Biology subjects

Bybee, S. M.

Publications and source records attributed to Bybee, S. M..

5 recordsLinked to original sources

bioRxiv2024

Antennal sensilla diversity in diurnal and nocturnal fireflies (Coleoptera, Lampyridae)

Insects use their antennae to collect environmental information. While the structural diversity of insect antennae is immediately obvious, the diversity of the minute antennal sensilla that interact with the environmental stimuli and translate them into sensory input, is largely unknown for many insect groups. This includes the beetle family Lampyridae, which includes nocturnal species that use bioluminescent signals during mate search, and diurnal species that rely exclusively on pheromones to identify and locate a potential mate. Diurnal species tend to have relatively larger antennae, and diurnal males have larger antennae than their females. It is generally assumed that antennal size reflects sensilla numbers, but this remains to be tested. Here we use Scanning Electron Microscopy to document the sensilla diversity of both males and females of three diurnal and four nocturnal firefly species, as well as total sensilla numbers, densities and their distribution along the antenna. We identified 14 sensilla morphotypes across the seven species, including 12 morphotypes that are new for Lampyridae. Mechanosensilla (3 morphotypes) were the most abundant and conserved sensilla across firefly species, and the distribution of chemosensilla (9 morphotypes) was unexpectedly variable across species. We hypothesized that the differences in mating signals between diurnal and nocturnal fireflies would be reflected in their chemosensilla counts or densities. As predicted, diurnal and nocturnal fireflies did not differ in their mechanoreceptor counts or densities, nor did males and females. In contrast, firefly males had significantly more chemoreceptors (and higher densities) than females and the interaction term (activity by sex) was also significant: diurnal males had significantly more chemoreceptors than nocturnal males, highlighting the importance of pheromones for diurnal species. Based on a series of predictions, we also identified a pheromone sensilla candidate for each species that will facilitate functional testing in future studies.

evolutionary biology↗

bioRxiv2023

The developmental gene disco regulates diel-niche evolution in adult moths

AbstractAnimals shift activity periods to reduce predation, minimize competition, or exploit new resources, and this can drive sensory system evolution. But adaptive mechanisms underlying niche- shifts are poorly understood, and model organisms are often too distantly related to reveal the genetic drivers. To address this, we examined expression patterns between two closely related silk moths that have undergone temporal niche divergence. We found 200-700 differentially expressed genes, including day upregulation in eye development and visual processing genes, and night upregulation of antennal and olfactory brain development genes. Further, clusters of circadian, sensory, and brain development genes co-expressed with diel-activity. In both species, eight genes showed expression significantly correlated to diel activity, and are involved in vision, olfaction, brain development, neural plasticity, energy utilization, and cellular maintenance. We repeatedly recovered disco, a zinc- finger transcription factor involved in antennal development, circadian activity, and optic lobe brain development in flies. While disco mutants have circadian arrhythmia, most studies attribute this to improper clock neuron development, not adult circadian maintenance. Comparing predicted 3D protein structure across moth and fly genetic models revealed disco likely retained developmental function with a conserved zinc finger domain, but gained functional zinc finger domains absent in D. melanogaster. These regions have several mutations between nocturnal and diurnal species that co- occur with higher levels of predicted phosphorylation sites. With robust circadian expression, functional nocturnal and diurnal mutations, and structural and sequence conservation, we hypothesize that disco may be a master regulator contributing to diel-activity diversification in adult moths. SignificanceInsect diel-activity patterns are diverse, yet the underlying evolutionary processes are poorly understood. Light environment powerfully entrains circadian rhythms and drives diel-niche and sensory evolution. To investigate its impact, we compared gene expression in closely related day- and night-active wild silk moths, with otherwise similar ecologies. Expression patterns that varied with diel activity included genes linked to eye development, neural plasticity and cellular maintenance. Notably, disco, which encodes a zinc-finger transcription factor involved in pupal Drosophila optic lobe and antennal development, shows robust adult circadian mRNA cycling in moth heads, is highly conserved in moths, and has additional zinc-finger domains with specific nocturnal and diurnal mutations. We hypothesize that disco may contribute to diversification of adult diel-activity patterns in moths.

evolutionary biology↗

bioRxiv2021

Firefly bioluminescence outshines aerial predators

Bioluminescence is found across the tree of life and has many functions. Yet we understand very little about its timing and origins, particularly as a predator avoidance strategy. Understanding the timing between bioluminescence and predator origins has yet to be examined and can help elucidate the evolution of this ecologically important aposematic signal. Using the most prevalent bioluminescent group, fireflies, where bioluminescence primarily functions as aposematic and sexual signals, the timing for the origins of both potential predators of fireflies and bioluminescence is explored. Divergence time estimations were performed using genomic-scale phylogenetic reconstructions, and multiple fossil calibration points, allowing for a robust estimate for the origin of lampyrid bioluminescence as a terrestrial and as an aerial signal. Our results recover the origins of terrestrial beetle bioluminescence at 141.17 (122.63-161.17) mya and firefly aerial bioluminescence at 133.18 (117.86-152.47) mya with a large dataset focused on Lampyridae; and terrestrial bioluminescence as 148.03 (130.12-166.80) mya, with the age of aerial bioluminescence at 104.97 (99.00-120.90) mya with a complementary broad Elateroidea dataset. These ages predate the origins of all known extant aerial predators (i.e., bats and birds) and support the much older terrestrial predators (assassin bugs, frogs, ground beetles, lizards, snakes, hunting spiders, and harvestmen) as the most likely drivers of terrestrial bioluminescence in beetles, and sexual signaling likely being the original function in aerial fireflies.

evolutionary biology↗

bioRxiv2020

Deep ancestral introgression shapes evolutionary history of dragonflies and damselflies

Introgression is arguably one of the most important biological processes in the evolution of groups of related species, affecting at least 10% of the extant species in the animal kingdom. Introgression reduces genetic divergence between species, and in some cases can be highly beneficial, facilitating rapid adaptation to ever-changing environmental pressures. Introgression also significantly impacts inference of phylogenetic species relationships where a strictly binary tree model cannot adequately explain reticulate net-like species relationships. Here we use phylogenomic approaches to understand patterns of introgression along the evolutionary history of a unique, non-model insect system: dragonflies and damselflies (Odonata). We demonstrate that introgression is a pervasive evolutionary force across various taxonomic levels within Odonata. In particular, we show that the morphologically "intermediate" species of Anisozygoptera (one of the three primary suborders within Odonata besides Zygoptera and Anisoptera), which retain phenotypic characteristics of the other two suborders, experienced high levels of introgression likely coming from zygopteran genomes. Additionally, we found evidence for multiple cases of deep inter-superfamilial ancestral introgression.

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↗