Biology subjects

Michalik, A.

Publications and source records attributed to Michalik, A..

15 recordsLinked to original sources

bioRxiv2026

The road to nowhere: geolocation-by-genotype traces large-scale yellow-browed warbler vagrancy to central Siberia

Vagrant animals - individuals found far outside their normal range - offer powerful natural experiments for understanding migratory mechanisms. The yellow-browed warbler (Phylloscopus inornatus) provides perhaps the best-yet example, typically migrating from Siberia to South/Southeast Asia yet found in increasingly large numbers in Western Europe. This represents a strikingly unresolved evolutionary puzzle: why do so many migrants consistently move in almost the complete wrong direction? A critical first step toward solving this enigma is determining where these birds come from. If vagrants came from the proximal western range edge this would imply simple disorientation, whilst a more easterly origin could imply large-scale reverse misorientation. Here, we develop a geolocation-by-genotype algorithm for low-coverage whole-genome resequencing data collected from feathers. Our method identifies spatially informative SNPs; clusters them to account for covariance in allele frequency through space; and employs a bootstrapped maximum-likelihood framework to estimate spatial origin with uncertainty. Applied to more than 80 European-caught birds, our results place their origin in central Siberia (118{degrees}E; 89-134{degrees}E [95% CI]); over 2000km east of the western range edge. These results suggest mass misorientation in a near-reverse direction, and highlight the yellow-browed warbler as an exceptional system for probing the mechanism, ontogeny and evolution of migration.

animal behavior and cognition↗

bioRxiv2025

Contrasting genomic trajectories of Bartonellaceae symbionts of planthoppers

Symbioses with microorganisms have shaped the nutritional biology and evolution of many insects. For example, several ant clades have adapted to nutrient-poor diets through symbiosis with a specific clade of bacteria in the family Bartonellaceae (Hyphomicrobiales), notorious for also including virulent vertebrate pathogens. Here we show that Bartonellaceae phylogenetically placed within the clade that has only encompassed ant symbionts to date - Candidatus genus Tokpelaia - have established as symbionts in four different clades of planthoppers (Insecta: Hemiptera: Fulgoromorpha). Genome size and contents indicate different levels of integration of these strains into the planthopper host biology and their diverse roles. Symbionts infecting one of the clades have some of the largest genomes among Bartonellaceae, at ca. 2 Mb, two others are under 700 kb, and the fourth is reduced to barely 158 kb. The planthopper-associated Tokpelaia strains with larger genomes, similarly to ant symbionts, encode multiple amino acid and vitamin biosynthesis genes, complementing the degraded nutritional capabilities of their hosts ancient heritable endosymbionts. Strikingly, the smallest Tokpelaia genome lacks any genes linked to essential amino acid biosynthesis, in contrast to all other known insect-associated bacteria with genomes of comparable size. We identified a single vitamin biosynthesis gene and iron-sulfur cluster assembly genes as its only putative contributions to the host biology. Our results broaden the host spectrum of non-pathogenic Bartonellaceae, indicating that they have contributed to nutrition and symbiotic consortium function in diverse diet-restricted host clades. They also highlight an unexpectedly broad range of evolutionary outcomes for this important bacterial group. SignificanceMany insects rely on bacterial partners to overcome nutrient-poor diets, yet the diversity and evolutionary trajectories and outcomes for these associations remain unclear. Our discovery of Bartonellaceae bacteria in planthoppers improves the understanding of the host range of these broadly relevant bacteria best-known as vertebrate pathogens. The finding that these planthopper symbionts generally have the capacity to produce essential amino acids and vitamins relevant to hosts and likely form long-term symbiotic associations agree with the expectations for sap-sucking hemipteran symbionts. However, the breadth of sizes and functions of the newly assembled genomes substantially expand the known range of states for Bartonellaceae, and their evolutionary trajectories. In particular, the identification of a strain with an ultra-reduced genome of only 158kb with no amino acid biosynthetic functions contrasts with all other known insect-symbiotic bacteria with genomes in a similar size range. This study also indicates how symbionts may enable the degeneration, functional loss, and evolution of other bacteria residing in the same host.

ecology↗

bioRxiv2025

The tiniest genomes shrink much further: extreme reductive evolution in planthopper symbionts

Strictly heritable endosymbiotic bacteria that provide limiting nutrients to sap-sucking hemipteran insects are known for their highly reduced genomes conserved in organization and function. Here, we show how in ancestral endosymbionts of planthoppers, Sulcia and Vidania, gradually losing genes during [~]263 my of co-diversification with hosts, co-infections by additional microbes and host ecological switches coincided with more dramatic genomic changes. At its extremes, this has resulted in the smallest non-organellar bacterial genomes known, at barely 50-52 kb. Such minuscule Vidania genomes evolved convergently in two planthopper superfamilies, and are strikingly similar in gene contents, including the ability to produce a single amino acid (phenylalanine) for the host. Losing many additional cell-function genes places them among mitochondria in the level of host dependence, further blurring the bacteria-organelle boundary. One-sentence summaryWe present the smallest bacterial genomes known and evaluate the patterns and processes of their reductive evolution

evolutionary biology↗

bioRxiv2025

Dissecting multitrophic interactions: the relationships among Entomophthora, their dipteran hosts, and associated bacteria

Interactions with microorganisms from across a range of mutualism-to-pathogenicity spectrums shape the biology of insects at all levels - from individual traits to populations and communities. However, the understanding of pathogens attacking non-model insect species in natural ecosystems, or their interactions with other insect-associated microorganisms, is fragmentary. Here, we tested a conceptually novel approach - the simultaneous sequencing of insect, fungal, and bacterial marker gene amplicons - as a means of dissecting interactions among entomopathogenic fungi in the genus Entomophthora and their dipteran hosts in South Greenland. We aimed to describe the taxonomic diversity of Entomophthora-killed flies, their pathogens, and the bacterial diversity within a set of field-collected dead insects exhibiting signs of Entomophthora infection. Across nine collected dipteran species, we identified multiple Entomophthora genotypes, with strong but not perfect patterns of host-specificity across the five targeted marker regions. Additionally, we found consistent differences in bacterial community composition among fungus-killed fly species and sampling sites. Our results substantially expand the knowledge of Entomopthora diversity and host associations while providing the very first insights into associated bacteria and their potential roles. We also conclude that multi-target amplicon sequencing can be a powerful tool for addressing broad questions about biological interactions in diverse natural communities.

ecology↗

bioRxiv2024

Peasants at the queen's table?: The microbiome's dynamics throughout swarming preparation in honey bees (Apis mellifera)

The intricate relationship between hosts and bacterial symbionts was crucial for the evolution of multiple insect clades. Western honey bees (Apis mellifera) have distinctive and highly stable microbiomes in terms of bacterial taxonomic composition. However, despite the significant development of molecular techniques observed in recent decades, we still are far from understanding much about the dynamics of honey bees microbiomes in terms of their strain diversity and quantities. The overall stable composition of their microbiome and complex behavior make honey bees a perfect model species for studying the gut-brain axis, where the gut microbiome can efficiently influence the hosts behavior. Here, by implementing high-throughput amplicon sequencing of bacterial 16S rRNA V4 and V1V2 hypervariable regions alongside a cutting-edge quantification approach, we aimed to describe the dynamic in honey bee young workers microbiome composition and quantity throughout swarming preparation. Our results show no changes in microbial absolute abundances throughout the swarming preparation among young worker bees. The V4 and V1V2 datasets congruently reconstructed microbial composition with some notable exceptions, and differential abundance analysis indicated that Bombella and Bartonella significantly changed over batches.

evolutionary biology↗

bioRxiv2024

A new tool in a toolbox: Addressing challenges in high-throughput microbiota surveys across diverse wild insects

With their significant effects on the biology of higher organisms, host-associated microbiota has attracted the research communitys attention. The rapid progress in sequencing techniques has greatly facilitated microbial community characterization. However, the most popular surveying technique, marker gene amplicon sequencing, has multiple caveats that are not often addressed satisfactorily, including the uncertainty about the identity of the surveyed wild-caught specimens, variable and sometimes very low abundance of microbes in some samples, or reagent- and cross-contamination. As a result, researchers often obtain incomplete, biased, and sometimes totally incorrect microbial community profiles. Here, we present a versatile, cost-effective, and high-throughput quantitative multi-target amplicon sequencing workflow for the characterization of host-associated microbial communities, combining laboratory and bioinformatic steps and addressing most of the known methodological issues. Optimized for the study of the microbiota of wild insects, it can be easily adapted for other sample types. Outputs include contamination-controlled data on the absolute abundance and identity of microbes present in insect samples, both at genotype- and OTU-level, as well as host barcodes alongside information on parasite infections. Using 1384 samples from Zackenberg Valley, NE Greenland, we demonstrate the potential of the workflow to study insect and symbiont diversity patterns across a large portion of a diverse natural community.

ecology↗

bioRxiv2024

Phylogenomics resolves the relationship and the evolutionary history of planthoppers (Insecta: Hemiptera: Fulgoromorpha)

Planthoppers (Hemiptera: Fulgoromorpha) are a species-rich and globally distributed insect clade with high economic, ecological, and evolutionary importance. However, the relationships among planthopper lineages and families remain unclear. Previous efforts based on inconsistent morphological traits, a few genes, or limited sampling often resulted in conflicting tree topologies. Here, we used genome-level data to assemble 1164 nuclear single-copy genes and 13 mitochondrial protein-coding genes for 149 planthopper species representing 19 out of 21 extant families. Additional markers were added from published mitogenomes, expanding our sampling to 285 species. These markers were used for Maximum Likelihood-based tree inference and dating analyses. The newly inferred phylogenies validated well-accepted relationships and recovered novel placements. Taxonomic conclusions include the establishment of a new family Borysthenidae stat. rev. within Delphacoidea and a new superfamily Meenoploidea superfam. nov. including redefined Kinnaridae stat. rev. and Meenoplidae stat. rev., the confirmation of the monophyletic family Achilixiidae outside the Achilidae-Derbidae clade, and the transfer of tribes Lyncidini and Amyclini to Dictyopharidae and the genus Madagascaritia to Fulgoridae. The time analyses based on 57 nuclear markers and 30 fossils dated the origin of crown Fulgoromorpha back to Guadalupian, Permian ([~]263 Ma), close to the maximum constraint at 267.3 Ma, while applying an older root constraint resulted in an origin in Mississippian, Carboniferous ([~]332 Ma). While future sampling of unstudied fauna in unexplored regions or habitats may change the topology, the current phylogenomic analysis will serve as a solid foundation for research into planthopper ecology, evolution, and significance.

evolutionary biology↗

bioRxiv2024

Limited variation in microbial communities across populations of Macrosteles leafhoppers (Hemiptera: Cicadellidae)

Microbial symbionts play important roles in insect biology, but their diversity, distribution, and dynamics over time across host populations are poorly understood. We surveyed the spatio-temporal distribution of bacterial symbionts in the broadly distributed and economically significant leafhopper genus Macrosteles, with emphasis on Macrosteles laevis, using host and symbiont marker gene amplicon sequencing. The cytochrome oxidase I (COI) gene data revealed no strong genetic differentiation across M. laevis populations, significant levels of heteroplasmy, and multiple cases of parasitoid infections. 16S rRNA data confirmed the universal presence of the ancient nutritional endosymbionts Sulcia and Nasuia and a high prevalence of Arsenophonus. Interestingly, in contrast to most previously surveyed species, in M. laevis we found only occasional cases of infection with facultative endosymbionts and other bacteria. There was no significant variation in symbiont prevalence across populations, or among sampling years for the same population. Facultative endosymbionts including Rickettsia, Wolbachia, Cardinium, and Lariskella, were more common in other Macrosteles species. Combined, our data demonstrate that not all species show clear spatial and temporal variation in genetic structure and microbial prevalence. However, simultaneous characterization of host and symbiont marker gene amplicons in large insect collections can help understand the dynamics of host-microbe interactions.

evolutionary biology↗

bioRxiv2023

Facultatively intra-bacterial localization of a planthopper endosymbiont as an adaptation to its vertical transmission

Transovarial transmission is the most reliable way of passing on essential nutrient- providing endosymbionts from mothers to offspring. However, not all endosymbiotic microbes follow the complex path through the female host tissues to oocytes on their own. Here we demonstrate an unusual transmission strategy adapted by one of the endosymbionts of the planthopper Trypetimorpha occidentalis (Hemiptera: Tropiduchidae) from Bulgaria. In this species, an Acetobacteraceae endosymbiont is transmitted transovarially within deep invaginations of cellular membranes of an ancient endosymbiont Sulcia - strikingly resembling recently described plant virus transmission. However, in males, Acetobacteraceae colonizes the same bacteriocytes as Sulcia but remains unenveloped. Then, the unusual endobacterial localization of Acetobacteraceae observed in females appears to be a unique adaptation to maternal transmission. Further, symbionts genomic features, including encoding essential amino acid biosynthetic pathways and very similar to a recently described psyllid symbiont, suggest a unique combination of ability to horizontally transmit among species and confer nutritional benefits. The close association with Acetobacteraceae symbiont correlates with the so-far- unreported level of genomic erosion of ancient nutritional symbionts of this planthopper. In Sulcia, this is reflected in substantial changes in genomic organization, reported for the first time in the symbiont renown for its genomic stability. In Vidania, substantial gene loss resulted in one of the smallest genomes known, at 109 kb. Thus, the symbionts of T. occidentalis display a combination of unusual adaptations and genomic features that expand our understanding of how insect-microbe symbioses may transmit and evolve. Significance StatementReliable transmission across host generations is a major challenge for bacteria that associate with insects, and independently established symbionts have addressed this challenge in different ways. The facultatively endobacterial association of Acetobacteraceae symbiont, enveloped by cells of ancient nutritional endosymbiont Sulcia in females but not males of the planthopper Trypetimorpha occidentalis, appears to be a unique adaptation to maternal transmission. Acetobacteraceaes genomic features indicate its unusual evolutionary history, and the genomic erosion experienced by ancient nutritional symbionts demonstrates apparent consequences of such close association. Combined, this multi-partite symbiosis expands our understanding of the diversity of strategies that insect symbioses form and some of their evolutionary consequences.

cell biology↗

bioRxiv2023

Division of labour within psyllids: Metagenomics reveals an ancient dual endosymbiosis with metabolic complementarity in the genus Cacopsylla

Hemipteran insects are well-known for their ancient associations with beneficial bacterial endosymbionts, particularly nutritional symbionts providing the host with essential nutrients such as amino acids or vitamins lacking from the hosts diet. Thereby, these primary endosymbionts enable the exploitation of nutrient-poor food sources such as plant sap or vertebrate blood. In turn, the strictly host-associated lifestyle strongly impacts the genome evolution of the endosymbionts, resulting in small and degraded genomes. Over time, even the essential nutritional functions can be compromised, leading to the complementation or replacement of an ancient endosymbiont by another, more functionally versatile, bacterium. Herein, we provide evidence for a dual primary endosymbiosis in several psyllid species. Using metagenome sequencing, we produced the complete genome sequences of both the primary endosymbiont Candidatus Carsonella ruddii and an as yet uncharacterized Enterobacteriaceae bacterium from four species of the genus Cacopsylla. The latter represents a new psyllid-associated endosymbiont clade for which we propose the name Candidatus Psyllophila symbiotica. Fluorescent in situ hybridisation confirmed the co-localization of both endosymbionts in the bacteriome. The metabolic repertoire of Psyllophila is highly conserved across host species and complements the tryptophan biosynthesis pathway that is incomplete in the co-occurring Carsonella. Unlike co-primary endosymbionts in other insects, the genome of Psyllophila is almost as small as the one of Carsonella, indicating an ancient co-obligate endosymbiosis rather than a recent association to rescue a degrading primary endosymbiont. IMPORTANCEHeritable beneficial bacterial endosymbionts have been crucial for the evolutionary success of numerous insects, enabling the exploitation of nutritionally limited food sources such as vertebrate blood and plant sap. Herein, we describe a previously unknown dual endosymbiosis in the psyllid genus Cacospylla, consisting in the primary endosymbiont Candidatus Carsonella ruddii and a co-occurring Enterobacteriaceae bacterium for which we propose the name Candidatus Psyllophila symbiotica. Its localization within the bacteriome and its small genome size confirm that Psyllophila is a co-primary endosymbiont widespread within the genus Cacopsylla. Despite its highly eroded genome, Psyllophila complements the tryptophan biosynthesis pathway that is incomplete in the co-occurring Carsonella. Moreover, the genome of Psyllophila is almost as small as the one of Carsonella, indicating an ancient dual endosymbiosis rather than a recent acquisition of a new symbiont. Hence, our results shed light on the dynamic interactions of psyllids and their endosymbionts over evolutionary time.

evolutionary biology↗

bioRxiv2022

Variable organization of symbiont-containing tissue across planthoppers hosting different heritable endosymbionts

Sap-feeding hemipteran insects live in associations with diverse heritable endosymbiotic bacteria and fungi that provide essential nutrients deficient in their diets. These symbionts typically reside in bacteriomes, dedicated organs made up of specialized cells termed bacteriocytes. The bacteriome organization varies between insect clades that are ancestrally associated with different microbes. As these symbioses evolve and additional microorganisms complement or replace the ancient associates, the organization of the symbiont-containing tissue becomes even more variable. Planthoppers (Hemiptera: Fulgoromorpha) are ancestrally associated with bacterial symbionts Sulcia and Vidania, but in many of the planthopper lineages, these symbionts are now accompanied or have been replaced by other heritable bacteria (e.g., Sodalis, Arsenophonus, Purcelliella) or fungi. We know the identity of many of these microbes, but the symbiont distribution within the host tissues and the bacteriome organization have not been systematically studied using modern microscopy techniques. Here, we combine light, fluorescence, and transmission electron microscopy with phylogenomic data to compare symbiont tissue distributions and the bacteriome organization across planthoppers representing 15 families. We identify and describe seven primary types of symbiont localization and seven types of the organization of the bacteriome. We show that Sulcia and Vidania, when present, occupy distinct bacteriomes distributed within the body cavity. The more recently acquired gammaproteobacterial and fungal symbionts generally occupy separate groups of cells organized into distinct bacteriomes or mycetomes, distinct from those with Sulcia and Vidania. They can also be localized in the cytoplasm of fat body cells. Alphaproteobacterial symbionts colonize a wider range of host body habitats: Asaia-like symbionts often colonize the host gut lumen, whereas Wolbachia and Rickettsia are usually scattered across tissues and cell types, including bacteriocytes containing other symbionts, bacteriome sheath, fat body cells, gut epithelium, as well as hemolymph. However, there are exceptions, including Gammaproteobacteria that share bacteriome with Vidania, or Alphaproteobacteria that colonize Sulcia cells. We discuss how planthopper symbiont localization correlates with their acquisition and replacement patterns and the symbionts likely functions. We also discuss the evolutionary consequences, constraints, and significance of these findings.

evolutionary biology↗

bioRxiv2022

Genome comparison reveals inversions and alternative evolutionary history of nutritional endosymbionts in planthoppers (Hemiptera: Fulgoromorpha)

The evolutionary success of sap-feeding hemipteran insects in the suborder Auchenorrhyncha was enabled by nutritional contributions from their heritable endosymbiotic bacteria. However, the symbiont diversity, functions, and evolutionary origins in this large insect group have not been broadly characterized using genomic tools. In particular, the origins and relationships among ancient betaproteobacterial symbionts Vidania (in Fulgoromorpha) and Nasuia/Zinderia (in Cicadomorpha) are uncertain. Here, we characterized the genomes of Vidania and Sulcia from three Pyrops planthoppers (family Fulgoridae) to understand their metabolic functions and evolutionary histories. Like in previously characterized planthoppers, these symbionts share nutritional responsibilities, with Vidania providing seven out of ten essential amino acids. Sulcia lineages across the Auchenorrhyncha have a highly conserved genome but with multiple independent rearrangements occurring in an early ancestor of Cicadomorpha or Fulgoromorpha and in a few succeeding lineages. Genomic synteny was also observed within each of the betaproteobacterial symbiont genera Nasuia, Zinderia, and Vidania, but not across them, which challenges the expectation of a shared ancestry for these symbionts. The further comparison of other biological traits strongly suggests an independent origin of Vidania early in the planthopper evolution and possibly of Nasuia and Zinderia in their respective host lineages. Originality-Significance StatementWe sequenced and characterized the genomes of two ancient nutritional symbionts, Sulcia and Vidania, in three species from the genus Pyrops in the species- and symbiont-rich but understudied insect clade, Fulgoromorpha (planthoppers). We describe--for the first time--several independent genome rearrangements in Sulcia, which is often cited as a premier example of extreme genome stability spanning hundreds of millions of years. We also show a global lack of synteny across the genomes of the Auchenorrhynchan betaproteobacterial symbionts (Vidania, Nasuia, and Zinderia). This result is unexpected given previous hypotheses of a common origin for these symbionts >250 million years ago alongside Sulcia. Taken together, we suggest an independent origin of Vidania and possibly of Nasuia and Zinderia symbiont lineages as well. This hypothesis further links the potential acquisition of novel nutritional endosymbiont lineages with the emergence of auchenorrhyncham superfamilies.

genomics↗

bioRxiv2022

Till evolution do us part: The diversity of symbiotic associations across populations of Philaenus spittlebugs

Symbiotic bacteria have played crucial roles in the evolution of sap-feeding insects and can strongly affect host function. However, their diversity and distribution within species are not well understood; we dont know to what extent environmental factors or associations with other species may affect microbial community profiles. Here, we sequenced host and bacterial marker gene amplicons to survey the bacterial community composition across multiple populations of Philaenus spittlebugs. Host mitochondrial sequence data confirmed morphology-based identification of 6 species and revealed two divergent clades of Philaenus spumarius. All of them hosted the primary symbiont Sulcia that was almost always accompanied by Sodalis. Interestingly, populations and individuals often differed in the presence of Sodalis sequence variants, suggestive of intra-genome 16S rRNA variant polymorphism combined with rapid genome evolution and/or recent additional infections or replacements of the co-primary symbiont. The prevalence of facultative endosymbionts, including Wolbachia, Rickettsia, and Spiroplasma, varied among populations. Notably, COI amplicon data also showed that nearly a quarter of P. spumarius were infected by parasitoid flies (Verralia aucta). One of the Wolbachia OTUs was exclusively present in Verralia-parasitized specimens, suggestive of parasitoids as their source and highlighting the utility of host gene amplicon sequencing in microbiome studies.

ecology↗

bioRxiv2021

Alternative transmission patterns in independently acquired nutritional co-symbionts of Dictyopharidae planthoppers

Sap-sucking hemipterans host specialized, heritable microorganisms that supplement their unbalanced diet with essential nutrients. These microbes show unusual features that provide a unique perspective on the evolution of life but have not been systematically studied. Here, we combine microscopy with high-throughput sequencing to revisit 80-year-old reports on the diversity of symbiont transmission modes in a broadly distributed planthopper family Dictyopharidae. We show that in all species examined, the ancestral nutritional endosymbionts Sulcia and Vidania are complemented by co-primary symbionts, either Arsenophonus or Sodalis, acquired several times independently by different host lineages. Like in other obligate sap-feeders, the ancestral symbionts produce essential amino acids, whereas co-primary symbionts contribute to the biosynthesis of B vitamins. These symbionts reside within separate bacteriomes within the abdominal cavity, although in females, Vidania also occupies bacteriocytes in the rectal organ. Notably, the symbionts are transmitted from mothers to offspring in two alternative ways. In most examined species, all nutritional symbionts simultaneously infect the posterior end of the full-grown (vitellogenic) oocytes and next gather in their perivitelline space. In contrast, in other species, Sodalis colonizes the cytoplasm of the anterior pole of young (previtellogenic) oocytes forming a cluster separate from the "symbiont ball" formed by late-invading Sulcia and Vidania. Our data add to evidence on frequent replacements of gammaproteobacterial symbionts combined with the relative functional stability of the nutritional functions during the evolution of sap-feeding insects, and show how newly-arriving microbes may utilize different strategies to establish long-term heritable symbiosis. Significance statementSup-sucking hemipterans host ancient heritable microorganisms that supplement their unbalanced diet with essential nutrients, and which have repeatedly been complemented or replaced by other microorganisms. They need to be reliably transmitted to subsequent generations through the reproductive system, and often they end up using the same route as the ancient symbionts. We show for the first time that in a single family of planthoppers, the complementing symbionts that have established infections independently utilize different transmission strategies, one of them novel, with the transmission of different microbes separated spatially and temporarily. These data show how newly-arriving microbes may utilize different strategies to establish long-term heritable symbiosis.

evolutionary biology↗

bioRxiv2018

Changes in endosymbiont complexity drive host-level compensatory adaptations in cicadas

For insects that depend on one or more bacterial endosymbionts for survival, it is critical that these bacteria are faithfully transmitted between insect generations. Cicadas harbor two essential bacterial endosymbionts, Sulcia muelleri and Hodgkinia cicadicola. In some cicada species, Hodgkinia has fragmented into multiple distinct cellular and genomic lineages that can differ in abundance by more than two orders of magnitude. This complexity presents a potential problem for the host cicada, because low-abundance-but-essential Hodgkinia lineages risk being lost during the symbiont transmission bottleneck from mother to egg. Here we show that all cicada eggs seem to receive the full complement of Hodgkinia lineages, and that in cicadas with more complex Hodgkinia this outcome is achieved by increasing the number of Hodgkinia cells transmitted by up to six-fold. We further show that cicada species with varying Hodgkinia complexity do not visibly alter their transmission mechanism at the resolution of cell biological structures. Together these data suggest that a major cicada adaptation to changes in endosymbiont complexity is an increase in the number of Hodgkinia cells transmitted to each egg. We hypothesize that the requirement to increase the symbiont titer is one of the costs associated with Hodgkinia fragmentation.

evolutionary biology↗