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AIM: The latitudinal diversity gradient is the dominant pattern of life on Earth, but a consensus understanding of its origins has remained elusive. The analysis of recently diverged, hyper-rich invertebrate groups provides an opportunity to investigate latitudinal patterns with the statistical power of large trees while minimizing potentially confounding variation in ecology and history. Here, we synthesize global phylogenetic and macroecological data on a hyperdiverse (>1100 species) ant radiation, Pheidole , and evaluate the roles of three general explanations for the latitudinal gradient: variation in diversification rate, tropical conservatism, and ecological regulation. LOCATION: Global. TIME PERIOD: The past 35 million years. MAJOR TAXA STUDIED: The hyperdiverse ant genus Pheidole Westwood. METHODS: We assembled geographic data for 1499 species and morphospecies, and inferred a dated phylogeny of Pheidole of 449 species, including 150 species newly sequenced for this study. We tested correlations between diversification rate and latitude with BAMM, HiSSE, GeoSSE, and FiSSE, and examined patterns of diversification as Pheidole spread around the globe. RESULTS: We found that Pheidole diversification occurred in series of bursts when new continents were colonized, followed by a slowdown in each region. There was no evidence of systematic variation of net diversification rates with latitude across any of the methods. Additionally, we found latitudinal affinity is moderately conserved with a Neotropical ancestor and phylogenetic inertia alone is sufficient to produce the gradient pattern. MAIN CONCLUSIONS: Overall our results are consistent with tropical conservatism explaining the diversity gradient, while providing no evidence that diversification rate varies systematically with latitude. There is evidence of ecological regulation on continental scales through the pattern of diversification after colonization. These results shed light on the mechanisms underlying the diversity gradient, while contributing toward a much-needed invertebrate perspective on global biodiversity dynamics.

Aim The fundamental biogeographical processes of colonization, speciation and extinction shape island biotas in space–time. On oceanic islands, area and isolation affect these processes and resulting biodiversity patterns. In the Anthropocene, a new human-mediated colonization dynamic is altering insular ecosystems world-wide. Here, we test predictions about the roles of archipelago area and isolation in structuring ant diversity patterns through effects on both natural and anthropogenic biogeographical processes. Location Tropical Pacific islands. Methods We compiled a comprehensive data set of ant faunal compositions across tropical Pacific archipelagos. Using regression analysis we evaluated the bivariate and interactive effects of area and isolation on the number of colonizing lineages, native species, endemic species, exotic species and total richness in the archipelago. Results There is a strong species–area effect and a much more modest isolation effect on total ant species richness across the Pacific archipelagos. The number of colonizing lineages of each archipelago is strongly driven by the isolation of the archipelago. Endemic species are present in large archipelagos of low and intermediate isolation. The most remote archipelagos are nearly devoid of endemic lineages and their ant faunas are largely composed of Pacific Tramp species and exotics brought from outside the Pacific region. Main conclusions The prominent species–area curve in Pacific ants emerged over time through multiple processes. The colonization of lineages is determined primarily by isolation, with few or no lineages reaching remote archipelagos. Cladogenesis mediates the isolation effect and increases the area effect through the differential radiation of lineages in large archipelagos. In the Anthropocene, the assembly of the species–area relationship has accelerated dramatically through human-mediated colonization. Overall, our results support a view that species–area curves reflect regulating limits on species richness that scale with area, but that multiple biogeographical processes can occur to achieve these limits.

Aim We sought to reconstruct the biogeographical structure and dynamics of a hyperdiverse ant genus, Pheidole, and to test several predictions of the taxon cycle hypothesis. Using large datasets on Pheidole geographical distributions and phylogeny, we (1) inferred patterns of biogeographical modularity (clusters of areas with similar faunal composition), (2) tested whether species in open habitats are more likely to be expanding their range beyond module boundaries, and (3) tested whether there is a bias of lineage flow from high- to low-diversity areas. Location The Old World. Methods We compiled and jointly analysed a comprehensive database of Pheidole geographical distributions, the ecological affinities of different species, and a multilocus phylogeny of the Old World radiation. We used network modularity methods to infer biogeographical structure in the genus and comparative methods to evaluate the hypotheses. Results The network analysis identified eight biogeographical modules, and a suite of species with anomalous ranges that are statistically more likely to occur in open habitat, supporting the hypothesis that open habitats promote range expansion. Phylogenetic analysis shows evidence for a cascade pattern of colonization from Asia to New Guinea to the Pacific, but no ‘upstream’ colonization in the reverse direction. Main conclusions The distributions of Pheidole lineages in the Old World are highly modular, with modules generally corresponding to biogeographical regions inferred in other groups of organisms. However, some lineages have expanded their ranges across module boundaries, and these species are more likely to be adapted to open habitats rather than interior forest. In addition, there is a cascade pattern of dispersal from higher to lower diversity areas during these range expansions. Our findings are consistent with the taxon cycle hypothesis, although they do not rule out alternative interpretations.

Summary 1. Species diversity of arboreal arthropods tends to increase during rainforest succession so that primary forest communities comprise more species than those from secondary vegetation, but it is not well understood why. Primary forests differ from secondary forests in a wide array of factors whose relative impacts on arthropod diversity have not yet been quantified. 2. We assessed the effects of succession-related determinants on a keystone ecological group, arboreal ants, by conducting a complete census of 1332 ant nests from all trees with diameter at breast height ‡ 5 cm occurring within two (unreplicated) 0AE32-ha plots, one in primary and one in secondary lowland forest in New Guinea. Specifically, we used a novel rarefaction-based approach to match number, size distribution and taxonomic structure of trees in primary forest communities to those in secondary forest and compared the resulting numbers of ant species. 3. In total, we recorded 80 nesting ant species from 389 trees in primary forest but only 42 species from 295 trees in secondary forest. The two habitats did not differ in the mean number of ant species per tree or in the relationship between ant diversity and tree size. However, the between-tree similarity of ant communities was higher in secondary forest than in primary forest, as was the between-tree nest site similarity, suggesting that secondary trees were more uniform in providing nesting microhabitats. 4. Using our rarefaction method, the difference in ant species richness between two forest types was partitioned according to the effects of higher tree density (22AE6%), larger tree size (15AE5%) and higher taxonomic diversity of trees (14AE3%) in primary than in secondary forest. The remaining difference (47AE6%) was because of higher beta diversity of ant communities between primary forest trees. In contrast, difference in nest density was explained solely by difference in tree density. 5. Our study shows that reduction in plant taxonomic diversity in secondary forests is not the main driver of the reduction in canopy ant species richness. We suggest that the majority of arboreal species losses in secondary tropical forests are attributable to simpler vegetation structure, combined with lower turnover of nesting microhabitats between trees.

What forces structure ecological assemblages? A key limitation to general insights about assemblage structure is the availability of data that are collected at a small spatial grain (local assemblages) and a large spatial extent (global coverage). Here, we present published and unpublished data from 51 ,388 ant abundance and occurrence records of more than 2,693 species and 7,953 morphospecies from local assemblages collected at 4,212 locations around the world. Ants were selected because they are diverse and abundant globally, comprise a large fraction of animal biomass in most terrestrial communities, and are key contributors to a range of ecosystem functions. Data were collected between 1949 and 2014, and include, for each geo-referenced sampling site, both the identity of the ants collected and details of sampling design, habitat type, and degree of disturbance. The aim of compiling this data set was to provide comprehensive species abundance data in order to test relationships between assemblage structure and environmental and biogeographic factors. Data were collected using a variety of standardized methods, such as pitfall and Winkler traps, and will be valuable for studies investigating large-scale forces structuring local assemblages. Understanding such relationships is particularly critical under current rates of global change. We encourage authors holding additional data on systematically collected ant assemblages, especially those in dry and cold, and remote areas, to contact us and contribute their data to this growing data set.

Ants are extremely abundant in lowland tropical forests where they are important predators, plant mutualists, and herbivores. Their complex role in tropical plant-insect food webs can be best assessed by experimental manipulation of their abundance. Historically, ant exclusion experiments have had a small-scale focus, such as single trees. Here, we test a new 'whole-forest' method of ant exclusion, using treated canopy bait stations, in a diverse tropical rainforest in New Guinea. 2. We conducted a 10-month manipulative experiment in primary and secondary rainforests. In each forest type, a 625 m 2 treatment plot was isolated from the sur- rounding forest and 135 bait stations treated with fipronil, S-methoprene, and hydram- ethylnon were placed in trees to suppress ants. Ant activity was monitored in the forest canopy and understorey with an additional 65 stations in treatment and control plots. 3. We achieved a dramatic decline in ant abundance in treatment plots compared with controls in both forest types, with an average decrease in ant numbers per station of 82.4% in primary and 91.2% in secondary forest. In particular, native dominant species Oecophylla smaragdina, Anonychomyrma cf. scrutator in primary forest, and invasive Anoplolepis gracilipes in secondary forest were greatly affected. In contrast, Tapinoma melanocephalum flourished in treatment plots, perhaps benefiting from reduced competition from other ant species. 4. Our study demonstrates that it is possible to selectively eradicate most of the foraging ants in a structurally complex tropical forest. We propose whole-forest manip- ulation as a novel tool for studying the role of ants in shaping plant-insect food webs.

A central focus of ecology and biogeography is to determine the factors that govern spatial variation in biodiversity. Here, we examined patterns of ant diversity along climatic gradients in three temperate montane systems: Great Smoky Mountains National Park (USA), Chiricahua Mountains (USA), and Vorarlberg (Austria). To identify the factors which potentially shape these elevational diversity gradients, we analyzed patterns of community phylogenetic structure (i.e. the evolutionary relationships among species coexisting in local communities). We found that species at low-elevation sites tended to be evenly dispersed across phylogeny, suggesting that these communities are structured by interspecific competition. In contrast, species occurring at high-elevation sites tended to be more closely related than expected by chance, implying that these communities are structured primarily by environmental filtering caused by low temperatures. Taken together, the results of our study highlight the potential role of niche constraints, environmental temperature, and competition in shaping broad-scale diversity gradients. We conclude that phylogenetic structure indeed accounts for some variation in species density, yet it does not entirely explain why temperature and species density are correlated.

We characterized a plant–caterpillar food web from secondary vegetation in a New Guinean rain forest that included 63 plant species (87.5% of the total basal area), 546 Lepidoptera species and 1679 trophic links between them. The strongest 14 associations involved 50% of all individual caterpillars while some links were extremely rare. A caterpillar randomly picked from the vegetation will, with ‡ 50% probability, (1) feed on one to three host plants (of the 63 studied), (2) feed on < 20% of local plant biomass and (3) have ‡ 90% of population concentrated on a single host plant species. Generalist species were quantitatively unimportant. Caterpillar assemblages on locally monotypic plant genera were distinct, while sympatric congeneric hosts shared many caterpillar species. The partitioning of the plant–caterpillar food web thus depends on the composition of the vegetation. In secondary forest the predominant plant genera were locally monotypic and supported locally isolated caterpillar assemblages.

Caterpillar assemblages feeding on two alien plants, Piper aduncum and P. umbellatum, were studied in lowland rainforest in Papua New Guinea and compared with assemblages from 69 species of native woody hosts, including congeneric P. macropiper. 2. Species richness of caterpillars feeding on P. aduncum (29 species per 1500 m 2 of foliage) and P. umbellatum (36 species) was higher than the median richness for the 69 native hosts (23 species). 3. The probability that a caterpillar species colonised alien Piper increased with its host range from 3% for the species feeding on a single plant family to 92% for the species with host range >10 plant families. 4. The assemblage on P. aduncum was dominated by a single species (Herpeto- gramma sp. near licarsisalis, Crambidae), which represented 48% of individuals, and also had a high proportion (34%) of rare species, collected as single individ- uals. This community structure was indistinguishable from that of a typical native host. In contrast, the P. umbellatum assemblage was unusual as no species represented >10% of individuals. 5. The aggressive invasion by P. aduncum of early successional vegetation is not explained by a competitive advantage due to low herbivore load, as the abundance of caterpillars feeding on it was comparable to that of native pioneer plants. 6. The caterpillar assemblage on P. aduncum demonstrated that an assemblage indistinguishable from native assemblages in density, species richness, and dominance structure (but not in host specificity) can originate from the existing species pool in lowland rainforests on a recently established tree species in