scholarly journals Using Trees: Myrmecocystus Phylogeny and Character Evolution and New Methods for Investigating Trait Evolution and Species Delimitation (PhD Dissertation)

2008 ◽  
Author(s):  
Brian O’Meara
Keyword(s):  
Species Delimitation ◽  
Character Evolution ◽  
Trait Evolution ◽  
New Methods

Why are there species?

2019 ◽  
pp. 52-82
Author(s):  
Timothy G. Barraclough
Keyword(s):  
Reproductive Isolation ◽  
Species Delimitation ◽  
Divergent Selection ◽  
Single Locus ◽  
Whole Genome ◽  
Gene Exchange ◽  
New Methods ◽  
Genome Data ◽  
Alternative Hypotheses ◽  
Complex Models

This chapter continues the discussion of evolutionary methods of species delimitation by exploring how multilocus methods can be used to delimit reproductively isolated groups, and how genetic and trait data can be used in concert to delimit groups that experience divergent selection. These methods provide a way to evaluate the different mechanisms leading to cohesion within species and divergence between them. Multilocus data are scarcer at present than single-locus data discussed in chapter 3, and more work is needed to test alternative hypotheses for the pattern of reproductive isolation—does it generally fall into discrete units or are there broader or gradually declining rates of gene exchange? Divergent selection is less commonly used as a metric for delimiting species, and possible new methods are introduced. Possible uses of whole-genome data are discussed for combining these approaches and testing whether reproductive isolation and divergent selection tend to overlap to generate species or whether more complex models of diversity are required.

New methods for mycocalicioid fungi

2020 ◽  
Vol 52 (6) ◽  
pp. 403-413
Author(s):  
Hanna Tuovila ◽  
Seppo Huhtinen
Keyword(s):  
Species Delimitation ◽  
Morphological Characteristics ◽  
Molecular Data ◽  
Chemical Characteristics ◽  
New Methods ◽  
Single Character ◽  
Chemical Characters

AbstractThe identification of mycocalicioid species continues to be based on morphological and chemical characters, even though molecular data and substratum preferences can provide many important insights into specific problems associated with species delimitation and other taxonomic challenges. Our results reinforce the usefulness of many morphological and chemical characteristics and reveal several new features that can be used for both species delimitation and identification. Given the fact that mycocalicioid species can rarely be distinguished by just a single character, combinations of different chemical and morphological characteristics must be used. Additional characteristics must also be sought, including those that have previously been overlooked or still need to be discovered. As a result of this search, we introduce a new term, pseudohemiamyloid, for a reversible, KOH resistant/enhanced reaction in Lugol's solution.

scholarly journals Trait Evolution on Phylogenetic Networks

2015 ◽  
Author(s):  
Dwueng-Chwuan Jhwueng ◽  
Brian O'Meara
Keyword(s):  
Brownian Motion ◽  
Measurement Error ◽  
Drought Tolerance ◽  
R Package ◽  
Phylogenetic Networks ◽  
Ancestral State ◽  
Trait Evolution ◽  
New Methods ◽  
Hybridization Event ◽  
Brownian Motion Model

Species may evolve on a reticulate network due to hybridization or other gene flow rather than on a strictly bifurcating tree, but comparative methods to deal with trait evolution on a network are lacking. We create such a method, which uses a Brownian motion model. Our method seeks to separately or jointly detect a bias in trait value coming from hybridization (β) and a burst of variation at the time of hybridization (v_H) associated with the hybridization event, as well as traditional Brownian motion parameters of ancestral state (μ) and rate of evolution (σ^2) of Brownian motion, as well as measurement error of the tips (SE). We test the method with extensive simulations. We also apply the model to two empirical examples, cichlid body size and Nicotiana drought tolerance, and find substantial measurement error and a hint that hybrids have greater drought tolerance in the latter case. The new methods are available in CRAN R package BMhyd.

scholarly journals Is it time to describe new species without diagnoses?—A comment on Sharkey et al. (2021)

Zootaxa ◽  
2021 ◽  
Vol 5027 (2) ◽  
pp. 151-159
Author(s):  
DIRK AHRENS ◽  
SHANE T. AHYONG ◽  
ALBERTO BALLERIO ◽  
MAXWELL V. L. BARCLAY ◽  
JONAS EBERLE ◽  
...  
Keyword(s):  
New Species ◽  
Dna Barcoding ◽  
Species Delimitation ◽  
Large Scale ◽  
Modern Science ◽  
Biodiversity Research ◽  
New Methods ◽  
Species Descriptions

New methods in taxonomy and systematics can influence the overall practice of formally naming and describing biodiversity. DNA barcoding has been controversial since its emergence, but now, large scale species descriptions exclusively based on barcodes have created what can be called a ‘new quality of performance’. Its limitations are discussed from different perspectives: nomenclature, general pragmatism, and problems of DNA-based species delimitation in the light of the central aim of achieving a robust and stable nomenclature of organisms, essential for all applications of biodiversity research. This issue needs to be addressed to prevent restraining the progress of taxonomy and its ability to contribute to modern science.  

Replication of Wet Objects and Cells

1974 ◽  
Vol 32 ◽  
pp. 102-103
Author(s):  
S. Basu ◽  
D. F. Parsons
Keyword(s):  
Water Vapor Pressure ◽  
High Vacuum ◽  
Polystyrene Latex ◽  
Vacuum System ◽  
Saturated Water Vapor ◽  
Replication Method ◽  
New Methods ◽  
Saturated Water ◽  
Water Vapors ◽  
Intermediate Chamber

We are approaching the invasiveness of cancer cells from the studies of their wet surface morphology which should distinguish them from their normal counterparts. In this report attempts have been made to provide physical basis and background work to a wet replication method with a differentially pumped hydration chamber (Fig. 1) (1,2), to apply this knowledge for obtaining replica of some specimens of known features (e.g. polystyrene latex) and finally to realize more specific problems and to improvize new methods and instrumentation for their rectification. In principle, the evaporant molecules penetrate through a pair of apertures (250, 350μ), through water vapors and is, then, deposited on the specimen. An intermediate chamber between the apertures is pumped independently of the high vacuum system. The size of the apertures is sufficiently small so that full saturated water vapor pressure is maintained near the specimen.

A Freeze Shadow Technique for the Preparation of Soft Paint Latexes for Electron Microscopy

1977 ◽  
Vol 35 ◽  
pp. 314-315
Author(s):  
Earl R. Walter ◽  
Glen H. Bryant
Keyword(s):  
Sample Preparation ◽  
High Vacuum ◽  
Vacuum System ◽  
Latex Particles ◽  
New Methods ◽  
Diffusion Pump ◽  
Film Forming ◽  
Routine Basis ◽  
Distribution Studies ◽  
Preparation Techniques

With the development of soft, film forming latexes for use in paints and other coatings applications, it became desirable to develop new methods of sample preparation for latex particle size distribution studies with the electron microscope. Conventional latex sample preparation techniques were inadequate due to the pronounced tendency of these new soft latex particles to distort, flatten and fuse on the substrate when they dried. In order to avoid these complications and obtain electron micrographs of undistorted latex particles of soft resins, a freeze-dry, cold shadowing technique was developed. The method has now been used in our laboratory on a routine basis for several years.The cold shadowing is done in a specially constructed vacuum system, having a conventional mechanical fore pump and oil diffusion pump supplying vacuum. The system incorporates bellows type high vacuum valves to permit a prepump cycle and opening of the shadowing chamber without shutting down the oil diffusion pump. A baffeled sorption trap isolates the shadowing chamber from the pumps.

Directional observation on lipid of male nectary of Lindera megaphylla hemsl. by the rapid embedding method with polyethylene glycol (PEG)

1990 ◽  
Vol 48 (3) ◽  
pp. 718-719
Author(s):  
Dai Dalin ◽  
Guo Jianmin
Keyword(s):  
Electron Microscope ◽  
Polyethylene Glycol ◽  
Chemical Reaction ◽  
Traditional Method ◽  
Osmium Tetroxide ◽  
Unsaturated Lipid ◽  
Embedding Method ◽  
Long Period ◽  
New Methods

Lipid cytochemistry has not yet advanced far at the EM level. A major problem has been the loss of lipid during dehydration and embedding. Although the adoption of glutaraldehyde and osmium tetroxide accelerate the chemical reaction of lipid and osmium tetroxide can react on the double bouds of unsaturated lipid to from the osmium black, osmium tetroxide can be reduced in saturated lipid and subsequently some of unsaturated lipid are lost during dehydration. In order to reduce the loss of lipid by traditional method, some researchers adopted a few new methods, such as the change of embedding procedure and the adoption of new embedding media, to solve the problem. In a sense, these new methods are effective. They, however, usually require a long period of preparation. In this paper, we do research on the fiora nectary strucure of lauraceae by the rapid-embedding method wwith PEG under electron microscope and attempt to find a better method to solve the problem mentioned above.

Confronting the grey zone after severe brain injury

2019 ◽  
Vol 3 (6) ◽  
pp. 707-711 ◽  
Author(s):  
Andrew Peterson ◽  
Adrian M. Owen
Keyword(s):  
Brain Injury ◽  
Ethical Issues ◽  
Vegetative State ◽  
Clinical Care ◽  
Grey Zone ◽  
Severe Brain Injury ◽  
New Methods ◽  
Legal Decision Making ◽  
Technological Developments ◽  
The Brain

In recent years, rapid technological developments in the field of neuroimaging have provided several new methods for revealing thoughts, actions and intentions based solely on the pattern of activity that is observed in the brain. In specialized centres, these methods are now being employed routinely to assess residual cognition, detect consciousness and even communicate with some behaviorally non-responsive patients who clinically appear to be comatose or in a vegetative state. In this article, we consider some of the ethical issues raised by these developments and the profound implications they have for clinical care, diagnosis, prognosis and medical-legal decision-making after severe brain injury.

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