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At least 937 records · Page 52Linked to original sources

USGS2016

Demographic mechanisms underpinning genetic assimilation of remnant groups of a large carnivore

Current range expansions of large terrestrial carnivores are occurring following human-induced range contraction. Contractions are often incomplete, leaving small remnant groups in refugia throughout the former range. Little is known about the underlying ecological and evolutionary processes that influence how remnant groups are affected during range expansion. We used data from a spatially explicit, long-term genetic sampling effort of grizzly bears ( Ursus arctos ) in the Northern Continental Divide Ecosystem (NCDE), USA, to identify the demographic processes underlying spatial and temporal patterns of genetic diversity. We conducted parentage analysis to evaluate how reproductive success and dispersal contribute to spatio-temporal patterns of genetic diversity in remnant groups of grizzly bears existing in the southwestern (SW), southeastern (SE) and east-central (EC) regions of the NCDE. A few reproductively dominant individuals and local inbreeding caused low genetic diversity in peripheral regions that may have persisted for multiple generations before eroding rapidly (approx. one generation) during population expansion. Our results highlight that individual-level genetic and reproductive dynamics play critical roles during genetic assimilation, and show that spatial patterns of genetic diversity on the leading edge of an expansion may result from historical demographic patterns that are highly ephemeral.

Northern Continental Divide Ecosystem↗

USGS2003

Phylogeography of infectious haematopoietic necrosis virus in North America

Infectious hematopoietic necrosis virus (IHNV) is a rhabdoviral pathogen that infects wild and cultured salmonid fish throughout the Pacific Northwest of North America. IHNV causes severe epidemics in young fish and can cause disease or occur asymptomatically in adults. In a broad survey of 323 IHNV field isolates, sequence analysis of a 303 nucleotide variable region within the glycoprotein gene revealed a maximum nucleotide diversity of 8·6 %, indicating low genetic diversity overall for this virus. Phylogenetic analysis revealed three major virus genogroups, designated U, M and L, which varied in topography and geographical range. Intragenogroup genetic diversity measures indicated that the M genogroup had three- to fourfold more diversity than the other genogroups and suggested relatively rapid evolution of the M genogroup and stasis within the U genogroup. We speculate that factors influencing IHNV evolution may have included ocean migration ranges of their salmonid host populations and anthropogenic effects associated with fish culture.

Journal of General Virology↗

USGS2018

Pulsed flows, tributary inputs, and food web structure in a highly regulated river

1.Dams disrupt the river continuum, altering hydrology, biodiversity, and energy flow. Although research indicates that tributary inputs have the potential to dilute these effects, knowledge at the food web level is still scarce. 2.Here we examined the riverine food web structure of the Colorado River below Glen Canyon Dam, focusing on organic matter sources, trophic diversity, and food chain length. We asked how these components respond to pulsed flows from tributaries following monsoon thunderstorms that seasonally increase streamflow in the American Southwest. 3.Tributaries increased the relative importance of terrestrial organic matter, particularly during the wet season below junctures of key tributaries. This contrasted with the algal-based food web present immediately below Glen Canyon Dam. 4.Tributary inputs during the monsoon also increased trophic diversity and food chain length: food chain length peaked below the confluence with the largest tributary (by discharge) in Grand Canyon, increasing by >1 trophic level over a 4-5 kilometre reach possibly due to aquatic prey being flushed into the mainstem during heavy rain events. 5.Our results illustrate that large tributaries can create seasonal discontinuities, influencing riverine food web structure in terms of allochthony, food web diversity, and food chain length. 6.Synthesis and applications. Pulsed flows from unregulated tributaries following seasonal monsoon rains increase the importance of terrestrially-derived organic matter in large, regulated river food webs, increasing food chain length and trophic diversity downstream of tributary inputs. Protecting unregulated tributaries within hydropower cascades may be important if we are to mitigate food web structure alteration due to flow regulation by large dams. This is critical in the light of global hydropower development, especially in megadiverse, developing countries where dam placement (including completed and planned structures) is in tributaries.

Colorado River↗

USGS2021

Genomic and environmental influences on resilience in a cold-water fish near the edge of its range

Small, isolated populations present a challenge for conservation. The dueling effects of selection and drift in a limited pool of genetic diversity make the responses of small populations to environmental perturbations erratic and difficult to predict. This is particularly true at the edge of a species range, where populations often persist at the limits of their environmental tolerances. Populations of cisco, Coregonus artedi , in inland lakes have experienced numerous extirpations along the southern edge of their range in recent decades, which are thought to result from environmental degradation and loss of cold, well-oxygenated habitat as lakes warm. Yet, cisco extirpations do not show a clear latitudinal pattern, suggesting that local environmental factors and potentially local adaptation may influence resilience. Here, we used genomic tools to investigate the nature of this pattern of resilience. We used restriction site-associated DNA capture (Rapture) sequencing to survey genomic diversity and differentiation in southern inland lake cisco populations and compared the frequency of deleterious mutations that potentially influence fitness across lakes. We also examined haplotype diversity in a region of the major histocompatibility complex involved in stress and immune system response. We correlated these metrics to spatial and environmental factors including latitude, lake size, and measures of oxythermal habitat and found significant relationships between genetic metrics and broad and local factors. High levels of genetic differentiation among populations were punctuated by a phylogeographic break and residual patterns of isolation-by-distance. Although the prevalence of deleterious mutations and inbreeding coefficients was significantly correlated with latitude, neutral and non-neutral genetic diversity were most strongly correlated with lake surface area. Notably, differences among lakes in the availability of estimated oxythermal habitat left no clear population genomic signature. Our results shed light on the complex dynamics influencing these isolated populations and provide valuable information for their conservation.

Wisconsin↗

USGS2005

Spartina alterniflora genotype influences facilitation and suppression of high marsh species colonizing an early successional salt marsh

Genetically based phenotypic and ecotypic variation in a dominant plant species can influence ecological functions and patterns of recruitment by other species in plant communities. However, the nature and degree of importance of genotypic differences is poorly understood in most systems. The dominant salt marsh species, Spartina alterniflora , is known to induce facilitative and competitive effects in different plant species, and the outcomes of interactions can be affected by nutrients and flooding stress. Clonal genotypes, which maintained their different plant architecture phenotypes throughout 31 months of a field experiment, underwent considerable genet‐specific senescence in their centres over the last 12 months. Different clonal genotypes and different locations (robust edges vs. senescent centres) permitted significantly different levels of light penetration of the canopy (14.8–77.6%), thus establishing spatial heterogeneity for this important environmental factor. S. alterniflora clonal genotype influenced the degree of suppression of the previously dominant Salicornia bigelovii as well as facilitation of recruitment and growth by other plant species. Aster subulatus and Atriplex patula performed better in Spartina clone centres, and experienced reduced growth in Salicornia ‐dominated areas. Four other high marsh species ( Borrichia frutescens , Aster tenuifolius , Iva frutescens and Limonium carolinianum ) colonized only into Spartina clones but not into the Salicornia ‐dominated area. These results suggest that differences in clone size, centre senescence, stem density, height, total stem length and biomass in different genotypes of a dominant marsh plant species can influence recruitment and growth of other plant species. The spatial pattern of habitat heterogeneity is, at least in part, dependent on the genotypic diversity, and possibly the genetic diversity, of such foundation species. We hypothesize that as genotypic diversity increases in populations of a dominant plant species like S. alterniflora , the number and diversity of interactions with other species will increase as well.

Journal of Ecology↗

USGS2005

Phylogeographic patterns of Hawaiian Megalagrion damselflies (Odonata: Coenagrionidae) correlate with Pleistocene island boundaries

The Pleistocene geological history of the Hawaiian Islands is becoming well understood. Numerous predictions about the influence of this history on the genetic diversity of Hawaiian organisms have been made, including the idea that changing sea levels would lead to the genetic differentiation of populations isolated on individual volcanoes during high sea stands. Here, we analyse DNA sequence data from two closely related, endemic Hawaiian damselfly species in order to test these predictions, and generate novel insights into the effects of Pleistocene glaciation and climate change on island organisms. Megalagrion xanthomelas and Megalagrion pacificum are currently restricted to five islands, including three islands of the Maui Nui super-island complex (Molokai, Lanai, and Maui) that were connected during periods of Pleistocene glaciation, and Hawaii island, which has never been subdivided. Maui Nui and Hawaii are effectively a controlled, natural experiment on the genetic effects of Pleistocene sea level change. We confirm well-defined morphological species boundaries using data from the nuclear EF-1?? gene and show that the species are reciprocally monophyletic. We perform phylogeographic analyses of 663 base pairs (bp) of cytochrome oxidase subunit II (COII) gene sequence data from 157 individuals representing 25 populations. Our results point to the importance of Pleistocene land bridges and historical island habitat availability in maintaining inter-island gene flow. We also propose that repeated bottlenecks on Maui Nui caused by sea level change and restricted habitat availability are likely responsible for low genetic diversity there. An island analogue to northern genetic purity and southern diversity is proposed, whereby islands with little suitable habitat exhibit genetic purity while islands with more exhibit genetic diversity. ?? 2005 Blackwell Publishing Ltd.

Molecular Ecology↗

USGS2012

Colonizing the world in spite of reduced MHC variation

Reduced immune gene diversity is thought to negatively affect the capacity of organisms to adapt to pathogen challenges, which represent a major force in natural selection. Genes of the Major Histocompatibility Complex (MHC) are the most widely invoked adaptive loci in conservation biology, and have become the most popular genetic markers to investigate pathogen-host interactions in vertebrates. Although MHC genes are the most polymorphic genes described in the vertebrate genome, the extent to which MHC diversity determines the long-term persistence of populations is, unclear and often debated, as recent studies have documented the occurrence of natural populations thriving even after a depletion of MHC diversity caused by genetic drift. Here, we show that some phylogenetically related species belonging to the Falco genus (Aves: Falconidae) present a dramatically low MHC variability that has not precluded, nevertheless, the successful colonization of almost all existing regions and habitats worldwide. We found evidence for two remarkably different patterns of MHC variation within the genus. While kestrels show a high MHC variation according to the general theory, falcons exhibit an ancestrally low intra- and inter-specific MHC allelic diversity. We provide compelling evidence that this pattern is not caused by the degeneration of functional genes into pseudogenes, the inadvertent analyses of paralogous MHC genes, or the devastating action of genetic drift. Instead, our results strongly support the idea of an evolutionary transition driven and maintained by natural selection from primarily highly variable towards low polymorphic, but functional and expressed, MHC genes with species-specific pathogen-recognition capabilities.

Journal of Evolutionary Biology↗

USGS2010

Low genetic variation and evidence of limited dispersal in the regionally important Belize manatee

The Antillean subspecies of the West Indian manatee Trichechus manatus is found throughout Central and South America and the Caribbean. Because of severe hunting pressure during the 17th through 19th centuries, only small populations of the once widespread aquatic mammal remain. Fortunately, protections in Belize reduced hunting in the 1930s and allowed the country's manatee population to become the largest breeding population in the Wider Caribbean. However, increasing and emerging anthropogenic threats such as coastal development, pollution, watercraft collision and net entanglement represent challenges to this ecologically important population. To inform conservation and management decisions, a comprehensive molecular investigation of the genetic diversity, relatedness and population structure of the Belize manatee population was conducted using mitochondrial and microsatellite DNA. Compared with other mammal populations, a low degree of genetic diversity was detected ( H E =0.455; N A =3.4), corresponding to the small population size and long-term exploitation. Manatees from the Belize City Cayes and Southern Lagoon system were genetically different, with microsatellite and mitochondrial F ST values of 0.029 and 0.078, respectively ( P ≤0.05). This, along with the distinct habitats and threats, indicates that separate protection of these two groups would best preserve the region's diversity. The Belize population and Florida subspecies appear to be unrelated with microsatellite and mitochondrial F ST values of 0.141 and 0.63, respectively ( P ≤0.001), supporting the subspecies designations and suggesting low vagility throughout the northern Caribbean habitat. Further monitoring and protection may allow an increase in the Belize manatee genetic diversity and population size. A large and expanding Belize population could potentially assist in the recovery of other threatened or functionally extinct Central American Antillean manatee populations.

Animal Conservation↗

USGS2005

Relationship between demographics and diet specificity of Imperial Eagles Aquila heliaca in Kazakhstan

The demographic consequences of within-population variability in predator foraging are not well understood. We assessed the relationship between the degree of diet specialization and two demographic parameters, population density and reproductive output, within a single population of Imperial Eagles Aquila heliaca at a nature reserve in north-central Kazakhstan. Nearest-neighbour distances between eagle nests throughout the reserve, and thus population density, were correlated with the degree to which diets were specialized. Diet diversity showed an extensive regional variability that was linked to prey distributions, but within-year analyses of reproductive output did not show similar linkages. However, multi-year analyses of breeding performance showed inter-regional differences in nesting success that were paralleled, and probably driven by, similar trends in diet diversity. In contrast, brood size at fledging was not linked to diet diversity and was more probably driven by reserve-wide influences such as weather. Finally, the decision to initiate breeding was associated neither with diet diversity nor with environmental variability. Our results indicate that the degree of dietary specialization is linked to the demographics of Imperial Eagle populations. For these and other raptor populations, it is possible that management could be used separately to increase or decrease nesting success, brood size at fledging, and the likelihood that a pair will initiate breeding.

Ibis↗

USGS2011

Hierarchical spatial structure of stream fish colonization and extinction

Spatial variation in extinction and colonization is expected to influence community composition over time. In stream fish communities, local species richness (alpha diversity) and species turnover (beta diversity) are thought to be regulated by high extinction rates in headwater streams and high colonization rates in downstream areas. We evaluated the spatiotemporal structure of fish communities in streams originally surveyed by Burton and Odum 1945 (Ecology 26: 182-194) in Virginia, USA and explored the effects of species traits on extinction and colonization dynamics. We documented dramatic changes in fish community structure at both the site and stream scales. Of the 34 fish species observed, 20 (59%) were present in both time periods, but 11 (32%) colonized the study area and three (9%) were extirpated over time. Within streams, alpha diversity increased in two of three streams but beta diversity decreased dramatically in all streams due to fish community homogenization caused by colonization of common species and extirpation of rare species. Among streams, however, fish communities differentiated over time. Regression trees indicated that reproductive life-history traits such as spawning mound construction, associations with mound-building species, and high fecundity were important predictors of species persistence or colonization. Conversely, native fishes not associated with mound-building exhibited the highest rates of extirpation from streams. Our results demonstrate that stream fish colonization and extinction dynamics exhibit hierarchical spatial structure and suggest that mound-building fishes serve as keystone species for colonization of headwater streams.

Oikos↗

USGS2021

Nuclear eDNA estimates population allele frequencies and abundance in experimental mesocosms

Advances in environmental DNA (eDNA) methodologies have led to improvements in the ability to detect species and communities in aquatic environments, yet the majority of studies emphasize biological diversity at the species level by targeting variable sites within the mitochondrial genome. Here, we demonstrate that eDNA approaches also have the capacity to detect intraspecific diversity in the nuclear genome, allowing for assessments of population-level genetic diversity and estimates of the number of genetic contributors in a sample. Using a panel of microsatellite loci, we evaluated intraspecific genetic diversity in the round goby (Neogobius melanostomus) using eDNA samples from experimental mesocosms. First, we tested the similarity between eDNA and individual tissue-based estimates of allele frequencies. Subsequently, we used a likelihood-based DNA mixture framework to estimate the number of unique genetic contributors in mesocosm eDNA samples and in simulated mixtures of alleles. Allele frequencies from eDNA accurately reflected allele frequencies from genotyped round goby tissue samples, indicating nuclear markers can be reliably amplified from water samples under controlled conditions. DNA mixture analyses were able to estimate the number of genetic contributors from eDNA samples and simulated mixtures of DNA from up to 58 individuals, with the degree of positive or negative bias dependent on the filtering scheme of low-frequency alleles. This study is the first to document the application of eDNA and multiple amplicon-based methods to obtain intraspecific nuclear genetic information and estimate the absolute abundance of a species in mesocosms. With proper validation, this approach has the potential to advance non-invasive survey methods to characterize populations and broadens the application of eDNA methodologies to inform population-level management objectives.

New York↗

USGS2023

Timing of reproduction underlies fitness tradeoffs for a salmonid fish

Life history diversity is generated and maintained in part by density-dependent fitness tradeoffs that inhibit a single trait value from reaching fixation. While central to our understanding of evolution, demonstrating density dependence in the strength of fitness tradeoffs is difficult in natural systems. The timing of reproduction is a key life history trait that determines access to breeding habitat and exposure of offspring to competitive interactions and environmental conditions. Understanding the processes underlying diversity in reproductive timing will aid efforts to increase adaptive capacity under global environmental change. Here, we used detailed field studies, genetic parentage assignment, and simulation modeling to evaluate the fitness tradeoffs associated with the timing of reproduction for Yellowstone cutthroat trout Oncorhynchus clarkii bouvieri in groundwater-dominated tributaries to the upper Snake River, Wyoming, USA. We conducted our study across two years to understand how the strength of tradeoffs changes with population density. We found that early breeders experienced reduced reproductive success relative to later breeders due to the negative impact of nest superimposition (where later breeders construct nests overlapping those constructed previously) on embryo survival. However, as the risk of superimposition declined in the low-density year and early breeders experienced fewer losses, reproductive success became more similar among individuals breeding at different times. Further, in the spring following the critical period for growth and survival, offspring of early breeders had experienced longer growing seasons, attained larger body sizes, and were equally abundant relative to those of later breeders, suggesting that fitness losses due to superimposition may be offset by size-dependent competitive ability and overwinter survival. Our results illustrate a mechanism underlying diversity in the timing of reproduction for salmonids. This type of life history diversity will help to ensure the resilience and stability of salmonid populations attempting to adapt to changing local stressors associated with global climate change.

Oikos↗

USGS2001

Genetic and morphologic variation in Phyllodoce empetriformis and Phyllodoce glanduliflora (Ericaceae) in Mount Rainier National Park, Washington

Genetic and morphological diversity of Phyllodoce empetriformis (Sw.) D. Don and Phyllodoce glanduliflora (hook.) Cov. were surveyed in Mount Rainier National Park in the Cascade Mountains of Washington State. Paired populations at high and low elevations were sampled at three study areas between 1720- and 2451-m elevation. Allozyme analysis of four polymorphic loci indicates high levels of genetic diversity within populations ( P. empetriformis = 94.2% and P. glanduliflora = 93.4% of total diversity) and significant differences in allele frequencies among populations and study areas. Individual populations are composed of multiple clones with high ratios of local to widespread genotypes. The proportion of distinguishable clones ranges from 32 to 83% within individual populations. Within individual populations, 18-67% of genotypes were restricted to one population. Patterns of morphologic variation, estimated through measurements of leaf width, leaf length, stem extension, and plant height paralleled those displayed by allozyme analysis. Significant differences were found in leaf width and stem length for P. empetriformis and among greenhouse populations for leaf width ( P. empetriformis ) and leaf length ( P. glanduliflora ). Species conservation strategies for Phyllodoce should concentrate on the maintenance of within-population levels of diversity, protection of adjacent populations, and protection of safe sites for recruitment of new populations.

Washington↗

USGS2020

An empirical comparison of population genetic analyses using microsatellite and SNP data for a species of conservation concern

Background Use of genomic tools to characterize wildlife populations has increased in recent years. In the past, genetic characterization has been accomplished with more traditional genetic tools (e.g., microsatellites). The explosion of genomic methods and the subsequent creation of large SNP datasets has led to the promise of increased precision in population genetic parameter estimates and identification of demographically and evolutionarily independent groups, as well as questions about the future usefulness of the more traditional genetic tools. At present, few empirical comparisons of population genetic parameters and clustering analyses performed with microsatellites and SNPs have been conducted. Results Here we used microsatellite and SNP data generated from Gunnison sage-grouse ( Centrocercus minimus ) samples to evaluate concordance of the results obtained from each dataset for common metrics of genetic diversity ( H O , H E , F IS , A R ) and differentiation ( F ST , G ST , D Jost ). Additionally, we evaluated clustering of individuals using putatively neutral (SNPs and microsatellites), putatively adaptive, and a combined dataset of putatively neutral and adaptive loci. We took particular interest in the conservation implications of any differences. Generally, we found high concordance between microsatellites and SNPs for H E , F IS , A R , and all differentiation estimates. Although there was strong correlation between metrics from SNPs and microsatellites, the magnitude of the diversity and differentiation metrics were quite different in some cases. Clustering analyses also showed similar patterns, though SNP data was able to cluster individuals into more distinct groups. Importantly, clustering analyses with SNP data suggest strong demographic independence among the six distinct populations of Gunnison sage-grouse with some indication of evolutionary independence in two or three populations; a finding that was not revealed by microsatellite data. Conclusion We demonstrate that SNPs have three main advantages over microsatellites: more precise estimates of population-level diversity, higher power to identify groups in clustering methods, and the ability to consider local adaptation. This study adds to a growing body of work comparing the use of SNPs and microsatellites to evaluate genetic diversity and differentiation for a species of conservation concern with relatively high population structure and using the most common method of obtaining SNP genotypes for non-model organisms.

Arizona, Colorado, New Mexico, Utah↗

USGS2021

Species and population specific gene expression in blood transcriptomes of marine turtles

Background Transcriptomic data has demonstrated utility to advance the study of physiological diversity and organisms’ responses to environmental stressors. However, a lack of genomic resources and challenges associated with collecting high-quality RNA can limit its application for many wild populations. Minimally invasive blood sampling combined with de novo transcriptomic approaches has great potential to alleviate these barriers. Here, we advance these goals for marine turtles by generating high quality de novo blood transcriptome assemblies to characterize functional diversity and compare global transcriptional profiles between tissues, species, and foraging aggregations. Results We generated high quality blood transcriptome assemblies for hawksbill ( Eretmochelys imbricata ) , loggerhead ( Caretta caretta ), green ( Chelonia mydas ), and leatherback ( Dermochelys coriacea ) turtles. The functional diversity in assembled blood transcriptomes was comparable to those from more traditionally sampled tissues. A total of 31.3% of orthogroups identified were present in all four species, representing a core set of conserved genes expressed in blood and shared across marine turtle species. We observed strong species-specific expression of these genes, as well as distinct transcriptomic profiles between green turtle foraging aggregations that inhabit areas of greater or lesser anthropogenic disturbance. Conclusions Obtaining global gene expression data through non-lethal, minimally invasive sampling can greatly expand the applications of RNA-sequencing in protected long-lived species such as marine turtles. The distinct differences in gene expression signatures between species and foraging aggregations provide insight into the functional genomics underlying the diversity in this ancient vertebrate lineage. The transcriptomic resources generated here can be used in further studies examining the evolutionary ecology and anthropogenic impacts on marine turtles.

BMC Genomics↗

USGS2009

The needs of salmon and steelhead in balancing their conservation and use

Over the past 100 years, Pacific salmon Oncorhynchus spp. and steelhead trout O. mykiss populations in the Pacific Northwest have experienced dramatic declines as a result of human population growth and associated development of the region's natural resources. Any strategy to reverse those declines will depend on achieving consensus among a diverse group of stakeholders willing to (1) restore damaged habitats and watersheds; (2) consider the biological needs of salmonid fishes; and (3) understand, conserve, and manage existing levels of biodiversity within an ecosystem context. The objective of this chapter is to review and summarize the needs of Pacific salmon and steelhead trout from perspectives that promote their sustainability and perpetuity, and, within that context, provide a framework, for the development of a sustainable fisheries strategy. Although volumes of information are available on the life histories and habitat requirements of Pacific salmonids, new concepts have begun to address the importance of habitat complexity, genetic diversity among locally adapted populations, and the need for appropriate units of conservation. Habitat variability and complexity are the templates that produce diverse, locally adapted populations of Pacific salmon and steelhead trout. Molded by conditions in the environments they colonized, salmon and steelhead have unique adaptations they may have taken hundred i?? perhaps thousands i?? of years to evolve. Any strategy to reverse the declines of salmon and steelhead must focus on conserving both current levels of genetic diversity as well as restoration and maintenance of habitats compatible with the specific needs of individual populations. An argument can be made that we know enough already about the needs of our salmon and steelhead to allow us to make appropriate decisions. There is strong need to integrate what we know about local salmonid adaptations and habitat needs with conservation and management strategies that address the problems we have created. It may be possible to have healthy, sustainable salmonid populations coastwide if we do not wait too long to make up our minds.

Book chapter↗

USGS2012

Molecular detection of hematozoa infections in tundra swans relative to migration patterns and ecological conditions at breeding grounds

Tundra swans ( Cygnus columbianus ) are broadly distributed in North America, use a wide variety of habitats, and exhibit diverse migration strategies. We investigated patterns of hematozoa infection in three populations of tundra swans that breed in Alaska using satellite tracking to infer host movement and molecular techniques to assess the prevalence and genetic diversity of parasites. We evaluated whether migratory patterns and environmental conditions at breeding areas explain the prevalence of blood parasites in migratory birds by contrasting the fit of competing models formulated in an occupancy modeling framework and calculating the detection probability of the top model using Akaike Information Criterion (AIC). We described genetic diversity of blood parasites in each population of swans by calculating the number of unique parasite haplotypes observed. Blood parasite infection was significantly different between populations of Alaska tundra swans, with the highest estimated prevalence occurring among birds occupying breeding areas with lower mean daily wind speeds and higher daily summer temperatures. Models including covariates of wind speed and temperature during summer months at breeding grounds better predicted hematozoa prevalence than those that included annual migration distance or duration. Genetic diversity of blood parasites in populations of tundra swans appeared to be relative to hematozoa prevalence. Our results suggest ecological conditions at breeding grounds may explain differences of hematozoa infection among populations of tundra swans that breed in Alaska.

Alaska↗

USGS2019

Morphology and genetics of Lythrum salicaria from latitudinal gradients of the Northern Hemisphere grown in cold and hot common gardens

The aim of this project was to compare the phenotypic responses of global populations of Lythrum salicaria in cold/dry and hot/humid environments to determine if phenotypic plasticity varied between the native and invasive ranges, and secondarily if this variation was linked to genetic diversity. Common garden studies were conducted in Třeboň, Czech Republic, and Lafayette, Louisiana, USA (cold/dry vs. hot/humid garden, respectively), using populations from latitudinal gradients in Eurasia and North America. Lythrum salicaria seeds collected from the same maternal plants across these latitudinal gradients were germinated and grown in Třeboň and Lafayette. Tissue masses (above-, below-ground, inflorescence and total) of these individuals were assessed at the end of each growing season (2006–2008). Worldwide field measurements of L . salicaria height were made by volunteers from 2004–2016. Biomass and height data were analyzed using the General Linear Model framework and multivariate techniques. Molecular markers (amplified fragment length polymorphisms) of individuals used in the common garden study were analyzed using traditional genetic diversity metrics and Bayesian clustering algorithms in STRUCTURE. Reaction norms were developed from differences in maternal plant responses in Třeboň versus Lafayette. In the common garden studies, stem/leaf, root and total biomass generally were highest for individuals grown from seeds collected in the southern part of the range in the cold garden, particularly by the third year of the study. In contrast, inflorescence biomass in the cold garden was higher by the third year in individuals from mid-latitude populations. As measured by volunteers, plants were taller in Eurasia than in North America moving from north to south with the pattern switching southward of 40°N latitude. Genetic diversity was similar between native and non-native invasive populations regardless of geographical origin of the seed and was not significantly different in the GLM Select model (p > 0.05). Reaction norm slopes showed that Eurasia had larger values than North America for reaction norms for above-ground and total biomass. Plants from the seeds of mother plants from Turkey had wide variation in total biomass when grown in Třeboň versus Lafayette; this variation in response within certain populations may have contributed to the lack of population-level differences in plasticity. These results indicate no loss of genetic diversity for L . salicaria during its North American invasion, nor reduction in plastic tissue allocation responses to a varying environment, which may help explain some of its invasive qualities and which could be of adaptive value under changing future environments.

PLoS ONE↗