Evolutionary déjà vu? A case of convergent evolution in an ant-plant association.

Obligatory ant-plant symbioses often appear to be single evolutionary shifts within particular ant lineages; however, convergence can be revealed once natural history observations are complemented with molecular phylogenetics. Here, we describe a remarkable example of convergent evolution in an ant-plant symbiotic system. Exclusively arboreal, Myrmelachista species can be generalized opportunists nesting in several plant species or obligately symbiotic, live-stem nesters of a narrow set of plant species. Instances of specialization within Myrmelachista are known from northern South America and throughout Middle America. In Middle America, a diverse radiation of specialists occupies understory treelets of lowland rainforests. The morphological and behavioural uniformity of specialists suggests that they form a monophyletic assemblage, diversifying after a single origin of specialization. Using ultraconserved element phylogenomics and ancestral state reconstructions, we show that shifts from opportunistic to obligately symbiotic evolved independently in South and Middle America. Furthermore, our analyses support a remarkable case of convergence within the Middle American radiation, with two independently evolved specialist clades, arising nearly simultaneously from putative opportunistic ancestors during the late Pliocene. This repeated evolution of a complex phenotype suggests similar mechanisms behind trait shifts from opportunists to specialists, generating further questions about the selective forces driving specialization.

Multispecies coinfections and presence of antibiotics shape resistance and fitness costs in a pathogenic bacterium.

Increasing antimicrobial resistance (AMR) poses a challenge for treatment of bacterial diseases. In real life, bacterial infections are typically embedded within complex multispecies communities and influenced by the environment, which can shape costs and benefits of AMR. However, knowledge of such interactions and their implications for AMR in vivo is limited. To address this knowledge gap, we investigated fitness-related traits of a pathogenic bacterium (Flavobacterium columnare) in its fish host, capturing the effects of bacterial antibiotic resistance, coinfections between bacterial strains and metazoan parasites (fluke Diplostomum pseudospathaceum) and antibiotic exposure. We quantified real-time replication and virulence of sensitive and resistant bacteria and demonstrate that both bacteria can benefit from coinfection in terms of persistence and replication, depending on the coinfecting partner and antibiotic presence. We also show that antibiotics can benefit resistant bacteria by increasing bacterial replication under coinfection with flukes. These results emphasize the importance of diverse, inter-kingdom coinfection interactions and antibiotic exposure in shaping costs and benefits of AMR, supporting their role as significant contributors to spread and long-term persistence of resistance.

The overlooked complexity of avian brood parasite-host relationships.

The relationships between avian brood parasites and their hosts are widely recognised as model systems for studying coevolution. However, while most brood parasites are known to parasitise multiple species of host and hosts are often subject to parasitism by multiple brood parasite species, the examination of multispecies interactions remains rare. Here, we compile data on all known brood parasite-host relationships and find that complex brood parasite-host systems, where multiple species of brood parasites and hosts coexist and interact, are globally commonplace. By examining patterns of past research, we outline the disparity between patterns of network complexity and past research emphases and discuss factors that may be associated with these patterns. Drawing on insights gained from other systems that have embraced a multispecies framework, we highlight the potential benefits of considering brood parasite-host interactions as ecological networks and brood parasitism as a model system for studying multispecies interactions. Overall, our results provide new insights into the diversity of these relationships, highlight the stark mismatch between past research efforts and global patterns of network complexity, and draw attention to the opportunities that more complex arrangements offer for examining how species interactions shape global patterns of biodiversity.

Multiple Mutualism Effects generate synergistic selection and strengthen fitness alignment in the interaction between legumes, rhizobia and mycorrhizal fungi.

Nearly all organisms participate in multiple mutualisms, and complementarity within these complex interactions can result in synergistic fitness effects. However, it remains largely untested how multiple mutualisms impact eco-evolutionary dynamics in interacting species. We tested how multiple microbial mutualists-N-fixing bacteria and mycorrrhizal fungi-affected selection and heritability of traits in their shared host plant (Medicago truncatula), as well as fitness alignment between partners. Our results demonstrate for the first time that multiple mutualisms synergistically affect the selection and heritability of host traits and enhance fitness alignment between mutualists. Specifically, we found interaction with multiple microbial symbionts doubled the strength of natural selection on a plant architectural trait, resulted in 2- to 3-fold higher heritability of plant reproductive success, and more than doubled fitness alignment between N-fixing bacteria and plants. These findings show synergism generated by multiple mutualisms extends to key components of microevolutionary change, emphasising the importance of multiple mutualism effects on evolutionary trajectories.

Effect of algal surface area and species interactions in toxicity testing bioassays.

Single and multispecies algal bioassays were assessed using copper toxicity with three green algae (Scenedesmus subspicatus, Scenedesmus quadricauda and Ankistrodesmus angustus) and one blue-green algae species (Oscillatoria prolifera). Single and multispecies toxicity tests were conducted based on cell density as per standard toxicity testing, and on equivalent surface area. A higher copper sulfate toxicity was registered for O. prolifera, followed by S. subspicatus, S. quadricauda, and A. angustus in single-species toxicity tests based on cell density. Single species toxicity tests based on surface area showed increased copper toxicity with increasing algal surface area except for A. angustus. In multispecies control bioassays, the growth of A. angustus was inhibited in the presence of other species in surface area-based tests. As compared to single species bioassays, O. prolifera, and S. quadricauda showed a decreased sensitivity to copper sulfate in both cell density and surface area based multispecies tests. However, for the algae species with the smallest surface area, S. subspicatus, 96h-EC50 value decreased in multispecies bioassays based on surface area as compared to the single species test, while it increased in multispecies bioassays based on cell density. The difference in S. subspicatus sensitivity to copper between tests based on cell density and surface area supports the need to adopt multispecies toxicity testing based on surface area to avoid the confounding effect on copper toxicity of increased biomass for metal binding. 96h-EC50 values for all species combined in the multispecies test based on cell density and on surface area were significantly different from 96h-EC50 values obtained in single species bioassays. These results demonstrate that single-species bioassays may over- or underestimate metal toxicity in natural waters.

The acacia ants revisited: convergent evolution and biogeographic context in an iconic ant/plant mutualism.

Phylogenetic and biogeographic analyses can enhance our understanding of multispecies interactions by placing the origin and evolution of such interactions in a temporal and geographical context. We use a phylogenomic approach-ultraconserved element sequence capture-to investigate the evolutionary history of an iconic multispecies mutualism: Neotropical acacia ants (Pseudomyrmex ferrugineus group) and their associated Vachellia hostplants. In this system, the ants receive shelter and food from the host plant, and they aggressively defend the plant against herbivores and competing plants. We confirm the existence of two separate lineages of obligate acacia ants that convergently occupied Vachellia and evolved plant-protecting behaviour, from timid ancestors inhabiting dead twigs in rainforest. The more diverse of the two clades is inferred to have arisen in the Late Miocene in northern Mesoamerica, and subsequently expanded its range throughout much of Central America. The other lineage is estimated to have originated in southern Mesoamerica about 3 Myr later, apparently piggy-backing on the pre-existing mutualism. Initiation of the Pseudomyrmex/Vachellia interaction involved a shift in the ants from closed to open habitats, into an environment with more intense plant herbivory. Comparative studies of the two lineages of mutualists should provide insight into the essential features binding this mutualism.

Indirect effects of herbivory on plant-pollinator interactions in invasive Lythrum salicaria.

PREMISE OF THE STUDY: Herbivory can affect a plant's fitness in a variety of ways, including modifying the biotic interactions of the plant. In particular, when herbivory influences floral display, we hypothesize that pollinator visitation will be altered accordingly. Here we studied the indirect effects of feeding by two beetles, Neogalerucella calmariensis and N. pusilla, released as a biological control, on plant-pollinator interactions and fitness in the invasive plant, purple loosestrife (Lythrum salicaria). METHODS: Two herbivory treatments (ambient and simulated) were applied to plants in a naturally occurring population of purple loosestrife. During flowering, traits of plants in the treatment and control groups were recorded. Data on pollinator visitation behavior was then collected after intense larval herbivory had ended. KEY RESULTS: Plants exposed to herbivory treatments produced more flowers and inflorescences but flowered significantly later than those in the control group. Moreover, we found a significant, positive association of herbivory with the number of flowers probed by bumblebees and with the number of times a foraging pollinator moved among inflorescences on a single plant. No differences in female fitness (fruit or seed production) were detected. CONCLUSIONS: We conclude that herbivore-mediated differences in floral display traits impacted pollinator visitation behavior. However, as we discuss, differences in pollinator visitation did not translate into detectable differences in female reproductive success. We postulate that herbivory could influence other unmeasured aspects of fitness, such as seed quality or the number of seeds sired.

A tale of two rivers: development, destruction, and despair in Ongata Rongai, Kenya.

Introduction: Ongata Rongai is a rapidly growing peri-urban space in Nairobi Metropolitan, Kenya. The last 10 years have seen exponential population growth and building development leading to overcrowding and pressure on water and environmental resources. This original research sheds light on interactions among humans, animals, and this rapidly changing urban environment. It is therefore a quintessentially One Health study. Methods: Qualitative and ethnographically informed methods are employed to better understand the impact of rapid growth on the riparian environment and the effect of this on those who depend on it. The reflexive use of archival material and a historical ethnographic approach enabled in-depth narratives to address these issues within a longitudinal context, and the use of deliberate walking alongside visual methodologies and more traditional anthropological methods make this study novel both in terms of methodological approach and findings. Results: This study finds that people cite high levels of pollution from solid waste and sewage have made the rivers almost unusable and a hazardous place for both humans and animals. Yet, in the past, these rivers played key roles in daily life. There is frustration with structural-level actors' moribund attitude to the environment. The poor health of the rivers and riparian environment leads to human and animal health challenges, increased pressure on water resources, and economic pressure due to a loss of livelihoods. Discussion: The study contributes to what is currently a fairly small literature on urban riparian spaces globally, but one which is of growing and vital importance given the rapidly increasing percentage of humans who now reside in urban spaces. It contributes to WASH and urban clean water knowledge as well as One Health, public health, and urban growth narratives, and directly addresses challenges faced by SDG 6.

Pollinators and herbivores interactively shape selection on strawberry defence and attraction.

Tripartite interactions between plants, herbivores, and pollinators hold fitness consequences for most angiosperms. However, little is known on how plants evolve in response-and in particular what the net selective outcomes are for traits of shared relevance to pollinators and herbivores. In this study, we manipulated herbivory ("presence" and "absence" treatments) and pollination ("open" and "hand pollination" treatments) in a full factorial common-garden experiment with woodland strawberry (Fragaria vesca L.). This design allowed us to quantify the relative importance and interactive effects of herbivore- and pollinator-mediated selection on nine traits related to plant defence and attraction. Our results showed that pollinators imposed stronger selection than herbivores on traits related to both direct and indirect (i.e., tritrophic) defence. However, conflicting selection was imposed on inflorescence density: a trait that appears to be shared by herbivores and pollinators as a host plant signal. However, in all cases, selection imposed by one agent depended largely on the presence or ecological effect of the other, suggesting that dynamic patterns of selection could be a common outcome of these interactions in natural populations. As a whole, our findings highlight the significance of plant-herbivore-pollinator interactions as potential drivers of evolutionary change, and reveal that pollinators likely play an underappreciated role as selective agents on direct and in direct plant defence.

Insight into the benefits of anammox bacteria living as aggregates.

This work tried understanding aggregation preference of anammox bacteria from benefit-driven perspective. Aggregated anammox sludge (AGS) gained benefits in specific anammox activity (SAA) (increased by 40.47 ± 12.64%) and in toxicity resistance (enhanced by 65.41%) than scattered anammox sludge (SCS), which were verified by kinetics. The increased heme c content by 35.67 ± 5.77% and enhanced relative abundance of anammox bacteria by 9.29% supported the benefits in biological activity and improved EPS content by 1097.59 ± 43.06% (622.16 ± 61.73% for protein (PN), 2403.47 ± 162.75% for humic acid (HA) and 1145.34 ± 97.33% for polysaccharide (PS)) justified the benefits in toxicity resistance. The diverse microbial communities and organized spatial structures owned by AGS promoted interactions between species, as the intrinsic justification for obtaining the benefits. We expect our findings to provide theoretical guidance for promotions and applications of the anammox process with excellent nitrogen removal capacity and stability.

BLANKA: an Algorithm for Blank Subtraction in Mass Spectrometry of Complex Biological Samples.

Multispecies microbiome systems are known to be closely linked to human, animal, and plant life processes. The growing field of metabolomics presents the opportunity to detect changes in overall metabolomic profiles of microbial species interactions. These metabolomic changes provide insight into function of metabolites as they correlate to different species presence and the observed phenotypic changes, but detection of subtle changes is often difficult in samples with complex backgrounds. Natural environments such as soil and food contain many molecules that convolute mass spectrometry-based analyses, and identification of microbial metabolites amongst environmental metabolites is an informatics problem we begin to address here. Our microbes are grown on solid or liquid cheese curd media. This medium, which is necessary for microbial growth, contains high amounts of salts, lipids, and casein breakdown products which make statistical analyses using LC-MS/MS data difficult due to the high background from the media. We have developed a simple algorithm to carry out background subtraction from microbes grown on solid or liquid cheese curd media to aid in our ability to conduct statistical analyses so that we may prioritize metabolites for further structure elucidation. Graphical Abstract .

Mycorrhizal interactions do not influence plant-herbivore interactions in populations of Clarkia xantiana ssp. xantiana spanning from center to margin of the geographic range.

Multispecies interactions can be important to the expression of phenotypes and in determining patterns of individual fitness in nature. Many plants engage in symbiosis with arbuscular mycorrhizal fungi (AMF), but the extent to which AMF modulate other species interactions remains poorly understood. We examined multispecies interactions among plants, AMF, and insect herbivores under drought stress using a greenhouse experiment and herbivore choice assays. The experiment included six populations of Clarkia xantiana (Onagraceae), which span a complex environmental gradient in the Southern Sierra Nevada of California. Clarkia xantiana's developing fruits are commonly attacked by grasshoppers at the end of the growing season, and the frequency of attack is more common in populations from the range center than range margin. We found that AMF negatively influenced all metrics of plant growth and reproduction across all populations, presumably because plants supplied carbon to AMF but did not benefit substantially from resources potentially supplied by the AMF. The fruits of plants infected with AMF did not differ from those without AMF in their resistance to grasshoppers. There was significant variation among populations in damage from herbivores but did not reflect the center-to-margin pattern of herbivory observed in the field. In sum, our results do not support the view that AMF interactions modulate plant-herbivore interactions in this system.

Phenotypic responses to microbial volatiles render a mold fungus more susceptible to insect damage.

In decomposer systems, fungi show diverse phenotypic responses to volatile organic compounds of microbial origin (volatiles). The mechanisms underlying such responses and their consequences for the performance and ecological success of fungi in a multitrophic community context have rarely been tested explicitly. We used a laboratory-based approach in which we investigated a tripartite yeast-mold-insect model decomposer system to understand the possible influence of yeast-borne volatiles on the ability of a chemically defended mold fungus to resist insect damage. The volatile-exposed mold phenotype (1) did not exhibit protein kinase A-dependent morphological differentiation, (2) was more susceptible to insect foraging activity, and (3) had reduced insecticidal properties. Additionally, the volatile-exposed phenotype was strongly impaired in secondary metabolite formation and unable to activate "chemical defense" genes upon insect damage. These results suggest that volatiles can be ecologically important factors that affect the chemical-based combative abilities of fungi against insect antagonists and, consequently, the structure and dynamics of decomposer communities.

The role of multispecies social interactions in shaping Pseudomonas aeruginosa pathogenicity in the cystic fibrosis lung.

Pseudomonas aeruginosa is a major pathogen in the lungs of cystic fibrosis (CF) patients. However, it is now recognised that a diverse microbial community exists in the airways comprising aerobic and anaerobic bacteria as well as fungi and viruses. This rich soup of microorganisms provides ample opportunity for interspecies interactions, particularly when considering secreted compounds. Here, we discuss how P. aeruginosa-secreted products can have community-wide effects, with the potential to ultimately shape microbial community dynamics within the lung. We focus on three well-studied traits associated with worsening clinical outcome in CF: phenazines, siderophores and biofilm formation, and discuss how secretions can shape interactions between P. aeruginosa and other commonly encountered members of the lung microbiome: Staphylococcus aureus, the Burkholderia cepacia complex, Candida albicans and Aspergillus fumigatus. These interactions may shape the evolutionary trajectory of P. aeruginosa while providing new opportunities for therapeutic exploitation of the CF lung microbiome.

Threesomes destabilise certain relationships: multispecies interactions between wood decay fungi in natural resources.

Understanding interspecific interactions is key to explaining and modelling community development and associated ecosystem function. Most interactions research has focused on pairwise combinations, overlooking the complexity of multispecies communities. This study investigated three-way interactions between saprotrophic fungi in wood and across soil, and indicated that pairwise combinations are often inaccurate predictors of the outcomes of multispecies competition in wood block interactions. This inconsistency was especially true of intransitive combinations, resulting in increased species coexistence within the resource. Furthermore, the addition of a third competitor frequently destabilised the otherwise consistent outcomes of pairwise combinations in wood blocks, which occasionally resulted in altered resource decomposition rates, depending on the relative decay abilities of the species involved. Conversely, interaction outcomes in soil microcosms were unaffected by the presence of a third combatant. Multispecies interactions promoted species diversity within natural resources, and made community dynamics less consistent than could be predicted from pairwise interaction studies.