Patterns Of Functional Beta Diversity Research Articles

Interactions between land use, taxonomic group and aspects and levels of diversity in a Brazilian savanna: Implications for the use of bioindicators

Abstract The conversion of natural habitats into anthropogenic uses is a key driver of global biodiversity loss, but effects can vary among taxa and diversity metrics. This has important implications for the use of bioindicators in land management. We evaluated the local‐scale responses of multiple faunal taxa to land‐use change in the Brazilian Cerrado measuring different aspects (taxonomic and functional) and levels (alpha and beta) of diversity. We compared ant, dung beetle and bird assemblages inhabiting remnants of natural habitat (savanna and semi‐deciduous forest) with those found in cattle pastures, soy fields or Eucalyptus plantations. Species richness was markedly higher in natural habitats for ants and birds but not for dung beetles. Effects on functional alpha diversity were taxon specific and there was not such a contrast between natural and anthropogenic habitats. Patterns of functional beta diversity were correlated with patterns of taxonomic beta diversity and were also taxon specific. For dung beetles, site‐to‐site variation in taxonomic and functional composition was greatest in forests, whereas birds tended to present greater spatial turnover and ants greater nestedeness in the anthropogenic than in the natural habitats. Among the three anthropogenic land uses, tree plantations presented the most similar composition to natural habitat for all taxa. Overall, similarity in taxonomic and functional composition between natural and anthropogenic habitats was greater for savanna than forest. Synthesis and applications. The responses of ant, dung beetle and bird assemblages to land‐use change in the Cerrado were highly variable. Nonetheless, results indicate that the extent of impacts on biodiversity reflects the extent of habitat transformation and that impacts at a landscape scale may be reduced by a mix of land uses. We showed that effects were more severe from a taxonomic than from a functional perspective, for the forest than for the savanna‐associated fauna, for the ant and bird than for the dung beetle fauna, and often in lands devoted to intensive agriculture rather than to pastoralism or plantation forestry. Our findings can help guide the selection and assessment of indicator taxa and the interpretation of exactly what they are indicating.

Drivers of Taxonomic, Phylogenetic, and Functional Beta Diversity of Himalayan Riverine Birds

Abiotic and biotic factors drive compositional differences among local species assemblages. Determining the influence of different drivers on beta diversity patterns can provide insights into processes governing community organization. Examining beta diversity patterns along taxonomic, phylogenetic and functional dimensions enables a nuanced understanding of underlying processes that govern community assembly and dynamics. The dynamic and complex riparian habitats in the Himalaya, and the hyper-diverse riverine bird community offer a fascinating setup to examine the role of environmental factors in influencing community structuring. Using a large dataset on river bird communities from field census across multiple drainages in the Indian Himalaya, we aimed at discerning processes that structure these communities through an understanding of pair-wise dissimilarities in species composition across sites. We determined the relative contributions of turnover and nestedness in taxonomic, phylogenetic, and functional beta diversity patterns in the Eastern and Western Himalaya that differ in species richness. Generalized Dissimilarity Modeling was used to examine the relative contributions of climatic, geographic, and anthropogenic factors toward explaining different metrics of beta diversity. The riverine bird communities in the drier and seasonal Western Himalaya were poorer in species richness, more phylogenetically and functionally clustered than that in the Eastern Himalaya. The contribution of the turnover component to the overall beta diversity was higher than the nestedness component in river bird communities, particularly in the Eastern Himalaya. Habitat and climatic factors differentially influenced the beta diversity patterns in both Eastern and Western Himalaya, with river width consistently explaining a large variation in beta diversity in the east and the west. The results show that environmental filtering plays a crucial role in structuring riverine bird communities in the Himalayan headwaters, highlighting the need to ameliorate the threats posed by the slew of hydroelectric projects and forest loss in the region.

Functional beta diversity of New Zealand fishes: Characterising morphological turnover along depth and latitude gradients, with derivation of functional bioregions

AbstractChanges in the functional structures of communities are rarely examined along multiple large‐scale environmental gradients. Here, we describe patterns in functional beta diversity for New Zealand marine fishes versus depth and latitude, including broad‐scale delineation of functional bioregions. We derived eight functional traits related to food acquisition and locomotion and calculated complementary indices of functional beta diversity for 144 species of marine ray‐finned fishes occurring along large‐scale depth (50–1200 m) and latitudinal gradients (29°–51°S) in the New Zealand Exclusive Economic Zone. We focused on a suite of morphological traits calculated directly from in situ Baited Remote Underwater Stereo‐Video (stereo‐BRUV) footage and museum specimens. We found that functional changes were primarily structured by depth followed by latitude, and that latitudinal functional turnover decreased with increasing depth. Functional turnover among cells increased with increasing depth distance, but this relationship plateaued for greater depth distances (>750 m). In contrast, functional turnover did not change significantly with increasing latitudinal distance at 700–1200 m depths. Shallow functional bioregions (50–100 m) were distinct at different latitudes, whereas deeper bioregions extended across broad latitudinal ranges. Fishes in shallow depths had a body shape conducive to efficient propulsion, while fishes in deeper depths were more elongated, enabling slow, energy‐efficient locomotion, and had large eyes to enhance vision. Environmental filtering may be a primary driver of broad‐scale patterns of functional beta diversity in the deep sea. Greater environmental homogeneity may lead to greater functional homogeneity across latitudinal gradients at deeper depths (700–1200 m). We suggest that communities living at depth may follow a ‘functional village hypothesis’, whereby similar key functional niches in fish communities may be maintained over large spatial scales.

Relative importance of deterministic and stochastic processes for beta diversity of bird assemblages in Yunnan, China

AbstractEvaluating the relative importance of deterministic and stochastic processes underlying taxonomic and functional beta diversity is crucial in community ecology, because it can reveal the dominant processes of community assembly. However, studies of bird communities remain rare and of limited spatial extents. In this study, we described the taxonomic and functional beta diversity patterns of 32 passerine bird assemblages of Yunnan Province, China. We constructed null models based on observed species beta diversity and used multiple regressions on distance matrices to evaluate the relative contributions of deterministic and stochastic processes to passerine bird assemblage dissimilarity. Our results showed significant geographic distance decay in taxonomic and functional similarity, with passerine bird assemblages located in the northwest and southwest of the province having higher functional beta diversity values than expected. Environmental distance and geographic distance explained a similar amount taxonomic beta diversity, but environmental distance explained much more functional beta diversity. Our results suggest that both deterministic and stochastic processes drive taxonomic beta diversity, but that deterministic processes, particularly environmental filtering, play a dominant role in driving functional beta diversity of passerine bird assemblages at sub‐national scale.

Dam promotes downriver functional homogenization of phytoplankton in a transitional river-reservoir system in Amazon

Dams disrupt the longitudinal gradient and decrease the natural connectivity of lotic systems and change the physical, chemical, and biological compartments of the river environment. Here, we investigated the effects of damming and seasonal variation in environmental conditions and richness, density, taxonomic and functional beta diversity patterns of phytoplankton, through dry and rainy seasons (of 2011 and 2012), among four zones (upriver, reservoir, dam, downriver) of the Tucurui dam (Tocantins River sub-basin, eastern Amazon, Brazil). Species were quantified and classified into three functional traits (size class, floating, life form) used to estimate functional beta diversity. We showed that water transparency was higher in the dam, and dry periods presented higher total phosphorus. Our results also demonstrated that the dam promotes species turnover between zones and seasonal periods and that the functional morphological groups respond to local limnological conditions. However, the dam led to a reduction in functional beta diversity—functional homogenization—of phytoplankton species, mainly downstream. We demonstrated that the dam is promoting unfavorable conditions and reducing the environmental heterogeneity, leading to a significant loss of functional traits variation between phytoplankton communities, which compromises the ecosystem processes provided by phytoplankton.

The effect of riverine networks on fish β-diversity patterns in a Neotropical system

We investigated how the riverine network influences taxonomic and functional beta diversity patterns of fish assemblages in the mainstem/headwater (lateral) and upstream/downstream (longitudinal) gradients in a Neotropical river system. We investigated the following questions: which component (turnover or nestedness) explains taxonomic and functional beta diversity in both gradients? Is this component a consistent pattern for different lateral sections of the river basin? Is this component influenced by the spatial extent? Finally, how are taxonomic and functional beta diversity structured by space and environment along the longitudinal gradient? Taxonomic and functional turnover were the main patterns found for the lateral gradient and they were consistent for all lateral sections considered. Taxonomic and functional turnover were also the main patterns for the longitudinal gradient, increasing with the spatial extent increase and being structured by space and spatially structured environments. Our study demonstrates that the dendritic nature of riverine systems constrains species and traits occurrence along lateral and longitudinal gradients in a Neotropical region, generating taxonomic and functional turnover patterns due to the influence of space and spatially structured environments on niche- and dispersal-based processes. These results show that Neotropical riverine systems conservation must go beyond traditional approaches and consider the metacommunity perspective.

Functional and Taxonomic Beta Diversity of Saproxylic Beetles in Mediterranean Forests: On What Factors Do They Depend?

Understanding how biodiversity is distributed across geographical and environmental gradients is a main goal of diversity sciences. However, since ecosystem processes are linked to variation in functional traits of the biota, examining functional beta diversity is particularly important. Our objective was to analyze the taxonomic and functional beta diversity patterns of saproxylic beetle assemblages in evergreen Quercus forest of Spain. We tested whether environmental or geographical distance had a greater influence on taxonomic and functional beta diversity, and if both measures of beta diversity were affected by the same environmental variables. We used 45 flight interception traps distributed in three protected areas over a 12-mo period to sample saproxylic beetles. We measured 13 environmental variables around each trap and the geographical distance between traps. For functional composition, we used 12 functional traits from four functional groups (morphological, phenological, trophic, and a surrogate of physiological). Our results showed that environmental differences between areas influenced the taxonomic and functional beta diversity components (replacement and loss/gain) but in different ways. While replacement components (higher for taxonomic composition) increased with environmental distance, the loss or gain components (higher for functional composition) remained constant, indicating that species replacement mostly involved functionally redundant species. Besides, environmental variables influencing both taxonomic and functional composition were strongly dependent on each area. In conclusion, in well-preserved Mediterranean forests, environmental filtering determines the taxonomic and functional composition of saproxylic beetle assemblages, by favoring species replacement but filtering species traits.

Taxonomic and functional anuran beta diversity of a subtropical metacommunity respond differentially to environmental and spatial predictors.

Anurans exhibit limited dispersion ability and have physiological and behavioural characteristics that narrow their relationships with both environmental and spatial predictors. So, the relative contributions of environmental and spatial predictors in the patterns of taxonomic and functional anuran beta diversity were examined in a metacommunity of 33 ponds along the coast of south Brazil. We expected that neutral processes and, in particular, niche-based processes could have similar influence on the taxonomic and functional beta diversity patterns. Distance-based methods (db-RDA) with variation partitioning were conducted with abundance data to examine taxonomic and functional facets and components (total, turnover and nestedness) in relation to environmental and spatial predictors. Processes determining metacommunity structure differed between the components of beta diversity and among taxonomic and functional diversity. While taxonomic beta diversity was further accounted by both environmental and spatial predictors, functional beta diversity responded more strongly to spatial predictors. These two contrasting patterns were different to what we had predicted, suggesting that while there is a taxonomic turnover mediated by environmental filters, the spatial distance promotes the trait dissimilarity between sites. In addition, our data confirm that neutral and niche-based processes operate on anuran metacommunities even at short geographic scales. Our results reinforce the idea that studies aiming to evaluate the patterns of structure in metacommunities should include different facets of diversity so that better interpretations can be achieved.

Local and regional drivers of turnover and nestedness components of species and functional beta diversity in lake macrophyte communities in China

Beta diversity describes the variation in species composition between sites and is often influenced by both local and regional processes. Partitioning beta diversity into turnover (species replacement between sites) and nestedness (richness difference between sites) components may enhance our understanding of the mechanisms behind the local and regional drivers determining species composition across spatial scales. We sampled macrophyte communities in 24 lakes in two regions (Yangtze River basin and Yunnan-Guizhou plateau) of China covering broad climate and nutrient gradients. Based on both species and functional approaches, we calculated multiple-site beta diversity using the Sørensen dissimilarity index and partitioned it into turnover and nestedness coefficients crossed with two nested spatial scales: among depths within transects (transect scale) and among transects within lakes (lake scale). The overall species beta diversity and functional beta diversity (i.e. Sørensen coefficient) were significantly lower and thus more homogeneous at lake scale. Across spatial scales, species beta diversity was mainly explained by turnover patterns (56–61%) and functional beta diversity primarily by nestedness patterns (58–65%). Both local and regional drivers contributed to structuring species and functional beta diversity patterns, largely through changes in species turnover and functional nestedness, respectively. Overall, we observed a significant increase in species beta diversity and its turnover component while a decreasing trend in functional beta diversity and its nestedness component at high altitude. Our results further emphasized that the species beta diversity and its turnover component decreased at high total phosphorus concentration (TP) across the two spatial scales, while the functional beta diversity and its nestedness component decreased at high TP at the transect scale. We conclude that understanding of the relative role of local and regional drivers in determining macrophyte diversity patterns may help managers to select the most appropriate conservation strategies for preservation of biodiversity varying with the scale in focus.

Functional beta-diversity patterns reveal deterministic community assembly processes in eastern North American trees

Aim Determining the relative influence of niche-based and neutral processes in driving the spatial turnover of community composition is a central challenge in community ecology. Spatial patterns of functional turnover, or functional beta diversity, may capture important signals of niche-based assembly processes, but these patterns have not been quantified for communities across broad geographic and environmental gradients. Here, we analyse continental-scale patterns of species and functional beta diversity in relation to space and the environment to assess the relative importance of niche-based and neutral community assembly mechanisms. Location Eastern North America. Methods We use a continental-scale forest plot dataset and functional trait data to quantify spatial patterns of species and functional beta diversity. We use redundancy analysis-based variance partitioning to evaluate the influence of space, soil and climate on beta-diversity metrics. We use a null model approach to test for non-random functional beta diversity given the observed patterns of species turnover across spatial scales. Results Species and functional beta diversity increased with increasing geographic distance (i.e. distance decay of community similarity). Results of variance partitioning analysis show that species and functional beta diversity were spatially structured and significantly related to environmental, particularly climatic, variation. Results of null model analysis show that functional beta diversity was lower than expected based on species turnover at fine scales (< 600 km) and higher than expected at broad scales (> 1800 km). Main conclusions The observed patterns of functional beta diversity support a niche-based model of community assembly, driven by the deterministic filtering of species across environmental gradients based on their functional traits.

Deterministic tropical tree community turnover: evidence from patterns of functional beta diversity along an elevational gradient

Explaining the mechanisms that produce the enormous diversity within and between tropical tree communities is a pressing challenge for plant community ecologists. Mechanistic hypotheses range from niche-based deterministic to dispersal-based stochastic models. Strong tests of these hypotheses require detailed information regarding the functional strategies of species. A few tropical studies to date have examined trait dispersion within individual forest plots using species trait means in order to ask whether coexisting species tend to be more or less functionally similar than expected given a null model. The present work takes an alternative approach by: (i) explicitly incorporating population-level trait variability; and (ii) quantifying the functional beta diversity in a series of 15 tropical forest plots arrayed along an elevational gradient. The results show a strong pattern of decay in community functional similarity with elevation. These observed patterns of functional beta diversity are shown to be highly non-random and support a deterministic model of tropical tree community assembly and turnover.