While most flowering plants engage in mutualistic interactions with their pollinators, Arisaema species employ a unique, seemingly antagonistic strategy by imprisoning and causing the pollinators to perish within their spathes. Recent studies have revealed that Arisaema thunbergii primarily relies on a fungus gnat, Leia ishitanii, with some individuals possibly escaping female spathes after oviposition. We investigated interactions between A. urashima and its pollinating fungus gnats, given that A. urashima is closely related to A. thunbergii. Specifically, we tested whether decaying A. urashima serve as brood-sites for some pollinators and whether these pollinators can escape seemingly lethal floral traps. We retrieved A. urashima spathes together with adult insect corpses trapped within the spathes and incubated the spathes to see if conspecific insects emerged. In addition, under laboratory conditions, we observed the escape behaviour of Sciophila yokoyamai, whose next-generation adults most frequently emerge from the decaying spathes. Our findings indicate that S. yokoyamai almost always escapes from the female spathe after oviposition while using the inflorescence as a nursery. In contrast, other pollinators of A. urashima, including Mycetophila spp., remain trapped and perished within the spathes. This study demonstrates that A. urashima spathes can function both as lethal traps and mutualistic nurseries, with outcomes differing among pollinator species. Our results also suggest that the contribution of certain pollinators to Arisaema reproduction is underestimated or even neglected, given that information on their pollinator assemblages has been based on floral visitors trapped within the inflorescences.

Gene loss is expected in microbial communities when the benefit of obtaining a biosynthetic precursor from a neighbor via cross-feeding outweighs the cost of retaining a biosynthetic gene. However, gene cost primarily comes from expression, and many biosynthetic genes are only expressed when needed. Thus, one can conversely expect cross-feeding to repress biosynthetic gene expression and promote gene retention by lowering gene cost. Here we examined long-term bacterial cocultures pairing Escherichia coli and Rhodopseudomonas palustris for evidence of gene loss or retention in response to cross-feeding of non-essential adenine. Although R. palustris continued to externalize adenine in long-term cultures, E. coli did not accumulate mutations in purine synthesis genes, even after 700 generations. E. coli purine synthesis gene expression was low in coculture, suggesting that gene repression removed selective pressure for gene loss. In support of this explanation, R. palustris also had low transcript levels for iron-scavenging siderophore genes in coculture, likely because E. coli facilitated iron acquisition by R. palustris. R. palustris siderophore gene mutations were correspondingly rare in long-term cocultures but were prevalent in monocultures where transcript levels were high. Our data suggests that cross-feeding does not always drive gene loss, but can instead promote gene retention by repressing costly expression.

UNASSIGNED: Pollinating flower-consuming mutualisms are considered exemplary models for studying coevolution due to their rarity. Visual cues are considered to have a major role in facilitating the evolution of floral patterns in these systems. We present a new specialized pollinating flower-consuming mutualism from the plant Wurfbainia villosa, which is a traditional Chinese herbal medicine, by a pollinating weevil, Xenysmoderes sp.
UNASSIGNED: In this study, We utilized monochrome plates for binary-choice tests to determine weevil color preferences, conducted behavioral choice experiments, using trackballs, photographed flowers and weevils, and employed blue sticky boards to attract weevils in the field.
UNASSIGNED: Tests were conducted using colorpreferring weevils in both indoor and outdoor field systems, and validation experiments were performed. Behavioral tests were conducted to investigate the role of the visual cues in the pollinator attraction of W. villosa, which is a selfcompatible insect-pollinated plant that relies primarily on the Xenysmoderes sp. weevil for pollination due to its specialized gynandrium-like structure. Behavioral tests demonstrated that a blue color wavelength of 480 nm and the blue color system, as along with the UV-style pattern of the flowers, particularly the parts with specialized gynandrium-like structures in the labellum, were significantly attractive to both male and female weevils. These results were further confirmed through the field blue sticky board trap method.
UNASSIGNED: These findings indicated that the interaction between W. villosa and Xenysmoderes sp. weevil was a novel symbiotic relationship involving pollinator flower consumption. Additionally, Wurfbainia villosa flowers developed specific visual cues of UV patterns and specialized structures that played a crucial role in attracting pollinators.

Ectomycorrhizal fungi employ different strategies for mycelial growth and host colonization under varying nutrient conditions. However, key genes associated with mycorrhizal interaction should be influenced solely by the inoculation treatment and not by nutrient variations. To utilize subtle nutrient differences and rapidly screen for key genes related to the interaction between Suillus luteus and Pinus massoniana, we performed an inoculation experiment using culture bottles containing high- and low-nutrient media. Interestingly, S. luteus LS88 promoted the growth of P. massoniana seedlings without mature ectomycorrhiza, and the impact of LS88 inoculation on P. massoniana roots was greater than that of nutrient changes. In this study, the resequenced genome of the LS88 strain was utilized for transcriptome analysis of the strain. The analysis indicated that a unique gene encoding glutathione S-transferase (GST) in LS88 is likely involved in colonizing P. massoniana roots. In this study, the GST gene expression was independent of nutrient levels. It was probably induced by P. massoniana and could be used as a marker for S. luteus colonization degree.

Biological interactions, including symbiotic ones, have vital roles in ecological and evolutionary processes. Microbial symbionts in the intestinal tracts, known as the gut microbiome, are especially important because they can fundamentally influence the life history, fitness, and competitiveness of their hosts. Studies on the gut-resident microorganisms of wild animals focus mainly on vertebrates, and studies on species-rich invertebrate taxa, such as ground beetles, are sparse. In fact, even among the species-rich genus Carabus, only the gut microbiome of two Asian species was studied, while results on European species are completely missing. Here, we investigated the gut bacterial microbiome of a widespread European Carabus species, targeting the V3 and V4 regions of the 16S ribosomal RNA genes by next-generation high-throughput sequencing. We identified 1138 different operational taxonomic units assigned to 21 bacterial phyla, 90 families, and 197 genera. Members of the carbohydrate-degrading Prevotellaceae family, previously not detected in ground beetles, were the most abundant in the gut microbiome of the carnivorous C. convexus. Presumably, individuals from the studied wild populations also consume plant materials, especially fruits, and these carbohydrate-degrading bacterial symbionts can facilitate both the consumption and the digestion of these supplementary foods.

With increasing land resource constraints, wetlands, as ecological hotspots, are expected to enhance biogeochemical processes to mitigate nitrogen (N) pollution, particularly nitrate-nitrogen (NO3--N). However, the interactions among bacteria, algae, and macrophytes in wetlands, which are crucial for N removal, remain largely unknown. This study explored how macrophyte coverage influences bacterial-algal interactions, shifting from mutualism to inhibition, thereby affecting N removal. Moderate coverage enhanced NO3--N and total nitrogen (TN) removal (P < 0.05), which was correlated with increased microbial abundance (P < 0.05). This may have resulted from moderate algal photosynthesis, reduced physiological stress, and the expansion of ecological niches for microbes. Insufficient coverage promoted algal growth (chlorophyll-a > 31.8 μg·L-1), leading to increased competition for substrates and elevated pH, which further inhibited bacterial activity. Excessive coverage also inhibited bacterial activity by reducing illumination and oxidation-reduction potential. Consequently, insufficient and excessive coverage decreased N removal efficiencies by 2.7-15.7 % (NO3--N) and 3.7-11.1 % (TN) while increasing methane emission potential by 1.4-6.9 times compared with moderate coverage. These findings offer insights into solving NO3--N contamination using near-natural methods and balancing the ecological and practical considerations for small wetlands.

AbstractMutualisms constitute a diverse class of ecologically important interactions, yet their ecological and evolutionary stability remain topics of debate in coevolutionary theory. Recent theoretical and empirical work has suggested that coevolutionary arms races may be involved in the maintenance of mutualistic interactions, sustaining mutually beneficial outcomes for interacting species while producing exaggerated traits. Here we present an individual-based model that evaluates how asynchronous life histories-that is, partners with different average lifespans-change the dynamics of trait coevolution, the expected fitness outcomes for species involved, and the dynamics of selection differentials across time for each species. Results indicate that a longer-lived mutualist will consistently \"lose\" an otherwise balanced coevolutionary arms race, being outpaced in both the mean trait value and fitness outcome compared with a shorter-lived partner. Furthermore, linear selection differentials on mutualistic traits become increasingly divergent as life histories become increasingly asynchronous, with the longer-lived species experiencing persistent directional selection and the shorter-lived species experiencing weaker, more inconsistent selection. These results suggest that asynchronous life histories can complicate the maintenance of mutualistic interactions via coevolutionary arms races and that detecting coevolution via selection differentials may be difficult when life histories are sufficiently divergent.

BACKGROUND: The symbiosis among plants, rhizobia, and arbuscular mycorrhizal fungi (AMF) is one of the most well-known symbiotic relationships in nature. However, it is still unclear how bilateral/tripartite symbiosis works under resource-limited conditions and the diverse genetic backgrounds of the host.
RESULTS: Using a full factorial design, we manipulated mungbean accessions/subspecies, rhizobia, and AMF to test their effects on each other. Rhizobia functions as a typical facilitator by increasing plant nitrogen content, plant weight, chlorophyll content, and AMF colonization. In contrast, AMF resulted in a tradeoff in plants (reducing biomass for phosphorus acquisition) and behaved as a competitor in reducing rhizobia fitness (nodule weight). Plant genotype did not have a significant effect on AMF fitness, but different mungbean accessions had distinct rhizobia affinities. In contrast to previous studies, the positive relationship between plant and rhizobia fitness was attenuated in the presence of AMF, with wild mungbean being more responsive to the beneficial effect of rhizobia and attenuation by AMF.
CONCLUSIONS: We showed that this complex tripartite relationship does not unconditionally benefit all parties. Moreover, rhizobia species and host genetic background affect the symbiotic relationship significantly. This study provides a new opportunity to re-evaluate the relationships between legume plants and their symbiotic partners.

The heat-shock response plays a key role in the immune defence against viruses across various organisms. Studies on model organisms have shown that inducing this response prior to viral exposure enhances host resistance to infections, while deficient responses make individuals more susceptible. Moreover, viruses rely on components of the heat-shock response for their own stability and viral infections improve thermal tolerance in plants, giving infected individuals an advantage in extreme conditions, which aids the virus in replication and transmission. Here, we examine the interaction between the nematode Caenorhabditis elegans and its natural pathogen the Orsay virus (OrV) under heat stress. We found that OrV infection leads to differential expression of heat-stress-related genes, and infected populations show increased resistance to heat-shock. This resistance correlates with increased expression of argonautes alg-1 and alg-2, which are crucial for survival after heat-shock and for OrV replication. Overall, our study suggests an environmental-dependent mutualistic relationship between the nematode and OrV, potentially expanding the animal\'s ecological niche and providing the virus with extra opportunities for replication and adaptation to extreme conditions.

Cyanobacteria are globally occurring photosynthetic bacteria notable for their contribution to primary production and production of toxins which have detrimental ecosystem impacts. Furthermore, cyanobacteria can form mutualistic symbiotic relationships with a diverse set of eukaryotes, including land plants, aquatic plankton and fungi. Nevertheless, not all cyanobacteria are found in symbiotic associations suggesting symbiotic cyanobacteria have evolved specializations that facilitate host-interactions. Photosynthetic capabilities, nitrogen fixation, and the production of complex biochemicals are key functions provided by host-associated cyanobacterial symbionts. To explore if additional specializations are associated with such lifestyles in cyanobacteria, we have conducted comparative phylogenomics of molecular functions and of biosynthetic gene clusters (BGCs) in 984 cyanobacterial genomes. Cyanobacteria with host-associated and symbiotic lifestyles were concentrated in the family Nostocaceae, where eight monophyletic clades correspond to specific host taxa. In agreement with previous studies, symbionts are likely to provide fixed nitrogen to their eukaryotic partners, through multiple different nitrogen fixation pathways. Additionally, our analyses identified chitin metabolising pathways in cyanobacteria associated with specific host groups, while obligate symbionts had fewer BGCs. The conservation of molecular functions and BGCs between closely related symbiotic and free-living cyanobacteria suggests the potential for additional cyanobacteria to form symbiotic relationships than is currently known.