Epiphytic bryophyte diversity and range distributions along an elevational gradient in Marojejy,Madagascar

Describing spatial variation in species richness and understanding its links to ecological mechanisms are complementary approaches for explaining geographical patterns of richness. The study of elevational gradients holds enormous potential for understanding the factors underlying global diversity. This paper investigates the pattern of species richness and range-size distribution of epiphytic bryophytes along an elevational gradient in Marojejy National Park, northeast Madagascar. The main objectives are to describe bryophyte species composition and endemism in Marojejy National Park, to describe the species richness and distribution patterns of epiphytic bryophytes along an elevational gradient from 250 m to 2050 m and to evaluate the explanatory value of environmental variables for the observed patterns. Bryophyte samples were collected following a nested design with four hierarchical levels: elevational belts, plots, quadrats, and microplots. In total, 254 epiphytic bryophyte species were recorded, comprising 157 liverworts and 97 mosses. Twenty-three of these are endemic to Madagascar. Species richness exhibits a hump-shaped pattern along the elevational gradient, peaking at 1,250 m. Eighty-seven percent of the total recorded species have a range distribution lower than 1,000 m, at which point 36% are restricted to these single elevations. Our results suggest that mean temperature, relative humidity, and vapor pressure deficit play important roles in shaping the richness pattern observed in this study. While the liverwort richness pattern did not correlate to vapor pressure deficit and responded only weakly to relative humidity, the richness pattern shown by mosses correlates well with mean temperature, relative humidity, and vapor pressure deficit.     

Latitudinal diversity gradients in bryophytes and woody plants: Roles of temperature and water availability

It remains unclear whether the latitudinal diversity gradients of micro- and macro-organisms are driven by the same macro-environmental variables. We used the newly completed species catalog and distribution information of bryophytes in China to explore their spatial species richness patterns, and to investigate the underlying roles of energy availability, climatic seasonality, and environmental heterogeneity in shaping these patterns. We then compared these patterns to those found for woody plants. We found that, unlike woody plants, mosses and liverworts showed only weakly negative latitudinal trends in species richness. The spatial patterns of liverwort richness and moss richness were overwhelmingly explained by contemporary environmental variables, although explained variation was lower than that for woody plants. Similar to woody plants, energy and climatic seasonality hypotheses dominate as explanatory variables but show high redundancy in shaping the distribution of bryophytes. Water variables, that is, the annual availability, intra-annual variability and spatial heterogeneity in precipitation, played a predominant role in explaining spatial variation of species richness of bryophytes, especially for liverworts, whereas woody plant richness was affected most by temperature variables. We suggest that further research on spatial patterns of bryophytes should incorporate the knowledge on their ecophysiology and evolution.     

Post-fire bryophyte dynamics in Mediterranean vegetation

Abstract. Bryophyte dynamics after fire in the Mediterranean macchia of Southern Italy was studied both by diachronic and synchronic approaches. Changes of bryophyte cover and species composition were found in relation to both age and fire intensity. During the first 2 yr after fire, bryophytes dominated the plots which had experienced the highest fire intensity while herbs were dominant in plots affected by lighter fires. Pioneer species, such as Funaria hygrometrica, Barbula convoluta and Bryum dunense, characterized recent intense fires, whereas Bryum torquescens, B. radiculosum and B. ruderale were dominant after less intense burning. Pleurochaete squarrosa, Tortula ruraliformis and Tortella flavovirens dominated intermediate successional stages. Pleurocarpous mosses were dominant only in the older closed stands. Different patterns of regeneration strategies were described: spores dominated early stages of intense fire, while vegetative propagules characterized later successional stages and less severely burned areas. Although bryophytes usually have a low abundance in Mediterranean vegetation, their role in post-fire vegetation dynamics may be locally enhanced according to burning conditions.     

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.     

Functional diversity decreases with temperature in high elevation ant fauna

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西藏横断山区溪流细菌beta多样性组分对气候和水体环境的响应

理解沿环境或空间梯度的群落组成变化(即beta多样性)一直是生态学和保护生物学的中心问题, 且beta多样性的形成机制及其对环境的响应已成为当前生物多样性研究的热点问题。本文以西藏横断山区怒江和澜沧江两个流域入江溪流中的细菌为研究对象, 使用Baselga的beta多样性分解方法, 基于Sørensen相异性指数将细菌的beta多样性分解为周转(turnover)和嵌套(nestedness)两个组分, 探究了细菌beta多样性及其分解组分随海拔距离的分布模式, 并且衡量了环境、气候和空间因子的相对重要性。结果表明, 两个流域中细菌的群落结构显著不同。两个流域的细菌总beta多样性和周转组分随海拔距离的增加而增加, 周转组分占总beta多样性的比例较大。气候和环境因子是两个流域中细菌总beta多样性及周转过程的重要预测因子, 并且所有的显著因子均为正相关, 其中环境因子中相关性最高的为海拔距离(R ²= 0.408, P < 0.001), 而气候因子中相关性最高的为年均温差(R ²= 0.417, P < 0.001)。方差分解结果暗示嵌套组分主要受空间扩散的影响; 总beta多样性和周转组分在环境较恶劣的澜沧江主要受环境过滤的影响, 而在环境较温和的怒江主要受空间扩散和环境过滤的共同影响。此外, 较为恶劣的环境条件会增加细菌的总beta多样性和周转率, 并且会形成更强的环境筛选作用去影响细菌群落的物种组成。我们的研究表明对西藏横断山区水体细菌多样性的保护需要从整个流域入手, 而非少量的生物多样性热点地区。     

Epiphytic ferns and bryophytes of Tasmanian tree‐ferns: A comparison of diversity and composition between two host species

Abstract Ferns, bryophytes and lichens are the most diverse groups of plants in wet forests in south‐eastern Australia. However, management of this diversity is limited by a lack of ecological knowledge of these groups and the difficulty in identifying species for non‐experts. These problems may be alleviated by the identification and characterization of suitable proxies for this diversity. Epiphytic substrates are potential proxies. To evaluate the significance of some epiphytic substrates, fern and bryophyte assemblages on a common tree‐fern species, Dicksonia antarctica (soft tree‐fern), were compared with those on a rare species, Cyathea cunninghamii (slender tree‐fern), in eastern Tasmania, Australia. A total of 97 fern and bryophyte species were recorded on D. antarctica from 120 trunks at 10 sites, and 64 species on C. cunninghamii from 39 trunks at four of these sites. The trunks of C. cunninghamii generally supported fewer species than D. antarctica, but two mosses (particularly Hymenodon pilifer) and one liverwort showed significant associations with this host. Several other bryophytes and epiphytic ferns showed an affinity for the trunks of D. antarctica. Species assemblages differed significantly between both sites and hosts, and the differences between hosts varied significantly among sites. The exceptionally high epiphytic diversity associated with D. antarctica suggests that it plays an important ecological role in Tasmanian forests. Evidently C. cunninghamii also supports a diverse suite of epiphytes, including at least one specialist species.     

The bryophyte flora of northern Iturup (north-west Pacific): between the circumboreal and East Asian floristic regions

Introduction. The Kuril Islands Chain demarcates the boundary between the circumpolar and East Asian floras in the amphi-Pacific and is a trans-Oceanic migration route from warm-temperate insular East Asia to north-east Asia and Beringia. This paper reviews the flora of the northern part of Iturup Island in regards to its bryogeography and taxonomic diversity, as well as its relative position among other bryophyte floras of north-east and East Asia.

Methods. The paper uses morphological methods to identify the species composition and detrended correspondence analysis to identify the position of the northern Iturup Island in the system of local floras of the eastern, extra-tropical, Pacific.

Key results. The flora is closely related to the bryophyte floras of the southern Kurils and Hokkaido Island, but has been found to be distinctly distant from the ‘true’ cool-temperate East Asian floras, as well as from the boreal and hemiarctic floras of north-east Asia. Instead, the floras of the south Kurils and northern Hokkaido Island belong to a peculiar intermediate phytogeographic province that cannot be unambiguously placed in either the East Asian or circumboreal floristic regions. The hemiboreal character of the bryophyte flora of northern Iturup Island is in contrast to the general appearance of many of the dominant vegetation communities on the island, which are more characteristic of the hemiarctic.

Conclusion. There is no robust evidence to refer the bryophyte flora of northern Iturup either to the circumboreal or East Asian Floristic Region, the flora belongs to a unique intermediate province between the two regions.     

Niche assembly of epiphytic bryophyte communities in the Guianas: a regional approach

Aim Epiphytic bryophyte communities of tropical forests show a gradient in species composition from the base to the top of the host trees, indicating a strong role of niche assembly. This pattern, however, has never been tested at a regional scale. The aim of this study was to test whether niche assembly, rather than dispersal limitation, predominantly drives species composition of bryophyte communities across large spatial scales. Location Three lowland forests in the Guianas: one near Saul, French Guiana; and two near Mabura Hill, Guyana. Methods Communities of epiphytic bryophytes were sampled from six different height zones of several trees in three lowland forests. We analysed the composition of these communities using detrended correspondence analysis in order to find the best explanatory variable for the variation in community composition. A multi‐response permutation procedure was used to test the significance of grouping communities by height zone. We conducted an indicator species analysis to classify species as specialists or generalists and then tested, through weighted averaging, if specialists would indeed maintain their preferred height zone across the Guianas. Results Community composition was explained mainly by height zone. The similarity among communities inhabiting the same height zone of trees, across a distance of up to 640 km, was higher than the similarity among communities established along the vertical gradient of a single standing tree (30–50 m). More than half (57%) of the species had a preferred height zone, and the preference was consistent: species occupied roughly the same height zone on host trees in the different localities. The three local communities investigated were found to belong to the same regional species pool. Main conclusions Throughout the Guianas, epiphytic bryophyte communities are drawn from the same regional species pool, and their composition is shaped by micro‐environmental conditions. The predominance of niche assembly over dispersal assembly rules is consistently found at both local and regional scales.     

Functional traits reveal the expansion and packing of ecological niche space underlying an elevational diversity gradient in passerine birds

Variation in species richness across environmental gradients may be associated with an expanded volume or increased packing of ecological niche space. However, the relative importance of these alternative scenarios remains unknown, largely because standardized information on functional traits and their ecological relevance is lacking for major diversity gradients. Here, we combine data on morphological and ecological traits for 523 species of passerine birds distributed across an Andes-to-Amazon elevation gradient. We show that morphological traits capture substantial variation in species dietary (75%) and foraging niches (60%) when multiple independent trait dimensions are considered. Having established these relationships, we show that the 14-fold increase in species richness towards the lowlands is associated with both an increased volume and density of functional trait space. However, we find that increases in volume contribute little to changes in richness, with most (78%) lowland species occurring within the range of trait space occupied at high elevations. Taken together, our results suggest that high species richness is mainly associated with a denser occupation of functional trait space, implying an increased specialization or overlap of ecological niches, and supporting the view that niche packing is the dominant trend underlying gradients of increasing biodiversity towards the lowland tropics.     

Disentangling the roles of chance,abiotic factors and biotic interactions among epiphytic bryophyte communities in a tropical rainforest (Yunnan,China)

• Epiphytes offer an appealing framework to disentangle the contributions of chance, biotic and abiotic drivers of species distributions. In the context of the stress-gradient theory, we test the hypotheses that (i) deterministic (i.e., non-random) factors play an increasing role in communities from young to old trees, (ii) negative biotic interactions increase on older trees and towards the tree base, and (iii) positive interactions show the reverse pattern.
• Bryophyte species distributions and abiotic conditions were recorded on a 1.1 ha tropical rainforest canopy crane site. We analysed co-occurrence patterns in a niche modelling framework to disentangle the roles of chance, abiotic factors and putative biotic interactions among species pairs.
• 76% of species pairs resulted from chance. Abiotic factors explained 78% of non-randomly associated species pairs, and co-occurrences prevailed over non-coincidences in the remaining species pairs. Positive and negative interactions mostly involved species pairs from the same versus different communities (mosses versus liverworts) and life forms, respectively. There was an increase in randomly associated pairs from large to small trees. No increase in negative interactions from young to old trees or from the canopy to the base was observed.
• Our results suggest that epiphytic bryophyte community composition is primarily driven by environmental filtering, whose importance increases with niche complexity and diversity. Biotic interactions play a secondary role, with a very marginal contribution of competitive exclusion. Biotic interactions vary among communities (mosses versus liverworts) and life forms, facilitation prevailing among species from the same community and life form, and competition among species from different communities and life forms.

     

秦岭太白山木本植物物种多样性的梯度格局及环境解释

物种多样性沿环境梯度的分布格局是生物多样性研究的重要议题,而海拔梯度包含了各种环境因子的综合影响,因此对于探讨物种多样性沿环境梯度的分布格局具有重要意义。秦岭山脉地处我国暖温带向亚热带的过渡带,其植被垂直带和物种多样性分布格局对于研究我国南北部植被分异特征具有重要意义。基于对秦岭山脉太白山南北坡海拔1200—3750m之间的垂直样带调查的83个样方,本文利用植被数量分析方法(DCA和TWINSPAN)和Shannon-Wiener多样性指数、Pielou指数以及Jaccard相异性系数对太白山木本植物物种多样性在南北坡沿海拔梯度分布格局进行了初步研究。结果表明：太白山的木本植物群落具有明显的环境梯度格局,海拔是决定太白山植物群落分布的主要因素,而坡向起到次要作用一植物群落类型与坡向的关系不大,当考虑群落的环境梯度格局时,DCA第一轴主要与年均温密切相关,而第二轴则取决于年平均相对湿度：乔木层和灌木层的物种具有相似的海拔梯度格局,植物群落中木本植物物种丰富度和多样性随着海拔的升高单调下降;群落均匀度随着海拔变化的规律不明显;灌木层的物种多样性比乔木层更为丰富,而南坡具有比北坡更多的物种数和更高的多样性。相邻海拔之问群落的相异性在南北坡具有不同的分布格局,在北坡2800m以下,群落相异性沿海拔梯度变化不大,而在2800m以上的高海拔地区,群落相异性随海拔的升高而降低;在南坡,随着海拔的升高,群落相异性不断减少。太白山南坡群落比北坡分布更连续。     

Functional diversity of urban bird communities: effects of landscape composition,green space area and vegetation cover

In this study, we aim to gain a better insight on how habitat filtering due to urbanization shapes bird communities of Vienna city parks. This may help to derive implications for urban planning in order to promote and maintain high diversity and ecosystem function in an increasing urbanized environment. The structure of wintering bird communities of 36 Vienna city parks – surveyed once a month in January 2009, December 2009, December 2012, and January 2013 – was described by species richness and the functional diversity measurements FRic (functional richness), FEve (functional evenness), and FDiv (functional divergence). Environmental filtering was quantified by park size, canopy heterogeneity within the park, and the proportion of sealed area surrounding each park. Species richness, FRic, and FDiv increased with increasing park size. Sealed area had a strong negative effect on species richness and FDiv. Canopy heterogeneity played a minor role in explaining variance in FDiv data. FEve did not respond to any of these park parameters. Our results suggest a loss of species richness and functional diversity, hence most likely indicate a decline in ecosystem function, with decreasing park size and increasing sealed area of the surrounding urban landscape matrix.     

Phylogenetic alpha and beta diversity in tropical tree assemblages along regional-scale environmental gradients in northwest South America

Aims Environmental gradients are drivers of species diversity; however, we know relatively little about the evolutionary processes underlying these relationships. A potentially powerful approach to studying diversity gradients is to quantify the phylogenetic structure within and between assemblages arrayed along broad spatial and environmental gradients. Here, we evaluate the phylogenetic structure of plant assemblages along an environmental gradient with the expectation that the habitat specialization of entire lineages is an important evolutionary pattern influencing the structure of tree communities along environmental gradients.Methods We evaluated the effect of several environmental variables on the phylogenetic structure of plant assemblages in 145 plots distributed in northwestern South America that cover a broad environmental gradient. The phylogenetic alpha diversity was quantified for each plot and the phylogenetic beta diversity between each pair of plots was also quantified. Both the alpha and beta diversity measures were then related to spatial and environmental gradients in the study system.Important findings We found that gradients in temperature and potential evapotranspiration have a strong relationship with the phylogenetic alpha diversity in our study system, with phylogenetic overdispersion in low temperatures and phylogenetic clustering at higher temperatures. Further, the phylogenetic beta diversity between two plots increases with an increasing difference in temperature, whereas annual precipitation was not a significant predictor of community phylogenetic turnover. We also found that the phylogenetic structure of the plots in our study system was related to the degree of seasonal flooding and seasonality in precipitation. In particular, more stressful environments such as dry forests and flooded forests showed phylogenetic clustering. Finally, in contrast with previous studies, we find that phylogenetic beta diversity was not strongly related to the spatial distance separating two forest plots, which may be the result of the importance of the three independent mountain ranges in our study system, which generate a high degree of environmental variation over very short distances. In conclusion, we found that environmental gradients are important drivers of both phylogenetic alpha and phylogenetic beta diversities in these forests over spatial distance.     

Resource diversity and provenance underpin spatial patterns in functional diversity across native and exotic species

Functional diversity metrics are increasingly used to augment or replace taxonomic diversity metrics to deliver more mechanistic insights into community structure and function. Metrics used to describe landscape structure and characteristics share many of the same limitations as taxonomy‐based metrics, particularly their reliance on anthropogenically defined typologies with little consideration of structure, management, or function. However, the development of alternative metrics to describe landscape characteristics has been limited. Here, we extend the functional diversity framework to characterize landscapes based on the diversity of resources available across habitats present. We then examine the influence of resource diversity and provenance on the functional diversities of native and exotic avian communities in New Zealand. Invasive species are increasingly prevalent and considered a global threat to ecosystem function, but the characteristics of and interactions between sympatric native and exotic communities remain unresolved. Understanding their comparative responses to environmental change and the mechanisms underpinning them is of growing importance in predicting community dynamics and changing ecosystem function. We use (i) matrices of resource use (species) and resource availability (habitats) and (ii) occurrence data for 62 native and 25 exotic species and 19 native and 13 exotic habitats in 2015 10 × 10 km quadrats to examine the relationship between native and exotic avian and landscape functional diversity. The numbers of species in, and functional diversities of, native and exotic communities were positively related. Each community displayed evidence of environmental filtering, but it was significantly stronger for exotic species. Less environmental filtering occurred in landscapes providing a more diverse combination of resources, with resource provenance also an influential factor. Landscape functional diversity explained a greater proportion of variance in native and exotic community characteristics than the number of habitat types present. Resource diversity and provenance should be explicitly accounted for when characterizing landscape structure and change as they offer additional mechanistic understanding of the links between environmental filtering and community structure. Manipulating resource diversity through the design and implementation of management actions could prove a powerful tool for the delivery of conservation objectives, be they to protect native species, control exotic species, or maintain ecosystem service provision.     

贺兰山不同海拔典型植被带土壤微生物多样性

土壤微生物多样性在海拔梯度的分布格局研究近年来受到和植物动物一样的重视程度,但是干旱风沙区微生物多样性在海拔梯度上的多样性分布规律尚未揭示。本研究以处于干旱风沙区的贺兰山不同海拔的六个典型植被带（荒漠草原带、山地旱生灌丛带、温性针叶林带、针阔混交林带、寒温性针叶林带和亚高山草甸带）土壤为研究对象,利用Biolog微平板法和磷脂脂肪酸甲酯法(FAMEs)系统研究微生物多样性群落特征以及在不同植被带分布规律。结果表明：土壤微生物功能多样性随海拔增加发生变化,且微生物群落结构存在显著差异。Biolog分析显示土壤微生物群落代谢活性依次是：亚高山草甸>寒温性针叶林>针阔混交林>温性针叶林>山地旱生灌丛>荒漠草原,随海拔的升高土壤微生物群落物种丰富度指数（H）和均匀度指数（E）总体上均表现出增大的趋势,差异显著（P＜0.05）;FAMEs分析表明不同海拔的微生物区系发生了一定程度的变化,寒温性针叶林土壤微生物磷酸脂肪酸生物标记的数量和种类均最高,且细菌、真菌特征脂肪酸相对含量也最高;土壤微生物群落结构多样性次序是：寒温性针叶林带>针阔混交林带>温性针叶林带>亚高山草甸>山地旱生灌丛>荒漠草原。本研究结果表明贺兰山海拔梯度的微生物多样性分布规律不同于已有的植物多样性“中部膨胀”研究结果,这说明在高海拔地区有更多的适合该生境的微生物存在,这对维持干旱风沙区的生态系统功能稳定性具有重要意义。     

Reinvestigation on species richness and environmental correlates of bryophytes at a regional scale in China

Aims The aim of this article is 4-fold: (i) to update species richness of bryophytes for each of the Chinese provinces based on the most current knowledge on distributions of bryophytes in China, (ii) to provide a set of analyses based on the updated species richness data and the environmental variables used in a recent article on species richness of bryophytes in China, (iii) to expand the analysis presented in the recent article by relating species richness of bryophytes to over 15 additional climatic variables and (iv) to determine the degree to which the relationships between bryophyte species richness and environmental variables that were reported in the recent article might have been biased.Methods Over 180 literatures with national, provincial and local species lists of bryophytes in China were used in this study. Taxonomy and nomenclature of bryophytes in China were standardized according to The Plant List. Correlation and regression analyses were used to examine the relationships between species richness or species density of bryophytes in Chinese provinces and environmental variables.Important findings On average, each Chinese province possesses 700.6 species of bryophytes, which is 112.1 species more than previously reported. With the updated species richness data reported in this study, stronger relationships between species richness of bryophytes and environmental variables have been found, compared with those found in a recently published study for China. When single environmental variables were considered, precipitation-related variables were, on average, more strongly correlated with species richness and species density than were temperature-related variables. Environmental variables were on average correlated more strongly with species density than with species richness of bryophytes at the regional scale in China. Our study showed that measures quantifying the average and variation of environmental conditions within each Chinese province explained 82.7% and 71.1% of the variation in species richness of liverworts and mosses, respectively, and explained 86.5% and 70.7% of the variation in species density of liverworts and mosses, respectively.     

芦芽山寒温性针叶林冠层下植被beta多样性格局及其成因

群落构建机制是生态学的中心议题之一。对山地植被beta多样性格局及其成因的探究有助于加深对此问题的认识。以芦芽山寒温性针叶林群落冠层下植被为研究对象,结合野外调查与室内实验获取的详细数据,运用Mantel检验、普通最小二乘回归和典范对应分析(CCA)等统计方法,探讨了林下植被的beta多样性格局及其成因,结果显示:(1)沿海拔梯度相邻群落间草本层物种周转率呈现递减格局,而灌木层变化规律不明显;(2)灌、草层beta多样性与海拔差异、地理距离呈显著正相关关系,而与局地环境异质性关系不显著。控制海拔作用后发现,灌、草层beta多样性与地理距离关系依然显著,而当消除地理距离的线性影响后,beta多样性与海拔关系也变得不显著(3)CCA模型中,环境因子共解释了物种组成变异的74.4%,其中,海拔、坡度、凋落物厚度、乔木密度与总干面积对林下灌、草植被物种组成具有显著影响,但土壤因子的作用未见显著。综上,生境筛滤与扩散限制共同主导了芦芽山寒温性针叶林冠层下群落构建过程,但扩散限制的影响强于生境筛滤作用。     

Functional structure and diversity of invertebrate communities in a glacierised catchment of the tropical Andes

1. In many mountainous areas, glaciers feed streams characterised by harsh environmental conditions, such as low water temperature, high turbidity, low channel stability, and high temporal variability in flow. Additionally, in many glacierised catchments, the mixture of streams arising from different water sources (glacier melt, groundwater, rainfall) generates high levels of environmental heterogeneity, which enhance species turnover rates and increase regional diversity.
2. Studies from mainly temperate regions have revealed some consistent patterns: a predominance of traits adaptive to harsh environmental conditions and reduced functional diversity with increased glaciality, both strongly related to environmental filtering. Here, we investigated variation in functional structure and diversity between macroinvertebrate communities from 15 stream sites, with different water sources (five glacier-fed, five groundwater-fed, and five mixed source) and level of glacier influence, in a glacierised catchment in the Ecuadorian Andes.
3. Our results revealed functional differences between communities inhabiting the different stream types. As found in temperate regions, high levels of glaciality were associated with an increase of small-sized taxa that do not swim but are temporarily attached to or burrow in the substrate, have a flying-adult stage, and feed by collecting–gathering. Similarly, we found a general decrease in functional diversity at sites with higher glacier influence. A null modelling approach suggested that in some of our glacier-fed sites, environmental filtering may be the main driver of community assembly, whereas other mechanisms, mainly regional (such as dispersal), but also local (such as intraspecific competition), may gain importance as glacier influence decreases.
4. Assemblage composition in streams in tropical glacierised catchments may be driven by both local and regional processes that generate a gradient of decreasing functional diversity with stronger glacier influence. However, lack of knowledge of relevant traits for taxa in tropical glacierised streams currently poses a substantial obstacle to predicting changes likely to arise from global warming and glacier melt in this region.