South Carolina Population Research Articles

Phenotypic plasticity in the sailfin molly III: Geographic variation in reaction norms of growth and maturation to temperature and salinity.

Phenotypic plasticity, the ability of a single genotype to produce different phenotypes under different environmental conditions, plays a profound role in several areas of evolutionary biology. One important role is as an adaptation to a variable environment. While plasticity is extremely well documented in response to many environmental factors, there is controversy over how much of that plasticity is adaptive. Evidence is also mixed over how often conspecific populations display qualitative differences in the nature of plasticity. We present data on the reaction norms of growth and maturation to variation in temperature and salinity in male and female sailfin mollies (Poecilia latipinna) from three locally adjacent populations from South Carolina (SC). We compare these reaction norms to those previously reported in locally adjacent populations from north Florida (NF). In general, patterns of plasticity in fish from SC were similar to those in fish from NF. The magnitude of plasticity differed; fish from SC displayed less plasticity than fish from NF. This was because SC fish grew faster and matured earlier at the lower temperatures and salinities compared to NF fish. This is a countergradient pattern of variation, in which SC fish grew faster and matured earlier in conditions that would otherwise slow growth and delay maturity. Among fish from both regions, males were much less plastic than females, especially for length at maturity. While there was no detectable heterogeneity among populations from NF, males from one of the SC populations, which is furthest from the other two, displayed a qualitatively different response in age at maturity to temperature variation than did males from the other two SC populations. The pattern of population variation in plasticity within and among regions suggests that gene flow, which diminishes with distance in sailfin mollies, plays a critical role in constraining divergence in norms of reaction.

Extension of the geographical range of the primary burrowing crayfish Cambarus strigosus Hobbs, 1981 (Decapoda: Astacidea: Cambaridae) in South Carolina

Abstract Knowledge of the geographical distribution for many primary burrowing crayfishes is often limited to information presented in species descriptions or field notes associated with epigean crayfish surveys. Cambarus strigosusHobbs, 1981, a rare primary burrowing crayfish, was collected as part of a survey of the Sumter National Forest, South Carolina (SC), USA. Prior to this discovery, C. strigosus appeared to be endemic to mid-reaches of the Broad River Drainage in Georgia (GA). We conducted additional field sampling in SC and GA and used mitochondrial DNA (mtDNA) to compare the relative genetic distance between individuals across all populations in an effort to determine the identity of the specimens collected. Genetic data indicated that the crayfish collected in SC was C. strigosus, with one shared haplotype between SC and GA populations. Our genetic results exhibited geographic structuring and indicated that SC populations have a specific haplotype unique to them, providing strong evidence that SC populations are not introduced. Two additional SC records of C. strigosus from 1983 housed in the US National Museum were examined and determined to be C. strigosus. With these records, we hypothesized that like in GA, the distribution of C. strigosus in SC is limited to riparian habitats associated with the Savannah River Drainage. While the range of this species has been extended, it is still limited to small portions of this drainage. Thus, further sampling to determine the true extent of C. strigosus distribution within SC along with conservation efforts are needed to protect this globally rare species.

SARS-CoV-2 concentration in wastewater consistently predicts trends in COVID-19 case counts by at least two days across multiple WWTP scales.

Wastewater surveillance of SARS-CoV-2 has proven instrumental in mitigating the spread of COVID-19 by providing an economical and equitable approach to disease surveillance. Here, we analyze the correlation of SARS-CoV-2 RNA in influents of seven wastewater plants (WWTPs) across the state of South Carolina with corresponding daily case counts to determine whether underlying characteristics of WWTPs and sewershed populations predict stronger correlations. The populations served by these WWTPs have varying social vulnerability and represent 24% of the South Carolina population. The study spanned 15 months from April 19, 2020, to July 1, 2021, which includes the administration of the first COVID-19 vaccines. SARS-CoV-2 RNA concentrations were measured by either reverse transcription quantitative PCR (RT-qPCR) or droplet digital PCR (RT-ddPCR). Although populations served and average flow rate varied across WWTPs, the strongest correlation was identified for six of the seven WWTPs when daily case counts were lagged two days after the measured SARS-CoV-2 RNA concentration in wastewater. The weakest correlation was found for WWTP 6, which had the lowest ratio of population served to average flow rate, indicating that the SARS-CoV-2 signal was too dilute for a robust correlation. Smoothing daily case counts by a 7-day moving average improved correlation strength between case counts and SARS-CoV-2 RNA concentration in wastewater while dampening the effect of lag-time optimization. Correlation strength between cases and SARS-CoV-2 RNA was compared for cases determined at the ZIP-code and sewershed levels. The strength of correlations using ZIP-code-level versus sewershed-level cases were not statistically different across WWTPs. Results indicate that wastewater surveillance, even without normalization to fecal indicators, is a strong predictor of clinical cases by at least two days, especially when SARS-CoV-2 RNA is measured using RT-ddPCR. Furthermore, the ratio of population served to flow rate may be a useful metric to assess whether a WWTP is suitable for a surveillance program.

Spider mite resistance to miticides in South Carolina strawberry and implications for improved integrated pest management.

Tetranychus urticae Koch (Acari: Tetranychidae), twospotted spider mite, is a major secondary pest of strawberry and can cause significant yield loss. Tetranychus urticae is typically controlled using miticides, which has led to rapid resistance development. In South Carolina (USA), extension agents and growers have reported field failures of miticides (inadequate pest suppression), but resistance has not been quantitatively determined. In 2018, we determined the level of miticide resistance of six T. urticae populations found on strawberry across South Carolina. We examined efficacy of all miticides registered for use on US strawberry by conducting an initial diagnostic bioassay at 20% of the maximum labeled field rate. Any population × active ingredient combination resulting in < 55% mortality was identified as 'potentially resistant' and concentration-response bioassays were then conducted to calculate LC50 values for an individual population. These values were compared with those of a known-susceptible laboratory population to calculate resistance ratios (RR). Our results indicate that examined South Carolina populations of T. urticae from strawberry were highly resistant to bifenthrin (RR = 100-60,000) and there was reduced susceptibility to fenbutatin-oxide (RR = 25-123). The 'Sardinia' population had decreased abamectin susceptibility (RR = 25). No resistance to hexythiazox, etoxazole, acequinocyl, bifenazate, fenpyroximate, spiromesifen, or cyflumetofen was found. Based on available data, it appears that miticide resistance is not a likely cause of field failures and issues related to application error and coverage should be investigated. Overall, this work supports the need to reduce the use of broad-spectrum pesticides and older products, in favor of newer miticide chemistries due to resistance issues.

First report of Seville root-knot nematode, Meloidogyne hispanica (Nematoda: Meloidogynidae) in the USA and North America.

A high number of second stage juveniles of the root-knot nematode were recovered from soil samples collected from a corn field, located in Pickens County, South Carolina, USA in 2019. Extracted nematodes were examined morphologically and molecularly for species identification which indicated that the specimens of root knot juveniles were Meloidogyne hispanica. The morphological examination and morphometric details from second-stage juveniles were consistent with the original description and redescriptions of this species. The ITS rRNA, D2-D3 expansion segments of 28S rRNA, intergenic COII-16S region, nad5 and COI gene sequences were obtained from the South Carolina population of M. hispanica. Phylogenetic analysis of the intergenic COII-16S region of mtDNA gene sequence alignment using statistical parsimony showed that the South Carolina population clustered with Meloidogyne hispanica from Portugal and Australia. To our best knowledge, this finding represents the first report of Meloidogyne hispanica in the USA and North America.

Development and characterization of microsatellites from the sweetpotato weevil, Cylas formicarius elegantulus

AbstractTo conduct population genetics analyses on sweetpotato weevils (Cylas formicarius elegantulus) collected from three populations in the United States, microsatellite loci were developed from sweetpotato weevil transcriptome sequences obtained from a publicly available database. Nineteen of 27 microsatellite loci tested were usable for population analyses. Sweetpotato weevil individuals from Georgia (N = 17), Hawaii (N = 16) and South Carolina (N = 12) were analysed. Here, we present microsatellite primer sequences for 19 loci and population genetics statistics, including diversity, population differences and relatedness. Thirty‐nine alleles were detected in the 45 individuals, and four private alleles were observed in individuals from the Hawaii and South Carolina populations. Observed heterozygosities ranged from 0.00 to 1.00, and expected heterozygosities ranged from 0.00 to 0.44. The mean Shannon's information index ranged from 0.30 to 0.49 for the three populations. Pairwise differences among populations (FST estimates) from individuals ranged from a low of 0.022 between Georgia and Hawaii to a high of 0.036 between Georgia and South Carolina, and cluster analysis (PCA and Structure) indicated two populations independent of geographical location.

2733. Association Between Influenza Vaccination Coverage and Ambulatory Antibiotic Prescription Rates in Children in South Carolina

BackgroundPrior studies demonstrated an increase in ambulatory antibiotic prescription rates during the peak of Influenza virus activity, which often occurs during the first 4 months of the year in Southeastern United States. However, the impact of Influenza vaccination coverage on antibiotic prescription rates remains undefined. The purpose of this retrospective cohort study is to examine the association between Influenza vaccination coverage and ambulatory antibiotic prescription rates in children in South Carolina from 2012 to 2017.MethodsMedicaid and State Employee Health Plan pharmacy claims for outpatient oral antibiotics were utilized for estimation of community antibiotic prescription rates in South Carolina population 6 months to 17 years of age from January 1, 2012 to December 31, 2017, which represents approximately 60% of the South Carolina population in this age group. Linear regression was used to examine the association between antibiotic prescription rates in January to April of each year and Influenza vaccine coverage in children 6 months to 17 years old after adjustments for Influenza vaccine effectiveness in that season as obtained from Centers for Disease Control and Prevention (CDC).ResultsDuring the 6-year study period, the mean antimicrobial prescription rate in children in South Carolina declined from 103 to 79 per 1000 person-months for the months January through April indicating a 26% decline (P < 0.0001). Influenza vaccine coverage also increased from 50.6% during the first Influenza season of the study and peaked at 60.7% in 2014–2015 Influenza season (Figure 1). After adjusting for the vaccine effectiveness, the decline in antibiotic prescription rate was significantly associated with an increase in vaccine coverage in children (P-value < 0.01). Antibiotic prescription rates declined by 3 per 1,000 person-months for each 1% increase in Influenza vaccine coverage in children.ConclusionThere is a temporal association between the increase in Influenza vaccination coverage and the decline in ambulatory antibiotic prescription rates in children in South Carolina. Achieving the CDC’s set target Influenza vaccination coverage of 70% of the population may be associated with greater decline in ambulatory antibiotic prescription rates in children in the future. Disclosures All authors: No reported disclosures.

Genetic Diversity Within and Among Populations of the Endangered Southeastern North American Plant Species, Tiedemannia canbyi (Apiaceae) and its More Common Congener, T. filiformis

Genetic analyses can provide important insights for the successful reestablishment or augmentation of populations of endangered plant species. Tiedemannia canbyi (Apiaceae) is an endangered southeastern US coastal plain species whose natural range extends from southwestern Georgia to southeastern North Carolina with a disjunct (approximately 600 km) population in Maryland. T. canbyi currently has only approximately 40 known populations. Thirty nuclear allozyme loci were employed to determine the levels and distribution of neutral genetic diversity within and among 14 populations of T. canbyi and eight populations of its more common and widespread congener, T. filiformis. Both species exhibited relatively high levels of genetic diversity (He = 0.185 and 0.284 for T. canbyi and T. filiformis, respectively). The Maryland population of T. canbyi had the lowest overall level of genetic diversity (He = 0.089). Genetic differentiation among populations of both species was similar (GST = 0.250 and 0.254). Populations of T. canbyi formed two genetically distinct groups, southwest and south-central Georgia vs. eastern Georgia, South Carolina, and Maryland. Six T. filiformis populations from southern and coastal Georgia and coastal South Carolina formed one genetically similar group while an inland population from Georgia and an inland South Carolina population were genetically distinct from each other and from the six coastal populations. Patterns of genetic variation observed for these two Tiedemannia species are most consistent with the different groups of populations having originated from genetically discrete glacial refugia. The value of these results for the restoration and/ or augmentation of T. canbyi populations is discussed.

975. Clostridium difficile Infection and Antibiotic Prescription Rates in the Community: Explaining the Gender Gap

BackgroundPrevious studies have reported higher incidence rates of community-associated Clostridium difficile infection (CA-CDI) in women than in men. This cross-sectional population-based study examines whether this difference in CA-CDI rates across genders is driven by or independent of antibiotic use.MethodsMedicaid and State Employee Health Plan pharmacy claims for outpatient oral antibiotics and associated medical claims were utilized for estimation of community antibiotic prescription rates in South Carolina population 18 to 64 years of age from January 1, 2015 to December 31, 2015. CA-CDI cases were identified from National Healthcare Safety Network (NHSN) and South Carolina Infectious Disease and Outbreak Network (SCION) through complete enumeration of South Carolina population of the same age and study period as above. Incidence rates of CA-CDI were reported in both men and women 18–39 and 40–64 years of age before and after adjustments for antibiotic prescription rates in the same gender and age group. The 95% confidence intervals (CI) were calculated to examine statistical difference in incidence rates across genders within the same age group.ResultsDuring the calendar year 2015, a total of 1,564 CA-CDI cases were identified in South Carolina residents 18–64 years of age. The incidence rate of CA-CDI per 100,000 person-years was higher in women than in men in age groups 18–39 years (37.3 [95% CI: 32.8–41.8] vs. 21.0 [95% CI: 17.6–24.4]) and 40–64 years (86.4 [95% CI: 80.1–92.8] vs. 56.6 [95% CI: 51.2–61.9]. Similarly, antibiotic prescription rates per 100 person-years were higher in women than men in the 2 respective age groups (118.8 [95% CI: 118.3–119.3] vs. 54.3 [95% CI: 53.9–54.8] and 130.4 [95% CI: 129.8–130.9] vs. 83.8 [95% CI: 83.3–84.4]. After adjustments for antibiotic prescriptions, there was no significant difference in the incidence rates of CA-CDI per 100,000 prescriptions between women and men 18–39 years of age (31.4 [95% CI: 27.6–35.2] vs. 38.6 [95% CI: 32.4–44.8] and 40–64 years old (66.3 [95% CI 61.5–71.2] vs. 67.5 [95% CI: 61.1–73.8]).ConclusionHigher crude incidence rates of CA-CDI in women are likely due to higher outpatient antibiotic prescription rates in women when compared with men.Disclosures P. B. Bookstaver, CutisPharma: Scientific Advisor, <$1,000. Melinta Therapeutics: Speaker’s Bureau, <$1,000.

Associations between perfluorinated alkyl acids in blood and ovarian follicular fluid and ovarian function in women undergoing assisted reproductive treatment

Endocrine disrupting contaminants, in combination with other environmental variables, are associated with altered reproductive health. Assisted reproductive technology (ART) procedures offer valuable opportunities to explore the connections between environmental contaminants in the ovarian microenvironment and measures of fertility, including impaired responsiveness to gonadotropins. Here, we investigate an emerging class of environmental contaminants, the perfluorinated alkyl acids (PFAAs), to determine whether ovarian contaminant levels are associated with measures of ovarian responsiveness and fertility outcomes in a South Carolina population of women undergoing ART. Levels of PFAAs in plasma and follicular fluid samples collected from women undergoing ovarian stimulation were analyzed by liquid chromatography tandem mass spectrometry (LC-MS/MS). Six PFAAs were detected in both plasma and follicular fluid. PFAA concentrations in plasma correlate strongly to those detected in ovary and, with the exception of one compound, remain stable throughout ovarian stimulation. The concentration of PFHxS in follicular fluid inversely relates to baseline follicle counts. While no significant relationships were detected between ovarian response measures and PFAA concentrations, we identified a negative relationship between follicular fluid PFDA and PFuNA and blastocyst conversion rates. Our assessments indicate that plasma levels of PFAAs serve as a sound proxy of those in the ovarian compartment and that follicular fluid levels of specific PFAA compounds are inversely related to important clinical measures of reproductive health including baseline follicle count and post-fertilization success.

Prevalence of Autism Spectrum Disorders Among Children With Intellectual Disability.

Autism spectrum disorders (ASD) often co-occur with intellectual disability (ID) and are associated with poorer psychosocial and family-related outcomes than ID alone. The present study examined the prevalence, stability, and characteristics of ASD estimates in 2,208 children with ASD and ID identified through the South Carolina Autism and Developmental Disabilities Network. The prevalence of ASD in ID was 18.04%, relative to ASD rates of 0.60%-1.11% reported in the general South Carolina population. Compared to children with ASD alone, those with comorbid ID exhibited increased symptom severity and distinct DSM-IV-TR profiles. Further work is needed to determine whether current screening, diagnostic, and treatment practices adequately address the unique needs of children and families affected by comorbid ASD and ID diagnoses.

18S rRNA and COI haplotype diversity of Trichodorus obtusus from turfgrass in South Carolina

The stubby-root nematode,Trichodorus obtusus, was recently identified on zoysiagrass in South Carolina, USA. In Florida,T. obtususcauses more damage than other stubby-root nematodes encountered in turfgrass. The objective of this study was to use morphological analysis, mitochondrial DNA (COI: cytochrome oxidase 1) and nuclear (18S rRNA) sequence data to study the genetic structure and haplotype diversity of populations recovered from turfgrasses in South Carolina. Numerous morphological differences were observed among populations. Three 18S haplotypes were shared among South Carolina and Florida populations, and six mitochondrial haplotypes were identified in South Carolina samples. Of the six COI haplotypes, four haplotypes were restricted to one population from St Augustinegrass. The lowest haplotype diversity was found in samples from zoysiagrass. Sequences of the COI mtDNA gene ofT. obtususwere published in GenBank and represent the first mtDNA sequences for the genusTrichodorus.

Telestroke Centers as an Option for Addressing Geographical Disparities in Access to Stroke Care in South Carolina, 2013.

Telestroke centers can increase access to proper and timely diagnosis and treatment of stroke, especially for rural populations, thereby reducing disability and death. Census tract information was used to map primary stroke centers geographically and to identify areas that would benefit from additional access to medical care via telestroke centers (health care facilities that provide information on stroke care from a distance). Results indicate that in 2013, approximately half of the South Carolina population did not have access to a primary stroke center within a 30-minute drive of their home, and 30% did not have access within 60 minutes. Increasing access to prompt evaluation, diagnosis, and treatment of stroke and improving long-term quality of life requires the addition of telestroke centers in areas without primary stroke centers and examination of the effects of these centers on stroke incidence and mortality in South Carolina.

Phylogeographic Patterns Among the Subspecies ofNotophthalmus viridescens(Eastern Newt) in South Carolina

Relatively little work has been done on the population genetics and phylogenetic patterns in Notophthalmus viridescens (Eastern Newt). The most recent study by Gabor and Nice (2004) divided the sampled populations into northern and southern groups rather than along taxonomic lines, and patterns of genetic variation indicated the southern populations were isolated and undergoing genetic drift. To re-evaluate these patterns, we collected sequence data on the mitochondrial ND2 and the flanking tRNAMet genes in fifteen South Carolina populations in the piedmont, sandhills, and lower coastal plain where three of the four subspecies were located (we found no Eastern Newts in the upper coastal plain). Haplotypes did not group by taxonomic designation in phylogenetic analyses, suggesting introgressive hybridization has occurred. Statistical parsimony analysis resolved the haplotype groups into two geographic groups, and partitioning of genetic variation between these groups was significant. We suggest these groups represent populations established during the last glacial maximum, a pattern that has been observed in other pond-breeding salamanders.

Population Genetic Structure of &lt;I&gt;Pseudatomoscelis seriatus&lt;/I&gt; (Hemiptera: Miridae) in the Cotton-Growing Regions of the United States

The cotton fleahopper, Pseudatomoscelis seriatus (Reuter) (Hemiptera: Miridae) is an economically important insect pest of cotton in the United States. However, reports of cotton fleahopper infestation and its management in cotton fields are restricted primarily to Texas, Oklahoma, and Arkansas. The objective of this study was to understand the genetic diversity of cotton fleahopper populations infesting cotton in the cotton-growing areas of the United States. Amplified fragment length polymorphism markers were used to detect genetic diversity and to characterize geographic genotypes across the distribution of the cotton fleahopper in the United States. We used 172 individuals and 559 amplified fragment length polymorphism loci in this study and found significant, but low, level of genetic differentiation among geographic populations (F(ST) = 0.02; P < 0.0001). Molecular fingerprints of cotton fleahopper populations were partitioned into three broad regional genetic populations with a western, central, and eastern distribution. The western (Arizona) and eastern (Florida, Georgia, South Carolina, and North Carolina) populations are genetically distinct, whereas the central (Texas, Oklahoma, Arkansas, Mississippi, Louisiana, and Alabama) population represents an admixed population, which include both western and eastern populations. These results suggest considerable gene flow among the populations within regions but restricted gene flow among populations from eastern and western region.

Mind the gap: racial differences in breast cancer incidence and biologic phenotype, but not stage, among low-income women participating in a government-funded screening program

Breast cancer mortality rates in South Carolina (SC) are 40 % higher among African-American (AA) than European-American (EA) women. Proposed reasons include race-associated variations in care and/or tumor characteristics, which may be subject to income effects. We evaluated race-associated differences in tumor biologic phenotype and stage among low-income participants in a government-funded screening program. Best Chance Network (BCN) data were linked with the SC Central Cancer Registry. Characteristics of breast cancers diagnosed in BCN participants aged 47-64 years during 1996-2006 were abstracted. Race-specific case proportions and incidence rates based on estrogen receptor (ER) status and histologic grade were estimated. Among 33,880 low-income women accessing BCN services, repeat breast cancer screening utilization was poor, especially among EAs. Proportionally, stage at diagnosis did not differ by race (607 cancers, 53 % among AAs), with about 40 % advanced stage. Compared to EAs, invasive tumors in AAs were 67 % more likely (proportions) to be of poor-prognosis phenotype (both ER-negative and high-grade); this was more a result of the 46 % lesser AA incidence (rates) of better-prognosis (ER+ lower-grade) cancer than the 32 % greater incidence of poor-prognosis disease (p values <0.01). When compared to the general SC population, racial disparities in poor-prognostic features within the BCN population were attenuated; this was due to more frequent adverse tumor features in EAs rather than improvements for AAs. Among low-income women in SC, closing the breast cancer racial and income mortality gaps will require improved early diagnosis, addressing causes of racial differences in tumor biology, and improved care for cancers of poor-prognosis biology.

East versus West: Organic contaminant differences in brown pelican (Pelecanus occidentalis) eggs from South Carolina, USA and the Gulf of California, Mexico

Brown pelicans (Pelecanus occidentalis) were listed as endangered in the United States in 1970, largely due to reproductive failure and mortality caused by organochlorine contaminants, such as DDT. The southeast population, P.o. carolinensis, was delisted in 1985, while the west coast population, P.o. californicus, was not delisted until 2009. As fish-eating coastal seabirds, brown pelicans may serve as a biomonitors. Organic contaminants were examined in brown pelican eggs collected from the Gulf of California in 2004 and South Carolina in 2005 using gas chromatography/mass spectrometry (GC/MS). Contaminants were compared using all individual data as well as statistically pooled samples to provide similar sample sizes with little difference in results. Principal components analysis separated the Gulf of California brown pelican eggs from the South Carolina eggs based on contaminant patterns. The South Carolina population had significantly (P<0.05) higher levels of polychlorinated biphenyls (PCBs), chlordanes, dieldrin and mirex, while the Gulf of California eggs had higher levels of dichlorodiphenyltrichloroethanes (DDTs) and hexachlorocyclohexanes (HCHs). With the exception of dieldrin and brominated diphenyl ether (BDE) 47, this pattern was observed for mussel and oyster tissues from these regions, indicating the need for further study into the differences between east and west coast brown pelican populations and ecosystem contamination patterns.

Sex Bias in Interspecific Copulation between the Hermaphroditic Freshwater Snails,Physa acutaandP. pomilia(Physidae)

Previously-published mate-choice experiments have uncovered significant prezygotic reproductive isolation between South Carolina populations of Physa acuta (Draparnaud, 1805) and P. pomilia (Conrad, 1834). Here we report the results of similar tests returning no evidence of such barriers between an Alabama population of P. pomilia and three separate populations of P. acuta, two from Alabama and one from South Carolina. However, heterogametic copulations did demonstrate both a significant sex bias and a significant size bias. The smaller P. acuta was more likely to copulate in the male role and hence less exposed to any potential fitness decrements due to the reduced viability and sterility of the hybrids produced. Our observations on defeated mating attempts suggested that P. acuta may be more aggressive than Alabama P. pomilia in mating contests (its smaller size perhaps contributing to greater agility) and hence more likely to prevail in the male role. The absence of a sex bias in our previously-published mate-choice observations involving South Carolina P. pomilia and P. acuta may be attributable to our use of size-matched snails, which equalized the agility of the prospective copulants, thus perhaps prolonging the mating contests, and ultimately lessening the likelihood that any mating took place at all.

Conservation and genetics of the frosted flatwoods salamander (Ambystoma cingulatum) on the Atlantic coastal plain

The federally threatened frosted flatwoods salamander, Ambystoma cingulatum, occurs in isolated populations on the coastal plain of northern Florida, Georgia and South Carolina. An earlier phylogeographic study based primarily on mitochondrial DNA (mtDNA) and morphometrics demonstrated that the previously recognized species A. cingulatum contained two cryptic species, and that two distinct mtDNA clades were contained within the newly restricted A. cingulatum. However, salamanders from the northern extent of the species range in South Carolina were not previously available for analysis. Here, we used individuals from a newly discovered South Carolina breeding site to determine whether A. cingulatum from South Carolina are genetically distinct from their more southerly conspecifics. These analyses included the mitochondrial gene studied previously as well as broad geographic sampling of three rapidly evolving nuclear genes that allowed us to further investigate lineage diversification of flatwoods salamanders. The mitochondrial and nuclear results are largely congruent, yielding strong support for two distinct species of flatwoods salamanders and also two lineages within the eastern species. Further, the South Carolina specimens are closely related to other haplotypes found in eastern Georgia and Florida. Our summary of field surveys over the past 20 years indicates that this South Carolina population may be one of only three remaining in the entire Atlantic coastal plain distribution of this rare and declining amphibian species.

Geographic distribution of genetic variation among native and introduced populations of Chinese tallow tree, Triadica sebifera (Euphorbiaceae)

Invasive plants often display genetically determined variation in patterns of growth and resource allocation between native and introduced genotypes, as well as among genotypes within different regions of the introduced range. We examined patterns of genetic variation within and among native and introduced populations of the tetraploid Chinese tallow tree (Triadica sebifera, Euphorbiaceae) to determine whether nonselective evolutionary processes or the introduction history could contribute to previously observed phenotypic differences between native and introduced populations as well as among introduced populations. We used six microsatellite markers to study 12 native populations in China, 51 introduced populations in the southeastern USA, and one introduced population in Australia. Genetic diversity was greater within and among native populations than introduced populations. Within the southeastern USA, populations in Georgia and South Carolina differed substantially in their genetic composition and had greater genetic diversity than the rest of the southeastern USA. Greater genetic similarity between some populations in the native range and introduced range indicate a common provenance for Georgia and South Carolina populations that could have come from any of several western or southern Chinese populations and a different provenance for other southeastern USA populations and the Australian population, which were most similar to more northeastern Chinese populations. Differences among introduced populations in potentially adaptive traits (e.g., herbivore tolerance, herbivore resistance, growth rates) may result in part from the introduction history, in particular from differences present among source populations in the native range.