Western North America Research Articles

Mortality Events in Yuma Myotis (Myotis yumanensis) Due to White-Nose Syndrome in Washington, USA.

The impacts of white-nose syndrome (WNS) on many bat species in eastern North America have been well documented because of the length of time that the causative agent, Pseudogymnoascus destructans (Pd), has been present and the ability to monitor bat hibernacula in that region. However, the disease outcomes for bat species in western North America are less known because of the more recent arrival of Pd and the challenges associated with monitoring hibernating bat populations in parts of the western US. We report on mortality events involving Yuma myotis (Myotis yumanensis) bats at two locations in King and Benton counties, Washington, US, that were attributed to WNS during the late winters of 2020-21 and 2024, respectively. All bats that were grossly examined had depleted subcutaneous white adipose tissue, tested positive for the presence of Pd, had histopathologic lesions consistent with WNS, and did not exhibit evidence of other disease processes that may have contributed to death. Mortality was likely higher than what was documented because the locations of the Pd-contaminated hibernacula from which the bats originated were inaccessible or unknown and thus could not be surveyed. These findings indicate that Yuma myotis may be highly susceptible to WNS, and close monitoring is warranted to understand how WNS will affect population trends in this (and other) western bat species.

Iguanas rafted more than 8,000 km from North America to Fiji

Founder-event speciation can occur when one or more organisms colonize a distant, unoccupied area via long-distance dispersal, leading to the evolution of a new species lineage. Species radiations established by long-distance, and especially transoceanic, dispersal can cause substantial shifts in regional biodiversity. Here, we investigate the occurrence and timing of the greatest known long-distance oceanic dispersal event in the history of terrestrial vertebrates-the rafting of iguanas from North America to Fiji. Iguanas are large-bodied herbivores that are well-known overwater dispersers, including species that colonized the Caribbean and the Galápagos islands. However, the origin of Fijian iguanas had not been comprehensively tested. We estimated the phylogenetic relationships and evolutionary timescale of the iguanid lizard radiation using genome-wide exons and ultraconserved elements (UCEs). Those data indicate that the closest living relative of extant Fijian iguanas is the North American desert iguana and that the two taxa likely diverged during the late Paleogene near or after the onset of volcanism that produced the Fijian archipelago. Biogeographic models estimate North America as the most probable ancestral range of Fijian iguanas. Our analyses support the hypothesis that iguanas reached Fiji via an extraordinary oceanic dispersal event from western North America, and which spanned a fifth of the earth's circumference (>8,000 km). Overwater rafting of iguanas from North America to Fiji strengthens the importance of founder-event speciation in the diversification of iguanids and elucidates the scope of long-distance dispersal across terrestrial vertebrates.

New remarkably complete skeleton of Mixodectes reveals arboreality in a large Paleocene primatomorphan mammal following the Cretaceous-Paleogene mass extinction

Mixodectids are poorly understood placental mammals from the Paleocene of western North America that have variably been considered close relatives of euarchontan mammals (primates, dermopterans, and scandentians) with hypothesized relationships to colugos, extinct plagiomenids, and/or microsyopid plesiadapiforms. Here we describe the most complete dentally associated skeleton yet recovered for a mixodectid, specifically Mixodectes pungens from the early Paleocene of the San Juan Basin, New Mexico. A partial skull with all the teeth erupted and associated axial skeleton, forelimbs, and hind limbs, with epiphyses fused, indicate that it was a mature adult. Results from cladistic analyses incorporating new data robustly support primatomorphan (Primates + Dermoptera) affinities of Mixodectidae, but relationships within Euarchonta are less clear, with Mixodectes recovered as a stem primatomorphan, stem dermopteran, or stem primate. Analyses of postcrania suggest that M. pungens was a relatively large (~ 1.3 kg), claw-climbing arborealist capable of frequent clinging on large diameter vertical supports. With teeth suggesting an omnivorous diet that included leaves, M. pungens occupied a unique ecological niche in the early Paleocene of North America that differed from contemporary, arboreal plesiadapiforms that were smaller and more frugivorous. Euarchontans were thus a more diverse radiation in the early Cenozoic than previously appreciated.

Historical fire regimes in whitebark pine ecosystems of west‐central British Columbia

AbstractForest ecosystems across western North America are experiencing increasingly large and severe wildfire disturbances. From 2012 to 2024, approximately 600,000 ha of forest in Tweedsmuir Provincial Park, British Columbia's largest protected area, were impacted by wildfires. These wildfires burned primarily through lower elevation subboreal forests, but high‐severity fire also impacted subalpine and treeline ecosystems across the mountainous provincial park. Whitebark pine is a long‐lived and endangered high‐elevation tree species experiencing extensive mortality throughout western North America from an invasive pathogen and recent large‐scale outbreaks of mountain pine beetle. To understand the impacts of changing fire regimes on subboreal and subalpine whitebark pine ecosystems, we reconstructed the first fire history in North Tweedsmuir Provincial Park. Eleven study sites containing whitebark pine were sampled along lakeshores, islands, knolls, and ridgelines. Our fire history record indicated two key findings. First, fire‐scarred trees provided evidence of low‐severity fire at all 11 study sites. Our dendrochronological record covered 830 years (1190–2020) and included 127 fire scars during a 580‐year period (1377–1957), with a composite mean fire interval of 8 years in the period 1580–1957 recorded across the study area. Second, our results highlight centuries of Indigenous fire stewardship that, combined with lightning, comprised the historical fire regime. Prior to 20th century fire suppression policies, the fire regime was characterized by shorter fire intervals than the contemporary period, effectively reducing available fuels, and creating a mosaic of burned and unburned forests across the landscape. Our research findings highlight the need for proactive and dynamic wildfire management that supports multiple cultural and ecological values across protected areas.

Phenological sensitivity of Bromus tectorum genotypes depends on current and source environments

AbstractPlants respond to their environment with both short‐term, within‐generation trait plasticity, and long‐term, between‐generation evolutionary changes. However, the relative magnitude of plant responses to short‐ and long‐term changes in the environment remains poorly understood. Shifts in phenological traits can serve as harbingers for responses to environmental change, and both a plant's current and source (i.e., genotype origin) environment can affect plant phenology via plasticity and local adaptation, respectively. To assess the role of current and source environments in explaining variation in flowering phenology of Bromus tectorum, an invasive annual grass, we conducted a replicated common garden experiment using 92 genotypes collected across western North America. Replicates of each genotype were planted in two densities (low = 100 seeds/1 m2, high = 100 seeds/0.04 m2) under two different temperature treatments (low = white gravel; high = black gravel; 2.1°C average difference) in a factorial design, replicated across four common garden locations in Idaho and Wyoming, USA. We tested for the effect of current environment (i.e., density treatment, temperature treatment, and common garden location), source environment (i.e., genotype source climate), and their interaction on each plant's flowering phenology. Flowering timing was strongly influenced by a plant's current environment, with plants that experienced warmer current climates and higher densities flowering earlier than those that experienced cooler current climates and lower densities. Genotypes from hot and dry source climates flowered consistently earlier than those from cool and wet source climates, even after accounting for genotype relatedness, suggesting that this genetically based climate cline is a product of natural selection. We found minimal evidence of interactions between current and source environments or genotype‐by‐environment interactions. Phenology was more sensitive to variation in the current climate than to variation in source climate. These results indicate that cheatgrass phenology reflects high levels of plasticity as well as rapid local adaptation. Both processes likely contribute to its current success as a biological invader and its capacity to respond to future environmental change.

Energetic Value of Women's Work: Assessing Maternal Energetic Costs From Acorn Foraging.

Perceptions of female energetic contributions and their role in human evolution are limited. This exploratory study compares energy expenditure, return rate, and foraging efficiency between infant carrying methods in females simulating acorn foraging practices by Indigenous communities in western North America. After resting metabolic rate (RMR) was collected, female volunteers (n = 6, age: 21-37) conducted three 1-h bouts of acorn foraging. First, volunteers foraged unloaded (control) while for the second and third bouts they foraged carrying a traditional basketry cradle or a chest sling (randomized order) with 4.5 kg sandbags. Energy expenditure (EE) was measured through indirect calorimetry, physical activity intensity was assessed using accelerometry, and foraging return rates (RR) were calculated after acorn processing. The inter-bout results are not statistically significant. Findings show, however, that foraging RR largely surpasses EE irrespective of infant carrying method. The cradle carrying technique resulted in the largest mean EE, yet it was more efficient than the sling-carrying method. Most of the time foraging was spent at moderate physical intensity, especially during cradle-carrying bouts compared to the sling-carrying and control groups. This small exploratory study demonstrates the caloric contributions by and foraging efficiency of females. Our findings emphasize that child-carrying techniques using basketry cradles allow for improved efficiency in foraging returns compared to more commonly used slings. Our results reinforce previous findings of female foraging efficiency despite the energetic demands of infant carrying and emphasize the energetic contributions of females to human evolution even during child-rearing.

Integrative species delimitation methods infer species boundaries in the Lomatium foeniculaceum complex and indicate an evolutionary history from the Southwest towards the Northeast in western North America.

Integrative species delimitation methods infer species boundaries in the Lomatium foeniculaceum complex and indicate an evolutionary history from the Southwest towards the Northeast in western North America.

The cultural macroevolution of lithic technological strategies in Northern and Western North America during the upper Pleistocene and Holocene

The cultural macroevolution of lithic technological strategies in Northern and Western North America during the upper Pleistocene and Holocene

Candidate DNA and RNA viruses of Drosophila suzukii from Canada and Germany, and their interactions with Wolbachia.

Candidate DNA and RNA viruses of Drosophila suzukii from Canada and Germany, and their interactions with Wolbachia.

Geographic distributions in Chromosera species—continental and oceanic barriers, including a new species, a new variety and a new combination

Chromosera cyanophylla was initially described from Europe and, when it was named type of the genus, was thought to be distributed throughout Europe and North America. Molecular phylogenies revealed that Chromosera “cyanophylla” from eastern and western North America represent two separate species and that neither is conspecific with European C. cyanophylla nor with the more recently described C. ambigua. Here we describe a new species from western North America as Chromosera loreleiae. We resurrect the species Peck described from eastern North America as Agaricus lilacifolius by recombining it in Chromosera and describe a new lilac variety lacking yellow pigments. The range of C. cyanophylla s.s. across eastern Eurasia including China is confirmed. Chromosera citrinopallida, described from Washington state, USA, comprised one clade in Washington that we infer is C. citrinopallida s.s. and a separate circumarctic clade distributed in Scandinavia, Iceland and Alaska.

When the sand blossoms: Phylogeny, trait evolution, and geography of speciation in Linanthus.

Understanding how plants successfully diversified in novel environments is a central question in evolutionary biology. Linanthus occurs in arid areas of western North America and exhibits extensive floral trait variation, multiple color polymorphisms, differences in blooming time, and variation in life history strategies. We reconstructed the evolutionary history of this genus. We generated restriction-site associated (ddRAD) sequences for 180 individuals and target capture (TC) sequences for 63 individuals, with complete species sampling. Using maximum likelihood and pseudo-coalescent approaches, we inferred phylogenies of Linanthus and used them to model the evolution of phenotypic traits and investigate the genus's geographic speciation history. Relationships are consistent and well supported with both ddRAD and TC data. Most species are monophyletic despite extensive local sympatry and range overlap, suggesting strong isolating barriers. The non-monophyly of the night-blooming and perennial species may be due to rapid speciation or cryptic diversity. Perenniality likely evolved from annuality, a rare shift in angiosperms. Night-blooming evolved three times independently. Flower color polymorphism is an evolutionarily labile trait that is likely ancestral. No single geographic mode of speciation characterizes this diversification, but most species overlap in range, which suggests that they evolved in parapatry. Our results illustrate the complexity of phylogenetic inference for recent radiations, even with multiple sources of genomic data and extensive sampling. This analysis provides a foundation for understanding aridity adaptations, such as evolution of flower color polymorphisms, night-blooming, and perenniality, as well as speciation mechanisms.

Repeatable Selection on Large Ancestry Blocks in an Avian Hybrid Zone.

Hybrid zones create natural tests of genetic incompatibilities by combining loci from 2 species in the same genetic background in the wild, making them useful for identifying loci involved in both intrinsic and ecological (extrinsic) isolation. Two Swainson's thrush subspecies form a hybrid zone in western North America. These coastal and inland subspecies exhibit dramatic differences in migration routes; their hybrids exhibit poor migratory survival, suggesting that ecological incompatibilities maintain this zone. We used a panel of ancestry informative markers to identify repeated patterns of selection and introgression across 4 hybrid populations that span the entire length of the Swainson's thrush hybrid zone. Two repeatable patterns consistent with selection against incompatibilities-steep genomic clines and few transitions between ancestry states-were found in large genetic blocks on chromosomes 1 and 5. The block on chromosome 1 showed evidence for inland subspecies introgression while the block on chromosome 5 exhibited coastal subspecies introgression. Some regions previously associated with migratory phenotypes, including migratory orientation, or exhibiting misexpression between the subspecies exhibited signatures of selection in the hybrid zone. Both selection and introgression across the genome were shaped by genomic structural features and evolutionary history, with stronger selection and reduced introgression in regions of low recombination, high subspecies differentiation, positive selection within the subspecies, and on macrochromosomes. Cumulatively, these results suggest that linkage among loci interacts with divergent selection and past divergent evolution between species to strengthen barriers to gene flow within hybrid zones.

Mast hindcasts reveal pervasive effects of extreme drought on a foundational conifer species.

Predicting seed production is challenging because many plants produce highly variable crops among years (i.e. masting), but doing so can inform forest management, conservation, and our understanding of ecosystem trajectories in a changing climate. We evaluated the ability of an existing model to forecast masting in an ecologically and culturally important tree species in the southwestern United States, Pinus edulis. Annual seed cone production was predicted using cross-validation techniques on two unique out-of-sample datasets, representing different collection methods and spatial scales (cone scars and cone counts). We then hindcasted this model into the historical past to evaluate whether seed production has declined with the onset of extreme drought conditions in western North America. The evaluated model had fair skill, with root-mean-squared error of 6%. The model had better skill predicting the interannual variability within a site than among sites (i.e. within years). Hindcast analyses indicated recent (2000-2024) mean annual cone production was 30.6% lower than in the past century (1900-1999). Mast forecasts are within reach, but much room remains for improvement. Forecasts may be a powerful tool to anticipate the effects of climate change on forests and woodlands.

Genomic Vulnerability of a Sentinel Mammal Under Climate Change.

Climate change poses a significant threat to biodiversity, particularly in alpine ecosystems where species have already undergone elevational range shifts. Genomics can be used to estimate the adaptive potential of species, as well as the shift in adaptive genomic composition necessary for populations to adjust to climate change (e.g., genomic offset). Here, we investigated patterns of climate-mediated adaptive genetic variation and predicted the degree of genomic offset under multiple climate change scenarios for a sentinel alpine mammal, the American pika (Ochotona princeps). We collected genome-wide data (29,709 SNPs) from 363 individuals spanning the entire range in western North America and employed genotype-environment association analyses to identify 924 robust outlier SNPs, several of which were linked to genes previously associated with high elevation and hypoxia responses in various pika species (Ochotonidae). Adaptive genomic variation was most strongly influenced by mean warmest month temperature, followed by precipitation of the coldest quarter. Spatial patterns of genomic offset were heterogeneous, significantly predicted by levels of adaptive genetic variation, elevation and latitude. Sites within the Northern Rocky Mountains exhibited the highest genomic offset under projected climate change despite possessing high levels of adaptive genetic variation. As such, while our study provides an example of how genomic data can be used to explore the potential consequences of climate change, it further highlights the need for careful consideration of genomic offset values within their proper ecological context.

Fatal interactions: pneumonia in bighorn lambs following experimental exposure to carriers of Mycoplasma ovipneumoniae.

We hypothesized that bighorn sheep ewes with chronic nasal Mycoplasma ovipneumoniae carriage are the source of infection that results in fatal lamb pneumonia. We tested this hypothesis in captive bighorn ewes at two study facilities over a 5-year period, by identifying carrier ewes and then comparing lamb fates in groups that did (exposed pens) or did not (non-exposed pens) include one or more carrier ewes. Most (23 of 30) lambs born in exposed pens, but none of 11 lambs born in non-exposed pens, contracted fatal pneumonia. In addition, surviving lambs in exposed pens showed obvious signs of respiratory disease while lambs in non-exposed pens did not. In crossover experiments, individual non-carrier ewes had lambs that experienced fatal pneumonia in years when housed in exposed pens, but not in years when housed in non-exposed pens. The results of these studies clearly associate lamb pneumonia to exposure to M. ovipneumoniae carrier ewes, consistent with a necessary role for this agent in epizootic pneumonia of bighorn sheep. These data specifically highlight the role of chronic M. ovipneumoniae carriage by some bighorn ewes in the epidemiology of this population-limiting wildlife disease.IMPORTANCEBighorn sheep populations, historically important in mountain and canyon ecosystems of western North America, declined precipitously following European settlement of North America and remain depressed today. One factor contributing to these declines and lack of recovery is epizootic pneumonia caused by the bacterium Mycoplasma ovipneumoniae. This pathogen arrived with settlers' domestic sheep and goats and spilled over to infect bighorn sheep, a process that continues to this day. Bighorn losses from this disease include high rates of mortality (median, approaching 50%) of all ages of bighorn sheep on initial exposure, followed in subsequent years to decades by mortality largely limited to young lambs. The source of infection causing persistent lamb losses is the focus of the research described here. Conducting these studies on groups of captive bighorn sheep enabled demonstration of clear linkage between largely asymptomatic nasal carriage of M. ovipneumoniae by ewes and outbreaks of fatal pneumonia in lambs.

High Diversity and Low Genetic Differentiation Among Geographic Populations of Myotis yumanensis in Western Canada.

Myotis yumanensis is a small insectivorous bat distributed in Western North America and is susceptible to white-nose syndrome, a devastating fungal disease. Effective management of the disease in M. yumanensis requires an understanding of its population structure to identify possible routes and barriers of disease transmission. Here we used nine microsatellite loci to investigate genetic variation among 336 M. yumanensis from 10 locations in Western Canada. Our analyses revealed high genetic diversity and low but statistically significant genetic differentiation among several geographic populations. Interestingly, though geographically it was not the most distant, the Lillooet population showed the highest genetic differentiation from others, suggesting factors other than geographic distance also contributed to gene flow in this species. While white-nose syndrome has been reported in M. yumanensis populations in neighbouring Washington State in the United States of America, as of 2023, the causative pathogen was not detected on the wings of our analyzed 336 M. yumanensis bats in Western Canada. However, continuing monitoring is required to provide the most updated information about the white-nose syndrome status in these populations. The knowledge of M. yumanensis population structure in Western Canada will help develop effective management strategies for protecting this bat species from white-nose syndrome.

Regional exhumation of the Laramide Province

Western North America is the archetypical Cordilleran orogenic system that preserves a Mesozoic to Cenozoic record of oceanic Farallon plate subduction-related processes. After prolonged Late Jurassic through mid-Cretaceous normal-angle Farallon plate subduction that produced the western North American batholith belt and retroarc fold-thrust belt, a period of low-angle, flat-slab subduction during Late Cretaceous−Paleogene time caused upper plate deformation to migrate eastward in the form of the Laramide basement-involved uplifts, which partitioned the original regional foreland basin. Major questions persist about the mechanism and timing of flat-slab subduction, the trajectory of the flat-slab, inter-plate coupling mechanism(s), and the upper-plate deformational response to such processes. Critical for testing various flat-slab hypotheses are the timing, rate, and distribution of exhumation experienced by the Laramide uplifts as recorded by low-temperature thermochronology. In this contribution, we address the timing of regional exhumation of the Laramide uplifts by combining apatite fission-track (AFT) and (U-Th-Sm)/He (AHe) data from 29 new samples with 564 previously published AFT, AHe, and zircon (U-Th)/He ages from Laramide structures in Arizona, Utah, Wyoming, Colorado, Montana, and South Dakota, USA. We integrate our results with existing geological constraints and with new regional cross sections to reconstruct the spatial and temporal history of exhumation driven by Laramide deformation from the mid-Cretaceous to Paleogene. Our analysis suggests a two-stage exhumation of the Laramide province, with an early phase of localized exhumation occurring at ca. 100−80 Ma in Wyoming and Montana, followed by a more regional period of exhumation at ca. 70−50 Ma. Generally, the onset of enhanced exhumation occurs earlier in the northern Laramide province (ca. 90 Ma) and later in the southern Laramide province (ca. 80 Ma). Thermal history models of selected samples along regional cross sections through Utah−Arizona−New Mexico and Wyoming−South Dakota show that exhumation occurred contemporaneously with deformation, implying that Laramide basement block exhumation is coupled with regional deformation. These results have implications for testing proposed migration pathway models of Farallon flat-slab and for how upper-plate deformation is expressed in flat-slab subduction zones in general.

Global and regional burden of kidney cancer: Analysis and future predictions based on GBD data from 1990 to 2021.

521 Background: Kidney cancer, as a common urological malignancy with poor prognosis, shows significant variations in incidence and mortality rates in different countries and regions worldwide. This study aims to investigate the global burden and trends of kidney cancer from 1990 to 2021, and to analyze its associations with various factors. Methods: First, data on the number of kidney cancer cases and age-standardized rates (ASR) of incidence, prevalence, mortality, and disability-adjusted life years (DALYs) from 1990 to 2021 were collected and analyzed globally. Subgroup analyses based on sex, country, region, and sociodemographic index (SDI) were then performed to examine the current status and time trends from 1990 to 2021 of kidney cancer in the total population and various subgroups. In addition, the age-period-cohort (APC) and Bayesian age-period-cohort analysis (BAPC) models were used to track dynamic changes in disease burden and predict future trends of the above indicators. Finally, risk factors and trend changes related to kidney cancer mortality within SDI subgroups were analyzed. Results: Globally, the incidence of kidney cancer increased sharply from 1.6×10 5 in 1990 to 3.9×10 5 in 2021. The ASRs for all measures of kidney cancer burden were higher for men than for women. China has the highest number of cases, deaths and DALYs in 2021, followed by the United States. The country of Cabo Verde and the region of Western Europe have the fastest growing ASRs for both incidence and mortality. 49 countries or regions, mainly in Western Europe and North America, have a decreasing trend in ASR for mortality over the period. Overall, the burden of kidney cancer increased with higher SDIs, with countries with middle and low-middle SDIs having the fastest growing burden of kidney cancer, such as North Africa and the Middle East. The APC and BAPC models predicted a steady decline in the ASRs of incidence, prevalence, mortality and DALYs for kidney cancer over the next 20 years, although the APC model predicted a continued steady increase in the absolute numbers of these indicators. In addition, high BMI and smoking were identified as the major risk factors contributing to kidney cancer deaths. High body mass index was particularly pronounced in countries with low SDIs. Conclusions: From 1990 to 2021, the incidence of kidney cancer has declined from historical peaks in developed countries, but remains on an upward trend in developing countries and represents a significant health threat. Revealing some previously unreported findings, the formulation of appropriate policies to reduce population exposure to risk factors associated with kidney cancer could be beneficial in the context of global aging trends.

Resolving issues in the genus Dioxys (Hymenoptera, Megachilidae, Dioxyini) in the West Palaearctic with a new identification key.

The bee genus Dioxys is widely distributed across the Holarctic from the Mediterranean basin to western North America but is species-poor, and individual species can prove challenging to identify. Consequently, there has been a lack of consensus as to how many species actually exist. In the West Palaearctic, the number of species has varied from six to ten, depending on the worker. Due to a previously incorrect assessment of publication dates, Dioxysrotundatus Pérez, 1884, sp. resurr. is restored as the senior synonym of Dioxysmoestus Costa, 1884, syn. nov. The relationship between this species and Dioxysatlanticus Saunders, 1904 is clarified, with the latter restricted to the islands of Gran Canaria and Tenerife (Spain). Dioxysrufipes Morawitz, 1875 is considered part of the West Palaearctic fauna, replacing "D.moestus" sensu Warncke (1977) in the eastern Mediterranean. Dioxysmontanus Heinrich, 1977, sp. resurr. is revalidated from synonymy with Dioxyscinctus (Jurine, 1807). Dioxyspumilus Gerstäcker, 1869 is found to consist of four species, D.pumilus (eastern Mediterranean), Dioxysvaripes De Stefani, 1887, sp. resurr. (western Mediterranean), Dioxyscypriacus Popov, 1944, sp. resurr. (Cyprus), and Dioxyshermonensis sp. nov. (Israel: Mount Hermon). A neotype is designated for D.varipes, and Dioxysfalsificus Engel, 2023, syn. nov. is synonymised with it. This contribution produces a total of 13 species for the West Palaearctic region, and illustrates the degree to which persistent taxonomic problems exist even within small bee genera.

Geography and Environment Shape Spatial Genetic Variation and Predict Climate Maladaptation Across Isolated and Disjunct Populations of Pinus muricata.

Assessing the evolutionary potential of rare species with limited migration amidst ongoing climate change requires an understanding of patterns of genetic variation and local adaptation. In contrast to the large distributions and population sizes of most pines, Pinus muricata (bishop pine) occurs in a few isolated populations along coastal western North America and is listed as threatened by the IUCN. To quantify how current genetic variation is influenced by distribution and environment, we generated reduced representation DNA sequencing data for most extant populations of P. muricata (12 locations, 7828 loci). We assessed geographic variation in differentiation and diversity and used genetic-environment association (GEA) analyses to characterise the contribution of environmental variables to local adaptation and genetic structure. Based on these inferences, we quantified genomic offset as a relative estimate of potential maladaptation under mild (SSP1-2.6) and severe (SSP5-8.5) climate change scenarios across 2041-2060 and 2081-2100. Despite occurring in small, isolated populations, genetic diversity was not low in P. muricata. Population differentiation was, however, defined across a hierarchy of spatial scales, with stands generally forming genetically identifiable groups across latitude and environments. GEA analyses implicated temperature- and soil-related variables as most strongly contributing to local adaptation. Estimates of maladaptation to future climate varied non-linearly with latitude, increased with severity of projections and over time, and were predicted by increases in annual temperature. Our results suggest that isolation and local adaptation have shaped genetic variation among disjunct populations and that these factors may shape maladaptation risk under projected climate change.