Contribution of cocoa plantations to the conservation of native ants (Insecta: Hymenoptera: Formicidae) with a special emphasis on the Atlantic Forest fauna of southern Bahia,Brazil

By maintaining a forest-like structure, shaded cocoa plantations contribute to the conservation of ants that usually live in the soil, leaf litter or canopy of tropical forests. Here we synthesize the available information on the diversity and community structure of ants in shaded cocoa plantations in the Atlantic forest region of Brazil, compare ant assemblages in cocoa agroforests with forests and other forms of agriculture, and discuss how these shaded plantations contribute to the conservation of the ants in the Atlantic Forest region. We also discuss ants of economical importance and of special interest, including Camponotus, Dolichoderus, Gnamptogenys, Pachycondyla, Pseudomyrmex and other litter dwelling genera. We discuss the situation of the tramp ant Wasmannia auropunctata in the Bahian cocoa-producing region where it is considered as native, and that of the two cryptobiotic genera Thaumatomyrmex and Typhlomyrmex, as well as that of proven and possible endangered army ant and Ponerini species. A total of 192 ant species from four strata were found in extensive sampling of a cocoa plantation with a relatively simple shade canopy (comprised primarily of Erythrina). Species richness in the cocoa plantations corresponded roughly to that of low diversity native forests, and species composition of cocoa plantations was most similar to native habitats (forest and mangroves) while ant composition in other agricultural habitats was most similar to that of urban areas. Although occurrences of Wasmannia auropunctata were similar in cocoa plantations and forests, abundance of Thaumatomyrmex and Typhlomyrmex, generally thought to be rare ants, was relatively high in cocoa plantations. These results, from cocoa plantations with relatively simple shade, demonstrate the importance of cocoa for ant conservation in the Atlantic forest region of Brazil. It is likely that cocoa plantations with a greater number of vegetation strata and higher tree species richness (such as traditional cabruca plantations) provide even more important habitat for ants generally and for ant species of conservation concern.     

Effect of rainfall exclusion on ant assemblages in montane rainforests of Ecuador

Models of global climate change generally predict higher rainfall variability, with more intense rainfall events separated by extended dry periods. We experimentally studied the effects of prolonged droughts on diverse ant assemblages found at three elevations in an Ecuadorian montane rainforest. We hypothesized that most species will be negatively affected directly (physiological stress) or indirectly (less food or suitable nesting resources) by drought. We thus expected a decrease in species richness as well as changes in assemblage composition. As the decrease of moisture content was expected to be more marked above ground than in soil, its impact on ants should differ according to their nesting site (dead wood, leaf litter, soil). After 6-month treatments, dead wood, leaf litter and soil samples were on average 53%, 46% and 4% drier under tents than controls, respectively. The drought did not alter overall species richness in the three nesting situations. However, species composition was significantly modified, mostly in dead wood and in leaf litter. Camponotus in dead wood, Strumigenys in leaf litter and Solenopsis in all three microhabitats were more abundant under tents. In contrast, Pheidole in dead wood, and Pachycondyla in leaf litter, were less abundant than in controls. Similar trends were observed at the three study sites. To conclude, after 6-month droughts dominant ant genera in the assemblages were affected differently. In the longer term, alteration of the rainfall regime is therefore expected to have an important impact on ants, as well as on their ecosystem functions and services, through shifts in species dominance and composition.     

Foliage-dwelling ants in a neotropical savanna: effects of plant and insect exudates on ant communities

Ant dominance in tropical ecosystems can be explained by a capacity to exploit liquid foods such as extrafloral nectaries (EFNs) and secretions from honeydew-producing hemipterans (HPHs). Such nutritious exudates may determine ant distribution in space and shape specialization in ant–plant interactions. We provide a first assessment of how EFNs and HPHs mediate the structure of ant assemblages, ant visitation intensity, and characteristics of ant–plant interaction networks across space in Brazilian “cerrado” savanna. We used arboreal pitfall traps to sample visiting ants in four cerrado localities and recorded the presence of lepidopteran larvae to determine their possible response to ant visitation. Ant species composition and richness did not differ regardless of the presence of liquid rewards on plants, and most network patterns did not show consistent differences. However, in two of the four sites, ant densities were higher on plants with HPHs or EFNs due to increased activity by Camponotus and Pseudomyrmex ants. At these two sites, plants with liquid food sources had a more specific ant assemblage (higher specialization d′) than did plants without resources, and caterpillars were more frequently found on plants with fewer workers of Camponotus and Pseudomyrmex. Plants with HPHs had increased ant visitation and accumulated more ant species than did plants with EFNs or without liquid foods. Ant response to such food sources may thus depend on local conditions and identity of ant species, and may determine how ant assemblages are structured. Results highlight how different patterns of ant visitation to liquid resources can produce distinctive effects on herbivore infestation.     

Analysis of the local ant fauna (Hymenoptera, Formicidae) in Southern Vietnam

The ant fauna of Nam Cat Tien in the southern part of the Cat Tien Biosphere Reserve (Dong Nai Prov., Southern Vietnam) was studied in 2007–2008. The zonal type of vegetation under study is closed deciduous tropical forests dominated by Lagerstroemia spp. in association with Dipterocarpaceae and Fabaceae. The local ant fauna comprises 272 species from 68 genera and 12 subfamilies. The maximum number of species was found in the genera Polyrhachis (31), Camponotus (21), Pheidole (21), Leptogenys (17), and Crematogaster (13). Seven ant genera (Echinopla F. Sm., Indomyrma Brown, Liomyrmex Mayr, Paratopula Wheeler, Proatta For., Protanilla Taylor, and Rotastruma Bolton) are reported from Vietnam for the first time. The ecological pattern of the ant fauna in the main forest biotopes of the study area is considered. In the dipterocarp forests in the central part of the reserve, the complex of stratobiont species was the most diverse. In the bamboo forests, the stratobiont complex is less diverse but the fraction of dendrobionts is greater. The forests with similar layer structure occurring on sand and loamy soils were shown to differ in the species composition of ant assemblages. Repeated population inventories of ants were carried out in 8 model plots of 100 m2 each during the dry and rainy season. The specificity of revealing species of different biomorphs is discussed in the seasonal aspect. The structure of the ant fauna of Nam Cat Tien is compared to that in other territories of the Oriental Region. The zoogeographic unity of the study area and some localities of the Indo-Malayan Subregion (Borneo, Java) is demonstrated.     

Diversity and biogeography of a species‐rich ant fauna of the Australian seasonal tropics

Although ants are an ecologically dominant and extensively studied faunal group throughout the tropics, there is a poor understanding of tropical ant diversity and distribution at large spatial scales. Here we use a collection developed from 3 decades of ant surveys to present the first analysis of ant diversity and biogeography of a large tropical region. Our objective was to document the species richness, composition, and biogeographic distributions of the ant fauna of the 400 000 km² “Top End” of Australia's Northern Territory. The known Top End ant fauna comprises 901 native species from 59 genera. The richest genera are Pheidole (90 species), Melophorus (83), Monomorium (83), Camponotus (71), Meranoplus (63), Polyrhachis (57), Rhytidoponera (50), Tetramorium (43), Cerapachys (32), and Iridomyrmex (31). The fauna is the center of diverse radiations within species‐groups of genera such as Meranoplus, Rhytidoponera, and Leptogenys. It also includes IndoMalayan species that have likely bypassed the normal dispersal route into Australia through Cape York Peninsula in North Queensland. Faunistic similarity with other regions of far northern Australia is associated more with rainfall than with geographic proximity. Most (60%) of Top End ant species have not been recorded elsewhere, and, despite uncertainties relating to species delimitation and sampling intensity, this appears to be a credible estimate of the level of endemism. Such exceptionally high endemism can be attributed to the Top End's geographic isolation from other regions of northern Australia with comparably high rainfall.     

Functional groups and patterns of organization in North American ant communities: a comparison with Australia

Ant distribution and behavioural dominance is examined at nine sites along an elevational gradient (1400–2600 m) in south eastern Arizona, in order to classify North American species according to a functional group scheme used extensively in Australia. The functional groups are then used as a basis for determining patterns of community structure along the environmental gradient, and for comparing community structure between Australia and North America. Quantitative information on species com- position was obtained from pitfall traps, and patterns of ant abundance at tuna baits were used to determine relative behavioural dominance among taxa. A total of eighty-three species from twenty-eight genera was recorded along the elevational gradient, with site species richness ranging from four (high elevation Douglas fir forest) to thirty-three (mid elevation oak–juniper woodland). There was a strong correlation between ant abundance and richness, which was not an artefact of sampling intensity. The most common ants were species of Forelius, Monomorium, Crematogaster and Pheidole at the three desert sites, species of Formica, Pheidole and Crematogaster at the three woodland sites, and species of Prenolepis and Formica at one forest site. No species were abundant at two other forest sites. The most common species in traps also tended to be the most common species at baits. In terms of behavioural dominance, highly competitive ants included species of Solenopsis, Forelius, Monomorium and Liometopum. Species of Pheidole and Crematogaster tended to be moderately competitive, whereas species of Dory- myrmex, Myrmica, Camponotus and Formica (fusca gp) had low competitive ability. On the basis of these results and on published records of other taxa, North American ants were assigned to functional groups as follows (major taxa only given here): Dominant Dolichoderinae—Forelius, Liome- topum; Subordinate Camponotini—Camponotus; Hot Climate Specialists—Pogonomyrmex, Myrmecocystus; Cold Climate Specialists—Formica (rufa, exsecta and microgyna groups), Leptothorax, Stenamma, Lasius, Prenolepis; Cryptic Species—Smithistruma, Solenopsis (subgenus Diplorhop- trum), Acanthomyops; Opportunists—Formica (fusca group), Myrmica, Paratrechina, Dorymyrmex; Generalized Myr- micinae—Pheidole, Crematogaster, Monomorium; Specialist Predators—no major taxa. Functional group composition varied systematically along the elevation gradient: Dominant Dolichoderinae, Generalized Myrà micinae and Hot Climate Specialists were predominant at desert sites; Generalized Myrmicinae and Opportunists were predominant at woodland sites; and Opportunists and Cold Climate Specialists were predominant at forest sites. These patterns are consistent with published studies from elsewhere in North America. Almost all North American taxa can be matched with what appear to be ecologically equivalent taxa in Australia, and biogeographic patterns of functional group composition are broadly similar across the two continents. The major differences are that Australian ant communities are far richer in species, and are almost always dominated by dolichoderines, particularly species of Iridomyrmex. Generalized myrmicines are subdominant to dolichoderines in Australia, but are the behaviourally dominant ants throughout the warmer parts of North America. In cool-temperate North America, species of Formica (especially rufa and exsecta groups) are behaviourally dominant, as they are throughout the Palearctic. Some major features of the North American fauna can be linked to its poor representation of Dominant Dolichoderinae, including (1) the relatively low degree of physiological, morphological and behavioural specialization of Hot Climate Specialists; (2) behavioural dominance by formicines in cool-temperate habitats; and (3) the susceptibility to invasion by behaviourally dominant species such as the imported fire ant Solenopsis invicta and the Argentine ant Linepithema humile.     

Ants of Three Adjacent Habitats of a Transition Region Between the Cerrado and Caatinga Biomes: The Effects of Heterogeneity and Variation in Canopy Cover

Habitat heterogeneity and complexity associated with variations in climatic conditions are important factors determining the structure of ant communities in different terrestrial ecosystems. The objective of this study was to describe the horizontal and vertical distribution patterns of the ant community associated with three adjacent habitats in a transition area between the Cerrado and Caatinga biomes at the Pandeiros River, state of Minas Gerais, Brazil. We tested the following hypotheses: (1) the richness and composition of ant species and functional group structure changes between different habitats and strata; (2) habitats with higher tree species richness and density support higher ant species richness; and (3) habitats with lower variation in canopy cover support higher ant species richness. Sampling was conducted in three adjacent habitats and at three vertical strata. Ant species richness was significantly different among vertical strata. Ant species composition was different among both habitats and vertical strata and functional group structure was divergent among habitats. Partitioning of the diversity revealed that the diversity for the three components was statistically different from the one expected by the null model; α and β ₂ were higher and β ₁ was lower than the values expected by chance. Tree density and variation in canopy cover negatively affected ant species richness. The occurrence of different species and the changing of functional group structures in different habitats and strata suggest an ecological–evolutionary relationship between ants and their habitats and emphasize the need to implement local conservation strategies in the ecotones between biomes.     

Size matters: nest colonization patterns for twig‐nesting ants

相似文献   

Reactions by army ant workers to nestmates having had contact with sympatric ant species

It was recently shown that Pheidole megacephala colonies (an invasive species originating from Africa) counterattack when raided by the army ant, Eciton burchellii. The subsequent contact permits Pheidole cuticular compounds (that constitute the “colony odour”) to be transferred onto the raiding Eciton, which are then not recognised by their colony-mates and killed. Using a simple method for transferring cuticular compounds, we tested if this phenomenon occurs for Neotropical ants. Eciton workers rubbed with ants from four sympatric species were released among their colony-mates. Individuals rubbed with Solenopsis saevissima or Camponotus blandus workers were attacked, but not those rubbed with Atta sexdens, Pheidole fallax or with colony-mates (control lot). So, the chemicals of certain sympatric ant species, but not others, trigger intra-colonial aggressiveness in Eciton. We conclude that prey-ant chemicals might have played a role in the evolution of army ant predatory behaviour, likely influencing prey specialization in certain cases.     

Global phylogenetic structure of the hyperdiverse ant genus Pheidole reveals the repeated evolution of macroecological patterns

Adaptive radiations are of particular interest owing to what they reveal about the ecological and evolutionary regulation of biodiversity. This applies to localized island radiations such as Darwin''s finches, and also to rapid radiations occurring on a global scale. Here we analyse the macroevolution and macroecology of Pheidole, a famously hyperdiverse and ecologically dominant ant genus. We generate and analyse four novel datasets: (i) a robust global phylogeny including 285 Pheidole species, (ii) a global database on regional Pheidole richness in 365 political areas summarizing over 97 000 individual records from more than 6500 studies, (iii) a global database of Pheidole richness from 3796 local communities and (iv) a database of Pheidole body sizes across species. Analysis of the potential climate drivers of richness revealed that the patterns are statistically very similar across different biogeographic regions, with both regional and local richness associated with the same coefficients of temperature and precipitation. This similarity occurs even though phylogenetic analysis shows that Pheidole reached dominance in communities through serial localized radiations into different biomes within different continents and islands. Pheidole body size distributions have likewise converged across geographical regions. We propose these cases of convergence indicate that the global radiation of Pheidole is structured by deterministic factors regulating diversification and diversity.     

Genetic Diversity of Urban <Emphasis Type="Italic">Camponotus</Emphasis> Mayr (Hymenoptera: Formicidae) Ants Revealed by Capture of Alates and DNA Sequencing

The Camponotus Mayr genus of carpenter ants is one of the largest in species number and widely represented in the Neotropical Region. Most species are generalists and capable of exploiting diverse habitats including urban environments. Urban green areas can act as a repository of regional biodiversity, thus we investigated whether this is valid for the largest city in South America. We compared the richness of Camponotus spp. in two green areas in regions with distinct urbanization profiles and also with previous surveys made in smaller cities and in natural areas of the original Atlantic Forest. Besides the usual capture of worker specimens, we included capture of alates to improve the species richness sampling. Morphological identification of Camponotus spp. is challenging, even more when alates are included. To assist in specimen identification, we performed DNA sequencing of mitochondrial and nuclear markers. The richness observed in the less stressed urban area was higher than in the more stressed one. Camponotus spp. reported in natural areas are largely represented in the urban area. DNA sequencing for specimen identification is hampered by the lack of corresponding sequences in the GenBank, but it helped to associate workers and alates of the same species and indicated the existence of cryptic species in the genus. Capture of alates allowed detection of several species for which workers were not sampled; therefore, it is a valuable tool for surveying diversity of Camponotus or other ant taxa with arboreal or hypogeic habits.     

How plants shape the ant community in the Amazonian rainforest canopy: the key role of extrafloral nectaries and homopteran honeydew

Ant-plant interactions in the canopy of a lowland Amazonian rainforest of the upper Orinoco, Venezuela, were studied using a modified commercial crane on rails (Surumoni project). Our observations show a strong correlation between plant sap exudates and both abundance of ants and co-occurrence of ant species in tree canopies. Two types of plant sap sources were compared: extrafloral nectaries (EFNs) and honeydew secretions by homopterans. EFNs were a frequent food source for ants on epiphytes (Philodendron spp., Araceae) and lianas (Dioclea, Fabaceae), but rare on canopy trees in the study area, whereas the majority of trees were host to aggregations of homopterans tended by honeydew-seeking ants (on 62% of the trees examined). These aggregations rarely occurred on epiphytes. Baited ant traps were installed on plants with EFNs and in the crowns of trees from three common genera, including trees with and without ant-tended homopterans: Goupia glabra (Celastraceae), Vochysia spp. (Vochysiaceae), and Xylopia spp. (Annonaceae). The number of ant workers per trap was significantly higher on plants offering one of the two plant sap sources than on trees without such resources. Extrafloral nectaries were used by a much broader spectrum of ant species and genera than honeydew, and co-occurrence of ant species (in traps) was significantly higher on plants bearing EFNs than on trees. Homopteran honeydew (Coccidae and Membracidae), on the other hand, was mostly monopolised by a single ant colony per tree. Homopteran-tending ants were generally among the most dominant ants in the canopy. The most prominent genera were Azteca, Dolichoderus (both Dolichoderinae), Cephalotes, Pheidole, Crematogaster (all Myrmicinae), and Ectatomma (Ponerinae). Potential preferences were recorded between ant and homopteran species, and also between ant-homopteran associations and tree genera. We hypothesize that the high availability of homopteran honeydew provides a key resource for ant mosaics, where dominant ant colonies and species maintain mutually exclusive territories on trees. In turn, we propose that for nourishment of numerous ants of lower competitive capacity, Philodendron and other sources of EFNs might be particularly important.     

A social ethogram of the neotropical arboreal ant Zacryptocerus varians (Fr. Smith)

An ethogram is presented of Zacryptocerus varians, a morphologically advanced member of the ‘turtle ants’ comprising the neotropical ant tribe Cephalotini. The species displays unusual and in one or two cases possibly even unique social behaviours, including the consumption and sharing of infrabuccal pellets, the apparent absence of adult transport, a primarily or exclusively mechanical form of colony defence, and a remarkable form of abdominal trophallaxis. All of these specializations seem to be associated with more primary adaptations by the species to arboreal nesting and scavenging. Among the additional results is the demonstration that the major worker is more specialized as a defensive caste than is the case in certain species of Camponotus and Pheidole.     

Index,Vol. 34, 1999

To investigate whether similar physiognomic areas support similar faunas, the richness, similarity, and community structure of the ant fauna attracted to baits in an area of the Brazilian Cerrado sensu stricto at the core of the domain and in two Cerrado 'islands' (one of sensu stricto and another of 'cerradão') were compared. In each locality, four collecting events were performed (two during the day and two at night) capturing ants attracted to 400 sardine baits (200 in soil, 200 in vegetation). Ants of six subfamilies, 33 genera, and 121 species were identified visiting baits in the three areas (180 species estimated). The most speciose genera were Camponotus (27 species), Pheidole (13), Solenopsis (11), and Crematogaster (8). The similarity values between pair sites can be considered medium in relation to other studies. The highest value was recorded for the core area and the 'island' of Cerrado sensu stricto (Morisita-Horn = 0.57). The two Cerrado 'islands' were found to be 0.44 similar and the core area and the 'cerradão' 0.41 similar. The ordination analysis (non-metric multidimensional scaling) revealed discontinuities in species distributions between areas of Cerrado sensu stricto and 'cerradão,' and distinctive ant faunas relative to the temporal (nocturnal and diurnal) and foraging niches (ground and vegetation). The ant fauna at ground level in the 'cerradão' and Cerrado sensu stricto showed the greatest dissimilarity. The data suggest that areas of Cerrado are characterized by relatively high local ant fauna richness, and that community structure is influenced by the distance between sites and the diversity of vegetation.     

Impact of Flooding on the Species Richness, Density and Composition of Amazonian Litter-Nesting Ants

Litter-nesting ants are diverse and abundant in tropical forests, but the factors structuring their communities are poorly known. Here we present results of the first study to examine the impact of natural variation in flooding on a highly diverse (21 genera, 77 species) litter-nesting ant community in a primary Amazonian forest. Fifty-six 3 × 3 m plots experiencing strong variation in flooding and twenty-eight 3 × 3 m terra firme plots were exhaustively searched for litter-nesting ants to determine patterns of density, species richness and species composition. In each plot, flooding, litter depth, twig availability, canopy cover, plant density, percent soil nitrogen, carbon, and phosphorus were measured. Degree of flooding, measured as flood frequency and flood interval, had the strongest impact on ant density in flooded forest. Flooding caused a linear decrease in ant abundance, potentially due to a reduction of suitable nesting sites. However, its influence on species richness varied: low-disturbance habitat had species richness equal to terra firme forest after adjusting for differences in density. The composition of ant genera and species varied among flood categories; some groups known to contain specialist predators were particularly intolerant to flooding. Hypoponera STD10 appeared to be well-adapted to highly flooded habitat. Although flooding did not appear to increase species richness or abundance at the habitat scale, low-flooding habitat contained a mixture of species found in the significantly distinct ant communities of terra firme and highly flooded habitat.
     

Effects of canopy connectivity on the arboreal ant community in coffee shade trees

Canopy connectivity influences foraging, movement, and competition in arboreal ant communities. Understanding how canopy connectivity affects arboreal ant communities could inform the development of management practices that maximize services from known biocontrol agents. We experimentally manipulated connectivity between the crowns of large shade trees to investigate the effects of canopy connectivity on arboreal ant species richness and composition in a coffee agroecosystem. A linear mixed-effects analysis showed that the number of species observed at baits set in tree crowns increased significantly after the crowns had been connected with nylon ropes. Crowns that were connected increased in similarity of ant species composition, particularly between adjacent connected crowns. Connectivity may increase the number of species present in tree crowns by allowing ants to move and forage in the canopy while bypassing trunks with more aggressive, territorial species such as Azteca sericeasur. Because twig-nesting species in the upper canopy have been shown to act as biocontrol agents of herbivores, an increase in species richness in tree crowns could have positive implications for agricultural pest-control services.     

Comparing the bacterial diversity of acute and chronic dental root canal infections

This study performed barcoded multiplex pyrosequencing with a 454 FLX instrument to compare the microbiota of dental root canal infections associated with acute (symptomatic) or chronic (asymptomatic) apical periodontitis. Analysis of samples from 9 acute abscesses and 8 chronic infections yielded partial 16S rRNA gene sequences that were taxonomically classified into 916 bacterial species-level operational taxonomic units (OTUs) (at 3% divergence) belonging to 67 genera and 13 phyla. The most abundant phyla in acute infections were Firmicutes (52%), Fusobacteria (17%) and Bacteroidetes (13%), while in chronic infections the dominant were Firmicutes (59%), Bacteroidetes (14%) and Actinobacteria (10%). Members of Fusobacteria were much more prevalent in acute (89%) than in chronic cases (50%). The most abundant/prevalent genera in acute infections were Fusobacterium and Parvimonas. Twenty genera were exclusively detected in acute infections and 18 in chronic infections. Only 18% (n = 165) of the OTUs at 3% divergence were shared by acute and chronic infections. Diversity and richness estimators revealed that acute infections were significantly more diverse than chronic infections. Although a high interindividual variation in bacterial communities was observed, many samples tended to group together according to the type of infection (acute or chronic). This study is one of the most comprehensive in-deep comparisons of the microbiota associated with acute and chronic dental root canal infections and highlights the role of diverse polymicrobial communities as the unit of pathogenicity in acute infections. The overall diversity of endodontic infections as revealed by the pyrosequencing technique was much higher than previously reported for endodontic infections.     

Influence of forest type and tree species on canopy ants (Hymenoptera: Formicidae) in Budongo Forest, Uganda

The arboreal ant fauna was investigated in Budongo Forest, a seasonal rain forest in Uganda, using the insecticidal fogging technique. Ants were collected from 61 trees, between 7 and 33 m in height, belonging to four tree species. Trees were growing in adjacent plots of forests characterized by different use and structure: an old primary forest, a primary swamp forest along a small river, and a secondary forest where selective logging was carried out for 30 years. A total number of 37,065 ants, belonging to 161 species in 30 genera were collected. Considering the high number of species found only once, the completeness of the canopy ant fauna was relatively high and of relatively similar magnitude as samples from the Neotropics or the Oriental region. Up to 37 ant species on a single tree, with an average of 18.2 species per tree, were found. Forty-four ant species (28.1%) were found only once, less than ten individuals were found for each of 88 species (54.7%), but 64.0% of all individuals belonged to one of five species. Considering the high numerical dominance of a few ant species like a Pheidole sp., Tetramorium aculeatum (Mayr) and a Crematogaster sp., there is some evidence for an ant mosaic in the lower canopy of the Budongo Forest. Individual numbers of ants were strongly correlated with nests in the fogged tree, though the ants were not homogeneously distributed in the tree crowns. Diversity measures that strongly depend on individual numbers such as the Morisita-Horn index or rarefaction methods were calculated, but results were not concordant with those of incidence-based estimates such as jack-knife calculations. Differences in ant species richness and faunal composition between tree species were low, but more significant between forest types. The ant fauna in the secondary forest was less diverse with 12.6% fewer species compared to the primary forest sites. The average number of ant species per tree was significantly lower in the secondary forest (<20% of the species; F=8.03, df=59, P<0.01) than in the undisturbed forest types. Cataulacus, Leptothorax, Tetraponera, and Polyrhachis, which are typical canopy-dwelling ant genera, had a significantly higher diversity and frequency in the two primary forest types (F=4.17, df=53, P<0.05). Secondary forest trees are often younger, lacking dead branches and epiphytes which are important requisites for ant colonization on trees.     

Rainforest ants of the Tiwi Islands: a remarkable centre of endemism in Australia’s monsoonal tropics

The small and isolated rainforest patches that are embedded in the predominantly savanna landscape of Australia’s monsoonal tropics support a highly distinctive and biogeographically significant ant fauna. This fauna features shade-tolerant taxa of Indo-Malayan origin, in contrast to the arid-adapted, endemic Australian taxa that dominate the surrounding savanna. The Tiwi Islands north of Darwin in the Northern Territory (NT) receive the highest mean annual rainfall (up to 2,000 mm) in monsoonal Australia, and have a particularly extensive rainforest estate that has been poorly surveyed for invertebrates. Here we describe results from intensive ant surveys at 17 sites representing the full range of Tiwi rainforest types, using subterranean traps, Winkler sacs, pitfall traps and arboreal traps, supplemented by opportunistic hand collections. Our surveys yielded a total of 87 species from 37 genera, with the richest genera being Pheidole (9 species collected), Polyrhachis (8), Camponotus (5), Rhytidoponera (5) and Strumigenys (5). The overall structure and diversity of the Tiwi rainforest fauna is comparable to that of rainforest ant faunas on the Australian mainland. However, the species have exceptional biogeographic significance. At least 21 species across 12 genera have apparently never previously been collected, three species from subcoastal northeastern Australia are recorded for the first time in the NT, and the genera Mesoponera and Onychomyrmex are documented for the first time in the NT. There was a very low incidence of exotic species, which further highlights the conservation values of this remarkable fauna.