Biology subjects

Lower, S. E.

Publications and source records attributed to Lower, S. E..

6 recordsLinked to original sources

bioRxiv2025

Species-specific bacterial associations emerge from stochastically assembled microbiomes in Northeastern American fireflies

Many insects harbor diverse microbial communities ("microbiomes") that can profoundly influence the biology of their host. Yet, for most insect taxa, the relative roles of stochastic events versus deterministic forces in shaping these communities remain unknown. We investigated microbiome assembly in fireflies (Coleoptera: Lampyridae) using 16S rRNA gene amplicon sequencing and quantitative PCR from 12 species and species groups collected across the Northeastern United States. We hypothesized that firefly microbiomes are predominantly structured by stochastic ecological processes, such as random microbial exposures. Consistent with this, we observed elevated normalized stochasticity ratio (NST) values for most bacteria, coupled with high intraspecific variability in bacterial abundance and composition. However, microbiomes were more similar among closely related firefly hosts, and several bacterial taxa, including endosymbionts and unusually prevalent mollicute strains, showed lower NST values, species-specific associations, and patterns linked to geography, season, and sex. These results reveal that deterministic processes--likely involving host-driven microbial filtering, microbe-microbe interactions, and reliable transmission modes--act alongside stochastic forces to shape firefly-microbe associations. By disentangling these ecological drivers in a diverse, understudied beetle lineage, our study advances understanding of the ecological and evolutionary processes structuring microbiomes in the wild.

ecology↗

bioRxiv2025

Antennal RNAseq reveals odorant receptors with sex-biased expression in the common eastern firefly, Photinus pyralis

BackgroundWith their charismatic nighttime flashes, fireflies are a classic organismal system for studying visual mating signal evolution. However, across their diversity, fireflies employ a variety of mating strategies that include both chemical and visual signals. While phylogenetic evidence points to a common ancestor that relied on long-range pheromones, behavioral evidence suggests that light-dependent flashing fireflies do not use smell for mating. We tested this hypothesis by investigating the olfactory genetics of the nocturnal, light-using common eastern firefly, Photinus pyralis. In insects, odors are primarily detected by odorant receptor (OR) proteins embedded in the dendritic membranes of olfactory receptor neurons. If pheromones are part of mate signaling in light-using fireflies, then one or more OR genes should be upregulated in the antennae of the searching sex (males). We therefore annotated the complete suite of ORs from the genome of P. pyralis and measured expression of OR genes between the sexes. ResultsWe identified 102 ORs in the Photinus pyralis genome, including the conserved single-copy Orco. Our phylogenetic analysis showed lineage-specific OR diversification in P. pyralis relative to other beetle species. Differential expression analysis of male and female antennae and hind legs revealed that a subset of ORs are upregulated in antennae as compared to legs, suggesting a role in adult olfaction. Notably, PpyrOR6 was one of two genes, and the only OR, that was significantly upregulated between male and female antennae, suggesting a role in mating. ConclusionsThese findings increase known diversity of insect ORs in an understudied beetle family and suggest that bioluminescent fireflies use multimodal signals during mating.

evolutionary biology↗

bioRxiv2022

Identification of a Female-produced Sex Attractant Pheromone of the Winter Firefly, Photinus corrusca

Firefly flashes are well-known visual signals used by these insects to find, identify, and choose mates. However, many firefly species have lost the ability to produce light as adults. These "unlighted" species generally lack developed adult light organs, are diurnal rather than nocturnal, and are believed to use volatile pheromones acting over a distance to locate mates. While cuticular hydrocarbons, which may function in mate recognition at close range, have been examined for a handful of the over 2000 extant firefly species, no volatile pheromone has ever been identified. In this study, using coupled gas chromatography - electroantennographic detection, we detected a single female-emitted compound that elicited antennal responses from wild-caught male winter fireflies, Photinus corrusca. The compound was identified as (1S)-exo-3-hydroxycamphor (hydroxycamphor). In field trials at two sites across the species eastern North American range, large numbers of male P. corrusca were attracted to synthesized hydroxycamphor, verifying its function as a volatile sex attractant pheromone. Males spent more time in contact with lures treated with synthesized hydroxycamphor than those treated with solvent only in laboratory two-choice assays. Further, using single sensillum recordings, we characterized a pheromone-sensitive odorant receptor neuron in a specific olfactory sensillum on male P. corrusca antennae and demonstrated its sensitivity to hydroxycamphor. Thus, this study has identified the first volatile pheromone and its corresponding sensory neuron for any firefly species, and provides a tool for monitoring P. corrusca populations for conservation, and further inquiry into the chemical and cellular bases for sexual communication among fireflies.

ecology↗

bioRxiv2021

A Time-calibrated Firefly (Coleoptera: Lampyridae) Phylogeny: Using Genomic Data for Divergence Time Estimation

Fireflies (Coleoptera: Lampyridae) consist of over 2,000 described extant species. A well-resolved phylogeny of fireflies is important for the study of their population genetics, bioluminescence, evolution, and conservation. We used a recently published anchored hybrid enrichment dataset (AHE; 436 loci for 88 Lampyridae species and 10 outgroup species) and state-of-the-art statistical methods (the fossilized birth-death-range process implemented in a Bayesian framework) to estimate a time-calibrated phylogeny of Lampyridae. Unfortunately, estimating calibrated phylogenies using AHE and the latest and most robust time-calibration strategies is not possible because of computational constraints. As a solution, we subset the full dataset by applying three different strategies: (i) using the most complete loci, (ii) using the most homogeneous loci, and (iii) using the loci with the highest accuracy to infer the well established Photinus clade. The estimated topology using the three data subsets agreed on almost all major clades and only showed minor discordance within less supported nodes. The estimated divergence times overlapped for all nodes that are shared between the topologies. Thus, divergence time estimation is robust as long as the topology inference is robust and any well selected data subset suffices. Additionally, we observed an un-expected amount of gene tree discordance between the 436 AHE loci. Our assessment of model adequacy showed that standard phylogenetic substitution models are not adequate for any of the 436 AHE loci which is likely to bias phylogenetic inferences. We performed a simulation study to explore the impact of (a) incomplete lineage sorting, (b) uniformly distributed and systematic missing data, and (c) systematic bias in the position of highly variable and conserved sites. For our simulated data, we observed less gene tree variation which shows that the empirically observed amount of gene tree discordance for the AHE dataset is unexpected and needs further investigation.

evolutionary biology↗

bioRxiv2019

On the inference of a southern origin of the North American firefly Photinus pyralis

The firefly Photinus pyralis inhabits a wide range of latitudinal and ecological niches, with populations living from temperate to tropical habitats. Its ample geographic distribution makes this species an ideal system for the study of local adaptation and demographic inference of wild populations. Therefore, in this study we modelled and inferred different demographic scenarios for North American populations of P. pyralis, collected from Texas to New Jersey. To do this, we used a combination of ABC techniques (for multi-population/colonization analyses), and likelihood inference (dadi) for single-population demographic inference, which proved useful with our RAD data.We uncovered that the most ancestral North American population lays in Texas, which further colonized the Central region of the US and more recently the North Eastern coast. Our study confidently rejects a demographic scenario where the North Eastern populations colonized more southern populations until reaching Texas. Our results suggest that P. pyralis originated in Central- or South America, followed by migration events that populated northern latitudes. Finally, modelling the demographic history of North American P. pyralis serves as a null model of nucleotide diversity patterns, which will inform future studies of adaptation, not only in P. pyralis, but also in other North American taxa.

evolutionary biology↗

bioRxiv2017

Firefly genomes illuminate the origin and evolution of bioluminescence

Fireflies are among the best-studied of the bioluminescent organisms. Despite longterm interest in the biochemistry, neurobiology, and evolution of firefly flash signals and the widespread biotechnological applications of firefly luciferase, only a limited set of genes related to this complex trait have been described. To investigate the genetic basis of firefly bioluminescence, we generated a high-quality reference genome for the Big Dipper firefly Photinus pyralis, from which the first laboratory luciferase was cloned, using long-read (PacBio), short-read (Illumina), and Hi-C sequencing technologies. To facilitate comparative genomics, we also generated short-read genome assemblies for a Japanese firefly Aquatica lateralis and a bioluminescent click beetle, Ignelater luminosus. Analyses of these genomic datasets supports at least two independent gains of luminescence in beetles, and provides new insights into the evolution of beetle bioluminescence and chemical defenses that likely co-evolved over their 100 million years of evolution.

genomics↗