Biology subjects

Tolman, E.

Publications and source records attributed to Tolman, E..

5 recordsLinked to original sources

bioRxiv2026

Contrasting Range and Demographic Histories in two Palearctic Dragonfly Species (Odonata: Anisoptera)

Climatic suitability is often used to infer historical range changes, yet whether suitable area predicts effective population size remains unexplored. We investigated this relationship in two Palearctic dragonflies with contrasting ecologies: Somatochlora arctica, a widespread peatland specialist, and S. meridionalis, a southern European species associated with shaded streams. We combined demographic reconstructions from individual reference genomes using the pairwise sequentially Markovian coalescent (PSMC), maximum entropy (MaxEnt) species distribution models projected across six paleoclimatic intervals spanning approximately 3.3 million years, and ancestral state reconstructions of peatland specialization. Predicted suitable area was consistently greater for S. arctica, reaching its greatest extent during the Last Glacial Maximum. However, its inferred effective population size was smaller than that of S. meridionalis for most of the last ~275,000 years. Ancestral reconstructions placed the most probable gain of peatland specialization in the S. arctica lineage (Clade I) during the late Miocene, with a median age of 9.4 million years, predating the modeled climatic intervals. These findings indicate a decoupling of climatic suitability and demographic history. Patchy breeding habitat, population structure, and the isolated Scottish origin of the sampled S. arctica may contribute to this mismatch. Combining genomic, ecological, and phylogenetic approaches provides complementary insights into historical biogeography and highlights the limitations of interpreting suitable climate as available breeding habitat or using individual genomes to characterize species-wide demographic histories.

genomics↗

bioRxiv2026

Testing Thirty Years of Hypotheses: Ancient Trout-Salmon Introgression and Limited Pre-Colonial Gene Flow Between Rainbow and Cutthroat Trout Shaped Pacific Salmonid Evolution

Introgression is the transfer of genetic material between species or populations through hybridization and backcrossing. While often deleterious or neutral in nature, introgression can also have beneficial consequences for the recipient lineage. Oncorhynchus is a genus of ray-finned fish (family Salmonidae) composed of nine species of Pacific trout and eight species of Pacific salmon, in which deep introgression has long been proposed to explain patterns of gene-tree-species-tree discordance, and in which hybridization is extensively observed between introduced and endemic species. In this study, we identified well-supported introgression between the ancestral lineage of Pacific trout and the ancestor of Chinook and coho salmon, a long-posited but previously untested hypothesis. While other salmon lineages (pink, chum, sockeye, and masu salmon) have been sympatric with trout for extended periods, providing an opportunity for hybridization to occur, we found no evidence of introgression between trout and these other salmon lineages. Our findings suggest mito-nuclear incompatibilities serve as a possible barrier to gene flow between the clade comprised of pink, chum, and sockeye salmon and all other lineages in Oncorhynchus. Within Pacific trout, we detected no historical introgression between cutthroat and rainbow trout lineages, suggesting that the extensive hybridization observed between them today reflects recent, primarily human-mediated contact rather than long-term gene flow. These findings show that ancestral introgression has shaped the evolutionary history of Oncorhynchus and should be accounted for in future comparative phylogenetic studies of the genus.

evolutionary biology↗

bioRxiv2026

One species, two lives: cryptic population structure and life-history divergence in a vineyard spittlebug (Aphrophora sp.), a candidate vector for Pierce's disease

Whole genome analysis of spittlebug populations, an Aphrophora species (Hemiptera: Aphrophoridae) known to spread Pierce's disease, from various vineyards in Napa and Sonoma Counties demonstrates that these insects are conspecific with Aphrophora permutata found in quasi-natural populations. The genomes analyzed fall in three autosomal clusters with two sympatric populations (based on admixture) that diverged around 40,000-90,000 years before present according to demographic models. We also recover three related but distinct mitochondrial clusters. There is no genetic differentiation between Napa and Sonoma County vineyard populations and very modest differentiation among vineyards and quasi-natural Berkeley/Oakland Hills population. These vineyard and quasi-natural populations have distinct life histories, including divergent oviposition hosts (understory herbs versus pines) and different patterns of adult seasonal migration (out-migration and return versus simple movement from the understory to the pine canopy). Analysis of the mitochondrial gene COI indicates that A. permutata, Aphrophora fulva and Aphrophora maculosa are intermingled in the same mitochondrial clade, along with the more distantly related species Aphrophora gelida. Further, all three autosomal genetic clusters show evidence of selection for insecticide resistance. We also find that endosymbionts Wolbachia and Rickettsia were both present in a substantial fraction of specimens analyzed, but neither appears to influence population structure. Overall, our findings elucidate an intriguing degree of life history divergence between geographically proximate, conspecific populations linked by gene flow and may have implications for the continued management of vineyard populations.

ecology↗

bioRxiv2025

First Genomic Insights into an Aeshnidae Dragonfly: Unveiling the Genome of a Holarctic Species, Aeshna juncea

Temperature oscillations in the Arctic may present a unique opportunity to study how insect species respond to such changes. Aeshna juncea, a Holarctic species of the family Aeshnidae thrives in this environment; molecular adaptations that allow it to survive in the Arctic have yet to be evaluated. Here, we present the first assembled and annotated draft genome assembly and annotation of A. juncea. The assembly is both highly contiguous and complete. This resource is presented and used here to provide further evidence that transposons and unclassified repetitive elements are a major driver behind genome size variation in Odonata and show that the effective population size of A. juncea populations from Alaska went through bottlenecks during the most recent ice age. We believe this genome will be an important resource in understanding how species like Aeshna juncea survive in Arctic habitats.

evolutionary biology↗

bioRxiv2022

A Chromosome-length Assembly of the Black Petaltail (Tanypteryx hageni) Dragonfly

We present a chromosome-length genome assembly and annotation of the Black Petaltail dragonfly (Tanypteryx hageni). This habitat specialist diverged from its sister species over 70 million years ago, and separated from the most closely related Odonata with a reference genome 150 million years ago. Using PacBio HiFi reads and Hi-C data for scaffolding we produce one of the most high quality Odonata genomes to date. A scaffold N50 of 206.6 Mb and a BUSCO score of 96.8% indicate high contiguity and completeness. SignificanceWe provide a chromosome-length assembly of the Black Petaltail dragonfly (Tanypteryx hageni), the first genome assembly for any non-libelluloid dragonfly. The Black Petaltail diverged from its sister species over 70 million years ago. T. hageni, like its confamilials, occupies fen habitats in its nymphal stage, a life history uncommon in the vast majority of dragonflies. We hope that the availability of this assembly will facilitate research on T. hageni and other petaltail species, to better understand their ecology and support conservation efforts.

genomics↗