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Functional diversity of habitat formers declines scale-dependently across an environmental stress gradient.

ABSTRACT: Marine habitat formers such as seaweeds and corals are lynchpins of coastal ecosystems, but their functional diversity and how it varies with scale and context remains poorly studied. Here, we investigate the functional diversity of seaweed assemblages across the rocky intertidal stress gradient at large (zones) and small (quadrat) scales. We quantified complementary metrics of emergent group richness, functional richness (functional space occupied) and functional dispersion (trait complementarity of dominant species). With increasing shore height, under species loss and turnover, responses of functional diversity were scale- and metric-dependent. At the large scale, functional richness contracted while-notwithstanding a decline in redundancy-emergent group richness and functional dispersion were both invariant. At the small scale, all measures declined, with the strongest responses evident for functional and emergent group richness. Comparisons of observed versus expected values based on null models revealed that functional richness and dispersion were greater than expected in the low shore but converged with expected values higher on the shore. These results show that functional diversity of assemblages of marine habitat formers can be especially responsive to environmental stress gradients at small scales and for richness measures. Furthermore, niche-based processes at the small-neighbourhood-scale can favour co-occurrence of functionally distinctive species under low, but not high, stress, magnifying differences in functional diversity across environmental gradients. As assemblages of marine habitat formers face accelerating environmental change, further studies examining multiple aspects of functional diversity are needed to elucidate patterns, processes, and ecosystem consequences of community (dis-)assembly across diverse groups.

SUBMITTER: Cappelatti L

PROVIDER: S-EPMC7561580 | biostudies-literature | 2020 Oct

REPOSITORIES: biostudies-literature

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Functional diversity of habitat formers declines scale-dependently across an environmental stress gradient.

Cappelatti Laura L Mauffrey Alizée R L ARL Griffin John N JN

Oecologia 20200907 1-2

Marine habitat formers such as seaweeds and corals are lynchpins of coastal ecosystems, but their functional diversity and how it varies with scale and context remains poorly studied. Here, we investigate the functional diversity of seaweed assemblages across the rocky intertidal stress gradient at large (zones) and small (quadrat) scales. We quantified complementary metrics of emergent group richness, functional richness (functional space occupied) and functional dispersion (trait complementari ...[more]

PMID: 32895733

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Project description:Global patterns of plant biomass drive the distribution of much of the marine and terrestrial life on Earth. This is because their biomass and physical structure have important consequences for the communities they support by providing food and habitat. In terrestrial ecosystems, temperature is one of the major determinants of plant biomass and can influence plant and leaf morphology. In temperate marine systems, macroalgae are major habitat-formers and commonly display highly variable morphology in response to local environmental conditions. Variation in their morphology, and thus habitat structure on temperate reefs, however, is poorly understood across large scales. In this study, we used a trait-based approach to quantify morphological variability in subtidal rocky reefs dominated by the algal genus Sargassum along a latitudinal gradient, in southeastern Australia (~900 km). We tested whether large-scale variation in sea surface temperature (SST), site exposure, and nutrient availability can predict algal biomass and individual morphology. We found Sargassum biomass declined with increasing maximum SST. We also found that individual morphology varied with abiotic ocean variables. Frond size and intraindividual variability in frond size decreased with increasing with distance from the equator, as SST decreased and nitrate concentration increased. The shape of fronds displayed no clear relationship with any of the abiotic variables measured. These results suggest climate change will cause significant changes to the structure of Sargassum habitats along the southeastern coast of Australia, resulting in an overall reduction in biomass and increase in the prevalence of thalli with large, highly variable fronds. Using a space-for-time approach means shifts in morphological trait values can be used as early warning signs of impending species declines and regime shifts. Consequently, by studying traits and how they change across large scales we can potentially predict and anticipate the impacts of environmental change on these communities.

Project description:BackgroundEnvironmental stress is widely considered to be an important factor in regulating whether changes in diversity will affect the functioning and stability of ecological communities.Methodology/principal findingsWe investigated the effects of a major environmental stressor (a decrease in water volume) on diversity-abundance and diversity-stability relations in laboratory microcosms composed of temperate multi-trophic rock pool communities to identify differences in community and functional group responses to increasing functional group richness along a gradient of environmental stress (low, medium, and high water volume). When a greater number of functional groups were present, communities were less temporally variable and achieved higher abundances. The stabilizing effect of increased functional group richness was observed regardless of the level of environmental stress the community was subjected too. Despite the strong consistent stabilizing effect of increased functional group richness on abundance, the way that individual functional groups were affected by functional group richness differed along the stress gradient. Under low stress, communities with more functional groups present were more productive and showed evidence of strong facilitative interactions. As stress increased, the positive effect of functional group richness on community abundance was no longer observed and compensatory responses became more common. Responses of individual functional groups to functional group richness became increasing heterogeneous are stress increased, prompting shifts from linear diversity-variability/abundance relations under low stress to a mix of linear and non-linear responses under medium and high stress. The strength of relations between functional group richness and both the abundances and temporal variability of functional groups also increased as stress increased.Conclusions/significanceWhile stress did not affect the relation between functional group richness and stability per se, the way in which functional groups responded to changes in functional group richness differed as stress increased. These differences, which include increases in the heterogeneity of responses of individual functional groups, increases in compensatory dynamics, and increases in the strength of richness-abundance and richness-variability relations, may be critical to maintaining stability under increasingly stressful environmental conditions.

Project description:Mountains provide an interesting context in which to study the many facets of biodiversity in response to macroclimate, since environmental conditions change rapidly due to elevation. Although the decrease in biodiversity with increasing elevation is generally accepted, our understanding of the variation of functional diversity along altitudinal gradients is still poorly known. The partitioning of diversity into spatial components can help to understand the processes that influence the distribution of species, and these studies are urgently needed in face of the increasing threats to mountain environments throughout the world. We describe the distribution of dung beetle diversity along an altitudinal gradient on a tropical mountain in southeastern Brazil, including the spatial partitioning of taxonomic and functional diversities. The altitudinal gradient ranged from 800 up to 1400 m a.s.l. and we collected dung beetles at every 100 m of altitude. We used the Rao Index to calculate γ, α and β diversity for taxonomic and functional diversity of dung beetles. Climatic, soil and vegetation variables were used to explain variation in community attributes along the altitudinal gradient. Dung beetle richness declined with altitude and was related to climatic and vegetation variables, but functional diversity did not follow the same pattern. Over 50% of γ taxonomic diversity was caused by among altitudes diversity (β), while almost 100% of functional diversity was due to the α component. Contrasting β taxonomic with β functional diversity, we suggest that there is ecological redundancy among communities and that the environment is filtering species in terms of the Grinnellian niche, rather than the Eltonian niche. β taxonomic diversity is caused mainly by the turnover component, reinforcing the hypothesis of environmental filtering. Global warming may have strong effects on mountain communities due to upslope range shifts and extinctions, and these events will lead to an even larger than previously expected loss of diversity as dung beetles γ taxonomic diversity is caused mainly by the β component.

Project description:Background: Human activities have resulted in a rapid increase of modified habitats in proximity to wildlife habitats in the Himalaya. However, it is crucial to understand the extent to which human habitat modification affects wildlife. Mesocarnivores generally possess broader niches than large carnivores and adapt quickly to human activities. Here, we use a case study in the western Himalaya to test the hypothesis that human disturbance influenced mesocarnivore habitat use. Methods: We used camera trapping and mitochondrial DNA-based species identification from faecal samples to obtain mesocarnivore detections. We then compared the responses of mesocarnivores between an anthropogenic site and a less disturbed park along a contiguous gradient in habitat quality. The non-linear pattern in species-specific habitat selection and factors responsible for space usage around villages was captured using hierarchical generalized additive modelling (HGAM) and non-metric multidimensional scaling (NMDS) ordination. Results: Wildlife occurrences along the gradient varied by species. Leopard cat and red fox were the only terrestrial mesocarnivores that occurred in both anthropogenic site and park. We found a shift in habitat selection from less disturbed habitat in the park to disturbed habitat in anthropogenic site for the species detected in both the habitat types. For instance, red fox showed habitat selection towards high terrain ruggedness (0.5 to 0.7 TRI) and low NDVI (-0.05 to 0.2) in the park but no such specific selection in anthropogenic site. Further, leopard cat showed habitat selection towards moderate slope (20°) and medium NDVI (0.5) in park but no prominent habitat selections in anthropogenic site. The results revealed their constrained behaviour which was further supported by the intensive site usage close to houses, agricultural fields and human trails in villages. Conclusions: Our results indicate shifts in habitat selection and intensive site usage by mesocarnivores in the human-modified habitat. In future, this suggests the possibility of conflict and disease spread affecting both the people and wildlife. Therefore, this study highlights the requisite to test the wildlife responses to rapidly growing human expansions in modified habitats to understand the extent of impact. The management strategies need to have an integrated focus for further expansions of modified habitat and garbage disposal strategies, especially in the human-wildlife interface area.

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Functional diversity of habitat formers declines scale-dependently across an environmental stress gradient.

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Functional diversity of habitat formers declines scale-dependently across an environmental stress gradient.

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