The spatial distributions of many tropical arboreal ant species are often arranged in a mosaic such that dominant species have mutually exclusive distributions among trees. These dominant species can ...also mediate the structure of the rest of the arboreal ant community. Little attention has been paid to how diet might shape the effects of dominant species on one another and the rest of the ant community. Here, we take advantage of new information on the diets of many tropical arboreal ant species to examine the intra- and inter-guild effects of dominant species on the spatial distribution of one another and the rest of the tropical arboreal ant community in a cocoa farm in Bahia, Brazil. Using null model analyses, we found that all ant species, regardless of dominance status or guild membership, co-occur much less than expected by chance. Surprisingly, the suite of five dominant species showed random co-occurrence patterns, suggesting that interspecific competition did not shape their distribution among cocoa trees. Across all species, there was no evidence that competition shaped co-occurrence patterns within guilds. Co-occurrence patterns of subordinant species were random on trees with dominant species, but highly nonrandom on trees without dominant species, suggesting that dominant species disassemble tropical arboreal ant communities. Taken together, our results highlight the often complex nature of interactions that structure species-rich tropical arboreal ant assemblages.
Tropical forest canopies house most of the globe's diversity, yet little is known about global patterns and drivers of canopy diversity. Here, we present models of ant species density, using climate, ...abundance and habitat (i.e. canopy versus litter) as predictors. Ant species density is positively associated with temperature and precipitation, and negatively (or non-significantly) associated with two metrics of seasonality, precipitation seasonality and temperature range. Ant species density was significantly higher in canopy samples, but this difference disappeared once abundance was considered. Thus, apparent differences in species density between canopy and litter samples are probably owing to differences in abundance–diversity relationships, and not differences in climate–diversity relationships. Thus, it appears that canopy and litter ant assemblages share a common abundance–diversity relationship influenced by similar but not identical climatic drivers.
Messor nests in Iranian steppe rangelands can be so large that they are visible from space. When compared with reference soils, nest soil is higher in nutrients and lower in pH. Ant nests also ...homogenise the nutrients throughout the upper soil profile, although this effect diminished when nests are abandoned. The denuded circles around nests are surrounded by rings of vegetation that differ in species composition from that of the surrounding vegetation, while abandoned nests are colonized by a different range of plant species. Data on the density and abundance of Messor cf. intermedius nests indicate that the soil in less than 1% of the area is impacted, although the cumulative effect of so many nests influences the plant species and vegetation structure of the region. The data indicate the importance of these ants in altering soil chemical composition and plant diversity, which could have flow-on effects to the diversity of animals.
Taxonomic impediments require us to know if simpler approaches such as using higher taxa or habitat surrogates can help assess the needs of invertebrates when managing forests. This study tests ...whether higher taxon (families for species) and habitat (vegetation structure for species and families) surrogates might assist in determining the effects of prescribed burning on spiders. Spiders were sampled at sites representing a chronosequence of increasing ages since burning (0, 3, 6 and 9 years) by pitfall trapping and vacuuming from understorey vegetation in the South-west Botanical Province of Australia; a global biodiversity hotspot. Reassembly followed a similar pattern for both the richness of species and families. Immediately following burning, mean richness of families and species was low (8.75 and 14.5, respectively). By 3 years, however, there were significant increases in familial and species richness (13.25 and 23.75, respectively). Thereafter, taxon richness remained constant. Multiple regressions suggested habitat variables potentially influencing family and species richness were litter depth, bare ground (%), the density of dead vegetation (0–100
cm high), and the density of live vegetation (40–140
cm). The first three of these variables correlated significantly with time since burning, suggesting these components of habitat structure are useful predictors of taxon richness for spiders following fire. For assemblage composition, the congruence in post-fire response patterns between taxonomic ranks was highly significant, although the amount of variation explained was low (Rho
<
0.55). In the first 9 years post-fire, there was a significant shift in the taxonomic composition of spiders at family, but not specific, rank. Family composition at recently burnt sites differed significantly from that at sites burnt 9 years previously. Correlated with assemblage composition were litter depth, bare ground, and the density of live vegetation (0–40
cm above the ground). However, the best correlation obtained by any combination of habitat variables with assemblage composition (Rho
<
0.317) was less than that obtained by using family level data. We conclude, therefore, that where resources are limited and there is a need to determine the effects of forest management practices on invertebrates using surrogates, identifying spiders to higher taxa is better than relying on habitat structure.
In order to better understand the relationship between reserve design and the species represented by such designs, we examined the effectiveness of the Western Australian reserve system for ...conserving angiosperm diversity, and examined the characteristics of those species conserved. We overlayed species distribution data for 14 plant lineages with the distribution of the reserve system (8.5% of the State's area) and identified the species that remained unprotected. We found that, depending upon the method employed, between 174 (5.7%) and 570 (18.7%) of species were not included within the reserve system. Two main unprotected regions were identified, one of which was also a centre of high diversity. Geographical range sizes of unprotected species were six times smaller than those species that were protected, while species richness of small-ranged endemic species coincided with general patterns of species richness. At the level of Western Australia's bioregions we found that conservation effectiveness was most dependent on characteristics of the reserve system rather than characteristics (size and positioning) of species ranges. At this scale, the most effective way to conserve more species in Western Australia would be to conserve more land, while conservation would be most successful in a uniformly dispersed reserve system. Our results highlight the fact that reserve systems may take on two design approaches based on scale--at continental scales, reserves should be clustered around the hotspots of endemic species, while within regions, an evenly distributed reserve system will most adequately sample species.
Understanding trends in assemblage composition of key invertebrate groups can provide important insight into the 'condition' of, or changes in, the environment. Species density, abundance and ...composition of Hemiptera (true bugs) were assessed in jarrah (Eucalyptus marginata) forest and a chronosequence of restored bauxite mine pits near Boddington, Western Australia, in order to evaluate how restoration was progressing. A significant difference was uncovered for hemipteran species density between the youngest restored treatment and forest. In contrast, hemipteran composition was distinct between the forest and all restored treatments. Hemipteran composition was associated with the presence of the plant species Conostylis setigera and Trichocline spathulata, and plant structure between 160-180cm and 260-280, plus soil pH. Restoration was successful in returning Hemiptera with respect to species density, but restoration was yet to attain a similar composition of Hemiptera to that of unmined forest, despite some of the restored sites being almost 20 years old. These results are similar to those of other studies that have assessed the response of Hemiptera to disturbance, and highlight the need to wait for considerable periods in order to achieve restoration goals. This study also confirms the utility of Hemiptera as bioindicators of environmental 'condition' and change.
Although Merostachys fischeriana is very abundant in the Brazilian Atlantic Rainforest, little attention has been paid to the biological interactions with other animals. The present study describes ...some of the interactions between ants and this bamboo species. The experiment was carried out in a fragment of a montane tropical forest in the Parque Estadual do Itacolomi, near Ouro Preto, MG, Brazil. Thirty culms of bamboo were randomly collected. The ants were obtained by direct collection from nodes and internodes. Morphometric variables of the bamboo were recorded for characterization of potential ant habitat. Merostachys fischeriana grows in rosettes as a thin bamboo (average = 1,0 cm; se = 0,27; n = 20) and is tall enough to reach the upper canopy of this low forest (average = 9,1 m; se = 2,72; n = 20). Fifteen ant species were sampled. Brachymyrmex heeri Forel was the most abundant in the nodes, while Camponotus crassus Mayr (Hymenoptera: Formicidae) was the most abundant in the internodes. The composition of the species that inhabit the internodes was different from the composition in the node (Q-test: Q = 3,76; P = 0,05). The level of occupation was defined by the number of holes (F = 10,33; P < 0,01), the number of internodes in the canopy (F = 6,84; P = 0,01) and the length of the culm (F = 7,52; P = 0,01). The plant's morphology allowed the occurrence of additional species of ants in the canopy and influenced the composition of the entire ant assemblage.
Resultado do projeto "Rede Multidisciplinar de Estudos sobre Formigas Poneromorfas do Brasil", o livro apresenta um conjunto de estudos originais ou revisões bibliográficas que focalizam o ...comportamento, desenvolvimento e contribuições das formigas poneromorfas para o ecossistema.
Restoring disturbed lands is essential for conserving biodiversity. In floristically diverse regions, restoring all plant species following anthropogenic disturbance is financially costly and it is ...unknown if this can be achieved. However, re-creating faunal habitat may not require reinstating all plant species if there is a high degree of redundancy. Here, we assess whether there is redundancy among a subset of native plant species chosen to restore fauna habitat following a severe disturbance. Additionally, we determine if reestablished plants support similar faunal assemblages as the same plant species in less disturbed forest. We sampled plant-dwelling Hemiptera from 1,800 plants across 16 species. We found 190 species of Hemiptera, with most plant species in the forest having distinct hemipteran assemblages. Returning these plant species to areas undergoing restoration reinstated 145 hemipteran species, including the dominant species. Recalcitrant plant species (difficult to propagate and reestablish in restored areas) had different hemipteran assemblages from all other species. There was only one plant species that did not have a distinct assemblage and thus was considered redundant. We conclude that there is little redundancy in this study. For plant-dwelling Hemiptera (with good powers of dispersal) to recolonize restored areas, restoration efforts will need to reinstate at least 13 of the 16 species of host plant of appropriate age and structure. Consequently, to meet the goal of restoring fauna habitat when there is no knowledge of which plant species are redundant, restoration projects should aim to reinstate all plant species present in less disturbed reference areas.
Cerrado is a biome whose evolution is intimately influenced by constant fire events. Although many species are capable of dealing with this predictable impact, many others may be negatively affected, ...resulting in community changes after fire. Using ants as bioindicators of changes in biodiversity and environmental conditions, this study evaluated the effects of fire in two Cerrado vegetation types: "cerrado" sensu stricto, a xeric savanna, and wetland "veredas", a mesic vegetation on floodable soils, where water concentrates and ultimately flows towards rivers. We examined the effects of fire on both habitats in two independent sites, but with special consideration to the wetlands, which are not fully adapted to fire. In the cerrado, a similar result was observed for Crematogaster nr. obscurata, which disappeared after fire. The wetland vegetation having little adaptation to fire, plus low resilience in the ant community resulted in a severely changed fauna, both in guild predominance and species composition, and return to an original state is uncertain.
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