Unraveling habitat-driven shifts in alpha, beta, and gamma diversity of hummingbirds and their floral resource.

Background: Biodiversity, crucial for understanding ecosystems, encompasses species richness, composition, and distribution. Ecological and environmental factors, such as habitat type, resource availability, and climate conditions, play pivotal roles in shaping species diversity within and among communities, categorized into alpha (within habitat), beta (between habitats), and gamma (total regional) diversity. Hummingbird communities are influenced by habitat, elevation, and seasonality, making them an ideal system for studying these diversities, shedding light on mutualistic community dynamics and conservation strategies. Methods: Over a year-long period, monthly surveys were conducted to record hummingbird species and their visited flowering plants across four habitat types (oak forest, juniper forest, pine forest, and xerophytic shrubland) in Tlaxcala, Mexico. Three locations per habitat type were selected based on conservation status and distance from urban areas. True diversity measures were used to assess alpha, beta, and gamma diversity of hummingbirds and their floral resources. Environmental factors such as altitude and bioclimatic variables were explored for their influence on beta diversity. Results: For flowering plants, gamma diversity encompassed 34 species, with oak forests exhibiting the highest richness, while xerophytic shrublands had the highest alpha diversity. In contrast, for hummingbirds, 11 species comprised the gamma diversity, with xerophytic shrublands having the highest richness and alpha diversity. Our data reveal high heterogeneity in species abundance among habitats. Notably, certain floral resources like Loeselia mexicana and Bouvardia ternifolia emerge as key species in multiple habitats, while hummingbirds such as Basilinna leucotis, Selasphorus platycercus, and Calothorax lucifer exhibit varying levels of abundance and habitat preferences. Beta diversity analyses unveil habitat-specific patterns, with species turnover predominantly driving dissimilarity in composition. Moreover, our study explores the relationships between these diversity components and environmental factors such as altitude and climate variables. Climate variables, in particular, emerge as significant contributors to dissimilarity in floral resource and hummingbird communities, highlighting the influence of environmental conditions on species distribution. Conclusions: Our results shed light on the complex dynamics of hummingbird-flower mutualistic communities within diverse habitats and underscore the importance of understanding how habitat-driven shifts impact alpha, beta, and gamma diversity. Such insights are crucial for conservation strategies aimed at preserving the delicate ecological relationships that underpin biodiversity in these communities.

Simplified fish larval supply in coastal areas after a dam burst in Brazil.

Coastal and estuarine systems play an important role in the maintenance of marine biodiversity, providing nursery, feeding, developmental and reproductive areas for terrestrial and aquatic species. The Fundão dam collapse is considered one of the biggest environmental disasters in Brazil, causing great social, economic and ecological damage in the affected areas. In our study, we used beta diversity and its components as a tool to monitor the spatio-temporal variation of fish larvae in four marine areas adjacent to the Doce River. The results show that the four areas undergo different spatio-temporal dynamics, with the composition of fish larvae in the Doce being simplified in the last years after the dam burst, compared to the other adjacent marine areas. In addition, turbidity is an important factor that has caused the homogenization of the larval composition of the Doce, demonstrating that mud resuspension events can cause a decrease in diversity and also suggesting the toxicity of the mud composition. The change from negative to positive additive and colonizing components in recent years suggests a slight recovery of diversity in the Doce compared to other marine areas. Finally, we have shown that some species may be tolerant to the impact, but with probable behavioral, energetic and physiological costs, which justifies the constant monitoring of these areas.

Hydroids from a reef system under the influence of the Amazon River plume, Brazil.

The Amazon Reef System (ARS) is one of the most important shallow and mesophotic reef ecosystems in the South Atlantic Ocean. The ARS consists mainly of extensive beds of calcareous algae interspersed by assemblages of octocorals and sponges. The enormous freshwater discharge from the Amazon River forms a plume along the extensive Amazon continental shelf, for which the hydroid community is still largely unknown. The aim of this study is to document the diversity and distribution of hydroids from the ARS, as well as to infer the influence of the plume on species composition in the different zones. Samples were collected at ninety-six stations between 15 and 240 m deep on the Amazon shelf. A total of 37 species were recorded in the studied area. Hydroid assemblages are richer in zones under lower river plume influence, and species composition differs significantly between zones with and without plume influence (PERMANOVA, p = 0.0025). The dissolved oxygen and nitrate ranges were the environmental variables significantly correlated with the hydroid distribution. This study is the first surveying the hydroid species composition and richness in the ARS, highlighting the presence of a typical reef biota and that further faunal studies in underexplored areas of the Atlantic should reveal the distribution of many poorly known hydroids species.

Searching for common patterns in parasite ecology: species and host contributions to beta-diversity in helminths of South African ungulates and fleas of South American rodents.

We searched for common patterns in parasite ecology by investigating species and host contributions to the beta-diversity of infracommunities (=assemblages of parasites harboured by a host individual) in helminths of three species of South African ungulates and fleas of 11 species of South American rodents, assuming that a comparison of patterns in distinctly different parasites and hosts would allow us to judge the generality or, at least, commonness of these patterns. We used data on species' composition and numbers of parasites and asked whether (i) parasite species' attributes (life cycle, transmission mode, and host specificity in helminths; possession of sclerotized combs, microhabitat preference, and host specificity in fleas) or their population structure (mean abundance and/or prevalence) and (ii) host characteristics (sex and age) affect parasite and host species' contributions to parasite beta-diversity (SCBD and HCBD, respectively). We found that parasite species' morphological and ecological attributes were mostly not associated with their SCBD. In contrast, parasite SCBD, in both ungulates and rodents, significantly increased with either parasite mean abundance or prevalence or both. The effect of host characteristics on HCBD was detected in a few hosts only. In general, parasite infracommunities' beta-diversity appeared to be driven by variation in parasite species rather than the uniqueness of the assemblages harboured by individual hosts. We conclude that some ecological patterns (such as the relationships between SCBD and parasite abundance/prevalence) appear to be common and do not differ between different host-parasite associations in different geographic regions, whereas other patterns (the relationships between SCBD and parasite species' attributes) are contingent and depend on parasite and host identities.

Variations in the Odonata Assemblages: How Do the Dry Season and Water Bodies Influence Them?

Diverse abiotic and biotic factors drive the ecological variation of communities across spatial and temporal dimensions. Within the Amazonian landscape, various freshwater environments exhibit distinct physicochemical characteristics. Thus, our study delved into the fluctuations of Odonata assemblages amidst distinct water bodies within Amazonia, encompassing two distinct climatic seasons. Comparative analysis was conducted on Odonata species diversity and assemblage composition across a blackwater pond, a lake, and a stream, spanning the initiation and culmination of the dry season in the southwestern Amazon region in Peru. Our methodology involved capturing adult Odonata using entomological nets on three separate occasions between 11:00 and 14:00 h for each water body in May (beginning of the dry season) and October (end of the dry season) of 2018. We also evaluated the influence of temperature, precipitation, and percent cloud cover on the abundance and richness of adult Odonata. Species richness and composition differed among the three water bodies in both periods of the dry season. No effect of the dry season periods on species richness and abundance was observed. However, except in the oxbow lake, the more abundant species were substituted to the end of the dry season. Our study highlights the influence of water body types on Odonata species diversity and composition. The effects of the sampling period during the dry season may not be immediately apparent in conventional diversity metrics, such as species richness and abundance. Instead, its effects manifest predominantly in the relative abundance of the species that compose these assemblages.

Fish diversity of Colombian Andes-Amazon streams at the end of conflict is a reference for conservation before increased land use.

Reference conditions are difficult to find in the Anthropocene but essential for effective biodiversity conservation. Aquatic ecosystems in the Andes-Amazon transition zone of Colombia are now at high risk due to expanded human activities after peace agreements in 2016 ended armed conflict because lands formerly controlled by FARC and other armed groups are now prone to agricultural and urban expansion. Particularly, expanding human land use may reduce fish diversity across the altitudinal gradient, especially in the premontane streams (i.e., <500 m a.s.l.) because lands are more amenable to human use than at greater altitudes. We evaluated fish α-diversity (measured as species richness, total abundance, and effective species number) and ß-diversity (spatial and temporal) in 12 sites over 8 years bracketing the end of armed conflict. All α-diversity and ß-diversity analyses were evaluated relative to categorical altitude (< or >500 m) and continuous altitude. Strong differences in fish community structure among sites occurred as a function of altitude. Fish communities exhibit altitudinal biodiversity gradients that are consistent in space and time, and that need to be accounted for conservation and management considerations. Our results provide a reference to identify short- and long-term changes due to impending human land use at a critical moment for the conservation of tropical fish diversity. Similar studies in other areas of the upper Amazon Basin are needed to evaluate effects of subsequent human activities on diversity patterns and our study area to compare to reference conditions reported here.

Upstream cascade reservoirs drive temporal beta diversity increases through species loss in a dammed river.

Changes in the biodiversity of aquatic environments over time and space due to human activities are a topic of theoretical and conservational interest in ecology. Thus, variation in taxonomic beta diversity of the planktonic ciliates community was investigated along a temporal and spatial gradient in two subsystems of a Neotropical floodplain, one impacted by dams (Paraná) and the other free of them along its course (Ivinhema). For the spatial analysis, the Paraná subsystem did not show a significant decrease in beta diversity, presenting a pattern like that observed for the Ivinhema subsystem. Therefore, biotic homogenization was not observed for the ciliate's community downstream of the dams. It was noted that there was a fluctuation in the relevance of the components of beta diversity, regardless of the subsystem analyzed. For the temporal analysis there was a significant change in species composition from the first to the last year investigated, essentially for the subsystem impacted by dams, and that this was determined mainly by species loss. Although spatial beta diversity remained high without a clear process of biotic homogenization, dams promoted remarkable changes in ciliate species composition over the years mainly by continuous loss of species.

Interdecadal changes in ichthyofauna in a tropical bay with high anthropogenic influences: functional stability despite turnover predominance.

Functional characteristics of species are of great importance for understanding their roles in ecosystems and can be used to detect long-term chances in the environment. We evaluated temporal changes (1983-1985 and 2017-2019) in taxonomic and functional indices of the fish fauna in shallow areas of a tropical bay heavily impacted by anthropogenic activities in recent decades. The hypothesis that functional indices change over time as a result of environmental degradation was tested. Our results showed a significant decrease in species richness and abundance over time, and in functional richness, while others functional diversity indices (divergency, evenness, and originality) remained stable. Thirteen functional groups were detected, some of which contained only one species, raising concerns about the loss of ecosystem functions due to ongoing changes. We also observed an increase in beta diversity over time, which may be the result of a decrease in local richness without leading to regional extinctions. Turnover was the most important process in structuring the fish fauna at the evaluated time scale. The relative stability of the functional structure and the higher levels of turnover seem to be related to the dominance of functional groups, within which species replace each other according to their responses to environmental filters that select for specific functional traits. Incorporating functional diversity indices and beta diversity variations in the fish community helped to enhance the existing information about this coastal system by offering improved estimates of biological diversity through diverse approaches. The predominance of turnover identified in the preset study suggests a dynamic and fluctuating species composition within the habitat. In this sense, habitat preservation should prioritize the protection of diverse habitats to accommodate a broad spectrum of species.

Submarine outfall and new sewage treatment plant modulate the response of intertidal benthic communities in a SW Atlantic area.

Spatio-temporal responses of the intertidal macrobenthic community to the effects of a submarine outfall (SO) and a new sewage treatment plant (EDAR) were evaluated, analyzing changes in macrofaunal assemblages and community structure. Study was conducted in a SW Atlantic coastal area in 4 stages: BSO (Before the SO), Du (During the construction of the SO), ASO (After the SO start-up) and AEDAR (After the treatment plant start-up). Boccardia proboscidea and Brachidontes rodriguezii contributed most to the differences between all stages at the site nearest to the discharge point. Number of individuals was highest at BSO and Du. Richness and diversity were lowest at the BSO and highest at the Du. Furthermore, the richness decreased slightly, and the diversity increased at AEDAR. Evenness was highest at the BSO and AEDAR. The nestedness was the dominant process driving the differences between the BSO stage community and the rest of the stages. SO affects the composition and structure of the intertidal macrobenthic community near the outfall area, as organic matter discharge further offshore favour the development of a more diverse intertidal community, including species sensitive to organic enrichment.

Distribution of diversity of fishes in an Andean fluvial network

Introduction: The distribution of freshwater fishes in the Colombian Andes results from the interaction between historical and recent factors. Currently, the Andean landscape is facing rapid transformation processes. However, the knowledge regarding species distribution and environmental requirements is advancing slower than the transformations underway in the fluvial networks. Objective: To understand the conformation of the fish assemblage in the middle and lower Cauca River basin, considering the local environmental context before the construction of the Ituango Dam, and quantifying β diversity and its two components (turnover and nestedness) amongst local fish communities. Methods: 58 localities were monitored during nine years (between February 2010 and November 2018), the period before the dam's operation. The species richness (α-diversity), species turnover (β-diversity), and assemblage composition were estimated for the given localities. Results: 114 species were recorded, representing ~ 49 % of the total richness of known species for the Magdalena basin. The richness distribution showed that the number of species varies among the aquatic environments. Swamps presented the most significant number of species, followed by the Cauca River, while streams had the lowest values of richness. The spatial analyses of β-diversity revealed a high variation component in the study area due to species replacement between the aquatic environments. Conclusions: The implementation of long-term monitoring allowed us to recognize that the Cauca River basin conserves a great variety of species-rich environments. The species turnover indicates a high proportion of endemism or multiple sites with unique species. Finally, our study will serve as a baseline to verify, over time, whether the dam's construction is associated with essential changes in the structure of fish communities.

Introducción: La distribución de los peces de agua dulce en los Andes colombianos es el resultado de la interacción entre factores históricos y recientes. Actualmente, el paisaje Andino enfrenta procesos de rápida transformación. Sin embargo, el conocimiento sobre la distribución de las especies y sus requerimientos ambientales no avanza tan rápido como las transformaciones en curso en las redes fluviales. Objetivo: Comprender la conformación del ensamble de peces en la cuenca media y baja del río Cauca, considerando el contexto ambiental local antes de la construcción de la represa de Ituango, y cuantificar la diversidad beta y sus dos componentes (recambio y anidamiento) entre las comunidades de peces locales. Métodos: Se analizaron 58 localidades durante nueve años (entre febrero 2010 y noviembre 2018), período previo a la operación de la represa. La riqueza de especies (diversidad α), el recambio de especies (diversidad β) y la composición del conjunto se estimaron para las localidades dadas. Resultados: Se registraron 114 especies, que representan ~ 49 % de la riqueza total de especies conocidas para la cuenca del Magdalena. La distribución de la riqueza mostró que el número de especies varía entre los ambientes acuáticos. Las ciénagas presentaron el mayor número de especies, seguidas por el río Cauca, mientras que las quebradas presentaron los valores más bajos de riqueza. Los análisis espaciales de la diversidad β revelaron un alto componente de variación en el área de estudio debido al reemplazo de especies entre los ambientes acuáticos. Conclusiones: La implementación del monitoreo a largo plazo permitió reconocer que la cuenca del río Cauca conserva una gran variedad de ambientes ricos en especies. El recambio de especies indica una alta proporción de endemismo o múltiples sitios con especies únicas. Finalmente, nuestro estudio servirá como línea base para verificar, con el tiempo, si la construcción de la represa está asociada con cambios esenciales en la estructura de las comunidades de peces.

Climate change should drive mammal defaunation in tropical dry forests.

Human-induced climate change has intensified negative impacts on socioeconomic factors, the environment, and biodiversity, including changes in rainfall patterns and an increase in global average temperatures. Drylands are particularly at risk, with projections suggesting they will become hotter, drier, and less suitable for a significant portion of their species, potentially leading to mammal defaunation. We use ecological niche modelling and community ecology biodiversity metrics to examine potential geographical range shifts of non-volant mammal species in the largest Neotropical dryland, the Caatinga, and evaluate impacts of climate change on mammal assemblages. According to projections, 85% of the mammal species will lose suitable habitats, with one quarter of species projected to completely lose suitable habitats by 2060. This will result in a decrease in species richness for more than 90% of assemblages and an increase in compositional similarity to nearby assemblages (i.e., reduction in spatial beta diversity) for 70% of the assemblages. Small-sized mammals will be the most impacted and lose most of their suitable habitats, especially in highlands. The scenario is even worse in the eastern half of Caatinga where habitat destruction already prevails, compounding the threats faced by species there. While species-specific responses can vary with respect to dispersal, behavior, and energy requirements, our findings indicate that climate change can drive mammal assemblages to biotic homogenization and species loss, with drastic changes in assemblage trophic structure. For successful long-term socioenvironmental policy and conservation planning, it is critical that findings from biodiversity forecasts are considered.

Effects of hydrogeochemistry on the microbial ecology of terrestrial hot springs.

Temperature, pH, and hydrochemistry of terrestrial hot springs play a critical role in shaping thermal microbial communities. However, the interactions of biotic and abiotic factors at this terrestrial-aquatic interface are still not well understood on a global scale, and the question of how underground events influence microbial communities remains open. To answer this, 11 new samples obtained from the El Tatio geothermal field were analyzed by 16S rRNA amplicon sequencing (V4 region), along with 191 samples from previous publications obtained from the Taupo Volcanic Zone, the Yellowstone Plateau Volcanic Field, and the Eastern Tibetan Plateau, with their temperature, pH, and major ion concentration. Microbial alpha diversity was lower in acid-sulfate waters, and no significant correlations were found with temperature. However, moderate correlations were observed between chemical parameters such as pH (mostly constrained to temperatures below 70°C), SO4 2- and abundances of members of the phyla Armatimonadota, Deinococcota, Chloroflexota, Campilobacterota, and Thermoplasmatota. pH and SO4 2- gradients were explained by phase separation of sulfur-rich hydrothermal fluids and oxidation of reduced sulfur in the steam phase, which were identified as key processes shaping these communities. Ordination and permutational analysis of variance showed that temperature, pH, and major element hydrochemistry explain only 24% of the microbial community structure. Therefore, most of the variance remained unexplained, suggesting that other environmental or biotic factors are also involved and highlighting the environmental complexity of the ecosystem and its great potential to test niche theory ecological associated questions. IMPORTANCE This is the first approach to investigate whether geothermal processes could have an influence on the ecology of thermal microbial communities on a global scale. In addition to temperature and pH, microbial communities are structured by sulfate concentrations, which depends on the tectono-magmatic settings (such as the depth of magmatic chambers) and the local settings (such as the availability of a confining layer separating NaCl waters from steam after phase separation) and the possibility of mixing with more diluted fluids. Comparison of microbial communities from different geothermal areas by homogeneous sequence processing showed that no significant geographic distance decay was detected on the microbial communities according to Bray-Curtis, Jaccard, unweighted, and weighted Unifrac similarity/dissimilarity indices. Instead, an ancient potential divergence in the same taxonomic groups is suggested between globally distant thermal zones.

Biogeographic regionalization of human infectious diseases in Brazil based on geographically explicit data.

OBJECTIVE: Biogeographic regionalization represents abstractions of the organisation of life on Earth, and can provide a large-scaled framework for health management and planning. We aimed at determining a biogeographic regionalization for human infectious diseases in Brazil, and at investigating non-mutually exclusive hypotheses predicting the observed regions. METHODS: Based on the spatial distributions of 12 infectious diseases with mandatory notification (SINAN database, 2007-2020, n = 15,839), we identified regions through a clustering procedure based on beta-diversity turnover. The analysis was repeated 1000 times by randomly shuffling the rows (0.5° cells) in the original matrix. We evaluated the relative importance of variables using multinomial logistic regression models: contemporary climate (temperature and precipitation), human activity (population density and geographic accessibility), land cover (11 classes), and the full model (all variables). We refined the geographic boundaries of each cluster by polygonising their kernel densities to identify clusters' core zones. RESULTS: The two-cluster solution showed the best correspondence between disease ranges and clusters geographic limits. The largest cluster occurred with more density in the central and northeastern regions, while the smaller and complementary cluster occurred in the south and southeastern region. The best model for explaining the regionalization was the full model, supporting the 'complex association hypothesis'. The heatmap showed a NE-S directional display of the cluster's densities, and core zones showed geographic correspondence with tropical + arid (NE) versus temperate (S) climates. CONCLUSION: Our findings indicate that there is a discernible latitudinal pattern in the turnover of disease in Brazil, and this phenomenon is associated with an intricate interplay between contemporary climate, population activity, and land cover. This generalised biogeographic pattern may offer the earliest insights into the geographic arrangement of diseases in the country. We suggested that the latitudinal pattern could be adopted as a nationwide framework for geographic vaccine allocation.

What are the Andean Colombian anurans? Empirical regionalization proposals vs. observed patterns of compositional dissimilarity.

Background: Defining Andean anurans through their altitudinal limits has been a common practice in species lists, studies of responses to climate change among others, especially in the northern Andes. At least three proposals to differentiate Andean anurans from lowland anurans through elevation and at least one to differentiate Andean anurans from high mountain anurans have been formulated. However, the most frequently used altitudinal limits are not based on theoretical or numerical support, but on observations or practical definitions. Additionally, these proposals have been applied equally to different portions of the Andes, ignoring the fact that even between slopes of the same mountain, environmental conditions (and therefore the distribution of species) may differ. The objective of this work was to evaluate the concordance between the altitudinal distribution of anurans in the Colombian Andes and four different altitudinal delimitation proposals. Methods: We constructed our study area in a manner that allowed us to include species from the Andean region (as traditionally defined) and adjacent lowlands, because if the boundaries criteria were applied they would separate the species of the latter by themselves. We divided the study area into eight entities according to the watershed and the course of the most important rivers. We conducted a bibliographic search for all anurans in the cordilleras and inter-Andean valleys of Colombia and complemented the search with information on anurans for the region available in the GBIF. After curing the species distribution points, we generated elevation bands of 200 m amplitude for both the study area and for each Andean entity. Subsequently, we performed a cluster analysis to evaluate the grouping of the elevation bands according to their species composition. Results: In none of the cases (neither for the entire study area nor for any of the entities) we found a correspondence of any of the traditionally used boundaries and the altitudinal distribution of Anurans in the Andean region of Colombia. Instead, on average, the altitudinal delimitation proposals arbitrarily spanned the altitudinal distribution of about one third of the species distributed in the study area. Conclusions: We suggest that, although, based on our results, some Andean entities can be divided according to the altitudinal composition of the species that occur in them, we did not find any results that support the idea of a generalizable altitudinal limit for the Colombian Andes. Thus, to avoid biases in studies that may later be used by decision makers, the selection of anuran species in studies in the Colombian Andes should be based on biogeographic, phylogenetic or natural history criteria and not on altitudinal limits as they have been used.

Environmental heterogeneity of a tropical river-to-sea continuum and its relationship with structure and phytoplankton dynamics - Lençóis Maranhenses National Park.

ß-diversity and functional traits of phytoplankton indicators associated with environmental heterogeneity were investigated as environmental quality descriptors in coastal (CS), estuarine (ES), and limnetic (LS) sectors in a tropical river-to-sea ecosystem. Results showed that environmental heterogeneity was marked by spatial differences, contributing to biological heterogeneity. Sporadic and recurrent blooms were associated with environmental spatiotemporal variations and reflected a reduction in ES α-diversity. Salinity acted as an environmental filter that governed the structure and dynamics of the community. The spatial heterogeneity and high turnover of phytoplankton resulted in reliable bioindicators selection. Colonial, bloom-forming and harmful species were associated with highly suspended particulate matter (SPM) because these species are better adapted to these conditions. Species small in size were associated with high concentrations of silicate and chlorophyll-a in the ES because of the occurrence of diatom recurrent blooms. Most flagellates indicators genera have bloom-forming potential. Integrating morphofunctional with taxonomic approaches enabled detailed observations of environmental filters, supporting the selection of priority species and areas for introducing biodiversity monitoring programs and conservation in tropical ecosystems.

Resident species, not immigrants, drive reorganization of estuarine fish assemblages in response to warming.

Climate change is reshaping biological communities, as species track environmental temperature. Assemblage reorganization is underpinned by shifts in species abundance and distribution, but studies often focus on documenting compositional turnover. As a consequence, phenomena such as the tropicalization of temperate communities have been widely associated with increased occupancy of warm-affinity species. Abundance-weighted change in thermal affinity can be tracked with the Community Temperature Index (CTI), and decomposed into four processes: tropicalization (increasing warm-affinity), borealization (increasing cold-affinity), deborealization (decreasing cold-affinity), and detropicalization (decreasing warm-affinity). Further evaluation of these processes according to species persistence (i.e., immigrant, emigrant, and resident) may provide insights on whether novel communities emerge primarily from local shifts in species abundance or distribution. Using long-term data on fish assemblages undergoing climate change's effects across 19 temperate estuaries surveyed for at least 20 years, we hypothesized (1) deborealization is the main process reshaping communities under climate change, and (2) the contribution of resident species to processes reshaping communities surpass the ones from immigrants and emigrants. Community dissimilarity was calculated through the Temporal Beta Index (TBI), which was further decomposed into species and individual losses and gains. These values were then used as effect sizes in the meta-analyses performed to detect systematic trends in assemblage reorganization in response to climate change. We also calculated CTI and the strength of temperature-related processes for resident, immigrant and emigrant species. Species and individual gains outweighed losses in estuaries. Temperature was correlated with changes in species abundance, but not occurrence. Fish abundance decreased with warming, and initially cooler estuaries gained more fish than warmer ones. Novel communities were shaped by a variety of processes, but mainly tropicalization. Assemblage reorganization was primarily driven by shifts in abundance of resident species with distinct thermal affinities, while contributions of arriving and exiting species played a secondary role. These findings reveal that novel communities are drawn primarily from the local species pool, due to changes in climate-related drivers that favor distinct resident species.

Foundation species canopies affect understory beta diversity differently depending on species mobility.

Beta diversity measures the spatial variation in species composition. Because it influences several community attributes, studies are increasingly investigating its drivers. Spatial environmental heterogeneity is a major determinant of beta diversity, but canopy-forming foundation species can locally modify environmental properties. We used intertidal communities dominated by the canopy-forming alga Mazzaella laminarioides as a model system to examine how a foundation species affects spatial environmental heterogeneity and the resulting beta diversity. Since canopies were found to reduce the spatial variation of temperature and desiccation during low tides, we hypothesized that canopies would decrease understory beta diversity, which we tested through a field experiment that contrasted canopy removal with presence treatments over 32 months. The beta diversity of sessile species was always lower under canopies, but canopies never affected the beta diversity of mobile species. The observed responses for sessile species may result from their abundance being more dependent on spatial abiotic variation than for mobile species, which can occur in stressful areas while temporarily foraging or in transit to other areas. These responses may likely apply to other systems exhibiting canopy-forming foundation species hosting sessile and mobile species assemblages.

Blooming plant species diversity patterns in two adjacent Costa Rican highland ecosystems.

The Costa Rican Paramo is a unique ecosystem with high levels of endemism that is geographically isolated from the Andean Paramos. Paramo ecosystems occur above Montane Forests, below the permanent snow level, and their vegetation differs notably from that of adjacent Montane Forests. We compared the composition and beta diversity of blooming plant species using phenological data from functional plant groups (i.e., insect-visited, bird-visited and insect + bird-visited plants) between a Paramo and a Montane Forest site in Costa Rica and analyzed seasonal changes in blooming plant diversity between the rainy and dry seasons. Species richness was higher in the Montane Forest for all plant categories, except for insect-visited plants, which was higher in the Paramo. Beta diversity and blooming plant composition differed between both ecosystems and seasons. Differences in species richness and beta diversity between Paramo and the adjacent Montane Forest are likely the result of dispersal events that occurred during the last glacial period and subsequent isolation, as climate turned to tropical conditions after the Pleistocene, and to stressful abiotic conditions in the Paramo ecosystem that limit species establishment. Differences in blooming plant composition between both ecosystems and seasons are likely attributed to differential effects of climatic cues triggering the flowering events in each ecosystem, but phylogenetic conservatism cannot be discarded. Analyses of species composition and richness based on flowering phenology data are useful to evaluate potential floral resources for floral visitors (insects and birds) and how these resources change spatially and temporarily in endangered ecosystems such as the Paramo.

Biotic homogenization and differentiation of plant communities in tropical and subtropical forests.

Anthropogenic impacts on biodiversity can lead to biotic homogenization (BH) and biotic differentiation (BD). BH is a process of increasing similarity in community composition (including taxonomic, functional, and phylogenetic components), whereas BD is a process of decreasing similarity over space and time. Here, we conducted a systematic review of BH and BD in plant communities in tropical and subtropical forests to identify trends and knowledge gaps. Our bibliometric search in the Web of Science returned 1989 papers, of which 151 matched our criteria and were included in the analysis. The Neotropical region had the largest number of articles, and Brazil was the most represented country with 92 studies. Regarding the type of change, homogenization was more frequent than differentiation (noted in 69.6% of publications). The taxonomic diversity component was measured more often than functional and phylogenetic diversity components. Most studies (75.6%) assessed homogenization and differentiation based on a single observation in time; as opposed to few studies that monitored plant community over multiple years. Forest fragmentation was cited as the main determinant of homogenization and differentiation processes (57.2% of articles). Our results highlight the importance of evaluating community composition over time and more than taxonomic components (i.e., functional and phylogenetic) to advance understanding of homogenization and differentiation. Both processes were scale dependent and not mutually exclusive. As such, future research should consider differentiation as a potential transition phase to homogenization and that potential differences in both processes may depend on the spatial and temporal scale adopted. Understanding the complexity and causes of homogenization and differentiation is essential for biodiversity conservation in a world increasingly affected by anthropogenic disturbances.

Los impactos antropogénicos sobre la biodiversidad pueden resultar en la homogenización y diferenciación biótica. La homogenización biótica consiste en una creciente similitud de la composición comunitaria (incluidos los componentes taxonómicos, funcionales y filogenéticos), mientras que la diferenciación biótica conlleva la disminución en similitudes a lo largo del tiempo y el espacio. En este trabajo realizamos una revisión sistemática de la homogenización y diferenciación biótica en las comunidades vegetales en los bosques tropicales y subtropicales para identificar tendencias y vacíos de conocimiento. Nuestra búsqueda bibliométrica en Web of Science produjo 1989 artículos, de los cuales 151 cumplieron con nuestros criterios y fueron incluidos en el análisis. La región neotropical tuvo el mayor número de artículos y Brasil fue el país más representado con 92 estudios. Con respecto al tipo de cambio, la homogenización fue más frecuente que la diferenciación (reportada en 69.6% de las publicaciones). El componente de diversidad taxonómica se midió más veces que los componentes de diversidad funcional y filogenética. La mayoría de los estudios (75.6%) examinó la homogenización y la diferenciación con base en una sola observación en el tiempo; unos cuantos estudios sí monitorearon las comunidades vegetales a través de varios años. Se citó a la fragmentación del bosque como el principal determinante de los procesos de homogenización y diferenciación (57.2% de los artículos). Nuestros resultados resaltan la importancia de la evaluación de la composición de la comunidad a través del tiempo y más allá de los componentes taxonómicos para propiciar el entendimiento de la homogenización y la diferenciación. Ambos procesos dependieron de la escala y no se excluyeron mutuamente. Por lo tanto, las siguientes investigaciones deberían considerar a la diferenciación como una fase potencial de transición hacia la homogenización y que las posibles diferencias en ambos procesos podrían depender de la escala espacial y temporal aplicada. Son esenciales el entendimiento de la complejidad y las causas de la homogenización y la diferenciación para la conservación de la biodiversidad en un planeta que cada vez se ve más afectado por las perturbaciones antropogénicas.

Influence of abiotic factors on the composition of fish assemblages in the Aracá-Demeni sub-basin of the middle Negro River / Influência de fatores abióticos na composição das assembleias de peixes na sub-bacia Aracá-Demeni no médio rio Negro

Abstract We evaluated the influence of flooding and receding comparison and spatial variation on the composition and structure of fish assemblages in blackwater and clearwater rivers of the Aracá-Demeni sub-basin in the middle Negro River, Amazonas state, Brazil. The collections were carried out during the falling-water period (November 2018) and the rising-water period (April 2019) using gillnets with meshes ranging from 30 to 120mm stretched mesh size. Ecological estimates of richness, equitability, the Shannon-Wiener diversity index, and the Berger-Parker index showed no significant differences between the periods. The composition of the ichthyofauna showed variations between the falling-water and rising-water periods. Beta diversity in the Aracá-Demeni sub-basin is almost completely caused by species substitution, with spatial turnover accounting for most of the estimate. The identification of these patterns and of the responsible factors are fundamental for the definition of conservation strategies, especially in an ecosystem whose dynamics can be influenced by climate change through changes in the intensity of the flood pulse and connectivity.

Resumo Avaliamos a influência da variação entre os períodos de enchente e vazante e espacialmente na composição e estrutura das assembleias de peixes em rios de águas pretas e claras da sub-bacia Aracá-Demeni no médio rio Negro, Amazonas, Brasil. As coletas foram realizadas durante o período de vazante (novembro de 2018) e o período de enchente (abril de 2019) utilizando redes de espera com malhas variando de 30 a 120mm entre nós opostos. As estimativas ecológicas de riqueza, equitabilidade, índice de diversidade de Shannon-Wiener e índice de Berger-Parker não apresentaram diferenças significativas entre os períodos. A composição da ictiofauna apresentou variações entre os períodos de vazante e enchente. A diversidade beta na sub-bacia Aracá-Demeni é quase totalmente causada pela substituição de espécies, com a renovação espacial respondendo pela maior parte da estimativa. A identificação desses padrões e os fatores responsáveis são fundamentais para a definição de estratégias de conservação, principalmente em um ecossistema cuja dinâmica pode ser influenciada pelas mudanças climáticas por meio de mudanças na intensidade do pulso de inundação e conectividade.