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Related Concept Videos

Phylogeny01:23

Phylogeny

Phylogeny is concerned with the evolutionary diversification of organisms or groups of organisms. A group of organisms with a name is called a taxon (singular). Taxa (plural) can span different levels of the evolutionary hierarchy. For instance, the group containing all birds is a taxon (comprising the class Aves), and the group of all species of daisies (the genus Bellis) is a taxon. Phylogenies can likewise include just one genus (i.e., depict species relationships) or span an entire...
Phylogenetic Trees03:21

Phylogenetic Trees

Phylogenetic trees come in many forms. It matters in which sequence the organisms are arranged from the bottom to the top of the tree, but the branches can rotate at their nodes without altering the information. The lines connecting individual nodes can be straight, angled, or even curved.The length of the branches can depict time or the relative amount of change among organisms. For instance, the branch length might indicate the number of amino acid changes in the sequence that underlies the...
Gene Evolution - Fast or Slow?02:05

Gene Evolution - Fast or Slow?

The genomes of eukaryotes are punctuated by long stretches of sequence which do not code for proteins or RNAs. Although some of these regions do contain crucial regulatory sequences, the vast majority of this DNA serves no known function. Typically, these regions of the genome are the ones in which the fastest change, in evolutionary terms, is observed, because there is typically little to no selection pressure acting on these regions to preserve their sequences.
In contrast, regions which code...
Evolutionary Relationships through Genome Comparisons02:54

Evolutionary Relationships through Genome Comparisons

Genome comparison is one of the excellent ways to interpret the evolutionary relationships between organisms. The basic principle of genome comparison is that if two species share a common feature, it is likely encoded by the DNA sequence conserved between both species. The advent of genome sequencing technologies in the late 20th century enabled scientists to understand the concept of conservation of domains between species and helped them to deduce evolutionary relationships across diverse...
Phylogenetic Trees03:21

Phylogenetic Trees

Phylogenetic trees come in many forms. It matters in which sequence the organisms are arranged from the bottom to the top of the tree, but the branches can rotate at their nodes without altering the information. The lines connecting individual nodes can be straight, angled, or even curved.The length of the branches can depict time or the relative amount of change among organisms. For instance, the branch length might indicate the number of amino acid changes in the sequence that underlies the...
Microbial Phylogeny01:28

Microbial Phylogeny

Understanding the evolutionary relationships among microorganisms is fundamental to microbial ecology and taxonomy. Phylogenetic trees are essential tools for inferring these relationships, relying primarily on comparative analyses of molecular sequences such as DNA, RNA, or proteins. In microbial studies, these trees typically depict the evolutionary paths of diverse bacterial and archaeal species by mapping genetic differences accumulated over time.Phylogenetic trees are composed of tips,...

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A Practical Guide to Phylogenetics for Nonexperts
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A Practical Guide to Phylogenetics for Nonexperts

Published on: February 5, 2014

Molecular phylogenetics and evolution of turtles.

James G Krenz1, Gavin J P Naylor, H Bradley Shaffer

  • 1Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, 50011-3223, USA.

Molecular Phylogenetics and Evolution
|June 21, 2005
PubMed
Summary

New research uses the recombination activase gene 1 (RAG-1) to clarify turtle evolutionary history. This molecular data provides higher support for some relationships and challenges others, aiding conservation efforts for this imperiled group.

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Area of Science:

  • * Herpetology and evolutionary biology.
  • * Molecular phylogenetics and comparative genomics.

Background:

  • * Turtles possess a rich fossil record spanning over 200 million years, yet their evolutionary relationships (phylogeny) have key uncertainties.
  • * Understanding turtle phylogeny is crucial for conservation, especially given that many turtle species are globally imperiled.

Purpose of the Study:

  • * To resolve uncertain phylogenetic nodes in turtle evolution.
  • * To assess the utility of the nuclear recombination activase gene 1 (RAG-1) for phylogenetic analysis.
  • * To investigate the evolutionary relationships between Platysternidae and Chelydridae.

Main Methods:

  • * Sequencing of over 90% of the RAG-1 gene for 24 species representing all modern turtle families.
  • * Phylogenetic analyses using maximum parsimony, maximum likelihood, and Bayesian methods.
  • * Comparison of molecular data with existing morphological evidence.

Main Results:

  • * RAG-1 gene sequencing provided robust phylogenetic support for many known turtle relationships.
  • * The RAG-1 data indicated that Platysternidae and Chelydridae are not closely related, contrary to some morphological interpretations.
  • * Conflicting results emerged between analytical methods: maximum parsimony suggested three basal splits, while maximum likelihood and Bayesian analyses supported the traditional grouping of softshell and pig-nosed turtles (Trionychoidae) within Cryptodira.

Conclusions:

  • * The RAG-1 gene is a valuable tool for resolving turtle phylogeny, offering high support for critical evolutionary nodes.
  • * Molecular data can identify potential homoplasies or inaccuracies in morphological datasets.
  • * The study provides insights into the evolutionary history of turtles, aiding biodiversity research and conservation strategies for this vulnerable group.