RESUMO
Recent decades have witnessed substantial changes in freshwater biodiversity worldwide. Although research has shown that freshwater biodiversity can be shaped by changes in habitat diversity and human-induced pressure, the potentials for interaction between these drivers and freshwater biodiversity at large spatial extents remain unclear. To address these issues, we employed a spatially extensive multitrophic fish and insect database from 3323 stream sites across the United States, to investigate the ability of habitat diversity to modulate the effect of human pressure on the richness and abundance of fish and insects. We found evidence that high levels of habitat diversity were associated with increased richness and abundance of fish and insects (including whole-assemblage and individual trophic guilds). We also show that the effects of human pressure on the richness and abundance of fish and insects tend to become positive at high levels of habitat diversity. Where habitat diversity is low, human pressure strongly reduces insect richness and abundance, whereas these reductions are attenuated at high levels of habitat diversity. Structural equation modeling revealed that human pressure reduced habitat diversity, indirectly negatively affecting the richness and abundance of fish and insects. These findings illustrate that, in addition to promoting greater fish and insect biodiversity, habitat diversity may mitigate the deleterious effects of human pressures on these two stream assemblages. Overall, our study suggests that maintaining high levels of habitat diversity is a useful way to protect freshwater biodiversity from ongoing increases in human pressure. However, if human pressures continue to increase, this will reduce habitat diversity, further threatening stream assemblages.
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Biodiversidade , Ecossistema , Peixes , Insetos , Rios , Animais , Insetos/fisiologia , Peixes/fisiologia , Estados Unidos , Humanos , Atividades HumanasRESUMO
Taylor's power law (TPL) describes the expected range of parameters of the mean-variance scaling relationship and has been extensively used in studies examining temporal variations in abundance. Few studies though have focused on biological and ecological covariates of TPL, while its statistical inherences have been extensively debated. In the present study, we focused on species-specific features (i.e. functional traits) that could be influential to temporal TPL. We combined field surveys of 180 fish species from 972 sites varying from small streams to large rivers with data on 31 ecological traits describing species-specific characteristics related to three main niche dimensions (trophic ecology, life history, and habitat use). For each species, the parameters of temporal TPL (intercept and slope) were estimated from the log-log mean-variance relationships while controlling for spatial dependencies and biological covariates (species richness and evenness). Then, we investigated whether functional traits explained variations in TPL parameters. Differences in TPL parameters among species were explained mostly by life history and environmental determinants, especially TPL slope. Life history was the main determinant of differences in TPL parameters and thereby aggregation patterns, with traits related to body size being the most influential, thus showing a high contrast between small-sized species with short lifespans and large-bodied migratory fishes, even after controlling for phylogenetic resemblances. We found that life history traits, especially those related to body size, mostly affect TPL and, as such, can be determinants of temporal variability of fish populations. We also found that statistical effects and phylogenetic resemblances are embedded in mean-variance relationships for fish, and that environmental drivers can interact with ecological characteristics of species in determining temporal fluctuations in abundance.
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Peixes , Características de História de Vida , Animais , Peixes/fisiologia , Ecossistema , Especificidade da Espécie , Rios , Modelos Biológicos , Água DoceRESUMO
PREMISE: Increasingly complete phylogenies underpin studies in systematics, ecology, and evolution. Myrteae (Myrtaceae), with ~2700 species, is a key component of the exceptionally diverse Neotropical flora, but given its complicated taxonomy, automated assembling of molecular supermatrices from public databases often lead to unreliable topologies due to poor species identification. METHODS: Here, we build a taxonomically verified molecular supermatrix of Neotropical Myrteae by assembling 3909 published and 1004 unpublished sequences from two nuclear and seven plastid molecular markers. We infer a time-calibrated phylogenetic tree that covers 712 species of Myrteae (~28% of the total diversity in the clade) and evaluate geographic and taxonomic gaps in sampling. RESULTS: The tree inferred from the fully concatenated matrix mostly reflects the topology of the plastid data set and there is a moderate to strong incongruence between trees inferred from nuclear and plastid partitions. Large, species-rich genera are still the poorest sampled within the group. Eastern South America is the best-represented area in proportion to its species diversity, while Western Amazon, Mesoamerica, and the Caribbean are the least represented. CONCLUSIONS: We provide a time-calibrated tree that can be more reliably used to address finer-scale eco-evolutionary questions that involve this group in the Neotropics. Gaps to be filled by future studies include improving representation of taxa and areas that remain poorly sampled, investigating causes of conflict between nuclear and plastid partitions, and the role of hybridization and incomplete lineage sorting in relationships that are poorly supported.
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Myrtaceae , Filogenia , Myrtaceae/genética , Myrtaceae/classificação , América do Sul , Plastídeos/genéticaRESUMO
Introduction: Chironomidae (Diptera) is the most widespread and abundant aquatic insect family in freshwater ecosystems. Chironomids are considered good indicators of water quality but are seldom identified at the genus level in broad spatial scale studies. Objective: To identify environmental conditions associated with chironomids in an altitudinal gradient. Methods: We compared ecoregions, river types, and seasons, for chironomids in neotropical streams and rivers (18 river sites; 2014-2018; Yungas rainforest and Western Chaco dry forest, Argentina). We used non-metric multidimensional scaling, dissimilarity, envfit analysis and rank-abundance curves. Results: Chironomid "assemblages''matched both ecoregions and river types. However, ecoregions presented a better fit with species composition. The stenothermal taxa of Orthocladiinae were dominant at high elevations and the eurythermal Chironominae in lowland rivers. Altitude, water temperature and conductivity were important. Seasonal differences were smaller than ecoregional differences. Conclusions: Ecoregions, altitude, water temperature and conductivity correlated with chironomid communities. Orthocladiinae were dominant at high elevations and Chironominae in lowland rivers.
Introducción: Chironomidae (Diptera) es la familia de insectos acuáticos más extendida y abundante en los ecosistemas dulceacuícolas. Los quironómidos se consideran buenos indicadores de la calidad del agua, pero rara vez se identifican a nivel de género en estudios de amplia escala espacial. Objetivo: Identificar las condiciones ambientales asociadas a los quironómidos en un gradiente altitudinal. Métodos: Comparamos ecorregiones, tipos de ríos y estaciones para quironómidos en arroyos y ríos neotropicales (18 sitios en ríos; 2014-2018; en un bosque tropical de Yungas y un bosque seco del Chaco Occidental, Argentina). Utilizamos escalamiento no métrico multidimensional, disimilitud, análisis de envfit y curvas de rango-abundancia. Resultados: Los "ensamblajes''de quironómidos coincidieron tanto con las ecorregiones como con los tipos de ríos. Sin embargo, las ecorregiones presentaron un mejor ajuste con la composición de especies. Los taxones estenotérmicos de Orthocladiinae fueron dominantes en las elevaciones altas y los euritermales de Chironominae en los ríos de las tierras bajas. La altitud, la temperatura del agua y la conductividad fueron importantes. Las diferencias estacionales fueron menores que las diferencias ecorregionales. Conclusiones: las ecorregiones, la altitud, la temperatura del agua y la conductividad se correlacionaron con las comunidades de quironómidos. Orthocladiinae fue dominante en los sitios altos y Chironominae en los ríos de tierras bajas.
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Establishing how environmental gradients and host ecology drive spatial variation in infection rates and diversity of pathogenic organisms is one of the central goals in disease ecology. Here, we identified the predictors of concomitant infection and lineage richness of blood parasites in New Word bird communities. Our multi-level Bayesian models revealed that higher latitudes and elevations played a determinant role in increasing the probability of a bird being co-infected with Leucocytozoon and other haemosporidian parasites. The heterogeneity in both single and co-infection rates was similarly driven by host attributes and temperature, with higher probabilities of infection in heavier migratory host species and at cooler localities. Latitude, elevation, host body mass, migratory behavior, and climate were also predictors of Leucocytozoon lineage richness across the New World avian communities, with decreasing parasite richness at higher elevations, rainy and warmer localities, and in heavier and resident host species. Increased parasite richness was found farther from the equator, confirming a reverse Latitudinal Diversity Gradient pattern for this parasite group. The increased rates of Leucocytozoon co-infection and lineage richness with increased latitude are in opposition with the pervasive assumption that pathogen infection rates and diversity are higher in tropical host communities.
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Doenças das Aves , Coinfecção , Haemosporida , Parasitos , Animais , Coinfecção/veterinária , Teorema de Bayes , Altitude , Doenças das Aves/epidemiologia , Doenças das Aves/parasitologia , Aves , PrevalênciaRESUMO
Bird-plant seed-dispersal networks are structural components of ecosystems. The role of bird species in seed-dispersal networks (from less [peripheral] to more connected [central]), determines the interaction patterns and their ecosystem services. These roles may be driven by morphological and functional traits as well as evolutionary, geographical and environmental properties acting at different spatial extents. It is still unknown if such drivers are equally important in determining species centrality at different network levels, from individual local networks to the global meta-network representing interactions across all local networks. Using 308 networks covering five continents and 11 biogeographical regions, we show that at the global meta-network level species' range size was the most important driver of species centrality, with more central species having larger range sizes, which would facilitate the interaction with a higher number of plants and thus the maintenance of seed-dispersal interactions. At the local network level, body mass was the only driver with a significant effect, implying that local factors related to resource availability are more important at this level of network organisation than those related to broad spatial factors such as range sizes. This could also be related to the mismatch between species-level traits, which do not consider intraspecific variation, and the local networks that can depend on such variation. Taken together, our results show that the drivers determining species centrality are relative to the levels of network organisation, suggesting that prediction of species functional roles in seed-dispersal interactions requires combined local and global approaches.
Las redes de dispersión de semillas entre aves y plantas son componentes estructurales de los ecosistemas. El rol de las especies de aves en estas redes de dispersión de semillas (de menos [periféricas] a más conectadas [centrales]), determina los patrones de interacción y sus servicios ecosistémicos. Estos roles pueden ser impulsados por rasgos morfológicos y funcionales, propiedades evolutivas, geográficas y ambientales que actúan en diferentes extensiones espaciales. Todavía se desconoce si dichos impulsores son igualmente importantes para determinar la centralidad de las especies en diferentes niveles de red, desde redes locales individuales hasta la meta-red global que representa todas las interacciones en las redes locales. Usando 308 redes abarcando cinco continentes y once regiones biogeográficas, mostramos que a nivel de meta-red global, el tamaño de la distribución geográfica de las especies fue el factor más determinante de la centralidad de las especies, con especies más centrales siendo aquellas que tienen distribuciones más grandes, lo que les facilitaría la interacción con un mayor número de plantas y por lo tanto el mantenimiento de las interacciones de dispersión de semillas. A nivel de las redes locales, la masa corporal fue el único impulsor con un efecto significativo, lo que implica que los factores locales relacionados con la disponibilidad de recursos son más importantes en este nivel de organización que los relacionados con factores espaciales amplios, como el tamaño de las distribuciones. Esto también podría estar relacionado con el desajuste entre los rasgos a nivel de especie, que no consideran la variación intraespecífica, y las redes locales que pueden depender de dicha variación. En conjunto, nuestros resultados muestran que los impulsores que determinan la centralidad de las especies en las redes de interacción son relativos a los niveles de organización de la red, lo que sugiere que la predicción de los roles funcionales de las especies en las interacciones de dispersión de semillas requiere enfoques locales y globales combinados.
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Ecossistema , Dispersão de Sementes , Animais , Aves , Sementes , PlantasRESUMO
Land-use and land-cover transitions can affect biodiversity and ecosystem functioning in a myriad of ways, including how energy is transferred within food-webs. Size spectra (i.e. relationships between body size and biomass or abundance) provide a means to assess how food-webs respond to environmental stressors by depicting how energy is transferred from small to larger organisms. Here, we investigated changes in the size spectrum of aquatic macroinvertebrates along a broad land-use intensification gradient (from Atlantic Forest to mechanized agriculture) in 30 Brazilian streams. We expected to find a steeper size spectrum slope and lower total biomass in more disturbed streams due to higher energetic expenditure in physiologically stressful conditions, which has a disproportionate impact on large individuals. As expected, we found that more disturbed streams had fewer small organisms than pristine forest streams, but, surprisingly, they had shallower size spectrum slopes, which indicates that energy might be transferred more efficiently in disturbed streams. Disturbed streams were also less taxonomically diverse, suggesting that the potentially higher energy transfer in these webs might be channelled via a few efficient trophic links. However, because total biomass was higher in pristine streams, these sites still supported a greater number of larger organisms and longer food chains (i.e. larger size range). Our results indicate that land-use intensification decreases ecosystem stability and enhances vulnerability to population extinctions by reducing the possible energetic pathways while enhancing efficiency between the remaining food-web linkages. Our study represents a step forward in understanding how land-use intensification affects trophic interactions and ecosystem functioning in aquatic systems.
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Biodiversidade , Ecossistema , Humanos , Animais , Cadeia Alimentar , Florestas , Biomassa , Rios/química , InvertebradosRESUMO
Despite the increasing plastic discharge into the environment, few articles have dealt with the macroecological implications of microplastics (MPs) bioaccumulation on organisms. We performed a meta-analysis of MPs accumulation in true crabs and pseudocrabs worldwide and made use of macroecotoxicological approaches to know if: I) functional traits influence the bioaccumulation of MPs in the tissues of crabs; II) there is a latitudinal pattern of MPs bioaccumulation; III) there are tissues that can accumulate more MPs; IV) crabs can sort particles according to size, color, shape and type. Our results showed that functional traits influence the accumulation of MPs. Smaller crabs in size and weight and with shorter lifespans tended to exhibit more plastic particles. According to the environment, estuarine crabs from the intertidal and muddy substrates held more MPs. Also, burrowers exhibited significantly more particles in the tissues than omnivorous crabs. Besides, we recorded that crabs from low latitudes tended to exhibit more plastic particles, probably because of the mangroves' location that acts as traps for MPs. Non-human-consumed crabs accumulated significantly more MPs than human-consumed ones. Considering the tissues, gills were prone to accumulate more debris than the digestive tract, but without significant differences. Finally, colorless fibers of 1-5 mm of PA, PP and PET were the predominant characteristics of MPs, suggesting that crabs accumulated denser types but did not sort plastic according to color. These results indicate that functional traits might influence the accumulation of MPs and that there are coastal regions and geographical areas where crabs tend to accumulate more MPs. Analyzing MPs accumulation patterns with macroecological tools can generate information to identify the most affected species and define priorities for monitoring and implementing actions toward reducing plastic use globally.
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Braquiúros , Poluentes Químicos da Água , Animais , Microplásticos/toxicidade , Plásticos/química , Bioacumulação , Monitoramento Ambiental , Poluentes Químicos da Água/análiseRESUMO
The kinetic hypothesis of biodiversity proposes that temperature is the main driver of variation in species richness, given its exponential effect on biological activity and, potentially, on rates of diversification. However, limited support for this hypothesis has been found to date. I tested the fit of this model to the variation of tree-species richness along a continuous latitudinal gradient in the Americas. I found that the kinetic hypothesis accurately predicts the upper bound of the relationship between the inverse of mean annual temperature (1/kT) and the natural logarithm of species richness, at a broad scale. In addition, I found that water availability and the number of days with freezing temperatures explain part of the residual variation of the upper bound model. The finding of the model fitting on the upper bound rather than on the mean values suggest that the kinetic hypothesis is modeling the variation of the potential maximum species richness per unit of temperature. Likewise, the distribution of the residuals of the upper bound model in function of the number of days with freezing temperatures suggest the importance of environmental thresholds rather than gradual variation driving the observable variation in species richness.
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Temperatura Baixa , Árvores , Temperatura , Biodiversidade , ÁguaRESUMO
The movement of plant species across the globe exposes native communities to new species introductions. While introductions are pervasive, two aspects of variability underlie patterns and processes of biological invasions at macroecological scales. First, only a portion of introduced species become invaders capable of substantially impacting ecosystems. Second, species that do become invasive at one location may not be invasive in others; impacts depend on invader abundance and recipient species and conditions. Accounting for these phenomena is essential to accurately understand the patterns of plant invasion and explain the idiosyncratic results reflected in the literature on biological invasions. The lack of community-level richness and the abundance of data spanning broad scales and environmental conditions have until now hindered our understanding of invasions at a macroecological scale. To address this limitation, we leveraged quantitative surveys of plant communities in the USA and integrated and harmonized nine datasets into the Standardized Plant Community with Introduced Status (SPCIS) database. The database contains 14,056 unique taxa identified within 83,391 sampling units, of which 52.6% have at least one introduced species. The SPCIS database includes comparable information on plant species occurrence, abundance, and native status across the 50 U.S. States and Puerto Rico. SPCIS can be used to answer macro-scale questions about native plant communities and interactions with invasive plants. There are no copyright restrictions on the data, and we ask the users of this dataset to cite this paper, the respective paper(s) corresponding to the dataset sampling design (all references are provided in Data S1: Metadata S1: Class II-B-2), and the references described in Data S1: Metadata S1: Class III-B-4 as applicable to the dataset being utilized.
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Ecossistema , Plantas , Espécies Introduzidas , Porto Rico , BiodiversidadeRESUMO
Species distribution patterns are widely used to guide conservation planning and are a central issue in ecology. The usefulness of spatial correlation analysis has been highlighted in several ecological applications so far. However, spatial assumptions in ecology are highly scale-dependent, in which geographical relationships between species diversity and distributions can have different conservation concerns. Here, an integrative landscape planning was designed to show the spatial distribution patterns of taxonomic and functional diversity of amphibians and fishes, from multiple species traits regarding morphology, life history, and behavior. We used spatial, morphological, and ecological data of amphibians and fishes to calculate the functional diversity and the spatial correlation of species. Mapping results show that the higher taxonomic and functional diversity of fishes is concentrated in the West Atlantic Forest. Considering amphibians, are located in the East portion of the biome. The spatial correlation of species indicates the regions of the Serra do Mar and the extreme southern part of the Central Corridor as the main overlapped species distribution areas between both groups. New key conservation sites were reported within the Brazilian Atlantic Forest hotspot, revealing cross-taxon mismatches between terrestrial and freshwater ecosystems. This study offers useful spatial information integrating suitable habitats of fishes and amphibians to complement existing and future research based on terrestrial and freshwater conservation. New priorities for biodiversity conservation in rich-species regions highlight the importance of spatial pattern analysis to support land-use planning in a macroecological context.
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Conservação dos Recursos Naturais , Ecossistema , Animais , Conservação dos Recursos Naturais/métodos , Anfíbios , Biodiversidade , PeixesRESUMO
Investigations of phenotypic disparity across geography often ignore macroevolutionary processes. As a corollary, the random null expectations to which disparity is compared and interpreted may be unrealistic. We tackle this issue by representing, in geographical space, distinct processes of phenotypic evolution underlying ecological disparity. Under divergent natural selection, assemblages in a given region should have empirical disparity higher than expected under an evolutionarily oriented null model, whereas the opposite may indicate constraints on phenotypic evolution. We gathered phylogenies, biogeographic distributions, and data on the skull morphology of sigmodontine rodents to discover which regions of the Neotropics were more influenced by divergent, neutral, or constrained phenotypic evolution. We found that regions with higher disparity than expected by the evolutionary-oriented null model, in terms of both size and shape, were concentrated in the Atlantic Forest, suggesting a larger role for divergent natural selection there. Phenotypic disparity in the rest of South America, mainly the Amazon basin, northeastern Brazil, and Southern Andes, was constrained-lower than predicted by the evolutionary model. We also demonstrated equivalence between the disparity produced by randomization-based null models and constrained-evolution null models. Therefore, including evolutionary simulations into the null modeling framework used in ecophylogenetics can strengthen inferences on the processes underlying phenotypic evolution.
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Evolução Biológica , Roedores , Animais , Brasil , Filogenia , Roedores/genética , Seleção GenéticaRESUMO
Trophic specialisation is known to vary across space, but the environmental factors explaining such variation remain elusive. Here we used a global dataset of flower-visitor networks to evaluate how trophic specialisation varies between latitudinal zones (tropical and temperate) and across elevation gradients, while considering the environmental variation inherent in these spatial gradients. Specifically, we assessed the role of current (i.e., net primary productivity, temperature, and precipitation) and historical (i.e., temperature and precipitation stability) environmental factors in structuring the trophic specialisation of floral visitors. Spatial variations in trophic specialisation were not explained by latitudinal zones or elevation. Moreover, regardless of network location on the spatial gradient, there was a tendency for higher trophic specialisation in sites with high productivity and precipitation, whereas historical temperature stability was related to lower trophic specialisation. We highlight that both energetic constraints in animal foraging imposed by climate and resource availability may drive the global variation in trophic specialisation.
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Clima , Flores , Animais , Estado NutricionalRESUMO
Understanding how microbial communities are structured in coral holobionts is important to estimate local and global impacts and provide efficient environment management strategies. Several studies investigated the relationship between corals and their microbial communities, including the environmental drivers of shifts in this relationship, associated with diseases and coral cover loss. However, these studies are often geographically or taxonomically restricted and usually focused on the most abundant microbial groups, neglecting the rare biosphere, including archaea in the group DPANN and the recently discovered bacterial members of the candidate phyla radiation (CPR). Although it is known that rare microbes can play essential roles in several environments, we still lack understanding about which taxa comprise the rare biosphere of corals' microbiome. Here, we investigated the host-related and technical factors influencing coral microbial community structure and the importance of CPR and DPANN in this context by analyzing more than a hundred coral metagenomes from independent studies worldwide. We show that coral genera are the main biotic factor shaping coral microbial communities. We also detected several CPR and DPANN phyla comprising corals' rare biosphere for the first time and showed that they significantly contribute to shaping coral microbial communities.
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Antozoários , Microbiota , Animais , Antozoários/microbiologia , Archaea/genética , Bactérias/genéticaRESUMO
Ancestral adaptations to tropical-like climates drive most multicellular biogeography and macroecology. Observational studies suggest that this niche conservatism could also be shaping unicellular biogeography and macroecology, although evidence is limited to Acidobacteria and testate amoebae. We tracked the phylogenetic signal of this niche conservatism in far related and functionally contrasted groups of common soil protists (Bacillariophyta, Cercomonadida, Ciliophora, Euglyphida and Kinetoplastida) along a humid but increasingly cold elevational gradient in Switzerland. Protist diversity decreased, and the size of the geographic ranges of taxa increased with elevation and associated decreasing temperature (climate), which is consistent with a macroecological pattern known as the Rapoport effect. Bacillariophyta exhibited phylogenetically overdispersed communities assembled by competitive exclusion of closely related taxa with shared (conserved) niches. By contrast, Cercomonadida, Ciliophora, Euglyphida and Kinetoplastida exhibited phylogenetically clustered communities assembled by habitat filtering, revealing the coexistence of closely related taxa with shared (conserved) adaptations to cope with the humid but temperate to cold climate of the study site. Phylobetadiversity revealed that soil protists exhibit a strong phylogenetic turnover among elevational sites, suggesting that most taxa have evolutionary constraints that prevent them from colonizing the colder and higher sites of the elevation gradient. Our results suggest that evolutionary constraints determine how soil protists colonize climates departing from warm and humid conditions. We posit that these evolutionary constraints are linked to an ancestral adaptation to tropical-like climates, which limits their survival in exceedingly cold sites. This niche conservatism possibly drives their biogeography and macroecology along latitudinal and altitudinal climatic gradients.
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Cilióforos , Solo , Biodiversidade , Cilióforos/genética , Ecossistema , FilogeniaRESUMO
Closely related species tend to be more similar than randomly selected species from the same phylogenetic tree. This pattern, known as a phylogenetic signal, has been extensively studied for intrinsic (e.g. morphology), as well as extrinsic (e.g. climatic preferences), properties but less so for ecological interactions. Phylogenetic signals of species interactions (i.e. resource use) can vary across time and space, but the causes behind such variations across broader spatial extents remain elusive. Here, we evaluated how current and historical climates influence phylogenetic signals of bat-fruit interaction networks across the Neotropics. We performed a model selection relating the phylogenetic signals of each trophic level (bats and plants) with a set of current and historical climatic factors deemed ecologically important in shaping biotic interactions. Bat and plant phylogenetic signals in bat-fruit interaction networks varied little with climatic factors, although bat phylogenetic signals positively covaried with annual precipitation. These findings indicated that water availability could increase resource availability, favouring higher niche partitioning of trophic resources among bat species and hence bat phylogenetic signals across bat-fruit interaction networks. Overall, our study advances our understanding of the spatial dynamics of bat-fruit interactions by highlighting the association of current climatic factors with phylogenetic patterns of biotic interactions.
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Quirópteros , Animais , Ecossistema , Frutas , Estado Nutricional , FilogeniaRESUMO
Latitudinal diversity gradients (LDG) and their explanatory factors are among the most challenging topics in macroecology and biogeography. Despite of its apparent generality, a growing body of evidence shows that 'anomalous' LDG (i.e., inverse or hump-shaped trends) are common among marine organisms along the Southeastern Pacific (SEP) coast. Here, we evaluate the shape of the LDG of marine benthic polychaetes and its underlying causes using a dataset of 643 species inhabiting the continental shelf (<200 m depth), using latitudinal bands with a spatial resolution of 0.5°, along the SEP (3-56° S). The explanatory value of six oceanographic (Sea Surface Temperature (SST), SST range, salinity, salinity range, primary productivity and shelf area), and one macroecological proxy (median latitudinal range of species) were assessed using a random forest model. The taxonomic structure was used to estimate the degree of niche conservatism of predictor variables and to estimate latitudinal trends in phylogenetic diversity, based on three indices (phylogenetic richness (PDSES), mean pairwise distance (MPDSES), and variation of pairwise distances (VPD)). The LDG exhibits a hump-shaped trend, with a maximum peak of species richness at ca. 42° S, declining towards northern and southern areas of SEP. The latitudinal pattern was also evident in local samples controlled by sampling effort. The random forest model had a high accuracy (pseudo-r2 = 0.95) and showed that the LDG could be explained by four variables (median latitudinal range, SST, salinity, and SST range), yet the functional relationship between species richness and these predictors was variable. A significant degree of phylogenetic conservatism was detected for the median latitudinal range and SST. PDSES increased toward the southern region, whereas VPD showed the opposite trend, both statistically significant. MPDSES has the same trend as PDSES, but it is not significant. Our results reinforce the idea that the south Chile fjord area, particularly the Chiloé region, was likely the evolutionary source of new species of marine polychaetes along SEP, creating a hotspot of diversity. Therefore, in the same way as the canonical LDG shows a decline in diversity while moving away from the tropics; on this case the decline occurs while moving away from Chiloé Island. These results, coupled with a strong phylogenetic signal of the main predictor variables suggest that processes operating mainly at evolutionary timescales govern the LDG.
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A robust understanding of what drives parasite ß-diversity is an essential step towards explaining what limits pathogens' geographical spread. We used a novel global dataset (latitude -39.8 to 61.05 and longitude -117.84 to 151.49) on helminths of anurans to investigate how the relative roles of climate, host composition and spatial distance to parasite ß-diversity vary with spatial scale (global, Nearctic and Neotropical), parasite group (nematodes and trematodes) and host taxonomic subset (family). We found that spatial distance is the most important driver of parasite ß-diversity at the global scale. Additionally, we showed that the relative effects of climate concerning distance increase at the regional scale when compared with the global scale and that trematodes are generally more responsive to climate than nematodes. Unlike previous studies done at the regional scale, we did not find an effect of host composition on parasite ß-diversity. Our study presents a new contribution to parasite macroecological theory, evidencing spatial and taxonomic contingencies of parasite ß-diversity patterns, which are related to the zoogeographical realm and host taxonomic subset, respectively. This article is part of the theme issue 'Infectious disease macroecology: parasite diversity and dynamics across the globe'.
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Anuros/parasitologia , Biodiversidade , Interações Hospedeiro-Parasita , Nematoides/fisiologia , Trematódeos/fisiologia , Distribuição Animal , Animais , ParasitosRESUMO
Biddick & Burns (2021) proposed a null/neutral model that reproduces the island rule as a product of random drift. We agree that it is unnecessary to assume adaptive processes driving island dwarfing or gigantism, but several flaws make their approach unrealistic and thus unsuitable as a stochastic model for evolutionary size changes.
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Evolução Biológica , Deriva GenéticaRESUMO
BACKGROUND: A key challenge for conservation biology in the Neotropics is to understand how deforestation affects biodiversity at various levels of landscape fragmentation. Addressing this challenge requires expanding the coverage of known biodiversity data, which remain to date restricted to a few well-surveyed regions. Here, we assess the sampling coverage and biases in biodiversity data on fruit-feeding butterflies at the Brazilian Atlantic Forest, discussing their effect on our understanding of the relationship between forest fragmentation and biodiversity at a large-scale. We hypothesize that sampling effort is biased towards large and connected fragments, which occur jointly in space at the Atlantic forest. METHODS: We used a comprehensive dataset of Atlantic Forest fruit-feeding butterfly communities to test for sampling biases towards specific geographical areas, climate conditions and landscape configurations. RESULTS: We found a pattern of geographical aggregation of sampling sites, independently of scale, and a strong sampling bias towards large and connected forest fragments, located near cities and roads. Sampling gaps are particularly acute in small and disconnected forest fragments and rare climate conditions. In contrast, currently available data can provide a fair picture of fruit-feeding butterfly communities in large and connected Atlantic Forest remnants. DISCUSSION: Biased data hamper the inference of the functional relationship between deforestation and biodiversity at a large-scale, since they are geographically clustered and have sampling gaps in small and disconnected fragments. These data are useful to inform decision-makers regarding conservation efforts to curb biodiversity loss in the Atlantic Forest. Thus, we suggest to expand sampling effort to small and disconnected forest fragments, which would allow more accurate evaluations of the effects of landscape modification.