Accounting for multiple dimensions of biodiversity to assess surrogate performance in a freshwater conservation prioritization

Understanding diversity patterns and the potential mechanisms driving them is a fundamental goal in ecology. Examination of different dimensions of biodiversity can provide insights into the relative importance of different processes acting upon biotas to shape communities. Unfortunately, patterns of diversity are still poorly understood in hyper-diverse tropical countries. Here, we assess spatial variation of taxonomic, functional and phylogenetic diversity of bat assemblages in one of the least studied Neotropical countries, Bolivia, and determine whether changes in biodiversity are explained by the replacement of species or functional groups, or by differences in richness (i.e., gain or loss of species or functional groups). Further, we evaluate the contribution of phylogenetic and taxonomic changes in the resulting patterns of functional diversity of bats. Using well-sampled assemblages from published studies we examine noctilionoid bats at ten study sites across five ecoregions in Bolivia. Bat assemblages differed from each other in all dimensions of biodiversity considered; however, diversity patterns for each dimension were likely structured by different mechanisms. Within ecoregions, differences were largely explained by species richness, suggesting that the gain or loss of species or functional groups (as opposed to replacement) was driving dissimilarity patterns. Overall, our results suggest that whereas evolutionary processes (i.e., historical connection and dispersal routes across Bolivia) create a template of diversity patterns across the country, ecological mechanisms modify these templates, decoupling the observed patterns of functional, taxonomic and phylogenetic diversity in Bolivian bats. Our results suggests that elevation represents an important source of variability among diversity patterns for each dimension of diversity considered. Further, we found that neither phylogenetic nor taxonomic diversity can fully account for patterns of functional diversity, highlighting the need for examining different dimensions of biodiversity of bats in hyperdiverse ecosystems.

Spatial patterns of functional diversity are important in understanding community assembly as well as spatial variation in ecosystem functioning, yet the contribution of different species to these patterns remains unclear, making it difficult to generalise. Several studies have previously used a sequential addition approach to determine the subsets of species that contribute to the spatial distribution of species richness, frequently showing the importance of common species to richness patterns. This approach, however, has not been applied to functional diversity despite the central role of species traits in community ecology. Here we use a multiscale survey of plants from the Machair grassland system of the Western Isles of Scotland to ask the following questions: (i) Do functional diversity patterns correlate better with geographically common or geographically rare species?; (ii) Do their relative contributions vary with spatial scale?; and (iii) Do these patterns vary between functional diversity measures? We show that while species richness patterns correlate with geographically common species, common species contribute less than expected to spatial patterns of functional diversity at frequently used spatial monitoring scales. The relative contribution of species to overall biodiversity patterns, however, can vary with spatial scale. Synthesis. Surveying only common species may be inadequate for estimating spatial patterns of functional diversity, especially if using occurrence as opposed to percentage cover or abundance data, and spatial scale needs to be considered when designing surveys. Our approach highlights the species that may be adequate indicators of different dimensions of biodiversity and contributes to our understanding of the distribution of functional diversity in space.

Riparian plant communities are key to ecosystem functioning and important providers of ecosystem services on which wildlife and people depend. Ecosystem functioning and stability depend on functional diversity and redundancy. Therefore, understanding which and how different drivers shape community assembly processes and functional patterns is crucial. However, there is limited knowledge of these processes at larger scales for the entire riparian vascular plant community. Two community assembly processes dominate: environmental filtering, where species living in similar environments have similar traits leading to trait convergence; and limiting similarity, where similar traits cause species to compete more strongly leading to trait divergence. We assessed functional diversity patterns of riparian vascular plant communities across an Atlantic–Mediterranean biogeographical gradient in north Portugal. We used functional diversity indices and null models to detect community assembly processes and whether these processes change along environmental gradients. We hypothesised that environmental filtering associated with precipitation and aridity would be the prevailing assembly process at a regional scale. We also expected a shift from environmental filtering to limiting similarity as precipitation‐related stress declined. As hypothesised, patterns of functional diversity were consistent with environmental filtering of species occurrences at the regional scale. Functional patterns were also consistent with a shift between environmental filtering and limiting similarity as cold and aridity stress declined. Under stressful environmental conditions, communities showed lower functional divergence and richness than expected by chance. Environmental filtering was more strongly associated with minimum temperatures than precipitation and aridity. Underlining the need for hierarchical approaches and the analysis of multiple climatic stressors, our results highlighted the relevance of large‐scale environmental stress gradients and the potential role of community assembly in influencing riparian functional diversity. Alterations in stress filters due to climate change will affect assembly processes and functional patterns, probably affecting ecosystem functioning and stability.

AimFunctional redundancy occurs when species share overlapping ecological functions and is considered an important component of ecosystem resilience. However, much of what we know about functional redundancy comes from relatively species‐rich terrestrial and marine environments. Here, we examined patterns of functional redundancy among Ontario freshwater fish communities with species richness levels ranging from 4 to 30 species across lakes of differing size, depth, productivities and thermal characteristics.LocationSix thousand nine hundred and seventy‐seven lakes in Ontario, Canada.MethodsWe examined functional redundancy by quantifying the relationship between functional diversity and species richness in lakes across Ontario and within smaller biogeographic regions. We used null models to test whether fish communities had greater redundancy than expected from random assemblages. We then used generalized additive models (GAMs) to predict how patterns of redundancy vary across environmental variables. At last, we compared species‐level functional rarity metrics across fish thermal preference groups, body sizes and species occurrence rates.ResultsThe functional diversity and species richness relationship were saturating among fish communities at the provincial scale but varied between smaller regions with differing biogeographic histories. Most communities fell within expectations from weighted null models of the functional diversity and species richness relationship. The GAMs indicated that fish communities in the largest, deepest and warmest lakes showed the greatest overall functional redundancy. No differences were observed in functional rarity measures between thermal preference groups, across body sizes or across species occurrence rates.Main conclusionsAlthough lakes in this study were relatively depauperate of fish species, Ontario fish communities exhibited functional redundancy at the provincial scale, with variation regionally. North‐eastern communities showed the least saturating relationship overall as predicted by historical biogeographic patterns of freshwater fish colonization. Overall, this study provides a broad perspective of freshwater fish diversity patterns and highlights the importance of investigating redundancy from different perspectives and multiple spatial scales.

Global biodiversity losses erode the functioning of our vital ecosystems. Functional diversity is increasingly recognized as a critical link between biodiversity and ecosystem functioning. Satellite earth observation was proposed to address the current absence of information on large-scale continuous patterns of plant functional diversity. This study demonstrates the inference and spatial mapping of functional diversity metrics through satellite remote sensing over a large key biodiversity region (Sabah, Malaysian Borneo, ~53,000 km2) and compares the derived estimates across a land-use gradient as an initial qualitative assessment to test the potential merits of the approach. Functional traits (leaf water content, chlorophyll-a and -b, and leaf area index) were estimated from Sentinel-2 spectral reflectance using a pre-trained neural network on radiative transfer modeling simulations. Multivariate functional diversity metrics were calculated, including functional richness, divergence, and evenness. Spatial patterns of functional diversity were related to land-use data distinguishing intact forest, logged forest, and oil palm plantations. Spatial patterns of satellite remotely sensed functional diversity are significantly related to differences in land use. Intact forests, as well as logged forests, featured consistently higher functional diversity compared to oil palm plantations. Differences were profound for functional divergence, whereas functional richness exhibited relatively large variances within land-use classes. By linking large-scale patterns of functional diversity as derived from satellite remote sensing to land-use information, this study indicated initial responsiveness to broad human disturbance gradients over large geographical and spatially contiguous extents. Despite uncertainties about the accuracy of the spatial patterns, this study provides a coherent early application of satellite-derived functional diversity toward further validation of its responsiveness across ecological gradients.

The multi-dimensional analysis of biodiversity addresses several components, including the number of species, as well as their ecological and evolutionary identities. This approach can lead to key biodiversity patterns that remain covered when only species richness is studied. The convergence of the Nearctic and Neotropical biogeographic regions in Mexico suggests spatial variation in biodiversity patterns. In this study we analysed species richness, functional diversity, and phylogenetic diversity of mammal assemblages in relation to abiotic variables and their variation across the biogeographic regions. Our results showed contrasting patterns among biodiversity dimensions: 1) species richness followed the typical global pattern of a gradual increase from the Nearctic towards the Neotropical region, 2) phylogenetic diversity was highest in the Transitional region; and 3) functional diversity was highest in the Neotropical region, but not different between the Nearctic and Transitional regions. Abiotic variables had a significant relation with variation in biodiversity dimensions, but they had a higher contribution to explain functional diversity than species richness and phylogenetic diversity. The decoupled patterns of functional and phylogenetic diversity among the biogeographical regions highlight the complementarity between these dimensions and the importance of transitional regions, and suggest that several historical, environmental and ecological processes may be structuring mammal assemblages. Likewise, different approaches should be followed in accordance to variation of functional and phylogenetic traits among regions.

BackgroundFunctional diversity illustrates the range of ecological functions in a community. It allows revealing the appearance of functional redundancy in communities and processes of community assembly. Functional redundancy illustrates the overlap in ecological functions of community members which may be an indicator of community resilience. We evaluated patterns of species richness, functional diversity and functional redundancy on tadpole communities in rainforest streams in Madagascar. This habitat harbours the world's most species-rich stream tadpole communities which are due to their occurrence in primary habitat of particular interest for functional diversity studies.ResultsSpecies richness of tadpole communities is largely determined by characteristics of the larval habitat (stream structure), not by adult habitat (forest structure). Species richness is positively correlated with a size-velocity gradient of the streams, i.e. communities follow a classical species-area relationship. While widely observed for other taxa, this is an unusual pattern for anuran larvae which usually is expected to be hump-shaped. Along the species richness gradient, we quantified functional diversity of all communities considering the similarity and dissimilarity of species in 18 traits related to habitat use and foraging. Especially species-rich communities were characterised by an overlap of species function, i.e. by functional redundancy. By comparing the functional diversity of the observed communities with functional diversity of random assemblages, we found no differences at low species richness level, whereas observed species-rich communities have lower functional diversity than respective random assemblages.ConclusionsWe found functional redundancy being a feature of communities also in primary habitat, what has not been shown before using such a continuous measure. The observed species richness dependent pattern of low functional diversity indicates that communities with low species richness accumulate functional traits randomly, whereas species in species-rich communities are more similar to each other than predicted by random assemblages and therefore exhibit an accumulation of stream-specific functional traits. Beyond a certain species richness level, therefore, stream-specific environmental filters exert influence whereas interspecific competition between species does not influence trait assemblage at any species richness level.

AimAs we enter an era of major biodiversity shifts, understanding large‐scale biodiversity patterns has become crucial for ecological and conservation purposes. Often, conservation priorities are based on concepts derived largely from species richness, yet recent work shows that different facets of biodiversity are also crucial for proper ecosystem continuity, function and services. One facet of biodiversity increasingly relevant to conservation is functional diversity. Here, we aim to improve our understanding of large‐scale patterns of biodiversity by testing the hypothesis that species richness can also accurately estimate functional diversity along the latitudinal gradient of species richness in fish.LocationMarine environments.Time periodContemporary.Major taxa studiedEight hundred and forty‐two species within 11 fish families: Acanthuridae, Blenniidae, Chaetodontidae, Gobiidae, Labridae, Lutjanidae, Pleuronectidae, Pomacanthidae, Pomacentridae, Scombridae and Sparidae.MethodsUsing geometric morphometrics to calculate morphological diversity, a proxy for functional diversity, we estimated the expected functional diversity for a given number of species and compared it with the observed functional diversity in fish families along latitudes. We then fitted a broken‐stick regression model with estimates of functional diversity over absolute degree of latitudes to locate latitudes where significant shifts in functional diversity occur.ResultsWe found that species richness typically over‐ or underestimated functional diversity along the latitudinal gradient of species richness in the evaluated fishes. We also showed that for most families investigated, there was a pattern of stable functional diversity from the equator through the tropics that shifted, with a mean inflection point occurring at absolute latitude 31.7 ± 10.1°. We suggest that this pattern might be linked to changes in environmental factors such as global temperature and/or habitat availability beyond tropical latitudes; however, these concepts require more study.Main conclusionsThis analysis shows the importance of considering functional diversity further, in combination with other biodiversity metrics, when developing conservation priorities and policies.

Over the last two decades, although much has been learned regarding the multifaceted nature of biodiversity, relatively little is known regarding spatial variation in constituents other than species richness. This is particularly true along extensive environmental gradients such as latitude. Herein, we describe latitudinal gradients in the functional diversity of New World bat communities. Bat species from each of 32 communities were assigned to one of seven functional groups. Latitudinal gradients existed for the richness, diversity and scaled‐dominance of functional groups. No significant patterns were observed for evenness of functional groups. Measures of functional diversity were different in magnitude and increased towards the equator at a faster rate than expected given the underlying spatial variation in species richness. Thus, latitudinal gradient in species richness alone do not cause the latitudinal gradient in functional diversity. When variation in species composition of the regional fauna of each community was incorporated into analyses, many differences between observed and simulated patterns of functional diversity were not significant. This suggests that those processes that determine the composition of regional faunas strongly influence the latitudinal gradient in functional diversity at the local level. Nonetheless, functional diversity was lower than expected across observed sites. Community‐wide responses to variation in the quantity and quality of resources at the local level probably contribute to differences in functional diversity at local and regional scales and enhance beta diversity.

In forested ecosystems, it remains unclear whether environmental conditions, resource competition or their joint effects explain non-randomly distributed species pattern. Recently, trait-based approaches have been recognized as an important tool to infer processes governing community assembly patterns. In this study, we quantify patterns of functional composition and diversity to study how tree species coexistence is influenced by abiotic factors and biotic interactions in a species-rich temperate old-growth forest. In a 25 ha (500 × 500 m) fully mapped forest plot, we calculated functional composition (community weighted mean) and diversity of five key traits considering two spatial scales (20 × 20 and 50 × 50 m quadrats). We compared the observed patterns in functional diversity with randomly generated null communities to test for the presence of non-random patterns in community assembly, and studied the variation of functional composition and diversity along gradients of soil conditions to test for the shift in assembly processes along resource gradients. Functional diversity differed from null expectations depending on the spatial scale considered. In broad-scale quadrats (50 × 50 m), functional diversity in wood specific gravity (WSG) and leaf area (LA) was lower than expected by chance, whereas functional diversity in specific root length (SRL) was greater than expected. In small quadrats (20 × 20 m), functional diversity was lower than expected by chance in specific leaf area (SLA) and when considering all traits in combination. Functional composition and diversity varied along the soil resource gradient but the results were dependent on the scale considered. We found an increase in functional composition in maximum height (H) and WSG and a reduction in the functional diversity in most of traits suggesting an increase in competition with the increase in soil water content at small scale. The trait dispersion pattern for all traits in combination had no directional changes with some of individual traits generating more clear dispersion trend when the dominant competitor Pinus koraiensis was removed from the community dataset. The results presented here suggest that community assembly is governed by non-random processes in the studied forests. Interestingly, the choice of quadrat size seems to be crucial to describe community patterns and infer the forces governing community assembly. The consideration of different traits and environmental gradients allowed us to discover that different assembly mechanisms operate simultaneously in the studied forest.

Arthropod diversity is often linked to variation in resource use, dispersal ability, habitat connectivity, and climate factors that differ across spatial scales. The aim of this research was to examine how species richness, functional diversity, and community composition of two taxa differing in functional roles and dispersal ability are structured across spatial scales and to identify the importance of vegetation, climate, and landscape in explaining these patterns at different scales. Organisms were collected from tree canopies using insecticidal fogging in the summer of 2000 from 96 trees in 24 stands of 6 deciduous forest sites in 2 ecoregions of the eastern United States. Taxonomic and functional beta diversity of ants (Hymenoptera: Formicidae) and spiders (Araneae) were partitioned across four hierarchical spatial scales (individual tree, forest stand, site, and ecoregion). The contributions of climatic, landscape, and vegetation variables were determined using model selection. Ant and spider species richness, functional diversity, and community composition differed between taxa and across spatial scales. Alpha diversity (within trees) was lower than expected for both taxa and types of diversity, with host tree species supporting different species of ants and spiders. While the beta components of species diversity among trees and forest stands were greater than expected for both taxa, spiders also showed significant levels of beta diversity among sites. Functional beta diversity was less scale‐dependent than taxonomic beta diversity. Stand‐level patterns of beta diversity were significantly predicted by variation in climate and landscape connectivity. The effects of climate and landscape fragmentation on the diversity and community structure of both taxa indicate that anthropogenic climate change and land use change will alter canopy arthropod communities. Results also suggest that patterns of diversity among fragmentation metrics are influenced by differences in dispersal ability.

QuestionsAlthough the relative importance of climate in abiotic filtering is higher for woody than for herbaceous species assemblages, it is unclear whether this pattern is also reflected between the woody overstorey and herbaceous understorey of forests. The understorey might respond more to small‐scale soil variation, next to experiencing additional abiotic filtering through overstorey effects on light and litter quality. We explored the proportional importance of climate and soil on the species, trait and (functional) diversity patterns of both the forest overstorey and fern and lycophyte understorey.LocationSubtropical forest along an elevational gradient from 850 to 2100 m a.s.l. in northern Taiwan.MethodsWe measured nine functional traits expected to respond to soil nutrient or climatic stress for woody overstorey species and understorey ferns and lycophytes. Next, we performed parallel constrained ordinations on over‐ and understorey species and trait composition, and multiple regression for species and functional diversity, using measured climate proxies and soil variables as predictors.ResultsClimate was more important than soil in predicting the species composition of both vegetation layers and trait composition of the understorey. The stronger than expected effect of climate for the understorey was likely due to fern and lycophytes’ higher vulnerability to drought, while the higher importance of soil for the overstorey trait composition seemed driven by deciduous species. The environmental drivers affected different response traits in both vegetation layers, and the overstorey had additional effects on understorey traits, resuling in a disconnection of community‐level trait values across layers. Interestingly, species and functional diversity patterns could be almost exclusively explained by climate effects for both layers.ConclusionsThis study illustrates that abiotic filtering can differentially affect species, trait and diversity patterns and can be highly divergent for forest overstorey and fern understorey vegetation, and should consequently not be extrapolated across vegetation layers.

Summary Invertebrates supporting natural pest control and pollination ecosystem services are crucial to world‐wide crop production. Understanding national patterns in the spatial structure of natural pest control and pollination can be used to promote effective crop management and contribute to long‐term food security. We mapped the species richness and functional diversity of ground beetles and bees to provide surrogate measures of natural pest control and pollination for Great Britain. Functional diversity represents the value and range of morphological and behavioural traits that support ecosystem services. We modelled the rate at which functional diversity collapsed in response to species extinctions to provide an index of functional redundancy. Deficits in functional diversity for both pest control and pollination were found in areas of high arable crop production. Ground beetle functional redundancy was positively correlated with the landscape cover of semi‐natural habitats where extinctions were ordered by body size and dispersal ability. For bees, functional redundancy showed a weak positive correlation with semi‐natural habitat cover where species extinctions were ordered by feeding specialization. Synthesis and applications. Increasingly, evidence suggests that functionally diverse assemblages of ground beetles and bees may be a key element to strategies that aim to support pollination and natural pest control in crops. If deficits in both functional diversity and redundancy in areas of high crop production are to be reversed, then targeted implementation of agri‐environment schemes that establish semi‐natural habitat may provide a policy mechanism for supporting these ecosystem services.

Human activities have disrupted the functioning of river ecosystems around the world. In the Amazon basin, hydropower expansion has affected diversity patterns, but no study has investigated how phytoplankton assemblages respond to impoundments. This study investigated the hypothesis that phytoplankton diversity is highly sensitive to river damming in large tropical rivers, declining in impoundment areas. We examined patterns of taxonomic diversity (i.e., richness, biovolume, and composition), functional diversity (Reynolds Functional Groups, RFGs), and functional redundancy (i.e., number of taxa in each RFG) along the Tocantins River, before and after the construction of Estreito Hydropower Dam. We monitored five sites along the river (ca. 260 km) between December 2009 and May 2013. The dam changed environmental conditions related to flow, nutrient supply, and depth. We recorded 140 taxa and 26 RFGs in the area. Taxa richness, biovolume, and the number of RFGs declined significantly after river regulation. Composition and abundance ranks changed over periods, and the codons C, Y, TC, W1, and LO were eliminated; functional redundancy declined significantly. These results show that phytoplankton diversity is sensitive to river regulation in large tropical rivers, where changes in hydrology and environmental filters lead to significant losses in taxonomic and functional diversity.

Assessing the effects of landscape structure on the relationship between species diversity and functional diversity