Host Species Research Articles

Редкая находка: скребень Neoechinorhynchus beringianus (Eoacanthocephala: Neoechinorhynchidae) в бассейне верхней Колымы

The parasite of nine-spine sticklebacks, the Neoechinorhynchus beringianus, was found in the intestines of the broad whitefish caughtin the BuyundaRiver, the Kolyma tributary. Themorphometric parameters of the found specimen and individuals of the same species from the population existing in the lower reaches of the Kolyma River were compared. The possible conditions of the host species infection with a non-indigenous parasite and the variants of the acanthocephalan settlement in the river basin are considered.

Редкая находка: скребень Neoechinorhynchus beringianus (Eoacanthocephala: Neoechinorhynchidae) в бассейне верхней Колымы

The parasite of nine-spine sticklebacks, the Neoechinorhynchus beringianus, was found in the intestines of the broad whitefish caughtin the BuyundaRiver, the Kolyma tributary. Themorphometric parameters of the found specimen and individuals of the same species from the population existing in the lower reaches of the Kolyma River were compared. The possible conditions of the host species infection with a non-indigenous parasite and the variants of the acanthocephalan settlement in the river basin are considered.

Incipient decay in beech (Fagus sylvatica L.) and linden (Tilia cordata Mill.): An interspecific static and dynamic material analysis

With increasing awareness of the ecological value of trees in urban areas, there is a growing need to preserve mature specimens often colonised by wood-decay fungi. Nonetheless, cases of stem collapse or uprooting of such trees under adverse weather conditions remain a significant issue requiring further investigation. Depending on the decay type and the wood structure of the host tree, different combinations of wood-decaying fungi and host species can have varying impacts on the mechanical and vibroacoustic properties of green wood. This study compares the physical and mechanical properties of green European beech (Fagus sylvatica L.) and small-leaved linden (Tilia cordata Mill.) artificially exposed to Fomes fomentarius (L.) Fr. and Kretzschmaria deusta (Hoff.) P.M.D. Martin after different exposure periods. Mass loss (ML) caused by both fungi differed according to the wood species. A statistically significant difference between the two fungal species was observed in beech wood, but not in linden. Significant differences in the modulus of rupture (MOR) and dynamic bending modulus of elasticity (MOED) were observed among the fungus-wood combinations, also depending on the exposure time. The relationships between ML and MOR varied according to the fungal species, where at the same ML values, K. deusta caused a higher MOR loss in both wood species. Strong relationships between MOED and MOR were demonstrated for all fungus-wood combinations, without significant differences related to the decay type. The MOED is a reliable parameter for predicting MOR loss even at incipient degradation stages, irrespective of the type of decay. The presented results can lead to better prediction of the impact of fungal colonization on standing trees and improve non-destructive methods used for tree stability assessment.

Priority effects alter microbiome composition and increase abundance of probiotic taxa in treefrog tadpoles.

Harnessing the functions of host-associated bacteria is a promising mechanism for managing disease outcomes across different host species. In the case of amphibians, certain frog-associated bacteria can mitigate lethal outcomes of infection by the fungal pathogen Batrachochytrium dendrobatidis. Successful probiotic applications require knowledge of community assembly and an understanding of the ecological mechanisms that structure these symbiotic bacterial communities. In our study, we show the importance of environment and parentage in determining bacterial community composition and that community composition can be influenced by priority effects. Further, we provide support for the use of bacterial priority effects as a mechanism to increase the relative abundance of target probiotic taxa in a developing host. While our results show that priority effects are not universally effective across all host-associated bacteria, our ability to increase the relative abundance of specific probiotic taxa may enhance conservation strategies that rely on captive rearing of endangered vertebrates.

Lack of abundant core virome in Culex mosquitoes from a temperate climate region despite a mosquito species-specific virome.

In arthropod-associated microbial communities, insect-specific viruses (ISVs) are prevalent yet understudied due to limited infectivity outside their natural hosts. However, ISVs might play a crucial role in regulating mosquito populations and influencing arthropod-borne virus transmission. Some studies have indicated a core virome in mosquitoes consisting of mostly ISVs. Employing single mosquito metagenomics, we comprehensively profiled the virome of native and invasive mosquito species in Belgium. This approach allowed for accurate host species determination, prevalence assessment of viruses and Wolbachia, and the identification of novel viruses. Contrary to our expectations, no abundant core virome was observed in Culex mosquitoes from Belgium. In that regard, we caution against rigidly defining mosquito core viromes and encourage nuanced interpretations of other studies. Nonetheless, our study identified 45 viruses of which 28 were novel, enriching our understanding of the mosquito virome and ISVs. We showed that the mosquito virome in this study is species-specific and less dependent on the location where mosquitoes from the same species reside. In addition, because Wolbachia has previously been observed to influence arbovirus transmission, we report the prevalence of Wolbachia in Belgian mosquitoes and the detection of several Wolbachia mobile genetic elements. The observed prevalence ranged from 83% to 92% in members from the Culex pipiens complex.IMPORTANCECulex pipiens mosquitoes are important vectors for arboviruses like West Nile virus and Usutu virus. Virome studies on individual Culex pipiens, and on individual mosquitoes in general, have been lacking. To mitigate this, we sequenced the virome of 190 individual Culex and 8 individual Aedes japonicus mosquitoes. We report the lack of a core virome in these mosquitoes from Belgium and caution the interpretation of other studies in this light. The discovery of new viruses in this study will aid our comprehension of insect-specific viruses and the mosquito virome in general in relation to mosquito physiology and mosquito population dynamics.

Zinc-finger (ZiF) fold secreted effectors form a functionally diverse family across lineages of the blast fungus Magnaporthe oryzae.

Filamentous plant pathogens deliver effector proteins into host cells to suppress host defence responses and manipulate metabolic processes to support colonization. Understanding the evolution and molecular function of these effectors provides knowledge about pathogenesis and can suggest novel strategies to reduce damage caused by pathogens. However, effector proteins are highly variable, share weak sequence similarity and, although they can be grouped according to their structure, only a few structurally conserved effector families have been functionally characterized to date. Here, we demonstrate that Zinc-finger fold (ZiF) secreted proteins form a functionally diverse effector family in the blast fungus Magnaporthe oryzae. This family relies on the Zinc-finger motif for protein stability and is ubiquitously present in blast fungus lineages infecting 13 different host species, forming different effector tribes. Homologs of the canonical ZiF effector, AVR-Pii, from rice infecting isolates are present in multiple M. oryzae lineages. Wheat infecting strains of the fungus also possess an AVR-Pii like allele that binds host Exo70 proteins and activates the immune receptor Pii. Furthermore, ZiF tribes may vary in the proteins they bind to, indicating functional diversification and an intricate effector/host interactome. Altogether, we uncovered a new effector family with a common protein fold that has functionally diversified in lineages of M. oryzae. This work expands our understanding of the diversity of M. oryzae effectors, the molecular basis of plant pathogenesis and may ultimately facilitate the development of new sources for pathogen resistance.

The prevalence and infection rates of amphistome species in intermediate snail hosts: a systematic review and meta-analysis

The systematic review and meta-analysis were conducted to determine the estimates of the prevalence and infection rates of natural and experimental infections of amphistome species in intermediate host snails (IHs) across different continents. A search of peer-reviewed literature on natural and experimental infections of freshwater snails with amphistome species was conducted from four electronic databases from 1984 to 2023. The estimates of the prevalence and/or infection rates were based on 36 eligible peer-reviewed articles, which met the inclusion criteria and reported on natural and experimental infections of amphistome species in freshwater snails. The results showed that a total of 1,67,081 snail species from the peer-reviewed articles were examined for natural infections and 7,659 snail species for experimental infections. The overall pooled prevalence of amphistome infections from naturally infected snails was 2% (95% CI: 0–4), while the overall pooled prevalence of amphistome infections from infections was 40% (95% CI: 18–64). The highest pooled prevalence of natural infection was 3%, which was recorded in Europe (95% CI: 1–7%). The highest overall prevalence of naturally infected amphistome was 6% (95% CI: 0–20%) for Paramphistomum epiclitum. The Americas had the highest pooled prevalence of experimental amphistome infection among freshwater snails (66%; 95% CI: 26–96%). The highest pooled infection rate of 65% (95% CI: 12–100%) was recorded for Paramphistomum cervi in experimental infections. Galba truncatula was the only snail that qualified for meta-analysis for natural infection with Calicophoron daubneyi, with a pooled prevalence of 3% (95% CI: 1–8%). Galba truncatula infected with C. daubneyi and P. cervi, and Bulinus tropicus infected with Calicophoron microbothrium in the experimental infection qualified for the meta-analysis, with an overall infection rate of 66% (95% CI: 34–92%) and 30% (95% CI: 0–74%), respectively. The pooled prevalence of amphistome species infection in the intermediate host (IH) snails based on detection techniques was higher with PCR compared to the dissection and shedding of cercariae. The results from the quality effects model revealed a high heterogeneity and publication bias between studies. This meta-analysis provided valuable insights into the prevalence and infection rates of amphistome species in snail IHs across different geographical regions.

Epidemiology and Transmission of Foot and Mouth Disease among Small Ruminants – A Review

Foot-and-mouth disease (FMD) is a highly contagious viral infection that affects cloven-hoofed animals, including small ruminants such as sheep and goats. FMD causes severe economic losses due to reduced productivity, trade restrictions, and control measures. The epidemiology and transmission of FMD among small ruminants are influenced by various factors, such as the virus strain, the host species, the environmental conditions, and the animal management practices. This paper reviews the current knowledge on the epidemiology and transmission of foot-and-mouth disease (FMD) among small ruminants. It also examines the global distribution and prevalence of FMD in small ruminants, the clinical signs and lesions of FMD in small ruminants, the role of small ruminants in the maintenance and spread of FMD, the transmission routes and risk factors of FMD in small ruminants, and the implications of FMD in small ruminants for disease control and eradication. The paper also identifies the knowledge gaps and research priorities for improving the understanding and management of FMD in small ruminants.

"Isolation by Gentes with Asymmetric Migration" shapes the genetic structure of the common cuckoo in China.

Amid coevolutionary arms races between brood parasitic birds and their diverse host species, the formation of host-specific races, or gentes, has drawn significant research focus. Nevertheless, numerous questions about gentes evolutionary patterns persist. Here, we investigated the potential for gentes evolution across multiple common cuckoo (Cuculus canorus) populations parasitizing diverse host species in China. Using maternal (mitochondrial and W-linked DNA) and biparental (autosomal and Z-linked DNA) markers, we found consistent clustering of cuckoo gentes (rather than geographical populations) into distinct clades in matrilineal gene trees, indicating robust differentiation. In contrast, biparental markers indicated intermixing of all gentes, suggesting asymmetric gene flow regardless of geography. Unlike the mitonuclear discordance commonly resulting from incomplete lineage sorting, adaptive introgression, or demographic disparities, the observed pattern in brood parasitic cuckoos might reflect biased host preferences between sexes. We hereby present the "Isolation by Gentes with Asymmetric Migration" model. According to this model, the maternal line differentiation of the common cuckoo in China is potentially driven by host preferences in females, whereas males maintained the integrity of the cuckoo species through random mating. To achieve this, cuckoo males could perform flexible migration among gentes or engage in early copulation with females before reaching the breeding sites, allowing female cuckoos to store sperm from various gentes. Future studies collecting additional samples from diverse cuckoo gentes with overlapping distribution and investigating the migratory and copulation patterns of each sex would enhance our understanding of sex-biased differentiation among cuckoo populations in China.

Host specificity and virulence of Flavobacterium psychrophilum: a comparative study in ayu (Plecoglossus altivelis) and rainbow trout (Oncorhynchus mykiss) hosts

Flavobacterium psychrophilum, the causative agent of bacterial cold-water disease, is a devastating, worldwide distributed, fish pathogen causing significant economic loss in inland fish farms. Previous epidemiological studies showed that prevalent clonal complexes (CC) differ in fish species affected with disease such as rainbow trout, coho salmon and ayu, indicating significant associations between particular F. psychrophilum genotypes and host species. Yet, whether the population structure is driven by the trade of fish and eggs or by host-specific pathogenicity is uncertain. Notably, all F. psychrophilum isolates retrieved from ayu belong to Type-3 O antigen (O-Ag) whereas only very few strains retrieved from other fish species possess this O-Ag, suggesting a role in outbreaks affecting ayu. Thus, we investigated the links between genotype and pathogenicity by conducting comparative bath infection challenges in two fish hosts, ayu and rainbow trout, for a collection of isolates representing different MLST genotypes and O-Ag. Highly virulent strains in one host species exhibited low to no virulence in the other. F. psychrophilum strains associated with ayu and possessing Type-3 O-Ag demonstrated significant variability in pathogenicity in ayu, ranging from avirulent to highly virulent. Strikingly, F. psychrophilum strains retrieved from rainbow trout and possessing the Type-3 O-Ag were virulent for rainbow trout but not for ayu, indicating that Type-3 O-Ag alone is not sufficient for pathogenicity in ayu, nor does it prevent pathogenicity in rainbow trout. This study revealed that the association between a particular CC and host species partly depends on the pathogen’s adaptation to specific host species.

Crystallization experiments of the wheel-and-axle host compound, 1,4-phenylene-bis(di-p-tolylmethanol), from pyridine and methylpyridine mixtures

Abstract1,4-Phenylene-bis(di-p-tolylmethanol) (H), a host compound with the wheel-and-axle design, formed complexes with organic guest solvents pyridine (PYR) and 2-, 3- and 4-methylpyridine (2MP, 3MP and 4MP). The host: guest (H: G) ratios were 1:3, 1:2, 1:2 and 1:1, respectively. Host crystallization experiments from mixed guests demonstrated H to prefer both PYR and 4MP; however, it was established that these difficult-to-separate (by fractional distillations) guest mixtures cannot be purified/separated by means of H through supramolecular chemistry strategies owing to these selectivities for PYR and 4MP being less than optimal. Single crystal X-ray diffraction experiments showed that each guest compound was held in its complex by means of a classical hydrogen bond with H, and that one of the preferred guests, PYR, experienced a significantly shorter contact of this type than the other guests. Hirshfeld surface analyses demonstrated that PYR was also involved in a greater percentage of (guest)N···H(host) interactions compared with the other guest molecules. Thermal analyses, on the other hand, revealed that 4MP (also a favoured guest species) formed the most stable complex of the four in this investigation. These results with H were compared to those obtained when employing a closely related host compound from a previous report, 1,4-bis(diphenylhydroxymethyl)benzene: while both host species preferred the same guests (PYR and 4MP), the extent of the selectivity of that host compound compared with H in the present work was significantly more enhanced. Thus, minor modifications may deleteriously affect the selectivity behaviour of closely related host compounds.

Trypanosoma cruzi in Wild and Synanthropic Mammals in Two Regions of Mexico: A Fieldwork and Genetic Discrete Typing Unit Review.

Background: Marsupials and rodents are the most important wild and synanthropic hosts of Trypanosoma cruzi due to the high frequency of infection, maintenance of diverse genetic populations of the parasite, and their close proximity to interact with both transmission cycles, sylvatic and peridomestic. Our aim was to identify the discrete typing units (DTU) of T. cruzi from different wild and synanthropic hosts in two regions of Mexico and to carry out a review of historical data focusing on current knowledge on the diversity and T. cruzi DTUs of host species. Materials and Methods: One hundred fifteen samples were obtained from two areas in Tabasco and Nayarit state. The presence of T. cruzi was evaluated by PCR. Results: The 12.6% (12/95) of samples from Tabasco and 65% (13/20) from Nayarit were found to be positive for parasite DNA. All the sequences analyzed were grouped in T. cruzi DTU I; low nucleotide diversity was observed in Tabasco (π = 0.00566, and ϴ = 0.00632), while high genetic diversity was observed in Nayarit sequences, up to 8.63 (π) to 11.10 (ϴ) times greater than Tabasco sequences. Genetic flow and migration between Tabasco, and Nayarit were scarce (FST = 0.37329 and Nm = 0.42), and genetic exchange was observed only between nearby areas. The bibliographic review of hosts in Mexico, together with our data, shows a heterogeneous T. cruzi prevalence in Chiroptera and domestic animals. For Atelidae and Canids, prevalence is generally below 25%. However, a high prevalence, greater than 25% and up to 100%, was recorded in Didelphimorphia, and Rodentia. Few studies in regions of Mexico have been described as infected with the parasite; in these, the genetic group with the highest prevalence is the DTU I. Conclusion: Marsupials and rodents are important reservoirs of T. cruzi; DTU I was frequently reported; however, recent genetic and reservoir studies have demonstrated the presence of greater diversity of genetic groups.

Host lifestyle and parasite interspecific facilitation mediate co‐infection in a species‐poor host–parasite system

Despite their important ecological role, questions remain on mechanisms structuring parasite assemblages. We present an endemic and species‐poor parasite–host system of two species of clupeid fishes Limnothrissa miodon, Stolothrissa tanganicae) and two species of monogenean parasites (Kapentagyrus, Dactylogyridae) from Lake Tanganyika as a model to study parasite distribution patterns and co‐infection dynamics in nature. We modelled spatiotemporal dynamics of parasite–host interaction using infection data along the north–south axis of Lake Tanganyika (660 km) over the course of two seasons and four years (1730 fish, 3710 parasites). We found temporal stability of parasite infection, which contrasts with previously reported seasonally driven fluctuations of fish host abundances. We found a difference in spatial structure between the parasite species which follows the contrasting dispersal pattern of their respective host species. On L. miodon, the host species that is infected by the two parasite species, we discovered a positive correlation with host body size for one parasite species, and a negative correlation for the other species. The apparent host‐size related replacement in the two parasite species infecting L. miodon contrasts with the beneficial influence that each of the parasite species has on the other. Parasites have been reported in previous studies to change habitat depending on host size/age. Differences in abundance and prevalence here reported between parasite species infecting the same host species related to the host body length further illustrate the parasites' dependence on changes in lifestyle of the host during its ontogenetic development. Also, possible mechanisms underlying the reported facilitation of infection are discussed. In conclusion, we show that in this closed, species‐poor system parasite infection dynamics are dependent on a combination of host mobility, host lifestyle changes over ontogenetic development, and interspecific interactions between parasites.

Seasonal dietary changes relate to gut microbiota composition depending on the host species but do not correlate with gut microbiota diversity in arthropod-eating lizards.

The animal gut microbiota is strongly influenced by environmental factors that shape their temporal dynamics. Although diet is recognized as a major driver of gut microbiota variation, dietary patterns have seldom been linked to gut microbiota dynamics in wild animals. Here, we analysed the gut microbiota variation between dry and rainy seasons across four Sceloporus species (S. aeneus, S. bicanthalis, S. grammicus and S. spinosus) from central Mexico in light of temporal changes in diet composition. The lizard microbiota was dominated by Firmicutes (now Bacillota) and Bacteroidota, and the closely related species S. aeneus and S. bicanthalis shared a great number of core bacterial taxa. We report species-specific seasonal changes in gut microbiota diversity and composition: greater alpha diversity during the dry compared to the rainy season in S. bicanthalis, the opposite pattern in S. aeneus, and no seasonal differences in S. grammicus and S. spinosus. Our findings indicated a positive association between gut bacterial composition and dietary composition for S. bicanthalis and S. grammicus, but bacterial diversity did not increase linearly with dietary richness in any lizard species. In addition, seasonality affected bacterial composition, and microbial community similarity increased between S. aeneus and S. bicanthalis, as well as between S. grammicus and S. spinosus. Together, our results illustrate that seasonal variation and dietary composition play a role in shaping gut microbiota in lizard populations, but this is not a rule and other ecological factors influence microbiota variation.

Development and reproduction of Scirtothrips dorsalis (Thysanoptera: Thripidae) on six host plant species.

Host plants can strongly influence the population performance of insects. Here, we investigated the development, survival, and oviposition of Scirtothrips dorsalis Hoodon 6 host plants-Camellia sinensis ( L.) Kuntze (Ericales: Theaceae), Rosa chinensis Jacq. (Rosales: Rosaceae), Capsicum annuum L. (Solanales: Solanaceae), Eustoma grandiflorum (Hook.) G.Don (Gentianales: Gentianaceae), Glycine max (L.) Merr. (Fabales: Fabaceae), and Cucumis sativus L. (Cucurbitales: Cucurbitaceae), and constructed life tables for S. dorsalis on each plant. Significant differences in S. dorsalis development on the host species were observed. The mean developmental period from egg to adult was 11.45 ± 0.12 days, 11.24 ± 0.13 days, 12.08 ± 0.15 days, 12.28 ± 0.12 days, 12.67 ± 0.10 days, and 13.03 ± 0.11 days on C. sinensis, R. chinensis, C. annuum, E. grandiflorum, G. max, and C. sativus, respectively. Significant differences in survival of S. dorsalis were observed, namely, C. sinensis ≈ R. chinensis > E. grandiflorum ≈ C. annuum > G. max > C. sativus. The highest and lowest fecundities of S. dorsalis were recorded on R. chinensis (60.44 ± 1.53) and C. sativus (28.64 ± 1.02), respectively. Both of the net reproductive rate (R0) and intrinsic rate of increase (rm) of S. dorsalis were the highest on R. chinensis, with the values of 27.63 ± 0.58 and 0.142 ± 0.002, respectively; while the lowest on C. sativus, with the values of 8.81 ± 0.12 and 0.092 ± 0.003, respectively. Thus, R. chinensis was found to be the most suitable host, but C. sativus was the least suitable, for population development of S. dorsalis. Our results provide important information for the key control of S. dorsalis among different host plants.

Local environment shapes milk microbiomes while evolutionary history constrains milk macronutrients in captive cercopithecine primates.

Milk is a complex biochemical fluid that includes macronutrients and microbiota, which, together, are known to facilitate infant growth, mediate the colonization of infant microbiomes, and promote immune development. Examining factors that shape milk microbiomes and milk-nutrient interplay across host taxa is critical to resolving the evolution of the milk environment. Using a comparative approach across four cercopithecine primate species housed at three facilities under similar management conditions, we test for the respective influences of the local environment (housing facility) and host species on milk (a) macronutrients (fat, sugar, and protein), (b) microbiomes (16S rRNA), and (c) predicted microbial functions. We found that milk macronutrients were structured according to host species, while milk microbiomes and predicted function were strongly shaped by the local environment and, to a lesser extent, host species. The milk microbiomes of rhesus macaques (Macaca mulatta) at two different facilities more closely resembled those of heterospecific facility-mates compared to conspecifics at a different facility. We found similar, facility-driven patterns of microbial functions linked to physiology and immune modulation, suggesting that milk microbiomes may influence infant health and development. These results provide novel insight into the complexity of milk and its potential impact on infants across species and environments.

Effects of long-term experimental warming on phyllosphere epiphytic bacterial and fungal communities of four alpine plants

The effects of climatic warming on phyllosphere microbial communities remain uncertain. In this study, the effects of long-term (>10 years) experimental warming on phyllosphere epiphytic bacterial and fungal communities of Carex alrofusca, Kobresia pygmaea, Potentilla bifurca and Stipa capillacea were examined in the Northern Tibet. Overall, warming increased bacterial α-diversity, but reduced fungal α-diversity across the four host plants. Warming altered the bacterial and fungal community compositions mainly by increasing Actinobacteria, Firmicutes and pathotroph-saprotroph fungi, and reducing Basidiomycota and symbiotroph fungi across the four host plants. Warming increased the relative effect of the ‘drift & others’ process in the bacterial community, but reduced the relative effect of the ‘dispersal limitation’ process in the bacterial community and the relative effect of the ‘homogeneous selection’ process in the fungal community across the four host plants. The overall warming effects on the bacterial and fungal communities may be due to overall warming effects on temperature, leaf morphology structure and physicochemical properties, ecological processes of community assembly and topological parameters of species co-occurrence networks of bacteria and fungi. Warming altered the bacterial species co-occurrence network mainly by increasing the vertex, clustering coefficient and heterogeneity, while reducing the average path length and network diameter across host species. Warming altered the fungal species co-occurrence network mainly by increasing the network diameter and reducing the vertex across host species. Warming effects on bacterial and fungal communities varied among host plants, which may be due to the diverse responses to warming of plant height, leaf malondialdehyde, ecological processes of community assembly and topological parameters of species co-occurrence network. Therefore, warming can alter phyllosphere epiphytic bacterial and fungal communities of alpine plants. Such changes varied among host plants and may cause adverse effects on the host plants.

Host specificity of plant‐associated bacteria is negatively associated with genome size and host abundance along a latitudinal gradient

AbstractHost specialization plays a critical role in the ecology and evolution of plant–microbe symbiosis. Theory predicts that host specialization is associated with microbial genome streamlining and is influenced by the abundance of host species, both of which can vary across latitudes, leading to a latitudinal gradient in host specificity. Here, we quantified the host specificity and composition of plant–bacteria symbioses on leaves across 329 tree species spanning a latitudinal gradient. Our analysis revealed a predominance of host‐specialized leaf bacteria. The degree of host specificity was negatively correlated with bacterial genome size and the local abundance of host plants. Additionally, we found an increased host specificity at lower latitudes, aligning with the high prevalence of small bacterial genomes and rare host species in the tropics. These findings underscore the importance of genome streamlining and host abundance in the evolution of host specificity in plant‐associated bacteria along the latitudinal gradient.

Root nodules of red alder (Alnus rubra) and Sitka alder (Alnus viridis ssp. sinuata) are inhabited by taxonomically diverse cultivable microbial endophytes

AbstractThe root nodules of actinorhizal plants are home to nitrogen‐fixing bacterial symbionts, known as Frankia, along with a small percentage of other microorganisms. These include fungal endophytes and non‐Frankia bacteria. The taxonomic and functional diversity of the microbial consortia within these root nodules is not well understood. In this study, we surveyed and analyzed the cultivable, non‐Frankia fungal and bacterial endophytes of root nodules from red and Sitka alder trees that grow together. We examined their taxonomic diversity, co‐occurrence, differences between hosts, and potential functional roles. For the first time, we are reporting numerous fungal endophytes of alder root nodules. These include Sporothrix guttuliformis, Fontanospora sp., Cadophora melinii, an unclassified Cadophora, Ilyonectria destructans, an unclassified Gibberella, Nectria ramulariae, an unclassified Trichoderma, Mycosphaerella tassiana, an unclassified Talaromyces, Coniochaeta sp., and Sistotrema brinkmanii. We are also reporting several bacterial genera for the first time: Collimonas, Psychrobacillus, and Phyllobacterium. Additionally, we are reporting the genus Serratia for the second time, with the first report having been recently published in 2023. Pseudomonas was the most frequently isolated bacterial genus and was found to co‐inhabit individual nodules with both fungi and bacteria. We found that the communities of fungal endophytes differed by host species, while the communities of bacterial endophytes did not.

Stilbocrea banihashemiana, an emerging fungal pathogen associated with canker and dieback diseases in walnut trees

Persian walnut (Juglans regia L.), a globally significant and economically important tree, is cultivated worldwide for its valuable wood and nutritious nuts. In this study, we conducted a comprehensive survey of the trees exhibiting signs of distress, such as trunk and branch cankers, dieback, and wood discoloration, in the central region of Fars Province in Iran. Initial morphological identification indicated that the fungal isolates recovered from the canker symptoms belonged to a newly emerged ascomycete pathogen, Stilbocrea banihashemiana. The identification was further confirmed by utilizing species-specific primer pairs for S. banihashemiana. Pathogenicity assessments on detached shoots and one-year-old saplings revealed the isolates' ability to induce wood necrosis symptoms. The cross-pathogenicity test with isolates of S. banihashemiana from walnut and other reported hosts, including fig, loquat, and pomegranate was performed on detached branches. The results indicated varying levels of aggressiveness of the isolates across the different host species examined. To our knowledge, this is the first global confirmation of the isolation of S. banihashemiana from infected Persian walnut trees and the assessment of its pathogenicity on this new host.