Biology subjects

Riegler, M.

Publications and source records attributed to Riegler, M..

9 recordsLinked to original sources

bioRxiv2026

Sociality in weevils is shaped by sheltering and convergent gene losses

Eusociality, characterized by overlapping generations, cooperative brood care, and reproductive division of labour, has arisen independently across diverse, phylogenetically distant insect orders, including Hymenoptera (ants, bees, and wasps), Blattodea (termites), and Coleoptera (weevils). While multiple studies have investigated the molecular evolution of sociality from solitary ancestors in Hymenoptera and Blattodea, so far little is known about the evolutionary signatures of social evolution in Coleoptera. Weevils (Curculionidae) provide an ideal system for addressing this question, as they cover the full spectrum of social complexity from parental care, through several origins of facultative eusociality to the only obligately eusocial beetle, Austroplatypus incompertus. We generated genome assemblies for A. incompertus and two facultatively eusocial weevil species, Xylosandrus germanus and Xyleborinus saxesenii, which together with 18 publicly available weevil genomes span two independent evolutionary origins of sociality. Our analyses reveal a genome-wide relaxation of purifying selection with increasing social complexity, which is most pronounced in A. incompertus. We find a significant excess of convergent gene family contractions in lineages where sociality evolved, and no evidence of elevated positive selection. These findings indicate that the molecular mechanisms of social evolution in weevils are primarily characterised by relaxed selection and gene loss, rather than adaptive innovation and gene family expansions. These observations are consistent with sheltering and reduced effective population size playing an important role, a pattern not previously observed in other clades.

evolutionary biology↗

bioRxiv2026

Symbiont-mediated shifts in cuticular hydrocarbon profiles reduce female attractiveness after mating

Males can influence future mating interactions of females after copulation by changing female signals that subsequent males will encounter. In insects, such effects commonly involve cuticular hydrocarbons (CHCs), but whether heritable microbial symbionts contribute to post-mating chemical signalling remains largely unknown. Kelly's citrus thrips, Pezothrips kellyanus, provides an ideal system to address this question because reproductive compatibility is shaped by common arthropod endosymbionts. Across P. kellyanus populations, Cardinium occurs in almost all individuals whereas Wolbachia varies in prevalence and appears to spread by cytoplasmic incompatibility (CI). Yet, females with only Cardinium (C) avoid incompatible males carrying both Cardinium and Wolbachia (CW), and this discrimination is linked to the distinct CHC profile of CW males. Here, we tested whether this endosymbiont-associated male perfume persists on females beyond copulation by altering the female CHC profile and subsequent male mating behaviour. Using behavioural assays and GC-MS-based CHC profiling, we found that, independent of female endosymbiont association, females first mated with CW males received fewer antennal contacts and mating attempts from subsequent C males. Furthermore, mating remodelled female CHC profiles, while mating with CW males produced a distinctive post-mating chemical signature. Most notably, tridecane, previously detected only in CW males, occurred exclusively in females mated with CW males. Our findings show that endosymbionts can alter mated female CHCs and influence future sexual communication between male and female hosts. These findings reveal a previously unrecognised post-mating route through which endosymbionts reshape sexual communication, with potential consequences for reproductive compatibility and symbiont transmission dynamics.

evolutionary biology↗

bioRxiv2026

Comparative studies of transmission mode and localisation patterns of common RNA viruses in Queensland fruit fly (Bactrocera tryoni) reveal most are vertically transmitted

RNA viruses are common in tephritid fruit flies including the Queensland fruit fly, Australias most significant horticultural pest. For many their transmission, tissue tropism and load across host development remain unexplored. Yet these factors are important for host biology, ecology and pest management. We investigated Bactrocera tryoni orbivirus (OV), Bactrocera tryoni xinmovirus (XV), Bactrocera tryoni toti-like virus (TLV) and Bactrocera tryoni iflavirus species 2 (IVsp.2) that commonly coinfect B. tryoni laboratory populations. OV and XV transmission was vertical within and on eggs, while TLV transmission was vertical within eggs. IVsp.2 was not detected in eggs but was present in adults; however, IVsp.2 was horizontally transmitted, with viral load increasing with cohabitation time with infected flies. Horizontal transmission was not observed for the other viruses. OV had a similar load across all tissues, while XV was consistently more abundant in ovaries. TLV had a high viral load in the brain whereas IVsp.2 was abundant in the thorax, foregut and midgut. Besides differences in eggs, the viruses were detected in all other developmental stages, but viral load patterns differed: viral load remained constant for TLV, fluctuated for OV and XV, and was low in pre-adult stages and high in adults for IVsp.2. Our findings demonstrate distinct transmission strategies and tissue tropism among the viruses, providing new insights into their epidemiology and role in host biology. Furthermore, contrary to prevailing views that viruses are generally horizontally transmitted, most known RNA viruses of B. tryoni are vertically transmitted affecting the evolution of host-virus interactions.

microbiology↗

bioRxiv2026

Asymmetric biparental but inefficient horizontal transmission of paralysis-causing sigmavirus in Queensland fruit fly

Insects are associated with diverse RNA viruses, including vertically transmitted viruses that form persistent infections without apparent symptoms. One of the first documented vertically transmitted viruses is sigmavirus (Rhabdoviridae) affecting fitness of Drosophila. Sigmaviruses and related rhabdoviruses have also been detected in pest fruit flies and other arthropods. However, their prevalence, transmission, tissue localisation and fitness effects remain poorly known, despite their potentially common infections in diverse hosts. We investigated Sigmavirus tryoni (BtSV) prevalence, load, transmission across multiple generations and host effects in Queensland fruit fly (Bactrocera tryoni), Australias most significant horticultural pest, which carries BtSV at low prevalence (13.7%) across field populations. We detected BtSV in 6 of 12 laboratory populations (prevalence 12.5% to 80.4%) where it was transmitted biparentally within embryos. Although incomplete, maternal transmission was more reliable and resulted in higher BtSV load than paternal transmission. Paternally transmitted BtSV was almost entirely lost after two generations. BtSV became detectable in most uninfected individuals cohabiting with infected flies, but this resulted in a low load that was subsequently transmitted to only few offspring. BtSV occurred across developmental stages, digestive and reproductive tissues, albeit its viral load was lower in reproductive tissues when received paternally than maternally, and lower in testes than ovaries. Furthermore, BtSV-infected individuals suffered paralysis and mortality when exposed to high CO2 concentrations, a Rhabdoviridae effect previously reported for several Drosophila species, a muscid fly and mosquitoes. Our study suggests that sigmavirus transmission dynamics and fitness effects may apply broadly to arthropod hosts and affect their management.

evolutionary biology↗

bioRxiv2024

Social family structure and biogeography contribute to genomic divergence and cryptic speciation in the only eusocial beetle species, Austroplatypus incompertus (Curculionidae: Platypodinae)

Eusociality in insects has arisen multiple times independently in Hymenoptera (bees, wasps, ants), Blattodea (termites) and Coleoptera (beetles). In Hymenoptera and Blattodea, the evolution of eusociality led to massive species proliferation. In the hyperdiverse Coleoptera, eusociality evolved only once, in the ancient Australian ambrosia beetle species Austroplatypus incompertus (Curculionidae: Platypodinae). This species occurs in mesic eucalypt forests of eastern Australia, from Victoria to northern New South Wales. Based on few individuals collected from the southern and northern edges of the species distribution it was initially described as two distinct species; however, the names were later synonymised as no morphological differences were found in analyses of more specimens. Recent mitochondrial haplotype analyses revealed substantial latitudinal divergence across the distribution of A. incompertus. To address this apparent disparity between morphological and molecular data, we sequenced and analysed a SNP panel of over 6,656 biallelic markers from 187 individuals of 11 sites across 1000 km of this species range. Our data indicate that eusocial demographic processes such as low colony establishment success rate, limited dispersal and reliance on few reproductive individuals, together with substantial habitat fragmentation contributed to the population genetic structure of this species. We further identified that the Hunter Valley biogeographic barrier split the species into two distinct clades, with both clades in secondary close contact on the Barrington Tops plateau without any discernible admixture. Our results support the resurrection of a second species of Austroplatypus which has important consequences for the evolution eusociality in Coleoptera and the systematics of Platypodinae.

genetics↗

bioRxiv2021

Gut microbial diversity in stingless bees is linked to host wing size and is influenced by geography

Stingless bees are globally important social corbiculate bees, fulfilling critical pollination roles in many ecosystems; however, their gut microbiota, especially fungal communities, are not well characterized to date. We collected 121 bee samples from two species, Tetragonula carbonaria and Austroplebeia australis, across a distance of 1,200 km of eastern Australia, and analysed their gut microbiomes. We found that the gut bacterial richness of T. carbonaria was influenced by geography (latitude and longitude) and positively correlated to an established fitness indicator in insects; namely, host forewing length/size that relates to flight capacity of stingless bees. We characterized the core microbiomes of the two bees and found that they consisted of the bacterial taxa Snodgrassella, Lactobacillus, Acetobacteraceae and Bombella, and the fungal taxa Didymellaceae, Monocilium mucidum, Malassezia restricta and Aureobasidium pullulans. Both host species identity and management (wild or managed) significantly influenced the gut microbial diversity and composition, and similarity between colonies declined as the geographical distance between them increased. This result was also supported by our co-existing network analyses. Overall, we have thoroughly analysed stingless bee gut microbiomes, and provided novel evidence that T. carbonaria bees with larger wings or from more southern populations have higher microbial diversity in their guts. Originality-Significance StatementBeneficial interactions between insects and their microbial symbionts are pivotal for their fitness. In this study, we analysed the gut microbiomes of two stingless bee species, Tetragonula carbonaria and Austroplebeia australis, that are widespread and important pollinators in Australia. We characterized their gut microbiomes and detected a significant positive correlation between gut bacterial richness and host forewing size for T. carbonaria; the first time that gut microbial diversity has been linked to a morphological trait in stingless bees. Furthermore, we found that host species identity, management type (wild or managed) and geography all significantly influenced bee gut microbial diversity and composition, and were able to describe both bacterial and fungal core microbial taxa. This study reveals novel understandings of stingless bee gut microbiomes and provides the basis for utilizing microbial strategies to maintain colony health.

ecology↗

bioRxiv2020

Applying machine learning in motor activity time series of depressed bipolar and unipolar patients.

Current practice of assessing mood episodes in affective disorders largely depends on subjective observations combined with semi-structured clinical rating scales. Motor activity is an objective observation of the inner physiological state expressed in behavior patterns. Alterations of motor activity are essential features of bipolar and unipolar depression. The aim was to investigate if objective measures of motor activity can aid existing diagnostic practice, by applying machine-learning techniques to analyze activity patterns in depressed patients and healthy controls. Random Forrest, Deep Neural Network and Convolutional Neural Network algorithms were used to analyze 14 days of actigraph recorded motor activity from 23 depressed patients and 32 healthy controls. Statistical features analyzed in the dataset were mean activity, standard deviation of mean activity and proportion of zero activity. Various techniques to handle data imbalance were applied, and to ensure generalizability and avoid overfitting a Leave-One-User-Out validation strategy was utilized. All outcomes reports as measures of accuracy for binary tests. A Deep Neural Network combined with random oversampling class balancing technique performed a cut above the rest with a true positive rate of 0.82 (sensitivity) and a true negative rate of 0.84 (specificity). Accuracy was 0.84 and the Matthews Correlation Coefficient 0.65. Misclassifications appear related to data overlapping among the classes, so an appropriate future approach will be to compare mood states intra-individualistic. In summary, machine-learning techniques present promising abilities in discriminating between depressed patients and healthy controls in motor activity time series.

bioinformatics↗

bioRxiv2019

The fate of carbon in a mature forest under carbon dioxide enrichment

Atmospheric carbon dioxide enrichment (eCO2) can enhance plant carbon uptake and growth1,2,3,4,5, thereby providing an important negative feedback to climate change by slowing the rate of increase of the atmospheric CO2 concentration6. While evidence gathered from young aggrading forests has generally indicated a strong CO2 fertilization effect on biomass growth3,4,5, it is unclear whether mature forests respond to eCO2 in a similar way. In mature trees and forest stands7,8,9,10, photosynthetic uptake has been found to increase under eCO2 without any apparent accompanying growth response, leaving an open question about the fate of additional carbon fixed under eCO24, 5, 7,8,9,10,11. Here, using data from the first ecosystem-scale Free-Air CO2 Enrichment (FACE) experiment in a mature forest, we constructed a comprehensive ecosystem carbon budget to track the fate of carbon as the forest responds to four years of eCO2 exposure. We show that, although the eCO2 treatment of ambient +150 ppm (+38%) induced a 12% (+247 gCm-2yr-1) increase in carbon uptake through gross primary production, this additional carbon uptake did not lead to increased carbon sequestration at the ecosystem level. Instead, the majority of the extra carbon was emitted back into the atmosphere via several respiratory fluxes, with increased soil respiration alone contributing [~]50% of the total uptake surplus. Our results call into question the predominant thinking that the capacity of forests to act as carbon sinks will be generally enhanced under eCO2, and challenge the efficacy of climate mitigation strategies that rely on CO2 fertilization as a driver of increased carbon sinks in standing forests and afforestation projects.

ecology↗

bioRxiv2017

Master manipulation continued: feminizing Wolbachia endosymbiont distorts sex chromosome inheritance

Genomes are vulnerable to selfish genetic elements that enhance their own transmission often at the expense of host fitness. Examples are cytoplasmic elements such as maternally inherited bacteria that cause feminization, male-killing, parthenogenesis and cytoplasmic incompatibility. We demonstrate, for the first time, that segregation distortion, a phenomenon so far seen only for nuclear genetic elements, can also be caused by a cytoplasmic element, the ubiquitous endosymbiotic bacterium Wolbachia. For Eurema mandarina butterfly lineages with a Z0 sex chromosome constitution, we provide direct and conclusive evidence that Wolbachia induces production of all-female progeny by a dual role: the compensation for the female-determining function that is absent in Z0 lineages (feminization) and the prevention of maternal sex chromosome inheritance to offspring as a specific type of segregation distortion. Therefore, our findings highlight that both sex determination and chromosome inheritance -- crucially important developmental processes of higher eukaryotes -- can be manipulated by cytoplasmic parasites.

evolutionary biology↗