Movin\u27 & Groovin\u27 Salamanders: Conservation Implications of Large Scales and Quirky Sex

Mole salamanders (Ambystoma) and woodfrogs (Lithobates sylvaticus) are abundant in New England and depend on ephemeral wetlands for breeding. Their aquatic habitats have been well studied and are protected by several local and regional regulations. State endangered species laws also protect mabled salamanders (A. opacum), Jefferson salamanders (A. jeffersonianum), and blue-spotted salamanders (A. laterale). However, these amphbibians spend most of their adult lives in terrestrial habitats that remain poorly protected and elusive to researchers. In chapter 1, I developed a novel technique using passive integrated transponders for tracking small animals. I used this technique to track marbled salamanders walking up to 200 m from their breeding pond during post-breeding migrations. In Chapter 2, I examined the importance of multiple habitat variables for predicting the distributions of woodfrogs and spotted salamanders at 455 ponds in western Massachusetts. Based on a variable-comparison technique I developed, the best predictor for either species of amphibian was the amount of forest in the surrounding vii landscape. Both species were found more frequently in upland forests where the ponds are least protected by state and federal wetland regulations. In chapter 3, I used my data from chapter 2 and three other similar data sets to conduct an analysis of spatial scale and to parameterize a recently published resistant kernel model. The complex model parameterized by an expert panel did significantly worse than the null model. The distributions of both amphibians were best predicted by measuring the landscape at very large scales (over 1000 m). The most effective scales for conservation may be largest for organisms of intermediate dispersal capability. In chapter 4, I explored the evolution and genetics of the Jefferson/blue-spotted/unisexual salamander complex. I framed research into the fascinating unisexual reproductive system with a model that relates nuclear genome replacement, positive selection on hybrids, and biogeography of the species complex. I parameterized this model using genetic data taken from salamanders spanning Massachusetts and an individual-based breeding simulation. If paternal genomes are transmitted to offspring with the frequencies reported from laboratory experiments, then my model suggests that there must be strong selection favoring unisexuals with hybrid nuclei

Ramification conjecture and Hirzebruch's property of line arrangements

The ramification of a polyhedral space is defined as the metric completion of the universal cover of its regular locus. We consider mainly polyhedral spaces of two origins: quotients of Euclidean space by a discrete group of isometries and polyhedral metrics on the complex projective plane with singularities at a collection of complex lines. In the former case we conjecture that quotient spaces always have a CAT[0] ramification and prove this in several cases. In the latter case we prove that the ramification is CAT[0] if the metric is non-negatively curved. We deduce that complex line arrangements in the complex projective plane studied by Hirzebruch have aspherical complement.Comment: 19 pages 1 figur

A validation study of students' end comments: Comparing comments by students, a writing instructor, and a content instructor

In order to include more writing assignments in large classrooms, some instructors have been utilizing peer review. However, many instructors are hesitant to use peer review because they are uncertain of whether students are capable of providing reliable and valid ratings and comments. Previous research has shown that students are in fact capable of rating their peers papers reliably and with the same accuracy as instructors. On the other hand, relatively little research has focused on the quality of students' comments. This study is a first in-depth analysis of students' comments in comparison with a writing instructor's and a content instructor's comments. Over 1400 comment segments, which were provided by undergraduates, a writing instructor, and a content instructor, were coded for the presence of 29 different feedback features. Overall, our results support the use of peer review: students' comments seem to be fairly similar to instructors' comments. Based on the main differences between students and the two types of instructors, we draw implications for training students and instructors on providing feedback. Specifically, students should be trained to focus on content issues, while content instructors should be encouraged to provide more solutions and explanations

Searching for Hyperbolicity

This is an expository paper, based on by a talk given at the AWM Research Symposium 2017. It is intended as a gentle introduction to geometric group theory with a focus on the notion of hyperbolicity, a theme that has inspired the field from its inception to current-day research

The asymptotic quasi-stationary states of the two-dimensional magnetically confined plasma and of the planetary atmosphere

We derive the differential equation governing the asymptotic quasi-stationary states of the two dimensional plasma immersed in a strong confining magnetic field and of the planetary atmosphere. These two systems are related by the property that there is an intrinsic constant length: the Larmor radius and respectively the Rossby radius and a condensate of the vorticity field in the unperturbed state related to the cyclotronic gyration and respectively to the Coriolis frequency. Although the closest physical model is the Charney-Hasegawa-Mima (CHM) equation, our model is more general and is related to the system consisting of a discrete set of point-like vortices interacting in plane by a short range potential. A field-theoretical formalism is developed for describing the continuous version of this system. The action functional can be written in the Bogomolnyi form (emphasizing the role of Self-Duality of the asymptotic states) but the minimum energy is no more topological and the asymptotic structures appear to be non-stationary, which is a major difference with respect to traditional topological vortex solutions. Versions of this field theory are discussed and we find arguments in favor of a particular form of the equation. We comment upon the significant difference between the CHM fluid/plasma and the Euler fluid and respectively the Abelian-Higgs vortex models.Comment: Latex 126 pages, 7 eps figures included. Discussion on various forms of the equatio

Projecting Global Mangrove Species and Community Distributions under Climate Change

Given the multitude of ecosystem services provided by mangroves, it is important to understand their potential responses to global climate change. Extensive reviews of the literature and manipulative experiments suggest that mangroves will be impacted by climate change, but few studies have tested these predictions over large scales using statistical models. We provide the first example of applying species and community distribution models (SDMs and CDMs, respectively) to coastal mangroves worldwide. Species distributions were modeled as ensemble forecasts using BIOMOD. Distributions of mangrove communities with high species richness were modeled in three ways: as the sum of the separate SDM outputs, as binary hotspots (with >3 species) using a generalized linear model, and continuously using a general boosted model. Individual SDMs were projected for 12 species with sufficient data and CDMs were projected for 30 species into 2080 using global climate model outputs and a range of sea-level rise projections. Species projected to shift their ranges polewards by at least 2 degrees of latitude consistently experience a decrease in the amount of suitable coastal area available to them. Central America and the Caribbean are forecast to lose more mangrove species than other parts of the world. We found that the extent and grain size, at which continuous CDM outputs are examined, independent of the grain size at which the models operate, can dramatically influence the number of pseudo-absences needed for optimal parameterization. The SDMs and CDMs presented here provide a first approximation of how mangroves will respond to climate change given simple correlative relationships between occurrence records and environmental data. Additional, precise georeferenced data on mangrove localities and concerted efforts to collect data on ecological processes across large-scale climatic gradients will enable future research to improve upon these correlative models.Organismic and Evolutionary Biolog

Short run cost functions for Class II railroads / BEBR No.321

Includes bibliographical references

Abelian subgroups of Garside groups

In this paper, we show that for every abelian subgroup $H$ of a Garside group, some conjugate $g^{-1}Hg$ consists of ultra summit elements and the centralizer of $H$ is a finite index subgroup of the normalizer of $H$. Combining with the results on translation numbers in Garside groups, we obtain an easy proof of the algebraic flat torus theorem for Garside groups and solve several algorithmic problems concerning abelian subgroups of Garside groups.Comment: This article replaces our earlier preprint "Stable super summit sets in Garside groups", arXiv:math.GT/060258

Measurement of the electron electric dipole moment using GdIG

A new method for the detection of the electron edm using a solid is described. The method involves the measurement of a voltage induced across the solid by the alignment of the samples magnetic dipoles in an applied magnetic field, H. A first application of the method to GdIG has resulted in a limit on the electron edm of 5E-24 e-cm, which is a factor of 40 below the limit obtained from the only previous solid-state edm experiment. The result is limited by the imperfect discrimination of an unexpectedly large voltage that is even upon the reversal of the sample magnetization.Comment: 10 pages, 5 figures, v2:references corrected, submitted to PRL, v3:added labels to figure

Garside and quadratic normalisation: a survey

Starting from the seminal example of the greedy normal norm in braid monoids, we analyse the mechanism of the normal form in a Garside monoid and explain how it extends to the more general framework of Garside families. Extending the viewpoint even more, we then consider general quadratic normalisation procedures and characterise Garside normalisation among them.Comment: 30 page