USGS Science⌕ Search

SEARCH · USGS Science

Results for “Genes”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 469 records · Page 26Linked to original sources
USGS2013

Genetic diversity and mutation of avian paramyxovirus serotype 1 (Newcastle disease virus) in wild birds and evidence for intercontinental spread

Avian paramyxovirus serotype 1 (APMV-1), or Newcastle disease virus, is the causative agent of Newcastle disease, one of the most economically important diseases for poultry production worldwide and a cause of periodic epizootics in wild birds in North America. In this study, we examined the genetic diversity of APMV-1 isolated from migratory birds sampled in Alaska, Japan, and Russia and assessed the evidence for intercontinental virus spread using phylogenetic methods. Additionally, we predicted viral virulence using deduced amino acid residues for the fusion protein cleavage site and estimated mutation rates for the fusion gene of class I and class II migratory bird isolates. All 73 isolates sequenced as part of this study were most closely related to virus genotypes previously reported for wild birds; however, five class II genotype I isolates formed a monophyletic clade exhibiting previously unreported genetic diversity, which met criteria for the designation of a new sub-genotype. Phylogenetic analysis of wild-bird isolates provided evidence for intercontinental virus spread, specifically viral lineages of APMV-1 class II genotype I sub-genotypes Ib and Ic. This result supports migratory bird movement as a possible mechanism for the redistribution of APMV-1. None of the predicted deduced amino acid motifs for the fusion protein cleavage site of APMV-1 strains isolated from migratory birds in Alaska, Japan, and Russia were consistent with those of previously identified virulent viruses. These data therefore provide no support for these strains contributing to the emergence of avian pathogens. The estimated mutation rates for fusion genes of class I and class II wild-bird isolates were faster than those reported previously for non-virulent APMV-1 strains. Collectively, these findings provide new insight into the diversity, spread, and evolution of APMV-1 in wild birds.

Archives of Virology↗
USGS2012

Desulfohalophilus alkaliarsenatis gen. nov., sp. nov., an extremely halophilic sulfate- and arsenate-respiring bacterium from Searles Lake, California

A haloalkaliphilic sulfate-respiring bacterium, strain SLSR-1, was isolated from a lactate-fed stable enrichment culture originally obtained from the extreme environment of Searles Lake, California. The isolate proved capable of growth via sulfate-reduction over a broad range of salinities (125–330 g/L), although growth was slowest at salt-saturation. Strain SLSR-1 was also capable of growth via dissimilatory arsenate-reduction and displayed an even broader range of salinity tolerance (50–330 g/L) when grown under these conditions. Strain SLSR-1 could also grow via dissimilatory nitrate reduction to ammonia. Growth experiments in the presence of high borate concentrations indicated a greater sensitivity of sulfate-reduction than arsenate-respiration to this naturally abundant anion in Searles Lake. Strain SLSR-1 contained genes involved in both sulfate-reduction ( dsrAB ) and arsenate respiration ( arrA ). Amplicons of 16S rRNA gene sequences obtained from DNA extracted from Searles Lake sediment revealed the presence of close relatives of strain SLSR-1 as part of the flora of this ecosystem despite the fact that sulfate-reduction activity could not be detected in situ. We conclude that strain SLSR-1 can only achieve growth via arsenate-reduction under the current chemical conditions prevalent at Searles Lake. Strain SLSR-1 is a deltaproteobacterium in the family Desulfohalobiacea of anaerobic, haloalkaliphilic bacteria, for which we propose the name Desulfohalophilus alkaliarsenatis gen. nov., sp. nov.

California↗
USGS2007

Diversity, origins and virulence of Avipoxviruses in Hawaiian Forest Birds

We cultured avian pox (Avipoxvirus spp.) from lesions collected on Hawai'i, Maui, Moloka'i, and 'Oahu in the Hawaiian Islands from 15 native or non-native birds representing three avian orders. Phylogenetic analysis of a 538 bp fragment of the gene encoding the virus 4b core polypeptide revealed two distinct variant clusters, with sequences from chickens (fowlpox) forming a third distinct basal cluster. Pox isolates from one of these two clusters appear closely related to canarypox and other passerine pox viruses, while the second appears more specific to Hawai'i. There was no evidence that birds were infected simultaneously with multiple pox virus variants based on evaluation of multiples clones from four individuals. No obvious temporal or geographic associations were observed and strict host specificity was not apparent among the 4b-defined field isolates. We amplified a 116 bp 4b core protein gene fragment from an 'Elepaio (Chasiempis sandwichensis) collected in 1900 on Hawai'i Island that clustered closely with the second of the two variants, suggesting that this variant has been in Hawai'i for at least 100 years. The high variation detected between the three 4b clusters provides evidence for multiple, likely independent introductions, and does not support the hypothesis of infection of native species through introduction of infected fowl. Preliminary experimental infections in native Hawai'i 'Amakihi (Hemignathus virens) suggest that the 4b-defined variants may be biologically distinct, with one variant appearing more virulent. These pox viruses may interact with avian malaria (Plasmodium relictum), another introduced pathogen in Hawaiian forest bird populations, through modulation of host immune responses. ?? 2007 Springer Science+Business Media B.V.

Conservation Genetics↗
USGS2007

Population structure and genetic diversity of black redhorse (Moxostoma duquesnei) in a highly fragmented watershed

Dams have the potential to affect population size and connectivity, reduce genetic diversity, and increase genetic differences among isolated riverine fish populations. Previous research has reported adverse effects on the distribution and demographics of black redhorse (Moxostoma duquesnei), a threatened fish species in Canada. However, effects on genetic diversity and population structure are unknown. We used microsatellite DNA markers to assess the number of genetic populations in the Grand River (Ontario) and to test whether dams have resulted in a loss of genetic diversity and increased genetic differentiation among populations. Three hundred and seventy-seven individuals from eight Grand River sites were genotyped at eight microsatellite loci. Measures of genetic diversity were moderately high and not significantly different among populations; strong evidence of recent population bottlenecks was not detected. Pairwise FST and exact tests identified weak (global FST = 0.011) but statistically significant population structure, although little population structuring was detected using either genetic distances or an individual-based clustering method. Neither geographic distance nor the number of intervening dams were correlated with pairwise differences among populations. Tests for regional equilibrium indicate that Grand River populations were either in equilibrium between gene flow and genetic drift or that gene flow is more influential than drift. While studies on other species have identified strong dam-related effects on genetic diversity and population structure, this study suggests that barrier permeability, river fragment length and the ecological characteristics of affected species can counterbalance dam-related effects. ?? 2007 Springer Science+Business Media B.V.

Conservation Genetics↗
USGS2009

Conservation genetics of the alligator snapping turtle: cytonuclear evidence of range-wide bottleneck effects and unusually pronounced geographic structure

A previous mtDNA study indicated that female-mediated gene flow was extremely rare among alligator snapping turtle populations in different drainages of the Gulf of Mexico. In this study, we used variation at seven microsatellite DNA loci to assess the possibility of male-mediated gene flow, we augmented the mtDNA survey with additional sampling of the large Mississippi River System, and we evaluated the hypothesis that the consistently low within-population mtDNA diversity reflects past population bottlenecks. The results show that dispersal between drainages of the Gulf of Mexico is rare ( F ST msat = 0.43, Φ STmtDNA = 0.98). Past range-wide bottlenecks are indicated by several genetic signals, including low diversity for microsatellites (1.1–3.9 alleles/locus; H e = 0.06–0.53) and mtDNA ( h = 0.00 for most drainages; π = 0.000–0.001). Microsatellite data reinforce the conclusion from mtDNA that the Suwannee River population might eventually be recognized as a distinct taxonomic unit. It was the only population showing fixation or near fixation for otherwise rare microsatellite alleles. Six evolutionarily significant units are recommended on the basis of reciprocal mtDNA monophyly and high levels of microsatellite DNA divergence.

Gulf of Mexico↗
USGS2012

Identification of metapopulation dynamics among Northern Goshawks of the Alexander Archipelago, Alaska, and Coastal British Columbia

Northern Goshawks occupying the Alexander Archipelago, Alaska, and coastal British Columbia nest primarily in old-growth and mature forest, which results in spatial heterogeneity in the distribution of individuals across the landscape. We used microsatellite and mitochondrial data to infer genetic structure, gene flow, and fluctuations in population demography through evolutionary time. Patterns in the genetic signatures were used to assess predictions associated with the three population models: panmixia, metapopulation, and isolated populations. Population genetic structure was observed along with asymmetry in gene flow estimates that changed directionality at different temporal scales, consistent with metapopulation model predictions. Therefore, Northern Goshawk assemblages located in the Alexander Archipelago and coastal British Columbia interact through a metapopulation framework, though they may not fit the classic model of a metapopulation. Long-term population sources (coastal mainland British Columbia) and sinks (Revillagigedo and Vancouver islands) were identified. However, there was no trend through evolutionary time in the directionality of dispersal among the remaining assemblages, suggestive of a rescue-effect dynamic. Admiralty, Douglas, and Chichagof island complex appears to be an evolutionarily recent source population in the Alexander Archipelago. In addition, Kupreanof island complex and Kispiox Forest District populations have high dispersal rates to populations in close geographic proximity and potentially serve as local source populations. Metapopulation dynamics occurring in the Alexander Archipelago and coastal British Columbia by Northern Goshawks highlight the importance of both occupied and unoccupied habitats to long-term population persistence of goshawks in this region.

Alaska, British Columbia↗
USGS2012

Sample design effects in landscape genetics

An important research gap in landscape genetics is the impact of different field sampling designs on the ability to detect the effects of landscape pattern on gene flow. We evaluated how five different sampling regimes (random, linear, systematic, cluster, and single study site) affected the probability of correctly identifying the generating landscape process of population structure. Sampling regimes were chosen to represent a suite of designs common in field studies. We used genetic data generated from a spatially-explicit, individual-based program and simulated gene flow in a continuous population across a landscape with gradual spatial changes in resistance to movement. Additionally, we evaluated the sampling regimes using realistic and obtainable number of loci (10 and 20), number of alleles per locus (5 and 10), number of individuals sampled (10-300), and generational time after the landscape was introduced (20 and 400). For a simulated continuously distributed species, we found that random, linear, and systematic sampling regimes performed well with high sample sizes (>200), levels of polymorphism (10 alleles per locus), and number of molecular markers (20). The cluster and single study site sampling regimes were not able to correctly identify the generating process under any conditions and thus, are not advisable strategies for scenarios similar to our simulations. Our research emphasizes the importance of sampling data at ecologically appropriate spatial and temporal scales and suggests careful consideration for sampling near landscape components that are likely to most influence the genetic structure of the species. In addition, simulating sampling designs a priori could help guide filed data collection efforts.

Conservation Genetics↗
USGS2013

Interspecific hybridization contributes to high genetic diversity and apparent effective population size in an endemic population of mottled ducks (Anas fulvigula maculosa)

Under drift-mutation equilibrium, genetic diversity is expected to be correlated with effective population size (N e ). Changes in population size and gene flow are two important processes that can cause populations to deviate from this expected relationship. In this study, we used DNA sequences from six independent loci to examine the influence of these processes on standing genetic diversity in endemic mottled ducks ( Anas fulvigula ) and geographically widespread mallards ( A. platyrhynchos ), two species known to hybridize. Mottled ducks have an estimated census size that is about two orders-of-magnitude smaller than that of mallards, yet these two species have similar levels of genetic diversity, especially at nuclear DNA. Coalescent analyses suggest that a population expansion in the mallard at least partly explains this discrepancy, but the mottled duck harbors higher genetic diversity and apparent N e than expected for its census size even after accounting for a population decline. Incorporating gene flow into the model, however, reduced the estimated N e of mottled ducks to 33 % of the equilibrium N e and yielded an estimated N e consistent with census size. We also examined the utility of these loci to distinguish among mallards, mottled ducks, and their hybrids. Most putatively pure individuals were correctly assigned to species, but the power for detecting hybrids was low. Although hybridization with mallards potentially poses a conservation threat to mottled ducks by creating a risk of extinction by hybridization, introgression of mallard alleles has helped maintain high genetic diversity in mottled ducks and might be important for the adaptability and survival of this species.

Conservation Genetics↗
USGS2014

Regional differentiation among populations of the Diamondback terrapin ( Malaclemys terrapin )

The Diamondback terrapin (Malaclemys terrapin) is a brackish-water turtle species whose populations have been fragmented due to anthropogenic activity such as development of coastal habitat and entrapment in commercial blue crab (Callinectes sapidus) fishing gear. Genetic analyses can improve conservation efforts for the long-term protection of the species. We used microsatellite DNA analysis to investigate levels of gene flow among and genetic variability within 21 geographically separate collections of the species distributed from Massachusetts to Texas. Quantified levels of genetic variability (allelic diversity, genotypic frequencies, and heterozygosity) revealed three zones of genetic discontinuity, resulting in four discrete populations: Northeast Atlantic, Coastal Mid-Atlantic, Florida and Texas/Louisiana. The average number of alleles and expected heterozygosity for the four genetic clusters were N A = 6.54 and H E = 0.050, respectively. However, the geographic boundaries of the populations did not correspond to accepted terrapin subspecies limits. Our results illuminate not only the need to sample terrapins in additional sites, specifically in the southeast, but also the necessity for allowing uninterrupted gene flow among population groupings to preserve current levels of genetic diversity.

Conservation Genetics↗
USGS2016

Genetic structure and viability selection in the golden eagle (Aquila chrysaetos), a vagile raptor with a Holarctic distribution

Molecular markers can reveal interesting aspects of organismal ecology and evolution, especially when surveyed in rare or elusive species. Herein, we provide a preliminary assessment of golden eagle ( Aquila chrysaetos ) population structure in North America using novel single nucleotide polymorphisms (SNPs). These SNPs included one molecular sexing marker, two mitochondrial markers, 85 putatively neutral markers that were derived from noncoding regions within large intergenic intervals, and 74 putatively nonneutral markers found in or very near protein-coding genes. We genotyped 523 eagle samples at these 162 SNPs and quantified genotyping error rates and variability at each marker. Our samples corresponded to 344 individual golden eagles as assessed by unique multilocus genotypes. Observed heterozygosity of known adults was significantly higher than of chicks, as was the number of heterozygous loci, indicating that mean zygosity measured across all 159 autosomal markers was an indicator of fitness as it is associated with eagle survival to adulthood. Finally, we used chick samples of known provenance to test for population differentiation across portions of North America and found pronounced structure among geographic sampling sites. These data indicate that cryptic genetic population structure is likely widespread in the golden eagle gene pool, and that extensive field sampling and genotyping will be required to more clearly delineate management units within North America and elsewhere.

Conservation Genetics↗
USGS2018

Rare long-distance dispersal of the Island Night Lizard, Xantusia riversiana, maintains high diversity in a fragmented environment

The Island Night Lizard ( Xantusia riversiana ) is endemic to three of the Channel Islands off the coast of California, USA. Introduced species such as goats, sheep, and cats have profoundly affected the fauna and flora of the islands for over 150 years, but most of these non-native species have been recently removed. We measured the distribution of genetic diversity in Island Night Lizards across San Nicolas Island using DNA microsatellites to assess the impacts of historical habitat change on effective population size, gene flow, and population divergence; to provide baseline data for future monitoring of genetic diversity; and to provide recommendations to inform the restoration of degraded habitat. Despite a history of profound anthropogenic habitat disturbance, genetic diversity was high within sites, and there was no evidence of population bottlenecks. Divergence between sites was extraordinarily high, as expected for this sedentary species. Landscape resistance modeling using circuit theory showed that unsuitable habitat is relatively permeable to gene flow compared to suitable habitat, and yet populations separated by very short geographic distances remain genetically distinct. We found no evidence of a need for short-term intervention such as artificial translocations to maintain genetic diversity. Instead, we suggest that management should focus on maintaining, improving, and increasing habitat, especially in creating patches of habitat to link existing sites.

California↗
USGS2018

Genetic diversity, effective population size, and structure among black bear populations in the Lower Mississippi Alluvial Valley, USA

Multiple small populations of American black bears Ursus americanus , including the recently delisted Louisiana black bear subspecies U. a. luteolus , occupy a fragmented landscape in the Lower Mississippi Alluvial Valley, USA (LMAV). Populations include bears native to the LMAV, bears translocated from Minnesota during the 1960s, and recently reintroduced and colonizing populations sourced from within the LMAV. We estimated population structure, gene flow, and genetic parameters important to conservation of small populations using genotypes at 23 microsatellite markers for 265 bears from seven populations. We inferred five genetic clusters corresponding to the following populations: White River and western Mississippi, Tensas River and Three Rivers, Upper Atchafalaya, Lower Atchafalaya, and Minnesota. Upper Atchafalaya was suggested as the product of Minnesota-sourced translocations, but those populations have since diverged, likely because of a founder effect followed by genetic drift and isolation. An admixture zone recently developed in northeastern Louisiana and western Mississippi between migrants from White River and Tensas River, resulting in a Wahlund effect. However, gene flow among most populations has been limited and considerable genetic differentiation accumulated (global F ST = 0.22), particularly among the three Louisiana black bear populations that existed when federal listing occurred. Consistent with previous bottlenecks, founder effects, and persisting isolation, all LMAV bear populations had low genetic diversity ( A R = 2.08–4.81; H E = 0.36–0.63) or small effective population size ( N E = 3–49). Translocating bears among populations as part of a regional genetic restoration program may help improve genetic diversity and increase effective population sizes.

Lower Mississippi Alluvial Valley↗
USGS2026

Genetic structure in a previously extirpated population of gray wolves following reintroduction and natural recolonization

Genetic structuring in wildlife populations is driven by barriers that restrict gene flow as well as the history of population demography. Mechanisms driving genetic structuring can be nuanced in group-living species, such as gray wolves ( Canis lupus ). Behavioral factors, such as social affiliation and resistance, natal habitat imprinting, and trade-offs between dispersal from natal packs and territorial biding, affect habitat selection of wolves despite landscape barriers providing little resistance to their extensive dispersal capabilities. Wolves were previously extirpated from Idaho, USA, and current populations are the result of both reintroductions in 1995 and 1996 and natural dispersal from Canada. In this context we examined genetic structure of wolves in Idaho using 101 individuals genotyped at 18 nuclear DNA microsatellite loci and a subset of 38 individuals genotyped at 1019 single nucleotide polymorphism markers. We hypothesized panmictic (i.e., random mating) genetic structure in Idaho due to the long-distance dispersal abilities of gray wolves. Contrary to our hypothesis, we found three genetic clusters of gray wolves in Idaho, primarily supported by SNP markers. Microsatellite data suggested similar patterns, but permutation tests indicated these differences were not statistically significant. The extent of differentiation and evidence of gene flow, however, suggests that the three genetic clusters are not wholly isolated from one another. The distinctions between clusters spatially align with areas of reintroduction into central Idaho and Yellowstone National Park, as well ongoing natural recolonization from adjacent populations in Canada and Montana. Wolves at the periphery of analysis areas showed more admixture than those in the core, consistent with territoriality and mating behaviors contributing to genetic structuring. We demonstrate how management history, including reintroduction efforts, and animal behavior may interact and contribute to patterns of genetic structure in wild populations.

Idaho, Montana, Wyoming↗
USGS2022

A case study: Temporal trends of environmental stressors and reproductive health of smallmouth bass (Micropterus dolomieu) from a site in the Potomac River Watershed, Maryland, USA

Decades of poor reproductive success and young-of-the-year survival, combined with adult mortality events, have led to a decline in the smallmouth bass (SMB; Micropterus dolomieu ) population in sections of the Potomac River. Previous studies have identified numerous biologic and environmental stressors associated with negative effects on SMB health. To better understand the impact of these stressors, this study was conducted at the confluence of Antietam Creek and the Potomac River from 2013 to 2019 to identify temporal changes associated with SMB reproductive health. Surface water samples were collected and analyzed for over 300 organic contaminants, including pesticides, phytoestrogens, pharmaceuticals, hormones and total estrogenicity (E2Eq). Adult SMB were collected and sampled for multiple endpoints, including gene transcripts associated with reproduction (molecular), histopathology (cellular), and organosomatic indices (tissue). In males, biomarkers of estrogenic endocrine disruption, including testicular oocytes (TO) and plasma vitellogenin (Vtg) were assessed. Numerous agriculture-related contaminants or land use patterns were associated with gene transcript abundance in both male and female SMB. Positive associations between pesticides in the immediate catchment with TO severity and E2Eq with plasma Vtg in males were identified. In males, the prevalence of TO and detectable levels of plasma Vtg, liver vitellogenin transcripts ( vtg ) and testis vtg were high throughout the study. Peaks of complex mixtures of numerous contaminants occurred during the spring/early summer when spawning and early development occurs and to a lesser extent in fall/winter during recrudescence. Management practices to reduce exposure during these critical and sensitive periods may enhance reproductive health of these economically important sportfishes.

Maryland↗
USGS2021

Genetic structure and diversity of the mustard hill coral Porites astreoides along the Florida Keys reef tract

Increases in local and global stressors have led to major declines in coral populations throughout the western Atlantic. While abundances of other species have declined, however, the relative abundance of the mustard hill coral, Porites astreoides , has increased. Porites astreoides is relatively resilient to some stressors, and because of its mixed reproductive strategies, its populations often recover quickly following disturbances. The ability for P. astreoides to continue as a potential “winner” in western Atlantic reefs relies on maintaining sufficient genetic variation within populations to support acclimatization and adaptation to current and future environmental change. Without high genetic diversity and gene flow within the population, it would have limited capacity for adaptation and the species’ competitive advantages could be short-lived. In this study, we determined the genetic relatedness of 37 P. astreoides colonies at four shallow reefs along the offshore Florida Keys Reef Tract (FKRT), a region particularly hard-hit by recent disturbances. Using previously designed microsatellite markers, we determined the genetic diversity and connectivity of individuals among and between sites. Our results suggest that the FKRT likely contains a single, well-mixed genetic population of P. astreoides , with high levels of gene flow and evidence for larval migration throughout the region. This suggests that regional populations of P. astreoides likely have a higher chance of maintaining resilience than many other western Atlantic species as they face current and future disturbances.

Florida↗
USGS2018

A comparative evaluation of crowding stress on muscle HSP90 and myostatin expression in salmonids

Stress is a major factor that contributes to poor production and animal welfare concerns in aquaculture. As such, a thorough understanding of mechanisms involved in the stress response is imperative to developing strategies to mitigate the negative side effects of stressors, including the impact of high stocking densities on growth. The purpose of this study was to determine how the muscle growth inhibitor, myostatin , and the stress-responsive gene HSP90 are regulated in response to crowding stress in rainbow trout ( Oncorhynchus mykiss ), cutthroat trout ( Oncorhynchus clarki ), brook trout ( Salvelinus fontinalis ), and Atlantic salmon ( Salmo salar ). All species exhibited higher cortisol and glucose levels following the handling stress, indicating physiological response to the treatment. Additionally, all species, except rainbow trout, exhibited higher HSP90 levels in muscle after a 48 h crowding stress. Crowding stress resulted in a decrease of myostatin-1a in brook trout white muscle but not red muscle, while, myostatin-1a and -2a levels increased in white muscle and myostatin-1b levels increased in red muscle in Atlantic salmon. In rainbow trout, no significant changes were detected in either muscle type, but myostatin-1a was upregulated in both white and red skeletal muscle in the closely related cutthroat trout. The variation in response to crowding suggests a complex and species-specific interaction between stress and the muscle gene regulation in these salmonids. Only Atlantic salmon and cutthroat trout exhibited increased muscle myostatin transcription, and also exhibited the largest increase in circulating glucose in response to crowding. These results suggest that species-specific farming practices should be carefully examined in order to optimize low stress culture conditions.

Aquaculture↗
USGS2014

Comparative responses to endocrine disrupting compounds in early life stages of Atlantic salmon, Salmo salar

Atlantic salmon (Salmo salar) are endangered anadromous fish that may be exposed to feminizing endocrine disrupting compounds (EDCs) during early development, potentially altering physiological capacities, survival and fitness. To assess differential life stage sensitivity to common EDCs, we carried out short-term (four day) exposures using three doses each of 17α-ethinylestradiol (EE2), 17β-estradiol (E2), and nonylphenol (NP) on four early life stages; embryos, yolk-sac larvae, feeding fry and one year old smolts. Differential response was compared using vitellogenin (Vtg, a precursor egg protein) gene transcription. Smolts were also examined for impacts on plasma Vtg, cortisol, thyroid hormones (T4/T3) and hepatosomatic index (HSI). Compound-related mortality was not observed in any life stage, but Vtg mRNA was elevated in a dose-dependent manner in yolk-sac larvae, fry and smolts but not in embyos. The estrogens EE2 and E2 were consistently stronger inducers of Vtg than NP. Embryos responded significantly to the highest concentration of EE2 only, while older life stages responded to the highest doses of all three compounds, as well as intermediate doses of EE2 and E2. Maximal transcription was greater for fry among the three earliest life stages, suggesting fry may be the most responsive life stage in early development. Smolt plasma Vtg was also significantly increased, and this response was observed at lower doses of each compound than was detected by gene transcription suggesting this is a more sensitive indicator at this life stage. HSI was increased at the highest doses of EE2 and E2 and plasma T3 decreased at the highest dose of EE2. Our results indicate that all life stages after hatching are potentially sensitive to endocrine disruption by estrogenic compounds and that physiological responses were altered over a short window of exposure, indicating the potential for these compounds to impact fish in the wild.

Aquatic Toxicology↗
USGS2012

Genetic diversity of a newly established population of golden eagles on the Channel Islands, California

Gene flow can have profound effects on the genetic diversity of a founding population depending on the number and relationship among colonizers and the duration of the colonization event. Here we used data from nuclear microsatellite and mitochondrial DNA control region loci to assess genetic diversity in golden eagles of the recently colonized Channel Islands, California. Genetic diversity in the Channel Island population was low, similar to signatures observed for other recent colonizing island populations. Differences in levels of genetic diversity and structure observed between mainland California and the islands suggests that few individuals were involved in the initial founding event, and may have comprised a family group. The spatial genetic structure observed between Channel Island and mainland California golden eagle populations across marker types, and genetic signature of population decline observed for the Channel Island population, suggest a single or relatively quick colonization event. Polarity in gene flow estimates based on mtDNA confirm an initial colonization of the Channel Islands by mainland golden eagles, but estimates from microsatellite data suggest that golden eagles on the islands were dispersing more recently to the mainland, possibly after reaching the carrying capacity of the island system. These results illustrate the strength of founding events on the genetic diversity of a population, and confirm that changes to genetic diversity can occur within just a few generations.

California↗