Biology Reference
In-Depth Information
12.7 The Universal Tree of Life
564
12.7.1 Two Domains 564
12.7.2 Three Domains 564
12.7.3 Origin of Eukaryota 565
12.8 The Fossil Record of Arthropods 568
12.9 Molecular Analyses of Arthropod Phylogeny
571
12.9.1
Evolution of the Ecdysozoa
571
12.9.2
Relationships among the Arthropoda
571
12.9.3
The Phylogeny of the Holometabola
571
12.9.4
Congruence Between Morphology- and Molecular-Based Trees
572
12.9.5
Genomes and Arthropod Phylogenies
572
12.10 Molecular Evolution and Speciation
573
12.10.1 Species Concepts 573
12.10.2 How Many Genes are Involved in Speciation?
575
12.10.3 Detecting Cryptic Species
577
12.11 Some Conclusions
578
Relevant Journals
579
References Cited
579
12.1 Overview
Systematics is the study of phylogeny and taxonomy. Taxonomy can be divided
into descriptive taxonomy and identification. DNA and genome sequences are
suitable for systematics studies because they provide the most direct analysis of
the genetic material possible and are unlikely to be confounded by life-stage or
environmentally induced variability in morphology. Molecular techniques used
include restriction analyses of DNA sequences and DNA sequencing of genes
and entire genomes. Each method has virtues and limitations in the amount and
type of information provided, their technical difficulties, and costs.
There have been several significant controversies associated with using molec-
ular techniques to study systematics and evolution. These include debates over
the relative importance of molecular versus morphological data, the constancy
of the molecular clock for evaluating time of divergence of taxa, the proper
use of the terms homology and similarity, and the neutrality of DNA sequence
variation. Another issue is how to resolve incongruencies between molecular-
and morphology-based phylogenies and which phylogenetic method, which
evolutionary model, and which DNA sequences should be used. The immense
diversity of insects and their long evolutionary history provide challenges, espe-
cially with the analysis of deep evolutionary patterns. The availability of entire
genomes of diverse arthropods will increasingly resolve many questions. With
the use of molecular methods, evolutionary biologists and population geneti-
cists are beginning to use common approaches to study both intraspecific and
