT. Variation in metabolite richness among communities was positively correlated with species richness, but variation in mean chemical similarity was not. Our results are consistent with the hypothesis that plant metabolomes play a more important role in community assembly in wetter and warmer climates, even at temperate latitudes, and suggest that metabolomic traits can provide unique insight to studies of trait-based community assembly.

A multi-faceted comparative perspective on elevational beta-diversity: the patterns and their causes

The observed patterns and underlying mechanisms of elevational beta-diversity have been explored intensively, but multi-dimensional comparative studies remain scarce. Herein, across distinct beta-diversity components, dimensions and species groups, we designed a multi-faceted comparative framework aiming to reveal the general rules in the observed patterns and underlying causes of elevational beta-diversity. We have found that: first, the turnover process dominated altitudinal patterns of species beta-diversity (β_sim > β_sne), whereas the nestedness process appeared relatively more important for elevational trait dissimilarity (β_funcsim < β_funcsne); second, the taxonomic turnover was relative higher than its phylogenetic and functional analogues (β_sim > β_phylosim/β_funcsim), conversely, nestedness-resultant trait dissimilarity tended to be higher than the taxonomic and phylogenetic measures (β_funcsne > β_sne/β_phylosne); and third, as elevational distance increased, the contradicting dynamics of environmental filtering and limiting similarity have jointly led the elevational patterns of beta-diversity, especially at taxonomic dimension. Based on these findings, we infer that the species turnover among phylogenetic relatives sharing similar functional attributes appears to be the main cause of shaping the altitudinal patterns of multi-dimensional beta-diversity. Owing to the methodological limitation in the randomization approach, currently, it remains extremely challenging to distinguish the influence of the neutral process from the offset between opposing niche-based processes. Despite the complexities and uncertainties during species assembling, with a multi-dimensional comparative perspective, this work offers us several important commonalities of elevational beta-diversity dynamics.

Seedling diversity in actively and passively restored tropical forest understories

Alternative methods for restoring tropical forests influence the ecological processes that shape recruitment of understory species. In turn, the traits of species recruited will influence the ecological processes the forests provide now and over the long term. We assess the phylogenetic and functional structure of seedlings beneath monoculture plantations, mixed-species plantations (both active restoration) and regenerating selectively logged native forests (passive restoration), considering traits of specific leaf area (SLA, including within-species variation), leaf nitrogen and phosphorus content, life-form, potential plant height, and dispersal type. Monoculture plantations comprised seedlings that were more closely related then would be expected by chance (i.e., phylogenetically clustered), and regenerating forest contained species more distantly related then would be expected by chance (i.e., phylogenetically overdispersed). This suggests that seedlings beneath monocultures assemble through environmental filtering and through the dispersal limitation of predictable functional guilds. However, dispersal limitation is frequently overcome by human-assisted dispersal, increasing trait diversity. Comparing SLA values revealed that regenerating forests recruit seedlings with both high and low mean and variation of SLA, leading to higher overall diversity. Regenerating forest seedlings showed signs of environmental filtering, only based on within-species variation of SLA. Regenerating forest understories appear to favor species that show a high intraspecific variation in SLA values (e.g., Pterocarpus indicus Willd.) and at the same time provided habitat for later successional seedlings that show a lower intraspecific variation in SLA (e.g., Canarium luzonicum (Blume) A.Gray). This trait diversity suggests limiting similarity or competitive exclusion may be reduced because of niche differences, allowing species with different traits to coexist. Phylogenetic and functionally distinct species are restricted in their regeneration capacity, many of which are of conservation significance (under the IUCN Red List). Reforestation projects should maximize desired ecological services (including conservation value) by actively managing for the recruitment of species that are phylogenetically and functionally (including intraspecifically) distinct. This management aim will increase the probability of fulfilling a wider array of niche spaces and potentially increase the diversity of ecosystem services provided.

Taxonomic resolution affects host-parasite association model performance

Identifying the factors that structure host–parasite interactions is fundamental to understand the drivers of species distributions and to predict novel cross-species transmission events. More phylogenetically related host species tend to have more similar parasite associations, but parasite specificity may vary as a function of transmission mode, parasite taxonomy or life history. Accordingly, analyses that attempt to infer host−parasite associations using combined data on different parasite groups may perform quite differently relative to analyses on each parasite subset. In essence, are more data always better when predicting host−parasite associations, or does parasite taxonomic resolution matter? Here, we explore how taxonomic resolution affects predictive models of host−parasite associations using the London Natural History Museum's database of host–helminth interactions. Using boosted regression trees, we demonstrate that taxon-specific models (i.e. of Acanthocephalans, Nematodes and Platyhelminthes) consistently outperform full models in predicting mammal-helminth associations. At finer spatial resolutions, full and taxon-specific model performance does not vary, suggesting tradeoffs between phylogenetic and spatial scales of analysis. Although all models identify similar host and parasite covariates as important to such patterns, our results emphasize the importance of phylogenetic scale in the study of host–parasite interactions and suggest that using taxonomic subsets of data may improve predictions of parasite distributions and cross-species transmission. Predictive models of host–pathogen interactions should thus attempt to encompass the spatial resolution and phylogenetic scale desired for inference and prediction and potentially use model averaging or ensemble models to combine predictions from separately trained models.

Phylogenetic Core Groups: a promising concept in search of a consistent methodological framework : Comment to ``A conceptual framework for the phylogenetically-constrained assembly of microbial communities''

In this comment, we analyse the conceptual framework proposed by Aguirre de Cárcer (Microbiome 7:142, 2019), introducing the novel concept of Phylogenetic Core Groups (PCGs). This notion aims to complement the traditional classification in operational taxonomic units (OTUs), widely used in microbial ecology, to provide a more intrinsic taxonomical classification which avoids the use of pre-determined thresholds. However, to introduce this concept, the author frames his proposal in a wider theoretical framework based on a conceptualization of selection that we argue is a tautology. This blurs the subsequent formulation of an assembly principle for microbial communities, favouring that some contradictory examples introduced to support the framework appear aligned in their conclusions. And more importantly, under this framework and its derived methodology, it is not possible to infer PCGs from data in a consistent way. We reanalyse the proposal to identify its logical and methodological flaws and, through the analysis of synthetic scenarios, we propose a number of methodological refinements to contribute towards the determination of PCGs in a consistent way. We hope our analysis will promote the exploration of PCGs as a potentially valuable tool, helping to bridge the gap between environmental conditions and community composition in microbial ecology. Video Abstract.

Ecophylogenetics redux

Species' evolutionary histories shape their present-day ecologies, but the integration of phylogenetic approaches in ecology has had a contentious history. The field of ecophylogenetics promised to reveal the process of community assembly from simple indices of phylogenetic pairwise distances - communities shaped by environmental filtering were composed of closely related species, whereas communities shaped by competition were composed of less closely related species. However, the mapping of ecology onto phylogeny proved to be not so straightforward, and the field remains mired in controversy. Nonetheless, ecophylogenetic methods provided important advances across ecology. For example the phylogenetic distances between species is a strong predictor of pest and pathogen sharing, and can thus inform models of species invasion, coexistence and the disease dilution/amplification effect of biodiversity. The phylogenetic structure of communities may also provide information on niche space occupancy, helping interpret patterns of facilitation, succession and ecosystem functioning - with relevance for conservation and restoration - and the dynamics among species within foodwebs and metacommunities. I suggest leveraging advances in our understanding of the process of evolution on phylogenetic trees would allow the field to progress further, while maintaining the essence of the original vision that proved so seductive.

The mechanism of species coexistence and diversity maintenance along aspects in the northeast of the Qinghai–Tibetan plateau

To examine the role of plant functional traits and phylogenetic relationships in predicting plant community species coexistence and diversity maintenance, we measured 73 species and six functional traits along a slope aspect gradient on the Qinghai–Tibetan plateau. We calculated the net relatedness index (NRI), the nearest taxon index (NTI), phylogenetic diversity (PD), functional diversity, and analysed phylogenetic signals. The results show that the species richness, plant composition, and PD changed substantially from northern to southern aspects, and the phylogenetic structure of the community changed from clustering to over-dispersion. Weak phylogenetic signals in plant height, leaf nitrogen content, and leaf potassium content were recorded. We conclude that the influencing factor(s) of species coexistence on northern and north-western aspects is limiting similarity (interspecific competition), whereas on southern and south-western aspects, habitat filtering (environmental effect) is predominant. On western aspects, the influencing factors are driven by three processes: limiting similarity, habitat filtration, and random processes. Results suggest that niche processes (including habitat filtration and limiting similarity) are the main mechanisms for species coexistence and diversity maintenance on aspects of the alpine meadow in the northeast of the Qinghai–Tibetan plateau, while random processes appear at the transitional zone (the western aspect in our study) between aspects.

Latitudinal and elevational patterns of phylogenetic structure in forest communities in China's mountains

The phylogenetic structure incorporates both ecological and evolutionary processes to explain assembly of a local community. The "phylogenetic niche conservatism" (PNC) hypothesis suggests that distributions of species along environmental gradients reflect both ancestral traits and ecological fitness of individual species The temperature is generally regarded to change in similar ways along both latitudinal and elevational gradients but with different historical contingence. Therefore, comparing the latitudinal and elevational patterns of phylogenetic structure of communities is of help to depict the effects of ecological and evolutionary processes in shaping the community assembly. In this study, we explored the latitudinal, elevational and climatic patterns of phylogenetic structure of 569 angiosperm tree communities from 38 mountains across China. We found a larger mean abundance-weighted net relatedness index (NRI) than the presence/absence-based NRI; and the NRI decreased when the species pool downscaled from the full pool to county-level pool. The mean family age and phylogenetic species evenness decreased with latitude, and increased with temperature of the coldest month and precipitation; whilst NRI increased with latitude, and decreased with mean temperature of the coldest month. In most mountains, NRI, mean family age and phylogenetic species evenness showed non-significant trends along the elevational gradient. Our results support the main predictions of PNC for the latitudinal gradient, i.e., species tend to be more phylogenetically related to each other and clades are younger in temperate environments, compared to those in tropical environments. We suggested that independent species pools and abundance should be incorporated in analysis to fully represent the phylogenetic structure of communities.

Global functional and phylogenetic structure of avian assemblages across elevation and latitude

Mountain systems are exceptionally species rich, yet the associated elevational gradients in functional and phylogenetic diversity and their consistency across latitude remain little understood. Here, we document how avian functional and phylogenetic diversity and structure vary along all major elevational gradients worldwide and uncover strong latitudinal differences. Assemblages in warm tropical lowlands and cold temperate highlands are marked by high functional overdispersion and distinctiveness, whereas tropical highlands and temperate lowlands appear strongly functionally clustered and redundant. We additionally find strong geographic variation in the interplay of phylogenetic and functional structure, with strongest deviations between the two in temperate highlands. This latitudinal and elevational variation in assemblage functional structure is underpinned by nuanced shifts in the position, shape and composition of multivariate trait space. We find that, independent of latitude, high-elevation assemblages emerge as exceptionally susceptible to functional change.

Heterospecific mating interactions as an interface between ecology and evolution

Reproductive interference (costly interspecific sexual interactions) is well-understood to promote divergence in mating-relevant traits (i.e. reproductive character displacement: RCD), but it can also reduce population growth, eventually leading to local extinction of one of the species. The ecological and evolutionary processes driven by reproductive interference can interact with each other. These interactions are likely to influence whether the outcome is coexistence or extinction, but remain little studied. In this paper, we first develop an eco-evolutionary perspective on reproductive interference by integrating ecological and evolutionary processes in a common framework. We also present a simple model to demonstrate the eco-evolutionary dynamics of reproductive interference. We then identify a number of factors that are likely to influence the relative likelihoods of extinction or RCD. We discuss particularly relevant factors by classifying them into four categories: the nature of the traits responding to selection, the mechanisms determining the expression of these traits, mechanisms of reproductive interference and the ecological background. We highlight previously underappreciated ways in which these factors may influence the relative likelihoods of RCD and local extinction. By doing so, we also identify questions and future directions that will increase our holistic understanding of the outcomes of reproductive interference.

Assembly rules of helminth parasite communities in grey mullets: combining components of diversity

Organisms aggregate in ecological communities. It has been widely debated whether these associations are explained by deterministic or, in contrast, random processes. The answer may vary, depending on the level of an organisational scale (α, β and γ) and the facet of diversity considered: taxonomic, functional and phylogenetic. Diversity at the level of a sampling unit (i.e. host individual) is the α diversity; β diversity represents the extent of dissimilarity in diversity among sampling units (within a level of an organisational scale, β1; between levels of an organisational scale, β2); and the total diversity of a system is γ diversity. Thus, the combination of facets and levels of a scale may be useful to disentangle the mechanisms driving the composition of a parasite community. Using helminth parasite taxonomic, functional, and a proxy for phylogenetic diversity of three species of grey mullets (Teleostei: Mugilidae) from the Mediterranean Sea, we show that random and deterministic processes of different nature explain the assemblage of parasite communities. The parasite community at a host individual (α) was invariably a random subset of the total diversity in the community for the three facets of diversity. At the β1 level, taxonomic diversity was lower than expected by chance, whereas functional diversity and the proxy for phylogenetic diversity were random. At the β2 level, diversity patterns suggested environmental filtering of the parasite assemblage: species, trait, and phylogenetic compositions of parasite communities seemed to depend primarily on the species of host, but also on the locality and season. Our study shows that parasite communities are not totally understood if any of the components (i.e. facets and levels) of diversity is neglected.

A phylogenetic and trait-based analysis of community assembly in a subtropical forest in central China

Despite several decades of study in community ecology, the relative importance of the ecological processes that determine species co-occurrence across spatial scales remains uncertain. Some of this uncertainty may be reduced by studying the scale dependency of community assembly in the light of environmental variation. Phylogenetic information and functional trait information are often used to provide potentially valuable insights into the drivers of community assembly. Here, we combined phylogenetic and trait-based tests to gain insights into community processes at four spatial scales in a large stem-mapped subtropical forest dynamics plot in central China. We found that all of the six leaf economic traits measured in this study had weak, but significant, phylogenetic signal. Nonrandom phylogenetic and trait-based patterns associated with topographic variables indicate that deterministic processes tend to dominate community assembly in this plot. Specifically, we found that, on average, co-occurring species were more phylogenetically and functionally similar than expected throughout the plot at most spatial scales and assemblages of less similar than expected species could only be found on finer spatial scales. In sum, our results suggest that the trait-based effects on community assembly change with spatial scale in a predictable manner and the association of these patterns with topographic variables, indicates the importance of deterministic processes in community assembly relatively to random processes.