Central Appalachian Mountains Research Articles

Northern Long-Eared Bat (Myotis septentrionalis) Day-Roost Loss in the Central Appalachian Mountains following Prescribed Burning

Before the arrival of white-nose syndrome in North America, the northern long-eared bat (Myotis septentrionalis) was a common cavity-roosting bat species in central Appalachian hardwood forests. Two successive prescribed burns on the Fernow Experimental Forest, West Virginia, in 2008 and 2009, were shown to positively affect maternity colony day-roost availability and condition in the near-term. However, whether immediate benefits were temporary and if burned forests actually experienced an accelerated loss of trees and snags possibly suitable for bats more than background loss in unburned forests became an important question following the species’ threatened designation. In 2016, we revisited 81 of 113 northern long-eared bat maternity colony day-roosts initially discovered in 2007–2009 with the objective of ascertaining if these trees and snags were still standing and thus potentially “available” for bat use. Initial tree or snag stage condition class and original year of discovery were contributory factors determining availability by 2016, whereas exposure to prescribed fire and tree/snag species decay resistance were not. Because forest managers may consider using habitat enhancement to improve northern long-eared bat survival, reproduction, and juvenile recruitment and must also protect documented day-roosts during forestry operations, we conclude that initial positive benefits from prescribed burning did not come at the expense of subsequent day-roost loss greater than background rates in these forests at least for the duration we examined.

Spatially variable syn- and post-Alleghanian exhumation of the central Appalachian Mountains from zircon (U-Th)/He thermochronology

Abstract To assess spatial and temporal patterns of Phanerozoic orogenic burial and subsequent exhumation in the central Appalachian Mountains, we present mid-temperature zircon (U-Th)/He (ZHe; closure temperature [TC] = 140–200 °C) dates for 10 samples along a 225 km, strike-perpendicular transect spanning the Appalachian Plateau, Valley and Ridge, Blue Ridge, and Piedmont physiographic provinces in West Virginia and western Virginia. Ranges of single-grain ZHe dates exhibit an eastward younging trend from 455–358 Ma in the Pennsylvanian Appalachian Plateau to 336–209 Ma in the Valley and Ridge, 298–217 Ma in the Blue Ridge, and 186–121 Ma in the Piedmont. Within the Pennsylvanian Appalachian Plateau, detrital ZHe dates are older than corresponding depositional ages, thus limiting postdepositional burial temperatures to less than 160 °C. These ZHe dates capture predepositional mid-Paleozoic cooling signatures, indicating provenance from either recycled Taconic or Acadian basin strata or mid-Paleozoic Appalachian terranes. Across the Valley and Ridge and western Blue Ridge provinces, reset Permian detrital ZHe dates feature flat date-effective uranium correlations that suggest rapid Alleghanian cooling initiating prior to 270 Ma. ZHe dates within the Valley and Ridge are more than 100 m.y. older than previously reported regional apatite fission-track dates, reflecting a protracted period of stable post-Alleghanian thermal conditions within the foreland. By contrast, post-Triassic single-grain ZHe dates in the interior Piedmont document rapid postrift cooling, likely resulting from both the relaxation of an elevated geothermal gradient and exhumation from rift-flank uplift. The spatial discontinuity between stable synrift thermal conditions in the Valley and Ridge and rapid cooling in the Piedmont suggests that rift-flank uplift and cooling were concentrated outboard of the foreland within the Piedmont province.

Pollinator communities vary with vegetation structure and time since management within regenerating timber harvests of the Central Appalachian Mountains

Native pollinator populations across the United States are increasingly threatened by a multitude of ecological stressors. Although the drivers behind pollinator population declines are varied, habitat loss/degradation remains one of the most important threats. Forested landscapes, where the impacts of habitat loss/degradation are minimized, are known to support robust pollinator populations in eastern North America. Within heavily forested landscapes, timber management is already implemented as a means for improving forest health and enhancing wildlife habitat, however, little is known regarding the characteristics within regenerating timber harvests that affect forest pollinator populations. In 2018 and 2019, we monitored insect pollinators in 143 regenerating (≤9 growing seasons post-harvest) timber harvest sites across Pennsylvania. During 1129 survey events, we observed over 9100 bees and butterflies, 220 blooming plant taxa, and collected over 2200 pollinator specimens. Bee and butterfly abundance were positively associated with season-wide floral abundance and negatively associated with dense vegetation that inhibits the growth of understory floral resources. Particularly in late summer, few pollinators were observed in stands >6 years post-harvest, with models predicting five times more bees in 1-year-old harvests than in 9-year-old harvests. Pollinator species diversity was positively associated with floral diversity and percent forb cover, and negatively associated with percent tall (>1 m) sapling cover. These results suggest that regenerating timber harvests promote abundant and diverse pollinator communities in the Appalachian Mountains, though pollinator abundance declined quickly as woody stems regenerated. Ultimately, our findings contribute to a growing body of literature suggesting that dynamic forest management producing a mix of age classes would benefit forest pollinator populations in the Central Appalachian Mountains.

Mycobiome sequencing and analysis of the assemblages of fungi associated with leaf litter on the Fernow Experimental Forest in the Central Appalachian Mountains of West Virginia

Mycobiome sequencing and analysis of the assemblages of fungi associated with leaf litter on the Fernow Experimental Forest in the Central Appalachian Mountains of West Virginia

Evaluating Models for Lithospheric Loss and Intraplate Volcanism Beneath the Central Appalachian Mountains

Evaluating Models for Lithospheric Loss and Intraplate Volcanism Beneath the Central Appalachian Mountains

Hotspot signatures at the North American passive margin

AbstractThe presence of localized low-velocity anomalies in the upper mantle beneath the passive Atlantic margin in North America is a puzzling geophysical observation. Whether the anomalies are caused by the remnant heat from past hotspots or ongoing asthenospheric upwelling is still debated. We addressed the formation of the anomalies based on a recent velocity model for eastern North America, which reveals new information on their shapes and anisotropic signatures. The low-velocity anomaly in New England appears as a narrow column above 90 km depth and broadens westward at depths of 120–200 km. Two slow anomalies are imaged under the central Appalachian Mountains between 140 km and 240 km. These low velocities correspond to pronounced positive radial anisotropy (Vsh > Vsv), indicating a dominantly horizontal asthenospheric flow. They also coincide with the tracks of the Great Meteor hotspot (140–115 Ma) and an inferred hidden hotspot (60–50 Ma). The anomalies in the central Appalachians could be due to lithospheric interaction with the second hotspot and subsequent lithospheric instabilities. The complex shape of the New England anomaly is consistent with interaction with both hotspots. The first hotspot could have eroded the base of the lithosphere, forming a channel, and the second hotspot could have further thinned the lithosphere and produced a localized cavity at shallow depths. Consequently, the indented lithosphere base would have filled with channelized asthenospheric flow or produced small-scale convection, helping to sustain the slow anomaly. Low-velocity anomalies at the North America passive margin are likely the consequences of prior hotspot interactions.

Bot Fly Parasitism of Allegheny Woodrats (Neotoma magister) in Virginia

The Allegheny woodrat (Neotoma magister) is a species of high conservation concern and relatively well-studied with respect to habitat use/associations, food habits, conservation genetics, and population trends. However, with the exception of raccoon roundworm (Baylisascaris procyonis) occurrence and etiology in woodrats, most disease and parasite ecology aspects for the woodrat are unknown. Herein, we examined the prevalence of bot flies (Cuterebra) over nearly three decades of woodrat surveys (1990–2018) in the central Appalachian Mountains of western Virginia. We use genetic analyses to identify recent bot fly specimen collections from a woodrat captured in 2017. Though highly variable from year to year, the overall prevalence of parasitism was low (typically < 4% of captures). As such, bot flies do not appear to be a widespread parasitic burden to Allegheny woodrats in Virginia. Genetic analysis of four collected bot fly larvae was inconclusive, as the genetic signature of these woodrat bots did not match any of the six bot species known to parasitize rodents and lagomorphs in the eastern United States. Further collections and genetic analyses will be needed to determine if the genetic database is incomplete or incorrect, or if our find is a new species of bot fly not yet taxonomically recognized.

Resolving host and species boundaries for perithecia-producing nectriaceous fungi across the central Appalachian Mountains

Abstract The Nectriaceae includes numerous canker pathogens. Due to the scarcity of ascomata on many hosts, comprehensive surveys are lacking. Here we characterize the diversity of perithecia-producing nectriaceous fungi across the central Appalachians in eastern North America. Nine species from eleven hosts were recovered including a novel Corinectria sp. from Picea rubens. Neonectria ditissima and Neonectria faginata were most abundant and associated with Fagus grandifolia with beech bark disease (BBD). Neonectria ditissima was also recovered from additional cankered hardwoods, including previously unreported Acer spicatum, Ilex mucronata, and Sorbus americana. Cross-pathogenicity inoculations of N. ditissima confirmed susceptibility of Acer and Betula spp. Neonectria magnoliae was recovered from cankered Liriodendron tulipifera and Magnolia fraseri and pathogenicity on L. tulipifera was confirmed. Fusarium babinda was consistently recovered from beech with BBD, although its role remains unclear. This survey provides a contemporary snapshot of Nectriaceae diversity across the Appalachian Mountains. The following nomenclatural changes are proposed: Neonectria magnoliae comb. nov.

Sex-specific effects of reproductive season on bobcat space use, movement, and resource selection in the Appalachian Mountains of Virginia.

Across taxa, sex-specific demands vary temporally in accordance with reproductive investments. In solitary carnivores, females must provision and protect young independently while meeting increased energetic demands. Males seek to monopolize access to females by maintaining large territories and defending them from other males. For many species, it is poorly understood how these demands relate to broad-scale animal movements. To investigate predictions surrounding the reproductive strategies of solitary carnivores and effects of local conditions on bobcat (Lynx rufus) spatial ecology, we examined the effects of sex and reproductive season on home range size, movement rate, and resource selection of bobcats in the central Appalachian Mountains. Male seasonal home ranges were approximately 3 times larger than those of females (33.9 ± 2.6 vs. 12.1 ± 2.4 km2, x±SE), and male movement rates were 1.4 times greater than females (212.6 ± 3.6 vs. 155 ± 8.2 m/hr), likely reflecting male efforts to maximize access to females. Both sexes appear to maintain relatively stable seasonal home ranges despite temporally varying reproductive investments, instead adjusting movements within home ranges. Males increased movements during the dispersal period, potentially reflecting increased territoriality prior to breeding. Females increased movements during the kitten-rearing period, when foraging more intensively, and frequently returning to den sites. Both sexes selected home ranges at higher elevations. However, females selected deciduous forest and avoided fields, whereas males selected fields and avoided deciduous forest, perhaps explained by male pressure to access multiple females across several mountain ridges and higher risk tolerance. Seasonal changes in home range selection likely reflect changes in home range shape. Increased female avoidance of fields during kitten rearing may indicate female avoidance of presumably resource rich, yet risky, fields at the time when kittens are most vulnerable. Our results indicate that while reproductive chronology influences the spatial ecology of solitary carnivores, effects may be constrained by territoriality.

Bot Fly Parasitism of Allegheny Woodrats (Neotoma magister) in Virginia

The Allegheny woodrat (Neotoma magister) is a species of high conservation concern and relatively well-studied with respect to habitat use/associations, food habits, conservation genetics, and population trends. However, with the exception of raccoon roundworm (Baylisascaris procyonis) occurrence and etiology in woodrats, most disease and parasite ecology aspects for the woodrat are unknown. Herein, we examined the prevalence of bot flies (Cuterebra) over nearly three decades of woodrat surveys (1990–2018) in the central Appalachian Mountains of western Virginia. We use genetic analyses to identify recent bot fly specimen collections from a woodrat captured in 2017. Though highly variable from year to year, the overall prevalence of parasitism was low (typically < 4% of captures). As such, bot flies do not appear to be a widespread parasitic burden to Allegheny woodrats in Virginia. Genetic analysis of four collected bot fly larvae was inconclusive, as the genetic signature of these woodrat bots did not match any of the six bot species known to parasitize rodents and lagomorphs in the eastern United States. Further collections and genetic analyses will be needed to determine if the genetic database is incomplete or incorrect, or if our find is a new species of bot fly not yet taxonomically recognized.

A revision of Hypotrachyna subgenus Parmelinopsis (Parmeliaceae) in eastern North America

A taxonomic revision of Hypotrachyna subgenus Parmelinopsis in eastern North America is presented based on molecular phylogenetic analyses of ITS and mtSSU data, extensive field observation and analyses of chemical and morphological data. Each species is described, illustrated with photographs, and the distribution in the region is mapped. An identification key is also presented. Eleven species are recognized: H. afrorevoluta, H. appalachensis, H. britannica, H. cryptochlora, H. horrescens, H. kauffmaniana, H. minarum, H. mcmulliniana, H. revoluta, H. showmanii and H. spumosa. Extensive discussion of prior studies is provided, particularly with respect to the delimitation of H. afrorevoluta and H. revoluta. Hypotrachyna kauffmaniana is described from the central and southern Appalachian Mountains and separated from H. afrorevoluta and H. revoluta by its ascending secondary lobes and pustulose soralia that are primarily confined to the secondary lobes. Hypotrachyna horrescens is shown to correspond to a taxon with narrow lobed, small thalli with ciliate isidia. Hypotrachyna mcmulliniana is described from material collected throughout southeastern North America that is chemically identical to H. horrescens but differs in having larger thalli and sparsely ciliate isidia. Hypotrachyna appalachensis is described to accommodate material previously referred to H. minarum but that differs in the production of 4,5-di-O-methylhiascic acid in high concentrations (vs. absent or present as a trace in H. minarum). Hypotrachyna britannica is reported for the first time from North America.

Radiocarbon dating peatland development: Key steps in reconstructing past climate in the central Appalachian Mountains

Canaan Valley in West Virginia contains a greater area of peatlands than any other locality in the mid-Atlantic Highlands. Extensive fieldwork focused on peat stratigraphy, combined with high-resolution radiocarbon dating, was used to evaluate five peatlands within Canaan Valley National Wildlife Refuge (CVNWR). One hundred soil cores were profiled and described, 30 with laboratory analysis, including 52 radiocarbon dates. Calibrated basal peat dates from the five peatlands indicate the onset of peat genesis ranged from ∼18,600 to ∼15,200 cal yr BP. Basal peat dates on the two oldest cores are 1800 to 2200 years older than published dates on peat initiation in any other Appalachian Mountain peatlands. Peat accumulation rates varied from 0.02 mm/yr to 1.34 mm/yr, with a mean of 0.14 mm/yr. Results of age-depth profiles for six well-dated cores consistently exhibit: rapid accumulation during the late Pleistocene (Heinrich Stadial 1, Bølling-Allerød interstadial, and Younger Dryas cold stadial), lower accumulation rates in the early Holocene (Greenlandian Age), even lower accumulation rates during the mid-Holocene (Northgrippian Age), and the most rapid peat accumulation at the onset of the late Holocene (early Meghalayan Age). A paucity of shallow peat dating younger than 2000 BP may reflect a reduction in peat accumulation, or mixing of surface vegetation into near-surface soil horizons. Soil cores from CVNWR suggest a somewhat different peat development history than the process of terrestrialization previously proposed for other peatland ecosystems in the region.

The MAGIC Experiment: A Combined Seismic and Magnetotelluric Deployment to Investigate the Structure, Dynamics, and Evolution of the Central Appalachians

Abstract The eastern margin of North America has undergone multiple episodes of orogenesis and rifting, yielding the surface geology and topography visible today. It is poorly known how the crust and mantle lithosphere have responded to these tectonic forces, and how geologic units preserved at the surface related to deeper structures. The eastern North American margin has undergone significant postrift evolution since the breakup of Pangea, as evidenced by the presence of young (Eocene) volcanic rocks in western Virginia and eastern West Virginia and by the apparently recent rejuvenation of Appalachian topography. The drivers of this postrift evolution, and the precise mechanisms through which relatively recent processes have modified the structure of the margin, remain poorly understood. The Mid-Atlantic Geophysical Integrative Collaboration (MAGIC) experiment, part of the EarthScope USArray Flexible Array, consisted of collocated, dense, linear arrays of broadband seismic and magnetotelluric (MT) stations (25–28 instruments of each type) across the central Appalachian Mountains, through the U.S. states of Virginia, West Virginia, and Ohio. The goals of the MAGIC deployment were to characterize the seismic and electrical conductivity structure of the crust and upper mantle beneath the central Appalachians using natural-source seismic and MT imaging methods. The MAGIC stations operated between 2013 and 2016, and the data are publicly available via the Incorporated Research Institutions for Seismology Data Management Center.

Influence of forest disturbance on bobcat resource selection in the central Appalachians

Similar to trends across the eastern United States, the central Appalachian Mountains were nearly entirely deforested by the early 20th century, then regenerated with a drastically altered disturbance regime. Forests found across much of the region today share little resemblance to the forest communities in which native wildlife evolved, including bobcats (Lynx rufus), a species adapted to stalking and ambushing prey in dense concealment cover. Managers implement efforts to restore historical forest structure and create wildlife habitat using prescribed fire, timber harvest, and maintained clearings. We developed resource selection functions utilizing GPS telemetry data from 9 bobcats (6 male, 3 female) monitored in 2018–2019 to investigate how prescribed fire, timber harvest, and forest edge may influence 3rd order (i.e. within home range) resource selection of bobcats in the Appalachian Mountains of western Virginia, USA. We found that bobcats selected for forest-edge, fire-created canopy openings, and recently harvested forest stands, and avoided the forest interior. Bobcats are likely selecting for these areas because of increased prey and cover. The comparatively widespread use of fire in this study area has allowed novel insight into the effects of prescribed fire on bobcat space use and demonstrates the ecological importance of future efforts to restore historical fire cycles in the Appalachians. As one of the largest carnivores in Appalachian ecosystems and the only wild felid remaining in the region, we suggest managers consider bobcat ecology when planning habitat management strategies and communicate those strategies to the public. Our results demonstrate that silvicultural practices that aim to mimic historical forest disturbance likely benefit native wildlife, as evident from selection of these treatments by bobcats in this system.

Twenty-First Century Streamflow and Climate Change in Forest Catchments of the Central Appalachian Mountains Region, US

Forested catchments are critical sources of freshwater used by society, but anthropogenic climate change can alter the amount of precipitation partitioned into streamflow and evapotranspiration, threatening their role as reliable fresh water sources. One such region in the eastern US is the heavily forested central Appalachian Mountains region that provides fresh water to local and downstream metropolitan areas. Despite the hydrological importance of this region, the sensitivity of forested catchments to climate change and the implications for long-term water balance partitioning are largely unknown. We used long-term historic (1950–2004) and future (2005–2099) ensemble climate and water balance data and a simple energy–water balance model to quantify streamflow sensitivity and project future streamflow changes for 29 forested catchments under two future Relative Concentration Pathways. We found that streamflow is expected to increase under the low-emission pathway and decrease under the high-emission pathway. Furthermore, despite the greater sensitivity of streamflow to precipitation, larger increases in atmospheric demand offset increases in precipitation-induced streamflow, resulting in moderate changes in long-term water availability in the future. Catchment-scale results are summarized across basins and the region to provide water managers and decision makers with information about climate change at scales relevant to decision making.

Do historic log buildings provide evidence of reforestation following depopulation of Indigenous Peoples?

AbstractAimTo test the previously published hypothesis that there was widespread reforestation following the depopulation of Indigenous Peoples in the 16th and 17th centuries.LocationThe central Appalachian Mountains of eastern North America.TaxonQuercus alba, Liriondendron tulipiferaMethodsTo test for reforestation following depopulation, we used tree‐ring evidence of tree recruitment, early radial growth and growth releases from 18 historic log buildings (n = 361 logs) and eight old‐growth forest sites (n = 197 trees). We used inner‐ring dates to determine if a synchronous recruitment event(s) was present at historic sites but absent from old‐growth sites following depopulation. We used cluster analysis to determine if historic logs established in a clearing (fast early growth) or under a canopy (slow early growth). Similarly, we calculated disturbance rates (growth releases per 100 years) to determine if historic logs grew in a clearing (low disturbance) or under a canopy (high disturbance).ResultsHistoric log and old‐growth forest sites both document a period of elevated recruitment beginning in the 1670s. This event was observed in previous studies and across site types, suggesting that either climate variability or the absence of low‐intensity land use (e.g. fire) may have also contributed to forest establishment. Most historic sites (61%–83%) had fast early growth, indicating growth of trees in high‐light conditions. The rate of disturbance was lower at historic sites with fast early growth (5.3 events/century, 95% Cl [3.6, 7.0]) than at old‐growth sites with slow early growth (23.5 events/century, 95% Cl [17.5, 29.5]), consistent with the idea that most historic logs were harvested from fast‐growing, second‐growth forests that established after depopulation.Main ConclusionsOur results support the hypothesis of reforestation in upland forests of the central Appalachian Mountains following depopulation and suggest that upland forests, at the time of European immigration, were at least in part, a legacy of indigenous land use practices. However, the timing of a regional drought event, depopulation and subsequent recruitment of trees, all within the period of ~1650–1690 CE, warrants further research into interactions between indigenous land use and climate during a pivotal period in North American history.

Activity Patterns of Cave-Dwelling Bat Species during Pre-Hibernation Swarming and Post-Hibernation Emergence in the Central Appalachians

In North America, bat research efforts largely have focused on summer maternity colonies and winter hibernacula, leaving the immediate pre- and post-hibernation ecology for many species unstudied. Understanding these patterns and processes is critical for addressing potential additive impacts to White-nose Syndrome (WNS)-affected bats, as autumn is a time of vital weight gain and fat resources are largely depleted in early spring in surviving individuals. Our study sought to examine autumn and spring bat activity patterns in the central Appalachian Mountains around three hibernacula to better understand spatio-temporal patterns during staging for hibernation and post-hibernation migration in the post-WNS environment. From early September through November 2015 and 2016, and from early March through April 2016 and 2017, we assessed the effects of distance to hibernacula and ambient conditions on nightly bat activity for Myotis spp. and big brown bats (Eptesicus fuscus) using zero-crossing frequency division bat detectors near cave entrances and 1 km, 2 km, and 3 km distant from caves. Following identification of echolocation calls, we used generalized linear mixed effects models to examine patterns of activity across the landscape over time and relative to weather. Overall bat activity was low at all sample sites during autumn and spring periods except at sites closest to hibernacula. Best-supported models describing bat activity varied, but date and ambient temperatures generally appeared to be major drivers of activity in both seasons. Total activity for all species had largely ceased by mid-November. Spring bat activity was variable across the sampling season, however, some activity was observed as early as mid-March, almost a month earlier than the historically accepted emergence time regionally. Current timing of restrictions on forest management activities that potentially remove day-roosts near hibernacula when bats are active on the landscape may be mismatched with actual spring post-hibernation emergence. Adjustments to the timing of these restrictions during the spring may help to avoid potentially additive negative impacts on WNS-impacted bat species.

Assessing streamflow sensitivity of forested headwater catchments to disturbance and climate change in the central Appalachian Mountains region, USA

Forest headwater catchments are critical sources of water, but climate change and disturbance may threaten their ability to produce reliable and abundant water supplies. Quantifying how climate change and forest disturbances individually and interactively alter streamflow provides important insights into the stability and availability of water derived from headwater catchments that are particularly sensitive to change. We used long-term water balance data, forest inventory measurements, and a multiple-methods approach using Budyko decomposition and paired catchment models to assess how climate change and forest disturbances interact to alter streamflow in five headwater catchments located along a disturbance gradient in the Appalachian Mountains, USA. We found that disturbance was the dominant driver of streamflow changes; disturbed catchments were more sensitive to climate change than the undisturbed catchment; and disturbance was an important factor for a catchment's sensitivity to climate change, principally through changes in species composition and xylem anatomy. Streamflow sensitivity to climate change increased with increasing proportion of diffuse porous species, suggesting that not all disturbances are equal when it comes to streamflow sensitivity to climate change. Climate change effects were masked by disturbance in catchments with high magnitude/low frequency disturbances and amplified in a catchment with low magnitude/high frequency disturbance. Furthermore, critical assumptions of Budyko decomposition were assessed to evaluate the efficacy of applying decomposition to the headwater scale. Our study demonstrates the efficacy and usefulness of applying decomposition to scales potentially useful to resource managers and decision makers. Our study contributes to a more thorough understanding about the impacts of climate change on disturbed headwater catchments that will help managers to better prepare for and adapt to future changes.

The novel species Navicula eileeniae (Bacillariophyta, Naviculaceae) and its recent expansion in the Central Appalachian region of North America

Background and aims – A novel species of Navicula has been recently discovered in rivers of the central Appalachian Mountains, USA. The purpose of this paper is to formally establish this new species and to determine whether it had been overlooked in the past or is a recent arrival to the area.&#x0D; Methods – We studied historical collections made in Pennsylvania, Virginia and adjacent areas since the 1940s and housed at the ANSP Diatom Herbarium. Light and scanning electron microscopy was employed to study the morphology of the new species and similar Navicula taxa, including those commonly reported at the same locations, or originally described from the rivers of the eastern United States, such as N. radiosafallax, initially established as N. radiosa var. parva by J.H. Wallace.&#x0D; Key results – The new species has an unusual shape of the external raphe slit, which is undulate toward the proximal ends. This character was so far found in a single other Navicula species known only from Europe. Examination of historical materials confirmed that N. eileeniae was absent from collections made in the eastern United States before 2007, but has become progressively more common and abundant in the last decade. The prevalence of this species in streams of low to moderate mineral and nutrient content suggests that its recent expansion cannot be explained by pollution. Climate change is also unlikely to have caused the northward expansion of N. eileeniae, as it has never been recorded south from central Appalachia.&#x0D; Conclusions – The results of this study confirm that a population of previously unknown Navicula species has been expanding in Central Appalachia and suggest that rapid shifts of distributional ranges not readily explainable by environmental changes may occur in protists.

Thin lithosphere beneath the central Appalachian Mountains: Constraints from seismic attenuation beneath the MAGIC array

The passive margin of the eastern coast of the United States is known to be geologically active, with recently rejuvenated topography, intraplate seismicity, and volcanism of Eocene age. This study uses seismic data from the Mid-Atlantic Geophysical Integrative Collaboration (MAGIC) experiment to constrain lateral variations in the attenuation of teleseismic P waves beneath the central Appalachian Mountains to shed light on the structure and dynamics of the upper mantle at this “active” passive margin. We use a Monte Carlo approach to estimate variations in attenuation along with both data and model uncertainties. The quality factor of the upper mantle dramatically decreases over a distance of less than 50 km on the western side of the central Appalachian Mountains, where a low-velocity anomaly has been previously inferred. Extrinsic factors such as scattering or focusing are rejected as explanations for the observations on the basis of finite-difference waveform modeling experiments. The peak in attenuation beneath the crest of the Appalachian Mountains requires that near- to super-solidus conditions occur in the upper mantle and is co-located with volcanism of Eocene age. Our preferred interpretation is that the attenuation reflects the removal of the mantle lithosphere via delamination beneath the mountains, followed by ongoing small-scale convection.