Functional richness: Overview of indices and underlying concepts

Cumulative human impacts on global marine fauna highlight risk to biological and functional diversity

Anthropogenic stressors to marine ecosystems from climate change and human activities increase extinction risk of species, disrupt ecosystem integrity, and threaten important ecosystem services. Addressing these stressors requires understanding where and to what extent they are impacting marine biological and functional diversity. We model cumulative risk of human impact upon 21,159 marine animal species by combining information on species-level vulnerability and spatial exposure to a range of anthropogenic stressors. We apply this species-level assessment of human impacts to examine patterns of species-stressor interactions within taxonomic groups. We then spatially map impacts across the global ocean, identifying locations where climate-driven impacts overlap with fishing, shipping, and land-based stressors to help inform conservation needs and opportunities. Comparing species-level modeled impacts to those based on marine habitats that represent important marine ecosystems, we find that even relatively untouched habitats may still be home to species at elevated risk, and that many species-rich coastal regions may be at greater risk than indicated from habitat-based methods alone. Finally, we incorporate a trait-based metric of functional diversity to identify where impacts to functionally unique species might pose greater risk to community structure and ecosystem integrity. These complementary lenses of species, function, and habitat provide a richer understanding of threats to marine biodiversity to help inform efforts to meet conservation targets and ensure sustainability of nature's contributions to people.

Dynamic shifts of functional diversity through climate-resilient strategies and farmland restoration in a mountain protected area

Land-use land-cover (LULC) change contributes to major ecological impacts, particularly in areas undergoing land abandonment, inducing modifications on habitat structure and species distributions. Alternative land-use policies are potential solutions to alleviate the negative impacts of contemporary tendencies of LULC change on biodiversity. This work analyzes these tendencies in the Montesinho Natural Park (Portugal), an area representative of European abandoned mountain rural areas. We built ecological niche models for 226 species of vertebrates (amphibians, reptiles, birds, and mammals) and vascular plants, using a consensus modelling approach available in the R package 'biomod2'. We projected the models to contemporary (2018) and future (2050) LULC scenarios, under four scenarios aiming to secure relevant ecosystem services and biodiversity conservation for 2050: an afforestation and a rewilding scenario, focused on climate-smart management strategies, and a farmland and an agroforestry recovery scenario, based on re-establishing human traditional activities. We quantified the influences of these scenarios on biodiversity through species habitat suitability changes for 2018-2050. We analyzed how these management strategies could influence indices of functional diversity (functional richness, functional evenness and functional dispersion) within the park. Habitat suitability changes revealed complementary patterns among scenarios. Afforestation and rewilding scenarios benefited more species adapted to habitats with low human influence, such as forests and open woodlands. The highest functional richness and dispersion was predicted for rewilding scenarios, which could improve landscape restoration and provide opportunities for the expansion and recolonization of forest areas by native species. The recovery of traditional farming and agroforestry activities results in the lowest values of functional richness, but these strategies contribute to complex landscape matrices with diversified habitats and resources. Moreover, this strategy could offer opportunities for fire suppression and increase landscape fire resistance. An integrative approach reconciling rewilding initiatives with the recovery of extensive agricultural and agroforestry activities is potentially an harmonious strategy for supporting the provision of ecosystem services while securing biodiversity conservation and functional diversity within the natural park.

Taxonomic, phylogenetic, and functional diversity of mollusk death assemblages in coral reef and seagrass sediments from two shallow gulfs in Western Cuban Archipelago

Mollusk death assemblages are formed by shell remnants deposited in the surficial mixed layer of the seabed. Diversity patterns in tropical marine habitats still are understudied; therefore, we aimed to investigate the taxonomic, phylogenetic, and functional diversity of mollusk death assemblages at regional and local scales in coral reef sands and seagrass meadows. We collected sediment samples at 11 sites within two shallow gulfs in the Northwestern Caribbean Sea and Southeastern Gulf of Mexico. All the shells were counted and identified to species level and classified into biological traits. We identified 7113 individuals belonging to 393 species (290 gastropods, 94 bivalves, and nine scaphopods). Diversity and assemblage structure showed many similarities between gulfs given their geological and biogeographical commonalities. Reef sands had higher richness than seagrasses likely because of a more favorable balance productivity-disturbance. Reef sands were dominated by epifaunal herbivores likely feeding on microphytobenthos and bysally attached bivalves adapted to intense hydrodynamic regime. In seagrass meadows, suspension feeders dominated in exposed sites and chemosynthetic infaunal bivalves dominated where oxygen replenishment was limited. Time averaging of death assemblages was likely in the order of 100 years, with stronger effects in reef sands compared to seagrass meadows. Our research provides evidence of the high taxonomic, phylogenetic, and functional diversity of mollusk death assemblages in tropical coastal sediments as result of the influence of scale-related processes and habitat type. Our study highlights the convenience of including phylogenetic and functional traits, as well as dead shells, for a more complete assessment of mollusk biodiversity.

Existing levels of biodiversity and river location may determine changes from small hydropower developments

Global ecosystems are facing anthropogenic threats that affect their ecological functions and biodiversity. However, we still lack an understanding of how biodiversity can mediate the responses of ecosystems or communities to human disturbance across spatial gradients. Here, we examined how existing, spatial patterns of biodiversity influence the ecological effects of small hydropower plants (SHPs) on macroinvertebrates in river ecosystems. This study found that levels of biodiversity (e.g., number of species) can influence the degrees of its alterations by SHPs occurring along elevational gradients. The results of the study reveal that the construction of SHPs has various effects on biodiversity. For example, low-altitude areas with low biodiversity (species richness less than 12) showed a small increase in biodiversity compared to high-altitude areas (species richness more than 12) under SHP disturbances. The increases in the effective habitat area of the river segment could be a driver of the enhanced biodiversity in response to SHP effects. Changes in the numerically dominant species contributed to the overall level of community variation from disturbances. Location-specific strategies may mitigate the effects of SHPs and perhaps other disturbances.

Climate change filtered out resource-acquisitive plants in a temperate grassland in Inner Mongolia, China

Global climate change has led to the decline of species and functional diversity in ecosystems, changing community composition and ecosystem functions. However, we still know little about how species with different resource-use strategies (different types of resource usage and plant growth of plants as indicated by the spectrum of plant economic traits, including acquisitive resource-use strategy and conservative resource-use strategy) would change in response to climate change, and how the changes in the diversity of species with different resource-use strategies may influence community-level productivity. Here, using long-term (1982-2017) observatory data in a temperate grassland in Inner Mongolia, we investigated how climate change had affected the species richness (SR) and functional richness (FRic) for the whole community and for species with different resource-use strategies. Specifically, based on data for four traits representing leaf economics spectrum (leaf carbon concentration, leaf nitrogen concentration, leaf phosphorus concentration, and specific leaf area), we divided 81 plant species appearing in the grassland community into three plant functional types representing resource-acquisitive, medium, and resource-conservative species. We then analyzed the changes in community-level productivity in response to the decline of SR and FRic at the community level and for different resource-use strategies. We found that community-level SR and FRic decreased with drying climate, which was largely driven by the decline of diversity for resource-acquisitive species. However, community-level productivity remained stable because resource-conservative species dominating this grassland were barely affected by climate change. Our study revealed distinctive responses of species with different resource-use strategies to climate change and provided a new approach based on species functional traits for predicting the magnitude and direction of climate change effects on ecosystem functions.

Landscape-scale benefits of protected areas for tropical biodiversity

The United Nations recently agreed to major expansions of global protected areas (PAs) to slow biodiversity declines1. However, although reserves often reduce habitat loss, their efficacy at preserving animal diversity and their influence on biodiversity in surrounding unprotected areas remain unclear2-5. Unregulated hunting can empty PAs of large animals6, illegal tree felling can degrade habitat quality7, and parks can simply displace disturbances such as logging and hunting to unprotected areas of the landscape8 (a phenomenon called leakage). Alternatively, well-functioning PAs could enhance animal diversity within reserves as well as in nearby unprotected sites9 (an effect called spillover). Here we test whether PAs across mega-diverse Southeast Asia contribute to vertebrate conservation inside and outside their boundaries. Reserves increased all facets of bird diversity. Large reserves were also associated with substantially enhanced mammal diversity in the adjacent unprotected landscape. Rather than PAs generating leakage that deteriorated ecological conditions elsewhere, our results are consistent with PAs inducing spillover that benefits biodiversity in surrounding areas. These findings support the United Nations goal of achieving 30% PA coverage by 2030 by demonstrating that PAs are associated with higher vertebrate diversity both inside their boundaries and in the broader landscape.

Non-interactive effects drive multiple stressor impacts on the taxonomic and functional diversity of atlantic stream macroinvertebrates

Freshwaters are considered among the most endangered ecosystems globally due to multiple stressors, which coincide in time and space. These local stressors typically result from land-use intensification or hydroclimatic alterations, among others. Despite recent advances on multiple stressor effects, current knowledge is still limited to manipulative approaches minimizing biological and abiotic variability. Thus, the assessment of multiple stressor effects in real-world ecosystems is required. Using an extensive survey of 50 stream reaches across North Portugal, we evaluated taxonomic and functional macroinvertebrate responses to multiple stressors, including marked gradients of nutrient enrichment, flow reduction, riparian vegetation structure, thermal stress and dissolved oxygen depletion. We analyzed multiple stressor effects on two taxonomic (taxon richness, Shannon-diversity) and two trait-based diversity indices (functional richness, functional dispersion), as well as changes in trait composition. We found that multiple stressors had additive effects on all diversity metrics, with nutrient enrichment identified as the most important stressor in three out of four metrics, followed by dissolved oxygen depletion and thermal stress. Taxon richness, Shannon-diversity and functional richness responded similarly, whereas functional dispersion was driven by changes in flow velocity and thermal stress. Functional trait composition changed along a major stress gradient determined by nutrient enrichment and oxygen depletion, which was positively correlated with organisms possessing fast-living strategies, aerial respiration, adult phases, and gathering-collector feeding habits. Overall, our results reinforce the need to consider complementary facets of biodiversity to better identify assembly processes in response to multiple stressors. Our data suggest that stressor interactions may be less frequent in real-word streams than predicted by manipulative experiments, which can facilitate mitigation strategies. By combining an extensive field survey with an integrative consideration of multiple biodiversity facets, our study provides new insights that can help to better assess and manage rivers in a global change context.

Decomposing niche components reveals simultaneous effects of opposite deterministic processes structuring alpine small mammal assembly

Introduction

Species distribution in alpine areas is constrained by multiple abiotic and biotic stressors. This leads to discrepant assembly patterns between different locations and study objects as opposite niche-based processes—limiting similarity and habitat filtering—simultaneously structure communities, masking overall patterns. We aimed to address how these processes structure small mammal communities in the alpine tree line transition zone, one of the most distinct vegetation transitions between alpine and montane habitats.

Methods

We compiled a dataset of species checklist, phylogeny, and functional traits from field collection and published sources spanning 18 mountains in southwest China. We first examined hypothetical niche-based processes with frequently used phylogenetic and trait approaches using this dataset. The species traits were decomposed into different niche components to explore the respective effects of specific stressors. Indices representing evolutionary history, trait space, and pairwise species distance were estimated and compared with null model expectations. Linear mixed-effect models were used to assess the association patterns between diversity indices and elevation.

Results

The results indicated that phylogenetic and functional richness were positively correlated with species richness. In contrast, distance-based indices were either negatively or weakly positively correlated with species richness. Null model analyses suggested no evidence of non-random phylogenetic or overall trait patterns. However, the resource acquisition niche tended to be more overdispersed (positive slopes), while the habitat affinity niche tended to be more clustered (negative slopes) beyond the high elevation tree line.

Discussion

These findings show that opposite niche-based processes simultaneously structure small mammal communities in alpine areas. Overall, the present study provides vital insights into the complexity of assembly processes in these habitats. It also highlights the importance of relating relevant traits to distinguish the influences of specific abiotic and biotic stressors.

Small run-of-river hydropower dams and associated water regulation filter benthic diatom traits and affect functional diversity

Knowledge of benthic diatom traits can help understand ecosystem function and guide biodiversity conservation. This is particularly important in rivers on which there are small run-of-river dams, which currently receive less attention. These dams generate power by drawing water from upstream and discharging it downstream after a large drop in penstock. We examine 15 functional diatom traits in habitats upstream, surrounding, and downstream of 23 small run-of-river dams in Xiangxi River, China. We compare the effects of these small dams on benthic diatom species traits, and taxonomic and functional diversity, from 90 sites. Dams change local environmental (e.g., channel width, flow velocity, depth) and physicochemical (e.g., dissolved oxygen, water temperature) variables, and a shift in diatom life forms and guilds is apparent, from taxa with strong attachment and low profile in high velocity waters (i.e., H1, H2 and H4) to those with weak attachment or that are planktonic below dams and outlets (i.e., H3 and H5), and towards high profile taxa below dams. Significant differences in biodiversity, particularly in functional richness, redundancy, and evenness, are apparent. Species and functional diversity indices are influenced by physical and chemical environmental factors (especially flow velocity and water depth). We found that diatom functional traits reflect longitudinal changes in flow and ecological condition, and suggest that monitoring such traits could be useful in adjusting flows to minimize ecosystem impacts. To maintain ecological flow and reasonable water depth within rivers we advocate for improved connectivity, carrying capacity and resilience of water ecosystems via a long-term, trait-based understanding of the impacts of small run-of-river dams.

Intensive human land uses negatively affect vertebrate functional diversity

Land-use change is the leading driver of global biodiversity loss thus characterising its impacts on the functional structure of ecological communities is an urgent challenge. Using a database describing vertebrate assemblages in different land uses, we assess how the type and intensity of land use affect the functional diversity of vertebrates globally. We find that human land uses alter local functional structure by driving declines in functional diversity, with the strongest effects in the most disturbed land uses (intensely used urban sites, cropland and pastures), and among amphibians and birds. Both tropical and temperate areas experience important functional losses, which are only partially offset by functional gains. Tropical assemblages are more likely to show decreases in functional diversity that exceed those expected from species loss alone. Our results indicate that land-use change non-randomly reshapes the functional structure of vertebrate assemblages, raising concerns about the continuation of ecological processes sustained by vertebrates.

Investigating the direct and indirect effects of forest fragmentation on plant functional diversity

Ongoing habitat loss and fragmentation alter the functional diversity of forests. Generalising the magnitude of change in functional diversity of fragmented landscapes and its drivers is challenging because of the multiple scales at which landscape fragmentation takes place. Here we propose a multi-scale approach to determine whether fragmentation processes at the local and landscape scales are reducing functional diversity of trees in the East Usambara Mountains, Tanzania. We employ a structural equation modelling approach using five key plant traits (seed length, dispersal mode, shade tolerance, maximum tree height, and wood density) to better understand the functional responses of trees to fragmentation at multiple scales. Our results suggest both direct and indirect effects of forest fragmentation on tree functional richness, evenness and divergence. A reduction in fragment area appears to exacerbate the negative effects resulting from an increased amount of edge habitat and loss of shape complexity, further reducing richness and evenness of traits related to resource acquisition and favouring tree species with fast growth. As anthropogenic disturbances affect forests around the world, we advocate to include the direct and indirect effects of forest fragmentation processes to gain a better understanding of shifts in functional diversity that can inform future management efforts.

Spiders (Arachnida: Araneae) in the semideciduous Atlantic Forest: An ecological and morphological trait dataset for functional studies

Background

The semideciduous Atlantic Forest is one of the most diverse ecosystems in the world with a great diversity of spiders. Most spider-related studies in this ecosystem focused on species richness and composition; however, little is known about their trait diversity (including morphological, ecological and/or physiological traits). Two main datasets were compiled to generate a complete record of spider traits for this ecosystem.

New information

Here, we present two datasets about 259 species of spiders from the semideciduous Atlantic Forest of Argentina. The trait data set compiled information of morphological and ecological traits such as body size, femur length, ocular distance, foraging strategy, prey range, circadian activity and stratum preference; traits were assessed by species considering sexual dimorphism. The second dataset included information about phenology (season when spiders were collected), number of individuals assessed by species and presence/absence of spiders in the different sample sites. This dataset has high potential to help researchers in recording the state of a component of biodiversity (functional) and contributes with the study of ecosystem services and species conservation.

The Aquatic Organisms Diversity, Community Structure, and Environmental Conditions

Two main aspects of the study of diversity can be distinguished: the first is related to the inventory of living organisms, the second is related to the organization of life at the level of biotic communities. Quantitative assessment of diversity is two-components as the richness of elements and their evenness. A model of the ecosystem continuum is proposed. The greatest indicators of diversity should be expected in the middle part of the environmental gradients with temporal stability. Study of producers and consumers in water bodies of Ukraine showed a regular change in their community structure in the gradient of saprobity indices. The decreasing of community diversity estimated by the Shannon index and by species richness was found at both high and low values of the saprobity indices. The fundamental coincidence of the empirical point fields of the Shannon index for the communities of invertebrates and phytoplankton with the field points of the empirical model indicates the universality of the bimodal distribution of diversity indicators in the trophic gradient. It is shown that the estimates by zoobenthos overestimate organic pollution compared with the calculations of the same indicators by phytoplankton.

Plant community responses to environmentally friendly piste management in northeast Iran

It is well-known that pistes have adverse effects on alpine ecosystems. Previous studies urged that pistes should be installed and managed in the ways to minimize negative impacts on natural habitats. However, the impacts of this type of management on the plant communities are not widely studied. The aim of this study was to examine species composition and biodiversity changes in an environmentally friendly managed piste in northeast Iran. This piste has been established in a previously degraded alpine landscape. For the vegetation survey, we sampled 44 within and 28 off-piste plots. Except for the piste management, other environmental factors were similar between the piste and off-piste plots. Dominant species were determined, and variation in community composition of the two areas was visualized. Also, native species, phylogenetic, and functional Hill diversity of the two areas were compared. The results showed that there was a moderate differentiation in the species composition of the piste and off-piste. Two palatable species (i.e., Bupleurum falcatum and Melica persica) were dominant in the piste and were not recorded in the off-piste. The diversity calculations results showed that the species diversity of the piste was higher than that of the off-piste. Phylogenetic diversity at the level of frequent and dominant plants showed a similar result. The piste had a higher functional diversity in terms of functional richness, and functional diversity of frequent and dominant plants. Our findings imply, after 10 years, species, phylogenetic, and functional diversity of the piste is significantly improved. Environmentally friendly piste management (EFPM) induced species composition change that led to emerging species that were absent in the off-piste. We can conclude that EFPM led to restoration of a degraded landscape. Long-term impacts of EFPM are still unknown, therefore, caution should be undertaken regarding the installation of new environmentally friendly pistes in other areas.