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At least 847 records · Page 47Linked to original sources

USGS2011

Predicting breeding bird occurrence by stand- and microhabitat-scale features in even-aged stands in the Central Appalachians

Spatial scale is an important consideration when managing forest wildlife habitat, and models can be used to improve our understanding of these habitats at relevant scales. Our objectives were to determine whether stand- or microhabitat-scale variables better predicted bird metrics (diversity, species presence, and abundance) and to examine breeding bird response to clearcut size and age in a highly forested landscape. In 2004–2007, vegetation data were collected from 62 even-aged stands that were 3.6–34.6 ha in size and harvested in 1963–1990 on the Monongahela National Forest, WV, USA. In 2005–2007, we also surveyed birds at vegetation plots. We used classification and regression trees to model breeding bird habitat use with a suite of stand and microhabitat variables. Among stand variables, elevation, stand age, and stand size were most commonly retained as important variables in guild and species models. Among microhabitat variables, medium-sized tree density and tree species diversity most commonly predicted bird presence or abundance. Early successional and generalist bird presence, abundance, and diversity were better predicted by microhabitat variables than stand variables. Thus, more intensive field sampling may be required to predict habitat use for these species, and management may be needed at a finer scale. Conversely, stand-level variables had greater utility in predicting late-successional species occurrence and abundance; thus management decisions and modeling at this scale may be suitable in areas with a uniform landscape, such as our study area. Our study suggests that late-successional breeding bird diversity can be maximized long-term by including harvests >10 ha in size into our study area and by increasing tree diversity. Some harvesting will need to be incorporated regularly, because after 15 years, the study stands did not provide habitat for most early successional breeding specialists.

Forest Ecology and Management↗

USGS2012

Threshold effects of flood duration on the vegetation and soils of the Upper Mississippi River floodplain, USA

Most large rivers have experienced major changes in hydrology and land use over the past century, with concomitant effects on sedimentation, nutrient cycling and biodiversity. To restore and/or enhance these ecosystems, managers need to know where their efforts are most likely to succeed under current hydrologic regimes as well as under potential future hydrologic regimes. We therefore examined changes in forest vegetation and soils across a hydrologic gradient, expressed as flood duration during the growing season, for 320 km of the Upper Mississippi River (UMR) floodplain. Soil texture was highly variable but trended toward finer grained sediments and >5% organic matter as flood duration increased from 0% to ~40% of the growing season. Beyond 40%, soil texture was exclusively silt plus clay with >5% organic matter. The diversity of both the understory and overstory tree communities was also highly variable at sites that flooded for <40% of the growing season. However, understory diversity decreased as flood duration increased from 0% to ~25% of the growing season and overstory diversity declined as flood duration increased from 0% to ~40% of the growing season. Diversity estimates for both strata were uniformly low at sites that flooded for longer than ~40% of the growing season. Beyond this point the proportional abundance of Acer saccharinum in the overstory exceeded 70%. Our results suggest that there is a threshold along the elevation gradient of this floodplain, corresponding with flood durations lasting ~40% of the growing season. At lower elevation sites, flooding exerts primary control over forest soils and vegetation, restricting the former to silt plus clay with higher organic matter and the latter to a few highly flood tolerant species. The existence of such thresholds have implications for management of floodplain soil nutrient dynamics and plant diversity under existing hydrologic regimes, more natural hydrologic regimes and more extreme hydrologic regimes that may result from climate change.

Iowa;Minnesota;Wisconsin↗

USGS2024

Urbanization and water management control stream water quality along a mountain to plains transition

Urbanization can have substantial effects on water quality due to altered hydrology and introduction of constituents to water bodies. In arid and semi-arid environments, streams are further stressed by dewatering as a result of diversions. We conducted a high-resolution synoptic survey of two streams in Colorado, USA that transition abruptly from granitic/metamorphic forested mountains to sedimentary urbanized plains and are both highly managed for water supply, yet differ in degree of urbanization. A synoptic mass balance approach developed for mine drainage applications was adapted to elucidate effects of urbanization, geology, and diversions on stream chemistry during baseflow conditions. Urbanization was a more important driver of stream concentrations than geology. The urban area was a strong source of bromide, calcium, chloride, and manganese, while lanthanum and dissolved organic carbon were primarily sourced from the mountains. A majority of streamflow was removed by diversions near the mountains/plains interface. Groundwater accounted for 31% of the subsequent flow increase to the urbanized stream, and delivered at least 33% of chloride loading. Constituents that were primarily urban-derived (bromide, calcium, chloride, and manganese) were 2–3 times higher in the urban region due to diversions; without diversions, stream water quality would have largely retained characteristics of forested streams through the urban reach. This study provides insights into processes that affect water quality in highly managed streams of the semi-arid western USA.

Colorado↗

USGS2021

Trait-based filtering mediates the effects of realistic biodiversity losses on ecosystem functioning

Biodiversity losses are a major driver of global changes in ecosystem functioning. While most studies of the relationship between biodiversity and ecosystem functioning have examined randomized species losses, trait-based filtering associated with species-specific vulnerability to drivers of diversity loss can strongly influence how ecosystem functioning responds to declining biodiversity. Moreover, the responses of ecosystem functioning to diversity loss may be mediated by environmental variability interacting with the suite of traits remaining in depauperate communities. We do not yet understand how communities resulting from realistic diversity losses (filtered by response traits) influence ecosystem functioning (via effect traits of the remaining community), especially under variable environmental conditions. Here we directly test how realistic and randomized plant diversity losses influence productivity and invasion resistance across multiple years in a California grassland. Compared with communities based on randomized diversity losses, communities resulting from realistic (drought-driven) species losses had higher invasion resistance under climatic conditions that matched the trait-based filtering they experienced. However, productivity declined more with realistic than with randomized species losses across all years, regardless of climatic conditions. Functional response traits aligned with effect traits for productivity but not for invasion resistance. Our findings illustrate that the effects of biodiversity losses depend not only on the identities of lost species, but also on how the traits of remaining species interact with varying environmental conditions. Understanding the consequences of biodiversity change requires studies that evaluate trait-mediated effects of species losses and incorporate the increasingly variable climatic conditions that future communities are expected to experience.

Proceedings of the National Academy of Sciences↗

USGS2016

Revisiting Paine’s 1966 sea star removal experiment, the most-cited empirical article in the American Naturalist

“Food Web Complexity and Species Diversity” (Paine 1966) is the most-cited empirical article published in the American Naturalist . In short, Paine removed predatory sea stars ( Pisaster ochraceus ) from the rocky intertidal and watched the key prey species, mussels ( Mytilus californianus ), crowd out seven subordinate primary space-holding species. However, because these mussels are a foundational species, they provide three-dimensional habitat for over 300 associated species inhabiting the mussel beds; thus, removing sea stars significantly increases community-wide diversity. In any case, most ecologists cite Paine (1966) to support a statement that predators increase diversity by interfering with competition. Although detractors remained skeptical of top-down effects and keystone concepts, the paradigm that predation increases diversity spread. By 1991, “Food Web Complexity and Species Diversity” was considered a classic ecological paper, and after 50 years it continues to influence ecological theory and conservation biology.

American Naturalist↗

USGS2022

Aquatic vegetation dynamics in the Upper Mississippi River over 2 decades spanning vegetation recovery

Macrophytes have recovered in rivers across the world, but long-term data and studies are lacking regarding community assembly and diversity changes coincident with macrophyte recovery. We investigated patterns of aquatic vegetation species composition and diversity in thousands of sites in the Upper Mississippi River, USA, spanning 21 y of monitoring and a period of vegetation recovery. We analyzed site-level compositional dissimilarity and environmental associations using non-metric multidimensional scaling, compared stability of lake-level assemblages over time with convex hulls, and assessed shared trends in assemblage dissimilarity at the pool scale using dynamic factor analysis. Site-level differences in aquatic vegetation assemblage structure were associated with water depth and substrate, and a gradient of species abundance and diversity was apparent. A common trend in assemblage dissimilarity over time and across contiguous floodplain lakes indicate that assemblage composition changed and diversity increased with considerable synchrony within the past 21 y. Shared trends across the 400-km study reach are indicative of 1 or more widespread, common drivers; however, neither hydrologic extremes nor turbidity explained vegetation assemblage patterns. Following several years of strong changes in composition and increased diversity, the vegetation assemblage displayed signs of increasing stability in some pools but not others. Further research is needed to identify drivers and mechanisms of aquatic vegetation assemblage expansion, assembly, and resilience, all of which will be applicable to the recovery of aquatic vegetation in floodplain systems worldwide.

Illinois, Iowa, Minnesota, Wisconsin↗

USGS2022

Avian-associated Aspergillus fumigatus displays broad phylogenetic distribution, no evidence for host specificity, and multiple genotypes within epizootic events

Birds are highly susceptible to aspergillosis, which can manifest as a primary infection in both domestic and wild birds. Aspergillosis in wild birds causes mortalities ranging in scale from single animals to large-scale epizootic events. However, pathogenicity factors associated with aspergillosis in wild birds have not been examined. Specifically, it is unknown whether wild bird-infecting strains are host-adapted (i.e. phylogenetically related). Similarly, it is unknown whether epizootics are driven by contact with clonal strains that possess unique pathogenic or virulence properties, or by distinct and equally pathogenic strains. Here, we use a diverse collection of Aspergillus fumigatus isolates taken from aspergillosis-associated avian carcasses, representing 24 bird species from a wide geographic range, and representing individual bird mortalities as well as epizootic events. These isolates were sequenced and analyzed along with 130 phylogenetically diverse human clinical isolates to investigate the genetic diversity and phylogenetic placement of avian-associated A. fumigatus , the geographic and host distribution of avian isolates, evidence for clonal outbreaks among wild birds, and the frequency of azole resistance in avian isolates. We found that avian isolates were phylogenetically diverse, with no clear distinction from human clinical isolates, and no sign of host or geographic specificity. Avian isolates from the same epizootic events were diverse and phylogenetically distant, suggesting that avian aspergillosis is not contagious among wild birds and that outbreaks are likely driven by environmental spore loads or host comorbidities. Finally, all avian isolates were susceptible to Voriconazole and none contained the canonical azole resistance gene variants.

G3 Genes|Genomes|Genetics↗

USGS2017

Effects of host species and environment on the skin microbiome of Plethodontid salamanders

The amphibian skin microbiome is recognized for its role in defence against pathogens, including the deadly fungal pathogen Batrachochytrium dendrobatidis (Bd). Yet, we have little understanding of evolutionary and ecological processes that structure these communities, especially for salamanders and closely related species. We investigated patterns in the distribution of bacterial communities on Plethodon salamander skin across host species and environments. Quantifying salamander skin microbiome structure contributes to our understanding of how host-associated bacteria are distributed across the landscape, among host species, and their putative relationship with disease. We characterized skin microbiome structure (alpha-diversity, beta-diversity and bacterial operational taxonomic unit [OTU] abundances) using 16S rRNA gene sequencing for co-occurring Plethodon salamander species (35 Plethodon cinereus , 17 Plethodon glutinosus , 10 Plethodon cylindraceus ) at three localities to differentiate the effects of host species from environmental factors on the microbiome. We sampled the microbiome of P. cinereus along an elevational gradient ( n = 50, 700–1,000 m a.s.l.) at one locality to determine whether elevation predicts microbiome structure. Finally, we quantified prevalence and abundance of putatively anti-Bd bacteria to determine if Bd-inhibitory bacteria are dominant microbiome members. Co-occurring salamanders had similar microbiome structure, but among sites salamanders had dissimilar microbiome structure for beta-diversity and abundance of 28 bacterial OTUs. We found that alpha-diversity increased with elevation, beta-diversity and the abundance of 17 bacterial OTUs changed with elevation (16 OTUs decreasing, 1 OTU increasing). We detected 11 putatively anti-Bd bacterial OTUs that were present on 90% of salamanders and made up an average relative abundance of 83% ( SD ± 8.5) per salamander. All salamanders tested negative for Bd. We conclude that environment is more influential in shaping skin microbiome structure than host differences in these congeneric species, and suggest that environmental characteristics that covary with elevation influence microbiome structure. High prevalence and abundance of anti-Bd bacteria may contribute to low Bd levels in these populations of Plethodon salamanders.

Journal of Animal Ecology↗

USGS2018

Synchrony — An emergent property of recreational fisheries

Recreational fisheries are traditionally managed at local scales, but more effective management could be achieved using a cross‐scale approach. To do this, we must first understand how local processes scale up to influence landscape patterns between anglers and resources. We highlight how population‐based synchrony methods, used in conjunction with a complex‐adaptive‐systems framework, can reveal emergent spatial properties within social‐ecological systems such as recreational fisheries. Herein, we quantified the level of spatial synchrony in angler behaviour, defined the relationship between angler synchrony and distance among waterbodies, and highlighted social‐ecological attributes contributing to these patterns. We leveraged a 111 waterbody‐year (34 waterbodies, 5‐year collection period) recreational fisheries dataset from Nebraska, USA to address these objectives. Intra‐annual patterns in angler behaviour were moderately synchronous across large spatial scales and predominately unrelated to distance among waterbodies. Large‐scale synchronous patterns in angler behaviour emerged from local‐scale interactions between angler heterogeneity and waterbody diversity. Spatial synchrony in angler behaviour is an emergent property that resulted from local‐level processes that scaled up to form large‐scale patterns. We posit that angler utility in combination with waterbodies sharing these desired utility components caused spatial synchrony among anglers with similar preferences or specializations. The level of spatial synchrony in angler behaviour will therefore depend on the degree of angler heterogeneity and waterbody diversity on the landscape, with high or low levels of both leading to low and high levels of spatial synchrony respectively. Synthesis and applications. Synchrony‐based methods proved useful for unveiling an emergent property in recreational fisheries that is beneficial for effective cross‐scale management. It may not be appropriate to extrapolate information and apply uniform management actions among local waterbodies because angler behaviour was not synchronous at small scales. Rather, anglers respond uniquely to waterbody diversity and therefore substitute waterbodies may be dispersed throughout the landscape. Creating boat access, for example could yield unintended consequences for a particular angler group and cause local and regional shifts in angler behaviour. Evaluating appropriate management options will require a cross‐scale monitoring approach that captures angler heterogeneity and waterbody diversity at multiple scales. Recreational fisheries are traditionally managed at local scales, but more effective management could be achieved using a cross‐scale approach. To do this, we must first understand how local processes scale up to influence landscape patterns between anglers and resources. We highlight how population‐based synchrony methods, used in conjunction with a complex‐adaptive‐systems framework, can reveal emergent spatial properties within social‐ecological systems such as recreational fisheries. Herein, we quantified the level of spatial synchrony in angler behaviour, defined the relationship between angler synchrony and distance among waterbodies, and highlighted social‐ecological attributes contributing to these patterns. We leveraged a 111 waterbody‐year (34 waterbodies, 5‐year collection period) recreational fisheries dataset from Nebraska, USA to address these objectives. Intra‐annual patterns in angler behaviour were moderately synchronous across large spatial scales and predominately unrelated to distance among waterbodies. Large‐scale synchronous patterns in angler behaviour emerged from local‐scale interactions between angler heterogeneity and waterbody diversity. Spatial synchrony in angler behaviour is an emergent property that resulted from local‐level processes that scaled up to form large‐scale patterns. We posit that angler

Journal of Applied Ecology↗

USGS2023

Functional traits explain waterbirds’ host status, subtype richness, and community-level infection risk for avian influenza

Species functional traits can influence pathogen transmission processes, and consequently affect species' host status, pathogen diversity, and community-level infection risk. We here investigated, for 143 European waterbird species, effects of functional traits on host status and pathogen diversity (subtype richness) for avian influenza virus at species level. We then explored the association between functional diversity and HPAI H5Nx occurrence at the community level for 2016/17 and 2021/22 epidemics in Europe. We found that both host status and subtype richness were shaped by several traits, such as diet guild and dispersal ability, and that the community-weighted means of these traits were also correlated with community-level risk of H5Nx occurrence. Moreover, functional divergence was negatively associated with H5Nx occurrence, indicating that functional diversity can reduce infection risk. Our findings highlight the value of integrating trait-based ecology into the framework of diversity–disease relationship, and provide new insights for HPAI prediction and prevention.

Ecology Letters↗

USGS2004

Biodiversity and ecosystem functioning: Synthesis and perspectives

Does diversity matter in restored communities? This edited book explores the diversity–function debate, which has raged in ecology during the past several decades. The diversity–function question is relevant in restoration, but the question has not yet received a straightforward hearing in the field of restoration science. None of the authors of this book explicitly relate their ideas to restoration, but the book can educate restorationists about the most recent developments in the diversity–function debate. It is also an excellent book for students to learn about the recent developments and historical background of the diversity–function debate and can be used for graduate-level seminars in restoration or plant ecology.

Restoration Ecology↗

USGS2015

Genetic signatures of historical dispersal of fish threatened by biological invasions: the case of galaxiids in South America

Aim The ecological effects of biological invasions are well documented, but little is known about the effects of invaders on the genetic structure of native species. We examined the phylogeography, genetic variation and population structuring of two galaxiid fishes, Aplochiton zebra and A. taeniatus , threatened by non-native salmonids, and whose conservation is complicated by misidentification and limited knowledge of their genetic diversity. Location Chile and the Falkland Islands. Methods We combined microsatellite and mitochondrial DNA (16S rDNA and COI) markers to compare genetic diversity, effective population size and gene flow of Aplochiton spp. populations differentially affected by salmonid presence. Results We identified two 16S rDNA haplotypes among A. zebra – one dominant in coastal populations and another dominant in inland populations. Populations living on the island of Chiloé displayed a mixture of coastal and inland haplotypes, as well as high microsatellite diversity, as one would expect if the island had been a refugium during the Last Glacial Maximum, or a contact zone among populations. Microsatellite data revealed strong population structuring, indicative of current isolation patterns, and a negative correlation between the genetic diversity of A. zebra and the relative abundance of invasive salmonids. Main conclusions Our study indicates that population structuring of A. zebra reflects the influence of historical patterns of migration, but also the current levels of reduced gene flow among watersheds. Invasive salmonids, known to compete with and prey on native galaxiids, may have had negative impacts on the genetic diversity of Aplochiton spp. The low genetic variation found in some populations, coupled with potential biases in abundance estimates due to species misidentification, highlight the urgent need for more research into the conservation status of the two species of Aplochiton .

Journal of Biogeography↗

USGS2014

Influence of drift and admixture on population structure of American black bears ( Ursus americanus ) in the Central Interior Highlands, USA, 50 years after translocation

Bottlenecks, founder events, and genetic drift often result in decreased genetic diversity and increased population differentiation. These events may follow abundance declines due to natural or anthropogenic perturbations, where translocations may be an effective conservation strategy to increase population size. American black bears ( Ursus americanus ) were nearly extirpated from the Central Interior Highlands, USA by 1920. In an effort to restore bears, 254 individuals were translocated from Minnesota, USA, and Manitoba, Canada, into the Ouachita and Ozark Mountains from 1958 to 1968. Using 15 microsatellites and mitochondrial haplotypes, we observed contemporary genetic diversity and differentiation between the source and supplemented populations. We inferred four genetic clusters: Source, Ouachitas, Ozarks, and a cluster in Missouri where no individuals were translocated. Coalescent models using approximate Bayesian computation identified an admixture model as having the highest posterior probability (0.942) over models where the translocation was unsuccessful or acted as a founder event. Nuclear genetic diversity was highest in the source (A R = 9.11) and significantly lower in the translocated populations (A R = 7.07-7.34; P = 0.004). The Missouri cluster had the lowest genetic diversity (A R = 5.48) and served as a natural experiment showing the utility of translocations to increase genetic diversity following demographic bottlenecks. Differentiation was greater between the two admixed populations than either compared to the source, suggesting that genetic drift acted strongly over the eight generations since the translocation. The Ouachitas and Missouri were previously hypothesized to be remnant lineages. We observed a pretranslocation remnant signature in Missouri but not in the Ouachitas.

Molecular Ecology↗

USGS2025

Low genetic differentiation across restored and natural populations shortly after a large-scale, post-fire seeding in the Great Basin

Genetic diversity is essential for species to adapt to environmental changes. In restoration efforts, such as those after large wildfires in the sagebrush steppe of the Great Basin, commercially produced native seeds are used to revegetate the burned areas. While native seed certification and procurement protocols assure that genetically appropriate seeds are used for restoration, how post-fire seeding affects the genetic integrity of wildland populations at the landscape scale is unknown. To assess the effects of seeding on the genetic diversity of wildland populations, we conducted a genetic survey of Bluebunch wheatgrass ( Pseudoroegneria spicata [Pursh] Á.Löve ssp. Spicata ) populations within the perimeter of a recent megafire in southeastern Oregon and southwestern Idaho, United States. We genotyped 760 samples with 10 polymorphic loci. We found similar genetic diversity in populations four to 5 years after seeding compared to unseeded populations that were either burned or unburned. Furthermore, genetic diversity neither increased nor decreased with distance from the fire's edge, suggesting that wind dispersal from neighboring remnant populations plays a minor role in immediate post-fire recovery compared to resprouting and germination from the seed bank. Though no change was detected in the short term, this survey of genetic variation after a post-fire seeding provides an empirical baseline that can be used to track changes in genetic diversity of these wildland populations over time.

Idaho↗

USGS2017

Genetic composition and connectivity of the Antillean manatee (Trichechus manatus manatus) in Panama

Genetic diversity and haplotype composition of the West Indian manatee (Trichechus manatus) population from the San San Pond Sak wetland in Bocas del Toro, Panama was studied using a segment of mitochondrial DNA (D’loop). No genetic information has been published to date for Panamanian populations. Due to the secretive behavior and small population size of the species in the area, DNA extraction was conducted from opportunistically collected fecal (N=20), carcass tissue (N=4) and bone (N=4) samples. However, after DNA processing only 10 samples provided good quality DNA for sequencing (3 fecal, 4 tissue and 3 bone samples). We found three haplotypes in total; two of these haplotypes are reported for the first time, J02 (N=3) and J03 (N=4), and one J01 was previously published (N=3). Genetic diversity showed similar values to previous studies conducted in other Caribbean regions with moderate values of nucleotide diversity (π= 0.00152) and haplotipic diversity (Hd= 0.57). Connectivity assessment was based on sequence similarity, genetic distance and genetic differentiation between San San population and other manatee populations previously studied. The J01 haplotype found in the Panamanian population is shared with populations in the Caribbean mainland and the Gulf of Mexico showing a reduced differentiation corroborated with Fst value between HSSPS and this region of 0.0094. In contrast, comparisons between our sequences and populations in the Eastern Caribbean (South American populations) and North Western Caribbean showed fewer similarities (Fst =0.049 and 0.058, respectively). These results corroborate previous phylogeographic patterns already established for manatee populations and situate Panamanian populations into the Belize and Mexico cluster. In addition, these findings will be a baseline for future studies and comparisons with manatees in other areas of Panama and Central America. These results should be considered to inform management decisions regarding conservation of genetic diversity, future controlled introductions, connectivity and effective population size of the West Indian manatee along the Central American corridor.

Bocas del Toro↗

USGS1998

Forest floor bryophytes of Pseudotsuga menziesii-Tsuga heterophylla stand in Oregon: Influences of substrate and overstory

Species richness and abundance of bryophytes inhabiting forest floor substrates were assessed at two sites in western Oregon. Bryophyte diversity, abundance, and community composition were compared between sites, and between young forest stands (~55 yrs) and old-growth stands (400 + yrs) within each site. Relationships of stand structural features to diversity and community composition were assessed by stratifying sampling between "diversity" plots placed in areas of greater structural diversity, such as hardwood openings and remnant old-growth trees, and "matrix" plots situated within the remaining more homogeneous conifer-dominated forest matrix. Richness, particularly for liverworts, was significantly higher in old-growth than young stands, and the two ages differed significantly in community composition. Substrate (ground versus coarse woody debris) and overstory (conifers versus hardwoods) were most strongly correlated with variation in community composition. Relatively open hardwood-dominated diversity plots differed in composition from matrix plots. Bryophyte abundance was lower in denser stands and plots, and positively correlated with canopy gaps, percentage of hardwoods, and incident solar radiation. These results suggest that availability of light may limit bryophyte productivity in these stands.

Bryologist↗

USGS2009

Evaluation of Restoration Methods to Minimize Canada Thistle (Cirsium arvense) Infestation

The National Wildlife Refuge System has an active habitat restoration program and annually seeds thousands of hectares with native plant species. The noxious weed, Canada thistle (Cirsium arvense), plagues these restorations. This study evaluates planting methodology and seed mixes with the goal of recommending optimal methods to reduce infestation of noxious weeds, especially Canada thistle, in new restorations. Three planting methods (dormant season broadcast, growing season [summer] broadcast, and growing season [summer] drill) were fully crossed with three levels of seed diversity (10, 20, and 34 species [plus a fourth level, 58 species, on the three sites in Iowa]) in a completely randomized design replicated on nine sites in Minnesota and Iowa. The propagule bank of Canada thistle was evaluated at each site. Planting occurred in winter 2004 and spring-summer 2005. Here I report on results through summer 2007. None of the planting methods or seed mix diversities consistently resulted in reduced abundance of Canada thistle. Soil texture had the strongest influence; sites with greater proportions of clay had greater frequency and cover of Canada thistle than did sandy sites. At the Minnesota study sites, the dormant broadcast planting method combined with the highest seed diversity resulted in both the greatest cover of planted species as well as the greatest richness of planted species. At the Iowa sites, planted species richness was slightly greater in the summer drill plots, but cover of planted species was greatest in the dormant broadcast plots. Richness of planted species at the Iowa sites was maximized in the high diversity plots, with the extra-high diversity seed mix resulting in significantly lower species richness. Individual species responded to planting methods idiosyncratically, which suggests that particular species could be favored by tailoring planting methods to that species.

Open-File Report↗

USGS2018

Population genomic surveys for six rare plant species in San Diego County, California

San Diego County is a hotspot of biodiversity, situated at the intersection of the Baja peninsula, the California floristic province, and the desert southwest. This hotspot is characterized by a high number of rare and endemic species, which persist alongside a major urban epicenter. San Diego County has implemented a strategic management plan that identifies species, based on low numbers of occurrences or high level of threat, for which management practices are recommended. In creating a management plan for rare species, it is important to strike a balance between preserving locally adapted traits and maintaining genetic diversity, as species’ ranges fluctuate in response to a changing climate and habitat fragmentation. This project, in partnership with the San Diego Natural History Museum, aims to provide a reference point for the current status of genetic diversity of rare plant species that will inform future preservation and restoration efforts. We focused on six threatened or endangered plant species: Acanthomintha ilicifolia , Baccharis vanessae , Chloropyron maritimum ssp. maritimum , Deinandra conjugens , Dicranostegia orcuttiana , and Monardella viminea . For each species, botanists from the San Diego Natural History Museum visited all known occurrences in San Diego County and collected leaf tissue for genetic and cytological analysis. We then developed a panel of genetic markers to estimate genetic diversity and population structure. This population genetic survey provided insight into the amount of genetic differentiation across each species’ range, identified isolated occurrences potentially subject to inbreeding or genetic bottlenecks, and identified areas that are rich sources of allelic diversity. Finally, we convened a panel of experts to review results and compatible management options for each species. A summary of the management workshop is included in this report. Overall, we found low genetic differentiation among occurrences across the San Diego region for all species, with the exception of A. ilicifolia . Relative inbreeding was low and consistent across sites, and genetic diversity across sites was variable, with noted exceptions. These findings allow for a wide array of management options that are compatible with panmictic population structure in five of the six surveyed species.

California↗