Elevational patterns of fern species assemblages and richness in central Japan

We conducted field surveys in 807 quadrats to evaluate the elevational belts, boundary and richness patterns of ferns and lycophytes in the temperate region of central Japan. We analysed fern species assemblages at 100 m elevational steps by cluster analysis and tested the number of upper and lower boundaries for elevational intervals against a null model of random distribution of elevational limits. We compared the pattern of fern species richness along the elevational gradients in central Japan with patterns in several locations to evaluate the fern flora in central Japan in relation to the rest of the world. We recorded 261 ferns species in total, which is one-third of the Japanese ferns. We found clear elevational boundaries of fern assemblages at 900 and 1,800 m and three fern elevational zones, which corresponded well to the elevational limits of forest types in central Japan. The pattern of fern species richness in central Japan was an asymmetric hump-shaped pattern that peaked close to the sea level, with the peak of local richness at lower elevations than that of regional richness. We found that the peak of fern species richness along the elevational gradient in Japan was located at lower elevations than that of fern elevational patterns in several locations around the world.     

Phylogenetic diversity,trait diversity and niches: species assembly of ferns along a tropical elevational gradient

Aim To analyse the structure of pteridophyte assemblages, based on phylogenetic relatedness and trait properties, along an elevational gradient. Ecological theory predicts that co‐occurring species may be: randomly selected from a regional pool; ecologically sorted so that they are functionally different hence resulting in reduced competition (overdispersion); or functionally similar as an adaptation to specific ecological conditions (clustering). Location Braulio Carrillo National Park and Cerro de la Muerte, Costa Rica, Central America. Methods We used an empirical dataset of the quantitative pattern of species occurrences and individual numbers of ferns within 156 plots along a tropical elevational gradient to test whether directed ecological sorting might cause deviations in patterns of trait and phylogenetic diversity. Mean pairwise distances of species based on phylogenetic and trait properties were compared with two different sets of null assemblages, one maintaining species frequency distributions (constrained) and one not (unconstrained). Results Applying different null models resulted in varying degrees of overdispersion and clustering, but overall patterns of deviation from random expectations remained the same. Contrary to theoretical predictions, phylogenetic and trait diversity were relatively independent from one another. Phylogenetic diversity showed no patterns along the elevational gradient, whereas trait diversity showed significant trends for epiphytes. Main conclusions Under stressful environmental conditions (drought at low elevations and frost at high elevations), epiphytic fern assemblages tended to be clustered with respect to trait characteristics, which suggests environmental filtering. Conversely, under less extreme environmental conditions (middle of the transect), the sorting was biased towards high differentiation (overdispersion), presumably because of interspecific competition and trait shifts among closely related species (character displacement).     

Phylogenetic diversity of macromycetes and woody plants along an elevational gradient in Eastern Mexico

Phylogenetic information provides insight into the ecological and evolutionary processes that organize species assemblages. We compared patterns of phylogenetic diversity among macromycete and woody plant communities along a steep elevational gradient in eastern Mexico to better understand the evolutionary processes that structure their communities. Macrofungi and trees were counted and identified in eight sites from 100 to 3500 m asl, and sequence data retrieved from GenBank for the same or closely related species were used to reconstruct their phylogenies. Patterns of species richness and phylogenetic diversity were similar for both macrofungi and trees, but macromycete richness and diversity peaked at mid‐elevations, whereas woody plant richness and diversity did not show significant trends with elevation. Phylogenetic similarity among sites was low for both groups and decreased as elevational distance between sites increased. Macromycete communities displayed phylogenetic overdispersion at low elevations and phylogenetic clustering at high elevations; the latter is consistent with environmental filtering at high elevation sites. Woody plants generally exhibited phylogenetic clustering, consistent with the potential importance of environmental filtering throughout the elevational gradient.     

Altitude acts as an environmental filter on phylogenetic composition,traits and diversity in bee communities

Knowledge about the phylogeny and ecology of communities along environmental gradients helps to disentangle the role of competition-driven processes and environmental filtering for community assembly. In this study, we evaluated patterns in species richness, phylogenetic structure and life-history traits of bee communities along altitudinal gradients in the Alps, Germany. We found a linear decline in species richness and abundance but increasing phylogenetic clustering in communities with increasing altitude. The proportion of social- and ground-nesting species, as well as mean body size and altitudinal range of bee communities, increased with increasing altitude, whereas the mean geographical distribution decreased. Our results suggest that community assembly at high altitudes is dominated by environmental filtering effects, whereas the relative importance of competition increases at low altitudes. We conclude that inherent phylogenetic and ecological species attributes at high altitudes pose a threat for less competitive alpine specialists with ongoing climate change.     

Joint effect of phylogenetic relatedness and trait selection on the elevational distribution of Rhododendron species

Congeneric species may coexist at fine spatial scales through niche differentiation, however, the magnitude to which the effects of functional traits and phylogenetic relatedness contribute to their distribution along elevational gradients remains understudied. To test the hypothesis that trait and elevational range overlap can affect local speciesʼ coexistence, we first compared phylogenetic relatedness and trait (including morphological traits and leaf elements) divergence among closely related species of Rhododendron L. on Yulong Mountain, China. We then assessed relationships between the overlap of multiple functional traits and the degree of elevational range overlap among species pairs in a phylogenetic context. We found that phylogeny was a good predictor for most functional traits, where closely related species showed higher trait similarity and occupied different elevational niches at our study site. Species pairs of R. subgen. Hymenanthes (Blume) K. Koch showed low elevational range overlap and some species pairs of R. subgen. Rhododendron showed obvious niche differentiation. Trait divergence is greater for species in R. subgen. Rhododendron, and it plays an important role between species pairs with low elevational range overlap. Trait convergent selection takes place between co-occurring closely related species that have high elevational range overlap, which share more functional trait space due to environmental filtering or ecological adaptation in more extreme habitats. Our results highlight the importance of evolutionary history and trait selection for species coexistence at fine ecological scales along environmental gradients.     

The roles of environment,space, and phylogeny in determining functional dispersion of rodents (Rodentia) in the Hengduan Mountains,China

The recently described trait‐based approach is becoming widely popular for a mechanistic understanding of species coexistence. However, the greatest challenge in functional analyses is decomposing the contributions of different ecological and evolutionary processes (e.g., niche‐based process, neutral process, and evolutionary process) in determining trait structure. Taking rodents (Rodentia) in the Hengduan Mountains as our study model, we aim to (1) quantify the vertical patterns of functional structure for head–body length (HL), tail/body ratio (TR), animal component in diet (ACD), and all traits; (2) disentangle the relative importance of different assembly processes (environment, space, and phylogeny) in structuring trait dispersion; and (3) assess the feasibility of Bergmann's rule and Allen's rule along elevational gradient. Our results have suggested that the vertical functional structure pattern varied across these three traits, indicating distinct functional roles in the community assembly process. These nonrandom vertical patterns of HL, TR, and terminal ACD have demonstrated these traits were dominated by different ecological process along environmental gradient. In variance partitioning, high proportion of the spatial variations in trait dispersion was explained by environmental and spatial models, which have provided supporting strong evidence for niche‐based and neutral processes in leading species coexistence. Although the three traits all exhibited apparent phylogenetic signals, phylogenetic relationship within community failed to predict the spatial variations of functional dispersion, confirming the enormous inference of phylogenetic signals in predicting trait structure. By assessing the vertical patterns of HL and TR at order and family levels, we argued that functional adaptation along an environmental gradient is a surrogate of series of complex processes (e.g., environmental filtering, interspecific interaction, and neutral dispersal) acting on multiple functional axes, which results in inconsistence with the empirical rules along elevational gradient.     

The origin and maintenance of montane diversity: integrating evolutionary and ecological processes

Determining how ecological and evolutionary processes produce spatial variation in local species richness remains an unresolved challenge. Using mountains as a model system, we outline an integrative research approach to evaluate the influence of ecological and evolutionary mechanisms on the generation and maintenance of patterns of species richness along and among elevational gradients. Biodiversity scientists interested in patterns of species richness typically start by documenting patterns of species richness at regional and local scales, and based on their knowledge of the taxon, and the environmental and historical characteristics of a mountain region, they then ask whether diversity–environment relationships, if they exist, are explained mostly by ecological or evolutionary hypotheses. The final step, and perhaps most challenging one, is to tease apart the relative influence of ecological and evolutionary mechanisms. We propose that elucidating the relative influence of ecological and evolutionary mechanisms can be achieved by taking advantage of the replicated settings afforded by mountains, combined with targeted experiments along elevational gradients. This approach will not only identify potential mechanisms that drive patterns of species richness, but also allow scientists to generate more robust hypotheses about which factors generate and maintain local diversity.     

Mountain metacommunities: climate and spatial connectivity shape ant diversity in a complex landscape

Understanding what drives biodiversity patterns across scales is a central goal of ecology. Both environmental gradients and spatial landscape structure have been found to be important factors influencing species distributions and community composition, and partly reflect the balance of underlying deterministic and stochastic community processes. In some systems, environmental gradients and spatial connectivity are intertwined in that steep environmental gradients serve as boundaries on species movements and impose environment‐derived complex spatial structure to metacommunities. Mountainous landscapes are prime examples of this, and recent theory has linked principles of geomorphology, environmental gradients, and spatial structure to make predictions for resulting community patterns. In this context, we examine variation in taxonomic and phylogenetic ant diversity patterns along a geographic transect spanning > 5000 m in elevational range in the Hengduan mountains of southern China. We found that environmental gradients dominate variation in both alpha and beta diversity in this landscape, with alpha diversity strongly declining with elevation and beta diversity driven by elevational differences. However, within an elevational band spatial connectivity predicts beta diversity better than geographic distance. Our findings deviate from theoretical predictions in several ways, notably alpha diversity is monotonically declining and within‐band beta diversity is invariant with increasing elevation. The discrepancies between theory and observation may be explained by differences in the Hengduan landscape from idealized fluvial landscapes, such as a lack of a mid‐elevation peak in connectivity, as well as evolutionary limits on the source pool of species available to populate metacommunities at different elevations. The latter is supported by variation in phylogenetic community structure with elevation. Our results demonstrate the power of conceptual, statistical, and theoretical frameworks that integrate the roles of environment and spatial structure in metacommunities, but that additional work is needed to bridge the gap between abstract theory and real systems.     

The impact of population processes on patterns of species richness: Lessons from elevational gradients

In the last few years, considerable headway has been made towards understanding patterns of species richness along latitudinal and elevational gradients, mostly by focussing on the influences of surface area, climatic factors, evolutionary history, and stochastic processes. However, the potential impact of population-level processes in determining or modifying patterns of species richness has largely been neglected, partly due to the difficulty of gathering such data for numerous species along geographical or ecological gradients. Based on two empirical examples, I here show that dispersal and the resulting source-sink effects modify patterns of plant species richness along elevation gradients, and that the inclusion or exclusion of such sink populations alters the perception of the diversity patterns and hence our interpretation of them. I argue that population processes should be taken into account when studying patterns of species richness, especially at scales at which dispersal is common in the taxon under consideration.     

Elevational filtering and the evolution of planthoppers (Hemiptera,Fulgoromorpha) in Papua New Guinea

Along elevational gradients, phylogenetic relatedness patterns constitute a considerable source of information and may shed light on ecological processes that structure communities. This study focuses on community phylogenetic structure of planthoppers, specifically the species-rich and abundant Fulgoromorpha families (Hemiptera, Auchenorrhyncha), Cixiidae and Derbidae + Achilidae, along an elevational gradient on Mount Wilhelm (Papua New Guinea). In order to assess the factors driving planthoppers community composition, we recorded abundance data for planthoppers species at each elevation and we generated a molecular phylogeny of the local species, using Bayesian inference. We analyzed 168 individuals representing 59 local morphospecies. Using a fully resolved and well-supported phylogeny, we then investigated the phylogenetic structure of the communities by performing a Spatial Analysis of Community Diversity. We show that Cixiidae are phylogenetically clustered along the elevational gradient, whereas Derbidae + Achilidae harbor a random structure, suggesting that local adaptation to elevation shapes community structure of Cixiidae, but not that of Derbidae + Achilidae. Our findings highlight the importance of phylogenies in the study of tropical elevational gradients.     

The impact of sterile populations on the perception of elevational richness patterns in ferns

Dispersal may influence the spatial distribution of species richness through mass or source‐sink effects, but the extent of sink populations at the community level remains largely unknown due to difficulties of identifying such populations. We compared the richness patterns of ferns in 333 plots along six tropical elevational gradients in America, the Mascarenes, and southeast Asia, using sterile populations as an indication of sink populations. First, we tested whether sterile fern records were more common towards the elevational range limits of the individual species, but found this pattern in only one out of ten cases. It is therefore uncertain if sterile records correspond to marginal sink populations. Second, we compared the elevational richness patterns of sterile and fertile species. In several cases, elevational trends for sterile and fertile records were quite similar, but in others they differed distinctly. The percentage of sterile records per plot decreased with elevation among epiphytic ferns along all six transects, whereas terrestrials showed mixed results (decrease, increase, and U‐shaped patterns). The percentage of sterile species records per plot relative to the number of species per plot recovered four significant patterns among the twelve cases analysed: higher percentages at higher species numbers among terrestrial ferns on two transects and lower percentages among epiphytes on two others. Despite the problems with equating sterile records to sink populations, we thus found distinct elevational patterns of sterile records that clearly affected our perception of the overall richness patterns. Ignoring the impact of population dynamics on diversity patterns is thus liable to result in misinterpretations of the diversity patterns.     

附生蕨类植物的克隆性研究进展

石松类及蕨类植物在高等植物中处于比较特殊的进化与系统发育地位, 同时具有孢子植物(孢子)与种子植物(维管束)的双重特征。附生蕨类植物是蕨类植物中占据独特生境的一个大类群, 其生活史策略及进化历史与其附生生长的森林生态系统紧密相关。大部分附生蕨类植物的克隆生长习性及克隆生活史性状在其生态适应中具有重要作用, 但这方面未引起广泛关注。本文主要综述了中国山地森林中附生蕨类植物的根状茎克隆生长、克隆性与生态适应性、不同克隆生长方式与进化等方面, 并展望了蕨类植物克隆性在森林生态系统过程与功能中的作用, 以及今后如何将蕨类植物生态学研究与气候变化、植被恢复、土地利用变化等全球变化的主流方向进行结合。     

A taxonomic,functional, and phylogenetic perspective on the community assembly of passerine birds along an elevational gradient in southwest China

Integrating multiple facets of biodiversity to describe spatial and temporal distribution patterns is one way of revealing the mechanisms driving community assembly. We assessed the species, functional, and phylogenetic composition and structure of passerine bird communities along an elevational gradient both in wintering and breeding seasons in the Ailao Mountains, southwest China, in order to identify the dominant ecological processes structuring the communities and how these processes change with elevation and season. Our research confirms that the highest taxonomic diversity, and distinct community composition, was found in the moist evergreen broadleaf forest at high elevation in both seasons. Environmental filtering was the dominant force at high elevations with relatively cold and wet climatic conditions, while the observed value of mean pairwise functional and phylogenetic distances of low elevation was constantly higher than expectation in two seasons, suggested interspecific competition could play the key role at low elevations, perhaps because of relative rich resource result from complex vegetation structure and human‐induced disturbance. Across all elevations, there was a trend of decreasing intensity of environmental filtering whereas increasing interspecific competition from wintering season to breeding season. This was likely due to the increased resource availability but reproduction‐associated competition in the summer months. In general, there is a clear justification for conservation efforts to protect entire elevational gradients in the Ailao Mountains, given the distinct taxonomic, functional, and phylogenetic compositions and also elevational migration pattern in passerine bird communities.     

Measuring biodiversity to explain community assembly: a unified approach

One of the oldest challenges in ecology is to understand the processes that underpin the composition of communities. Historically, an obvious way in which to describe community compositions has been diversity in terms of the number and abundances of species. However, the failure to reject contradictory models has led to communities now being characterized by trait and phylogenetic diversities. Our objective here is to demonstrate how species, trait and phylogenetic diversity can be combined together from large to local spatial scales to reveal the historical, deterministic and stochastic processes that impact the compositions of local communities. Research in this area has recently been advanced by the development of mathematical measures that incorporate trait dissimilarities and phylogenetic relatedness between species. However, measures of trait diversity have been developed independently of phylogenetic measures and conversely most of the phylogenetic diversity measures have been developed independently of trait diversity measures. This has led to semantic confusions particularly when classical ecological and evolutionary approaches are integrated so closely together. Consequently, we propose a unified semantic framework and demonstrate the importance of the links among species, phylogenetic and trait diversity indices. Furthermore, species, trait and phylogenetic diversity indices differ in the ways they can be used across different spatial scales. The connections between large‐scale, regional and local processes allow the consideration of historical factors in addition to local ecological deterministic or stochastic processes. Phylogenetic and trait diversity have been used in large‐scale analyses to determine how historical and/or environmental factors affect both the formation of species assemblages and patterns in species richness across latitude or elevation gradients. Both phylogenetic and trait diversity have been used at different spatial scales to identify the relative impacts of ecological deterministic processes such as environmental filtering and limiting similarity from alternative processes such as random speciation and extinction, random dispersal and ecological drift. Measures of phylogenetic diversity combine phenotypic and genetic diversity and have the potential to reveal both the ecological and historical factors that impact local communities. Consequently, we demonstrate that, when used in a comparative way, species, trait and phylogenetic structures have the potential to reveal essential details that might act simultaneously in the assembly of species communities. We highlight potential directions for future research. These might include how variation in trait and phylogenetic diversity alters with spatial distances, the role of trait and phylogenetic diversity in global‐scale gradients, the connections between traits and phylogeny, the importance of trait rarity and independent evolutionary history in community assembly, the loss of trait and phylogenetic diversity due to human impacts, and the mathematical developments of biodiversity indices including within‐species variations.     

Using Plant Functional Traits and Phylogenies to Understand Patterns of Plant Community Assembly in a Seasonal Tropical Forest in Lao PDR

Plant functional traits reflect different evolutionary responses to environmental variation, and among extant species determine the outcomes of interactions between plants and their environment, including other plant species. Thus, combining phylogenetic and trait-based information can be a powerful approach for understanding community assembly processes across a range of spatial scales. We used this approach to investigate tree community composition at Phou Khao Khouay National Park (18°14’-18°32’N; 102°38’- 102°59’E), Laos, where several distinct forest types occur in close proximity. The aim of our study was to examine patterns of plant community assembly across the strong environmental gradients evident at our site. We hypothesized that differences in tree community composition were being driven by an underlying gradient in soil conditions. Thus, we predicted that environmental filtering would predominate at the site and that the filtering would be strongest on sandier soil with low pH, as these are the conditions least favorable to plant growth. We surveyed eleven 0.25 ha (50x50 m) plots for all trees above 10 cm dbh (1221 individual trees, including 47 families, 70 genera and 123 species) and sampled soils in each plot. For each species in the community, we measured 11 commonly studied plant functional traits covering both the leaf and wood economic spectrum traits and we reconstructed a phylogenetic tree for 115 of the species in the community using rbcL and matK sequences downloaded from Genebank (other species were not available). Finally we compared the distribution of trait values and species at two scales (among plots and 10x10m subplots) to examine trait and phylogenetic community structures. Although there was strong evidence that an underlying soil gradient was determining patterns of species composition at the site, our results did not support the hypothesis that the environmental filtering dominated community assembly processes. For the measured plant functional traits there was no consistent pattern of trait dispersion across the site, either when traits were considered individually or when combined in a multivariate analysis. However, there was a significant correlation between the degree of phylogenetic dispersion and the first principle component axis (PCA1) for the soil parameters. Moreover, the more phylogenetically clustered plots were on sandier soils with lower pH. Hence, we suggest that the community assembly processes across our site may reflect the influence of more conserved traits that we did not measure. Nevertheless, our results are equivocal and other interpretations are possible. Our study illustrates some difficulties in combining trait and phylogenetic approaches that may result from the complexities of integrating spatial and evolutionary processes that vary at different scales.     

Phylogenetic analysis of community assembly and structure over space and time

Evolutionary ecologists are increasingly combining phylogenetic data with distributional and ecological data to assess how and why communities of species differ from random expectations for evolutionary and ecological relatedness. Of particular interest have been the roles of environmental filtering and competitive interactions, or alternatively neutral effects, in dictating community composition. Our goal is to place current research within a dynamic framework, specifically using recent phylogenetic studies from insular environments to provide an explicit spatial and temporal context. We compare communities over a range of evolutionary, ecological and geographic scales that differ in the extent to which speciation and adaptation contribute to community assembly and structure. This perspective allows insights into the processes that can generate community structure, as well as the evolutionary dynamics of community assembly.     

Neutral lipid fatty acid composition as trait and constraint in Collembola evolution

Functional traits determine the occurrence of species along environmental gradients and their coexistence with other species. Understanding how traits evolved among coexisting species helps to infer community assembly processes. We propose fatty acid composition in consumer tissue as a functional trait related to both food resources and physiological functions of species. We measured phylogenetic signal in fatty acid profiles of 13 field‐sampled Collembola (springtail) species and then combined the data with published fatty acid profiles of another 24 species. Collembola fatty acid profiles generally showed phylogenetic signal, with related species resembling each other. Long‐chain polyunsaturated fatty acids, related to physiological functions, demonstrated phylogenetic signal. In contrast, most food resource biomarker fatty acids and the ratios between bacterial, fungal, and plant biomarker fatty acids exhibited no phylogenetic signal. Presumably, fatty acids related to physiological functions have been constrained during Collembola evolutionary history: Species with close phylogenetic affinity experienced similar environments during divergence, while niche partitioning in food resources among closely related species favored species coexistence. Measuring phylogenetic signal in ecologically relevant traits of coexisting species provides an evolutionary perspective to contemporary assembly processes of ecological communities. Integrating phylogenetic comparative methods with community phylogenetic and trait‐based approaches may compensate for the limitations of each method when used alone and improve understanding of processes driving and maintaining assembly patterns.     

Fern species richness along a central Himalayan elevational gradient, Nepal

Aim The study explores fern species richness patterns along a central Himalayan elevational gradient (100–4800 m a.s.l.) and evaluates factors influencing the spatial increase and decrease of fern richness. Location The Himalayas stretch from west to east by 20°, i.e. 75–95° east, and Nepal is located from 80 to 88° east in this range. Methods We used published data of the distribution of ferns and fern allies to interpolate species elevational ranges. Defining species presence between upper and lower elevation limit is the basis for richness estimates. The richness pattern was regressed against the total number of rainy days, and gradients that are linearly related to elevation, such as length of the growing season, potential evapotranspiration (PET, energy), and a moisture index (MI = PET/mean annual rainfall). The regressions were performed by generalized linear models. Results A unimodal relationship between species richness and elevation was observed, with maximum species richness at 2000 m. Fern richness has a unimodal response along the energy gradients, and a linear response with moisture gradients. Main conclusions The study confirms the importance of moisture on fern distributions as the peak coincides spatially with climatic factors that enhance moisture levels; the maximum number of rainy days and the cloud zone. Energy‐related variables probably control species richness directly at higher elevations but at the lower end the effect is more probably related to moisture.     

Species richness and trait composition of butterfly assemblages change along an altitudinal gradient

Species richness patterns along altitudinal gradients are well-documented ecological phenomena, yet very little data are available on how environmental filtering processes influence the composition and traits of butterfly assemblages at high altitudes. We have studied the diversity patterns of butterfly species at 34 sites along an altitudinal gradient ranging from 600 to 2,000 m a.s.l. in the National Park Berchtesgaden (Germany) and analysed traits of butterfly assemblages associated with dispersal capacity, reproductive strategies and developmental time from lowlands to highlands, including phylogenetic analyses. We found a linear decline in butterfly species richness along the altitudinal gradient, but the phylogenetic relatedness of the butterfly assemblages did not increase with altitude. Compared to butterfly assemblages at lower altitudes, those at higher altitudes were composed of species with larger wings (on average 9 %) which laid an average of 68 % more eggs. In contrast, egg maturation time in butterfly assemblages decreased by about 22 % along the altitudinal gradient. Further, butterfly assemblages at higher altitudes were increasingly dominated by less widespread species. Based on our abundance data, but not on data in the literature, population density increased with altitude, suggesting a reversed density–distribution relationship, with higher population densities of habitat specialists in harsh environments. In conclusion, our data provide evidence for significant shifts in the composition of butterfly assemblages and for the dominance of different traits along the altitudinal gradient. In our study, these changes were mainly driven by environmental factors, whereas phylogenetic filtering played a minor role along the studied altitudinal range.