Species richness of vascular plants, bryophytes and lichens in dry grasslands: The effects of environment, landscape structure and competition

We studied the relative importance of local habitat conditions and landscape structure for species richness of vascular plants, bryophytes and lichens in dry grasslands on the Baltic island of Öland (Sweden). In addition, we tested whether relationships between species richness and vegetation cover indicate that competition within and between the studied taxonomic groups is important. We recorded species numbers of vascular plants, bryophytes and lichens in 4 m² plots (n=452), distributed over dry grassland patches differing in size and degree of isolation. Structural and environmental data were collected for each plot. We tested effects of local environmental conditions, landscape structure and vegetation cover on species richness using generalized linear mixed models. Different environmental variables explained species richness of vascular plants, bryophytes and lichens. Environmental effects, particularly soil pH, were more important than landscape structure. Interaction effects of soil pH with other environmental variables were significant in vascular plants. Plot heterogeneity enhanced species richness. Size and degree of isolation of dry grassland patches significantly affected bryophyte and lichen species richness, but not that of vascular plants. We observed negative relationships between bryophyte and lichen species richness and the cover of vascular plants. To conclude, effects of single environmental variables on species richness depend both on the taxonomic group and on the combination of environmental factors on a whole. Dispersal limitation in bryophytes and lichens confined to dry grasslands may be more common than is often assumed. Our study further suggests that competition between vascular plants and cryptogams is rather asymmetric.     

Factors influencing epiphytic bryophyte and lichen species richness at different spatial scales in managed temperate forests

The effect of management related factors on species richness of epiphytic bryophytes and lichens was studied in managed deciduous-coniferous mixed forests in Western-Hungary. At the stand level, the potential explanatory variables were tree species composition, stand structure, microclimate and light conditions, landscape and historical variables; while at tree level host tree species, tree size and light were studied. Species richness of the two epiphyte groups was positively correlated. Both for lichen and bryophyte plot level richness, the composition and diversity of tree species and the abundance of shrub layer were the most influential positive factors. Besides, for bryophytes the presence of large trees, while for lichens amount and heterogeneity of light were important. Tree level richness was mainly determined by host tree species for both groups. For bryophytes oaks, while for lichens oaks and hornbeam turned out the most favourable hosts. Tree size generally increased tree level species richness, except on pine for bryophytes and on hornbeam for lichens. The key variables for epiphytic diversity of the region were directly influenced by recent forest management; historical and landscape variables were not influential. Forest management oriented to the conservation of epiphytes should focus on: (i) the maintenance of tree species diversity in mixed stands; (ii) increment the proportion of deciduous trees (mainly oaks); (iii) conserving large trees within the stands; (iv) providing the presence of shrub and regeneration layer; (v) creating heterogeneous light conditions. For these purposes tree selection and selective cutting management seem more appropriate than shelterwood system.     

Plant species richness as the main driver of moth metacommunities

1. Ecologists have recognised several factors that may explain the distribution of species in a metacommunity. These factors may be related to the dispersal of individuals among the patches and environmental conditions. 2. Here, we attempted to determine which of the four different metacommunity frameworks (patch dynamics, mass effect, neutral processes, and species sorting) explain the distribution of Arctiinae moths in Brazilian savanna areas with different tree species richness. 3. The Arctiinae moths were categorised as habitat specialists or generalists, common or rare, and belonging to the tribes Arctiini and Lithosiini. We hypothesized that environmental variables best explain the abundance and occurrence of habitat specialist species, common species, and members of Lithosiini; whereas spatial processes are more closely related to habitat generalists, rare species, and members of Arctiini. 4. Contrary to our expectations, we found that the species sorting (mainly dictated by the species richness of trees) best explained the variation in abundance and occurrence of the majority of species groups. Spatial processes (more related to patch dynamics, mass effect, and neutral), although they were significantly related to some species groups, were not strong enough to explain the distribution of these species in the study area. 5. The plant species richness was the most important environmental condition, related to moth species niches. Therefore, species sorting best explained the distribution of the species of Arctiinae in the Brazilian savanna.     

Plant species coexistence at local scale in temperate swamp forest: test of habitat heterogeneity hypothesis

It has been suggested that a heterogeneous environment enhances species richness and allows for the coexistence of species. However, there is increasing evidence that environmental heterogeneity can have no effect or even a negative effect on plant species richness and plant coexistence at a local scale. We examined whether plant species richness increases with local heterogeneity in the water table depth, microtopography, pH and light availability in a swamp forest community at three local spatial scales (grain: 0.6, 1.2 and 11.4 m). We also used the variance partitioning approach to assess the relative contributions of niche-based and other spatial processes to species occurrence. We found that heterogeneity in microtopography and light availability positively correlated with species richness, in accordance with the habitat heterogeneity hypothesis. However, we recorded different heterogeneity-diversity relationships for particular functional species groups. An increase in the richness of bryophytes and woody plant species was generally related to habitat heterogeneity at all measured spatial scales, whereas a low impact on herbaceous species richness was recorded only at the 11.4 m scale. The distribution of herbaceous plants was primarily explained by other spatial processes, such as dispersal, in contrast to the occurrence of bryophytes, which was better explained by environmental factors. Our results suggest that both niche-based and other spatial processes are important determinants of the plant composition and species turnover at local spatial scales in swamp forests.     

Habitat diversity associated to island size and environmental filtering control the species richness of rock‐savanna plants in neotropical inselbergs

Disentangling the multiple factors controlling species diversity is a major challenge in ecology. Island biogeography and environmental filtering are two influential theories emphasizing respectively island size and isolation, and the abiotic environment, as key drivers of species richness. However, few attempts have been made to quantify their relative importance and investigate their mechanistic basis. Here, we applied structural equation modelling, a powerful method allowing test of complex hypotheses involving multiple and indirect effects, on an island‐like system of 22 French Guianan neotropical inselbergs covered with rock‐savanna. We separated the effects of size (rock‐savanna area), isolation (density of surrounding inselbergs), environmental filtering (rainfall, altitude) and dispersal filtering (forest‐matrix openness) on the species richness of all plants and of various ecological groups (terrestrial versus epiphytic, small‐scale versus large‐scale dispersal species). We showed that the species richness of all plants and terrestrial species was mainly explained by the size of rock‐savanna vegetation patches, with increasing richness associated with higher rock‐savanna area, while inselberg isolation and forest‐matrix openness had no measurable effect. This size effect was mediated by an increase in terrestrial‐habitat diversity, even after accounting for increased sampling effort. The richness of epiphytic species was mainly explained by environmental filtering, with a positive effect of rainfall and altitude, but also by a positive size effect mediated by enhanced woody‐plant species richness. Inselberg size and environmental filtering both explained the richness of small‐scale and large‐scale dispersal species, but these ecological groups responded in opposite directions to altitude and rainfall, that is positively for large‐scale and negatively for small‐scale dispersal species. Our study revealed both habitat diversity associated with island size and environmental filtering as major drivers of neotropical inselberg plant diversity and showed the importance of plant species growth form and dispersal ability to explain the relative importance of each driver.     

Spatial variation in insect community and species responses to habitat loss and plant community composition

Several experimental studies have examined species responses to manipulations of habitat area and spatial arrangement, but plant composition and spatial variation in species distributions also affect animal responses to habitat alteration. We used an experimental approach to study the combined effects of habitat area, edge, and plant community composition on the spatial structure of insect species richness and composition. The abundance of three guilds (herbivores, predators and parasitoids) and individual species were also analyzed. Habitat patches were created that differed in area and edge by selectively mowing portions of 15 m×15 m plots in a 1.7-ha old field. Spatial and environmental variables were used to predict insect responses in separate multiple regression and ordination models. The variation in species responses due to spatial and environmental variables was then partitioned by combining these variables into an overall regression or ordination. Spatial and environmental variables contributed similar percentages to the total variance in insect species richness, abundance or composition. No significant effects of habitat area were observed in any response variable. Herbivore abundance showed positive responses to legume or grass cover, as well as spatial variation that was unrelated to environmental variables. Predators and parasitoids had greater effects of plant species richness and habitat edge, and less unexplained spatial variation. Individual species differed in their responses to plant variables, depending on host specialization or intraspecific aggregation. Our study highlights the importance of plant community composition and spatial variation apart from environmental variables. Spatial variation stems both from species responses to environmental features as well as species differences in habitat specialization and intraspecific aggregation.     

Bryophyte and lichen diversity: A comparative study

Abstract We describe the regional species richness, variation in species richness and species turnover of bryophytes and lichens from 36 sites in lowland forests of southeastern Australia. The analyses subdivided the two major taxa into their constituent sub-groups: mosses, liverworts, and crustose, fruticose and foliose lichens. They also explored correlations between selected environmental variables and patterns of diversity. On a regional scale, there were 77 species of bryophytes and 69 species of lichens, giving a total of approximately one-third of the total number of vascular plant species in the region. Mean species richness was higher for lichens than bryophytes. Also, the two taxa were negatively correlated because lichens favoured dry sites and bryophytes favoured moist ones. Species turnover was greater for bryophytes than lichens, largely due to the distribution of liverwort species. Foliose lichens showed higher levels of turnover than crustose lichens. Multiple regression and canonical correspondence analysis showed that both taxa and all sub-groups responded to the same three variables: vascular plant cover, time since last fire and topographic position. Other variables, including time since logging and intensity of logging, explained little variation in bryophyte or lichen diversity. The data suggest that the strategies for the conservation of bryophyte and lichen biodiversity will be different, to reflect the different patterns of species richness and species turnover.     

Epiphytic lichens and bryophytes of forest ecosystems in Tuscany (Central Italy)

The distribution of epiphytic bryophytes and lichens on three species of trees (Quercus ilex, Quercus cerris and Fagus sylvatica, representing the forest ecosystems of central Italy at low, medium and high elevations, respectively) was examined with respect to host specificity and habitat differences. Although most species were host-specific, the results suggested that habitat characteristics are more important than phorophyte properties in determining the distribution of lichens and bryophytes. Factors affecting the diversity of the epiphytic flora were different for lichens and bryophytes. In the case of lichens, climatic parameters and forest monospecificity were important factors, whereas tree cover (i.e. shade) and to a certain extent the number of available trees seemed more important for bryophytes.     

The role of regional and local scale predictors for plant species richness in Mediterranean forests

Abstract

Both local and regional predictors play a role in determining plant community structure and composition. Climate, soil features as well as different local history and management affect forest understorey and tree species composition, but to date their specific role is relatively unknown. Few studies have addressed the importance of these predictors, especially in the Mediterranean area, where environmental conditions and human impacts have generated heterogeneous forest communities. In this study, the relationships between environmental variables and species richness of different groups of vascular plants (vascular species, woody species and open habitat species) and bryophytes were investigated in Tuscan forests. A total of 37 environmental variables were used by generalised linear model fitting in order to find parsimonious sub-sets of environmental factors (predictors) that are able to explain species diversity patterns at the local scale. Moreover, the role of regional and local variable groups on species richness of the considered plant groups was estimated by using the variance partitioning approach. We found that local variables, such as forest management and structure, explained more variance than regional variables for total species richness, open habitat species richness and bryophyte species richness. On the other hand, regional variables (such as elevation) played a central role for woody species richness.     

Hidden crown jewels: the role of tree crowns for bryophyte and lichen species richness in sycamore maple wooded pastures

Tree crowns typically cover the vast majority of the surface area of trees, but they are rarely considered in diversity surveys of epiphytic bryophytes and lichens, especially in temperate Europe. Usually only stems are sampled. We assessed the number of bryophyte and lichen species on stems and in crowns of 80 solitary sycamore maple trees (Acer pseudoplatanus) at six sites in wooded pastures in the northern Alps. The total number of species detected per tree ranged from 13 to 60 for bryophytes, from 25 to 67 for lichens, and from 42 to 104 for bryophytes and lichens considered together. At the tree level, 29 % of bryophyte and 61 % of lichen species were recorded only in the crown. Considering all sampled trees together, only 4 % of bryophyte, compared to 34 % of lichen species, were never recorded on the stem. Five out of 10 red-listed bryophyte species and 29 out of 39 red-listed lichen species were more frequent in crowns. The species richness detected per tree was unexpectedly high, whereas the proportion of exclusive crown species was similar to studies from forest trees. For bryophytes, in contrast to lichens, sampling several stems can give a good estimation of the species present at a site. However, frequency estimates may be highly biased for lichens and bryophytes if crowns are not considered. Our study demonstrates that tree crowns need to be considered in research on these taxa, especially in biodiversity surveys and in conservation tasks involving lichens and to a lesser degree also bryophytes.     

Relative importance of landscape and species characteristics on extinction debt,immigration credit and relaxation time after habitat turnover

Habitat turnover concomitantly causes destruction and creation of habitat patches. Following such a perturbation, metapopulations harbor either an extinction debt or an immigration credit, that is the future decrease or increase in population numbers due to this disturbance. Extinction debt and immigration credit are rarely considered simultaneously and disentangled from the relaxation time (time to new equilibrium). In this contribution, we test the relative importance of two potential drivers of time-delayed metapopulation dynamics: the spatial configuration of the habitat turnover and species dispersal ability. We provide a simulation-based investigation projecting metapopulation dynamics following habitat turnover in virtual landscapes. We consider two virtual species (a short-distance and a long-distance disperser) and five scenarios of habitat turnover depending on net habitat loss or gain and habitat aggregation. Our analyses reveal that (a) the main determinant of the magnitude of the extinction debt or immigration credit is the net change in total habitat area, followed by species dispersal distance and finally by the post-turnover habitat aggregation; (b) relaxation time weakly depends on the magnitude of the immigration credit or of the extinction debt; (c) the main determinant of relaxation time is dispersal distance followed by the net change in total habitat area and finally by the post-turnover habitat aggregation. These results shed light on the relative importance of dispersal ability and habitat turnover spatial structure on the components of time-delayed metapopulation dynamics.     

Do vine species in neotropical forests see the forest or the trees?

Questions: Is the occurrence of vine species in neotropical rain forests primarily determined by properties of the forest (environmental factors), by properties of the trees (tree species or tree size) or are vines randomly distributed? Location: Maya Biosphere Reserve, Guatemala. Methods: In five 1‐ha plots that span variation from unlogged forest to forest impacted by recurrent human disturbance we recorded the presence of all climbing vine species on every tree. The presence of all free standing vine species and 11 environmental variables were recorded in 100‐m² subplots. The relationship of host tree diameter and host tree identity on single tree vine species richness was investigated by GLM modelling. Partial redundancy analyses were used to partition the variation in vine species composition on two sources: environmental factors and tree species identity. Results: Single tree vine richness increased with increasing host tree DBH and differed significantly among host species. For climbing vines, the ratio of variation in subplot presence explained by tree species and by environmental variables was ca. 4:1 (in the most disturbed logged plots slightly lower), for free standing vines this ratio varied from 1:2 in the most disturbed logged plots to 9:1 in reserve plots, while a ratio of ca. 1:1 was found for all plots analysed together. Conclusion: Different tree species have different probabilities of being infested by vines. Vines see both the forest and the trees; the environment is more important in earlier developmental stages, properties of individual trees become more important from the time vines start to climb.     

Bole epiphytic lichens as potential indicators of environmental change in subtropical forest ecosystems in southwest China

Lichen epiphytes are applied as excellent environmental indicators worldwide. However, very little is known about epiphytic lichen communities and their response to forest dynamics in subtropical China. This paper proposes the applications of the cover, diversity, and functional traits of epiphytic lichens to assess environmental changes associated with succession in subtropical forests of southwest China. Bole lichens were sampled from 120 plots of eight representative forest types in the Ailao Mountains. Total cover, species richness, diversity and community structure of bole lichens differed significantly among forest types, and the highest cover and diversity occurred in the Populus bonatii secondary forest (PBSF). Sixty-one indicator species were associated with particular forest types and more than 50% occurred in the PBSF. Both cover and diversity of most lichen functional groups varied regularly during forest succession. Lichen pioneer species were not displaced by competitively superior species as succession proceeds and cyanolichens were more prevalent in secondary forests. The results also highlight the importance of habitat variables such as canopy openness, host diversity, forest age, tree size, the size of the largest tree, tree density, and basal area on the lichen community. Consequently, our findings support the notion that epiphytic lichens, in terms of cover, diversity, species composition and functional traits can be used as effective indicators for large-scale and long-term forest monitoring. More importantly, the narrowly lobed foliose group was the best candidate indicator of environmental conditions in this region. The combined application of lichen indicator species and functional groups seemed to be a more reliable and more powerful method for monitoring forest dynamics in subtropical montane ecosystems.     

Species richness–environment relationships within coastal sclerophyll and mesophyll vegetation in Ku‐ring‐gai Chase National Park,New South Wales,Australia

Abstract Patterns in species richness from a wide range of plant communities in Ku‐ring‐gai Chase National Park, New South Wales, Australia, were examined in relation to a number of environmental variables, including soil physical and chemical characteristics. Total species richness and richness of three growth‐form types (trees, shrubs and ground cover) were determined in duplicate 500‐m² quadrats from 50 sites on two geological substrata: Hawkesbury Sandstone and Narrabeen shales and sandstones. Generalized linear models (GLM) were used to determine the amount of variation in species richness that could be significantly explained by the measured environmental variables. Seventy‐three per cent of the variation in total species richness was explained by a combination of soil physical and chemical variables and site attributes. The environmental variables explained 24% of the variation in tree species richness, 67% of the variation in shrub species richness and 62% of the variation in ground cover species richness. These results generally support the hypothesis of an environmental influence on patterns in total species richness and richness of shrubs and ground cover species. However, tree species richness was not adequately predicted by any of the measured environmental variables; the present environment exerts little influence on the richness of this growth‐form type. Historical factors, such as fire or climatic/environmental conditions at time of germination or seedling establishment, may be important in determining patterns in tree species richness at the local scale.     

Scale dependent diversity patterns in arboreal and terrestrial oribatid mite (Acari: Oribatida) communities

In naturally fragmented, isolated, or patchily distributed habitats that contain non‐vagile organisms, we expect dispersal to be limited, and patterns of diversity to differ from similar, yet continuous habitats. We explored the alpha‐beta‐gamma relationship and community composition of oribatid mites (Acari: Oribatida) inhabiting spatially discrete canopy suspended soils, and compared the patterns of diversity with the continuous forest floor soils over two years. We explored dispersal limitation for oribatid mites in the canopy by using additive partitioning of species richness at multiple spatial scales. ANOSIM was used to demonstrate differences in oribatid mite community composition between the canopy and forest floor habitats over different sampling periods. Community composition of oribatid mites differed significantly between canopy and forest floor habitats, by season and yearly sampling period. Oribatid mite richness and abundance were positively correlated with substrate moisture content, particularly in the canopy. Richness and abundance of ground oribatid mites was greater in September than in June, a trend that is reversed in the canopy, suggesting canopy oribatid mite species may have altered life histories to take advantage of earlier moisture conditions. Alpha diversity of oribatid mites in the canopy was lower than the ground at all sampling levels, and not significantly different from a random distribution in either habitat. Beta diversity was greater than expected from a random distribution at the patch‐ and tree‐level in the canopy suggesting dispersal limitation associated with physical tree‐to‐tree dispersal barriers, and limited dispersal among patches within a tree. Beta diversity at the tree‐level was the largest contribution to overall species richness in both canopy and ground habitats, and was also greater than expected on the ground. These results suggest that factors other than physical dispersal barriers, such as aggregation, habitat availability, and environmental factors (moisture), may limit the distribution of species in both habitats.     

Sunken roads as habitats for forest plant species in a dynamic agricultural landscape: effects of age and isolation

Aim This study tests the hypothesis that linear, woody habitat patches surrounding small, sunken rural roads not only function as an unstable sink but also as a true, sustainable habitat for forest plants. Furthermore, factors affecting the presence of forest plant species in sunken roads are determined. Finally, the implications of these findings for the overall metapopulation dynamics of forest plant species in fragmented agricultural landscapes are assessed. Location The study area, c. 155 km² in size, is situated in a fragmented agricultural landscape within the loamy region of central Belgium. Methods Forest species presence–absence data were collected for 389 sunken roads. The effect of area, depth, age and isolation on sunken road species richness was assessed using linear regression and analysis of variance (anova ). Analysis of covariance was employed to study the interaction between age and isolation. Differences in plant community dispersal spectra in relation to sunken road age and isolation were analysed by means of linear regression and anova . Results Sunken roads proved to function as an important habitat for forest plants. The sink‐hypothesis was falsified by a clear species accumulation in time: sunken road species richness significantly increased with the age of the elements. Sunken road age mainly affected species richness through effects on both area and depth, affecting habitat quality and diversity. Furthermore, sunken road isolation had a significant impact on species richness as well, with the number of forest species decreasing with increasing isolation of the elements, indicating dispersal limitation in sunken road habitats. Moreover, a significant age × isolation interaction effect was demonstrated. Differences in regression slopes for isolation between age classes revealed that the effect of isolation intensified with increasing age of the elements. Differential colonization in relation to forest species dispersal capacities probably account for this, as confirmed by the analysis of sunken road plant community dispersal spectra, with the fraction of species with low dispersal capacities increasing with increasing age and decreasing isolation of the elements. Main conclusions During sunken road development, area and depth increase and, gradually, suitable habitat conditions for forest plant species arise. Depending on their ecological requirements and dispersal capacities, forest species progressively colonize these habitats as a function of the element's isolation. The functioning of sunken roads as a sustainable habitat for forest species enhances the metapopulation viability of forest plants in agricultural landscapes and has important consequences for forest restoration practices. Moreover, the results of this work call for integrating the presence of forest species in small‐scaled linear habitat patches in forest fragmentation studies.     

Tree and stand-scale factors affecting richness and composition of epiphytic bryophytes and lichens in deciduous woodland key habitats

Conservation and sustainable forestry are essential in a multi-functional landscape. In this respect, ecological studies on epiphytes are needed to determine abiotic and biotic factors associated with high diversity. The aim of the present study was to evaluate relative sensitivity of conservation targets (epiphytic bryophytes and lichens) in relation to contrasting environmental variables (tree species, tree diameter at breast height, bark crevice depth, pH, tree inclination, pH, forest stand age, area and type) in boreo-nemoral forests. The study was conducted in Latvian 34 woodland key habitat (WKH) boreo-nemoral forest stands. Generalized linear mixed models and canonical correspondence analysis showed that tree species and tree bark pH were the most important variables explaining epiphytic bryophyte and lichen composition and richness (total, Red-listed, WKH indicator species). Forest stand level factors, such as stand size and habitat type, had only minor influence on epiphytic species composition and richness. The results of the present study indicate a need to maintain the diversity of tree species and large trees, particularly Acer platanoides, Carpinus betulus, Fraxinus excelsior, Populus tremula, Tilia cordata, Ulmus glabra and Ulmus laevis in conservation of epiphytic bryophyte and lichen communities in the future.     

Dispersal ability links to cross‐scale species diversity patterns across the Eurasian Arctic tundra

Aim The role of dispersal in structuring biodiversity across spatial scales is controversial. If dispersal controls regional and local community assembly, it should also affect the degree of spatial species turnover as well as the extent to which regional communities are represented in local communities. Here we provide the first integrated assessment of relationships between dispersal ability and local‐to‐regional spatial aspects of species diversity across a large geographical area. Location Northern Eurasia. Methods Using a cross‐scale analysis covering local (0.64 m²) to continental (the Eurasian Arctic biome) scales, we compared slope parameters of the dissimilarity‐to‐distance relationship in species composition and the local‐to‐regional relationship in species richness among three plant‐like groups that differ in dispersal ability: lichens with the highest dispersal ability; mosses and moss allies with intermediate dispersal ability; and seed plants with the lowest dispersal ability. Results Diversity patterns generally differed between the three groups according to their dispersal ability, even after controlling for niche‐based processes. Increasing dispersal ability is linked to decreasing spatial species turnover and an increasing ratio of local to regional species richness. All comparisons supported our expectations, except for the slope of the local‐to‐regional relationship in species richness for mosses and moss allies which was not significantly steeper than that of seed plants. Main conclusions The negative link between dispersal ability and spatial species turnover and the corresponding positive link between dispersal ability and the ratio of local‐to‐regional species richness support the idea that dispersal affects community structure and diversity patterns across spatial scales.     

Evolution of termite functional diversity: analysis and synthesis of local ecological and regional influences on local species richness

Aim To (1) describe termite functional diversity patterns across five tropical regions using local species richness sampling of standardized areas of habitat; (2) assess the relative importance of environmental factors operating at different spatial and temporal scales in influencing variation in species representation within feeding groups and functional taxonomic groups across the tropics; (3) achieve a synthesis to explain the observed patterns of convergence and divergence in termite functional diversity that draws on termite ecological and biogeographical evidence to‐date, as well as the latest evidence for the evolutionary and distributional history of tropical rain forests. Location Pantropical. Methods A pantropical termite species richness data set was obtained through sampling of eighty‐seven standardized local termite diversity transects from twenty‐nine locations across five tropical regions. Local‐scale, intermediate‐scale and large‐scale environmental data were collected for each transect. Standardized termite assemblage and environmental data were analysed at the levels of whole assemblages and feeding groups (using components of variance analysis) and at the level of functional taxonomic groups (using correspondence analysis and canonical correspondence analysis). Results Overall species richness of local assemblages showed a greater component of variation attributable to local habitat disturbance level than to region. However, an analysis accounting for species richness across termite feeding groups indicated a much larger component of variation attributable to region. Mean local assemblage body size also showed the greater overall significance of region compared with habitat type in influencing variation. Ordination of functional taxonomic group data revealed a primary gradient of variation corresponding to rank order of species richness within sites and to mean local species richness within regions. The latter was in the order: Africa > south America > south‐east Asia > Madagascar > Australia. This primary gradient of species richness decrease can be explained by a decrease in species richness of less dispersive functional taxonomic groups feeding on more humified food substrates such as soil. Hence, the transects from more depauperate sites/regions were dominated by more dispersive functional taxonomic groups feeding on less humified food substrates such as dead wood. Direct gradient analysis indicated that ‘region’ and other large‐scale factors were the most important in explaining patterns of local termite functional diversity followed by intermediate‐scale geographical and site variables and, finally, local‐scale ecological variables. Synthesis and main conclusions Within regions, centres of termite functional diversity lie in lowland equatorial closed canopy tropical forests. Soil feeding termite evolution further down food substrate humification gradients is therefore more likely to have depended on the long‐term presence of this habitat. Known ecological and energetic constraints upon contemporary soil feeders lend support for this hypothesis. We propose further that the anomalous distribution of termite soil feeder species richness is partly explained by their generally very poor dispersal abilities across oceans. Evolution, radiation and dispersal of soil feeder diversity appears to have been largely restricted to what are now the African and south American regions. The inter‐regional differences in contemporary local patterns of termite species richness revealed by the global data set point to the possibility of large differences in consequent ecosystem processes in apparently similar habitats on different continents.