High niche partitioning promotes highly specialized, modular and non‐nested florivore–plant networks across spatial scales and reveals drivers of specialization

Ecological networks in savannas reflect different levels of hydric stress in adjacent palm swamp forest ecosystems

Palm swamp forests are wetland ecosystems typical of the Brazilian Cerrado, which in recent decades have undergone intense changes due to land use alterations and climate change. As a result of these disturbances, many palm swamps have been experiencing significant drying, which can also affect adjacent vegetation. In the present study, we evaluated whether the drying of palm swamps affects the structure of plant-herbivore networks located in adjacent savanna areas in Brazil. Our results show that savanna areas adjacent to dry zones of palm swamps have fewer interactions, fewer interacting species, and a less specialized topology, which corroborates our expectations. Our findings indicate that the drying of palm swamps also has propagated impacts on adjacent savanna vegetation, impairing more specialized interactions in these environments. On the other hand, contrary to expectations, plant-herbivore networks in dry zones displayed higher modularity, lower nestedness and lower robustness than those in wet zones, suggesting that in dry environments, species tend to compartmentalize their interactions, even with lower interaction specialization. This is the first study to investigate the impacts of environmental drying on the structure of plant-herbivore networks in tropical ecosystems, highlighting the complexity of these effects and their differential impact on specialized and generalized interactions. Understanding these dynamics is crucial for developing effective conservation and management strategies in the face of ongoing environmental changes.

Systematics and spatio-temporal evolutionary patterns of the flavopilosa group of Drosophila (Diptera, Drosophilidae)

The Drosophila flavopilosa group comprises morphologically cryptic species that are ecologically restricted to feeding, breeding and ovipositing on flowers of Cestrum and Sessea (Solanaceae). Previous studies confirmed the monophyly of the group and the success of DNA barcoding in identifying a subset of its species, but several others remain yet to be evaluated. Furthemore, the taxonomy of the group remains incomplete, with only nine of the 17 species assigned to subgroups. Here, we accessed the phylogenetic relationships and spatio-temporal evolutionary patterns of the flavopilosa group based on a mitochondrial and two nuclear genes, providing the first molecular support to the subdivision of the group and suggesting a new taxonomic scheme for its species. Barcoding proved to be an effective tool, as all species were reciprocally monophyletic and different analyses of species delimitation yielded congruent results. The close relationship of D. flavopilosa with D. cestri and D. cordeiroi was strongly supported, suggesting that the latter should be placed in the flavopilosa subgroup together with the first. Furthermore, D. mariaehelenae was positioned as sister to D. incompta, supporting its inclusion in the nesiota subgroup. Despite new taxonomic assignments, the synapomorphic status of the diagnostic characters proposed for both subgroups was supported. Based on them, each of the remaining species were placed into one of both subgroups. Divergence time estimates suggest that their diversification coincided with the divergence of Sessea and Cestrum, providing an interesting case of coevolution.

A new species of the Drosophila tripunctata group (Diptera: Drosophilidae) associated with fallen flowers of six Lecythidaceae species in the Amazon Rainforest

The tripunctata group falls under the subgenus Drosophila Falln, 1823 of the genus Drosophila Falln, 1823, and is composed of four subgroups and 17 species not assigned to subgroups. This group is widely distributed throughout tropical regions and is predominantly found in preserved forest environments. With a predicted high number of cryptic species, the occurrence of intraspecific morphological polymorphisms made it difficult to establish lines in the laboratory. The capture of males for comparison of the terminalia makes it hard to identify and delimit species; however, these difficulties can be overcome through the use of techniques such as searching for species in naturally occurring places, establishing isofemale lines in the laboratory, or using molecular techniques. In this work, we search for imagoes of species of the tripunctata group over present fallen flowers of the Lecythidaceae on the ground of the Amazon rainforest. The collected individuals were morphologically and molecularly analyzed. This species is described here under the binomial Drosophila lecythus sp. nov.

Interaction fidelity is less common than expected in plant-pollinator communities

Pairs of plants and pollinators species sometimes consistently interact throughout time and across space. Such consistency can be interpreted as a sign of interaction fidelity, that is a consistent interaction between two species when they co-occur in the same place. But how common interaction fidelity is and what determines interaction fidelity in plant-pollinator communities remain open questions. We aim to assess how frequent is interaction fidelity between plants and their pollinators and what drives interaction fidelity across plant-pollinator communities. Using a dataset of 141 networks around the world, we quantify whether the interaction between pairs of plant and pollinator species happens more ('interaction fidelity') or less ('interaction avoidance') often than expected by chance given the structure of the networks in which they co-occur. We also explore the relationship between interaction fidelity and species' degree (i.e. number of interactions), and the taxonomy of the species involved in the interaction. Our findings reveal that most plant-pollinator interactions do not differ from random expectations, in other words show neither fidelity nor avoidance. Out of the total 44,814 co-occurring species pairs we found 7,877 unique pair interactions (18%). Only 551 (7%) of the 7,877 plant-pollinator interactions did show significant interaction fidelity, meaning that these pairs interact in a consistent and non-random way across networks. We also find that 39 (0.09%) out of 44,814 plant-pollinator pairs showed significant interaction avoidance. Our results suggest that interactions involving specialist species have a high probability to show interaction fidelity and a low probability of interaction avoidance. In addition, we find that particular associations between plant and insect orders, as for example interactions between Hymenoptera and Fabales, showed high fidelity and low avoidance. Although niche and neutral processes simultaneously influence patterns of interaction in ecological communities, our findings suggest that it is rather neutral processes that are shaping the patterns of interactions in plant-pollinator networks.

Edge disturbance shapes liana diversity and abundance but not liana-tree interaction network patterns in moist semi-deciduous forests, Ghana

Edge disturbance can drive liana community changes and alter liana-tree interaction networks, with ramifications for forest functioning. Understanding edge effects on liana community structure and liana-tree interactions is therefore essential for forest management and conservation. We evaluated the response patterns of liana community structure and liana-tree interaction structure to forest edge in two moist semi-deciduous forests in Ghana (Asenanyo and Suhuma Forest Reserves: AFR and SFR, respectively). Liana community structure and liana-tree interactions were assessed in 24 50 × 50 m randomly located plots in three forest sites (edge, interior and deep-interior) established at 0-50 m, 200 m and 400 m from edge. Edge effects positively and negatively influenced liana diversity in forest edges of AFR and SFR, respectively. There was a positive influence of edge disturbance on liana abundance in both forests. We observed anti-nested structure in all the liana-tree networks in AFR, while no nestedness was observed in the networks in SFR. The networks in both forests were less connected, and thus more modular and specialised than their null models. Many liana and tree species were specialised, with specialisation tending to be symmetrical. The plant species played different roles in relation to modularity. Most of the species acted as peripherals (specialists), with only a few species having structural importance to the networks. The latter species group consisted of connectors (generalists) and hubs (highly connected generalists). Some of the species showed consistency in their roles across the sites, while the roles of other species changed. Generally, liana species co-occurred randomly on tree species in all the forest sites, except edge site in AFR where lianas showed positive co-occurrence. Our findings deepen our understanding of the response of liana communities and liana-tree interactions to forest edge disturbance, which are useful for managing forest edge.

Structural resilience and high interaction dissimilarity of plant-pollinator interaction networks in fire-prone grasslands

Fire is a frequent disturbance in most grasslands around the world, being key for the structure and dynamics of the biodiversity in such ecosystems. While grassland species may be resilient, little is known on how plant-pollinator networks reassemble after fire. Here, we investigate the structure and dynamics of plant-pollinator networks and the variation in species roles over a 2-year post-fire chronosequence on grassland communities in Southern Brazil. We found that both network specialization and modularity were similar over the chronosequence of time-since-fire, but in freshly burnt areas, there were more species acting as network hubs. Species roles exhibited high variation, with plant and pollinator species shifting roles along the post-disturbance chronosequence. Interaction dissimilarity was remarkably high in networks irrespective of times-since-fire. Interaction dissimilarity was associated more with rewiring than with species turnover, indicating that grassland plant and pollinator species are highly capable of switching partners. Time-since-fire had little influence on network structure but influenced the identity and diversity of pollinators playing key roles in the networks. These findings suggest that pollination networks in naturally fire-prone ecosystems are highly dynamic and resilient to fire with both plants and pollinators being highly capable of adjusting their interactions and network structure after disturbance.

Modularity and specialization in bat-fly interaction networks are remarkably consistent across patches within urbanized landscapes and spatial scales

Patterns of specialization and the structure of interactions between bats and ectoparasitic flies have been studied mostly on non-urban environments and at local scales. Thus, how anthropogenic disturbances influence species interactions and network structure in this system remain poorly understood. Here, we investigated patterns of interaction between Phyllostomidae bats and ectoparasitic Streblidae flies, and variations in network specialization and structure across Cerrado patches within urbanized landscapes in Brazil and between local and regional scales. We found high similarity in the richness and composition of bat and fly species across communities, associated with low turnover of interactions between networks. The high specialization of bat–streblid interactions resulted in little connected and modular networks, with the emergence of modules containing subsets of species that interact exclusively or primarily with each other. Such similarities in species and interaction composition and network structure across communities and scales suggest that bat–fly interactions within Cerrado patches are little affected by the degree of human modification in the surrounding matrix. This remarkable consistency is likely promoted by specific behaviors, the tolerance of Phyllostomidae bats to surrounding urbanized landscapes as well as by the specificity of the streblid–bat interactions shaped over evolutionary time.

Resolving the Rules of Robustness and Resilience in Biology Across Scales

Why do some biological systems and communities persist while others fail? Robustness, a system's stability, and resilience, the ability to return to a stable state, are key concepts that span multiple disciplines within and outside the biological sciences. Discovering and applying common rules that govern the robustness and resilience of biological systems is a critical step toward creating solutions for species survival in the face of climate change, as well as the for the ever-increasing need for food, health, and energy for human populations. We propose that network theory provides a framework for universal scalable mathematical models to describe robustness and resilience and the relationship between them, and hypothesize that resilience at lower organization levels contribute to robust systems. Insightful models of biological systems can be generated by quantifying the mechanisms of redundancy, diversity, and connectivity of networks, from biochemical processes to ecosystems. These models provide pathways towards understanding how evolvability can both contribute to and result from robustness and resilience under dynamic conditions. We now have an abundance of data from model and non-model systems and the technological and computational advances for studying complex systems. Several conceptual and policy advances will allow the research community to elucidate the rules of robustness and resilience. Conceptually, a common language and data structure that can be applied across levels of biological organization needs to be developed. Policy advances such as cross-disciplinary funding mechanisms, access to affordable computational capacity, and the integration of network theory and computer science within the standard biological science curriculum will provide the needed research environments. This new understanding of biological systems will allow us to derive ever more useful forecasts of biological behaviors and revolutionize the engineering of biological systems that can survive changing environments or disease, navigate the deepest oceans, or sustain life throughout the solar system.