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USGS2023

Biodiversity connections—‘ties that bind’

Connectivity is a foundational concept in ecology and conservation and was the organising theme for the 2022 Annual Meeting of the Southeastern Fishes Council, a professional organisation dedicated to the study and conservation of freshwater fishes native to the southeast region of the United States (US). We introduce a Special Contribution of six papers selected from presentations at that meeting that illustrate perspectives on connections created by fish migration and dispersal, evolved life histories and habitat affinities and interspecific facilitation. Although focused on streams of the southeast US, each of these topics is broadly relevant to freshwater fish conservation, particularly with respect to causes and consequences of migratory fish depletion, population fragmentation and species declines. Many other connections relevant to the ecology and conservation of freshwater fishes remain relatively unexplored but could substantively advance conservation. We highlight the potential that species evolutionary histories, that is connections through time, reconstructed using species distributions and phylogenies may improve predictions of species responses to environmental change. Identifying species interdependencies, including undiscovered interactions that support survival or reproduction, could provide insights into how species losses may cascade as aquatic communities unravel. Finally, efforts to elucidate diverse connections between people and freshwater biodiversity, particularly where fisheries are historic and streams mostly go unnoticed, may prove essential to building public support for conservation measures. A research agenda anchored on ‘biodiversity connections’ has the potential to advance ecological understanding and public engagement, elements essential to conserving freshwater fishes.

Ecology of Freshwater Fish↗

USGS1998

The ichnologic record of the continental invertebrate invasion; evolutionary trends in environmental expansion, ecospace utilization, and behavioral complexity

The combined study of continental trace fossils and associated sedimentary facies provides valuable evidence of colonization trends and events throughout the Phanerozoic. Colonization of continental environments was linked to the exploitation of empty or under-utilized ecospace. Although the nonmarine trace fossil record probably begins during the Late Ordovician, significant invasion of nonmarine biotopes began close to the Silurian-Devonian transition with the establishment of a mobile arthropod epifauna (Diplichnites ichnoguild) in coastal marine to alluvial plain settings. Additionally, the presence of vertical burrows in Devonian high-energy fluvial deposits reflects the establishment of a stationary, deep suspension-feeding infauna of the Skolithos ichnoguild. The earliest evidence of plant-arthropod interaction occurred close to the Silurian-Devonian boundary, but widespread and varied feeding patterns are known from the Carboniferous. During the Carboniferous, permanent subaqueous lacustrine settings were colonized by a diverse, mobile detritus-feeding epifauna of the Mermia ichnoguild, which reflects a significant palaeoenvironmental expansion of trace fossils. Paleozoic ichnologic evidence supports direct routes to the land from marginal marine environments, and migration to lakes from land settings. All nonmarine sedimentary environments were colonized by the Carboniferous, and subsequent patterns indicate an increase in ecospace utilization within already colonized depositional settings. During the Permian, back-filled traces of the Scoyenia ichnoguild record the establishment of a mobile, intermediate-depth, deposit-feeding in-fauna in alluvial and transitional alluvial-lacustrine sediment. Diversification of land plants and the establishment of ecologically diverse plant communities through time provided new niches to be exploited by arthropods. Nevertheless, most ot the evolutionary feeding innovations took place relatively early, during the Late Palaeozoic or early Mesozoic. A stationary deep unfauna, the Camborygma ichnoguild, was developed in Triassic transitional alluvial-lacustrinbe deposits. Terrestrial environments hosted the rise of complex social behavioral patterns, as suggested by the probable presence of hymenopteran and isopteran nests in Triassic paleosols. An increase in diversity of trace fossils is detected in Triassic-Jurassic eolian deposits, where the ichnofauna displays more varied behavioral patterns than their Paleozoic counterparts. Also, a mobile, intermediate-depth, deposit-feeding infauna, the Vagorichnus ichnoguild, was established in deep lake environments during the Jurassic. In contrast to Paleozoic permanent subaqueous assemblages typified by surface trails, Jurassic ichnocoenoses are dominated by infaunal burrows. High density of infaunal deposit-feeding traces of the Planolites ichnoguild caused major disruption of lacustrine sedimentary fabrics during the Cretaceous. Most insect mouthpart classes, functional feeding groups, and dietary guilds were established by the end of the Cretaceous. Diversification of modern insects is recorded by the abundance and complexity of structures produced by wasps, bees, dung-beetles, and termites in Cretaceous-Tertiary paleosols. The increase in bioturbation migrated from fluvial and lake-margin settings to permanent subaqueous lacustrine environments through time.

Palaios↗

USGS2025

Ecological acclimation: A framework to integrate fast and slow responses to climate change

Ecological responses to climate change occur across vastly different time-scales, from minutes for physiological plasticity to decades or centuries for community turnover and evolutionary adaptation. Accurately predicting the range of ecosystem trajectories will require models that incorporate both fast processes that may keep pace with climate change and slower ones likely to lag behind and generate disequilibrium dynamics. However, the knowledge necessary for this integration is currently fragmented across disciplines. We develop ‘ecological acclimation’ as a unifying framework to emphasize the similarity of dynamics driven by processes operating on dramatically different time-scales and levels of biological organization. The framework focuses on ecoclimate sensitivities, measured as the change in an ecological response variable per unit of climate change. Acclimation processes acting at different time-scales cause these sensitivities to shift in magnitude and even direction over time. We highlight shifting ecoclimate sensitivities in case studies from diverse ecosystems, including terrestrial plant communities, coral reefs and soil microbiomes. Models predicting future ecosystem states inevitably make assumptions about acclimation processes; these assumptions must be explicit for users to evaluate whether a model is appropriate for a given forecast horizon. Similarly, decision frameworks that clearly account for multiple acclimation processes and their distinct time-scales will help natural resource managers plan for ecological impacts of climate change from years to many decades into the future. We outline a synthetic research programme focused on the time-scales of ecological acclimation to reduce uncertainty in ecological forecasts.

Functional Ecology↗

USGS2014

Relaxed selection causes microevolution of seawater osmoregulation and gene expression in landlocked Alewives

Ecological transitions from marine to freshwater environments have been important in the creation of diversity among fishes. Evolutionary changes associated with these transitions likely involve modifications of osmoregulatory function. In particular, relaxed selection on hypo-osmoregulation should strongly affect animals that transition into novel freshwater environments. We used populations of the Alewife ( Alosa pseudoharengus ) to study evolutionary shifts in hypo-osmoregulatory capacity and ion regulation associated with freshwater transitions. Alewives are ancestrally anadromous, but multiple populations in Connecticut have been independently restricted to freshwater lakes; these landlocked populations complete their entire life cycle in freshwater. Juvenile landlocked and anadromous Alewives were exposed to three salinities (1, 20 and 30 ppt) in small enclosures within the lake. We detected strong differentiation between life history forms: landlocked Alewives exhibited reduced seawater tolerance and hypo-osmoregulatory performance compared to anadromous Alewives. Furthermore, gill Na + /K + -ATPase activity and transcription of genes for seawater osmoregulation (NKCC—Na + /K + /2Cl − cotransporter and CFTR—cystic fibrosis transmembrane conductance regulator) exhibited reduced responsiveness to seawater challenge. Our study demonstrates that adaptations of marine-derived species to completely freshwater life cycles involve partial loss of seawater osmoregulatory performance mediated through changes to ion regulation in the gill.

Connecticut↗

USGS2020

High site fidelity does not equate to population genetic structure for common goldeneye and Barrow's goldeneye in North America

Delineation of population structure provides valuable information for conservation and management of species, as levels of demographic and genetic connectivity not only affect population dynamics but also have important implications for adaptability and resiliency of populations and species. Here, we measure population genetic structure and connectivity across the ranges of two sister species of sea ducks: Barrow's goldeneye Bucephala islandica and common goldeneye B. clangula . We use two different marker types: 7–8 nuclear microsatellite loci assayed across 229 samples and 3678 double digest restriction‐site associated DNA sequencing (ddRAD‐seq) loci assayed across 61 samples. First, both datasets found no evidence of genetic structure within common or Barrow's goldeneye, including between North American and European samples of common goldeneye. These results are in contrast with previous mitochondrial DNA, band recovery and telemetry data which suggest that goldeneyes are structured across their range. We posit that the discordance between autosomal genetic markers and other data types suggests that males, possibly subadult males, may be maintaining genetic connectivity across each species' respective ranges. Next, although mate choice consequences resulting from inter‐specific brood parasitism was hypothesized to cause some level of gene flow between goldeneye species, we only identified a single F1 hybrid with no further evidence of contemporary or historical gene flow. Despite ddRAD‐seq demographic analyses which recovered an optimum evolutionary model of split‐with‐migration (i.e. secondary contact), estimates of gene flow were <<1 migrant per generation in both directions. Together, we conclude that either strong ecological barriers or assortative mating are likely playing a role in preventing further backcrossing. Finally, demographic analyses estimated a relatively deep divergence time between Barrow's goldeneye and common goldeneye of ~1.6 million years before present and suggests that the genomes of both species have been under similar evolutionary constraints.

Journal of Avian Biology↗

USGS2022

Causes, responses, and implications of anthropogenic versus natural flow intermittence in river networks

Rivers that do not flow year-round are the predominant type of running waters on Earth. Despite a burgeoning literature on natural flow intermittence (NFI), knowledge about the hydrological causes and ecological effects of human-induced, anthropogenic flow intermittence (AFI) remains limited. NFI and AFI could generate contrasting hydrological and biological responses in rivers because of distinct underlying causes of drying and evolutionary adaptations of their biota. We first review the causes of AFI and show how different anthropogenic drivers alter the timing, frequency and duration of drying, compared with NFI. Second, we evaluate the possible differences in biodiversity responses, ecological functions, and ecosystem services between NFI and AFI. Last, we outline knowledge gaps and management needs related to AFI. Because of the distinct hydrologic characteristics and ecological impacts of AFI, ignoring the distinction between NFI and AFI could undermine management of intermittent rivers and ephemeral streams and exacerbate risks to the ecosystems and societies downstream.

BioScience↗

USGS2007

Development of the Hydroecological Integrity Assessment Process for Determining Environmental Flows for New Jersey Streams

The natural flow regime paradigm and parallel stream ecological concepts and theories have established the benefits of maintaining or restoring the full range of natural hydrologic variation for physiochemical processes, biodiversity, and the evolutionary potential of aquatic and riparian communities. A synthesis of recent advances in hydroecological research coupled with stream classification has resulted in a new process to determine environmental flows and assess hydrologic alteration. This process has national and international applicability. It allows classification of streams into hydrologic stream classes and identification of a set of non-redundant and ecologically relevant hydrologic indices for 10 critical sub-components of flow. Three computer programs have been developed for implementing the Hydroecological Integrity Assessment Process (HIP): (1) the Hydrologic Indices Tool (HIT), which calculates 171 ecologically relevant hydrologic indices on the basis of daily-flow and peak-flow stream-gage data; (2) the New Jersey Hydrologic Assessment Tool (NJHAT), which can be used to establish a hydrologic baseline period, provide options for setting baseline environmental-flow standards, and compare past and proposed streamflow alterations; and (3) the New Jersey Stream Classification Tool (NJSCT), designed for placing unclassified streams into pre-defined stream classes. Biological and multivariate response models including principal-component, cluster, and discriminant-function analyses aided in the development of software and implementation of the HIP for New Jersey. A pilot effort is currently underway by the New Jersey Department of Environmental Protection in which the HIP is being used to evaluate the effects of past and proposed surface-water use, ground-water extraction, and land-use changes on stream ecosystems while determining the most effective way to integrate the process into ongoing regulatory programs. Ultimately, this scientifically defensible process will help to quantify the effects of anthropogenic changes and development on hydrologic variability and help planners and resource managers balance current and future water requirements with ecological needs.

Scientific Investigations Report↗

USGS2023

Movement beyond the mean: decoupling sources of individual variation in brook trout movement across seasons

Movement is an important eco-evolutionary process that can shape population and ecosystem structure and function. Accordingly, a firm understanding of species movement ecology is often foundational to effective management and conservation. However, despite movement being an inherently individual-level behavior, there remains a tendency to describe dispersal and migration patterns using simple population-level processes and effects. Overlooking within- and among-individual variation in movement risks incomplete understanding of the intrinsic and extrinsic factors that govern dispersal dynamics and could potentially result in inadequate management of critical behavioral phenotypes. In this study, we monitored movement of over 100 brook trout ( Salvelinus fontinalis ) and quantified the effect of individual-level traits, season, and their interactions to better understand factors that influence vagility. Our results suggest that movement was higher in fall than in summer, particularly for fish in poor condition. But we found no significant main effects for sex, providing no evidence for sex-biased dispersal. To better understand sources of individual variation, we also allowed for sex- and season-specific residual standard deviations. In doing so, we found that, on average, movement was more variable in fall compared to summer, and that females were more variable than males in vagility. Taken together, these results demonstrate how intrinsic, individual-level traits can interact with abiotic environmental conditions to determine movement. They also highlight the potential for simple explanations of movement ecology to overlook important traits that may help predict individual-level behaviors.

Pennsylvania↗

USGS2024

Origin of the Laurentian Great Lakes fish fauna through upward adaptive radiation cascade prior to the Last Glacial Maximum

The evolutionary histories of adaptive radiations can be marked by dramatic demographic fluctuations. However, the demographic histories of ecologically-linked co-diversifying lineages remain understudied. The Laurentian Great Lakes provide a unique system of two such radiations that are dispersed across depth gradients with a predator-prey relationship. We show that the North American Coregonus species complex (“ciscoes”) radiated rapidly prior to the Last Glacial Maximum (80–90 kya), a globally warm period, followed by rapid expansion in population size. Similar patterns of demographic expansion were observed in the predator species, Lake Charr ( Salvelinus namaycush ), following a brief time lag, which we hypothesize was driven by predator-prey dynamics. Diversification of prey into deep water created ecological opportunities for the predators, facilitating their demographic expansion, which is consistent with an upward adaptive radiation cascade. This study provides a new timeline and environmental context for the origin of the Laurentian Great Lakes fish fauna, and firmly establishes this system as drivers of ecological diversification and rapid speciation through cyclical glaciation.

Communications Biology↗

USGS2005

Population structure of Columbia spotted frogs ( Rana luteiventris ) is strongly affected by the landscape

Landscape features such as mountains, rivers, and ecological gradients may strongly affect patterns of dispersal and gene flow among populations and thereby shape population dynamics and evolutionary trajectories. The landscape may have a particularly strong effect on patterns of dispersal and gene flow in amphibians because amphibians are thought to have poor dispersal abilities. We examined genetic variation at six microsatellite loci in Columbia spotted frogs ( Rana luteiventris ) from 28 breeding ponds in western Montana and Idaho, USA, in order to investigate the effects of landscape structure on patterns of gene flow. We were particularly interested in addressing three questions: (i) do ridges act as barriers to gene flow? (ii) is gene flow restricted between low and high elevation ponds? (iii) does a pond equal a 'randomly mating population' (a deme)? We found that mountain ridges and elevational differences were associated with increased genetic differentiation among sites, suggesting that gene flow is restricted by ridges and elevation in this species. We also found that populations of Columbia spotted frogs generally include more than a single pond except for very isolated ponds. There was also evidence for surprisingly high levels of gene flow among low elevation sites separated by large distances. Moreover, genetic variation within populations was strongly negatively correlated with elevation, suggesting effective population sizes are much smaller at high elevation than at low elevation. Our results show that landscape features have a profound effect on patterns of genetic variation in Columbia spotted frogs.

Idaho, Montana↗

USGS2013

Taming wildlife disease: bridging the gap between science and management

1.Parasites and pathogens of wildlife can threaten biodiversity, infect humans and domestic animals, and cause significant economic losses, providing incentives to manage wildlife diseases. Recent insights from disease ecology have helped transform our understanding of infectious disease dynamics and yielded new strategies to better manage wildlife diseases. Simultaneously, wildlife disease management (WDM) presents opportunities for large-scale empirical tests of disease ecology theory in diverse natural systems. 2.To assess whether the potential complementarity between WDM and disease ecology theory has been realized, we evaluate the extent to which specific concepts in disease ecology theory have been explicitly applied in peer-reviewed WDM literature. 3.While only half of WDM articles published in the past decade incorporated disease ecology theory, theory has been incorporated with increasing frequency over the past 40 years. Contrary to expectations, articles authored by academics were no more likely to apply disease ecology theory, but articles that explain unsuccessful management often do so in terms of theory. 4.Some theoretical concepts such as density-dependent transmission have been commonly applied, whereas emerging concepts such as pathogen evolutionary responses to management, biodiversity–disease relationships and within-host parasite interactions have not yet been fully integrated as management considerations. 5.Synthesis and applications. Theory-based disease management can meet the needs of both academics and managers by testing disease ecology theory and improving disease interventions. Theoretical concepts that have received limited attention to date in wildlife disease management could provide a basis for improving management and advancing disease ecology in the future.

Journal of Applied Ecology↗

USGS2013

Eco-evolutionary responses of Bromus tectorum to climate change: implications for biological invasions

How plant populations, communities, and ecosystems respond to climate change is a critical focus in ecology today. The responses of introduced species may be especially rapid. Current models that incorporate temperature and precipitation suggest that future Bromus tectorum invasion risk is low for the Colorado Plateau. With a field warming experiment at two sites in southeastern Utah, we tested this prediction over 4 years, measuring B. tectorum phenology, biomass, and reproduction. In a complimentary greenhouse study, we assessed whether changes in field B. tectorum biomass and reproductive output influence offspring performance. We found that following a wet winter and early spring, the timing of spring growth initiation, flowering, and summer senescence all advanced in warmed plots at both field sites and the shift in phenology was progressively larger with greater warming. Earlier green-up and development was associated with increases in B. tectorum biomass and reproductive output, likely due early spring growth, when soil moisture was not limiting, and a lengthened growing season. Seeds collected from plants grown in warmed plots had higher biomass and germination rates and lower mortality than seeds from ambient plots. However, in the following two dry years, we observed no differences in phenology between warmed and ambient plots. In addition, warming had a generally negative effect on B. tectorum biomass and reproduction in dry years and this negative effect was significant in the plots that received the highest warming treatment. In contrast to models that predict negative responses of B. tectorum to warmer climate on the Colorado Plateau, the effects of warming were more nuanced, relied on background climate, and differed between the two field sites. Our results highlight the importance of considering the interacting effects of temperature, precipitation, and site-specific characteristics such as soil texture, on plant demography and have direct implications for B. tectorum invasion dynamics on the Colorado Plateau.

Utah↗

USGS2025

Speciation genomics in the tiger whiptail lizards ( Aspidoscelis tigris complex)

The transition from small genetic to genome-scale datasets for studying biodiversity has revealed that genetic exchange through introgressive hybridization is a widespread phenomenon in nature. Despite this, a lack of high-quality reference genomes for most non-model species limits our understanding of the impact of this process for many taxonomic groups. This restricts the range of insights that genomic tools can provide for conservation biologists, who often hope to employ genomic datasets to accurately identify historically isolated lineages to protect and to predict their evolutionary fate in the face of environmental change. Tiger whiptail lizards ( Aspidoscelis tigris complex) are an abundant and important ecological component of ecosystems across the southwestern United States. In this study, we assembled and annotated a chromosome-level reference genome for A. t. stejnegeri from coastal California. We then used this reference genome to reconstruct patterns of speciation and admixture within the larger species complex, finding evidence that gene flow is widespread both geographically and across the genome.

northern Mexico, southwestern United States↗

USGS2016

Elevational speciation in action? Restricted gene flow associated with adaptive divergence across an altitudinal gradient

Evolutionary theory predicts that divergent selection pressures across elevational gradients could cause adaptive divergence and reproductive isolation in the process of ecological speciation. Although there is substantial evidence for adaptive divergence across elevation, there is less evidence that this restricts gene flow. Previous work in the boreal chorus frog (Pseudacris maculata) has demonstrated adaptive divergence in morphological, life history and physiological traits across an elevational gradient from approximately 1500–3000 m in the Colorado Front Range, USA. We tested whether this adaptive divergence is associated with restricted gene flow across elevation – as would be expected if incipient speciation were occurring – and, if so, whether behavioural isolation contributes to reproductive isolation. Our analysis of 12 microsatellite loci in 797 frogs from 53 populations revealed restricted gene flow across elevation, even after controlling for geographic distance and topography. Calls also varied significantly across elevation in dominant frequency, pulse number and pulse duration, which was partly, but not entirely, due to variation in body size and temperature across elevation. However, call variation did not result in strong behavioural isolation: in phonotaxis experiments, low-elevation females tended to prefer an average low-elevation call over a high-elevation call, and vice versa for high-elevation females, but this trend was not statistically significant. In summary, our results show that adaptive divergence across elevation restricts gene flow in P. maculata, but the mechanisms for this potential incipient speciation remain open.

Colorado↗

USGS2025

Evaluating the central–marginal hypothesis: Introgression and genetic variation at the trailing edge of Quercus bicolor

The central–marginal hypothesis (CMH) predicts reduced genetic diversity and increased differentiation in range-edge populations due to ecological marginality and limited gene flow. Deviations from this pattern, however, can result from historical demographic processes, variation in reproductive strategies or interspecific hybridization. The genus Quercus , known for hybridization and long-distance pollination, offers an excellent model to examine the spatial patterns of genetic diversity, structure and introgression across species distributions. Here, we investigate these dynamics in Quercus bicolor Willd., a widespread eastern North American oak. Using RADseq, we genotyped 142 individuals from 12 sites at the fragmented trailing range edge and nine sites from the range core. To detect introgression, we incorporated reference data from six sympatric white oak species. We reveal extensive introgression, particularly from Q. lyrata Walt., in nearly all southern edge populations, but none in core populations despite sympatry with closely related congeners. Southern populations also showed increased genetic structure and differentiation, but not reduced diversity or increased inbreeding, even when only examining non-admixed individuals. Regression analyses reveal relationships between introgressed ancestry and heterozygosity, inbreeding and differentiation, indicating that introgression may buffer range-edge populations against genetic erosion by introducing novel alleles. Hindcast, current and forecast ecological niche models demonstrate temporally changing degrees of overlap between the geographic range of Q. lyrata and Q. bicolor and suggest higher hybridization potential in the future. These findings offer mixed support for the CMH while underscoring the evolutionary relevance of introgression in shaping genetic landscapes at range margins with significant implications for conservation.

Molecular Ecology↗

USGS2003

Sexual selection affects local extinction and turnover in bird communities

Predicting extinction risks has become a central goal for conservation and evolutionary biologists interested in population and community dynamics. Several factors have been put forward to explain risks of extinction, including ecological and life history characteristics of individuals. For instance, factors that affect the balance between natality and mortality can have profound effects on population persistence. Sexual selection has been identified as one such factor. Populations under strong sexual selection experience a number of costs ranging from increased predation and parasitism to enhanced sensitivity to environmental and demographic stochasticity. These findings have led to the prediction that local extinction rates should be higher for species/populations with intense sexual selection. We tested this prediction by analyzing the dynamics of natural bird communities at a continental scale over a period of 21 years (1975-1996), using relevant statistical tools. In agreement with the theoretical prediction, we found that sexual selection increased risks of local extinction (dichromatic birds had on average a 23% higher local extinction rate than monochromatic species). However, despite higher local extinction probabilities, the number of dichromatic species did not decrease over the period considered in this study. This pattern was caused by higher local turnover rates of dichromatic species, resulting in relatively stable communities for both groups of species. Our results suggest that these communities function as metacommunities, with frequent local extinctions followed by colonization. Anthropogenic factors impeding dispersal might therefore have a significant impact on the global persistence of sexually selected species.

Proceedings of the National Academy of Sciences↗

USGS2016

Feline immunodeficiency virus cross-species transmission: Implications for emergence of new lentiviral infections

Owing to a complex history of host-parasite coevolution, lentiviruses exhibit a high degree of species specificity. Given the well-documented viral archeology of HIV emergence following human exposures to SIV, understanding processes that promote successful cross-species lentiviral transmissions is highly relevant. We have previously reported natural cross-species transmission of a subtype of feline immunodeficiency virus, puma lentivirus A (PLVA), between bobcats ( Lynx rufus ) and mountain lions ( Puma concolor ) in a small number of animals in California and Florida. In this study we investigate host-specific selection pressures, within-host viral fitness, and inter- vs. intra-species transmission patterns among a larger collection of PLV isolates from free-ranging bobcats and mountain lions. Analysis of proviral and viral RNA levels demonstrates that PLVA fitness is severely restricted in mountain lions compared to bobcats. We document evidence of diversifying selection in three of six PLVA genomes from mountain lions, but did not detect selection among twenty PLVA isolates from bobcats. These findings support that PLVA is a bobcat-adapted virus, which is less fit in mountain lions and under intense selection pressure in the novel host. Ancestral reconstruction of transmission events reveals intraspecific PLVA transmission has occurred among panthers ( Puma concolor coryi ) in Florida following initial cross-species infection from bobcats. In contrast, interspecific transmission from bobcats to mountain lions predominates in California. These findings document outcomes of cross-species lentiviral transmission events among felids that compare to emergence of HIV from nonhuman primates. IMPORTANCE Cross-species transmission episodes can be singular, dead-end events or can result in viral replication and spread in the new species. The factors that determine which outcome will occur are complex, and the risk of new virus emergence is therefore difficult to predict. Here we use molecular techniques to evaluate transmission, fitness, and adaptation of puma lentivirus A (PLVA) between bobcats and mountain lions in two geographic regions. Our findings illustrate that mountain lion exposure to PLVA is relatively common, but does not routinely result in infections communicable in the new host. This is attributed to efficient species barriers that largely prevent lentiviral adaptation. However, the evolutionary capacity for lentiviruses to adapt to novel environments may ultimately overcome host restriction mechanisms over time and under certain ecological circumstances. This phenomenon provides a unique opportunity to examine cross-species transmission events leading to new lentiviral emergence.

California, Florida↗

USGS2020

Shorebird reproductive response to exceptionally early and late springs varies across sites in Arctic Alaska

While increases in overall temperatures are widely reported in the Arctic, large inter-annual variation in spring weather, with extreme early and late conditions, is also occurring. Using data collected from three sites in Arctic Alaska, we explored how shorebird breeding density, nest initiation, nest synchrony, nest survival, and phenological mismatch varied between two exceptionally early (2015 and 2016) and late (2017 and 2018) springs. We assessed these differences in the context of long-term data from each site and whether species exhibited conservative or opportunistic reproductive strategies. Conservative shorebirds typically display nest-site fidelity and territoriality, consistent population densities, relatively even individual spacing, and monogamous mating systems with bi-parental incubation. In contrast, opportunistic shorebirds display the opposite traits, and a polygamous mating system with uniparental incubation. In this study, we evaluated 2,239 nests from 13 shorebird species, 2015–2018, and found that shorebirds of both strategies bred earlier and in higher numbers in early, warm springs relative to historic levels (based on 3,789 nests, 2005–2014); opposite trends were observed in late springs. In early springs, nests were initiated less synchronously than in late springs. Nest survival was unrelated to spring type, but was greater in earlier laid nests overall. Invertebrate food resources emerged earlier in early springs, resulting in a greater temporal asynchrony between invertebrate emergence and chick hatching in early than late springs. However, invertebrate abundance was quite variable among sites and years regardless of spring type. Overall, our results were generally consistent with predicted relationships between spring conditions and reproductive parameters. However, we detected differences among sites that could not be explained by other ecological factors (e.g., predators or alternative prey). Differences in shorebird community composition and other subtler methodological/ecological differences among sites highlight the difficulty of understanding the complex nature of these ecological systems and the importance of evaluating questions at multiple sites across multiple years. Our study demonstrates that shorebirds exhibit a high degree of behavioral flexibility in response to variable Arctic conditions, but whether this flexibility is enough to allow them to optimally track changing environmental conditions or if evolutionary adjustments will be necessary is unknown.

Alaska↗