The true identity of Bryconops cyrtogaster (Norman), and description of a new species of Bryconops Kner (Characiformes: Iguanodectidae) from the Rio Jari,lower Amazon basin

Bryconops cyrtogaster, a poorly known species endemic from the Oyapock River at the border between French Guyana and Brazil, is redescribed herein based on examination of available type material, as well as newly collected material. Additionally, a new rheophilic species from the rio Jari rapids, lower Amazon basin, Brazil, is described. The two species belong to the subgenus Creatochanes and are unique among the congeneres for possessing a posteriorly positioned humeral blotch at the level of the sixth and seventh lateral line scales. They differ from each other by meristic and morphometric characters. The list of endemic species in the rio Jari basin is revised.     

Phytogeography of the Kaieteur Falls, Potaro Plateau, Guyana: floral distributions and affinities

Aim The plant diversity of one location on the Guiana Shield, Kaieteur National Park in Guyana, is used to examine the various hypothesized origins of the flora and to evaluate which may best explain the current plant distributions. Location Kaieteur National Park is located on eastern edge of the Potaro Plateau in central Guyana, South America. The species examined have distributions that vary from local to global. Methods The distribution patterns of the families, genera and species known from Kaieteur are examined using generalized distribution patterns. Results Data on distribution patterns, elevation and habitat were gathered from 131 flowering plant families, 517 genera and 1227 species. These plants represent all taxa that are currently known to occur in the area of the original Kaieteur National Park. Families tend to have cosmopolitan or pantropical distribution, genera are mostly neotropical and at the species level, most species are restricted to the Guiana Shield (c. 40%), northern South America (69%) or neotropical (96%) in distribution, each level inclusive of the previous. Conclusions The flora at the study site in Kaieteur National Park has its strongest affinity with the Guiana Shield; 42.1% of the species have a distribution that corresponds with the Shield or is more restricted within the Shield. There is a distinct flora on the Guiana Shield and its affinities lie with the flora of northern South American and beyond that, the neotropics. The flora is not closely affiliated with the floras of the Brazilian Shield, the Amazon, the Andes, the eastern coastal forests of Brazil, southern South America, or Africa as has been previous suggested.     

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.     

Species Turnover and Vertical Partitioning of Ant Assemblages in the Brazilian Amazon: A Comparison of Forests and Savannas1

We measured beta diversity, or turnover in species composition, of ant assemblages inhabiting patches of forest and savanna (cerrado) near Alter do Chão, in the Brazilian Amazon. In addition, we assessed vertical partitioning of these assemblages by comparing the ground and lower vegetation strata within each habitat. Ants attracted to sardine baits were collected along transects in 39 savanna and 34 forest sites scattered over a 16 km × 16 km landscape. There were about twice as many species in the forest as in the savanna, and within both habitats, we collected more species on the ground than in the vegetation. Similar results were obtained when analyzing data at the level of individual transects, indicating that ant species richness is affected by both habitat and strata. About two‐thirds of the species recorded in the savanna were also found in the forest. Within both habitats, a large proportion of the species found in the least species‐rich stratum (vegetation) were also found in the richer one (ground). However, ordination analysis, using data from individual transects, revealed that different habitats and strata can be clearly discriminated from each other in terms of their ant species composition. Each habitat and stratum had a number of characteristic (indicator) species which, although generally not exclusive to that particular habitat and stratum, predominated there. Our findings indicate that habitat and strata specialization is an important factor governing the organization of ant communities in Amazonia.     

Phylogeny and biogeography of paradoxical frogs (Anura, Hylidae, Pseudae) inferred from 12S and 16S mitochondrial DNA

We used mitochondrial DNA sequences of 12S and 16S ribosomal RNA genes to reconstruct phylogenetic relationships of the nine species of South American aquatic hylids known as paradoxical frogs. Pseudis minuta and P. cardosoi form the sister-group to a clade comprising Lysapsus and the remaining Pseudis. We suggest the resurrection of Podonectes, including P. minutus and P. cardosoi, to avoid the nonmonophyly of Pseudis. Some doubt is cast on the species status of P. cardosoi. Lysapsus limellum, P. bolbodactyla, and P. paradoxa each may comprise more than one species, but lack of comprehensive geographic and morphological appraisals precludes taxonomic changes. Biogeographic implications of the phylogeny are discussed. The correlation between hydrographic basins and Pseudis species is not fully supported, and a recent contact between Amazon populations in eastern Bolivia and western Brazil (Rond?nia) and Paraná basin populations in the Pantanal is suggested. A dispersal-vicariance analysis showed that major diversification of Pseudis and Lysapsus species occurred in the Brazilian Shield, and that the presence of P. paradoxa and L. limellum in the Amazon and Paraná basins is due to recent dispersals. Evidence suggests a vicariant event, most likely caused by Miocene marine introgressions, as the cause for the restricted distribution of L. laevis in the Guiana Shield.     

Synergistic effects of drought and deforestation on the resilience of the south-eastern Amazon rainforest

The south-eastern Amazon rainforest is subject to ongoing deforestation and is expected to become drier due to climate change. Recent analyses of the distribution of tree cover in the tropics show three modes that have been interpreted as representing alternative stable states: forest, savanna and treeless states. This situation implies that a change in environmental conditions, such as in the climate, could cause critical transitions from a forest towards a savanna ecosystem. Shifts to savanna might also occur if perturbations such as deforestation exceed a critical threshold. Recovering the forest would be difficult as the savanna will be stabilized by a feedback between tree cover and fire. Here we explore how environmental changes and perturbations affect the forest by using a simple model with alternative tree-cover states. We focus on the synergistic effects of precipitation reduction and deforestation on the probability of regime shifts in the south-eastern Amazon rainforest. The analysis indicated that in a large part of the south-eastern Amazon basin rainforest and savanna could be two alternative states, although massive forest dieback caused by mean-precipitation reduction alone is unlikely. However, combinations of deforestation and climate change triggered up to 6.6 times as many local regime shifts than the two did separately, causing large permanent forest losses in the studied region. The results emphasize the importance of reducing deforestation rates in order to prevent a climate-induced dieback of the south-eastern Amazon rainforest.     

Phylogeographic patterns of trans-Amazonian vicariants and Amazonian biogeography: the Neotropical rattlesnake (Crotalus durissus complex) as an example

Aim To investigate the phylogeography and execute a historical‐demographic analysis of the Neotropical rattlesnake, Crotalus durissus, thereby testing the hypothesis of a Pleistocene central Amazon corridor of dry forest or savanna that partitioned the Amazonian rain forest into western and eastern portions. Location South America. Methods Using sequences of three mitochondrial genes, we estimated the phylogeography, gene and nucleotide diversity across the South American range of C. durissus. Tree topology tests were used to test alternative biogeographical hypotheses, and tests of population genetic structure and statistical parsimony networks and nested clade phylogeographic analysis (NCPA) were used to infer connectivity and historical population processes on both sides of the Amazon basin. Results Tree topology tests rejected the hypothesis of a coastal dispersal in favour of a central corridor scenario. Gene diversity was similar on both sides of the Amazon basin. Nucleotide diversity indicated that the populations from north of the Amazon basin represented ancestral populations. Analysis of molecular variance (amova ) showed that intra‐population molecular variation was greater than between regions. Historical‐demographic statistics showed significant population expansion south of the Amazon, and little differentiation in the north, indicating moderate past gene flow between north and south of the Amazon. The parsimony network connected clades from the Roraima and Guyana populations with Mato Grosso, suggesting an Amazonian central corridor, and NCPA supported allopatric fragmentation between north and south of the Amazon. Main conclusions The distribution of C. durissus on both sides of the Amazon basin is evidence of changes in the distribution of rain forest vegetation during the Pleistocene. Our results suggest a formerly continuous distribution of this rattlesnake along a central Amazonian corridor during the middle Pleistocene. Allopatric fragmentation inferred from NCPA is consistent with vicariance resulting from a subsequent closure of this habitat corridor. This study emphasizes the potential of trans‐Amazonian open formation species to inform the debate on the past distribution of rain forests in the Amazon Basin.     

South American electric knifefishes of the genus Archolaemus (Ostariophysi,Gymnotiformes): undetected diversity in a clade of rheophiles

Neotropical electric knifefishes of the family Sternopygidae previously considered to represent a single relatively geographically widespread and morphologically variable species, Archolaemus blax, were analysed and found to represent a complex of five species, four of which are new to science. A fifth undescribed species from the Rio São Francisco basin outside the previous known range of the genus was identified. Recognized species of Archolaemus are: A. blax, previously thought to occur in the Rio Araguari, Rio Branco, Rio Tapajós, Rio Tocantins, and Rio Xingu, but which instead proved to be endemic to the Rio Tocantins; Archolaemus ferreirai sp. nov. from the Rio Mucajaí and Rio Uraricoera in the north‐eastern portions of the Amazon basin; Archolaemus janeae sp. nov. of the Rio Xingu and the upper Rio Tapajós, both southern tributaries of the mainstream Amazon; Archolaemus luciae sp. nov. of the Rio Trombetas, Rio Jari, and Rio Tapajós basins of the eastern Amazon, and the independent Rio Araguari draining into the Atlantic Ocean north of the mouth of the Amazon; Archolaemus orientalis sp. nov. of the São Francisco basin in eastern Brazil; and Archolaemus santosi sp. nov. of the Rio Jamari in the south‐western portion of the Amazon basin. The phylogenetic placements of Archolaemus and the recently described genus Japigny relative to the other members of the Eigenmanninae are discussed. A series of synapomorphies for Archolaemus are proposed and a hypothesis of the relationships within that genus is advanced. Rheophily of all members of Archolaemus is discussed, with the genus found to be the most specious clade within the Gymnotiformes living primarily in high‐energy settings. The reported anterior projection of the dentary teeth in A. blax was found to be a consequence of postmortem displacement.     

The role of remnants of Amazon savanna for the conservation of Neotropical mammal communities in eucalyptus plantations

In this study, we investigated the effects of the partial conversion of native Amazon savanna into a eucalyptus plantation on the richness, composition, and abundance of medium and large mammals. Considering these plantations as an integral component of a patchwork savanna landscape, we verified how the negative effects of these plantations can be buffered by the conservation of remnants of native habitat within their area. We analyzed the contribution of each type of Amazonian savanna to the maintenance of the mammalian fauna and the potential of eucalyptus plantations to substitute these native habitats. A total of 23 mammal species were recorded in line-transect surveys conducted within the conserved savanna. By contrast, only eight species were recorded in the eucalyptus plantation and none of them were exclusive to this vegetation. However, the landscape patchwork formed by plantations and savanna was more diverse and contained 19 species of mammals, highlighting the potential importance of remnant savanna vegetation. The maintenance of remnants of savanna habitat may thus be essential for ensuring the conservation of mammals in the anthropogenic landscape of this region. It will also be important to include as many different subtypes of native savanna vegetation as possible and to consider the connectivity between habitats.     

Hemiodus iratapuru,a new species of Hemiodontidae from the Rio Jari,Amazon Basin,Brazil (Teleostei,Characiformes)

Hemiodus iratapuru, a new species of the Hemiodontidae from the Rio Iratapuru, a left bank tributary of the Rio Jari, Amazon Basin, Brazil, is described. The new species is diagnosed from other species of Hemiodus by modifications in the ectopterygoid, tooth form, scale counts, dorsal‐fin form and colour pattern. The new species is proposed to be related to the Hemiodus quadrimaculatus species group.     

Climate and land-use interactively shape butterfly diversity in tropical rainforest and savanna ecosystems of southwestern China

Human-induced habitat conversion and degradation, along with accelerating climatic change, have resulted in considerable global biodiversity loss. Nevertheless, how local ecological assemblages respond to the interplay between climate and land-use change remains poorly understood. Here, we examined the effects of climate and land-use interactions on butterfly diversity in different ecosystems of southwestern China. Specifically, we investigated variation in the alpha and beta diversities of butterflies in different landscapes along human-modified and climate gradients. We found that increasing land-use intensity not only caused a dramatic decrease in butterfly alpha diversity but also significantly simplified butterfly species composition in tropical rainforest and savanna ecosystems. These findings suggest that habitat modification by agricultural activities increases the importance of deterministic processes and leads to biotic homogenization. The land-use intensity model best explained species richness variation in the tropical rainforest, whereas the climate and land-use intensity interaction model best explained species richness variation in the savanna. These results indicate that climate modulates the effects of land-use intensity on butterfly alpha diversity in the savanna ecosystem. We also found that the response of species composition to climate varied between sites: specifically, species composition was strongly correlated with climatic distance in the tropical rainforest but not in the savanna. Taken together, our long-term butterfly monitoring data reveal that interactions between human-modified habitat change and climate change have shaped butterfly diversity in tropical rainforest and savanna. These findings also have important implications for biodiversity conservation under the current era of rapid human-induced habitat loss and climate change.     

Adult habitat preferences, larval dispersal, and the comparative phylogeography of three Atlantic surgeonfishes (Teleostei: Acanthuridae)

Although many reef fishes of the tropical Atlantic are widely distributed, there are large discontinuities that may strongly influence phylogeographical patterns. The freshwater outflow of the Amazon basin is recognized as a major barrier that produces a break between Brazilian and Caribbean faunas. The vast oceanic distances between Brazil and the mid-Atlantic ridge islands represent another formidable barrier. To assess the relative importance of these barriers, we compared a fragment of the mitochondrial DNA (mtDNA) cytochrome b gene among populations of three species of Atlantic surgeonfishes: Acanthurus bahianus, A. chirurgus and A. coeruleus. These species have similar life histories but different adult habitat preferences. The mtDNA data show no population structure between Brazil and the mid-Atlantic islands, indicating that this oceanic barrier is readily traversed by the pelagic larval stage of all three surgeonfishes, which spend approximately 45-70 days in the pelagic environment. The Amazon is a strong barrier to dispersal of A. bahianus (d = 0.024, phiST = 0.724), a modest barrier for A. coeruleus (phiST = 0.356), and has no discernible effect as a barrier for A. chirurgus. The later species has been collected on soft bottoms with sponge habitats under the Amazon outflow, indicating that relaxed adult habitat requirements enable it to readily cross that barrier. A limited ability to use soft bottom habitats may also explain the low (but significant) population structure in A. coeruleus. In contrast, A. bahianus has not been collected over deep sponge bottoms, and rarely settles outside shallow reefs. Overall, adult habitat preferences seem to be the factor that differentiates phylogeographical patterns in these reef-associated species.     

Geographical variation in the high-duty cycle echolocation of the cryptic common mustached bat Pteronotus cf. rubiginosus (Mormoopidae)

The use of bioacoustics as a tool for bat research is rapidly increasing worldwide. There is substantial evidence that environmental factors such as weather conditions or habitat structure can affect echolocation call structure in bats and thus compromise proper species identification. However, intraspecific differences in echolocation due to geographical variation are poorly understood, which poses a number of issues in terms of method standardization. We examined acoustic data for Pteronotus cf. rubiginosus from the Central Amazon and the Guiana Shield. We provide the first evidence of intraspecific geographic variation in bat echolocation in the Neotropics, with calls significantly differing in almost all standard acoustic parameters for the two lineages of this clade. We complement our bioacoustic data with molecular and morphological data for both species. Considerable overlap in trait values prevents reliable discrimination between the two sympatric Pteronotus based on morphological characters. On the other hand, significant divergence in the frequency of maximum energy suggests that bioacoustics can be used to readily separate both taxa despite extensive intraspecific variability in their echolocation across the Amazon. Given the relative lack of barriers preventing contact between bat populations from the Central Amazon and French Guiana, the documented acoustic variation needs to be further studied in geographically intermediate locations to understand the potential isolation processes that could be causing the described divergence in echolocation and to determine whether this variation is either discrete or continuous.     

Phylogeographic and conservation genetic analysis of the black caiman (Melanosuchus niger)

We assessed the spatial distribution of the genetic variability of Melanosuchus niger from 11 localities in South America using 1,027 base pairs of the mitochondrial cytochrome b gene. Screening 132 animals, we found 41 haplotypes, high values of genetic diversity, low values of nucleotide diversity and significant deviations from neutral expectation of allelic frequencies in some localities. Mantel test and nested-clade analysis indicated that isolation-by-distance was an important population dynamic for the species as a whole. Wright's fixation indexes analyses showed that hydrogeographically separated populations from French Guiana together with Amapá state population in Brazil are genetically differentiated from all other populations that are found in the Amazon drainage basin. These indexes also disclosed that the population from Ecuador is genetically differentiated in relation to the populations from Brazil, Peru and French Guiana. Within the Amazon Basin little differentiation exists, and genetic and geographic distances are not correlated. Demographic data as well as population genetic data suggest that M. niger is recovering in some protected regions. However, part of this apparent recovery may be owing to the movement of animals into protected regions.     

Moenkhausia celibela: a new species from the Amazon basin,Brazil (Characiformes: Characidae)

A new species of Characidae, Moenkhausia celibela, is described from the Rio Amazonas at Santarém, Rio Maraú, several localities in the Rio Tapajós, Rio Curuá‐Una, Rio Xingu and Rio Jari, all from the Amazon basin, Brazil. The new species is distinguished from its congeners, except species included in Géry's 1992 Moenkhausia lepidura group, by presenting a dark blotch on the upper caudal‐fin lobe, and the lower lobe is hyaline or light grey. Moenkhausia celibela is distinguished from the species of the M. lepidura group by the absence of a humeral spot and the presence of a roughly triangular and dark spot at the caudal‐fin base, extending posteriorly along the middle caudal‐fin rays, and distinctly separate from the spot on the upper caudal‐fin lobe.     

Stem and leaf hydraulics of congeneric tree species from adjacent tropical savanna and forest ecosystems

Leaf and stem functional traits related to plant water relations were studied for six congeneric species pairs, each composed of one tree species typical of savanna habitats and another typical of adjacent forest habitats, to determine whether there were intrinsic differences in plant hydraulics between these two functional types. Only individuals growing in savanna habitats were studied. Most stem traits, including wood density, the xylem water potential at 50% loss of hydraulic conductivity, sapwood area specific conductivity, and leaf area specific conductivity did not differ significantly between savanna and forest species. However, maximum leaf hydraulic conductance (K _leaf) and leaf capacitance tended to be higher in savanna species. Predawn leaf water potential and leaf mass per area were also higher in savanna species in all congeneric pairs. Hydraulic vulnerability curves of stems and leaves indicated that leaves were more vulnerable to drought-induced cavitation than terminal branches regardless of genus. The midday K _leaf values estimated from leaf vulnerability curves were very low implying that daily embolism repair may occur in leaves. An electric circuit analog model predicted that, compared to forest species, savanna species took longer for their leaf water potentials to drop from predawn values to values corresponding to 50% loss of K _leaf or to the turgor loss points, suggesting that savanna species were more buffered from changes in leaf water potential. The results of this study suggest that the relative success of savanna over forest species in savanna is related in part to their ability to cope with drought, which is determined more by leaf than by stem hydraulic traits. Variation among genera accounted for a large proportion of the total variance in most traits, which indicates that, despite different selective pressures in savanna and forest habitats, phylogeny has a stronger effect than habitat in determining most hydraulic traits.     

Amazon vegetation: how much don’t we know and how much does it matter?

In spite of the existence of a vast body of information on the plant diversity of the Amazon, there remain significant obstacles to informed decision-making and management for conservation. Species distributions are poorly understood and the relationships between diversity and composition of vegetation, ecosystem services and resilience to climatic fluctuations are insufficiently clear. The geographic distribution of phylogenetic diversity in relation to current protected areas is unexplored and very little is known about intraspecific genetic variability and its practical significance. Interpretation of vegetation differentiation and distribution remains relatively simplistic; there are still large parts of the basin for which few or no botanical data exist, and many rare and sparsely distributed species remain undiscovered. Improved understanding of the ecological roles, dynamics and associations of the species of greatest importance for the maintenance of sustainable livelihoods and ecosystem services, habitat restoration and adaptation to climate change is a high priority. In many cases these are common and widespread species. Some of these issues are explored by looking at the Cristalino region in northern Mato Grosso as a case-study. Effective integration, quality assessment, synthesis and application of existing data on the plant diversity of the Amazon will help to address these issues. However, more targeted information is needed from the ground. Future prioritisation of research effort will require a careful and pragmatic balance between the ‘traditional’ focus on rare and endemic species and species-rich communities, and the growing need to understand the key ‘framework’ elements that will determine the future of the Amazon environment. Similar situations are faced elsewhere in the tropics: for botanical research institutes in the 21st century this demands an urgent re-evaluation of core activities and concerted engagement with the issues and challenges facing conservation in a context of rampant population growth, climate change and environmental destruction.     

Seed dispersal mechanisms and the vegetation of forest islands in a West African forest-savanna mosaic (Comoé National Park,Ivory Coast)

The transition zone between forest and savanna is typically characterized by a dynamic patchwork of forest and savanna. We studied the woody plant species composition of 49 forest islands, 18 savanna, and 3 gallery forest plots in the Comoé National Park (Ivory Coast), West Africa's largest savanna reserve. TWINSPAN makes a clear distinction in vegetational composition between these three major habitat types but, nevertheless, more than 50% of the 292 species occur in at least 2 of them. The gallery forest is dominated by Cynometra megalophylla (Caesalpiniaceae), a genus known to dominate humid forests in other afrotropical regions. Ordination reveals four distinct categories of forest islands, (1) humid forests comparable to the gallery forest in their species composition, (2) dry disturbed and (3) dry undisturbed forests and (4) forests formerly inhabited by humans. Disturbed forests harbor more savanna species but also a distinct group of disturbance-tolerant forest species. Compared to other forest species, in this latter group we found an exceptionally high fraction of animal dispersed species (80% vs. 58%), while wind dispersed species or species lacking long distance seed dispersal mechanisms were correspondingly rare. This pattern occurs in spite of the fact that the frequency of wind dispersed species in general increases from dense humid forests to open dry forests and savanna. Species lacking long distance dispersal mechanisms are most abundant among those specialized on humid forests. These observations suggest that the species composition of forest islands is to some extent determined by the seed dispersal abilities of the different species.     

Neotropical savanna ants show a reversed latitudinal gradient of species richness,with climatic drivers reflecting the forest origin of the fauna

Aim

To evaluate the extent to which ant species richness in Neotropical savannas varies with macrogeographic variables, and to identify the potential climatic drivers of such variation.

Location

The Cerrado savanna biome of central Brazil, in a region spanning ca. 20° of latitude and 18°of longitude.

Methods

Standardized sampling of the arboreal and ground‐dwelling faunas was performed in 29 well‐preserved savanna sites using pitfall traps. Species were classified according to their habitat affinities: open‐savanna specialists, forest‐associated species or habitat generalists. We used generalized linear models to evaluate the importance of geographic (latitude, longitude and elevation) and climatic (mean temperature and three metrics of rainfall) variables as predictors of species richness.

Results

The total number of species recorded at each site varied more than twofold (from 59 to 144), and latitude was the best geographic correlate of overall species richness. However, contrary to the expected pattern, more species were found at higher than lower latitudes. This reversed latitudinal pattern of diversity occurred for both the arboreal and ground‐dwelling faunas, and for the habitat generalists and forest specialists. The savanna specialists showed a mid‐latitudinal peak in diversity. Overall, there was a significant positive association between rainfall and species richness, but the strength of this relationship varied with ant habitat affinity.

Main conclusions

The Cerrado ant fauna shows a reverse latitudinal gradient in species diversity, and this can be explained by increasing rainfall during the warmest months of the year (and therefore in plant productivity) with increasing latitude. The sensitivity of Cerrado ant diversity to declining rainfall contrasts with the high resilience to aridity of the Australian savanna ant fauna, and this reflects the contrasting evolutionary histories of these faunas. Our findings highlight the importance of historical processes as drivers of intercontinental contrasts in macroecological patterns.