Biology subjects

Gloag, R.

Publications and source records attributed to Gloag, R..

10 recordsLinked to original sources

bioRxiv2026

Evidence for fungivory in Proctotydaeus furnarius, a brood mite of the Australian stingless bee Tetragonula carbonaria

Mites are common but poorly understood associates of stingless bee nests. The brood mite Proctotydaeus furnarius inhabits brood cells of Tetragonula carbonaria and was hypothesised to feed on fungi. We tested this hypothesis using electron microscopy, ITS amplicon sequencing, dye-based feeding trials, and brood-cell culturing. The unarmed, needle-like stylets of P. furnarius resembled those of fungivorous mites. In feeding trials, P. furnarius consumed a yeast isolate (Zygosaccharomyces sp.) cultured from brood cells, although also consumed crushed bee pupae. Mite presence did not detectably alter the culturable brood-cell microbial community. These findings suggest that P. furnarius feeds on fungi inside host nests but could shift its diet to feed on host brood according to resource availability.

ecology↗

bioRxiv2025

Conserved but mechanistically diverse piRNA defence against gypsy LTR retrotransposons in insect ovaries

Organisms have evolved highly adaptable defence systems to silence mobile genetic elements such as transposons. While individual transposons may emerge and vanish over time, the long-term evolutionary stability of the pathways that suppress them remains poorly understood. In the ovarian somatic cells of Drosophila, envelope-carrying gypsy long terminal repeat (LTR) retrotransposons are silenced by the Piwi-interacting RNA (piRNA) pathway, which depends exclusively on Piwi - an evolutionary derivative of an Aubergine/Piwi gene duplication unique to flies. Recent studies, however, have revealed that envelope-carrying gypsy elements are widespread across metazoans and particularly abundant in insect genomes, raising questions about the origin of ovarian somatic piRNA defence. Here we demonstrate that Aedes and Anopheles mosquitoes, as well as stingless bees and crickets, all produce piRNAs targeting gypsy elements in ovarian somatic cells, indicating a continuous arms race in this cellular niche for more than 400 million years of insect evolution. Notably, in Aedes aegypti, ovarian somatic cells express the same piRNA clusters as other somatic tissues, where they are known to target RNA viruses - suggesting a shared origin of anti-viral and anti-retrotransposon defences. Furthermore, we reveal striking lineage-specific differences in ovarian somatic piRNA biogenesis: slicing-independent phasing dominates in dipterans, ping-pong amplification in bees, and slicing-dependent phasing in crickets. Together, these findings indicate that distinct piRNA pathways have independently evolved at different timepoints to silence the same class of retrotransposons in insect evolution.

evolutionary biology↗

bioRxiv2025

Nesting behaviour drives the evolution of heat tolerance and climate vulnerability in bees

Species vulnerability to climate change depends in part on their capacity to evolve in response to increasing heat1. Within terrestrial ectotherms, heat tolerance generally corresponds weakly to current climates, which has led many to conclude that this trait is evolutionarily constrained2-4. However, most studies have not accounted for the role of microclimates, potentially obscuring signals of local adaptation. We examined heat tolerance in 95 species of wild bees that varied in nesting behaviour across the latitudinal extent of Australia. Species nest (ground, wooden cavities, or plant stems) micro-climate temperatures predicted heat tolerance evolution, where stem nesters evolved the highest heat tolerances, and ground nesters evolved the lowest heat tolerances due to their ability to evade extreme heat. A moderate level of phylogenetic inertia in heat tolerance was explained by patterns of related species sharing nesting behaviours. This indicated repeated adaptive evolution of similar heat tolerances, rather than strong evolutionary constraints on heat tolerance. Finally, incorporating nesting behaviour into assessments of climate change vulnerability changed the rank order of which species were most at risk. This underscores the need to understand what drives the evolution of heat tolerance across species to better identify the taxa most at risk to climate change.

ecology↗

bioRxiv2024

Species richness patterns in Fijian bees are explained by constraints in physiological traits

Determining the ecological and evolutionary mechanisms that underpin patterns of species richness across elevational gradients is a key question in evolutionary ecology, and can help to understand species extinction risk under changing climates. In the tropical montane islands of Fiji, there are 28 species of endemic bee in the subgenus Lasioglossum (Homalictus), where species richness increases with elevation despite decreasing land surface (habitat) areas. We used a combination of spatially explicit phylogenetic diversity analyses and phylogenetic trait analyses to examine the factors shaping species distributions in these bees. We found that species at higher elevations had lower heat tolerance and desiccation resistance than those at lower elevations, consistent with these traits constraining species elevational ranges. We also found high species phylogenetic diversity within mountains, and high phylogenetic signal in species heat tolerance and minimum elevational ranges, consistent with these traits being evolutionarily conserved among mountain-top taxa following vicariant (allopatric) speciation. We found no evidence to suggest that interspecific competition is shaping species elevational ranges. In all, our findings indicate that phylogenetic conservatism in physiological traits related to climatic niche, such as heat tolerance, can explain why species richness is highest at mountain tops in this system, with species having tracked their climatic niches over time towards ever higher (cooler and wetter) elevations. Because high elevations in this archipelago are extremely limited ([~]2.3% of total land area), only miniscule elevational islands in the sky remain into which this diverse, but climate-restricted fauna, can retreat as climates warm.

evolutionary biology↗

bioRxiv2022

Physiological traits and their relationships vary along an aridity gradient within and among Fijian bee species

O_LITemperature and water availability are hypothesised to be important abiotic drivers of the evolution of metabolic rates and gas exchange patterns, respectively. Specifically, the metabolic cold adaptation hypothesis (MCA) predicts that cold environments select for faster metabolic rates to counter the thermodynamics of biochemical reactions while the hygric hypothesis predicts that dry environments select for discontinuous gas exchange to reduce water loss. C_LIO_LIAlthough these two hypotheses consider different physiological traits and how they vary along different abiotic gradients, metabolic rate drives frequency of gas exchange patterns in insects meaning these two traits are inherently linked. Despite this link, the MCA and hygric hypotheses are rarely considered together and the extent to which metabolic rates and frequency of gas exchange vary and co-vary across climatic gradients remains unclear. C_LIO_LIWe tested the MCA and hygric hypotheses within a species of endemic Fijian bee, Homalictus fijiensis, across an altitudinal gradient of 1100 m, and among four Fijian bee species, including H. fijiensis, that inhabit different altitudinal bands. In Fiji, environmental temperature is [~]5{degrees}C lower in the central highlands than in the coastal lowlands with the highlands receiving [~]100 mm of additional precipitation than the lowlands each month. C_LIO_LIWe found an MCA-like pattern within H. fijiensis and among Fijian bee species, where metabolic rate decreased with increasing temperature, but precipitation also explained variation in metabolic rate. However, we did not find support for the hygric hypothesis within H. fijiensis or among species (frequency of gas exchange was not negatively correlated with precipitation). C_LIO_LIThe relationship between metabolic rate and frequency of gas exchange was steeper for species that occupied lower elevations on average, suggesting it is possible that these two traits can evolve independently of each other despite being positively correlated. C_LI

evolutionary biology↗

bioRxiv2022

Bee core venom genes predominantly originated before aculeate stingers evolved

Venoms, which have evolved numerous times in animals, are ideal models of convergent trait evolution. However, detailed genomic studies of toxin-encoding genes exist for only a few animal groups. The hyper-diverse hymenopteran insects are the most speciose venomous clade, but investigation of the origin of their venom genes has been largely neglected. Utilising a combination of genomic and proteo-transcriptomic data, we investigated the origin of 11 toxin genes in 29 published and three new hymenopteran genomes and compiled an up-to-date list of prevalent bee venom proteins. Observed patterns indicate that bee venom genes predominantly originate through single gene co-option with gene duplication contributing to subsequent diversification. Most Hymenoptera venom genes are shared by all members of the clade and only melittin and the new venom protein family anthophilin1 appear unique to the bee lineage. Most venom proteins thus predate the mega-radiation of hymenopterans and the evolution of the aculeate stinger.

evolutionary biology↗

bioRxiv2021

Multiple parasitism promotes facultative host acceptance of cuckoo eggs and rejection of cuckoo chicks

Many hosts of brood parasitic cuckoos reject foreign eggs from the nest. Yet where nests commonly receive more than one cuckoo egg, hosts might benefit by instead accepting parasite eggs. This is because cuckoos remove an egg from the nest before adding their own, and keeping cuckoo eggs in the nest reduces the odds that further host eggs are removed by subsequent cuckoos. This clutch dilution effect has been proposed as a precondition for the evolution of cuckoo nestling eviction by hosts, but no previous studies have tested this in a host that rejects cuckoo nestlings. We tested the clutch dilution hypothesis in large-billed gerygones (Gerygone magnirostris), which are multiply parasitized by little bronze-cuckoos (Chalcites minutillus). Gerygones evict cuckoo nestlings but accept cuckoo eggs. Consistent with multiple parasitism favouring egg acceptance, we found gerygone egg survival was higher under scenarios of cuckoo egg acceptance than rejection. Yet gerygones were also flexible in their egg acceptance, with 35% abandoning cuckoo-egg-only clutches. This novel demonstration of adaptive clutch dilution suggests that multiple parasitism can favour a facultative response to brood parasite eggs, whereby hosts accept or reject parasite eggs depending on clutch composition.

animal behavior and cognition↗

bioRxiv2021

Stingless bee floral visitation in the global tropics and subtropics

Bees play a key role in maintaining healthy terrestrial ecosystems by pollinating plants. Stingless bees (Apidae: Meliponini) are a diverse clade of social bees (>500 species) with a pantropical distribution spanning South and Central America, Africa, India, Australia and Asia. They are garnering increasing attention as commercially-beneficial pollinators of some crops, yet their contribution to the pollination of native plants in the tropics and subtropics remains poorly understood. Here we conduct a global review of the plants visited by stingless bees. We compile a database of reported associations (flower visits) between stingless bees and plants, from studies that have made either direct observations of foraging bees or analysed the pollen stored in nests. Worldwide, we find stingless bees have been reported to visit the flowers of plants from at least 220 different families and 1465 genera, with frequently reported interactions for many of the tropics most species-diverse plant families including Fabaceae, Asteraceae, Rubiaceae, Malvaceae, Lamiaceae, Arecaceae, Euphorbiaceae, Poaceae, Apocinaceae, Bignoniaceae, Melastomataceae and Myrtaceae. The list of commonly-visited plant families was similar for the stingless bee fauna of each of three major biogeographic regions (Neotropical, Afrotropical and Indo-Malayan-Australasian), though we detected differences in the proportional use of plant families by the stingless bees of the Indo-Malayan-Australasian and Neotropical regions, likely reflecting differences in the available flora of those regions. Stingless bees in all regions visit a range of exotic species in their preferred plant families (crops, ornamental plants and weeds), in addition to native plants. Although most reports of floral visitation on wild plants do not confirm effective pollen transfer, it is likely that stingless bees make at least some contribution to pollination for the majority of plants they visit. In all, our database supports the view that stingless bees play an important role in the ecosystems of the global tropics and subtropics as pollinators of an exceptionally large and diverse number of plants. This database also highlights important gaps in our knowledge of stingless bee resource use that may help focus future research efforts.

ecology↗

bioRxiv2020

Irreversible sterility of workers and high-volume egg production by queens in the stingless bee Tetragonula carbonaria

Social insect reproduction is characterised by a division of labour. Typically, the queen is the sole reproductive female in the colony and the female workers are non-reproductive. However, in the majority of social insect species the workers are only facultatively sterile and remain capable of laying eggs under some conditions, such as when the queen dies. The Australian stingless bee Tetragonula carbonaria is noteworthy as workers never lay eggs, even if a colony loses its queen. Here we describe the reproductive anatomy of T. carbonaria workers (deactivated ovaries), virgin queens (semi-activated ovaries), and mated queens (activated ovaries). T. carbonaria mated queens have high-volume egg production compared to other female insects as each of their eight ovarioles (filaments of the ovary) produces approximately 40 eggs per day. We then conduct the first experimental test of absolute worker sterility in the social insects. Using a controlled microcolony environment, we investigate whether the reproductive capacity of adult workers can be rescued by manipulating the workers social environment (separating them from a queen) and diet (feeding them unrestricted highly nutritious honey bee royal jelly), both conditions which cause ovary activation in bee species where workers are facultatively sterile. The ovaries of T. carbonaria workers that are queenless and fed royal jelly remain non-functional, indicating they are irreversibly sterile and that ovary degeneration is fixed prior to adulthood. We suggest that T. carbonaria might have evolved absolute worker sterility because colonies under natural conditions are unlikely to ever be queenless.

evolutionary biology↗

bioRxiv2020

Tests of hybridisation in Tetragonula stingless bees using multiple genetic markers.

Discrepancies in mitochondrial and nuclear genetic data are often interpreted as evidence of hybridisation. We re-examined reports of hybridisation in three cryptic stingless bee species in the genus Tetragonula in South East Queensland, Australia (T. carbonaria, T. davenporti, and T. hockingsi). Previous studies on this group using microsatellite markers proposed that occasional hybrids are found. In contrast, we find that allele frequencies at neutral regions of the nuclear genome, both microsatellites and random snps, reliably separated the three species, and thus do not support hybridisation. We found no inter-species variation in PCR amplicons of the nuclear gene EF1alpha, but low and moderate species-specific polymorphisms in the nuclear gene Opsin and the mitochondrial 16S respectively, with no cases of mito-nuclear discordance at these genes. We confirm that nuclear divergence between these species is low, based on 10-26kb of non-coding sequence flanking EF1alpha and Opsin (0.7-1% pairwise difference between species). However, we find mitogenomes to be far more diverged than nuclear genomes (21.6-23.6% pairwise difference between species). Based on these comprehensive analyses of multiple marker types, we conclude that there is no ongoing gene flow in the Tetragonula species of South East Queensland, despite their high morphological similarity to one another and the low nuclear divergence among them. The mitogenomes and draft nuclear genomes provided for these species will be a resource for further molecular studies on this group, which are important pollinators in Australian natural and agroecosystems.

evolutionary biology↗