Regional Differentiation in Genetic Components for the American Beech, Fagus grandifolia Ehrh., in Relation to Geological History and Mode of Reproduction

Fagus grandifolia , were investigated throughout its geographical range, using allozyme polymorphisms. A total of 1,131 trees from 21 populations were examined for 32 alleles of 10 polymorphic and two monomorphic loci in eight enzyme systems. The mean expected heterozygosity was 0.186, which indicates a relatively high genetic diversity within the populations. The levels of population differentiation were high, as revealed by genetic parameters, i.e., G _ST =0.168 and F _ST =0.167. The results of principal component analysis on allele frequencies clearly revealed unique regional patterns of differentiation in genetic components among populations “with” and “without” vegetative regeneration by root suckers. The American beech populations consist of two genetically distinct clusters, one from the Gulf-coastal plain, eastern coastal plain, Piedmont Plateau and Ozark Plateau; and the other from the remaining northern glaciated territories. Populations from the Blue Ridge and Great Smoky Mountains turned out to belong to the latter cluster, which is also characterized by extensive regeneration via root suckers. The consequences of regional differentiation in genetic components are discussed in relation to the postglacial spread from refugia to the current geographic distributions and the mode of reproduction. Received 8 August 2000/ Accepted in revised form 29 May 2001     

Carex fumosimontana (Cyperaceae), a new endemic from the Great Smoky Mountains National Park, North Carolina and Tennessee

Carex fumosimontana (Great Smoky Mountain Sedge), a new and narrowly endemic species of section Phacocystis, is described from the southern Appalachian Mountains of North Carolina and Tennessee, in the southeastern United States. It differs from the closely related C. gynandra in its dark reddish-brown pistillate scales that are strongly retuse apically, shorter spikes, narrower leaves, and strongly red-scabrous proximal sheath faces. It is locally abundant and sometimes the dominant sedge where it occurs in spite of being completely restricted to high-elevation spruce-fir forests and associated environs of Great Smoky Mountains National Park.     

Neophylax kolodskii (Trichoptera: Uenoidae), A New Species from the Great Smoky Mountains National Park,U.S.A.

Neophylax kolodskii sp. n. from Great Smoky Mountains National Park is described and illustrated from adult specimens.     

Nitrogen mineralization in high elevation forests of the Appalachians. I. Regional patterns in southern spruce-fir forests

Annual and seasonal rates of net nitrogen mineralization were determined for 19 sites in the spruce-fir forests of the Southern Appalachian Mountains. These sites included high and low elevation stands of red spruce (Picea rubens Sarg.) and Fraser fir (Abies fraseri (Pursh.) Poir.) on east and west exposures on Whitetop Mountain, Virginia; Mt. Mitchell, North Carolina; and Clingman's Dome in the Great Smoky Mountains National Park. Mineralization rates were determined using in situ soil incubations in PVC tubes with ion exchange resin bags placed in the bottom of the tubes to collect leachate. Throughfall was collected in resin bags placed in the top of the tubes. Average initial NH₄-N + NO₃-N ranged from 0.6 to 4.8 kg N/ha across all plots, and average mineralization rates ranged from 26 to 180 kg-N ha⁻¹ yr⁻¹. Throughfall ranged from 18 to 32 kg-N ha⁻¹ yr⁻¹ with NH₄-N accounting for about two-thirds of the throughfall N across all sites. Throughfall and mineralization rates were not related to elevation or exposure. The high rates of N mineralization and relatively high nitrate concentrations indicate that leaching losses of nitrogen and associated cations could be substantial. Requests for offprints     

胡杨（Populus euphratica）在额济纳绿洲三种生境内的根蘖繁殖特性

以额济纳荒漠绿洲胡杨根蘖幼苗为研究对象,通过对绿洲内胡杨分布的3种主要生境内根蘖幼苗的调查,得出如下结论。近年来绿洲内胡杨种群的更新几乎完全依赖于无性繁殖更新,种子萌发产生的幼苗在调查地内没有发现。河岸沙丘地及胡杨林下地的根蘖幼苗中,3龄幼苗所占比重最大,龄级越小的根蘖苗在群落中的数量越少;在河水漫灌后的林间空地,2龄幼苗的数量最多。水漫灌后的林间空地中根蘖幼苗密度显著大于其余两生境内根蘖幼苗密度,同时该生境内每段胡杨根系萌生出的不定芽也大于另两生境。随着龄级增加,未枯枝根蘖幼苗的比率逐渐减小。根蘖幼苗的萌发点分布于土层30cm以内的根系上,分布深度大于30cm的根系不能萌发出根蘖幼苗。     

Genetic diversity of flowering dogwood in the Great Smoky Mountains National Park

In the past three decades, flowering dogwood (Cornus florida) populations have experienced severe declines caused by dogwood anthracnose. Mortality has ranged from 48% to 98%, raising the concern that the genetic diversity of this native tree has been reduced significantly. In this study, we investigated levels of genetic diversity and population structure of flowering dogwood populations in the Great Smoky Mountains National Park (GSMNP). Understanding the factors influencing geographic distribution of genetic variation is one of the major concerns for preserving biodiversity and conservation of native populations. Eighteen microsatellite loci were used to evaluate the level and distribution of genetic variation of native flowering dogwood trees throughout the GSMNP. Significant genetic structure exists at both landscape and local levels. Two genetic clusters exist within the park and are separated by the main dividing ridges of the Great Smoky Mountains. The differentiation of the clusters is subtle, but statistically significant. Gene flow, evident through low-elevation corridors, indicates that nonrandom mating occurs between related individuals despite wide dispersal of seeds. Although high mortality rate and reduced fecundity caused by dogwood anthracnose severely affected native flowering dogwood populations throughout the entire GSMNP, this study confirmed that considerable genetic diversity still exists at the population level. It seems unlikely that recent demographic dynamics have resulted in a depletion of genetic variation.     

KARYOTYPES OF FIVE PLANT SPECIES WITH DISJUNCT DISTRIBUTIONS IN VIRGINIA AND THE CAROLINAS

Five species (Actaea pachypoda, Aralia nudicaulis, Cornus alternifolia, Panax quinquefolius, and Symplocarpus foetidus) display a disjunct distribution between the Mountains and Piedmont in North Carolina, South Carolina, and Virginia. The Piedmont populations are small and have apparently been isolated from the Mountain populations for several thousand years. Karyotype differences among populations were found only in A. pachypoda, and even in this species the differences were slight. The absence of population differences in four species, and the moderate differentiation found in A. pachypoda, indicate considerable cytological stability in these species.     

Reproductive isolation and cryptic introgression in a sky island enclave of Appalachian birds

Reproductive isolation is central to the speciation process, and cases where the strength of reproductive isolation varies geographically can inform our understanding of speciation mechanisms. Although generally treated as separate species, Black‐capped chickadees (Poecile atricapillus) and Carolina chickadees (P. carolinensis) hybridize and undergo genetic introgression in many areas where they come into contact across the eastern United States and in the northern Appalachian Mountains. The Great Smoky Mountains harbor the last large breeding population of atricapillus in the southern Appalachians, isolated from the species’ main range by nearly 200 km. This population is believed to be reproductively isolated from local carolinensis due to an unusual, behaviorally mediated elevational range gap, which forms during the breeding season and may function as an incipient reproductive isolating mechanism. We examined the effectiveness of this putative isolating mechanism by looking for genetic introgression from carolinensis in Great Smoky Mountain atricapillus. We characterized this population and parental controls genetically using hundreds of amplified fragment length polymorphism (AFLP) loci as well as mitochondrial DNA (mtDNA) sequence data from cytochrome‐b. Great Smoky Mountain atricapillus have experienced nuclear genetic introgression from carolinensis, but at much lower levels than other populations near the hybrid zone to the north. No mitochondrial introgression was detected, in contrast to northern contact areas. Thus, the seasonal elevational range gap appears to have been effective in reducing gene flow between these closely related taxa.     

Gradient analysis of the distribution of a fungal disease of Cornus florida in the southern Appalachian Mountains,Tennessee

Abstract: Based on 115 samples collected throughout the western portion of Great Smoky Mountains National Park, southern Appalachian Mts., and on spatial data derived in a GIS (Geographical Information System), the distribution of the disease dogwood anthracnose affecting Cornus florida (flowering dogwood), caused by the fungus Discula destructiva in this portion of the Park was assessed, and factors contributing to the disease's severity were identified through correlation and multiple linear regression analysis. The degree of infection varies considerably locally, and is influenced by elevation, slope curvature, slope position, and potential soil moisture. However, the abundance of C. florida (stem density) alone explains 25 % of the variation in disease severity. Factors contributing to disease severity do not change significantly between disturbed and undisturbed sites. The highest mortality rates are restricted to dense stands in damp, sheltered sites at low slope positions, implying that surviving populations of flowering dogwood may represent a biased genetic subset of the original population.     

Nitrogen mineralization in high-elevation forests of the appalachians. II. Patterns with stand development in fir waves

Wave-like patterns of mortality and regeneration of balsam fir (Abies balsamea {L.} Mill.) and Fraser fir (A. fraseri {Pursh.} Poir.) forests at high elevations in the Appalachian Mountains offer a unique opportunity to study the effects of stand development on nitrogen cycling. We sampled two fir waves, one with Fraser fir on Mt. LeConte in the Great Smoky Mountains National Park, and one with balsam fir on Whiteface Mountain in New York. Net nitrogen mineralization for 3 summer months at Mt. LeConte was high in the dead fir zone (47 kg-N/ha), lower in the regeneration and juvenile zones (24 and 21 kg-N/ha), and highest in the mature zone (61 kg-N/ha). This sampling period probably accounted for about 60% of the annual total. The pattern was similar in the balsam fir wave on Whiteface Mountain, with N mineralization rates of 39 and 33 kg-N/ha over 2 months for the regenerating and juvenile zones, and 43 and 54 kg-N/ha for the mature and dead zones. Throughfall nitrogen followed a fairly similar pattern, with rates ranging from 4.5 to 10 kg-N/ha for 2 or 3 months across all zones at both sites. Tension-free lysimeters indicated very little leaching of nitrogen below 30 cm depth (the maximum was 2.6 kg-N/ha), but these estimates may be low. We conclude that nitrogen mineralization is high at all stages of stand development, perhaps exceeding the uptake capacity of the trees. Rates of nitrogen leaching may be high in these ecosystems and should receive further attention. Request for offprints     

Systematics of dusky salamanders, Desmognathus (Caudata: Plethodontidae), in the mountain and Piedmont regions of Virginia and North Carolina, USA

We analysed mitochondrial (cytochrome  b ) nucleotide sequences, nuclear allozyme markers, and morphometric characters to investigate species boundaries and phylogenetic relationships among dusky salamanders ( Desmognathus ) in the southern Blue Ridge and adjacent Piedmont Physiographic Provinces of Virginia and North Carolina. Our results revealed four distinct mitochondrial DNA clades that are also characterized by distinct allozyme markers. One clade consists of sequences derived from populations distributed from New England to south-western Virginia that are referable to Desmognathus fuscus Rafinesque, 1820, although there is considerable sequence and allozyme divergence within this clade. A second clade consists of sequences derived from populations referable to Desmognathus planiceps Newman, 1955, a form that we resurrect from its long synonymy under D. fuscus . Desmognathus planiceps and D. fuscus also differ in mandibular tooth shape. Two other cytochrome  b sequences recovered from populations along the Blue Ridge escarpment in southern Virginia are quite divergent from those of the previous two clades, and these populations may represent yet another distinct species. Sequences from a population in the Brushy Mountains in the Piedmont of northern North Carolina are similar to those of Desmognathus carolinensis . Population groupings indicated by allozyme data generally correspond to the cytochrome  b clades. Cryptic diversity in Appalachian desmognathan salamanders clearly requires further study. © 2008 The Linnean Society of London, Zoological Journal of the Linnean Society , 2008, 152 , 115–130.     

Dispersal by cattle of salt-marsh and dune species into salt-marsh and dune communities

We investigated the spatial cohort structure of Trillium populations in old-growth cove forests in Great Smoky Mountains National Park (TN, USA). We mapped the locations of all Trillium erectum L., Trillium grandiflorum (Michaux) Salisbury, and Trillium vaseyi Harbison occurring within two 10 × 10 m sample plots at each of three old-growth sites—Anthony Creek, Cove Mountain, and Kalanu Prong. The height and life stage of each individual were recorded and a randomly selected subset was excavated for age determination. Our results suggest that Trillium populations in cove forests of the southern Appalachians display a high degree of spatial aggregation and are relatively stable, spatially, over long time periods (i.e., decades). Individual patches (aggregations of plants) within populations were typically multi-aged and no clear spatial cohort structure was observed. Surprisingly, more isolated plants (distal from large aggregations) were among the oldest plants in the population, rather than recent colonists dispersing away from parent populations. Individual species were less mingled than expected given that they share a common dispersal agent (ants). This study provides a double-baseline for Trillium population structure in old, primary forests with low browse pressure.     

New species of small dictyostelids from the Great Smoky Mountains National Park

Ten new species of small dictyostelids, five belonging to Acytostelium (A. anastomosans, A. longisorophorum, A. magnisorum, A. serpentarium and A. singulare) and five to Dictyostelium (D. amphisporum, D. naviculare, D. oculare, D. potamoides and D. stellatum), were isolated from forest soils in the Great Smoky Mountains National Park. These species were recovered mostly from acidic soils and at higher elevations. They represent a large group of dictyostelids of small stature (<2 mm total height) on which we are beginning to accumulate more information.     

Fireflies as a catalyst for science education

The study of fireflies makes an ideal subject for introducing students of all ages to the world of science, conservation biology, field studies and the importance of observation and understanding connections in the natural world.The synchronous fireflies, Photinus carolinus of the Great Smoky Mountains National Park's Elkmont Historic District can be used as a basis for classroom and field activities in subjects as diverse as conservation biology, economics, geography, ecology, governmental policy, zoology, history, taxonomy and animal behavior.Having been fascinated with the synchronous fireflies for over two decades, I will use the life cycle of the Elkmont Phontinus carolinus found in the Great Smoky Mountains National Park as an example.     

A new cost‐distance model for human accessibility and an evaluation of accessibility bias in permanent vegetation plots in Great Smoky Mountains National Park,USA

Question: Can a new cost‐distance model help us to evaluate the potential for accessibility bias in ecological observations? How much accessibility bias is present in the vegetation monitoring plots accumulated over the last three decades in Great Smoky Mountains National Park? Location: Great Smoky Mountains National Park, North Carolina and Tennessee, USA. Methods: Distance, slope, stream crossings, and vegetation density were incorporated into a least‐cost model of energetic expenditure for human access to locations. Results: Estimated round‐trip energy costs for the park ranged from 0 to 1.62 × 10⁵ J kg^?1. The estimated round‐trip energetic expenditure for the surveys ranged from 53 to 1.51 × 10⁵ J kg^?1. Their distribution was more accessible than the random expectation. Ten (17%) of the vegetation types in the park are significantly under‐sampled relative to their area, and 16 (29%) are over‐sampled. Plots in 18 of the 40 vegetation types exhibited a significant positive correlation with accessibility. Conclusions: The least‐cost model is an improvement over previous attempts to quantify accessibility. The bias in plot locations suggests using a least‐cost model to test for bias in cases in which human accessibility is confounded with other sources of ecosystem variation.     

Decomposition of standing dead trees in the southern Appalachian Mountains

Summary Decomposition of standing dead trees that were killed by fire was examined for 10 species in the Great Smoky Mountains National Park. The decrease in wood density as fire age increased was used to estimate decomposition rates. Quercus prinus had the fastest decay rate (11% yr^-1) while Pinus virginiana had the slowest decay rate (3.6% yr^-1) for standing dead wood. Decay rates were intermediate between those reported in western USA and tropics for wood.     

Clonal propagation and hydroxycitric acid production from <Emphasis Type="Italic">in vitro</Emphasis> shoot cultures of <Emphasis Type="Italic">Garcinia indica</Emphasis> using root suckers as explant

In vitro shoots from mature tree explants often show poor root initiation response. Garcinia species are known for vegetative propagation through root suckers in natural environment. To establish a protocol for clonal propagation, apical and intercalary buds of the root suckers obtained from a mature elite tree of Garcinia indica were used as explant source. Multiple shoots were initiated in woody plant medium fortified with combinations of 6-benzylaminopurine and 1-phenyl-3-(1,2,3-Thiadiazol-5-YL)-urea. A pulse treatment of indole-3-butyric acid ranging from 4.9 to 19.6 mM for 30 s and 1 min was tried for root induction. The resulting in vitro plants were successfully hardened. The initiated shoots were also used for in vitro synthesis of hydroxycitric acid in shake flask cultures. The effect of basal medium, incubation period and plant growth regulators on production of hydroxycitric acid in vitro was studied.     

Low-temperature pretreatment of the root system of Brassica rapa L. plants: effects on the xylem sap exudation and on the nitrate absorption rate

Brassica rapa plants were exposed for a 52 h period (as pretreatment) to a differential temperature (DT) between roots (5°C) and shoots (20°C), while control plants were maintained with both shoot and roots at 20°C (warm grown = WG). Measured at 20°C, volume flow of xylem exudate from roots of DT plants was enhanced compared with that from WG plants, while transpiration flows were similar in pretreated and control plants. Both transpiration and exudation flows were dependent upon shoot/root ratio. Differences in the volume flow of exudate were principally related to increases in root hydraulic conductance. Anion fluxes (notably nitrate) into xylem exudate of DT plants were significantly greater than those into exudate of WG plants. This enhancement of nitrate flow from the pretreated roots was associated with a two-fold increase in nitrate uptake rate. The relationship of the cold-induced change in nitrate uptake capacity with shoot/root ratio is discussed in terms of control of nitrate absorption by shoot sink strength.