Species tree reconstruction of a poorly resolved clade of salamanders (Ambystomatidae) using multiple nuclear loci.

The analysis of diverse data sets can yield different phylogenetic estimates that challenge systematists to explain the source of discordance. The mole salamanders (family Ambystomatidae) are a classic example of this phylogenetic conflict. Previous attempts to resolve the ambystomatid species tree using allozymic, morphological, and mitochondrial sequence data have yielded different estimates, making it unclear which data source best approximates ambystomatid phylogeny and which ones yield phylogenetically inaccurate reconstructions. To shed light on this conflict, we present the first multi-locus DNA sequence-based phylogenetic study of the Ambystomatidae. We utilized a range of analyses, including coalescent-based methods of species-tree estimation that account for incomplete lineage sorting within a locus and concordance-based methods that estimate the number of sampled loci that support a particular clade. We repeated these analyses with the removal of individual loci to determine if any locus has a disproportionate effect on our phylogenetic results. Collectively, these results robustly resolved many deep and relatively shallow clades within Ambystoma, including the placement of A. gracile and A. talpoideum as the sister clade to a clade containing all remaining ambystomatids, and the placement of A. maculatum as the sister lineage to all remaining ambystomatids excluding A. gracile and A. talpoideum. Both Bayesian coalescent and concordance methods produced similar results, highlighting strongly supported branches in the species tree. Furthermore, coalescent-based analyses that excluded loci produced overlapping species-tree posterior distributions, suggesting that no particular locus--including mtDNA--disproportionately contributed to our species-tree estimates. Overall, our phylogenetic estimates have greater similarity with previous allozyme and mitochondrial sequence-based phylogenetic estimates. However, intermediate depths of divergence in the ambystomatid species tree remain unresolved, potentially highlighting a region of rapid species radiation or a hard polytomy, which limits our ability to comment on previous morphologically-based taxonomic groups.

Parallel tagged amplicon sequencing reveals major lineages and phylogenetic structure in the North American tiger salamander (Ambystoma tigrinum) species complex.

Modern analytical methods for population genetics and phylogenetics are expected to provide more accurate results when data from multiple genome-wide loci are analysed. We present the results of an initial application of parallel tagged sequencing (PTS) on a next-generation platform to sequence thousands of barcoded PCR amplicons generated from 95 nuclear loci and 93 individuals sampled across the range of the tiger salamander (Ambystoma tigrinum) species complex. To manage the bioinformatic processing of this large data set (344 330 reads), we developed a pipeline that sorts PTS data by barcode and locus, identifies high-quality variable nucleotides and yields phased haplotype sequences for each individual at each locus. Our sequencing and bioinformatic strategy resulted in a genome-wide data set with relatively low levels of missing data and a wide range of nucleotide variation. structure analyses of these data in a genotypic format resulted in strongly supported assignments for the majority of individuals into nine geographically defined genetic clusters. Species tree analyses of the most variable loci using a multi-species coalescent model resulted in strong support for most branches in the species tree; however, analyses including more than 50 loci produced parameter sampling trends that indicated a lack of convergence on the posterior distribution. Overall, these results demonstrate the potential for amplicon-based PTS to rapidly generate large-scale data for population genetic and phylogenetic-based research.

Background, expectations and beliefs of a chiropractic student population: a cross-sectional survey.

PURPOSE: Research encompassing the characteristics of chiropractic students is limited. The purpose of our study was to evaluate a current chiropractic student population enrolled at a chiropractic college concerning demographics, expectations, and beliefs. METHODS: A 44-item survey was administered to volunteer participants. Direct verbal interaction in a classroom setting to potential participants was the recruitment strategy used. Data were collected and stored on a safe network. Percentages for all responses were calculated and means were recorded where appropriate. RESULTS: A total of 664 students participated of 877 potential eligible candidates (75%). The respondents tended to be 21-25 years of age, Caucasian, and male. Most respondents expected to work in a private practice immediately following graduation and anticipated an annual income of at least $100,000 eventually. Respondents preferred the retaining of the term, "subluxation," and identified the importance of new and emerging scientific data. Additionally, respondents held the viewpoint that some non-musculoskeletal diseases can be treated effectively with spinal manipulation as a primary treatment. CONCLUSIONS: The majority of chiropractic students in our study were represented by specific demographic characteristics, and a strong favoritism toward the expectations of working in a private practice setting and earning at least $100,000 per year at some point in their career. Distinct beliefs are shared between chiropractic students and practicing chiropractors in North America, and certain aspects of students in our study are comparable to chiropractic students in similar studies.