Biology subjects

Hotaling, S.

Publications and source records attributed to Hotaling, S..

At least 19 recordsLinked to original sources

bioRxiv2026

Elevation shapes alpine snow algal blooms and their influence on albedo reduction

Snow algae darken snowpacks and accelerate melt worldwide. Although elevation strongly structures the physical conditions of mountain snowfields, its influence on snow algal traits and their effects on snowpack reflectance remains unclear. Here, we investigated snow algal composition, cellular traits, and optical properties in summer blooms across an elevational range of 1,059-3,423 m a.s.l. in the western United States, spanning two elevational gradients in the Cascade Range (CA, OR, WA) and the Rocky Mountains (UT, WY, MT). Across all samples (n = 294), snow albedo declined strongly with increasing algal cell density, indicating that total biomass, rather than pigment composition, is the dominant driver of albedo reduction. However, within Sanguina-dominated blooms (117 of 206 samples bloom samples identified across the dataset), neither relative abundance nor algal cell density varied systematically with elevation. Instead, mean cell size increased with elevation, while per-cell pigment concentrations declined, leading to higher astaxanthin:chlorophyll-a ratios driven primarily by reductions in chlorophyll-a per cell. These elevation-dependent shifts in cell size and pigment balance were consistent across both mountain ranges, indicating phenotypic acclimation to increasing environmental stress with elevation. Together, these findings link cellular-scale acclimation of a widespread snow alga to radiative processes shaping mountain snowpacks.

microbiology↗

bioRxiv2024

Temperature and Pressure Shaped the Evolution of Antifreeze Proteins in Polar and Deep Sea Zoarcoid Fishes

Antifreeze proteins (AFPs) have enabled teleost fishes to repeatedly colonize polar seas. Four AFP types have convergently evolved in several fish lineages. AFPs inhibit ice crystal growth and lower cellular freezing point. In lineages with AFPs, species inhabiting colder environments may possess more AFP copies. Elucidating how differences in AFP copy number evolve is challenging due to the genes tandem array structure and consequently poor resolution of these repetitive regions. Here we explore the evolution of type III AFPs (AFP III) in the globally distributed suborder Zoarcoidei, leveraging six new long-read genome assemblies. Zoarcoidei has fewer genomic resources relative to other polar fish clades while it is one of the few groups of fishes adapted to both the Arctic and Southern Oceans. Combining these new assemblies with additional long-read genomes available for Zoarcoidei, we conducted a comprehensive phylogenetic test of AFP III evolution and modeled the effects of thermal habitat and depth on AFP III gene family evolution. We confirm a single origin of AFP III via neofunctionalization of the enzyme sialic acid synthase B and show that AFP copies expanded under low temperature, but also decreased with depth, which reduces freezing point via pressure. Associations between the environment and AFP III copy number were driven by duplications of paralogs that were translocated out of the ancestral locus at which Zoarcoidei AFP arose. Our results reveal novel environmental effects on AFP evolution and demonstrate the value of high-quality genomic resources for studying how structural genomic variation shapes convergent adaptation.

evolutionary biology↗

bioRxiv2024

Laboratory experiments suggests limited impact of increased nitrogen deposition on snow algae blooms

Snow algal blooms decrease snow albedo and increase local melt rates. However, the causes behind the size and frequency of these blooms are still not well understood. One factor that is likely contributing is nutrient availability, specifically nitrogen (N) and phosphorus (P). However, the nutrient requirements of the taxa responsible for these blooms is not known. Here, we assessed the growth of three commercial strains of snow algae under 24 different nutrient treatments that varied in both absolute and relative concentrations of N and P. After 38 days of incubation, we measured total biomass and cell size and estimated their effective albedo reduction surface (EARS). Snow algal strains tended to respond similarly and achieved bloom-like cell densities over a wide range of NP conditions. However, the molar ratio of N:P at which maximum biomass was achieved was between 4 and 7. Our data indicate a high requirement for P for snow algae and suggest that additional N inputs into the ecosystem may not significantly impact the productivity and abundance of snow algae blooms. This highlights P availability as a critical factor influencing the frequency and extent of snow algae blooms and their potential contribution to snow melt through altered albedo.

microbiology↗

bioRxiv2023

Phylogenomics recovers multiple origins of portable case-making in caddisflies (Insecta: Trichoptera), the world's most common underwater architects

Caddisflies (Trichoptera) are among the most diverse groups of freshwater animals with more than 16,000 described species. They play an outsized role in freshwater ecology and environmental engineering in streams, rivers, and lakes. Because of this, they are frequently used as indicator organisms in biomonitoring programs. Despite their importance, key questions concerning the evolutionary history of caddisflies, such as the timing and origin of larval case-making, have been unanswered due to the lack of a well-resolved phylogenetic tree. To shed light on these questions in Trichoptera, we estimated a phylogenetic tree using a combination of transcriptomes and targeted enrichment data for 206 species, representing 48 of 52 extant families and 174 genera. We calibrated and dated the tree with a set of 33 carefully selected fossils. The first caddisflies originated in the Permian and the major suborders began to diversify in the Triassic. Ancestral state reconstruction and diversification analysis revealed that portable case-making evolved in three separate lineages and shifts in diversification occurred in concert with key evolutionary innovations other than case-making.

evolutionary biology↗

bioRxiv2023

Trophic flexibility and hydrology structure alpine stream food webs: Implications for a fading cryosphere

Understanding biotic interactions and how they vary across habitats is important for assessing the vulnerability of communities to climate change. Receding glaciers in high mountain areas can lead to the hydrologic homogenization of streams and reduce habitat heterogeneity, which are predicted to drive declines in regional diversity and imperil endemic species. However, little is known about food web structure in alpine stream habitats, particularly among streams fed by different hydrologic sources (e.g., glaciers or snowfields). We used gut content and stable isotope analyses to characterize food web structure of alpine macroinvertebrate communities in streams fed by glaciers, subterranean ice, and seasonal snowpack in the Teton Range, Wyoming, USA. Specifically, we sought to: (1) assess community resource use among streams fed by different hydrologic sources; (2) explore how variability in resource use relates to feeding strategies; and (3) identify which environmental variables influenced resource use within communities. Average taxa diet differed among all hydrologic sources, and food webs in subterranean ice-fed streams were largely supported by the gold alga Hydrurus. This finding bolsters a hypothesis that streams fed by subterranean ice may provide key habitat for cold-water species under climate change by maintaining a longer growing season for this high-quality food resource. While a range of environmental variables associated with hydrologic source (e.g., stream temperature) were related to diet composition, hydrologic source categories explained the most variation in diet composition models. Less variable diets within versus among streams suggests high trophic flexibility, which was further supported by high levels of omnivory. This inherent trophic flexibility may bolster alpine stream communities against future changes in resource availability as the mountain cryosphere fades. Ultimately, our results expand understanding of the habitat requirements for imperiled alpine taxa while empowering predictions of their vulnerability under climate change.

ecology↗

bioRxiv2022

Uncovering hidden genetic diversity: allelic resolution of insect and spider silk genes

Arthropod silk is vital to the evolutionary success of hundreds of thousands of species. The primary proteins in silks are often encoded by long, repetitive gene sequences. Until recently, sequencing and assembling these complex gene sequences has proven intractable given their repetitive structure. Here, using high-quality long-read sequencing, we show that there is extensive variation--both in terms of length and repeat motif order--between alleles of silk genes within individual arthropods. Further, this variation exists across two deep, independent origins of silk which diverged more than 500 million years ago--(1) the insect clade containing caddisflies and butterflies and (2) spiders. This remarkable convergence in previously overlooked patterns of allelic variation across multiple origins of silk suggests mechanisms for the generation and maintenance of structural protein-coding genes. Future genomic efforts to connect genotypes to phenotypes should account for such allelic variation.

genomics↗

bioRxiv2022

Warming undermines emergence success in a threatened alpine stonefly: a multi-trait perspective on vulnerability to climate change

Species vulnerability to global warming is often assessed using short-term metrics such as the critical thermal maximum (CTmax), which represents an organisms ability to survive extreme heat. However, an understanding of the long-term effects of sub-lethal warming is an essential link to fitness in the wild, and these effects are not adequately captured by metrics like CTmax. The meltwater stonefly, Lednia tumana, is endemic to high-elevation streams of Glacier National Park, MT, USA, and has long been considered acutely vulnerable to climate change-associated stream warming. In 2019, it was listed as Threatened under the U.S. Endangered Species Act. This presumed vulnerability to warming was challenged by a recent study showing that nymphs can withstand short-term exposure to temperatures as high as ~27 {degrees}C. But how this short-term tolerance relates to chronic, long-term warming has remained unclear. By measuring fitness-related traits at several ecologically relevant temperatures over several weeks, we show that L. tumana cannot complete its life-cycle at temperatures well below the CTmax values measured for its nymphs. Although warmer temperatures maximized growth rates, they appear to have a detrimental impact on other key traits (survival, emergence success, and wing development), thus extending our understanding of L. tumanas vulnerability to climate change. Our results call into question the use of CTmax as a measure of thermal sensitivity, while highlighting the power and complexity of multi-trait approaches to assessing climate vulnerability.

ecology↗

bioRxiv2022

Realizing the promise of biodiversity genomics with highly accurate long reads

BackgroundGenerating the most contiguous, accurate genome assemblies given available sequencing technologies is a long-standing challenge in genome science. With the rise of long-read sequencing, assembly challenges have shifted from merely increasing contiguity to correctly assembling complex, repetitive regions of interest, ideally in a phased manner. At present, researchers largely choose between two types of long read data: longer, but less accurate sequences, or highly accurate, but shorter reads (i.e., >Q20 or 99% accurate). To better understand how these types of long-read data as well as scale of data (i.e., mean length and sequencing depth) influence genome assembly outcomes, we compared genome assemblies for a caddisfly, Hesperophylax magnus, generated with longer, but less accurate, Oxford Nanopore (ONT) R9.4.1 and highly accurate PacBio HiFi (HiFi) data. Next, we expanded this comparison to consider the influence of highly accurate long-read sequence data on genome assemblies across 6,750 plant and animal genomes. For this broader comparison, we used HiFi data as a surrogate for highly accurate long-reads broadly as we could identify when they were used from GenBank metadata. ResultsHiFi reads outperformed ONT reads in all assembly metrics tested for the caddisfly data set and allowed for accurate assembly of the repetitive [~]20 Kb H-fibroin gene. Across plants and animals, genome assemblies that incorporated HiFi reads were also more contiguous. For plants, the average HiFi assembly was 501% more contiguous (mean contig N50 = 20.5 Mb) than those generated with any other long-read data (mean contig N50 = 4.1 Mb). For animals, HiFi assemblies were 226% more contiguous (mean contig N50 = 20.9 Mb) versus other long-read assemblies (mean contig N50 = 9.3 Mb). In plants, we also found limited evidence that HiFi may offer a unique solution for overcoming genomic complexity that scales with assembly size. ConclusionsHighly accurate long-reads generated with HiFi or analogous technologies represent a key tool for maximizing genome assembly quality for a wide swath of plants and animals. This finding is particularly important when resources only allow for one type of sequencing data to be generated. Ultimately, to realize the promise of biodiversity genomics, we call for greater uptake of highly accurate long-reads in future studies.

genomics↗

bioRxiv2022

Community science for enigmatic ecosystems: Using eBird to assess avian biodiversity on glaciers and snowfields

AimTo quantify avian biodiversity and habitat preference and describe behavior in an enigmatic, understudied ecosystem: mountain glaciers and snowfields. LocationMountains in the Pacific Northwest of western North America: British Columbia (CA), Washington and Oregon (USA). TaxonBirds observed within our study area and focal habitat. MethodsWe used community science data from eBird--an online database of bird observations from around the world--to estimate bird biodiversity and abundance in glacier and snowfield ecosystems as well as nearby, ice-adjacent habitats. We used field notes from eBird users and breeding codes to extend our data set to include insight into habitat usage and behavior. Finally, we compared our community-science approach to previous studies that used traditional survey methods. ResultsWe identified considerable avian biodiversity in glacier and snowfield habitat (46 species) with four specialists that appeared to prefer glaciers and snowfields over nearby, ice-adjacent habitat. Combined with field notes by eBird users, our efforts increased the known global total of avian species associated with ice and snow habitats by 14%. When community science data was compared to traditional methods, we found similar species diversity but differences in abundance. Main conclusionsDespite the imminent threat of glacier and snowfield melt due to climate change, species living in these habitats remain poorly studied, likely due to the remoteness and ruggedness of their terrain. Glaciers and snowfields hold notable bird diversity, however, with a specialized set of species appearing to preferentially forage in these habitats. Our results show that community science data can provide a valuable starting point for studying difficult to access areas, but traditional surveys are still useful for more rigorous quantification of avian biodiversity.

ecology↗

bioRxiv2022

Summer dynamics of microbial diversity on a mountain glacier

Under climate change, glaciers are rapidly receding worldwide. A melting cryosphere will dramatically alter global sea levels, carbon cycling, and water resource availability. Glaciers also host rich biotic communities that are dominated by microbial diversity and this biodiversity can impact surface albedo, thereby driving a feedback loop between biodiversity and cryosphere melt. However, the microbial diversity of glacier ecosystems remains largely unknown outside of major ice sheets, particularly from a temporal perspective. Here, we characterized temporal dynamics of bacteria, eukaryotes, and algae on the Paradise Glacier, Mount Rainier, USA, over the summer melt season. During our study, the glacier surface steadily darkened as seasonal snow melted and darkening agents accumulated until new snow fell in late September. From a community-wide perspective, the bacterial community remained generally constant and eukaryotes exhibited a clear temporal progression of community change while fungal diversity was intermediate. Individual taxonomic groups, however, exhibited considerable stochasticity. We found little support for our a priori prediction that autotroph abundance would peak before heterotrophs. Notably, two different trends in snow algae emerged--an abundant early-and late-season OTU with a different mid-summer OTU that peaked in August. Overall, our results highlight the need for temporal sampling to clarify microbial diversity on glaciers and that caution should be exercised when interpreting results from single or few timepoints.

microbiology↗

bioRxiv2022

Long-read HiFi Sequencing Correctly Assembles Repetitive heavy fibroin Silk Genes in New Moth and Caddisfly Genomes

Insect silk is an incredibly versatile biomaterial. Lepidoptera and their sister lineage, Trichoptera, display some of the most diverse uses of silk with varying strength, adhesive qualities and elastic properties. It is well known that silk fibroin genes are long (> 20 kb) and have many repetitive motifs. These features make these genes challenging to sequence. Most research thus far has focused on conserved N- and C-terminal regions of fibroin genes because a full comparison of repetitive regions across taxa has not been possible. Using the PacBio Sequel II system and SMRT sequencing, we generated high fidelity (HiFi) long-read genomic and transcriptomic sequences for the Indianmeal moth (Plodia interpunctella) and genomic sequences for the caddisfly, Eubasilissa regina. Both genomes were highly contiguous (N50 = 9.7 Mbp/32.4 Mbp, L50 = 13/11) and complete (BUSCO Complete = 99.3%/95.2%), with complete and contiguous recovery of silk heavy fibroin gene sequences. This study demonstrates that HiFi long-read sequencing can significantly help our understanding of genes with highly contiguous, repetitive regions.

genomics↗

bioRxiv2022

Repetitive elements in the era of biodiversity genomics: insights from 600+ insect genomes

Repetitive elements (REs) are integral to the composition, structure, and function of eukaryotic genomes, yet remain understudied in most taxonomic groups. We investigated REs across 601 insect species and report wide variation in REs dynamics across groups. Analysis of associations between REs and protein-coding genes revealed dynamic evolution at the interface between REs and coding regions across insects, including notably elevated RE-gene associations in lineages with abundant long interspersed nuclear elements (LINEs). We leveraged this large, empirical data set to quantify impacts of long-read technology on RE detection and investigate fundamental challenges to RE annotation in diverse groups. In long-read assemblies we detected [~]36% more REs than short-read assemblies, with long terminal repeats (LTRs) showing 162% increased detection, while DNA transposons and LINEs showed less respective technology-related bias. In most insect lineages, 25-85% of repetitive sequences were "unclassified" following automated annotation, compared to only [~]13% in Drosophila species. Although the diversity of available insect genomes has rapidly expanded, we show the rate of community contributions to RE databases has not kept pace, preventing efficient annotation and high-resolution study of REs in most groups. We highlight the tremendous opportunity and need for the biodiversity genomics field to embrace REs and suggest collective steps for making progress towards this goal.

genomics↗

bioRxiv2021

Human and wildlife use of mountain glacier habitat in western North America

ContextThe global recession of glaciers and perennial snowfields is reshaping mountain ecosystems. Beyond physical changes to the landscape and altered downstream hydrology, the implications of glacier decline for biodiversity are poorly known. Before predictions can be made about how climate change will affect wildlife in glacier-associated ecosystems, a more thorough accounting of the role that glaciers play in species life histories is needed. However, typical approaches for documenting wildlife presence and behavior--remote camera traps--are difficult to use in glaciated terrain due to limited options for securing them (e.g., no trees) and dramatic seasonal changes in snowpack. AimsIn this study, we sought to test a novel camera trap designed for glaciated mountain ecosystems. We also aimed to use this approach to gain insight into wildlife and human usage of a mountain glacier in western North America. MethodsWe deployed an elevational transect of uniquely designed camera traps along the western margin of the Paradise Glacier, a rapidly receding mountain glacier on the south side of Mount Rainier, WA, USA. Our simple camera trap design consisted of a wildlife camera attached to a camouflaged cylindrical cooler filled with snow and rocks. Key resultsOur camera design proved ideal for a mountain glacier ecosystem and from June to September 2021, we detected at least 16 vertebrate species (seven birds, nine mammals) over 770 trap nights using glacier-associated habitats. Humans, primarily skiers, were the most common species detected, but we also recorded 99 observations of wildlife (birds and mammals). These included three species of conservation concern in Washington: wolverine (Gulo gulo), Cascade red fox (Vulpes vulpes cascadensis), and white-tailed ptarmigan (Lagopus leucura). ConclusionsCollectively, our results provide proof-of-concept for a novel camera trap design that is ideal for treeless, perennially snow-covered landscapes and revealed a rich diversity of wildlife using mountain glacier habitat in the Pacific Northwest. We highlight the global need for similar studies to better understand the true scale of biodiversity that will be impacted by glacier recession in mountain ecosystems.

ecology↗

bioRxiv2021

Pathways to polar adaptation in fishes revealed by long-read sequencing

Long-read sequencing is driving a new reality for genome science where highly contiguous assemblies can be produced efficiently with modest resources. Genome assemblies from long-read sequences are particularly exciting for understanding the evolution of complex genomic regions that are often difficult to assemble. In this study, we leveraged long-read sequencing data to generate a high-quality genome assembly for an Antarctic eelpout, Opthalmolycus amberensis, the first for the globally distributed family Zoarcidae. We used this assembly to understand how O. amberensis has adapted to the harsh Southern Ocean and compared it to another group of Antarctic fishes: the notothenioids. We showed that selection has largely acted on different targets in eelpouts relative to notothenioids. However, we did find some overlap; in both groups, genes involved in membrane structure, thermal tolerance, and vision have evidence of selection. We found evidence for historical shifts of transposable element activity in O. amberensis and other polar fishes, perhaps reflecting a response to environmental change. We were specifically interested in the evolution of two complex genomic loci known to underlie key adaptations to polar seas: hemoglobin and antifreeze proteins (AFPs). We observed unique evolution of the hemoglobin MN cluster in eelpouts and related fishes in the suborder Zoarcoidei relative to other Perciformes. For AFPs, we identified the first species in the suborder with no evidence of afpIII sequences (Cebidichthys violaceus) in the genomic region where they are found in all other Zoarcoidei, potentially reflecting a lineage-specific loss of this cluster. Beyond polar fishes, our results highlight the power of long-read sequencing to understand genome evolution.

genomics↗

bioRxiv2021

Towards a genome sequence for every animal: where are we now?

In less than 25 years, the field of animal genome science has transformed from a discipline seeking its first glimpses into genome sequences across the Tree of Life to a global enterprise with ambitions to sequence genomes for all of Earths eukaryotic diversity (1). As the field rapidly moves forward, it is important to take stock of the progress that has been made to best inform the disciplines future. In this Perspective, we provide a contemporary, quantitative overview of animal genome sequencing. We identified the best available genome assemblies on GenBank, the worlds most extensive genetic database, for 3,278 unique animal species across 24 phyla. We assessed taxonomic representation, assembly quality, and annotation status for major clades. We show that while tremendous taxonomic progress has occurred, stark disparities in genomic representation exist, highlighted by a systemic overrepresentation of vertebrates and underrepresentation of arthropods. In terms of assembly quality, long-read sequencing has dramatically improved contiguity, whereas gene annotations are available for just 34.3% of taxa. Furthermore, we show that animal genome science has diversified in recent years with an ever-expanding pool of researchers participating. However, the field still appears to be dominated by institutions in the Global North, which have been listed as the submitting institution for 77% of all assemblies. We conclude by offering recommendations for how we can collectively improve genomic resource availability and value while also broadening global representation. Significance statementThe field of animal genome science is rapidly developing, and efforts are underway to sequence genomes for all of Earths eukaryotic biodiversity. Here, we provide an overview of animal genome sequencing, with emphases on taxonomic representation, assembly quality, and geographic representation. We show that while a staggering 3,278 unique animal species have had their genomes sequenced, massive disparities exist in terms of the taxonomic groups receiving attention, the quality of the resources being produced, and the institutions driving the field. We highlight areas where improvements can be made, notably by continuing to increase the quality of genome assemblies, including by improving metadata and voucher specimen associations, and actively developing meaningful collaborations between researchers form the Global North and South.

genomics↗

bioRxiv2021

Lessons from 20 years of plant genome sequencing: an unprecedented resource in need of more diverse representation

The field of plant genomics has grown rapidly in the past 20 years, leading to dramatic increases in both the quantity and quality of publicly available genomic resources. With this ever-expanding wealth of genomic data from an increasingly diverse set of taxa, unprecedented potential exists to better understand the genome biology and evolution of plants. Here, we provide a contemporary view of plant genomics, including analyses on the quality of existing plant genome assemblies, the taxonomic distribution of sequenced species, and how national participation has influenced the fields development. We show that genome quality has increased dramatically in recent years, that substantial taxonomic gaps exist, and that the field has been dominated by affluent nations in the Global North and China, despite a wide geographic distribution of sequenced species. We identify multiple disconnects between the native range of focal species and the national affiliation of the researchers studying the plants, which we argue are rooted in colonialism--both past and present. However, falling sequencing costs paired with widening availability of analytical tools and an increasingly connected scientific community provide key opportunities to improve existing assemblies, fill sampling gaps, and, most importantly, empower a more global plant genomics community.

plant biology↗

bioRxiv2021

Long-reads are revolutionizing 20 years of insect genome sequencing

The first insect genome (Drosophila melanogaster) was published two decades ago. Today, nuclear genome assemblies are available for a staggering 601 insect species representing 20 orders. In this study, we analyzed the most-contiguous assembly for each species and provide a "state of the field" perspective, emphasizing taxonomic representation, assembly quality, gene completeness, and sequencing technologies. Relative to species richness, genomic efforts have been biased towards four orders (Diptera, Hymenoptera, Collembola, and Phasmatodea), Coleoptera are underrepresented, and 11 orders still lack a publicly available genome assembly. The average insect genome assembly is 439.2 megabases in length with 87.5% of single-copy benchmarking genes intact. Most notable has been the impact of long-read sequencing; assemblies that incorporate long-reads are ~48x more contiguous than those that do not. We offer four recommendations as we collectively continue building insect genome resources: (1) seek better integration between independent research groups and consortia, (2) balance future sampling between filling taxonomic gaps and generating data for targeted questions, (3) take advantage of long read sequencing technologies, and (4) expand and improve gene annotations. Significance statementSince the first insect genome was sequenced ~20 years ago, sequencing technologies and the availability of insect genome assemblies have both advanced dramatically. In this study, we curated, analyzed, and summarized the field of insect genomics in terms of taxonomic representation, assembly quality, gene completeness, and sequencing technology. We show that 601 insect species have genome assemblies available, with some groups heavily overrepresented (e.g., Diptera) relative to others (e.g., Coleoptera). The major takeaway of our study is that genome assemblies produced with long reads are ~48x more contiguous than short read assemblies.

genomics↗

bioRxiv2021

The biogeographic history of eelpouts and related fishes: linking phylogeny, environmental change, and patterns of dispersal in a globally distributed fish group

Modern genetic data sets present unprecedented opportunities to understand the evolutionary origins of taxonomic groups comprising hundreds to thousands of species. When the timing of key events are known, it is also possible to investigate biogeographic history in the context of major phenomena (e.g., continental drift). In this study, we investigated the biogeographic history of the suborder Zoarcoidei, a globally distributed fish group that includes species inhabiting both poles and multiple taxa that produce antifreeze proteins to survive chronic subfreezing temperatures. We first generated a multi-locus, time-calibrated phylogeny for the group. We then used biogeographic modeling to reconstruct ancestral ranges across the tree and quantify the type and frequency of biogeographic events (e.g., founder, dispersal). With these results, we considered how the cooling of the Southern and Arctic Oceans, which reached their present-day subfreezing temperatures 10-15 million years ago (Mya) and 2-3 Mya, respectively, may have shaped the evolutionary history of Zoarcoidei, with an emphasis on the most speciose and widely distributed family, eelpouts (family Zoarcidae). Our phylogenetic results clarified standing issues in the Zoarcoidei taxonomy and showed that the group began to diversify in the Oligocene [~]31-32 Mya, with the center of origin for all families in north temperate waters. Within-area speciation was the most common biogeographic event in the groups history (80% of all events) followed by dispersal (20%). Finally, we found mixed evidence for polar ocean cooling underpinning Zoarcoidei diversification, with support limited to eelpout speciation in the Southern Ocean over the last 10 million years.

evolutionary biology↗