With a little help from my friends: the roles of microbial symbionts in insect populations and communities

To understand insect abundance, distribution and dynamics, we need to understand the relevant drivers of their populations and communities. While microbial symbionts are known to strongly affect many aspects of insect biology, we lack data on their effects on populations or community processes, or on insects' evolutionary responses at different timescales. How these effects change as the anthropogenic effects on ecosystems intensify is an area of intense research. Recent developments in sequencing and bioinformatics permit cost-effective microbial diversity surveys, tracking symbiont transmission, and identification of functions across insect populations and multi-species communities. In this review, we explore how different functional categories of symbionts can influence insect life-history traits, how these effects could affect insect populations and their interactions with other species, and how they may affect processes and patterns at the level of entire communities. We argue that insect-associated microbes should be considered important drivers of insect response and adaptation to environmental challenges and opportunities. We also outline the emerging approaches for surveying and characterizing insect-associated microbiota at population and community scales. This article is part of the theme issue 'Towards a toolkit for global insect biodiversity monitoring'.

Macrosemiafengi Wang sp. nov. from Yunnan and Guizhou, China (Hemiptera, Cicadidae, Cicadinae)

Background

The genus Macrosemia Kato, 1925 (Hemiptera, Cicadidae, Cicadinae, Dundubiini, Dundubiina) currently includes 16 species (excluding subspecies and varieties), mainly occurring in the Oriental Region. More than half of them, 10 species, are known from China, including one new species, described in the present study.

New information

A new species of cicada, Macrosemiafengi Wang sp. nov., is described from Yunnan and Guizhou, southwest China. Colour plates are presented to illustrate its diagnostic characters. The distribution map of the new species is also given.

A new species of Tanna Distant, 1905 from Yunnan, China (Hemiptera, Cicadidae, Cicadinae)

Background

The genus Tanna Distant, 1905 (Hemiptera, Cicadidae, Cicadinae, Leptopsaltriini, Leptopsaltriina) currently includes 23 species (three tentatively placed), with its actual geographical distribution in China, Japan, Nepal, Bhutan, Cambodia, Thailand and Vietnam. Most of them, 16 species, are known from China, including one new species here described.

New information

A new species of cicada, Tannafengi Wang sp. nov., is described from Yunnan, southwest China. Colour plates are presented to illustrate all diagnostic characters. An updated list of Tanna species occurring in China is provided.

The cicadas (Hemiptera: Cicadidae) of Uruguay with a key to known species and comments on species of the genus Acanthoventris Ruschel including the resurrection of a previously synonymized species

A synoptic list and key of the cicadas of Uruguay is provided to complete the country lists of the South American cicada fauna. Fidicina gastracanthophora Berg, 1879 is shown to be a distinct species, is resurrected from junior synonymy, and reassigned to a new genus to become Acanthoventris gastracanthophora (Berg, 1879) revised status, n. comb. The species is redescribed to facilitate differentiating it in its new genus. The female of Acanthventris drewseni (Stl, 1854), the type species of the genus, is described and illustrated. The known ranges of Acanthoventris charrua Ruschel (in Ruschel et al.), 2023, A. drewseni (Stl, 1854), A. iara Ruschel (in Ruschel et al.), 2023, A. igneus Ruschel (in Ruschel et al.), 2023, and A. olivarius Ruschel (in Ruschel et al.), 2023 are expanded. The currently known cicada fauna for Uruguay is determined to be 12 species, 10 genera, four tribes and three subfamilies, the lowest known alpha diversity of any South American country.

Mesozoic evolution of cicadas and their origins of vocalization and root feeding

Extant cicada (Hemiptera: Cicadoidea) includes widely distributed Cicadidae and relictual Tettigarctidae, with fossils ascribed to these two groups based on several distinct, minimally varying morphological differences that define their extant counterparts. However, directly assigning Mesozoic fossils to modern taxa may overlook the role of unique and transitional features provided by fossils in tracking their early evolutionary paths. Here, based on adult and nymphal fossils from mid-Cretaceous Kachin amber of Myanmar, we explore the phylogenetic relationships and morphological disparities of fossil and extant cicadoids. Our results suggest that Cicadidae and Tettigarctidae might have diverged at or by the Middle Jurassic, with morphological evolution possibly shaped by host plant changes. The discovery of tymbal structures and anatomical analysis of adult fossils indicate that mid-Cretaceous cicadas were silent as modern Tettigarctidae or could have produced faint tymbal-related sounds. The discovery of final-instar nymphal and exuviae cicadoid fossils with fossorial forelegs and piercing-sucking mouthparts indicates that they had most likely adopted a subterranean lifestyle by the mid-Cretaceous, occupying the ecological niche of underground feeding on root. Our study traces the morphological, behavioral, and ecological evolution of Cicadoidea from the Mesozoic, emphasizing their adaptive traits and interactions with their living environments.

Symbionts in Hodgkinia-free cicadas and their implications for co-evolution between endosymbionts and host insects

IMPORTANCE

Obligate symbionts in sap-sucking hemipterans are harbored in either the same or different organs, which provide a unique perspective for uncovering complicated insect-microbe symbiosis. Here, we investigated the distribution of symbionts in adults of 10 Hodgkinia-free cicada species of 2 tribes (Sonatini and Polyneurini) and the co-phylogeny between 65 cicada species and related symbionts (Sulcia and YLSs). We revealed that YLSs commonly colonize the bacteriome sheath besides the fat bodies in these two tribes, which is different with that in most other Hodgkinia-free cicadas. Co-phylogeny analyses between cicadas and symbionts suggest that genetic variation of Sulcia occurred in Sonatini and some other cicada lineages and more independent replacement events in the loss of Hodgkinia/acquisition of YLS in Cicadidae. Our results provide new information on the complex relationships between auchenorrhynchans and related symbionts.

Two new species and two new records for cicadas (Hemiptera: Cicadidae) from French Guiana, with an updated faunal list of French Guiana and the first synoptic list for Guyana

Zammara conflutrimacula n. sp. and Fidicinoides ininiensis n. sp. are described as new. The first records of Guyalna polypaga Sanborn, 2019 and Taphura dolabella Sanborn, 2017 are reported for French Guiana. Cicada clarisona Hancock, 1834 nomen nudum, revised status, is shown to be unavailable. The first synoptic list of cicadas for Guyana is provided. The currently known cicada fauna for French Guiana is 73 species, 20 genera, five tribes, and three subfamilies. The known fauna of Guyana is 12 species, nine genera, two tribes and one subfamily.

Phylogeny of North Americas largest cicada radiation redefines Tibicinoides and Okanagana (Hemiptera: Auchenorrhyncha: Cicadidae: Tibicininae)

Tibicinoides, with three small endemic California cicada species, has a confusing, intertwined systematic history with Okanagana that we unravel here. An ingroup including all species of Tibicinoides and the majority (84.7%) of Okanagana species were sampled for six gene regions, polarized with Clidophleps, Okanagodes, Subpsaltria, and Tibicina outgroups, and subjected to Bayesian phylogenetic analysis. Although the ingroup was monophyletic from all outgroups including Tibicina, Tibicinoides rendered Okanagana paraphyletic among two major ingroup clades. To bring classification into agreement with phylogeny, we redescribe and redefine Tibicinoides to include all Okanagana species with a hooked uncus in the male genitalia, all of which grouped with the type T. cupreosparsa (Uhler, 1889) in the first of these clades: T. boweni (Chatfield-Taylor & Cole, 2020) comb. n., T. catalina (Davis, 1936) comb. n., T. hesperia (Uhler, 1876) comb. n., T. mercedita (Davis, 1915), T. minuta (Davis, 1915), T. pallidula (Davis, 1917a) comb. n., T. pernix (Bliven, 1964) comb. n., T. rubrovenosa (Davis, 1915) comb. n., T. simulata (Davis, 1921) comb. n., T. striatipes (Haldeman, 1852) comb. n., T. uncinata (Van Duzee, 1915) comb. n., T. utahensis (Davis, 1919) comb. n., and T. vanduzeei (Distant, 1914) comb. n. Okanagana is redescribed and restricted to the species of the second major clade which contained the type O. rimosa (Say, 1830). We describe two new genera for morphologically distinct orphan lineages: Chlorocanta gen. nov. for C. viridis (Davis, 1918) comb. n. and Hewlettia gen. nov. for H. nigriviridis (Davis, 1921) comb. n. We recognize O. rubrobasalis Davis, 1926 stat. rev. as a species and relegate two former species to junior subjective synonyms: O. noveboracensis (Emmons, 1854) = O. canadensis (Provancher, 1889) and O. occidentalis (Walker in Lord, 1866) = O. lurida Davis, 1919. Tibicinoides and Okanagana together represent a rapid radiation that presents challenges to phylogenetic analysis including suboptimal outgroups and short internodes.

Resolving taxonomic issues of cicadas (Hemiptera: Cicadidae) including new combinations, new synonymies, and revised status, with updates on the diversity of the Brazilian cicada fauna and new records for four South American countries

The taxonomic position and status of historically confused cicada taxa is determined. Species are reassigned based on analysis of type specimens and the application of currently accepted higher taxonomy. Diceroprocta grossa (Fabricius, 1775) is determined to be Megatibicen grossa (Fabricius, 1775) n. comb. with Cicada auletes Germar, 1834 n. syn., Fidicina literata Walker, 1850 n. syn., and Cicada sonora Walker, 1850 n. syn. becoming junior synonyms. Abroma egae (Distant, 1892) is determined to be Brevialavenosa egae (Distant, 1892) n. comb., Abroma temperata (Walker, 1858) is reassigned to become Brevialavenosa temperata (Walker, 1858) n. comb., and Abroma apicifera (Walker, 1850) is determined to be Brevialavenosa apicifera (Walker, 1850) n. comb. Cicada sahlbergi Stål, 1854 is reassigned to become Herrera sahlbergi (Stål, 1854) n. comb. Zammara eximia Erichson, 1848 is reassigned to become Zammaralna eximia (Erichson, 1848) n. comb. Zammara strepens Amyot & Audinet-Serville, 1843 is reassigned to become Orellana strepens (Amyot & Audinet-Serville, 1843) n. comb. Orellana brunneipennis Goding, 1925 is reassigned to become Zammara brunneipennis (Goding, 1925) n. comb. and Orellana pulla Goding, 1925 is reassigned to become Zammara pulla (Goding, 1925) n. comb. Zammara brunneipennis (Goding, 1925) n. comb., n. syn., Zammara pulla (Goding, 1925) n. comb., n. syn., and Zammara erna Schmidt, 1919 n. syn. are made junior synonyms of Zammara intricata Walker, 1850. Orellana pollyae Sanborn, 2011a n. syn. is made a junior synonym of Orellana strepens (Amyot & Audinet-Serville, 1843) n. comb., and Zammara medialinea Sanborn, 2004 n. syn. is made a junior synonym of Zammara luculenta Distant, 1883. Dorisiana brasilianensis Boulard, 2017 n. syn. is determined to be a junior synonym of Dorisiana noriegai Sanborn & Heath, 2014. Two taxa, Carineta viridicollis var. a Stål, 1862 n. syn. and Cicada proponens var. b Walker, 1858c n. syn. are shown to be unavailable as well as junior synonyms of Carineta viridicollis (Germar, 1830) and Parnisa proponens (Walker, 1858c), respectively. Fidicina aldegondae Kulgatz, 1902 (in Kulgatz & Melichar, 1902) rev. stat. is removed from synonymy and reassigned to become Guyalna aldegondae (Kulgatz, 1902 in Kulgatz & Melichar, 1902) rev. stat., n. comb. Cicada costa Dohrn, 1859 is shown to be a misspelling of Cicada casta Stål, 1854 and does not represent a nomen nudum. The alpha diversity of the known Brazilian cicada fauna is now 181 species with new records of Proarna uruguayensis Berg, 1882 and Herrera dentata Sanborn, 2020 and the removal of Diceroprocta grossa (Fabricius, 1775) and Odopoea degiacomii Distant, 1912 from the fauna. New records of Hemisciera maculipennis (de Laporte, 1832) for Bolivia, Guyalna cuta (Walker, 1850) for Paraguay, and Pachypsaltria phaedima Torres, 1960 for Peru are provided.

Low hybridization temperatures improve target capture success of invertebrate loci: a case study of leaf-footed bugs (Hemiptera: Coreoidea)

Target capture is widely used in phylogenomic, ecological and functional genomic studies. Bait sets that allow capture from a diversity of species can be advantageous, but high-sequence divergence from baits can limit yields. Currently, only four experimental comparisons of a critical target capture parameter, hybridization temperature, have been published. These have been in vertebrates, where bait divergences are typically low, and none include invertebrates where bait-target divergences may be higher. Most invertebrate capture studies use a fixed, high hybridization temperature to maximize the proportion of on-target data, but many report low locus recovery. Using leaf-footed bugs (Hemiptera: Coreoidea), we investigate the effect of hybridization temperature on capture success of ultraconserved elements targeted by (i) baits developed from divergent hemipteran genomes and (ii) baits developed from less divergent coreoid transcriptomes. Lower temperatures generally resulted in more contigs and improved recovery of targets despite a lower proportion of on-target reads, lower read depth and more putative paralogues. Hybridization temperatures had less of an effect when using transcriptome-derived baits, which is probably due to lower bait-target divergences and greater bait tiling density. Thus, accommodating low hybridization temperatures during target capture can provide a cost-effective, widely applicable solution to improve invertebrate locus recovery.

A Study on Symbiotic Systems of Cicadas Provides New Insights into Distribution of Microbial Symbionts and Improves Fluorescence In Situ Hybridization Technique

Nutritional symbionts of sap-sucking auchenorrhynchan insects of Hemiptera are usually confined to the bacteriomes and/or fat bodies. Knowledge is limited about the distribution of microbial symbionts in other organs. We investigated the distribution of obligate symbionts in the salivary glands, gut tissues, reproductive organs, bacteriomes, and fat bodies of two cicada species, Karenia caelatata and Tanna sp., using integrated methods, including a modified fluorescence in situ hybridization (FISH) technique, which can greatly enhance the FISH signal intensity of related symbionts. We revealed that Candidatus Sulcia muelleri (Sulcia) and a yeast-like fungal symbiont (YLS) were harbored in the bacteriomes and fat bodies, respectively. Both of Sulcia and YLS can be transmitted to the offspring via ovaries, forming a "symbiont ball" in each egg. Neither Sulcia nor YLS were harbored in the salivary glands, gut tissues and testes. Phylogenetic trees of both Sulcia and cicadas confirm that K. caelatata is a member of the tribe Dundubiini, and the tribe Leptopsaltriini that comprises Ta. sp. is not monophyletic. YLS of K. caelatata is embedded inside the lineage of YLS of Dundubiini, whereas YLS of Ta. sp. is closely related to the clade comprising both cicada-parasitizing fungi Ophiocordyceps and YLS of Mogannia conica and Meimuna mongolica, suggesting an evolutionary replacement of YLS in Ta. sp. from an Ophiocordyceps fungus to another Ophiocordyceps fungus. Our results provide new insights into the symbiosis between Cicadidae and related symbionts. Modification through the addition of helpers and heat shock greatly enhanced the FISH signal intensity of YLS, which may provide guidelines for enhancement of the hybridization signal intensity of other symbiont(s) in the FISH experiments.

Lack of host phylogenetic structure in the gut bacterial communities of New Zealand cicadas and their interspecific hybrids

Host-microbe interactions are intimately linked to eukaryotic evolution, particularly in sap-sucking insects that often rely on obligate microbial symbionts for nutrient provisioning. Cicadas (Cicadidae: Auchenorrhyncha) specialize on xylem fluid and derive many essential amino acids and vitamins from intracellular bacteria or fungi (Hodgkinia, Sulcia, and Ophiocordyceps) that are propagated via transmission from mothers to offspring. Despite the beneficial role of these non-gut symbionts in nutrient provisioning, the role of beneficial microbiota within the gut remains unclear. Here, we investigate the relative abundance and impact of host phylogeny and ecology on gut microbial diversity in cicadas using 16S ribosomal RNA gene amplicon sequencing data from 197 wild-collected cicadas and new mitochondrial genomes across 38 New Zealand cicada species, including natural hybrids between one pair of two species. We find low abundance and a lack of phylogenetic structure and hybrid effects but a significant role of elevation in explaining variation in gut microbiota.

Detecting and removing sample contamination in phylogenomic data: an example and its implications for Cicadidae phylogeny (Insecta: Hemiptera)

Contamination of a genetic sample with DNA from one or more non-target species is a continuing concern of molecular phylogenetic studies, both Sanger sequencing studies and Next-Generation Sequencing (NGS) studies. We developed an automated pipeline for identifying and excluding likely cross-contaminated loci based on detection of bimodal distributions of patristic distances across gene trees. When the contamination occurs between samples within a dataset, comparisons between a contaminated sample and its contaminant taxon will yield bimodal distributions with one peak close to zero patristic distance. This new method does not rely on a priori knowledge of taxon relatedness nor does it determine the causes(s) of the contamination. Exclusion of putatively contaminated loci from a dataset generated for the insect family Cicadidae showed that these sequences were affecting some topological patterns and branch supports, although the effects were sometimes subtle, with some contamination-influenced relationships exhibiting strong bootstrap support. Long tip branches and outlier values for one anchored phylogenomic pipeline statistic (AvgNHomologs) were correlated with the presence of contamination. While the AHE markers used here, which target hemipteroid taxa, proved effective in resolving deep and shallow level Cicadidae relationships in aggregate, individual markers contained inadequate phylogenetic signal, in part probably due to short length. The cleaned dataset, consisting of 429 loci, from 90 genera representing 44 of 56 current Cicadidae tribes, supported three of the four sampled Cicadidae subfamilies in concatenated-matrix maximum likelihood (ML) and multispecies coalescent-based species tree analyses, with the fourth subfamily weakly supported in the ML trees. No well-supported patterns from previous family-level Sanger sequencing studies of Cicadidae phylogeny were contradicted. One taxon (Aragualna plenalinea) did not fall with its current subfamily in the genetic tree, and this genus and its tribe Aragualnini is reclassified to Tibicininae following morphological re-examination. Only subtle differences were observed in trees after removal of loci for which divergent base frequencies were detected. Greater success may be achieved by increased taxon sampling and developing a probe set targeting a more recent common ancestor and longer loci. Searches for contamination are an essential step in phylogenomic analyses of all kinds and our pipeline is an effective solution.

Complex co-evolutionary relationships between cicadas and their symbionts

Previous evidence suggests that cicadas lacking Hodgkinia may harbour the yeast-like fungal symbionts (YLS). Here, we reinforce an earlier conclusion that the pathogenic ancestor of YLS independently infected different cicada lineages instead of the common ancestor of Cicadidae. Five independent replacement events in the loss of Hodgkinia/acquisition of YLS and seven other replacement events of YLS (from an Ophiocordyceps fungus to another Ophiocordyceps fungus) are hypothesised to have occurred within the sampled cicada taxa. The divergence time of YLS lineages was later than that of corresponding cicada lineages. The rapid shift of diversification rates of YLS and related cicada-parasitizing Ophiocordyceps began at approximately 32.94 Ma, and the diversification rate reached the highest value at approximately 24.82 Ma, which corresponds to the cooling climate changes at the Eocene-Oligocene boundary and the Oligocene-Miocene transition respectively. Combined with related acquisition/replacement events of YLS occurred during the cooling-climate periods, we hypothesise that the cooling-climate changes impacted the interactions between cicadas and related Ophiocordyceps, which coupled with the unusual life cycle and the differentiation of cicadas may finally led to the diversification of YLS in Cicadidae. Our results contribute to a better understanding of the evolutionary transition of YLS from entomopathogenic fungi in insects.

Thirteen new species of Chilecicada Sanborn, 2014 (Hemiptera: Auchenorrhyncha: Cicadidae: Tibicininae) expand the highly endemic cicada fauna of Chile

The genus Chilecicada Sanborn, 2014 is shown to be a complex of closely related species rather than a monospecific genus. Chilecicada citatatemporaria Sanborn & Cole n. sp., C. culenesensis Sanborn & Cole n. sp., C. curacaviensis Sanborn & Cole n. sp., C. impartemporaria Sanborn & Cole n. sp., C. magna Sanborn & Cole n. sp., C. mapuchensis Sanborn n. sp., C. oraria Sanborn & Cole n. sp., C. parrajaraorum Sanborn n. sp., C. partemporaria Sanborn & Cole n. sp., C. pehuenchesensis Sanborn & Cole n. sp., C. trifascia Sanborn n. sp., C. trifasciunca Sanborn & Cole n. sp., and C. viridicitata Sanborn & Cole n. sp. are described as new. Chilecicada occidentis Walker, 1850 is re-described to facilitate separation of the new species from the only previously known species. Song and cytochrome oxidase I analysis available for most species support the separation of the new taxa from the type species of the genus. Known species distributions and a key to the species of the genus are also provided. The new species increases the known cicada diversity 61.9% to 34 species, 91.2% of which are endemic to Chile.

Identification of Potential Host Plants of Sap-Sucking Insects (Hemiptera: Cicadellidae) Using Anchored Hybrid By-Catch Data

Reliable host plant records are available for only a small fraction of herbivorous insect species, despite their potential agricultural importance. Most available data on insect-plant associations have been obtained through field observations of occurrences of insects on particular plants. Molecular methods have more recently been used to identify potential host plants using DNA extracted from insects, but most prior studies using these methods have focused on chewing insects that ingest tissues expected to contain large quantities of plant DNA. Screening of Illumina data obtained from sap feeders of the hemipteran family Cicadellidae (leafhoppers) using anchored hybrid enrichment indicates that, despite feeding on plant fluids, these insects often contain detectable quantities of plant DNA. Although inclusion of probes for bacterial 16S in the original anchored hybrid probe kit yielded relatively high detection rates for chloroplast 16S, the Illumina short reads also, in some cases, included DNA for various plant barcode genes as "by-catch". Detection rates were generally only slightly higher for Typhlocybinae, which feed preferentially on parenchyma cell contents, compared to other groups of leafhoppers that feed preferentially on phloem or xylem. These results indicate that next-generation sequencing provides a powerful tool to investigate the specific association between individual insect and plant species.

Phylogeography of the endemic red-tailed cicadas of New Zealand (Hemiptera: Cicadidae: Rhodopsalta), and molecular, morphological and bioacoustical confirmation of the existence of Hudson’s Rhodopsalta microdora

Why do some genera radiate, whereas others do not? The genetic structure of present-day populations can provide clues for developing hypotheses. In New Zealand, three Cicadidae genera are depauperate [Amphipsalta (three species), Notopsalta (one species) and Rhodopsalta (three species)], whereas two have speciated extensively [Kikihia (~30 species/subspecies) and Maoricicada (~20 species/subspecies). Here, we examine the evolution of Rhodopsalta, the last New Zealand genus to be studied phylogenetically and phylogeographically. We use Bayesian and maximum-likelihood analyses of mitochondrial cox1 and nuclear EF1α gene sequences. Concatenated and single-gene phylogenies for 70 specimens (58 localities) support its monophyly and three described species: Rhodopsalta cruentata, Rhodopsalta leptomera and Rhodopsalta microdora, the last taxon previously regarded as uncertain. We provide distribution maps, biological notes and the first descriptions of diagnostic songs. We show that both R. cruentata and R. microdora exhibit northern and southern genetic subclades. Subclades of the dry-adapted R. microdora clade show geographical structure, whereas those of the mesic R. cruentata and sand-dune specialist R. leptomera have few discernible patterns. Genetic, bioacoustical and detailed distributional evidence for R. microdora add to the known biodiversity of New Zealand. We designate a lectotype for Tettigonia cruentata  Fabricius, 1775, the type species of Rhodopsalta.