RESUMO

Metacommunity processes have the potential to determine most features of the community structure. However, species diversity has been the dominant focus of studies. Nestedness, modularity and checkerboard distribution of species occurrences are main components of biodiversity organisation. Within communities, these patterns emerge from the interaction between functional diversity, spatial heterogeneity and resource availability. Additionally, the connectivity determines the pool of species for community assembly and, eventually, the pattern of species co-occurrence within communities. Despite the recognised theoretical expectations, the change in occurrence patterns within communities along ecological gradients has seldom been considered. Here, we analyse the spatial occurrence of animal species along sampling units within 18 temporary ponds and its relationship with pond environments and geographic isolation. Isolated ponds presented a nested organisation of species with low spatial segregation-modularity and checkerboard-and the opposite was found for communities with high connectivity. A pattern putatively explained by high functional diversity in ponds with large connectivity and heterogeneity, which determines that species composition tracks changes in microhabitats. On the contrary, nestedness is promoted in dispersal-limited communities with low functional diversity, where microhabitat filters mainly affect richness without spatial replacement between functional groups. Vegetation biomass promotes nestedness, probably due to the observed increase in spatial variance in biomass with the mean biomass. Similarly, the richness of vegetation reduced the spatial segregation of animals within communities. This result may be due to the high plant diversity of the pond that is observed similarly along all sampling units, which promotes the spatial co-occurrence of species at this scale. In the study system, the spatial arrangement of species within communities is related to local drivers as heterogeneity and metacommunity processes by means of dispersal between communities. Patterns of species co-occurrence are interrelated with community biodiversity and species interactions, and consequently with most functional and structural properties of communities. These results indicate that understanding the interplay between metacommunity processes and co-occurrence patterns is probably more important than previously thought to understand biodiversity assembly and functioning.

Los procesos metacomunitarios tienen el potencial de determinar la mayoría de las características de la estructura de las comunidades. Sin embargo, los trabajos se han enfocado principalmente en los patrones de diversidad de especies. El anidamiento, la modularidad y la distribución en damero de la ocurrencia espacial de las especies son propiedades básicas de las comunidades. Estos patrones surgen de la interacción entre la diversidad funcional, la heterogeneidad espacial y la disponibilidad de recursos dentro de las comunidades. Además, el pool de especies disponibles para el ensamblaje está determinado por la conectividad de la comunidad, afectando así su patrón de co­ocurrencia de especies. A pesar de las reconocidas expectativas teóricas, el cambio en los patrones de ocurrencia dentro de las comunidades a lo largo de gradientes ecológicos ha sido poco considerado. Aquí, analizamos la ocurrencia espacial de especies animales dentro de 18 charcos temporales y su relación con las características ambientales y el aislamiento geográfico de los charcos. Los charcos aislados presentaron alto anidamiento espacial mientras que los charcos de alta conectividad una distribución de ocurrencias modular y en damero. Por un lado, la baja diversidad funcional en charcos aislados, determinaría que los filtros microambientales afecten la riqueza de especies sin reemplazo espacial entre grupos funcionales, promoviendo un arreglo anidado de ocurrencias. Por otro lado, la alta diversidad funcional en charcos con alta conectividad y heterogeneidad permitiría el reemplazo espacial de especies en gradientes microambientales, determinando los patrones de segregación observados. La biomasa vegetal promueve el anidamiento, probablemente debido al aumento observado en la variación espacial de la biomasa con la biomasa media. La riqueza vegetal también redujo la segregación espacial de los animales dentro de las comunidades. Este resultado puede deberse a que la alta diversidad de plantas de los charcos es también observada a nivel de unidades muestreales, favoreciendo esto la coexistencia espacial de especies. El arreglo espacial de especies dentro de las comunidades estudiadas estaría determinado tanto por factores locales como la heterogeneidad, como por procesos regionales operando a través de la dispersión de individuos entre comunidades. Los patrones de co­ocurrencia de especies están interrelacionados con la diversidad comunitaria y las interacciones bióticas, y consecuentemente con la mayoría de las propiedades estructurales y funcionales de las comunidades. Este estudio evidencia la importancia de la conexión entre procesos metacomunitarios y la co­ocurrencia espacial de especies para comprender el ensamblaje y funcionamiento de la biodiversidad.

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Elevational gradients constitute excellent systems for understanding the mechanisms that generate and maintain global biodiversity patterns. Climatic gradients associated with elevation show strong influence on species distribution in mountains. The study of mountains covered by the same habitat type is an ideal scenario to compare alternatives to the energy hypotheses. Our aim was to investigate how changes in climatic conditions along the elevational gradient drive α- and ß-diversity of four taxa in a mountain system located within a grassland biome. We sampled ants, spiders, birds and plants, and measured climatic variables at six elevational bands (with 10 sampling sites each) established between 470 and 1,000 masl on a mountain from the Ventania Mountain System, Argentina. Species richness per site and ß-diversity (turnover and nestedness) between the lowest band and upper sites were estimated. For most taxa, species richness declined at high elevations and energy, through temperature, was the major driver of species richness for ants, plants and birds, prevailing over productivity and water availability. The major ß-diversity component was turnover for plants, spiders and birds, and nestedness for ants. The unique environmental conditions of the upper bands could favour the occurrence of specialist and endemic species.

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Nestedness and modularity have been found in many species interaction networks. Despite being conceptually distinct, negatively correlated and having different causes, these patterns often co-occur. A realistic but seldom investigated alternative to these simple topologies is hierarchical compound networks, in which the entire network is modular, and modules are internally nested. In compound networks, nestedness is suppressed by modularity at higher network hierarchical levels, but prevails at lower levels, within modules. The aims of this study are (i) to evaluate the prevalence of simple and hierarchical compound topologies in binary and weighted networks describing different kinds of species interactions and (ii) to probe the relationships between modularity and nestedness at different network hierarchical levels. With a procedure that discriminates between simple and compound structures, we re-analysed the topology of 142 well-studied binary networks including seed dispersal, host-parasite, pollination and plant-herbivore interactions; 68 of these also had quantitative information. Additionally, we tested the relationship between robustness and topology of binary networks and compared the robustness of networks with compound topologies to different sequences of species removals. Compound topologies were detected in 34% of binary and 71% of weighted networks of all interaction kinds. These results establish the hierarchical compound topology as a widespread network architecture, often undetected without quantitative data. Furthermore, they disentangle an apparent paradox: despite conflicting with overall nestedness, modularity usually co-occurs with high values of low-level nestedness. Nestedness progressively decreased, while modularity increased, from seed dispersal to host-parasite, pollination and plant-herbivore networks. There were no consistent differences in the robustness of networks with nested and compound topologies. However, compound topologies were especially vulnerable to removal sequences that accelerate the exclusion of entire modules. Compound topologies improve the depiction of ecological networks and differentiate ecological and evolutionary processes that operate at different hierarchical levels, with the potential to advance our understanding of network dynamics, stability and response to species loss or change. Quantitative data often reveal specialization patterns that are indistinguishable in binary networks, strongly improving the detection of modular and compound topologies.

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Neuroptera is an order of insects with a moderate diversity of species numbers yet a high between-family morphological diversity, which has a significant ecological role as a predator. However, there are few studies focused on describing changes in species diversity along environmental gradients. We evaluated changes in the alpha and beta diversity of species and the higher taxa in Neuroptera communities in the Tacaná Volcano in southern Mexico. Five sites each at different altitudes were studied through systematic annual sampling. The taxonomic and phylogenetic alpha diversity were analyzed, as well as the beta diversity and its components, species turnover and nestedness. The alpha diversity had two trends: (1) decreased standardized richness and taxonomic distinctness with increasing altitude, and (2) increased estimated richness and species diversity at intermediate altitudes. The highest turnover values for species, as well as for supra-specific taxa, were recorded at sites with lower altitudes. The highest total beta diversity value was recorded at elevations above 3000 m, whereas the highest number of species and supra-specific taxa were observed at sites between 600 and 2000 m, with an evident decrease above 3000 m. The type of vegetation and environmental conditions may be influencing the decrease in diversity toward higher elevations, which could explain the niche specialization of Neuroptera species to particular sites within the gradient. These results highlight the need to study the environmental factors and their effects on species composition along an elevation gradient.

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The presented datasets relate to the research article entitled "Native forest meta-community structures in Uruguay shaped by novel land use types in their surroundings" [Ramírez and Säumel; Ecology and Evolution, 2022]. The datasets include field survey data on woody species presence and absence from 384 plots at 32 permanent monitoring sites of native forests across the Oriental Republic of Uruguay (South America). We compiled different methods from meta-community studies, remote sensing and landscape ecology to explore how woody species communities are influenced by land use change from local to regional scale. We describe the diverse woody species composition in native forests across Uruguay and structure of metacommunities of woody species. Data on woody species diversity inform landscape planning, land-use management, policy and governance and can be used for further meta-analysis with other local, regional or global data sets.

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We explore the effect of land-use change from extensively used grasslands to intensified silvi- and agricultural monocultures on metacommunity structure of native forests in Uruguay. We integrated methods from metacommunity studies, remote sensing, and landscape ecology to explore how woody species distribution was influenced by land-use change from local to regional scale. We recorded richness and composition of adult and juvenile woody species from 32 native forests, created land-use maps from satellite image to calculate spatial metrics at landscape, class, and patch levels. We also analyzed the influence of land use pattern, climate, topography, and geographic distance between sites (d) on metacommunity, and created maps to visualize species richness and (dis)similarity between communities across the country. Woody species communities were distributed in a discrete pattern across Uruguay. Precipitation and temperature seasonality shaped species distribution pattern. Species richness and community dissimilarity increased from West to East. Latitude did not influence these patterns. Number of patches, landscape complexity, and interspersion and juxtaposition indexes determine woody species distribution at landscape level. Increasing areas covered by crops and timber plantation reduced species richness and increased community dissimilarity. The spatial metrics of native forest fragments at patch level did not influence metacommunity structure, species richness, and community dissimilarity. In conclusion, Uruguayan native forests display a high range of dissimilarity. Pressure of neighborhood land uses was the predominant factor for species assemblages. Conserving landscape structures that assure connectivity within and among native forest patches is crucial. On sites with rare target species, the creation of alliances between governmental institution and landowner complemented by incentives for biodiversity conservation provides opportunities to advance in species protection focused on those less tolerant to land-use change.

RESUMO

Understanding the factors and mechanisms shaping differences in species composition across space and time (ß-diversity) in human-modified landscapes has key ecological and applied implications. This topic is, however, challenging because landscape disturbance can promote either decreases (biotic homogenization) or increases (biotic differentiation) in ß-diversity. We assessed temporal differences in intersite ß-diversity of medium-bodied and large-bodied mammals in the fragmented Lacandona rainforest, Mexico. We hypothesized that, given the relatively short history of land-use changes in the region, and the gain and loss of some species caused by landscape spatial changes, ß-diversity would increase through time, especially its nestedness component. We estimated ß-diversity between 24 forest sites (22 forest patches and two continuous forest sites) in 2011 and 2017 to assess whether ß-diversity is decreasing or increasing in the region, and calculated its turnover and nestedness components to understand the mechanisms responsible for changes in ß-diversity, separately assessing mammal groups with different body mass, feeding guild, and habitat specialization. We then related such temporal changes in ß-diversity to temporal changes in five landscape variables (forest cover, matrix openness, number of patches, edge density and interpatch distance) to identify the landscape drivers of ß-diversity. In contrast with our expectations, ß-diversity decreased over time, suggesting an ongoing biotic homogenization process. This pattern was mostly driven by a decrease in species turnover in all mammal groups, especially in landscapes with decreasing forest cover and increasing forested matrices. Although the nestedness component showed a three-fold increase through time, species turnover was 22 and six times higher than nestedness in 2011 and 2017, respectively. The decreased turnover appears to be driven by an increase in dispersal (i.e., spillover) of native species among patches. The prevalence of species turnover over nestedness indicates that different forest sites have a fairly distinct subset of species (i.e., high complementarity in species composition). Therefore, conserving all remaining forest patches and increasing forest cover is of utmost importance to effectively maintain ß-diversity and conserve the total diversity (γ) of mammal assemblages in this Mesoamerican biodiversity hotspot.

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It is essential to predict areas of losses or exchanges of ecosystem services to adapt communities to the impacts caused by climate change. Particularly for provisioning ecosystem services provided by economically important plant species, understanding the association between climate change impacts and deforestation of native vegetation increases the accuracy of those predictions. Thus, we aim to (i) map the richness of provisioning ecosystem services from economically important native plants; (ii) use forecasts (present and future) of the distribution of ecosystem services to assess areas of changes in the number and type of provisioning ecosystems services. We evaluated provisioning ecosystem services from 110 Cerrado native species of economic importance for the local population. We determined the potential distribution of these plants using ecological niche modeling techniques, which were grouped according to the 21 different services provided. The forecasts for variation in richness and type of service used four future climate change scenarios (RCPs 4.5 and 8.5 in 2050 and 2070). The service losses detected in our models were associated with variables representing the progress of native vegetation deforestation in the biome due to agricultural expansion. Currently, ecosystem services can be found simultaneously in practically the entire biome. However, changes in the global climate will impact the potential geographic distribution of those plants, causing many areas in the biome to have reduced availability of potential ecosystem services. Moreover, due to the association between exposure to climate change and deforestation of native vegetation, the northern region of the biome will likely have the distribution of ecosystem services severely affected.

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RESUMO

Patterns of species replacement and richness differences along environmental gradients or ecoregions shed light on different ecological and evolutionary mechanisms acting on community structure. Communities of aquatic ecosystems of different watersheds are supposed to host distinct species and lineages. Quantifying and understanding the degree to which these differences are affected by environmental and biogeographical factors remains an open question for these environments, particularly in the Neotropical region. We investigated patterns of taxonomic and phylogenetic composition of headwater streams of the Paraná and Paraguai River basins to understand how local and biogeographical factors affect the assembly of fish communities. We also quantified taxonomic and phylogenetic beta diversity by decomposing them into nestedness and turnover components. We found that local environmental factors are the main factors influencing the composition of stream fish communities. Whereas pH affected both taxonomic and phylogenetic turnover, water velocity was responsible for phylogenetic turnover and pH was the main driver of phylogenetic nestedness. Our results indicate an effect of local environmental factors in determining the structure of headwater stream fish communities through a combination of a species sorting mechanism (water velocity and pH) and phylogenetic habitat filtering (pH).(AU)

Padrões de substituição de espécies ou diferenças de riqueza ao longo de gradientes ambientais ou ecoregiões lançam luz sobre diferentes processos e mecanismos ecológicos atuando na estruturação das comunidades. Supõe-se que comunidades aquáticas pertencentes a diferentes bacias pertençam a linhagens evolutivas distintas. Quantificar e entender o grau em que tais diferenças são resultado de fatores ambientais locais e/ou processos biogeográficos ainda é uma questão pouco explorada. Neste estudo nós investigamos os padrões de composição taxonômica e filogenética em riachos de cabeceira das bacias dos Rios Paraná e Paraguai, para entender como fatores locais e biogeográficos afetam a estruturação das comunidades de peixes. Nós quantificamos a diversidade beta taxonômica e filogenética decompondo estas em aninhamento e substituição. Encontramos que os fatores ambientais locais são os principais determinantes da composição das comunidades de peixes destes riachos. Enquanto o pH afetou tanto a substituição de linhagens e de espécies, a velocidade da água foi responsável por uma substituição de linhagens, enquanto o pH foi o principal responsável pelo aninhamento de linhagens. Nossos resultados indicam a importância dos fatores locais através da combinação entre mecanismos de preferência de nicho (velocidade da água e pH) e filtragem ambiental de linhagens (pH).(AU)

Assuntos

RESUMO

Patterns of species replacement and richness differences along environmental gradients or ecoregions shed light on different ecological and evolutionary mechanisms acting on community structure. Communities of aquatic ecosystems of different watersheds are supposed to host distinct species and lineages. Quantifying and understanding the degree to which these differences are affected by environmental and biogeographical factors remains an open question for these environments, particularly in the Neotropical region. We investigated patterns of taxonomic and phylogenetic composition of headwater streams of the Paraná and Paraguai River basins to understand how local and biogeographical factors affect the assembly of fish communities. We also quantified taxonomic and phylogenetic beta diversity by decomposing them into nestedness and turnover components. We found that local environmental factors are the main factors influencing the composition of stream fish communities. Whereas pH affected both taxonomic and phylogenetic turnover, water velocity was responsible for phylogenetic turnover and pH was the main driver of phylogenetic nestedness. Our results indicate an effect of local environmental factors in determining the structure of headwater stream fish communities through a combination of a species sorting mechanism (water velocity and pH) and phylogenetic habitat filtering (pH).(AU)

Padrões de substituição de espécies ou diferenças de riqueza ao longo de gradientes ambientais ou ecoregiões lançam luz sobre diferentes processos e mecanismos ecológicos atuando na estruturação das comunidades. Supõe-se que comunidades aquáticas pertencentes a diferentes bacias pertençam a linhagens evolutivas distintas. Quantificar e entender o grau em que tais diferenças são resultado de fatores ambientais locais e/ou processos biogeográficos ainda é uma questão pouco explorada. Neste estudo nós investigamos os padrões de composição taxonômica e filogenética em riachos de cabeceira das bacias dos Rios Paraná e Paraguai, para entender como fatores locais e biogeográficos afetam a estruturação das comunidades de peixes. Nós quantificamos a diversidade beta taxonômica e filogenética decompondo estas em aninhamento e substituição. Encontramos que os fatores ambientais locais são os principais determinantes da composição das comunidades de peixes destes riachos. Enquanto o pH afetou tanto a substituição de linhagens e de espécies, a velocidade da água foi responsável por uma substituição de linhagens, enquanto o pH foi o principal responsável pelo aninhamento de linhagens. Nossos resultados indicam a importância dos fatores locais através da combinação entre mecanismos de preferência de nicho (velocidade da água e pH) e filtragem ambiental de linhagens (pH).(AU)

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