Few studies have investigated the ecological interactions between wild species of Suidae and their parasites, leaving our knowledge concerning this host–parasite system fragmented. In the present study, we applied network studies to analyse community nestedness in helminth assemblages of common warthogs, Phacochoerus africanus (Gmelin) (Suidae). Helminth data were compiled from 95 warthogs, including young and adult males and females, from 2 different conservation areas in Mpumalanga and Limpopo Provinces, South Africa, collected monthly over a period of 1 year each. The aim was to study the effect of host sex, age and season of sampling on the structure of helminth infracommunities harboured by the warthogs and to search for non-random structural patterns in the warthog–helminth interaction networks. Furthermore, we investigated the influence of a warthog's age, sex and season of sampling on beta diversity and dark diversity of their helminth infracommunities. Lastly, we asked whether the effects of host sex, age and sampling season on helminth communities differed between the 2 localities. We found that helminth communities of warthogs were nested and host–parasite interactions were influenced by all 3 factors as well as combinations thereof. However, the resulting patterns differed at the 2 localities, indicating that local environmental processes are important drivers of community structure.

Fire plays a crucial role in shaping plant communities in South American savannas. However, the impact of biotic interactions on tree communities still needs to be better explored. In this study, we evaluated the influence of tree-on-tree interactions and abiotic conditions on the structure and diversity of woody communities in savannas of Central Brazil. We used plots of 10 × 10 m in three preservation areas of savanna to assess the abundance and composition of juveniles and adults in woody communities associated with two Apocynaceae tree species: Hancornia speciosa, postulated to show negative interactions with the associated tree community, and Himatanthus obovatus, postulated to show positive interactions. Our results revealed that while abiotic factors, represented by the altitude, are more critical in shaping the community of juvenile trees, tree-on-tree interactions have a stronger influence on adult tree populations, driving community dynamics during plant recruitment. Specifically, Hancornia speciosa reduces the abundance of adults, whereas Himatanthus obovatus enhances their relative abundance; both shape the composition of tree communities. Consequently, tree-on-tree interactions create distinct mosaics at various stages of regeneration, contributing to savanna dynamics and conservation.

Antarctic soils provide an excellent setting to test biogeographical patterns across spatial and environmental scales given their relatively simple communities and the dominance of physical factors that create strong environmental gradients. Additional urgency is given by the fact that their unique terrestrial communities are the subject of conservation efforts in a rapidly changing environment. We investigated relationships of soil community assembly and alpha and beta diversity with climatic and environmental parameters across regional and local scales in Maritime Antarctica. We sampled from a regional gradient of sites that differ in habitat severity, ranging from relatively favourable to harsher physicochemical conditions. At the regional scale, bacterial community characteristics and microarthropod abundance varied along this severity gradient, but most measures of fungal communities did not. Microarthropod and microbial communities differed in which soil and climate parameters were most influential, and the specific parameters that influenced each taxon differed across broad and fine spatial scales. This suggests that conservation efforts will need to focus on a large variety of habitat characteristics to successfully encompass diversity across taxa. Because beta diversity was the result of species turnover, conservation efforts also cannot focus on only the most biodiverse sites to effectively preserve all aspects of biodiversity.

Earth is rapidly losing free-living species. Is the same true for parasitic species? To reveal temporal trends in biodiversity, historical data are needed, but often such data do not exist for parasites. Here, parasite communities of the past were reconstructed by identifying parasites in fluid-preserved specimens held in natural history collections. Approximately 2500 macroparasites were counted from 109 English Sole (Parophrys vetulus) collected between 1930 and 2019 in the Salish Sea, Washington, USA. Alpha and beta diversity were measured to determine if and how diversity changed over time. Species richness of parasite infracommunities and community dispersion did not vary over time, but community composition of decadal component communities varied significantly over the study period. Community dissimilarity also varied: prior to the mid-20th century, parasites shifted in abundance in a seemingly stochastic manner and, after this time period, a canalization of community change was observed, where species' abundances began to shift in consistent directions. Further work is needed to elucidate potential drivers of these changes and to determine if these patterns are present in the parasite communities of other fishes of the Salish Sea.

We studied patterns of compositional, functional, and phylogenetic α- and β-diversity in flea and gamasid mite infracommunities of small Siberian mammals, taking into account host-associated (species) and environmental (biome or sampling period) factors. We asked: (a) How do these factors and their interactions affect infracommunity diversity? (b) Does infracommunity composition, in terms of species, traits, and phylogenetic lineages, deviate from random? (c) Are species, traits, and phylogenetic lineages in infracommunities clustered or overdispersed?, and (d) Do patterns of diversity differ between the three diversity facets and/or the two ectoparasite taxa? We found that the α-diversity of infracommunities was strongly affected by host species, biome, and sampling period. The highest proportion of infracommunity diversity in both taxa was associated with the interaction between either host species and biome or host species and sampling period. Infracommunities of both taxa within, as well as between, host species, biomes, and sampling periods were characterized by the clustering of species, traits and lineages. The patterns of the effects of host species, biome, and sampling period on infracommunity diversity were congruent among the three diversity facets in both fleas and mites. We conclude that the assembly patterns in ectoparasite infracommunities mirror those characteristics of component and compound communities.

Both decreases in compositional similarity with increasing geographic distances between sites (i.e. distance–decay relationship) and vertical stratification of species composition are key issues in ecology. However, the intersection between these two trends has scarcely been investigated. Here we use identical sampling methods in the canopy and at ground level in a tropical rainforest remnant on the coast of the Gulf of Mexico to evaluate, for the first time, a distance–decay relationship within vertical strata in insect assemblages. We found that the ant assemblage was vertically stratified; ant species richness was higher at ground level than in the canopy, and the species composition differed between the two vertical strata. Moreover, we observed that β-diversity increased with geographic distance at ground level, but not in the canopy strata. However, contrary to our prediction, there was less species turnover (lower β-diversity) between vertical strata than between trees. These findings may reflect differences in the dispersal capacity and nest habit of ants from each vertical stratum, and also habitat heterogeneity on the horizontal scale, e.g. the species of sampled trees. Our results illustrate the importance of sampling more than one vertical stratum to understand the spatial distribution patterns of biological diversity in tropical rainforests.

The functional composition of plant communities in montane regions has been studied for decades, and most recent analyses find that environmentally favourable landscapes at lower altitudes tend to be dominated by species with resource-acquisitive traits, while more resource-conservative taxa dominate higher-altitude communities. However, it is unclear the extent to which this pattern is driven by co-gradient variation within clades or changes in clade representation across the gradient. To test for co-gradient variation, species composition, phylogenetic structure and functional traits were quantified for 97 species within the plant family Melastomataceae at five locations across a 2500-m altitudinal gradient along Volcán Barva in Costa Rica. Average melastome leaf force to punch, specific leaf area and leaf size vary with altitude, while four other functional traits do not. Taxonomic dissimilarity between communities was correlated with altitudinal difference, while phylogenetic dissimilarity was correlated with altitudinal dissimilarity only when measured with a metric that emphasizes shallow turnover of the tips of the phylogeny. These results highlight how species turnover may be more pronounced than functional or phylogenetic variation along altitudinal gradients. In addition, these results highlight the conservation value of lowland tropical forests, which here harbour a disproportionate amount of phylogenetic and functional diversity.

The river zonation hypothesis predicts that abiotic and biotic conditions along riparian gradients drive variation in animal communities. Glass frogs are a diverse group of Neotropical anurans that use riparian habitats exclusively for oviposition and larval development, but little is known about how glass frog communities are distributed across riparian gradients. Here, we measured glass frog community assembly across a gradient of riparian habitats from first- to fifth-order streams at La Selva Biological Station, Costa Rica. We performed repeated nocturnal frog calling surveys and built occupancy and N-mixture abundance models to test for varying patterns of species occupancy, community assembly, species richness (α-diversity) and species turnover (ß-diversity). We observed significant differences in patterns of species occupancy and community assembly across a stream-order gradient: occupancy of two species increased with stream order (Teratohyla pulverata, Hyalinobatrachium fleischmanni), one species decreased (Teratohyla spinosa), and one species did not vary (Espadarana prosoblepon). We evaluated four a priori hypotheses describing how α- and ß-diversity of centrolenids are shaped across the riparian gradient; our data were most consistent with a pattern of nested assemblages and increasing species richness along the riparian gradient. Species-specific patterns of occupancy and abundance resulted in assemblage-level differences consistent with theoretical predictions for highly aquatic organisms along riparian gradients.

To address how seasonality affects the richness and abundance of tropical insects, we compared the canopy and understorey communities of fruit-feeding butterflies in a seasonal Atlantic forest in south-eastern Brazil. Butterflies were sampled over 1 y using a standardized design with baited traps. A total of 2047 individuals in 69 species were recorded (1415 in the canopy, 632 in the understorey). Clear differences were found between canopy and understorey, with significantly higher butterfly abundances in the canopy. We observed two marked peaks of abundance and richness in both strata; one at the transition from dry to the wet seasons, and the other at the transition from wet to dry seasons. We found lower species turnover throughout the year in the canopy. We interpret this as evidence that temperature is more important than rainfall in explaining the yearly variation of abundance in vertical strata. The higher temperatures found in the canopy may allow butterflies to maintain activity in this stratum all year round, whereas the understorey is subject to colder temperatures, thus presenting a higher species turnover. These results improve our understanding of diversity gradients between evergreen and seasonal tropical forests, allowing insights into how climate and beta diversity gradients interact.

Effective conservation of global species diversity requires a clear understanding of spatial scales that support overall diversity across broad scales. Abandonment of semi-natural grasslands has increased their fragmentation and decreased their areal extent. We quantified diversity patterns of plant communities in Japan across hierarchical scales to facilitate the development of an effective nationwide strategy for conserving species diversity in remnant semi-natural grasslands. We applied additive partitioning of plant species diversity, using a nested hierarchical design at three spatial scales (quadrat, grassland, and western and eastern regions of Japan) for three groups of plant species (all species, grassland species and national Red Listed species). We consistently found lower proportions of among-quadrats diversity, and higher proportions of among-grasslands diversity and between-regions diversity in the overall diversity of the entire species complement than would be expected by chance. The high contribution of among-grasslands diversity to overall diversity suggests that each grassland had a unique species content. The second-ranking contributor to overall diversity differed between grassland species and Red Listed species: the second-ranking contributor for grassland species was diversity at the among-quadrats scale but the second-ranking contributor for all species and for Red Listed species was diversity at the between-regions scale. Thus, effective conservation of diversity of the entire species complement in remnant semi-natural grasslands requires preservation of beta diversity in individual grasslands. Our findings highlight the importance of strengthening local preservation and restoration activities within each grassland, and of nationwide strategies for conserving Red Listed species in remnant semi-natural grassland communities.

Epiphytic orchids are very diverse in montane forests, but fragmentation modifies this diversity. Twenty fragments were quantified to evaluate the effects of fragmentation on the alpha and beta diversities of epiphytic orchids in a montane forest located in southern Mexico. The following factors were evaluated: area, core area, shape, edge density, Euclidean nearest-neighbour distance fragment and contrast index. In each fragment, two transects of 2 × 50 m were drawn, and the trees with a diameter at breast height ≥ 20 cm were recorded. In each tree, the orchid species present were identified and quantified. Twenty-three species of epiphytic orchid in 234 phorophytes corresponding to 20 species were recorded. The epiphytic orchid richness per tree and species turnover was different between the phorophytes. The edge density and the contrast index had significant effects on the alpha diversity, while the isolation of the fragments significantly affected the beta diversity. The edge density positively affected the alpha diversity of the epiphytic orchids, likely through microclimatic changes caused by fragmentation. Drought-tolerant species were common on the edges of the fragments, and shade-tolerant species established on the core area of the fragments. This pattern most likely depends on the ecological range of the taxa, which is crucial to their development and persistence in fragmented habitats.

To what extent tropical forest persisted in the Malay-Thai Peninsula during the Last Glacial Maximum, or contracted southwards with subsequent post-glacial expansion, has long been debated. These competing scenarios might be expected to have left contrasting broad spatial patterns of diversity of forest-dependent taxa. To test for a post-glacial northward spread of forest, we examined latitudinal clines of forest-dependent bat species at 15 forest sites across Peninsular Malaysia. From captures of 3776 insectivorous forest bats, we found that low richness characterized the north of the study area: predicted richness of 9–16 species, compared with 21–23 in the south. Predicted species richness decreased significantly with increasing latitude, but showed no relationship with either seasonality or peninsula width. Analyses of beta-diversity showed that differences between communities were not related to geographical distance, although there was evidence of greater differences in species numbers between the most distant sites. Assemblages were consistently dominated by six cave-roosting species from the families Rhinolophidae and Hipposideridae, while another 16 species were consistently rare. We suggest that these observed patterns are consistent with the hypothesized northward expansion of tropical rain forest since the Last Glacial Maximum, but emphasize that more surveys in the extreme north and south of the peninsula are required to support this assertion.

Major tropical rivers have been suggested to be important dispersal barriers that increase the beta diversity of animal communities in lowland rain forests. We tested this hypothesis using assemblages of frogs in the floodplains of the Sepik River, a major river system in Papua New Guinea. We surveyed frogs at five sites within a continuous 150 × 500-km area of lowland rain forest bisected by the Sepik, using standardized visual and auditory survey techniques. We documented 769 frogs from 44 species. The similarity in species composition decreased with logarithm of geographical distance between the sites, which ranged from 82 to 465 km. The similarity decay did not depend on whether or not the compared sites were separated by the Sepik River or whether the species were aquatic or terrestrial breeders. Likewise, a DCA ordination of frog assemblages did not show separation of sites by the river as a significant factor explaining their composition. Our results suggest that even major rivers, such as the Sepik, may not act as dispersal barriers. Rivers may not limit the distribution of frogs and therefore have a limited effect on determining frog species abundance and assemblage structure in rain forests.

The degree to which geographical location rather than environment affects the maintenance of high tropical forest beta diversity on altitudinal gradients is not well understood. Forest composition and its relationship to climate, soil, altitude and geographical distance were determined across an 1114-km2 landscape in south Pacific Costa Rica spanning an altitudinal gradient (0–1500 m asl). In 37 0.25-ha plots, > 200 species of dicot trees (≥ 30 cm dbh) and canopy palms (≥ 10 cm dbh) were found. Ordination analysis showed strong species composition patterns related to altitude; plot coordinates on the main axis showed negative correlations to the abundance of lowland-forest species Iriartea deltoidea (r = −0.54) and Brosimum utile (r = −0.65), and positive correlations to higher-altitude species Alchornea glandulosa (r = 0.63), Quercus sp. (r = 0.50) and Ocotea sp. 2 (r = 0.48). Mantel correlations, correlograms and variation partitioning analysis of relationships between floristic composition and spatial and environmental factors indicated that spatial location of the plots – potentially, dispersal limitation – was the single most important (R2adj = 0.149) driver of beta diversity, but that environmental heterogeneity also plays an important role. In particular, palm species turnover was strongly related to soil chemical properties. The effects of dispersal limitation on floristic assembly could determine the future distribution of plant communities as a result of climate change.

The wet tropical forests in Madagascar have endemic dung beetles that have radiated for tens of millions of years using a limited range of resources produced by the species-poor mammalian fauna. Beetles were trapped in two wet-forest localities over 4 years (6407 trap nights, 18,869 individuals). More limited data for six other local communities were used to check the generality of the results. Local communities are relatively species poor (around 30 species) in comparison with wet-forest-inhabiting dung beetle communities elsewhere in the tropics (typically 50 or more species). The species belong to only two tribes, Canthonini and Helictopleurina (Oniticellini), which have evolved, exceptionally for dung beetle tribes, completely nocturnal versus diurnal diel activities, respectively. Patterns in the elevational occurrence, body size and resource use suggest that interspecific competition restricts the numbers of locally coexisting species exploiting the limited range of resources that are available. On the other hand, regional turnover in the species composition is exceptionally high due to a large number of species with small geographical ranges, yielding a very large total fauna of dung beetles in Madagascar (>250 species). Apart from exceptionally low local (alpha) diversity and high beta diversity, the Malagasy dung beetle communities are ecologically distinctive from comparable communities in other tropical regions in having high numerical dominance of the most abundant species, small average body size and low degree of resource specialization.

The potential effect of forest type on the structuring of animal communities in western Amazonia remains poorly understood. In this study, we tested the hypothesis that amphibian species richness, composition and abundance differ across forest types in the lowland rain forest of south-eastern Peru. By using 320 individual transects, we compared the amphibian assemblages across four major forest types (floodplain, terra firme, bamboo and palm swamp) at each of four sites separated by 3.5–105 km. We identified 1967 individuals of 65 species in 11 families and found that a large proportion of the amphibian diversity in this region is attributed to habitat-related beta diversity. Overall, we found that forest type is more important than site in predicting both species composition and abundance. We also found that, when analyses are conducted separately for each forest type and include species abundance data, similarity between assemblages decreases with increasing geographic distance. In contrast to studies that considered species presence/absence but ignored species abundances, our results highlight the importance of including abundance data in the assessment of animal diversity patterns in western Amazonia. We conclude that evaluating community structure across forest types can improve our understanding of diversity patterns in this region.

Understanding how species assemblages are structured in relation to environmental variation is a central issue in community ecology. However, factors that create regional variation in relative species abundances have been little studied due to the rarity of large-scale datasets. Here, we investigated a large dataset (30 180 0.5-ha plots spread over 1 600 000 ha) gathered from forest planning inventories in the semi-deciduous forest of the south western Central African Republic. We used Correspondence Analysis and Non-Symmetric Correspondence Analysis on Instrumental Variables to analyse variation in the abundance of 73 common tree species in relation to soil type, rainfall and proximity to villages. Together, environmental variables explained 10.3% of multi-species floristic variation among plots, and the regional spatial structure almost disappeared when the effects of these variables were removed. A Trend Surface Analysis using a third order polynomial function of the geographical coordinates of the plots explained 14.5% of the floristic variation and more than 75% of this variation was explained by environmental variables. Sandy soil was the most influential factor affecting floristic composition. Residual spatial variation not explained by the environmental variables probably reflects the natural and anthropogenic history of the vegetation.

Many studies suggest that edaphic variables are major determinants of frog distributions. However, leaf-litter depth and soil characteristics are influenced by distance from streams, so the apparent relationship between edaphic characteristics and species distributions could be an artefact of the dependence of species on free water for reproduction. Therefore, we investigated the effect of edaphic variables on the mesoscale distribution of frog species not dependent on free water for reproduction. We evaluated the effects of soil texture, pH, slope, number of trees and leaf-litter volume on the distribution of nine terrestrially reproducing anuran species in the Reserva Ducke, a 100-km2 terra firme forest preserve in central Amazonia. Diurnal and nocturnal assemblages of anuran species were sampled in 72 plots systematically distributed across the reserve. We sampled the diurnal anuran assemblage by visual encounter in 250 × 1-m plots and the nocturnal assemblage in 250 × 20-m plots using both auditory and visual surveys. The majority of terrestrially breeding anuran species were influenced by topographic and/or edaphic variables, such as slope, soil clay content and pH. However, responses to environmental predictors differed among species. Most species occurred throughout all environmental gradients and relationships with soil characteristics were subtle, indicating that these species occur in the majority of habitats in Reserva Ducke. The results of this study indicate that terrestrially breeding frogs are habitat generalists that show little mesoscale beta diversity associated with habitat variation.