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Chytridiomycosis is caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd) and is regarded as one of the most significant threats to global amphibian populations. In México, Bd was first reported in 2003 and has now been documented in 13 states. We visited 33 localities and swabbed 199 wild-caught anurans from 7 species (5 native, 2 exotic) across the Mediterranean region of the state of Baja California. Using quantitative PCR, Bd was detected in 94 individuals (47.2% of samples) at 25 of the 33 survey localities for 5 native and 1 exotic frog species. The exotic Xenopus laevis was the only species that tested completely negative for Bd. We found that remoteness, distance to agricultural land, and elevation were the best positive predictors of Bd presence. These are the first Bd-positive results for the state of Baja California, and its presence should be regarded as an additional conservation threat to the region’s native frog species.

Established invasive species represent one of the most harmful and challenging threats to native biodiversity, necessitating methods for Early Detection and Rapid Response. Cryptic invasions are particularly challenging and often require expensive and time-consuming molecular surveys which limits their usefulness for management. We present a novel application of the Fluidigm SNP-Type Assay to identify rare non-native alleles that significantly reduces the cost and time to generate diagnostic results. We demonstrate the efficacy of this method using experimental Fluidigm pools (99% accuracy) and sequence data (96% accuracy). We apply our novel methodology to an endangered population of California tiger salamanders in Sonoma County where two individual non-native tiger salamander hybrids have previously been detected since 2008. We screened 5805 larvae in 387 sample-pools containing 15 larvae each. We did not detect any non-native hybrids in the population, a result that was verified with sequence data, though we strongly recommend additional years of sampling to confirm hybrid absence. Our success with a challenging, large-genome amphibian suggests this method may be applied to any system, and would be particularly useful when it is necessary for conservation practitioners to rapidly identify rare taxa or genes of interest., (© 2024. The Author(s).)

The federally endangered sister species, Eucyclogobius newberryi (northern tidewater goby) and E. kristinae (southern tidewater goby) comprise the California endemic genus Eucyclogobius, which historically occurred in all coastal California counties. Isolated lagoons that only intermittently connect to the sea are their primary habitat. Reproduction occurs during lagoon closure, minimizing marine dispersal and generating the most genetically subdivided vertebrate genus on the California coast. We present a new genome assembly for E. newberryi using HiFi long reads and Hi-C chromatin-proximity sequencing. The 980Mb E. newberryi reference genome has an N50 of 34Mb with 22 well-described scaffolds comprising 88% of the genome and a complete BUSCO score of 96.7%. This genome will facilitate studies addressing selection, drift, and metapopulation genetics in subdivided populations, as well as the persistence of the critically endangered E. kristinae, where reintroduction will be an essential element of conservation actions for recovery. It also provides tools critical to the recovery of the genetically distinct management units in the northern tidewater goby, as well as broader ecological and evolutionary studies of gobies, the most speciose family of fishes in the world., (© The American Genetic Association. 2024.)

We describe a highly contiguous and complete diploid genome assembly for the Chryxus Arctic, Oeneis chryxus (E. Doubleday, [1849]), a butterfly species complex spanning much of northern and western North America. One subspecies, the Ivallda Arctic (O. c. ivallda), is endemic to California's Sierra Nevada and of particular biogeographic interest and conservation concern. Extreme alpine habitats occupied by this subspecies include the summit of Mt. Whitney, California, representing the highest elevation butterfly population in North America. The assembly presented here consists of two haplotypes, 738.92 and 770.85 Mb in length, with contig N50 values of 10.49 and 10.13 Mb, scaffold N50 values of 25.35 and 25.69 Mb, scaffold L50 values of 13 and 14, and BUSCO completeness scores of 96.5 and 98.3%, respectively. More than 97% of the assembly is organized into 29 scaffolds, which likely represent whole chromosomes. This assembly is the first major genomic resource for Oeneis, providing a foundational reference for future genomic studies on the taxonomy, evolutionary history, and conservation of the genus. As part of the California Conservation Genomics Project, we will use this assembly in conjunction with short-read resequencing to resolve patterns of evolutionary differentiation, adaptive genomic variation, and gene flow among remaining O. c. ivallda populations. These data can and will be used to inform the subspecies' conservation as warming climatic conditions continue to lead to the loss and fragmentation of alpine habitats. We also provide genome assemblies for the O. chryxus mitochondrion and a Wolbachia endosymbiont., (© The American Genetic Association. 2024.)

Polyergus kidnapper ants are widely distributed, but relatively uncommon, throughout the Holarctic, spanning an elevational range from sea level to over 3000 m. These species are well known for their obligate social parasitism with various Formica ant species, which they kidnap in dramatic, highly coordinated raids. Kidnapped Formica larvae and pupae become integrated into the Polyergus colony where they develop into adults and perform nearly all of the necessary colony tasks for the benefit of their captors. In California, Polyergus mexicanus is the most widely distributed Polyergus, but recent evidence has identified substantial genetic polymorphism within this species, including genetically divergent lineages associated with the use of different Formica host species. Given its unique behavior and genetic diversity, Polyergus mexicanus plays a critical role in maintaining ecosystem balance by influencing the population dynamics and genetic diversity of its host ant species, Formica, highlighting its conservation value and importance in the context of biodiversity preservation. Here, we present a high-quality genome assembly of P. mexicanus from a sample collected in Plumas County, CA, USA, in the foothills of the central Sierra Nevada. This genome assembly consists of 364 scaffolds spanning 252.31 Mb, with contig N50 of 481,250 kb, scaffold N50 of 10.36 Mb, and BUSCO completeness of 95.4%. We also assembled the genome of the Wolbachia endosymbiont of P. mexicanus - a single, circular contig spanning 1.23 Mb. These genome sequences provide essential resources for future studies of conservation genetics, population genetics, speciation, and behavioral ecology in this charismatic social insect., (© The American Genetic Association. 2024.)

The California Pipevine, Aristolochia californica Torr., is the only endemic California species within the cosmopolitan birthwort family Aristolochiaceae. It occurs as an understory vine in riparian and chaparral areas and in forest edges and windrows. The geographic range of this plant species almost entirely overlaps with that of its major specialized herbivore, the California Pipevine Swallowtail Butterfly Battus philenor hirsuta. While this species pair is a useful, ecologically well-understood system to study co-evolution, until recently, genomic resources for both have been lacking. Here, we report a new, chromosome-level assembly of A. californica as part of the California Conservation Genomics Project (CCGP). Following the sequencing and assembly strategy of the CCGP, we used Pacific Biosciences HiFi long reads and Hi-C chromatin proximity sequencing technology to produce a de novo assembled genome. Our genome assembly, the first for any species in the genus, contains 531 scaffolds spanning 661 megabase (Mb) pairs, with a contig N50 of 6.53 Mb, a scaffold N50 of 42.2 Mb, and BUSCO complete score of 98%. In combination with the recently published B. philenor hirsuta reference genome assembly, the A. californica reference genome assembly will be a powerful tool for studying co-evolution in a rapidly changing California landscape., (© The American Genetic Association. 2024.)

When invasive and endangered native taxa hybridize, the resulting admixture introduces novel conservation challenges. Across a large region of central California, a hybrid swarm consisting of admixed endangered California tiger salamanders (CTS) (Ambystoma californiense) and introduced barred tiger salamanders (BTS) (Ambystoma mavortium) has replaced native populations, threatening the genetic integrity of CTS and the vernal pool systems they inhabit. We employed a large-scale, genomically informed field experiment to test whether shortening breeding pond hydroperiod would favor native CTS genotypes. We constructed 14 large, seminatural ponds to evaluate the effect of hydroperiod duration on larval survival and mass at metamorphosis. We tracked changes in non-native allele frequencies with a 5237-gene exon capture array and employed a combination of custom Bayesian and generalized linear models to quantify the effect of pond duration on salamander fitness. Earlier work on this system showed hybrid superiority under many conditions and suggested that hybrids are favored in human-modified ponds with artificially long hydroperiods. Consistent with these earlier studies, we found overwhelming evidence for hybrid superiority. Very short hydroperiods substantially reduced the mass (1.1-1.5 fold) and survival probability (10-13 fold) of both native and hybrid larvae, confirming that hydroperiod likely exerts a strong selective pressure in the wild. We identified 86 genes, representing 1.8% of 4723 screened loci, that significantly responded to this hydroperiod-driven selection. In contrast to earlier work, under our more natural experimental conditions, native CTS survival and size at metamorphosis were always less than hybrids, suggesting that hydroperiod management alone will not shift selection to favor native larval genotypes. However, shortening pond hydroperiod may limit productivity of hybrid ponds, complementing other strategies to remove hybrids while maintaining vernal pool ecosystems. This study confirms and expands on previous work that highlights the importance of hydroperiod management to control invasive aquatic species., (© 2023 The Authors. Conservation Biology published by Wiley Periodicals LLC on behalf of Society for Conservation Biology.)

Carpenter ants in the genus Camponotus are large, conspicuous ants that are abundant and ecologically influential in many terrestrial ecosystems. The bicolored carpenter ant, Camponotus vicinus Mayr, is distributed across a wide range of elevations and latitudes in western North America, where it is a prominent scavenger and predator. Here, we present a high-quality genome assembly of C. vicinus from a sample collected in Sonoma County, California, near the type locality of the species. This genome assembly consists of 38 scaffolds spanning 302.74 Mb, with contig N50 of 15.9 Mb, scaffold N50 of 19.9 Mb, and BUSCO completeness of 99.2%. This genome sequence will be a valuable resource for exploring the evolutionary ecology of C. vicinus and carpenter ants generally. It also provides an important tool for clarifying cryptic diversity within the C. vicinus species complex, a genetically diverse set of populations, some of which are quite localized and of conservation interest., (© The American Genetic Association. 2023.)

The Yuma myotis bat (Myotis yumanensis) is a small vespertilionid bat and one of 52 species of new world Myotis bats in the subgenus Pizonyx. While M. yumanensis populations currently appear relatively stable, it is one of 12 bat species known or suspected to be susceptible to white-nose syndrome, the fungal disease causing declines in bat populations across North America. Only two of these 12 species have genome resources available, which limits the ability of resource managers to use genomic techniques to track the responses of bat populations to white-nose syndrome generally. Here we present the first de novo genome assembly for Yuma myotis, generated as a part of the California Conservation Genomics Project. The M. yumanensis genome was generated using a combination of PacBio HiFi long reads and Omni-C chromatin-proximity sequencing technology. This high-quality genome is one of the most complete bat assemblies available, with a contig N50 of 28.03 Mb, scaffold N50 of 99.14 Mb, and BUSCO completeness score of 93.7%. The Yuma myotis genome provides a high-quality resource that will aid in comparative genomic and evolutionary studies, as well as inform conservation management related to white-nose syndrome., (© The American Genetic Association. 2023.)

Rattlesnakes play important roles in their ecosystems by regulating prey populations, are involved in complex coevolutionary dynamics with their prey, and exhibit a variety of unusual adaptations, including maternal care, heat-sensing pit organs, hinged fangs, and medically-significant venoms. The western rattlesnake (Crotalus oreganus) is one of the widest ranging rattlesnake species, with a distribution from British Columbia, where it is listed as threatened, to Baja California and east across the Great Basin to western Wyoming, Colorado and New Mexico. Here, we report a new reference genome assembly for one of six currently recognized subspecies, C. oreganus helleri, as part of the California Conservation Genomics Project (CCGP). Consistent with the reference genomic sequencing strategy of the CCGP, we used Pacific Biosciences HiFi long reads and Hi-C chromatin-proximity sequencing technology to produce a de novo assembled genome. The assembly comprises a total of 698 scaffolds spanning 1,564,812,557 base pairs, has a contig N50 of 64.7 Mb, a scaffold N50 of 110.8 Mb, and BUSCO complete score of 90.5%. This reference genome will be valuable for studies on the genomic basis of venom evolution and variation within Crotalus, in resolving the taxonomy of C. oreganus and its relatives, and for the conservation and management of rattlesnakes in general., (© The American Genetic Association. 2023.)

Snakes in the family Colubridae include more than 2,000 currently recognized species, and comprise roughly 75% of the global snake species diversity on Earth. For such a spectacular radiation, colubrid snakes remain poorly understood ecologically and genetically. Two subfamilies, Colubrinae (788 species) and Dipsadinae (833 species), comprise the bulk of colubrid species richness. Dipsadines are a speciose and diverse group of snakes that largely inhabit Central and South America, with a handful of small-body-size genera that have invaded North America. Among them, the ring-necked snake, Diadophis punctatus, has an incredibly broad distribution with 14 subspecies. Given its continental distribution and high degree of variation in coloration, diet, feeding ecology, and behavior, the ring-necked snake is an excellent species for the study of genetic diversity and trait evolution. Within California, six subspecies form a continuously distributed "ring species" around the Central Valley, while a seventh, the regal ring-necked snake, Diadophis punctatus regalis is a disjunct outlier and Species of Special Concern in the state. Here, we report a new reference genome assembly for the San Diego ring-necked snake, D. p. similis, as part of the California Conservation Genomics Project. This assembly comprises a total of 444 scaffolds spanning 1,783 Mb and has a contig N50 of 8.0 Mb, scaffold N50 of 83 Mb, and BUSCO completeness score of 94.5%. This reference genome will be a valuable resource for studies of the taxonomy, conservation, and evolution of the ring-necked snake across its broad, continental distribution., (© The American Genetic Association. 2023.)

Spiny lizards (genus Sceloporus) have long served as important systems for studies of behavior, thermal physiology, dietary ecology, vector biology, speciation, and biogeography. The western fence lizard, Sceloporus occidentalis, is found across most of the major biogeographical regions in the western United States and northern Baja California, Mexico, inhabiting a wide range of habitats, from grassland to chaparral to open woodlands. As small ectotherms, Sceloporus lizards are particularly vulnerable to climate change, and S. occidentalis has also become an important system for studying the impacts of land use change and urbanization on small vertebrates. Here, we report a new reference genome assembly for S. occidentalis, as part of the California Conservation Genomics Project (CCGP). Consistent with the reference genomics strategy of the CCGP, we used Pacific Biosciences HiFi long reads and Hi-C chromatin-proximity sequencing technology to produce a de novo assembled genome. The assembly comprises a total of 608 scaffolds spanning 2,856 Mb, has a contig N50 of 18.9 Mb, a scaffold N50 of 98.4 Mb, and BUSCO completeness score of 98.1% based on the tetrapod gene set. This reference genome will be valuable for understanding ecological and evolutionary dynamics in S. occidentalis, the species status of the California endemic island fence lizard (S. becki), and the spectacular radiation of Sceloporus lizards., (© The American Genetic Association. 2023.)

Wide-ranging species are seldom considered conservation priorities, yet they have the potential to harbour genetically deeply differentiated units across environments or ecological barriers, including some that warrant taxonomic recognition. Documenting such cryptic genetic diversity is especially important for wide-ranging species that are in decline, as they may comprise a set of even more endangered lineages or species with small distributions. However, studies of wide-ranging species, particularly when they cross political borders, are extremely challenging. One approach to overcoming these challenges is to conduct detailed local analyses in combination with less detailed, range-wide studies. We used this approach with the red-footed tortoise (Chelonoidis carbonarius), a threatened species likely to contain cryptic diversity given its vast range and the distinctive ecoregions that it inhabits. Previous single-gene molecular studies indicated the presence of at least five lineages, two of which occur in different ecoregions separated by the Andes within Colombia. We used a comprehensive genomic analysis to test the hypothesis of cryptic diversity within the single jurisdiction of Colombia. We used a combination of restriction-site-associated DNA sequencing and environmental niche modelling to provide three independent lines of evidence that support the presence of important cryptic diversity that may deserve taxonomic recognition: allopatric reproductive isolation, local adaptation and ecological divergence. We also provide a fine-scale genetic map with the distribution of conservation units in Colombia. As we complete ongoing range-wide analyses and make taxonomic adjustments, we recommend that the two lineages in Colombia be treated as separate units for conservation purposes., (© 2023 The Authors. Molecular Ecology published by John Wiley & Sons Ltd.)

Speciation entails a reduction in gene flow between lineages. The rates at which genomic regions become isolated varies across space and time. Barrier markers are linked to putative genes involved in (processes of) reproductive isolation, and, when observed over two transects, indicate species-wide processes. In contrast, transect-specific putative barrier markers suggest local processes. We studied two widely separated transects along the 900 km hybrid zone between Bufo bufo and B. spinosus, in northern and southern France, for ~1200 RADseq markers. We used genomic and geographic cline analyses to identify barrier markers based on their restricted introgression, and found that some markers are transect-specific, while others are shared between transects. Twenty-six barrier markers were shared across both transects, of which some are clustered in the same chromosomal region, suggesting that their associated genes are involved in reduced gene flow across the entire hybrid zone. Transect-specific barrier markers were twice as numerous in the southern than in the northern transect, suggesting that the overall barrier effect is weaker in northern France. We hypothesize that this is consistent with a longer period of secondary contact in southern France. The smaller number of introgressed genes in the northern transect shows considerably more gene flow towards the southern (B. spinosus) than the northern species (B. bufo). We hypothesize that hybrid zone movement in northern France and hybrid zone stability in southern France explain this pattern. The Bufo hybrid zone provides an excellent opportunity to separate a general barrier effect from localized gene flow-reducing conditions., (© 2023. The Author(s), under exclusive licence to The Genetics Society.)

Genome assemblies are increasingly being used to identify adaptive genetic variation that can help prioritize the population management of protected species. This approach may be particularly relevant to species like Blainville's horned lizard, Phrynosoma blainvillii, due to its specialized diet on noxious harvester ants, numerous adaptative traits for avoiding predation (e.g. cranial horns, dorsoventrally compressed body, cryptic coloration, and blood squirting from the orbital sinuses), and status as Species of Special Concern in California. Rangewide decline since the early 20th century, the basis of its conservation status, has been driven mainly by habitat conversion, over-collecting, and invasion of a non-native ant that displaces its native ant prey base. Here, we report on a scaffold-level genome assembly for P. blainvillii as part of the California Conservation Genomics Project (CCGP), produced using Pacific Biosciences HiFi long reads and Hi-C chromatin-proximity sequencing technology. The de novo assembly has 78 scaffolds, a total length of ~2.21 Gb, a scaffold N50 length of ~352 Mb, and BUSCO score of 97.4%. This is the second species of Phrynosoma for which a reference genome has been assembled and represents a considerable improvement in terms of contiguity and completeness. Combined with the landscape genomics data being compiled by the CCGP, this assembly will help strategize efforts to maintain and/or restore local genetic diversity, where interventions like genetic rescue, translocation, and strategic land preservation may be the only means by which P. blainvillii and other low-vagility species can survive in the fragmented habitats of California., (Published by Oxford University Press on behalf of The American Genetic Association 2023.)

Damselflies and dragonflies (Order: Odonata) play important roles in both aquatic and terrestrial food webs and can serve as sentinels of ecosystem health and predictors of population trends in other taxa. The habitat requirements and limited dispersal of lotic damselflies make them especially sensitive to habitat loss and fragmentation. As such, landscape genomic studies of these taxa can help focus conservation efforts on watersheds with high levels of genetic diversity, local adaptation, and even cryptic endemism. Here, as part of the California Conservation Genomics Project (CCGP), we report the first reference genome for the American rubyspot damselfly, Hetaerina americana, a species associated with springs, streams and rivers throughout California. Following the CCGP assembly pipeline, we produced two de novo genome assemblies. The primary assembly includes 1,630,044,487 base pairs, with a contig N50 of 5.4 Mb, a scaffold N50 of 86.2 Mb, and a BUSCO completeness score of 97.6%. This is the seventh Odonata genome to be made publicly available and the first for the subfamily Hetaerininae. This reference genome fills an important phylogenetic gap in our understanding of Odonata genome evolution, and provides a genomic resource for a host of interesting ecological, evolutionary, and conservation questions for which the rubyspot damselfly genus Hetaerina is an important model system., (© The American Genetic Association. 2023.)

The Virginia rail, Rallus limicola, is a member of the family Rallidae, which also includes many other species of secretive and poorly studied wetland birds. It is recognized as a single species throughout its broad distribution in North America where it is exploited as a game bird, often with generous harvest limits, despite a lack of systematic population surveys and evidence of declines in many areas due to wetland loss and degradation. To help advance understanding of the phylogeography, biology, and ecology of this elusive species, we report the first reference genome assembly for the Virginia rail, produced as part of the California Conservation Genomics Project (CCGP). We produced a de novo genome assembly using Pacific Biosciences HiFi long reads and Hi-C chromatin-proximity sequencing technology with an estimated sequencing error rate of 0.191%. The assembly consists of 1,102 scaffolds spanning 1.39 Gb, with a contig N50 of 11.0 Mb, scaffold N50 of 25.3 Mb, largest contig of 45 Mb, and largest scaffold of 128.4 Mb. It has a high BUSCO completeness score of 96.9% and represents the first genome assembly available for the genus Rallus. This genome assembly will help resolve questions about the complex evolutionary history of rails and evaluate the potential of rails for adaptive evolution in the face of growing threats from climate change and habitat loss and fragmentation. It will also provide a valuable resource for rail conservation efforts by quantifying Virginia rail vagility, population connectivity, and effective population sizes., (© The American Genetic Association. 2023.)

Climate-driven changes in hydrological regimes are of global importance and are particularly significant in riparian ecosystems. Riparian ecosystems in California provide refuge to many native and vulnerable species within a xeric landscape. California Tetragnatha spiders play a key role in riparian ecosystems, serving as a link between terrestrial and aquatic elements. Their tight reliance on water paired with the widespread distributions of many species make them ideal candidates to better understand the relative role of waterways versus geographic distance in shaping the population structure of riparian species. To assist in better understanding population structure, we constructed a reference genome assembly for Tetragnatha versicolor using long-read sequencing, scaffolded with proximity ligation Omni-C data. The near-chromosome-level assembly is comprised of 174 scaffolds spanning 1.06 Gb pairs, with a scaffold N50 of 64.1 Mb pairs and BUSCO completeness of 97.6%. This reference genome will facilitate future study of T. versicolor population structure associated with the rapidly changing environment of California., (© The American Genetic Association. 2023.)

The black rail, Laterallus jamaicensis, is one of the most secretive and poorly understood birds in the Americas. Two of its five subspecies breed in North America: the Eastern black rail (L. j. jamaicensis), found primarily in the southern and mid-Atlantic states, and the California black rail (L. j. coturniculus), inhabiting California and Arizona, are recognized across the highly disjunct distribution. Population declines, due primarily to wetland loss and degradation, have resulted in conservation status listings for both subspecies. To help advance understanding of the phylogeography, biology, and ecology of this elusive species, we report the first reference genome assembly for the black rail, produced as part of the California Conservation Genomics Project (CCGP). We produced a de novo genome assembly using Pacific Biosciences HiFi long reads and Hi-C chromatin-proximity sequencing technology with an estimated sequencing error rate of 0.182%. The assembly consists of 964 scaffolds spanning 1.39 Gb, with a contig N50 of 7.4 Mb, scaffold N50 of 21.4 Mb, largest contig of 44.8 Mb, and largest scaffold of 101.2 Mb. The assembly has a high BUSCO completeness score of 96.8% and represents the first genome assembly available for the genus Laterallus. This genome assembly can help resolve questions about the complex evolutionary history of rails, assess black rail vagility and population connectivity, estimate effective population sizes, and evaluate the potential of rails for adaptive evolution in the face of growing threats from climate change, habitat loss and fragmentation, and disease., (© The American Genetic Association. 2023.)

Pricklebacks (Family Stichaeidae) are generally cold-temperate fishes most commonly found in the north Pacific. As part of the California Conservation Genomics Project (CCGP), we sequenced the genome of the Monkeyface Prickleback, Cebidichthys violaceus, to establish a genomic model for understanding phylogeographic patterns of marine organisms in California. These patterns, in turn, may inform the design of marine protected areas using dispersal models based on forthcoming population genomic data. The genome of C. violaceus is typical of many marine fishes at less than 1 Gb (genome size = 575.6 Mb), and our assembly is near-chromosome level (contig N50 = 1 Mb, scaffold N50 = 16.4 Mb, BUSCO completeness = 93.2%). Within the context of the CCGP, the genome will be used as a reference for future whole genome resequencing projects, enhancing our knowledge of the population structure of the species and more generally, the efficacy of marine protected areas as a primary conservation tool across California's marine ecosystems., (© The American Genetic Association. 2022.)

Sculpins (Family Cottidae) are generally cold-temperate intertidal reef fishes most commonly found in the North Pacific. As part of the California Conservation Genomics Project (CCGP), we sequenced the genome of the Woolly Sculpin, Clinocottus analis, to establish a genomic model for understanding phylogeographic structure of inshore marine taxa along the California coast. These patterns, in turn, should further inform the design of marine protected areas using dispersal models based on genomic data. The small genome of C. analis is typical of marine fishes at less than 1 Gb (genome size = 538 Mb), and our assembly is near-chromosome level (contig N50 = 9.1 Mb, scaffold N50 = 21 Mb, BUSCO completeness = 97.9%). Within the context of the CCGP, the Woolly Sculpin genome will be used as a reference for future whole-genome resequencing projects aimed at enhancing our knowledge of the population structure of the species, and efficacy of marine protected areas across the state., (© The Author(s) 2022. Published by Oxford University Press on behalf of The American Genetic Association. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Integral projection models (IPMs) can estimate the population dynamics of species for which both discrete life stages and continuous variables influence demographic rates. Stochastic IPMs for imperiled species, in turn, can facilitate population viability analyses (PVAs) to guide conservation decision-making. Biphasic amphibians are globally distributed, often highly imperiled, and ecologically well suited to the IPM approach. Herein, we present a stochastic size- and stage-structured IPM for a biphasic amphibian, the U.S. federally threatened California tiger salamander (CTS) (Ambystoma californiense). This Bayesian model reveals that CTS population dynamics show greatest elasticity to changes in juvenile and metamorph growth and that populations are likely to experience rapid growth at low density. We integrated this IPM with climatic drivers of CTS demography to develop a PVA and examined CTS extinction risk under the primary threats of habitat loss and climate change. The PVA indicated that long-term viability is possible with surprisingly high (20%-50%) terrestrial mortality but simultaneously identified likely minimum terrestrial buffer requirements of 600-1000 m while accounting for numerous parameter uncertainties through the Bayesian framework. These analyses underscore the value of stochastic and Bayesian IPMs for understanding both climate-dependent taxa and those with cryptic life histories (e.g., biphasic amphibians) in service of ecological discovery and biodiversity conservation. In addition to providing guidance for CTS recovery, the contributed IPM and PVA supply a framework for applying these tools to investigations of ecologically similar species., (© 2022 The Ecological Society of America.)

Sea turtles represent an ancient lineage of marine vertebrates that evolved from terrestrial ancestors over 100 Mya. The genomic basis of the unique physiological and ecological traits enabling these species to thrive in diverse marine habitats remains largely unknown. Additionally, many populations have drastically declined due to anthropogenic activities over the past two centuries, and their recovery is a high global conservation priority. We generated and analyzed high-quality reference genomes for the leatherback ( Dermochelys coriacea ) and green ( Chelonia mydas ) turtles, representing the two extant sea turtle families. These genomes are highly syntenic and homologous, but localized regions of noncollinearity were associated with higher copy numbers of immune, zinc-finger, and olfactory receptor (OR) genes in green turtles, with ORs related to waterborne odorants greatly expanded in green turtles. Our findings suggest that divergent evolution of these key gene families may underlie immunological and sensory adaptations assisting navigation, occupancy of neritic versus pelagic environments, and diet specialization. Reduced collinearity was especially prevalent in microchromosomes, with greater gene content, heterozygosity, and genetic distances between species, supporting their critical role in vertebrate evolutionary adaptation. Finally, diversity and demographic histories starkly contrasted between species, indicating that leatherback turtles have had a low yet stable effective population size, exhibit extremely low diversity compared with other reptiles, and harbor a higher genetic load compared with green turtles, reinforcing concern over their persistence under future climate scenarios. These genomes provide invaluable resources for advancing our understanding of evolution and conservation best practices in an imperiled vertebrate lineage.

The California Conservation Genomics Project (CCGP) is a unique, critically important step forward in the use of comprehensive landscape genetic data to modernize natural resource management at a regional scale. We describe the CCGP, including all aspects of project administration, data collection, current progress, and future challenges. The CCGP will generate, analyze, and curate a single high-quality reference genome and 100-150 resequenced genomes for each of 153 species projects (representing 235 individual species) that span the ecological and phylogenetic breadth of California's marine, freshwater, and terrestrial ecosystems. The resulting portfolio of roughly 20 000 resequenced genomes will be analyzed with identical informatic and landscape genomic pipelines, providing a comprehensive overview of hotspots of within-species genomic diversity, potential and realized corridors connecting these hotspots, regions of reduced diversity requiring genetic rescue, and the distribution of variation critical for rapid climate adaptation. After 2 years of concerted effort, full funding ($12M USD) has been secured, species identified, and funds distributed to 68 laboratories and 114 investigators drawn from all 10 University of California campuses. The remaining phases of the CCGP include completion of data collection and analyses, and delivery of the resulting genomic data and inferences to state and federal regulatory agencies to help stabilize species declines. The aspirational goals of the CCGP are to identify geographic regions that are critical to long-term preservation of California biodiversity, prioritize those regions based on defensible genomic criteria, and provide foundational knowledge that informs management strategies at both the individual species and ecosystem levels., (© The Author(s) 2022. Published by Oxford University Press on behalf of The American Genetic Association. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

A recently published macrogenetic dataset of California's flora and fauna, CaliPopGen, comprehensively summarizes population genetic research published between 1985 and 2020. Integrating these genetic data into the requisite "best available science" upon which conservation professionals rely should facilitate the prioritization of populations based on genetic health. We evaluate the extent to which the CaliPopGen Dataset provides genetic diversity estimates that are 1) unbiased, 2) sufficient in quantity, 3) cover entire species' ranges, and 4) include potentially adaptive loci. We identified genetic diversity estimates for 4,462 spatially referenced populations of 432 species, confirming California's rich published history of population genetics research. Most recent studies used microsatellites markers, which have uniquely high levels of variation, and estimates of all genetic metrics varied significantly across marker types. Most studies used less than 10 loci for inferences, rendering parameter estimates potentially unreliable, and covered small spatial extents that include only a fraction of the studied species' California distribution (median 16.3%). In contrast, the ongoing California Conservation Genomics Project (CCGP) aims to cover the full geographical and environmental breadth of each species' occupied habitats, and uses a consistent approach based on whole-genome data. However, the CCGP will sequence only 12% of the number of individuals, and covers only about half the evolutionary diversity, of the CaliPopGen Database. There is clearly a place in the evaluation of the genetic health of California for both approaches going forward, especially if differences among studies can be minimized, and overlap emphasized. A complementary use of both datasets is warranted to inform optimal conservation decision-making. Finally, a synopsis of the available population genetic data for California, all other US states and 241 other countries, allows us to identify states and countries for which meaningful data summaries, such as CaliPopGen, could be collated and others, which have limited published data available and are prime targets for future, empirical work., (© The American Genetic Association. 2022.)

Surfperches (Family Embiotocidae) are viviparous temperate reef fishes that brood their young. This life history trait translates into limited dispersal, strong population structure, and an unusually strong potential for local adaptation in a marine fish. As part of the California Conservation Genomics Project (CCGP), we sequenced the genome of the Black Surfperch, Embiotoca jacksoni, to establish a genomic model for understanding phylogeographic patterns of marine organisms in California. These patterns, in turn, may inform the design of marine protected areas using dispersal models based on genomic data. The genome of E. jacksoni is typical of marine fishes at less than 1Gb (genome size = 635 Mb), and our assembly is near-chromosome level (contig N50 = 6.5Mb, scaffold N50 = 15.5 Mb, BUSCO = 98.1%). Within the context of the CCGP, the genome will be used as a reference for future whole genome resequencing projects aimed at enhancing our knowledge of the population structure of the species, and efficacy of Marine Protected Areas across the state., (© The Author(s) 2022. Published by Oxford University Press on behalf of The American Genetic Association.)

Conservation science and environmental regulation are sibling constructs of the latter half of the 20th century, part of a more general awakening to humanity's effect on the natural world in the wake of 2 world wars. Efforts to understand the evolution of biodiversity using the models of population genetics and the data derived from DNA sequencing, paired with legal and political mandates to protect biodiversity through novel laws, regulations, and conventions arose concurrently. The extremely rapid rate of development of new molecular tools to document and compare genetic identities, and the global goal of prioritizing species and habitats for protection are separate enterprises that have benefited from each other, ultimately leading to improved outcomes for each. In this article, we explore how the California Conservation Genomics Project has, and should, contribute to ongoing and future conservation implementation, and how it serves as a model for other geopolitical regions and taxon-oriented conservation efforts. One of our primary conclusions is that conservation genomics can now be applied, at scale, to inform decision-makers and identify regions and their contained species that are most resilient, and most in need of conservation interventions., (© The American Genetic Association. 2022.)

Sandblossoms, Linanthus parryae is a widespread annual plant species found in washes and sandy open habitats across the Mojave Desert and Eastern Sierra Nevada of California. Studies in this species have played a central role in evolutionary biology, serving as the first test cases of the shifting balance theory of evolution, models of isolation by distance, and metrics to describe the genetic structure of natural populations. Despite the importance of L. parryae in the development of landscape genetics and phylogeography, there are no genomic resources available for the species. Through the California Conservation Genomics Project, we assembled the first genome in the genus Linanthus. Using PacBio HiFi long reads and Hi-C chromatin conformation capture, we assembled 123 scaffolds spanning 1.51 Gb of the 1.96 Gb estimated genome, with a contig N50 of 18.7 Mb and a scaffold N50 of 124.8 Mb. This assembly, with a BUSCO completeness score of 88.7%, will allow us to revisit foundational ideas central to our understanding of how evolutionary forces operate in a geographic landscape. In addition, it will be a new resource to uncover adaptations to arid environments in the fragile desert habitat threatened by urban and solar farm development, climate change, and off-road vehicles., (© The American Genetic Association. 2022.)

The northwestern pond turtle, Actinemys marmorata, and its recently recognized sister species, the southwestern pond turtle, A. pallida, are the sole aquatic testudines occurring over most of western North America and the only living representatives of the genus Actinemys. Although it historically ranged from Washington state through central California, USA, populations of the northwestern pond turtle have been in decline for decades and the species is afforded state-level protection across its range; it is currently being considered for protection under the US Endangered Species Act. Here, we report a new, chromosome-level assembly of A. marmorata as part of the California Conservation Genomics Project (CCGP). Consistent with the reference genome strategy of the CCGP, we used Pacific Biosciences HiFi long reads and Hi-C chromatin-proximity sequencing technology to produce a de novo assembled genome. The assembly comprises 198 scaffolds spanning 2,319,339,408 base pairs, has a contig N50 of 75 Mb, a scaffold N50 of 146Mb, and BUSCO complete score of 96.7%, making it the most complete testudine assembly of the 24 species from 13 families that are currently available. In combination with the A. pallida reference genome that is currently under construction through the CCGP, the A. marmorata genome will be a powerful tool for documenting landscape genomic diversity, the basis of adaptations to salt tolerance and thermal capacity, and hybridization dynamics between these recently diverged species., (© The American Genetic Association. 2022.)

Incorporating measures of taxonomic diversity into research and management plans has long been a tenet of conservation science. Increasingly, active conservation programs are turning toward multispecies landscape and regional conservation actions, and away from single species approaches. This is both a reflection of changing trends in conservation science and advances in foundational technologies, including genomics and geospatial science. Multispecies approaches may provide more fundamental insights into evolutionary processes and equip managers with a more holistic understanding of the landscapes under their jurisdiction. Central to this approach are data generation and analyses which embrace and reflect a broad range of taxonomic diversity. Here, we examine the family-level phylogenetic breadth of the California Conservation Genomics Project (CCGP) based on family-level phylogenetic diversity (PD), family-level phylogenetic distinctness, and family richness. We place this in the context of the diversity present in California and compare it to the 35-plus years of genetic research compiled in the CaliPopGen Database. We found that the family-level PD in the CCGP reflected that of California very well, slightly overrepresenting chordates and underrepresenting arthropods, and that 42% of CCGP PD represented new contributions to genetic data for the state. In one focused effort, the CCGP was able to achieve roughly half the family-level PD studied over the last several decades. To maximize studied PD, future work should focus on arthropods, a conclusion that likely reflects the overall lack of attention to this hyperdiverse clade., (© The American Genetic Association. 2022.)

The glossy snake (Arizona elegans) is a polytypic species broadly distributed across southwestern North America. The species occupies habitats ranging from California's coastal chaparral to the shortgrass prairies of Texas and southeastern Nebraska, to the extensive arid scrublands of central México. Three subspecies are currently recognized in California, one of which is afforded state-level protection based on the extensive loss and modification of its preferred alluvial coastal scrub and inland desert habitat. We report the first genome assembly of A. elegans occidentalis as part of the California Conservation Genomics Project (CCGP). Consistent with the reference genome strategy of the CCGP, we used Pacific Biosciences HiFi long reads and Hi-C chromatin-proximity sequencing technologies to produce a de novo assembled genome. The assembly comprises a total of 140 scaffolds spanning 1,842,602,218 base pairs, has a contig NG50 of 61 Mb, a scaffold NG50 of 136 Mb, and a BUSCO complete score of 95.9%, and is one of the most complete snake genome assemblies. The A. e. occidentalis genome will be a key tool for understanding the genomic diversity and the basis of adaptations within this species and close relatives within the hyperdiverse snake family Colubridae., (Published by Oxford University Press on behalf of The American Genetic Association 2022.)

Keystone species are known to play a critical role in kelp forest health, including the well-known killer whales, sea otter, sea urchin, kelp trophic cascade in the Aleutian Islands, Alaska, USA. In California, a major player in the regulation of sea urchin abundance, and in turn, the health of kelp forests ecosystems, is a large wrasse, the California Sheephead, Semicossyphus pulcher. We present a reference genome for this ecologically important species that will serve as a key resource for future conservation research of California's inshore marine environment utilizing genomic tools to address changes in life-history traits, dispersal, range shifts, and ecological interactions among members of the kelp forest ecological assemblages. Our genome assembly of S. pulcher has a total length of 0.794 Gb, which is similar to many other marine fishes. The assembly is largely contiguous (N50 = 31.9 Mb) and nearly complete (BUSCO single-copy core gene content = 98.1%). Within the context of the California Conservation Genomics Project (CCGP), the genome of S. pulcher will be used as an important reference resource for ongoing whole genome resequencing efforts of the species., (© The Author(s) 2022. Published by Oxford University Press on behalf of The American Genetic Association.)

The rubber boa, Charina bottae is a semi-fossorial, cold-temperature adapted snake that ranges across the wetter and cooler ecoregions of the California Floristic Province. The rubber boa is 1 of 2 species in the family Boidae native to California and currently has 2 recognized subspecies, the Northern rubber boa C. bottae bottae and the Southern rubber boa C. bottae umbratica. Recent genomic work on C. bottae indicates that these 2 subspecies are collectively composed of 4 divergent lineages that separated during the late Miocene. Analysis of habitat suitability indicates that C. bottae umbratica montane sky-island populations from southern California will lose the majority of their habit over the next 70 yr, and is listed as Threatened under the California Endangered Species Act. Here, we report a new, chromosome-level assembly of C. bottae bottae as part of the California Conservation Genomics Project (CCGP). Consistent with the reference genome strategy of the CCGP, we used Pacific Biosciences HiFi long reads and Hi-C chromatin-proximity sequencing technology to produce a de novo assembled genome. The assembly comprises 289 scaffolds covering 1,804,944,895 bp, has a contig N50 of 37.3 Mb, a scaffold N50 of 97 Mb, and BUSCO completeness score of 96.3%, and represents the first reference genome for the Boidae snake family. This genome will enable studies of genetic differentiation and connectivity among C. bottae bottae and C. bottae umbratica populations across California and help manage locally endemic lineages as they confront challenges from human-induced climate warming, droughts, and wildfires across California., (Published by Oxford University Press on behalf of The American Genetic Association 2022.)

Dispersal drives invasion dynamics of nonnative species and pathogens. Applying knowledge of dispersal to optimize the management of invasions can mean the difference between a failed and a successful control program and dramatically improve the return on investment of control efforts. A common approach to identifying optimal management solutions for invasions is to optimize dynamic spatial models that incorporate dispersal. Optimizing these spatial models can be very challenging because the interaction of time, space, and uncertainty rapidly amplifies the number of dimensions being considered. Addressing such problems requires advances in and the integration of techniques from multiple fields, including ecology, decision analysis, bioeconomics, natural resource management, and optimization. By synthesizing recent advances from these diverse fields, we provide a workflow for applying ecological theory to advance optimal management science and highlight priorities for optimizing the control of invasions. One of the striking gaps we identify is the extremely limited consideration of dispersal uncertainty in optimal management frameworks, even though dispersal estimates are highly uncertain and greatly influence invasion outcomes. In addition, optimization frameworks rarely consider multiple types of uncertainty (we describe five major types) and their interrelationships. Thus, feedbacks from management or other sources that could magnify uncertainty in dispersal are rarely considered. Incorporating uncertainty is crucial for improving transparency in decision risks and identifying optimal management strategies. We discuss gaps and solutions to the challenges of optimization using dynamic spatial models to increase the practical application of these important tools and improve the consistency and robustness of management recommendations for invasions., (© 2022 The Ecological Society of America. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.)

CaliPopGen is a database of population genetic data for native and naturalized eukaryotic species in California, USA. It summarizes the published literature (1985-2020) for 5,453 unique populations with genetic data from more than 187,394 individuals and 448 species (513 species plus subspecies) across molecular markers including allozymes, RFLPs, mtDNA, microsatellites, nDNA, and SNPs. Terrestrial habitats accounted for the majority (46.4%) of the genetic data. Taxonomic groups with the greatest representation were Magnoliophyta (20.31%), Insecta (13.4%), and Actinopterygii (12.85%). CaliPopGen also reports life-history data for most included species to enable analyses of the drivers of genetic diversity across the state. The large number of populations and wide taxonomic breadth will facilitate explorations of ecological patterns and processes across the varied geography of California. CaliPopGen covers all terrestrial and marine ecoregions of California and has a greater density of species and georeferenced populations than any previously published population genetic database. It is thus uniquely suited to inform conservation management at the regional and state levels across taxonomic groups., (© 2022. The Author(s).)

Arctostaphylos (Ericaceae) species, commonly known as manzanitas, are an invaluable fire-adapted chaparral clade in the California Floristic Province (CFP), a world biodiversity hotspot on the west coast of North America. This diverse woody genus includes many rare and/or endangered taxa, and the genus plays essential ecological roles in native ecosystems. Despite their importance in conservation management, and the many ecological and evolutionary studies that have focused on manzanitas, virtually no research has been conducted on the genomics of any manzanita species. Here, we report the first genome assembly of a manzanita species, the widespread Arctostaphylos glauca. Consistent with the genomics strategy of the California Conservation Genomics project, we used Pacific Biosciences HiFi long reads and Hi-C chromatin-proximity sequencing technology to produce a de novo assembled genome. The assembly comprises a total of 271 scaffolds spanning 547Mb, close to the genome size estimated by flow cytometry. This assembly, with a scaffold N50 of 31Mb and BUSCO complete score of 98.2%, will be used as a reference genome for understanding the genetic diversity and the basis of adaptations of both common and rare and endangered manzanita species., (© The American Genetic Association. 2021.)

Toxin evolution in animals is one of the most fascinating and complex subjects of scientific inquiry today. Gaining an understanding of toxins poses a multifaceted challenge given the diverse modes of acquisition, evolutionary adaptations, and abiotic components that affect toxin phenotypes. Here, we highlight some of the main genetic and ecological factors that influence toxin evolution and discuss the role of antagonistic interactions and coevolutionary dynamics in shaping the direction and extent of toxicity and resistance in animals. We focus on toxic Pacific newts (family Salamandridae, genus Taricha ) as a system to investigate and better evaluate the widely distributed toxin they possess, tetrodotoxin (TTX), and the hypothesized model of arms-race coevolution with snake predators that is used to explain phenotypic patterns of newt toxicity. Finally, we propose an alternative coevolutionary model that incorporates TTX-producing bacteria and draws from an elicitor-receptor concept to explain TTX evolution and ecology.

Competing Interests: The authors declare no competing interest.

As genomic-scale data sets become economically feasible for most organisms, a key question for conservation biology is whether the increased resolution offered by new genomic approaches justifies repeating earlier studies based on traditional markers, rather than investing those same time and monetary resources in less-known species. Genomic studies offer clear advantages when the objective is to identify adaptive loci that may be critical to conservation policy-makers. However, the answer is far less certain for the population and landscape studies based on neutral loci that dominate the conservation genetics research agenda. We used Restriction-site Associated DNA sequencing (RADseq) to revisit earlier molecular studies of the IUCN Critically Endangered Magdalena River turtle (Podocnemis lewyana), documenting the conservation insights gained by increasing the number of neutral markers by several orders of magnitude. Earlier research indicated that P. lewyana has the lowest genetic diversity known for any chelonian, and little or no population differentiation among independent rivers. In contrast, the RADseq data revealed discrete population structure with isolation-by-distance within river segments and identified precise population breaks clearly delineating management units. It also confirmed that the species does not have extremely low heterozygosity and that effective population sizes are probably sufficient to maintain long-term evolutionary potential. Contrary to earlier inferences from more limited population genetic markers, our genomic data suggest that management strategies should shift from active genetic rescue to more passive protection without extreme interventions. We conclude with a list of examples of conservation studies in other vertebrates indicating that for many systems a genomic update is worth the investment., (© The American Genetic Association. 2021. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Proteins encoded by antigen-processing genes (APGs) provide major histocompatibility complex (MHC) class I (MHC-I) with antigenic peptides. In mammals, polymorphic multigenic MHC-I family is served by monomorphic APGs, whereas in certain nonmammalian species both MHC-I and APGs are polymorphic and coevolve within stable haplotypes. Coevolution was suggested as an ancestral gnathostome feature, presumably enabling only a single highly expressed classical MHC-I gene. In this view coevolution, while optimizing some aspects of adaptive immunity, would also limit its flexibility by preventing the expansion of classical MHC-I into a multigene family. However, some nonmammalian taxa, such as salamanders, have multiple highly expressed MHC-I genes, suggesting either that coevolution is relaxed or that it does not prevent the establishment of multigene MHC-I. To distinguish between these two alternatives, we use salamanders (30 species from 16 genera representing six families) to test, within a comparative framework, a major prediction of the coevolution hypothesis: the positive correlation between MHC-I and APG diversity. We found that MHC-I diversity explained both within-individual and species-wide diversity of two APGs, TAP1 and TAP2, supporting their coevolution with MHC-I, whereas no consistent effect was detected for the other three APGs (PSMB8, PSMB9, and TAPBP). Our results imply that although coevolution occurs in salamanders, it does not preclude the expansion of the MHC-I gene family. Contrary to the previous suggestions, nonmammalian vertebrates thus may be able to accommodate diverse selection pressures with flexibility granted by rapid expansion or contraction of the MHC-I family, while retaining the benefits of coevolution between MHC-I and TAPs., (© The Author(s) 2021. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.)

Tetrodotoxin (TTX) is a potent neurotoxin that was first identified in pufferfish but has since been isolated from an array of taxa that host TTX-producing bacteria. However, determining its origin, ecosystem roles, and biomedical applications has challenged researchers for decades. Recognized as a poison and for its lethal effects on humans when ingested, TTX is primarily a powerful sodium channel inhibitor that targets voltage-gated sodium channels, including six of the nine mammalian isoforms. Although lethal doses for humans range from 1.5-2.0 mg TTX (blood level 9 ng/mL), when it is administered at levels far below LD 50 , TTX exhibits therapeutic properties, especially to treat cancer-related pain, neuropathic pain, and visceral pain. Furthermore, TTX can potentially treat a variety of medical ailments, including heroin and cocaine withdrawal symptoms, spinal cord injuries, brain trauma, and some kinds of tumors. Here, we (i) describe the perplexing evolution and ecology of tetrodotoxin, (ii) review its mechanisms and modes of action, and (iii) offer an overview of the numerous ways it may be applied as a therapeutic. There is much to be explored in these three areas, and we offer ideas for future research that combine evolutionary biology with therapeutics. The TTX system holds great promise as a therapeutic and understanding the origin and chemical ecology of TTX as a poison will only improve its general benefit to humanity.

The North American tiger salamander species complex, including its best-known species, the Mexican axolotl, has long been a source of biological fascination. The complex exhibits a wide range of variation in developmental life history strategies, including populations and individuals that undergo metamorphosis; those able to forego metamorphosis and retain a larval, aquatic lifestyle (i.e., paedomorphosis); and those that do both. The evolution of a paedomorphic life history state is thought to lead to increased population genetic differentiation and ultimately reproductive isolation and speciation, but the degree to which it has shaped population- and species-level divergence is poorly understood. Using a large multilocus dataset from hundreds of samples across North America, we identified genetic clusters across the geographic range of the tiger salamander complex. These clusters often contain a mixture of paedomorphic and metamorphic taxa, indicating that geographic isolation has played a larger role in lineage divergence than paedomorphosis in this system. This conclusion is bolstered by geography-informed analyses indicating no effect of life history strategy on population genetic differentiation and by model-based population genetic analyses demonstrating gene flow between adjacent metamorphic and paedomorphic populations. This fine-scale genetic perspective on life history variation establishes a framework for understanding how plasticity, local adaptation, and gene flow contribute to lineage divergence. Many members of the tiger salamander complex are endangered, and the Mexican axolotl is an important model system in regenerative and biomedical research. Our results chart a course for more informed use of these taxa in experimental, ecological, and conservation research., Competing Interests: The authors declare no competing interest.

Living turtles are characterized by extraordinarily low species diversity given their age. The clade's extensive fossil record indicates that climate and biogeography may have played important roles in determining their diversity. We investigated this hypothesis by collecting a molecular dataset for 591 individual turtles that, together, represent 80% of all turtle species, including representatives of all families and 98% of genera, and used it to jointly estimate phylogeny and divergence times. We found that the turtle tree is characterized by relatively constant diversification (speciation minus extinction) punctuated by a single threefold increase. We also found that this shift is temporally and geographically associated with newly emerged continental margins that appeared during the Eocene-Oligocene transition about 30 million years before present. In apparent contrast, the fossil record from this time period contains evidence for a major, but regional, extinction event. These seemingly discordant findings appear to be driven by a common global process: global cooling and drying at the time of the Eocene-Oligocene transition. This climatic shift led to aridification that drove extinctions in important fossil-bearing areas, while simultaneously exposing new continental margin habitat that subsequently allowed for a burst of speciation associated with these newly exploitable ecological opportunities., Competing Interests: The authors declare no competing interest.

Hybridization between native and non-native species is an ongoing global conservation threat. Hybrids that exhibit traits and tolerances that surpass parental values are of particular concern, given their potential to outperform native species. Effective management of hybrid populations requires an understanding of both physiological performance and the underlying mechanisms that drive transgressive hybrid traits. Here, we explore several aspects of the hybridization between the endangered California tiger salamander (Ambystoma californiense; CTS) and the introduced barred tiger salamander (Ambystoma mavortium; BTS). We assayed critical thermal maximum (CTMax) to compare the ability of CTS, BTS and F1 hybrids to tolerate acute thermal stress, and found that hybrids exhibit a wide range of CTMax values, with 33% (4/12) able to tolerate temperatures greater than either parent. We then quantified the genomic response, measured at the RNA transcript level, of each salamander, to explore the mechanisms underlying thermal tolerance strategies. We found that CTS and BTS have strikingly different values and tissue-specific patterns of overall gene expression, with hybrids expressing intermediate values. F1 hybrids display abundant and variable degrees of allele-specific expression (ASE), likely arising from extensive compensatory evolution in gene regulatory mechanisms between CTS and BTS. We found evidence that the proportion of genes with allelic imbalance in individual hybrids correlates with their CTMax, suggesting a link between ASE and expanded thermal tolerance that may contribute to the success of hybrid salamanders in California. Future climate change may further complicate management of CTS if hybrid salamanders are better equipped to deal with rising temperatures., (© 2020 John Wiley & Sons Ltd.)

Populations of the western spadefoot (Spea hammondii) in southern California occur in one of the most urbanized and fragmented landscapes on the planet and have lost up to 80% of their native habitat. Orange County is one of the last strongholds for this pond-breeding amphibian in the region, and ongoing restoration efforts targeting S. hammondii have involved habitat protection and the construction of artificial breeding ponds. These efforts have successfully increased breeding activity, but genetic characterization of the populations, including estimates of effective population size and admixture between the gene pools of constructed artificial and natural ponds, has never been undertaken. Using thousands of genome-wide single-nucleotide polymorphisms, we characterized the population structure, genetic diversity, and genetic connectivity of spadefoots in Orange County to guide ongoing and future management efforts. We identified at least 2, and possibly 3 major genetic clusters, with additional substructure within clusters indicating that individual ponds are often genetically distinct. Estimates of landscape resistance suggest that ponds on either side of the Los Angeles Basin were likely interconnected historically, but intense urban development has rendered them essentially isolated, and the resulting risk of interruption to natural metapopulation dynamics appears to be high. Resistance surfaces show that the existing artificial ponds were well-placed and connected to natural populations by low-resistance corridors. Toad samples from all ponds (natural and artificial) returned extremely low estimates of effective population size, possibly due to a bottleneck caused by a recent multi-year drought. Management efforts should focus on maintaining gene flow among natural and artificial ponds by both assisted migration and construction of new ponds to bolster the existing pond network in the region., (© The American Genetic Association. 2021. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)