Dominance-diversity relationships in ant communities differ with invasion.

The relationship between levels of dominance and species richness is highly contentious, especially in ant communities. The dominance-impoverishment rule states that high levels of dominance only occur in species-poor communities, but there appear to be many cases of high levels of dominance in highly diverse communities. The extent to which dominant species limit local richness through competitive exclusion remains unclear, but such exclusion appears more apparent for non-native rather than native dominant species. Here we perform the first global analysis of the relationship between behavioral dominance and species richness. We used data from 1,293 local assemblages of ground-dwelling ants distributed across five continents to document the generality of the dominance-impoverishment rule, and to identify the biotic and abiotic conditions under which it does and does not apply. We found that the behavioral dominance-diversity relationship varies greatly, and depends on whether dominant species are native or non-native, whether dominance is considered as occurrence or relative abundance, and on variation in mean annual temperature. There were declines in diversity with increasing dominance in invaded communities, but diversity increased with increasing dominance in native communities. These patterns occur along the global temperature gradient. However, positive and negative relationships are strongest in the hottest sites. We also found that climate regulates the degree of behavioral dominance, but differently from how it shapes species richness. Our findings imply that, despite strong competitive interactions among ants, competitive exclusion is not a major driver of local richness in native ant communities. Although the dominance-impoverishment rule applies to invaded communities, we propose an alternative dominance-diversification rule for native communities.

Climate mediates the effects of disturbance on ant assemblage structure.

Many studies have focused on the impacts of climate change on biological assemblages, yet little is known about how climate interacts with other major anthropogenic influences on biodiversity, such as habitat disturbance. Using a unique global database of 1128 local ant assemblages, we examined whether climate mediates the effects of habitat disturbance on assemblage structure at a global scale. Species richness and evenness were associated positively with temperature, and negatively with disturbance. However, the interaction among temperature, precipitation and disturbance shaped species richness and evenness. The effect was manifested through a failure of species richness to increase substantially with temperature in transformed habitats at low precipitation. At low precipitation levels, evenness increased with temperature in undisturbed sites, peaked at medium temperatures in disturbed sites and remained low in transformed sites. In warmer climates with lower rainfall, the effects of increasing disturbance on species richness and evenness were akin to decreases in temperature of up to 9°C. Anthropogenic disturbance and ongoing climate change may interact in complicated ways to shape the structure of assemblages, with hot, arid environments likely to be at greatest risk.

Dataset of long-term monitoring of ground-dwelling ants (Hymenoptera: Formicidae) in the influence areas of a hydroelectric power plant on the Madeira River in the Amazon Basin.

BACKGROUND: Biodiversity loss is accelerating rapidly in response to increasing human influence on the Earth's natural ecosystems. One way to overcome this problem is by focusing on places of human interest and monitoring the changes and impacts on the biodiversity. This study was conducted at six sites within the influence area of the Santo Antônio Hydroelectric Power Plant in the margins of the Madeira River in Rondônia State. The sites cover a latitudinal gradient of approximately 100 km in the Brazilian Amazon Basin. The sampling design included six sampling modules with six plots (transects) each, totaling 30 sampling plots. The transects were distributed with 0 km, 0.5 km, 1 km, 2 km, 3 km and 4 km, measured perpendicularly from the river margin towards the interior of the forest. For sampling the ground-dwelling ants, the study used the ALL (ants of the leaf litter) protocol, which is standardized globally in the inventories of ant fauna. For the purpose of impact indicators, the first two campaigns (September 2011 to November 2011) were carried out in the pre-filling period, while campaigns 3 to 10 (February 2012 to November 2014) were carried out during and after the filling of the hydroelectric reservoir. A total of 253 events with a total of 9,165 occurrences were accounted during the monitoring. The ants were distributed in 10 subfamilies, 68 genera and 324 species/morphospecies. The impact on ant biodiversity during the periods before and after filling was measured by ecological indicators and by the presence and absence of some species/morphospecies. This is the first study, as far as we know, including taxonomic and ecological treatment to monitor the impact of a hydroelectric power plant on ant fauna. NEW INFORMATION: Until recently, most studies conducted on hydroelectric plants, located in the Amazon Basin, were carried out after the implementation of dams in order to assess their impacts on the environment and biodiversity (Benchimol and Peres 2015, Latrubesse et al. 2017, Sá-Oliveira et al. 2015). Recent studies on dam impacts have begun to be conducted prior to dam implementation (e.g. Bobrowiec and Tavares 2017, Fraga et al. 2014, Moser et al. 2014), thus providing a better overview of the impact and a better assessment of its magnitude.

Combining Taxonomic and Functional Approaches to Unravel the Spatial Distribution of an Amazonian Butterfly Community.

This study investigated the spatial distribution of an Amazonian fruit-feeding butterfly assemblage by linking species taxonomic and functional approaches. We hypothesized that: 1) vegetation richness (i.e., resources) and abundance of insectivorous birds (i.e., predators) should drive changes in butterfly taxonomic composition, 2) larval diet breadth should decrease with increase of plant species richness, 3) small-sized adults should be favored by higher abundance of birds, and 4) communities with eyespot markings should be able to exploit areas with higher predation pressure. Fruit-feeding butterflies were sampled with bait traps and insect nets across 25 km(2) of an Amazonian ombrophilous forest in Brazil. We measured larval diet breadth, adult body size, and wing marking of all butterflies. Our results showed that plant species richness explained most of the variation in butterfly taxonomic turnover. Also, community average diet breadth decreased with increase of plant species richness, which supports our expectations. In contrast, community average body size increased with the abundance of birds, refuting our hypothesis. We detected no influence of environmental gradients on the occurrence of species with eyespot markings. The association between butterfly taxonomic and functional composition points to a mediator role of the functional traits in the environmental filtering of butterflies. The incorporation of the functional approach into the analyses allowed for the detection of relationships that were not observed using a strictly taxonomic perspective and provided an extra insight into comprehending the potential adaptive strategies of butterflies.

A new species of Simopelta (Hymenoptera: Formicidae: Ponerinae) from Brazil and Costa Rica.

The genus Simopelta consists of 21 described species restricted to Central America and South America. The present study describes a new cryptobiotic species, Simopelta anomma sp. nov.. The new species is blind, possesses a 3-segmented antennal club, and has the midtibia with several stout setae, a combination of characters unique within the genus. Moreover, some traits of this species require broadening the definition of the genus. The discovery of S. anomma sp. nov. suggests that many undiscovered species, some of which may be important for understanding ant evolution, remain hidden below ground in Neotropical rainforests.

Diversity of parasitoid wasps in conventional and organic guarana (Paullinia cupana var. sorbilis) cultivation areas in the Brazilian Amazon

We surveyed parasitoid wasps (Hymenoptera) in two guarana plantations in the central Brazilian Amazon (one conventionally, and one organically managed), as well as in adjacent forest and edge areas between crop and forest. We evaluated differences between management systems in parasitoid diversity and abundance, and assessed the importance of the surrounding matrix as a source of parasitoid wasps for guarana cultivation. Parasitoid wasp richness, abundance and taxonomic composition (at family level) were compared between plantations, and among habitats within plantations. Wasps were sampled using Malaise and Moericke traps. A total of 25,951 parasitoid wasps (10,828 in the conventional, and 15,123 in the organic crop area) were collected, and were distributed in 11 superfamilies and 38 families. In the conventional management area, the greatest abundance and richness of parasitoids were recorded in the adjacent forest, while, in the organic management area, the greatest abundance and richness were recorded in the crop-forest edge. Parasitoid wasp family richness was not influenced by management system and habitat but varied significantly between trap types. Average wasp abundance varied significantly between management systems. The presence of adjacent forest in both cultivation areas likely contributed to a greater abundance and richness of parasitoid wasps, showing the importance of preserving forest areas near the plantations. (AU)