Molecular phylogenetics of the North American snake tribe Thamnophiini

Advancements in phylogenetic theory and methodology coupled with improvements in computational and sequencing technology facilitate study of the divergence and diversification patterns of life. I apply our current understanding to further explore the relationships and evolution of the North American snake tribe Thamnophiini, as well as to address current topics in phylogenetic and taxonomic methodology. There are two paradigms for the phylogenetic analysis of multi-locus sequence data: one which forces all genes to share the same underlying history, and another that allows genes to follow idiosyncratic patterns of descent from ancestral alleles. The first of these approaches (concatenation) is a simplified model of the actual process of genome evolution while the second (species-tree methods) may be overly complex for histories characterized by long divergence times between cladogenesis. Rather than making an a priori determination concerning which of these phylogenetic models to apply to our data, I seek to provide a framework for choosing between concatenation and species-tree methods that treat genes as independently evolving lineages. In Chapter 2 I demonstrate that parametric bootstrapping can be used to assess the extent to which genealogical incongruence across loci can be attributed to phylogenetic estimation error, and demonstrate the application of our approach using an empirical dataset from 10 species of the Natricine snake sub-family. Since our data exhibit incongruence across loci that is clearly caused by a mixture of coalescent stochasticity and phyogenetic estimation error, we also develop an approach for choosing among species tree estimation methods that take gene trees as input and those that simultaneously estimate gene trees and species trees. Ideally, existing taxonomy would be consistent with phylogenetic estimates derived from rigorously analyzed data using appropriate methods. In Chapter 3 I present a multi-locus molecular analysis of the relationships among nine genera in the North American snake tribe Thamnophiini in order to test the monophyly of the crayfish snakes (genus Regina) and the earth snakes (genus Virginia). Sequence data from seven genes were analyzed to assess relationships among representatives of the nine genera by performing multi-locus phylogeny and species tree estimations, and we performed constraint-based tests of monophyly of classic taxonomic designations on a gene-by-gene basis. Estimates of species trees demonstrate that both genera are paraphyletic, and this inference is supported by a concatenated tree. This finding was supported using gene tree constraint tests and Bayes factors, where we rejected the monophyly of both the crayfish snakes (genus Regina) and the earth snakes (genus Virginia). Progress in our understanding of molecular evolution necessitates a more thorough assessment of the phylogeny of thamnophiine snakes, whose relationships have not been fully resolved, and whose previous phylogenetic estimates are based solely on mitochondrial sequence data. In Chapter 4, I present the most data and taxa robust phylogenetic estimate of Thamnophiini to date, including 50 taxa and sequence data from 8 independently sorting loci. Our findings support the taxonomic recommendations proposed in Chapter 3. Additionally, I estimated the timing of divergence among the three major lineages to have occurred during the Miocene period (~14-11MYA), with higher than expected diversification in the garter snaked during the Pliocene period (~2-6MYA). Finally, we demonstrate that prey choice is labile, and thus an unreliable character for phylogeny reconstruction. Combined, these chapters present a thorough examination of the molecular phylogenetics of thamnophiine snakes. The novel methodological approaches may serve as a guideline for future research. Through estimating a robust phylogeny and suggesting taxonomic changes where appropriate, this work provides a foundation for phylogenetically-based studies of this group

Testing monophyly without well-supported gene trees: evidence from multi-locus nuclear data conflicts with existing taxonomy in the snake tribe

a b s t r a c t Ideally, existing taxonomy would be consistent with phylogenetic estimates derived from rigorously analyzed data using appropriate methods. We present a multi-locus molecular analysis of the relationships among nine genera in the North American snake tribe Thamnophiini in order to test the monophyly of the crayfish snakes (genus Regina) and the earth snakes (genus Virginia). Sequence data from seven genes were analyzed to assess relationships among representatives of the nine genera by performing multilocus phylogeny and species tree estimations, and we performed constraint-based tests of monophyly of classic taxonomic designations on a gene-by-gene basis. Estimates of concatenated phylogenies demonstrate that neither genera are monophyletic, and this inference is supported by a species tree estimate, though the latter is less robust. These taxonomic findings were supported using gene tree constraint tests and Bayes Factors, where we rejected the monophyly of both the crayfish snakes (genus Regina) and the earth snakes (genus Virginia); this method represents a potentially useful tool for taxonomists and phylogeneticists when available data is less than ideal

Recruiting long-term healthcare missionaries: insights from surveys of those who have gone and those who aspire to go

Background: The CMDA/MedSend Healthcare Missions Leadership Summit is an annual gathering of leaders from 75 mission sending agencies who work around the world in healthcare missions. The summit is jointly sponsored by MedSend and the Christian Medical & Dental Associations (CMDA). The purpose of the meeting is to share best practices, network, and examine cutting edge research issues in the field of healthcare missions. Objective: The purpose of the 2015 Launch survey was to learn from medical missionaries how to more effectively recruit and launch new healthcare professionals and their families into long-term missions. The objective of the 2016 Relocating for the Gospel survey was to learn from students and other aspiring healthcare missionaries the obstacles they perceive in their journey into long-term missions. Results were presented at the 2015 and 2016 Healthcare Missions Leadership Summits. Methods: Two multiple-choice surveys were developed to ascertain the positive and negative factors involved in the decision making process to launch into the healthcare mission field. Participants were invited to participate in the surveys via email. Results: The 2015 Launch survey analyzed 177 responses from healthcare missionaries with 63% of respondents still currently serving as long-term missionaries. 37% of the respondents were missionaries previously. Participants included millennials (n=39), Gen Xers (n=54), and baby boomers (n=84). Responses indicated that key positive factors include personal interaction with a long-term worker as well as a supportive agency, leader, or team to join. The 2016 Relocating for the Gospel survey analyzed responses from students and other aspiring missionaries who are millennials (n=79). The strongest overall factor that discouraged missions involvement was student loan debt. Other key obstacles include concerns over being lonely or isolated overseas, as well as difficulty in finding a good fit with a team or organization. Conclusion: The overall findings from the two surveys include four main points. First, effective launch into missions service is more relationally dependent than informationally dependent. Second, launching into missions service is more like a marathon than a sprint. Third, those who are exploring missions want to join a team so they will not feel lonely or isolated. Finally, aspiring missionaries want a placement that fits them well even if that does not match the top priorities of the agency

Origin of the eastern brownsnake, Pseudonaja textilis (Duméril, Bibron and Duméril) (Serpentes: Elapidae: Hydrophiinae) in New Guinea: evidence of multiple dispersals from Australia, and comments on the status of Pseudonaja textilis pughi Hoser 2003

Pseudonaja textilis is a widespread and common snake in eastern parts of Australia, but its distribution in New Guinea is poorly understood, and the origin of the New Guinea populations and its timing have been the subject of much speculation. Phylogenetic analysis of mitochondrial DNA sequences from three New Guinea populations of P. textilis indicates that New Guinea was colonised from two independent eastern and western migration routes most likely in the Pleistocene. One dispersal event from northern Queensland led to the populations in eastern New Guinea (Milne Bay, Oro and Central Provinces, Papua New Guinea), whereas another, from Arnhem Land to central southern New Guinea, led to the populations from the Merauke area, Indonesian Papua. The results are consistent with the effects of Pleistocene sea level changes on the physical geography of Australasia, and are thus suggestive of a natural rather than anthropogenic origin of the New Guinea populations. The taxonomic status of the New Guinean populations is discussed. Copyright © 2008 - Magnolia Press

Corporate governance, accounting and finance: a review

Free to read We review accounting and finance research on corporate governance (CG). In the course of our review, we focus on a particularly vexing issue, namely endogeneity in the relationships between CG and other matters of concern to accounting and finance scholars, and suggest ways to deal with it. Given the advent of large commercial CG databases, we also stress the importance of how CG is measured and in particular, the construction of CG indices, which should be sensitive to local institutional arrangements, and the need to capture both internal and external aspects of governance. The ‘stickiness’ of CG characteristics provides an additional challenge to CG scholars. Better theory is required, for example, to explain whether various CG practices substitute for each other or are complements. While a multidisciplinary approach to developing better theory is never without its difficulties, it could enrich the current body of knowledge in CG. Despite the vastness of the existing CG literature, these issues do suggest a number of avenues for future research