Few Ant Species Play a Central Role Linking Different Plant Resources in a Network in Rupestrian Grasslands

Organization of the macroinvertebrate community in a tropical annual agroecosystem into modules

The structure of macroinvertebrate communities in agroecosystems has been assumed to be modular and organized around key herbivore pests. We characterized the macroinvertebrate community in the annual organic brassica agroecosystem in tropical central Brazil to determine if the community was a random assemblage of independent populations or was organized into repeatable multi-species components. We sampled 36 macroinvertebrate taxa associated with six organic brassica farms at biweekly intervals during the dry season during two years in the Distrito Federal, Brazil. We used an unconstrained ordination based on latent variable modeling (boral) with negative binomial population counts to analyze community composition independent of variation in sample abundance. We evaluated observed community structure by comparing it with randomized alternatives. We found that the community was not a random assemblage and consistently organized itself into two modules based around the major herbivores; one with lepidoptera and whiteflies and their associated natural enemies which was gradually replaced during the season by one with brassica aphids, aphid parasitoids and coccinellids. This analysis suggests that the historical and present-day focus on pest herbivores and their associated species in agroecosystems may be justified based on community structure.

Changes in the core species of the ant-plant network of oak forest converted to grassland: replacement of its ant functional groups

Land-use change in terrestrial environments is one of the main threats to biodiversity. The study of ant-plant networks has increased our knowledge of the diversity of interactions and structure of these communities; however, little is known about how land-use change affects ant-plant networks. Here we determine whether the change in land use, from native oak forest to induced grassland, affected the network properties of ant-plant networks in a temperate forest in Mexico. We hypothesize that the disturbed vegetation will be more nested and generalized due to the addition of generalist species to the network. The oak forest network comprises 47 plant species and 11 ant species, while the induced grassland network has 35 and 13, respectively. Floral nectar was the resource used most intensely by the ants in both vegetation types. The ant-plant network of the induced grassland was significantly more nested and generalist than that of the oak forest; however, none of the networks were nested when considering the frequency of interaction. In both vegetation types, the ants were more specialized than the plants, and niche overlap was low. This could be related to the dominant species present in each type of vegetation: Prenolepis imparis in the oak forest and Camponotus rubrithorax in the grassland. The central core of cold climate ant species in the oak forest was replaced by a central core of subordinate Camponotini and tropical specialists in the induced grassland. These results suggest that the increase in nestedness and generalization in the grassland may be related to the loss of the cold climate specialists from the core of the oak forest network. Our findings provide evidence that land-use change increases the level of generalization in the ant-plant interaction networks of temperate forests.

Gender differences in traditional knowledge of useful plants in a Brazilian community

Genders differ in traditional ecological knowledge (TEK) about plants, but how gender influences TEK sharing is still poorly understood. Here, we examined how gender is associated with the diversity, transmission, and structure of TEK. We tested whether women and men differ in terms of plant knowledge (species richness, α-diversity), knowledge heterogeneity (β-diversity), and in the structure of social-ecological networks they form. The study was carried out in a suburban community in the city of Ouro Preto, Southeastern, Brazil. Using the snow-ball technique, semi-structured interviews, guided tours, and participant observation, we gathered information from 33 women and 33 men in the community. We collected information about their culture, social-economic profiles, and plant knowledge from which we identified 291 plant species in 10 use categories. Overall, our results indicated that the cognition and sharing of ethnobotanical knowledge are structured by gender. Women rated better in their plant knowledge repertory (greater α-diversity), while plant knowledge among men was more heterogeneous (greater β-diversity), suggesting less information sharing among them. We observed that the network among women is more connected, exhibited greater information sharing, with a greater number of central individuals, who likely provide the cohesion and maintenance of TEK in the community. Our findings indicate how social-ecological networks can provide insights and information to unveil social patterns of knowledge transmission. Understanding how TEK is fostered and shared among community members will favor better planning of ethnobotanical studies, as well as inform decision-makers about strategies for the conservation of plant TEK.

Volatile constituents of Eupatorieae (Asteraceae). Compositional multivariate analysis of volatile oils from Southern Brazilian species in the subtribe Disynaphiinae

Volatile oils (VOs) obtained from the aerial parts of species from the Disynaphiinae subtribe (genera Acanthostyles, Campovassouria, Disynaphia, Grazielia, Raulinoreitzia, and Symphyopappus) of Eupatorieae (Asteraceae) collected in Rio Grande do Sul, southern Brazil, were characterized using GC-MS. The yield of VOs relative to fresh material ranged from 0.2 to 1.7% between the Disynaphiinae subtribe samples (Acanthostyles buniifolius, Campovassouria cruciata, Disynaphia ericoides, D. ligulifolia, D. spathulata, Symphyopappus casarettoi, S. reticulatus, S. itatiayensis, Grazielia gaudichaudieana, G. intermedia, G. nummularia, G. serrata, Raulinoreitzia crenulata, and R. tremula). The VOs in this subtribe were mainly composed of terpene compounds. Compositional multivariate analysis demonstrated clustering between the samples of Grazielia and Raulinoreitzia on one side, which contain relatively higher proportions of monoterpenes, and Disynaphia and Campovassouria, which contain more oxygenated sesquiterpenes. The samples of Symphyopappus and Acanthostyles, which contain more sesquiterpene hydrocarbons, were located between these two main groups. Multivariate analysis accounting for the recent proposals of subtribal recircumscription of Eupatorieae was also performed. The odd chemistry of S. itatiayensis was in accordance with the recent attempts to exclude it from the genus Symphyopappus.

High fidelity defines the temporal consistency of host-parasite interactions in a tropical coastal ecosystem

Host-parasite interactions represent a selective force that may reduce hosts’ lifespan, their reproductive success and survival. Environmental conditions can affect host-parasite communities, leading to distinct patterns of interactions with divergent ecological and evolutionary consequences for their persistence. Here, we tested whether climatic oscillation shapes the temporal dynamics of bird-haemosporidian associations, assessing the main mechanisms involved in the temporal dissimilarity of their interactions’ networks. For two years, we monthly sampled birds in a tropical coastal ecosystem to avian malaria molecular diagnosis. The studied networks exhibited high specialization, medium modularity, with low niche overlap among parasites lineages. Moreover, alpha and β-diversity of hosts, parasites and their interactions, as well as the structure of their networks were temporally consistent, i.e., stable under fluctuations in temperature or precipitation over seasons. The structure and temporal consistency of the studied antagonistic networks suggest a high fidelity between partners, which is likely relevant for their evolutionary persistence.

Revisiting ecological dominance in arboreal ants: how dominant usage of nesting resources shapes community assembly

Ecologically dominant species can shape the assembly of ecological communities via altering competitive outcomes. Moreover, these effects may be amplified under limited niche differentiation. Nevertheless, the influences of ecological dominance and niche differentiation on assembly are rarely considered together. Here, we provide a novel examination of dominance in a diverse arboreal ant community, defining dominance by the prevalent usage of nesting resources and addressing how it influences community assembly. We first used a series of quantitative observational and experimental studies to address the natural nesting ecology, colony incidence on surveyed trees, and level of dominance over newly available nesting resources by our focal species, Cephalotes pusillus. The experimental studies were then used further to examine whether C. pusillus shapes assembly via an influence on cavity usage by co-occurring species. C. pusillus was confirmed as a dominant user of cavity nesting resources, with highly generalized nesting ecology, occupying about 50% of the trees within the focal system, and accounting for more than a third of new cavity occupation in experiments. Our experiments showed further that the presence of C. pusillus was associated with modest effects on species richness, but significant decreases in cavity-occupation levels and significant shifts in the entrance-size usage by co-occurring species. These results indicate that C. pusillus, as a dominant user of nesting resources, shapes assembly at multiple levels. Broadly, our findings highlight that complex interactions between a dominant species and the resource-usage patterns of other species can underlie species assembly in diverse ecological communities.

Construction, comparison and evolution of networks in life sciences and other disciplines

Network approaches have become pervasive in many research fields. They allow for a more comprehensive understanding of complex relationships between entities as well as their group-level properties and dynamics. Many networks change over time, be it within seconds or millions of years, depending on the nature of the network. Our focus will be on comparative network analyses in life sciences, where deciphering temporal network changes is a core interest of molecular, ecological, neuropsychological and evolutionary biologists. Further, we will take a journey through different disciplines, such as social sciences, finance and computational gastronomy, to present commonalities and differences in how networks change and can be analysed. Finally, we envision how borrowing ideas from these disciplines could enrich the future of life science research.

Does fire disturbance affect ant community structure? Insights from spatial co-occurrence networks

The coexistence of several species involves a complex mix of positive and negative interactions that can be represented as networks. As much as other ecological features, patterns of multispecies co-occurrence are susceptible to anthropogenic disturbance. In ant communities, wildfires may enhance competitive interactions by benefiting active, aggressive species, and by increasing encounter probabilities through decreased space availability. We explored ant co-occurrence patterns by analysing the macro and microscopic structure of their interaction networks in burned and unburned habitats. We built co-occurrence networks using significant aggregations and segregations between species pairs as positive and negative interactions, respectively. We described aggregate network properties and microscopic structural changes by comparing species and interactions turnover between burned and unburned sites. We found no differences in the macroscopic structure of co-occurrence networks between different fire regimes. However, we detected changes in the composition of both species and negative interactions. Interaction turnover between networks of different habitats was mostly explained by rewiring of interactions between shared species rather than by species replacement. Our results reflected changes in ant communities in response to fire although there were no changes in global structural patterns. These changes in species and negative interactions suggest modifications in species roles translated into changes in the spatial distribution of ant species. The analysis of species co-occurrence networks is a useful tool to detect and visualize patterns in ant communities and to understand the mechanisms underlying the effects of disturbance on biodiversity.

Handling by avian frugivores affects diaspore secondary removal

The balance between the costs and benefits of fleshy fruit production depends on the feeding behavior of their seed dispersers, which might effectively disperse seeds to farther areas or drop beneath parent plants some diaspores they handle during frugivory bouts. Nevertheless, the consequences of variation in fruit handling by primary seed dispersers on the secondary removal of diaspores remains poorly understood. We conducted a field study to determine how variation in fruit handling by avian frugivores affects short-term secondary removal of Miconia irwinii (Melastomataceae) diaspores by the ground-dwelling fauna in campo rupestre vegetation, southeastern Brazil. We conducted factorial experiments manipulating: (1) different outcomes of primary fruit/seed removal by birds, (2) distances of diaspore deposition from conspecifics, and (3) the access of ants and vertebrates to diaspores. We showed that secondary removal of diaspores was highly variable at the population scale, with an overall low removal rate by the ground-dwelling fauna (13% seeds, 19% fruits). However, we found that gut-passed seeds embedded in bird feces were less removed than seeds expelled from fruits. Gut-passed seeds were more likely to be removed by ant species acting as secondary dispersers, whereas pulp-free seeds dropped by birds were likely to interact with potential seed predators, including ants and rodents. We found no clear effect of dispersal from parent plant vicinity on seed removal, but fruit removal was significantly higher near parent plants. Partially defleshed fruits were more removed than intact fruits. The removal of fruits by ant and vertebrate rescuers, including lizards and birds, might reduce the costs of interactions with less effective dispersers that drop partially defleshed fruits under parent plants. Our study highlights that variation in fruit handling by primary avian seed dispersers mediate subsequent interactions among discarded diaspores and ground-dwelling animals, potentially affecting final seed fates. Moreover, we argue that escape-related benefits of dispersal can be contingent on how primary dispersers handle and discard seeds.