Biology subjects

Almeida Santos, A.

Publications and source records attributed to Almeida Santos, A..

7 recordsLinked to original sources

bioRxiv2026

A horizontally acquired and recurrently expanded glycoside hydrolase subfamily across leafhoppers

Horizontal gene transfer from bacteria is a known source of metabolic novelty in insects, yet how these acquisitions diversify and persist over evolutionary time scales remains poorly understood. Here, we reconstructed the evolutionary history of the bacterial glycoside hydrolase subfamily GH5-40 across leafhoppers (Cicadellidae). We annotated 24 genomes and identified 87 GH5-40 genes encoding 113 catalytic domains across 23 leafhopper species, with copy numbers ranging from 1 to 19 genes per genome. Maximum-likelihood phylogenetic analyses recovered all leafhopper GH5-40 domains as a single clade nested within Actinobacteria, supporting one ancestral acquisition followed by extensive lineage-specific duplication of both genes and catalytic domains. Seventeen genes encode 2 to 4 tandem catalytic domains connected by disordered linkers, and a four-domain architecture recurs independently in two divergent leafhopper subfamilies. Recombinant enzymes from distantly related species displayed contrasting substrate preferences for {beta}-glucans and {beta}-mannans in vitro, despite GH5-40 enzymes being classically characterized as endo-{beta}-1,4-mannanases.

evolutionary biology↗

bioRxiv2026

Is the winter survival area of Empoasca fabae continuously expanding?

O_LIEmpoasca fabae is a migratory pest that overwinters in the Southeastern United States (US) and damages crops throughout its summer range in North America. Its spring arrival has advanced by 9.7 days between 1951 and 2012, and increased damage is linked to warmer conditions that accelerate host and pest development. Yet whether this advance is also associated with a northward expansion of its winter survival area remains an open question. C_LIO_LIHere, we analyzed 126 years of minimum temperature data across the contiguous US to address this question. Using its winter survival threshold (-9{degrees}C), we calculated the annual winter survival area for E. fabae (temperature-only) and tested for time-series trends. We also mapped the potential overwintering area (temperature + winter hosts) under evergreen and pine-only forest scenarios. C_LIO_LIThe estimated winter survival area varies over 126 years, showing a nonlinear pattern. However, we found no significant trend, change-point year, or rate of change. This lack of significance was also observed when considering the 1951-2012 period. C_LIO_LIThe Southeastern US remained consistently suitable for winter survival, while the northern edge varied latitudinally, especially within the range of 35{degrees}-40{degrees}N, with no clear trend. C_LIO_LIPotential overwintering areas extend into Central Florida and the Texas Gulf Coastal Plain but exclude parts of Tennessee. In the pine-only scenario, the area in Mississippi and Alabama would be smaller. C_LIO_LIThe winter survival area for E. fabae has not continually expanded. The Southeastern US area remains suitable for over 126 years, whereas the northern range varies dynamically. C_LI GRAPHICAL ABSTRACT AND HIGHLIGHTS O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=78 SRC="FIGDIR/small/727670v1_ufig1.gif" ALT="Figure 1"> View larger version (22K): org.highwire.dtl.DTLVardef@1062508org.highwire.dtl.DTLVardef@696e4borg.highwire.dtl.DTLVardef@1c7ff29org.highwire.dtl.DTLVardef@14109c5_HPS_FORMAT_FIGEXP M_FIG C_FIG O_LIThe winter survival zone (temperature only) of Empoasca fabae has not expanded continuously over the past 126 years. C_LIO_LIThe Southeastern United States remained suitable over this period, with the maximum northward extent of potential survival reaching 45{degrees}N and high variation within the range of 35{degrees}-40{degrees}N. C_LIO_LIUpdated potential overwintering zones (temperature + winter hosts) extend into Central Florida and the Texas Gulf Coastal Plain. C_LI

ecology↗

bioRxiv2026

Genome-resolved metagenomics reveals conserved, flexible and emerging symbioses across global leafhoppers

BackgroundLeafhoppers are among the most important insect vectors of plant pathogens worldwide and depend on microbial symbionts to exploit nutrient-poor phloem diets. However, most studies of leafhopper-associated microbiota have focused on a limited number of taxa or marker-gene surveys, leaving the genomic diversity, ecological organization, and functional potential of these microbial communities poorly understood. Here, we generated the Global Leafhopper Microbiome Catalog by integrating genome-resolved metagenomics from 171 leafhopper species across 11 subfamilies and 13 countries, including the first microbiomes characterized from Arctic leafhoppers. ResultsDe novo assembly and genome reconstruction generated 337 high-quality non-redundant microbial genomes and 18.6 million non-redundant genes, substantially expanding the known microbial diversity associated with Cicadellidae, including several previously undescribed bacterial lineages. Comparative analyses revealed a recurrent modular microbiome architecture composed of: (i) a conserved core of obligate nutritional symbionts, dominated by Candidatus Karelsulcia and Candidatus Nasuia; (ii) a heterogeneous layer of secondary symbionts, including Wolbachia, Arsenophonus, Rickettsia, and Diplorickettsia; and (iii) a dynamic pool of environmentally acquired bacteria. While obligate symbionts remained highly conserved across divergent hosts, secondary and environmental taxa varied substantially among species and regions, suggesting repeated acquisition shaped by ecological filtering rather than host phylogeny alone. Comparative analyses between the specialist corn leafhopper Dalbulus maidis and the more polyphagous aster leafhopper Macrosteles quadrilineatus further showed that closely related vectors can maintain conserved ancestral symbionts while harboring markedly distinct accessory microbiomes. Arctic populations contained unique microbial assemblages enriched in functions associated with cold tolerance, oxidative stress, and reproductive manipulation. In addition, we identified numerous plant-associated bacteria, including phytoplasmas, spiroplasmas, Pantoea, and Erwinia, alongside taxa with predicted nutritional and plant growth-promoting functions. ConclusionsOur findings reveal that leafhopper microbiomes are structured through the interaction of ancient obligate symbioses and flexible environmentally responsive microbial layers. This work establishes a genome-resolved framework for understanding microbiome evolution in insect vectors and highlights the potential role of microbial community structure in host adaptation, pathogen ecology, and sustainable pest management.

microbiology↗

bioRxiv2025

'Candidatus Phytoplasma zeae': community-driven delineation of the maize bushy stunt phytoplasma, a Dalbulus-transmitted corn pathogen confined to the Americas

A novel phytoplasma species, Candidatus Phytoplasma zeae, is proposed based on ecological distinctiveness, vector specificity, whole-genome comparisons, and community consensus. This phytoplasma is associated with maize bushy stunt (MBS) disease in corn (Zea mays) and is transmitted exclusively by Dalbulus maidis and D. elimatus, two leafhopper species endemic to the Americas, and has been reported in Brazil, Colombia, Mexico, Peru, and several U.S. states. Here we sequenced and assembled the genome of MBS phytoplasma strains from Brazil, and U.S. to describe and propose this new species. Although the 16S rRNA gene sequence of the proposed reference strain, MBSP-BRRS, shares >99% identity with that of Ca. Phytoplasma asteris, key nucleotide polymorphisms distinguish Ca. P. zeae from other 16SrI-related phytoplasma species. Average nucleotide identity (ANI) and average amino acid identity (AAI) values between Ca. P. zeae and Ca. P. asteris are 97.70-98.00% and 96.65-96.88%, respectively, both near the established species delineation thresholds. Comparative genomic analyses revealed unique gene clusters in Ca. P. zeae associated with amino acid transport, defense mechanisms, and protein turnover, which may contribute to its specialization in corn. The ecological profile of Ca. P. zeae, including its narrow host range and restricted geographic distribution, supports its recognition as a novel species under Rule c of the IRPCM guidelines. The designation Candidatus Phytoplasma zeae is therefore proposed by members of the research community who have studied this pathogen for over a decade, with the MBSP-BrazilRS strain serving as the reference.

microbiology↗

bioRxiv2025

Diverse strains of aster yellows phytoplasma are associated with the potato leafhopper (Empoasca fabae) in Eastern Canada

Phytoplasmas are cell wall-less bacteria that are transmitted by phloem-feeding insects. In Canada, insect vectors of this pathogen are leafhoppers (Hemiptera: Cicadellidae), and they can contribute to significant economic losses. As climate change alters the composition and movement of insect communities, migratory species such as the potato leafhopper (Empoasca fabae, Harris 1841), one of the most abundant leafhoppers in Quebec, may play an emerging role in phytoplasma diseases. Although E. fabae is not currently confirmed to act as a vector, its frequent presence and abundance in fields, along with its potential to acquire phytoplasmas, deserve further investigation. In this study, we tested DNA from E. fabae collected in strawberry fields for the presence of Candidatus Phytoplasma using PCR, as well as inbred colonies for their ability to transmit this pathogen. The amplicons amplified from positive samples were cloned and sequenced to identify phytoplasma groups and subgroups. Our findings confirmed the presence of multiple Aster Yellows (16SrI-related) phytoplasma strains in E. fabae, based on phylogenetic analysis, restriction fragment length polymorphism (RFLP) profiling, and single-nucleotide polymorphism (SNP) profiles. However, the transmission assays did not show vector competence. We propose that although this leafhopper species hosts multiple, possibly new, phytoplasma subgroups, its capacity to transmit the disease remains limited and likely depends on high population density. Overall, these findings emphasize the importance of monitoring common pests like E. fabae as indicators of phytoplasma diversity in Eastern Canadian agricultural systems.

microbiology↗

bioRxiv2025

Uncovering diversity and climatic drivers of leafhopper-parasitoid dynamics in Canada

As climate change reshapes northern agroecosystems, leafhoppers (Hemiptera: Cicadellidae) are shifting their distributions, with implications for pest outbreaks and crop health. In Eastern Canada, we monitored strawberry farms from 2023 to 2024, collecting over 82,000 leafhoppers from 64 genera. Migratory species, Empoasca fabae and Macrosteles quadrilineatus, dominated captures, with sharp abundance increases above 16{degrees}C and 14{degrees}C, respectively, while local species declined under higher rainfall. A major finding was the first Canadian record of the corn pest Dalbulus maidis, a vector of multiple pathogens, likely introduced through long-distance dispersal. Insecticide applications generally failed to reduce leafhopper numbers, highlighting the limitations of current chemical control. Parasitism rates by Gonatopus wasps (Dryinidae), averaged ~3% but peaked in late summer at over 20%, primarily in M. quadrilineatus. Warmer temperatures and seasonal progression increased both parasitism probability and rates. Genomic analyses revealed at least three Gonatopus lineages, including the first complete mitochondrial genome for the genus from the New World, and confirmed multiple host species. We also recorded the first Canadian occurrence of G. clavipes. Our results demonstrate that parasitoids are active, climate-responsive, and capable of targeting dominant pest species. Together, these findings provide the first ecological and genomic baseline for leafhopper-parasitoid interactions in Canada. They point to the potential of conserving and enhancing native parasitoid populations as a foundation for climate-resilient, pesticide-free pest management strategies.

ecology↗

bioRxiv2025

Seasonal Phenology of Empoasca fabae (Hemiptera: Cicadellidae) in Quebec, Canada

Climate change is reshaping insect population dynamics in North America, notably impacting the migratory pest Empoasca fabae (Harris) (Hemiptera: Cicadellidae). While its phenology is well studied in the United States, knowledge gaps exist regarding its dynamics in Eastern Canada, one of its northernmost migration areas. Our study integrates degree-day models, CLIMEX ecological niche modeling, and field-collected data from Quebec to assess E. fabae seasonal phenology and monthly climatic suitability. Our results indicate that E. fabae completes one to two generations in Quebec, with earlier emergence and higher generational potential in warmer southeastern regions compared to cooler northeastern regions. CLIMEX modeling showed that suitable climatic conditions for E. fabae growth begin in April, peak from May to September, and decline by November. First adult captures occurred from late May to early June, with population peaks in June-July and a decrease by September. Observed adult peaks occurred earlier than predicted by degree-day models, suggesting that additional environmental factors, such as wind patterns and host plant availability, influence early-season population dynamics. This study provides a comprehensive understanding of E. fabae phenology in Quebec and highlights the importance of incorporating climatic and ecological modeling to predict future population trends. Further research on diapause onset, late-season persistence, and migration patterns is needed to refine predictive models and inform pest management strategies in Quebec. Understanding these factors will be essential in mitigating potential economic impacts amid ongoing climate change.

ecology↗