Biotic Homogenization Research Articles

The Erosion of Seasonality in Avian Communities

ABSTRACTAimSeasonality governs species composition at a given place and time. However, the effects of climate and land‐use change can vary by season, altering species composition. These changes can lead to a loss of distinct seasonal community composition, representing a novel form of biotic homogenisation. We ask if breeding and winter bird communities are becoming more similar over time. If so, is homogenisation occurring more rapidly in winter than in the breeding season, and has the presence of individual species changed between seasons?LocationNortheastern United States.Time Period1989–2019.Major Taxa StudiedTwo hundred thirty‐eight bird species.MethodsWe use data from The National Audubon Society's Christmas Bird Count and the North American Breeding Bird Survey to test if winter and breeding bird communities have become more similar (homogenised). We evaluate this change using the Sørensen dissimilarity index, and its components of turnover (species replacement) and nestedness (a subset of a more species rich community) and describe the mechanism in which the seasonal winter and breeding bird communities are changing.ResultsWe found that winter and breeding bird communities are homogenising, driven by significant decrease in turnover and a marginal decrease nestedness. When viewing breeding and wintering communities separately, we observe different trends. Breeding communities are becoming more unique with decreasing turnover and nestedness. Winter communities are becoming more similar to each other, with decreasing turnover and nestedness. More breeding species are declining and species that are typically found in the winter and year‐round residents are the main contributors to the homogenisation between seasons.Main ConclusionsWe show for the first time homogenisation between winter and breeding bird communities over time across the northeastern United States. This insight into how individual species are faring between seasons, and how they impact community structure, can be used when implementing conservation measures for maintaining ecological functioning and integrity.

Biotic homogenization in multisystem cascade reservoirs: insights from sedimentary photopigment analysis.

The existing literature provides limited insights into the dynamics of phytoplankton communities and the spatial heterogeneity of physicochemical parameters in multisystem cascade reservoirs (interconnected reservoirs derived from different rivers). The existing studies are concentrated on cascade reservoirs (interconnected reservoirs derived from the same river). To address this knowledge gap, the aims of the present study were as follows: (1) investigate the spatial heterogeneity, within and between reservoirs, of geochemical parameters associated with the eutrophication process, considering total phosphorus, chlorophyll-a, pheophytin, and metals (chromium, copper, nickel, lead, zinc, iron, and manganese); (2) evaluate sediment quality at the designated locations; (3) assess differences in the richness and concentration of sedimentary photopigments between the reservoirs. Application of principal component analysis revealed discernible gradients for the abiotic variables, although the differences were not statistically significant (one-way PERMANOVA test, p > 0.05). The observations suggested a tendency towards spatial homogeneity within and between the reservoirs. The metal concentrations were consistent with regional reference values, while phosphorus levels in the sediment approached the threshold for classification as pollution (~ 2000mg/kg). Analysis of pigments indicated low dissimilarity among the reservoirs, which could be mainly attributed to the eutrophication process and high connectivity of the sampled areas. To counteract ongoing biotic homogenization, it is essential to reduce nutrient inputs and invest in ecological protection and restoration programs. The analysis of sedimentary photopigments provides an efficient and cost-effective alternative way to assess phytoplankton communities.

Camelid herding may homogenize Andean grassland plant communities

The current global decline in biodiversity is a matter of pressing concern, necessitating the conservation of diverse ecosystems across various spatial scales. Regions such as the tropical Andes face the imminent threat of biotic homogenization due to intensive livestock grazing, posing a significant risk to biodiversity. This study is focused on the sub-humid grasslands of northwestern Bolivia, within the the National Park Apolobamba. We surveyed a total of 105 plots distributed across seven sites, representing a natural gradient of grazing intensity. Within each site, the plots were organized into five clusters to explore the impact of environmental factors on plant diversity within and among communities. Our research reveals that local plant diversity, quantified by species richness and the inverse Simpson index, is predominantly shaped by soil pH. Notably, more acidic soil is associated with diminished diversity. Furthermore, our findings highlight that the dissimilarity in species composition among local communities may be linked to grazing intensity. This suggests that intensified grazing may have the potential to homogenize plant communities across the landscape. A concerning implication is the likelihood of communities becoming dominated by acquisitive species, leaving them more susceptible to the impacts of climate variability. The study underlines the necessity to analyze multiple facets of diversity for a comprehensive understanding of the environmental factors regulating and therefore to address potential drivers of diversity loss. To mitigate these threats, managers may consider adjusting livestock quantities and the spatial range used by grazers, aiming to sustain multiple aspects of plant diversity and prevent homogenization and degradation of grasslands in a changing world.

Homogenization of fish assemblages in an endemic biodiversity hot spot: Evidence from 70‐year data from the Yun‐Gui Plateau, China

Abstract The combined impacts of anthropogenic activities and global climate changes threaten native fish communities. Such threats are particularly critical in biodiversity hot spot areas with many endemic species, as exemplified by the isolated Yun‐Gui Plateau, China. The risk of biotic homogenization is also expected to be high in such areas, but this risk and its underlying drivers remain poorly studied. Here, we established a database of fish distributions and used environmental filtering for spatial clusters (n = 3759) in river basins located at Yun‐Gui Plateau. This database was based on public data sources and a comprehensive review of relevant literature (n = 481) covering the period from 1950 to 2021. We divided the plateau into nine subbasins for spatial comparison and into two periods for temporal comparison—before and after the start of rapid economic growth development in 1978. We found: (a) a marginal increase in replacement (species exchange in different subbasins) and similarity index but a decrease in richness difference index, indicating homogenization and the loss of natural barriers across the entire plateau; (b) an increase in species richness accompanied by a discernible decline in phylogenetic diversity, also indicating homogenization; (c) the increase in species richness by species loss‐gain analyses was associated with climatic variables (temperature and precipitation), elevation and human activities in all subbasins. Temporal and spatial comparisons indicated that homogenization of fish assemblages in the Yun‐Gui Plateau was exacerbated by climatic and anthropogenic pressures. The observed homogenization of fish species is of great concern, and we call for systematic assessments and precautionary mitigation actions to maintain the uniqueness of biodiversity in the Yun‐Gui Plateau region.

The productivity-stability trade-off in global food systems.

Historically, humans have managed food systems to maximize productivity. This pursuit has drastically modified terrestrial and aquatic ecosystems globally by reducing species diversity and body size while creating very productive, yet homogenized, environments. Such changes alter the structure and function of ecosystems in ways that ultimately erode their stability. This productivity-stability trade-off has largely been ignored in discussions around global food security. Here, we synthesize empirical and theoretical literature to demonstrate the existence of the productivity-stability trade-off and argue the need for its explicit incorporation in the sustainable management of food systems. We first explore the history of human management of food systems, its impacts on average body size within and across species and food web stability. We then demonstrate how reductions in body size are symptomatic of a broader biotic homogenization and rewiring of food webs. We show how this biotic homogenization decompartmentalizes interactions among energy channels and increases energy flux within the food web in ways that threaten their stability. We end by synthesizing large-scale ecological studies to demonstrate the prevalence of the productivity-stability trade-off. We conclude that management strategies promoting landscape heterogeneity and maintenance of key food web structures are critical to sustainable food production.

Widespread introduced species dominate the urban tree assemblage on the endemic-rich tropical island of São Tomé.

The Afrotropics are experiencing some of the fastest urbanisation rates on the planet but the impact of city growth on their rich and unique biodiversity remains understudied, especially compared to natural baselines. Little is also known about how introduced species influence β-diversity in these contexts, and how patterns coincide with native ranges of species. Here we investigated how tree assemblages of the endemic-rich Afrotropical island of São Tomé differed between urban, rural and natural zones. These were primarily characterised by urban greenspaces, shade plantations, and old-growth forests, respectively. Based on 81 transects, we assessed biodiversity metrics of endemic, native and introduced species. Tree abundance and species richness were highest in the natural zone, where the composition was most different from the urban zone. The tree community of the rural zone was the most uneven and had the least variation among transects, representing the lowest β-diversity. The urban zone was dominated by introduced species (57.7%), while the natural zone hosted almost exclusively native species (93.3%), including many endemics (26.1%). The biogeographic realms that species originated from were particularly diverse in the urban zone, with few species from the Afrotropics. In contrast to native and endemic trees, introduced trees were clearly associated with urban and rural expansion, as they were much more abundant and species-rich in these zones than in the natural zone, facilitating biotic homogenisation. These findings highlight how urban and rural environments are affecting the native tree flora of São Tomé, and the need for conservation measures geared towards globally threatened and endemic tree species. Importantly, these require the protection of natural forests, despite the rising land demands for settlements and agriculture. Ultimately, such action to conserve endemic trees will contribute to global efforts to prevent further biodiversity declines.

Consistent generalization of plant-hummingbird networks despite increasing vegetation cover across a tropical urban landscape

Human activities, particularly urbanization, profoundly impact ecosystems often resulting in biotic homogenization. Whether or not urban landscapes can sustain diverse pollinator and plant communities is an important question to be addressed. Here, we investigated the influence of urbanization on plant-hummingbird interaction networks in a large tropical city, Belo Horizonte, Brazil. We recorded 13198 legitimate interactions between seven hummingbirds and 57 plant species across 12 local networks. Urban landscapes exhibited predominantly generalized networks, maintaining this pattern across varying vegetation cover and floral resource abundance. Although some functionally specialized hummingbirds with long bills were recorded performing more specialized interactions, urban environments did not generally support specialized networks. Nevertheless, network specialization did increase with the proportion of native nectar plants, emphasizing their importance for maintaining some specialized interactions. Furthermore, we observed a positive effect of plant richness, but not of flower abundance, on hummingbird abundance, indicating that it is not only the amount of flowers, but the diversity of floral resources that may be a key factor in maintaining hummingbirds. Therefore, promoting a diverse assemblage of native plants in urban green areas is crucial for sustainable pollinator communities. Our study highlights that while a biodiverse urban landscape will require careful urban vegetation planning considering both floral resource diversity and availability, vegetation cover per se may not be sufficient to mitigate the negative impacts of urbanization. Maintaining a diverse vegetation with different life forms, flowering phenology, and especially of native plants across the urban landscape is needed to create welcoming spaces for pollinators.

Driving factors of earthworm communities in Mediterranean urban parks

Earthworm communities within urban environments remain an intriguing subject. This study aims to unravel the intricate relationship between these communities and the heterogeneous urban soils they inhabit. Urban soils, shaped by past and present human activities, harbor a rich diversity of earthworms, yet the specific factors influencing these communities remain poorly understood.Earthworm communities were sampled across 13 urban parks of Montpellier, a Mediterranean city in France. The effect of four variables at two scales were assessed: (i) landscape attributes within a 100-meter radius surrounding each sampling point and (ii) site-specific factors, including soil properties such as organic carbon content and pH levels, soil age, and management practices. Variation partitioning was employed through partial canonical correspondence analysis in order to disentangle the effects of these variables on earthworm community composition.A total of 16 species were identified out of 1270 individuals collected. Most are ubiquist, with a limited number being endemic to the Mediterranean region, potentially indicating biotic homogenization due to urbanization. In addition, multivariate analyses emphasized the substantial influence of landscape characteristics, composed by the rate of green spaces and the number of patches. These landscape-level attributes and especially the connectivity of green spaces emerged as primary drivers, surpassing the influence of management practices, soil age and soil properties.Thus, this research underscores the importance of considering diverse scales, and particularly landscape-level factors, in comprehending and restoring soil fauna such as earthworm communities within Mediterranean urban parks.

Unravelling the complexities of biotic homogenization and heterogenization in the British avifauna.

Biotic homogenization is a process whereby species assemblages become more similar through time. The standard way of identifying the process of biotic homogenization is to look for decreases in spatial beta-diversity. However, using a single assemblage-level metric to assess homogenization can mask important changes in the occupancy patterns of individual species. Here, we analysed changes in the spatial beta-diversity patterns (i.e. biotic heterogenization or homogenization) of British bird assemblages within 30 km × 30 km regions between two periods (1988-1991 and 2008-2011). We partitioned the change in spatial beta-diversity into extirpation and colonization-resultant change (i.e. change in spatial beta-diversity within each region resulting from both extirpation and colonization). We used measures of abiotic change in combination with Bayesian modelling to disentangle the drivers of biotic heterogenization and homogenization. We detected both heterogenization and homogenization across the two time periods and three measures of diversity (taxonomic, phylogenetic, and functional). In addition, both extirpation and colonization contributed to the observed changes, with heterogenization mainly driven by extirpation and homogenization by colonization. These assemblage-level changes were primarily due to shifting occupancy patterns of generalist species. Compared to habitat generalists, habitat specialists had significantly (i) higher average contributions to colonization-resultant change (indicating heterogenization within a region due to colonization) and (ii) lower average contributions to extirpation-resultant change (indicating homogenization from extirpation). Generalists showed the opposite pattern. Increased extirpation-resultant homogenization within regions was associated with increased urban land cover and decreased habitat diversity, precipitation, and temperature. Changes in extirpation-resultant heterogenization and colonization-resultant heterogenization were associated with differences in elevation between regions and changes in temperature and land cover. Many of the 'winners' (i.e. species that increased in occupancy) were species that had benefitted from conservation action (e.g. buzzard (Buteo buteo)). The 'losers' (i.e. those that decreased in occupancy) consisted primarily of previously common species, such as cuckoo (Cuculus canorus). Our results show that focusing purely on changes in spatial beta-diversity over time may obscure important information about how changes in the occupancy patterns of individual species contribute to homogenization and heterogenization.

Urban stormwater ponds can support dragonfly reproduction akin to natural ponds

Stormwater ponds are constructed to receive urban runoff and regulate flooding of built areas. As a result, they can be more stressful habitats for aquatic organisms than natural ponds. Adult dragonflies are known to frequent stormwater management ponds in cities, but whether they successfully reproduce in these artificial systems is not clear. This study compared the reproductive potential of dragonflies in stormwater ponds across a temperate metropolitan area through weekly collections of exuviae at stormwater ponds and natural (reference) ponds. We hypothesized that stormwater ponds were poor habitats for dragonfly reproduction (in comparison to natural ponds) because of the typically negative effects of urbanization on wildlife. With respect to dragonfly reproduction, we therefore predicted: (1) lower breeding recruitment, (2) fewer habitat specialists, and (3) greater homogenization of breeding assemblages at stormwater ponds. However, we did not find a significant difference in the number of species and abundance of exuviae between stormwater and natural ponds. Stormwater ponds also supported similar numbers of habitat specialists as natural ponds. Furthermore, we did not find evidence of greater biotic homogenization across stormwater ponds as species composition was similar between both pond types. These results indicate that stormwater ponds can support the reproductive success of a diverse community of dragonflies.

Landscape, demographic, and dispersal parameters influence the spread and establishment of an aquatic biological invasion

AbstractHuman‐mediated species introductions are contributing to the biotic homogenization of global flora and fauna. Despite extensive research, we lack simple methods of predicting how and where an introduced species will spread and establish, particularly in species with complex life histories in aquatic ecosystems. We predict that spread can be modeled simply using the characteristics of the invading population, specifically species growth rate and dispersal capacity. In addition, we predict that the establishment of introduced species should be explained by the characteristics of the receiving ecosystem. Using the brown trout (Salmo trutta) invasion on the Island of Newfoundland as a case study, we fit and test a reaction–diffusion model with brown trout population data collected from the literature. Next, we use statistical models to assess the influence of a suite of abiotic (conductivity, pH, turbidity, calcium), biotic (Atlantic salmon occurrence), and landscape (watershed relief, watershed area, distance to original introduction) variables on brown trout establishment (i.e., presence–absence) patterns. We find that observed coastal spread in Newfoundland is slow (~4.4 km/year), and that it lies on the lower end of the range of predictions made by the reaction–diffusion model parameterized based on the estimates of growth rate and movement from the literature (predicted spread range 1.4 to 92 km/year). Also, we did not find evidence for a relationship between abiotic or biotic variables and brown trout establishment. However, we did observe that landscape variables of the distance to trout introduction point and estuary area may explain establishment patterns along the south coast of Newfoundland. Our results suggest the importance of using population‐specific parameterization and the need to integrate regional landscape factors that are generally applicable across biological invasions (e.g., distance to introduction), and those that are more specific to the ecology of the invader (e.g., estuary area). Our study contextualizes the mechanisms that contribute to a slow invasion by an aquatic species with a complex life history and reveals that future studies need to integrate a variety of methods to elucidate the processes governing invasions.

Connectivity and climate influence diversity–stability relationships across spatial scales in European butterfly metacommunities

AbstractAimAnthropogenic‐driven biodiversity loss can impact ecosystem stability. However, most studies have only evaluated the diversity–stability relationship at the local scale and we do not fully understand which factors stabilize animal populations and communities across scales. Here, we investigate the role of species dispersal ability, climate, spatial distance and different facets of biodiversity on the stability of butterfly populations and communities across multiple spatial scales.LocationPrimarily Western Europe.Time Period2005–2016.Major Taxa StudiedButterflies (Rhopalocera) of Europe.MethodsWe assembled a continent‐wide database of European butterflies' abundance and used Structural Equation Modelling to evaluate the direct and indirect effects of multiple stabilizing mechanisms. In parallel, we tested the effect of dispersal ability on the stability at multiple spatial scales, using a butterfly mobility index as an indicator of dispersal capacity.ResultsRegional stability strongly reflected local stability, which in turn was driven by both taxonomic and functional α‐diversity. Spatial asynchrony was also important for regional stability and it was driven by both functional β‐diversity and metapopulation asynchrony, which in turn increased with spatial distance among communities. We observed a positive effect of temperature on functional α‐diversity and on local stability, whereas precipitation negatively influenced local diversity. Finally, spatial asynchrony contributed more to the regional stability of less mobile species compared to highly mobile ones, indicating that both extrinsic and intrinsic determinants of connectivity impact regional stability indirectly.Main ConclusionsOur results demonstrate the importance of local and regional processes for regional stability. However, the relative contribution of spatial asynchrony and metapopulation asynchrony increases with connectivity loss, especially for less mobile species, indicating that landscape management should be tailored depending on the dispersal capacity of organisms. Both local biodiversity loss and regional biotic homogenization destabilize metacommunities, with potential implications for the reliable provision of ecosystem functions.

Pushing the boundaries: actual and potential distribution of thrushes expanding their ranges in South America

The distribution of a species reflects its ecological adaptability and evolutionary history, which is shaped by the environment and represents a dynamic area subject to anthropogenic environmental change. We used the MaxEnt algorithm to construct ecological niche models for four thrush species within the Turdus genus; T. amaurochalinus, T. chiguanco, T. falcklandii and T. rufiventris. These models were used to predict the potential geographic distributions of these species that are expanding their ranges in South America. Using occurrence records, we estimated currently occupied areas for each species. We also identified suitable habitats and projected possible areas to be colonized by the four species at continental scale. Temperature annual range had the highest influence for T. falcklandii, while human modification was the main variable explaining the distribution of the other three species. The potential distribution area ranged from 2.5 million km2 for T. falcklandii to nearly seven million km2 for T. amaurochalinus. Large proportions of suitable area remain unoccupied by all four species, being 50% for T. amaurochalinus and T. rufiventris, and about 70% for T. chiguanco and T. falcklandii. Anthropogenic disturbances, such as habitat loss and ecosystem transformation, lead to non-random species extinction and biotic homogenization, highlighting the importance of predictive models as valuable tools for informing mitigation policies and conservation strategies. Thrushes are progressively expanding their ranges, and the colonization of new habitats could bring new challenges.

Ungulate herbivores promote beta diversity and drive stochastic plant community assembly by selective defoliation and trampling: From a four‐year simulation experiment

Abstract Ungulate herbivores shape grassland plant communities at multiple scales, ultimately affecting ecosystem function. However, ungulates have complex effects on grasslands, including defoliation, trampling, excreta return and their interactions. Moreover, the effects of ungulate density on grasslands are regulated by these three mechanisms. Nevertheless, how these three mechanisms affect biodiversity at multiple scales and community assembly remains poorly understood. Here, we conducted a 4‐year novel field experiment to disentangle the effects of defoliation, trampling, and excreta return by ungulates on plant community assembly in a temperate grassland in Inner Mongolia, China. This experiment set two different scenarios: moderate ungulate density (Moderate, characterised by selective defoliation and moderate trampling) and high ungulate density (Intense, characterised by non‐selective defoliation and heavy trampling), including different combinations of defoliation, trampling and excreta return in each scenario. We found that defoliation and trampling increased stochasticity in community assembly and promoted alpha and beta diversity under both scenarios. Specifically, defoliation promoted the coexistence of species with multiple resource acquisition strategies (higher functional trait diversity) by reducing interspecific competition; trampling tended to facilitate random species colonisation. Conversely, excreta return favoured grasses, promoting deterministic assembly and impacting species coexistence. Notably, selective defoliation in the Moderate scenario led to a dominance of stochastic processes during community assembly, whereas non‐selective defoliation still did not change the dominance of deterministic processes. Further, communities subject to selective defoliation were insensitive to changes in soil properties caused by trampling and excreta return, maintaining a high‐level beta diversity and the stochastic of community assembly. Synthesis: Our study provides important insights into the mechanisms by which ungulate herbivores influence plant community assembly, suggesting that defoliation and trampling have the potential to drive stochastic processes, while excreta return plays the opposite role. Our study also suggests that selective foraging by ungulates acts as stronger stochastic forces during community assembly compared to non‐selective defoliation. These results imply that considering ungulate feeding preferences and foraging behaviour in grassland management will help prevent biodiversity loss and biotic homogenisation.

Long-term biotic homogenization in the East African Rift System over the last 6 million years of hominin evolution.

Eastern Africa preserves the most complete record of human evolution anywhere in the world but we have little knowledge of how long-term biogeographic dynamics in the region influenced hominin diversity and distributions. Here, we use spatial beta diversity analyses of mammal fossil records from the East African Rift System to reveal long-term biotic homogenization (increasing compositional similarity of faunas) over the last 6 Myr. Late Miocene and Pliocene faunas (~6-3 million years ago (Ma)) were largely composed of endemic species, with the shift towards biotic homogenization after ~3 Ma being driven by the loss of endemic species across functional groups and a growing number of shared grazing species. This major biogeographic transition closely tracks the regional expansion of grass-dominated ecosystems. Although grazers exhibit low beta diversity in open environments of the Early Pleistocene, the high beta diversity of Mio-Pliocene browsers and frugivores occurred in the context of extensive woody vegetation. We identify other key aspects of the Late Cenozoic biogeographic development of eastern Africa, their likely drivers and place the hominin fossil record in this context. Because hominins were undoubtedly influenced by many of the same factors as other eastern African mammals, this provides a new perspective on the links between environmental and human evolutionary histories.

Has climate change over the last ten years caused a banalisation of diatom communities in Cypriot streams?

To unveil possible changes in diatom communities in Cypriot streams over the last ten years or so, we selected samples from the years 2020, 2021, and 2022 for the “recent” dataset (N = 119) and samples from the years 2010 and 2011 for the “historical” dataset (N = 108). Biotic homogenization has become a truly global phenomenon. Here we show that, over the last ten years, in response to increased water temperature, conductivity, and discharge variability due to climate-change, Cypriot stream diatom communities include a higher number of trivial (= widespread, tolerant, and opportunistic), aerial, and thermophilic species, have reduced β-diversity and increased nestedness. Moreover, IndVal analysis shows that indicator species from the historical dataset were characteristic, often relatively rare species, while the indicators of the recent dataset were a group of typical trivial, eutraphentic, and thermophilic species. As is almost always the case, the diatom communities we studied were subjected to multiple stressors, often affecting them in opposite ways. Besides the increase in trivial species, the reduction in β-diversity, and the rise in nestedness mentioned above, the diatom assemblages we studied also showed an increase in α-diversity that could be due to a moderate reduction in nutrients in several sites. High-ecological-integrity ecosystems, such as springs, waterfalls, and dripping rock-walls, in particular springs that were shown to be excellent hydrologic refugia in climates heavily affected by climate change, and the stream sites close to them should be carefully protected, as they can be refugia for sensitive and characteristic species that can recolonize the adjacent streams after adverse climatic events.

Impact of a ‘reverse keystone species’ on the temporal dynamics of bird communities in Australia

Interference competition by noisy miners Manorina melanocephala threatens small woodland bird communities in the highly modified agricultural landscapes of southeastern Australia. Noisy miners aggressively exclude small passerines from their territories promoting the biotic homogenization of communities. Here, we addressed the impact of this native species on the temporal dynamics of bird communities over a 7-years period (2010/2011–2016/2017). We explored the differences in community dynamic metrics (synchrony, stability, rate of change) between assemblages with and without presence of noisy miners. We also tested for differences in temporal beta diversity between the two categories of community. We first applied a multi-species abundance model to account for the imperfect observation process and uncertainty in species abundance. Yearly variation in species occurrence (but not in abundance) was higher in communities with presence of noisy miners, suggesting that this hyper-aggressive competitor excludes rare species and contributes to increased level of temporal turnover. In line with this, species loss was also significantly higher in communities with this competitor. These communities are also subject to greater variation in composition across years despite consisting of a smaller number of species in comparison to those without noisy miners. This translates into instability, where communities with noisy miners showed a loose equilibrium and generally exhibited little directional change. Our findings suggest that in the short term, noisy miners act as a filter, resulting in a predictable homogenization of species assemblages (small-bodied species are excluded while large-bodied ones are favored) in their presence. However, over a longer period, this species contributes to increased community instability. This study adds to the growing body of literature showing evidence of the ecological relevance that the impact of noisy miners can have on Australian woodlands.

Impacts of climate change in taxonomic, phylogenetic and functional diversity in snakes in largest dry forest ecoregion, the Gran Chaco

The impacts of anthropogenic activities have significantly contributed to recent and future climate changes worldwide. The future effects of climate change on biodiversity have been intensively studied globally over the past two decades. Currently, dry ecoregions are among the most threatened ecosystems in the world. In South America, three such seasonal dry ecoregions stand out: the Cerrado, Caatinga, and the Gran Chaco. Among these, the Chaco has experienced high deforestation rates and landscape degradation over the last decade, making it a top priority for conservation efforts. In this study, we employed ecological niche modeling to estimate the present and future distribution of snakes in the Chaco region. Our goal was to assess how snake diversity will change with projected climate changes across this geographic area. Our findings suggest that snake assemblages in the Chaco will undergo significant changes under future climatic conditions, with a clear trend toward biotic homogenization of the ecoregion and a decrease in species richness. These negative changes will likely extend to the protected areas within the Chaco, resulting in biotic homogenization and a loss of species richness.

Hierarchical diversity partitioning of microscopic epibiont community on intertidal molluscan shells and inert surfaces over three geographic regions in Japan.

Microscopic epibionts on molluscan shells are a component of the biodiversity of intertidal coastal areas. Because molluscan shells are discrete habitats for the epibiont community, and the molluscan basibionts belong to the local community, epibiont diversity can be evaluated hierarchically by basibiont categories including species. To evaluate the structure of epibiont diversity and effects of taxonomic resolution on the evaluation, epibionts on molluscan shells and inert surfaces were investigated at three geographically distant sites in Japan. In total, 94 species-level taxonomic units of epibionts were obtained from 31 basibiont molluscan species and inert surfaces (plastics and rock chips). The density and the species richness at the site of the lowest latitude were significantly lower than those at the other sites. The epibiont community differed between the three sites, although the major portion of the epibionts were diatoms. Between-site diversity contributed most of the total diversity of the species richness and Simpson diversity in the five levels of the hierarchical partitioning: sample (individual basibiont), basibiont species (molluscan species), surface group (bivalves, chitons + limpets, and globose gastropods), site, and the total. The taxonomic resolution did not markedly affect the variability of communities between the three sites, although the taxon richness was reduced to 51 in the genus-level analysis. The lower taxonomic resolution (genus level); however, increased the contribution of the within-sample and decreased the contribution of β diversities at the higher hierarchies, leading to a possible overestimation of biotic homogenization between the communities.

Impact of a run-of-river dam in an Amazonian large river on the spatial and temporal patterns of phytoplankton beta diversity

Human activities degrade aquatic ecosystems and diminish biodiversity. Dams have a direct impact on river environments, notably affecting aquatic communities like phytoplankton. We investigated the impact of the damming of an Amazonian River on the composition and spatial and temporal beta diversity of phytoplankton, from October 2009 to July 2017. Also sought to understand how the contribution values for beta diversity (LCBD) changed over time. To achieve this, we performed a PERMANOVA to identify changes in phytoplankton composition between dam phases. Also calculated temporal beta diversity at local and regional scales and regressed these values over time to identify possible biotic homogenization and unidirectional changes in the community. Finally, we calculated the LCBD values of each site over time and regressed these values on species richness, environmental heterogeneity, and the site distance to the dam. We verified that the composition of the phytoplankton changed between the phases of the dam. The impact of time on both local and regional beta diversity was observable, particularly in the tributaries. This was attributed to shifts in community composition from the onset of the study to its conclusion, as well as to biotic homogenization detected in sites closest to the dam. These sites became similar over time, contributing less to beta diversity. This change was related to an increase in species richness. Therefore, it was possible to verify that the construction of the reservoir impacted the diversity of the community over time and that the tributaries backwaters were more affected than the main channel.