Searching for biodiversity indicators in running waters: do bryophytes, macroinvertebrates, and fish show congruent diversity patterns?

The degree to which different taxonomic groups show congruence in diversity patterns has attracted increased attention, yet such studies on stream biota are lacking. We examined environmental correlates of and congruence in the species richness patterns of bryophytes, macroinvertebrates, and fish in 101 boreal streams in Finland. Congruence in species richness among the taxonomic groups was generally low, mainly because of their differing responses to major environmental gradients. Bryophytes and macroinvertebrates showed the strongest degree of congruence, but even this relationship had a relatively weak predictive power. Bryophyte diversity showed the strongest relationship with water colour, followed by habitat stability, and stream size. Macroinvertebrate diversity increased with stream size, and further variation was accounted for by water colour and acidity. Fish species richness showed a weak and complex relationship with geographical location, stream size, and in-stream habitat characteristics. The regression models explained 23, 45, and 26% of the variation in species richness of bryophytes, macroinvertebrates, and fish, respectively. Our results suggest that indicator taxa may be of limited value in stream biodiversity inventories. Habitat-based approaches are suggested as an alternative surrogate measure in the conservation evaluation of lotic biodiversity.     

Taxonomic and functional diversity covary in rock pool microalgal communities despite their different drivers

Local biodiversity has traditionally been estimated with taxonomic diversity metrics such as species richness. Recently, the concept of biodiversity has been extended beyond species identity by ecological traits determining the functional role of a species in a community. This interspecific functional diversity typically responds more strongly to local environmental variation compared with taxonomic diversity, while taxonomic diversity may mirror more strongly dispersal processes compared with functional metrics. Several trait‐based indices have been developed to measure functional diversity for various organisms and habitat types, but studies of their applicability on aquatic microbial communities have been underrepresented. We examined the drivers and covariance of taxonomic and functional diversity among diatom rock pool communities on the Baltic Sea coast. We quantified three taxonomic (species richness, Shannon''s diversity, and Pielou''s evenness) and three functional (functional richness, evenness, and divergence) diversity indices and determined abiotic factors best explaining variation in these indices by generalized linear mixed models. The six diversity indices were highly collinear except functional evenness, which merely correlated significantly with taxonomic evenness. All diversity indices were always explained by water conductivity and temperature–sampling month interaction. Taxonomic diversity was further consistently explained by pool distance to the sea, and functional richness and divergence by pool location. The explained variance in regression models did not markedly differ between taxonomic and functional metrics. Our findings do not clearly support the superiority of neither set of diversity indices in explaining coastal microbial diversity, but rather highlight the general overlap among the indices. However, as individual metrics may be driven by different factors, the greatest advantage in assessing biodiversity is nevertheless probably achieved with a simultaneous application of the taxonomic and functional diversity metrics.     

Dominance determines fish community biomass in a temperate seagrass ecosystem

Biodiversity and ecosystem function are often correlated, but there are multiple hypotheses about the mechanisms underlying this relationship. Ecosystem functions such as primary or secondary production may be maximized by species richness, evenness in species abundances, or the presence or dominance of species with certain traits. Here, we combine surveys of natural fish communities (conducted in July and August 2016) with morphological trait data to examine relationships between biodiversity and ecosystem function (quantified as fish community biomass) across 14 subtidal eelgrass meadows in the Northeast Pacific (54°N, 130°W). We employ both taxonomic and functional trait measures of diversity to investigate whether ecosystem function is best predicted by species diversity (complementarity hypothesis) or by the presence or dominance of species with particular trait values (selection or dominance hypotheses). After controlling for environmental variation, we find that fish community biomass is maximized when taxonomic richness and functional evenness are low, and in communities dominated by species with particular trait values, specifically those associated with benthic habitats and prey capture. While previous work on fish communities has found that species richness is often positively correlated with ecosystem function, our results instead highlight the capacity for regionally prevalent and locally dominant species to drive ecosystem function in moderately diverse communities. We discuss these alternate links between community composition and ecosystem function and consider their divergent implications for ecosystem valuation and conservation prioritization.     

Taxonomic,functional, and phylogenetic dimensions of rodent biodiversity along an extensive tropical elevational gradient

Relationships among taxonomic, functional, and phylogenetic dimensions of biodiversity provide insight about the relative contributions of ecological and evolutionary processes in structuring local assemblages. We used data for rodent species distributions from an extensive tropical elevational gradient to 1) describe elevational gradients for each of three dimensions of biodiversity, 2) evaluate the sufficiency of species richness as a surrogate for other dimensions, and 3) quantify the relative support for mechanisms that increase or decrease phylogenetic or functional dispersion. Taxonomic biodiversity was quantified by species richness, as well as by richness, evenness, diversity, dominance, and rarity at generic and familial levels. Morphological and categorical traits were used to estimate functional biodiversity, and an ultrametric mammalian supertree was used as the basis for estimating phylogenetic biodiversity. Elevational gradients of each dimension of biodiversity were strong, with significant linear and non‐linear components based on orthogonal polynomial regression. Empirical linear and non‐linear regression components were consistently different than those expected based on species richness for generic, familial, and phylogenetic biodiversity, but not for functional biodiversity. Nevertheless, the congruence of dimensions of biodiversity based on correlation analyses indicated that any one dimension is a useful surrogate for the other dimensions for rodents at Manu. Given variation in species richness, assemblages from lowland rainforests comprised more biodiversity than expected, whereas assemblages from cloud and elfin forests represented less biodiversity than expected. Warm temperatures, vertical complexity of the vegetation, and high productivity likely facilitate niche differentiation in rainforests, whereas cricetid rodents are competitively superior to other clades in the less structurally complex, less productive, and colder, high elevation habitats.     

Community isolation drives lower fish biomass and species richness,but higher functional evenness,in a river metacommunity

1. The flow of individuals among communities and their interactions with local environmental filters are increasingly recognised as determinants of biodiversity patterns in riverine ecosystems. Both incoming dispersers and local conditions are expected to systematically change along connectivity gradients from headwaters to downstream communities. However, the interplay between isolation-centrality gradients and environmental conditions as determinants of biodiversity structure and function has seldom been considered.
2. Here, we represented the dendritic structure of the Negro River basin riverscape (Uruguay) in a directed graph quantifying the isolation-centrality of each river section and evaluated the direct and indirect pathways by which riverscape structure and environmental local drivers determine fish community assembly.
3. Fish communities (n = 58) were sampled following a stratified sampling design that properly represents this isolation-centrality connectivity gradient through the riverscape. In each community, fish abundance, biomass, richness, and functional diversity were estimated, and the direct and indirect hypothesised connections among them were evaluated with structural equation models.
4. We showed that the range of isolation among river sections determines a 2-fold, 5-fold, and 25-fold variation in total fish richness, abundance, and biomass, respectively. Additionally, isolation-centrality was positively associated with local temperature and conductivity, while negatively related to local depth. These variables and taxonomic richness accounted for most of the variation in total fish biomass (81%) herein used as measurement of ecosystem function. Local fish abundance was negatively and positively associated with functional evenness and taxonomic richness, respectively. Furthermore, once the effect of isolation on biomass and richness was accounted for, an effect of diversity on biomass became evident.
5. Our results provide empirical evidence for the role of riverscape structure on taxonomic and functional diversity, biomass, and the relationship between biodiversity and ecosystem function. We emphasise that in the understanding of river biodiversity and its management, local determinants should not be considered without attention to metacommunity processes.

     

Multiple facets of stream macroinvertebrate alpha diversity are driven by different ecological factors across an extensive altitudinal gradient

Environmental filtering and spatial structuring are important ecological processes for the generation and maintenance of biodiversity. However, the relative importance of these ecological drivers for multiple facets of diversity is still poorly understood in highland streams. Here, we examined the responses of three facets of stream macroinvertebrate alpha diversity to local environmental, landscape‐climate and spatial factors in a near‐pristine highland riverine ecosystem. Taxonomic (species richness, Shannon diversity, and evenness), functional (functional richness, evenness, divergence, and Rao's Quadratic entropy), and a proxy of phylogenetic alpha diversity (taxonomic distinctness and variation in taxonomic distinctness) were calculated for macroinvertebrate assemblages in 55 stream sites. Then Pearson correlation coefficient was used to explore congruence of indices within and across the three diversity facets. Finally, multiple linear regression models and variation partitioning were employed to identify the relative importance of different ecological drivers of biodiversity. We found most correlations between the diversity indices within the same facet, and between functional richness and species richness were relatively strong. The two phylogenetic diversity indices were quite independent from taxonomic diversity but correlated with functional diversity indices to some extent. Taxonomic and functional diversity were more strongly determined by environmental variables, while phylogenetic diversity was better explained by spatial factors. In terms of environmental variables, habitat‐scale variables describing habitat complexity and water physical features played the primary role in determining the diversity patterns of all three facets, whereas landscape factors appeared less influential. Our findings indicated that both environmental and spatial factors are important ecological drivers for biodiversity patterns of macroinvertebrates in Tibetan streams, although their relative importance was contingent on different facets of diversity. Such findings verified the complementary roles of taxonomic, functional and phylogenetic diversity, and highlighted the importance of comprehensively considering multiple ecological drivers for different facets of diversity in biodiversity assessment.     

江湖阻隔对长江中下游湖泊鱼类群落分类多样性的影响

基于1950s以来的长江中下游湖泊鱼类调查数据,分析通江湖泊与阻隔湖泊的鱼类分类多样性差异,以及通江和阻隔湖泊鱼类分类多样性的时间序列变化,探讨江湖阻隔对鱼类多样性的影响。结果显示,阻隔湖泊鱼类物种数、平均分类差异指数(Δ⁺)和分类差异变异指数(Λ⁺)平均值分别为48.47±14.64、74.02±3.09和736.89±33.80;通江湖泊为76.22±14.40、78.31±0.98和697.31±25.53。阻隔湖泊物种数和Δ⁺值显著低于通江湖泊(P<0.001),而阻隔湖泊Λ⁺值显著高于通江湖泊(P=0.002),表明阻隔湖泊物种间亲缘关系更近,均匀度下降,即物种分类单元减少,且集中分布于某几个分类阶元,稳定性变差。典型通江与阻隔湖泊鱼类群落分类多样性的时间变化分析发现,两种类型湖泊的鱼类物种数和Δ⁺值均随时间推移整体呈现下降趋势,Λ⁺值整体呈现升高趋势;并且阻隔湖泊的Λ+值随阻隔时间增加而大幅上升,Δ⁺和Λ^+...     

Comparative analysis of algal biodiversity in the rivers of Israel

Comparative analysis of algal communities in the rivers of Israel was completed to highlight the influence of environmental variables on biodiversity. The study revealed that 671 species of algae and cyanobacteria belonging to nine taxonomic divisions were present during 2002–2009 in the Yarqon, Alexander, Hadera, Qishon, Oren, Lower and Upper Jordan, and Zin rivers. The species richness of each river was evaluated by taxonomic structural comparison, geobotanical, hierarchical cluster analysis, and the degree of relatedness for different levels of taxonomic resolution. The analysis revealed close similarity of the Upper Jordan and Oren rivers. The average taxonomic distinctness index showed that the Yarqon, Oren, Upper Jordan, and Qishon communities were partly degraded due to permanent environmental disturbances. The variation in taxonomic distinctness index showed that the Alexander, Yarqon and Hadera communities were formed not only due to anthropogenic factors but also through long-term climatic impact. The most abundant indicator species inhabit low streaming and standing alkaline waters of medium salinity and low to medium organic pollution. The statistical approaches allowed discrimination between climatic and anthropogenic factors that impact upon the riverine biodiversity in semi-arid environments. Analysis shows the influence of anthropogenic factors was strongly modulated by climatic impacts causing a marked decease of species richness from north to south.     

人为干扰对溪流鱼类功能多样性及其纵向梯度格局的影响

溪流鱼类多样性沿着河流纵向梯度的空间分布规律已得到大量报道, 但这些研究大多聚焦基于物种组成的分类α多样性, 而有关分类β多样性和功能多样性的纵向梯度分布规律及其对人类干扰的响应研究较少。本文以青弋江上游3条人为干扰程度不同的河源溪流为研究区域, 比较研究了人为干扰对溪流鱼类功能α和β多样性及其纵向梯度分布格局的影响。结果显示, 人类干扰改变了河源溪流鱼类功能多样性的纵向梯度格局——由线性变化变为二项式分布。此外, 我们发现, 人为干扰导致土著种被本地入侵种取代, 且较强的土地利用和水污染排放可能增大环境的不连续性, 而群落周转和嵌套变化往往取决于环境的变化。尽管功能β多样性由嵌套成分主导, 但周转成分占比相对于人为干扰较小的溪流而言明显增加。人为干扰显著改变了受干扰溪流鱼类的物种组成和功能多样性, 且功能多样性的纵向梯度格局在不同的多样性指标上存在差异。本研究强调, 在评估人为干扰下多样性的变化时, 需要从多方面考虑, 包括空间尺度和多样性指标等。     

Predicting community rank‐abundance distributions under current and future climates

Understanding influences of environmental change on biodiversity requires consideration of more than just species richness. Here we present a novel framework for understanding possible changes in species' abundance structures within communities under climate change. We demonstrate this using comprehensive survey and environmental data from 1748 woody plant communities across southeast Queensland, Australia, to model rank‐abundance distributions (RADs) under current and future climates. Under current conditions, the models predicted RADs consistent with the region's dominant vegetation types. We demonstrate that under a business as usual climate scenario, total abundance and richness may decline in subtropical rainforest and shrubby heath, and increase in dry sclerophyll forests. Despite these opposing trends, we predicted evenness in the distribution of abundances between species to increase in all vegetation types. By assessing the information rich, multidimensional RAD, we show that climate‐driven changes to community abundance structures will likely vary depending on the current composition and environmental context.     

Biodiversity in microbial communities: system scale patterns and mechanisms

The relationship between anthropogenic impact and the maintenance of biodiversity is a fundamental question in ecology. The emphasis on the organizational level of biodiversity responsible for ecosystem processes is shifting from a species-centred focus to include genotypic diversity. The relationship between biodiversity measures at these two scales remains largely unknown. By stratifying anthropogenic effects between scales of biodiversity of bacterial communities, we show a statistically significant difference in diversity based on taxonomic scale. Communities with intermediate species richness show high genotypic diversity while speciose and species-poor communities do not. We propose that in species-poor communities, generally comprising stable yet harsh conditions, physiological tolerance and competitive trade-offs limit both the number of species that occur and the loss of genotypes due to decreases in already constrained fitness. In species-rich communities, natural environmental conditions result in well-defined community structure and resource partitioning. Disturbance of these communities disrupts niche space, resulting in lower genotypic diversity despite the maintenance of species diversity. Our work provides a model to inform future research about relationships between species and genotypic biodiversity based on determining the biodiversity consequences of changing environmental context.     

Taxonomic diversity as complementary information to assess plant species diversity in secondary vegetation and primary tropical deciduous forest

Question: Species diversity is commonly expressed as the number of species present in an area, but this unique value assumes that all species contribute equally to the area's biodiversity. Can taxonomic diversity be used as a complementary measure for species richness in order to assess plant biodiversity in remnants of primary forest and patches of secondary vegetation? Location: Veracruz, Mexico. Methods: Using data from six sampling transects of each vegetation type in an elevation gradient (400‐900 m a.s.l.), we compare the point, mean and cumulative floristic diversity of primary forest and secondary vegetation in a tropical deciduous landscape, using species richness and two measures of taxonomic diversity: average taxonomic distinctness (Δ+) and variation in taxonomic distinctness (Λ+). We performed a randomization test to detect differences in the observed taxonomic diversity, from the expected values derived from the species pool of each vegetation type. Results: We found that the species of secondary vegetation are more closely related at low taxonomic levels (lower Δ+ value) than the species of primary forest remnants. Also, in secondary vegetation the distribution of species is uneven among the taxonomic levels and units (high Λ+ value). These patterns are consistent for point, mean and cumulative taxonomic diversity. Families Asteraceae, Euphorbiaceae, Fabaceae and Poaceae are over‐represented, while families Bromeliaceae, Cactaceae, Orchidaceae and Pteridaceae are under‐represented in secondary vegetation. Conclusions: Although in a previous paper we concluded that secondary vegetation is more alpha‐diverse than primary forest (in terms of both cumulative and mean species richness), and beta‐diversity between vegetation types is notoriously high, we now provide a wider view by highlighting the importance of taxonomic diversity in primary forest remnants. Our data indicate that to measure biodiversity accurately, we should seek to capture its different facets. This will allow us to make conservation recommendations based on a broader view, and not on a single dimension.     

Atlantic floodplain meadows: influence of hydrological gradients and management on sciomyzid (Diptera) assemblages

Maintaining biodiversity is central to maintaining ecosystem functionality of wetlands. Hydrology has the strongest influence on wetland biodiversity, second to which agriculture is the most influential factor. This study investigates the influence of hydrology and farming practices on the abundance, species richness and composition of dipteran communities on temperate Atlantic floodplain hay meadows. Insects were sampled by sweep-net across twenty-four vegetation zones for which hydrological variables were calculated by combining river level data with fine-scale topographical data. Plant communities were surveyed using relevés and land owners were interviewed to gather data on current and past management regimes. A total of twenty-two sciomyzid species were recorded; over one-third of the Irish fauna. Flood depth and duration were found to have the strongest influence on sciomyzids, syrphids and plants. Sciomyzid species richness and total abundance were both positively correlated with hydroperiod and flood depth while both plants and syrphids responded negatively to increases. The difference in response highlights the need to assess more than one taxonomic group, when assessing the impact of changing environmental variables on biodiversity. Whereas vegetation structure drives changes in sciomyzid indicator species, plant species richness and composition, past management regimes and current nutrient inputs do not appear to influence these species. Thus, while the maintenance of the hydrological heterogeneity and the diversity of mowing regimes is important in maintaining biodiversity, variation in nutrient inputs and previous management (at least within the range here investigated) is likely to be of lesser importance for Syrphidae and Sciomyzidae.     

Functional diversity (FD), species richness and community composition

Functional diversity is an important component of biodiversity, yet in comparison to taxonomic diversity, methods of quantifying functional diversity are less well developed. Here, we propose a means for quantifying functional diversity that may be particularly useful for determining how functional diversity is related to ecosystem functioning. This measure of functional diversity “FD” is defined as the total branch length of a functional dendrogram. Various characteristics of FD make it preferable to other measures of functional diversity, such as the number of functional groups in a community. Simulating species' trait values illustrates how the relative importance of richness and composition for FD depends on the effective dimensionality of the trait space in which species separate. Fewer dimensions increase the importance of community composition and functional redundancy. More dimensions increase the importance of species richness and decreases functional redundancy. Clumping of species in trait space increases the relative importance of community composition. Five natural communities show remarkably similar relationships between FD and species richness.     

Geometric morphology as an alternative for measuring the diversity of fish assemblages

Biological diversity can be measured using ecological, taxonomic and functional indices, although numerous studies have concluded that organism morphology can be also a source for computing diversity indices. In the present study, we characterized fish morphology using geometric morphology, which included body shape landmarks as well as the morphology of fins, and we computed the correlation among ecological, taxonomic, functional and morphological indices (including a new index defined here called “morphological richness”). Morphological indices were calculated both from abundance data and presence/absence data. To carry out this study, thirteen fish assemblages of two different areas of the Catalan coast (north-western Mediterranean) were analyzed. The data was sampled by commercial fishing vessels using trammel nets. The results clearly indicated that each type of morphological index is related to one dimension of the biodiversity space. Furthermore, we demonstrated that presence/absence data provided the similar results as abundance data when using morphological indices, opening the possibility to analyze the evolution of fish assemblages over time from species checklists collected in experimental surveys from the late XIX century to the present.     

Taxonomic and functional homogenisation of macroinvertebrate communities in recently intermittent Alpine watercourses

1. Mountain streams in southwestern European Alps are currently shifting from perennial to intermittent flow due to the combined effects of climate change and local anthropogenic pressures. Given that flow intermittency is a recently documented phenomenon in the Alps, only scattered studies have investigated functional and taxonomical diversity of benthic invertebrate communities in recently intermittent Alpine streams.
2. We used a hierarchical sampling design to investigate patterns in taxonomic and functional diversity of benthic invertebrate communities in 13 recently intermittent Alpine streams in north-west Italy. in April 2017, we sampled benthic communities in two reaches of each stream with different hydrological conditions: a control reach, with permanent flow; and an intermittent reach, which recently experienced non-flow periods in summer.
3. We tested for the response of taxonomic richness at multiple spatial scales by partitioning total diversity into the average richness of local communities and the richness due to variation among local communities both within and among reaches. By partitioning total diversity (γ) into its local (α) and turnover (β) components we showed a decrease in local and regional species richness both within and among reaches, whereas variation among communities was significantly lower in intermittent reaches at the reach scale only.
4. The analysis of multidimensional trait space of macroinvertebrate communities in reaches with different hydrological conditions revealed a significant reduction of functional diversity, dispersion, and evenness in intermittent reaches. There was trait overdispersion in intermittent reaches, as these hosted both typical Alpine taxa and organisms adapted to flow intermittency. In particular, we observed the replacement of taxa with aquatic respiration and those preferring medium- to fast-flowing oligotrophic waters by taxa adapted to lentic habitats, air breathing and with larval dormancy phases.
5. These results indicate that recent flow intermittency has caused drastic changes in benthic invertebrate communities in Alpine streams. Our work highlights the importance of integrating taxonomic and functional diversity to thoroughly assess the impacts of flow intermittency.

     

Revisiting the dimensionality of biological diversity

Biodiversity can be represented by different dimensions. While many diversity metrics try to capture the variation of these dimensions they also lead to a ‘fragmentation’ of the concept of biodiversity itself. Developing a unified measure that integrates all the dimensions of biodiversity is a theoretical solution for this problem, however, it remains operationally impossible. Alternatively, understanding which dimensions better represent the biodiversity of a set of communities can be a reliable way to integrate the different diversity metrics. Therefore, to achieve a holistic understand of biological diversity, we explore the concept of dimensionality. We define dimensionality of diversity as the number of complementary components of biodiversity, represented by diversity metrics, needed to describe biodiversity in an unambiguously and effective way. We provide a solution that joins two components of dimensionality – correlation and the variation – operationalized through two metrics, respectively: evenness of eigenvalues (EE) and importance values (IV). Through simulation we show that considering EE and IV together can provide information that is neglected when only EE is considered. We demonstrate how to apply this framework by investigating the dimensionality of South American small mammal communities. Our example evidenced that, for some representations of biological diversity, more attention is needed in the choice of diversity metrics necessary to effectively characterize biodiversity. We conclude by highlighting that this integrated framework provides a better understanding of dimensionality than considering only the correlation component.     

Increasing fish taxonomic and functional richness affects ecosystem properties of small headwater prairie streams

相似文献   

Latitudinal gradient in the taxonomic composition of parasite communities

Although latitudinal gradients in diversity have been well studied, latitudinal variation in the taxonomic composition of communities has received less attention. Here, we use a large dataset including 950 surveys of helminth endoparasite communities in 650 species of vertebrate hosts to test for latitudinal changes in the relative contributions of trematodes, cestodes, nematodes and acanthocephalans to parasite assemblages. Although the species richness of helminth communities showed no consistent latitudinal variation, their taxonomic composition varied as a function of both host type and latitude. First, trematodes and acanthocephalans accounted for a higher proportion of species in helminth communities of fish, whereas nematodes achieved a higher proportion of the species in communities of bird and especially mammal hosts. Second, the proportion of trematodes in helminth communities of birds and mammals increased toward higher latitudes. Finally, the proportion of nematodes per community increased toward lower latitudes regardless of the type of host. We present tentative explanations for these patterns, and argue that new insights in parasite community ecology can be gained by searching for latitudinal gradients not only in parasite species richness, but also in the taxonomic composition of parasite assemblages.