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the maxillopedia mutation have labial and maxillary palps transformed into
leg-like structures ( Figure 4.9 ). Tribolium with mutations of Cephalothorax have
the head and first thoracic segment fused and the labial palps transformed into
antennae ( Figure 4.9 ). Tribolium with prothoraxless mutations exhibit fusion of
head segments with the entire thorax, and transformation of all three pairs of
thoracic legs into antennae.
Comparative studies on the molecular evolution of genes involved in devel-
opment in additional insects provide information about the evolution of gene
families regulating development, as well as contribute to our understanding of
the basic mechanisms underlying the genetic control of development ( Davis and
Patel 2002, Roth and Hartenstein 2008, Schroder et al. 2008, Shippy et al. 2008,
Lynch et al. 2012 ).
4.17 Evo-Devo and the Revolution in Developmental Studies
“Evolutionary developmental biology,” also called “evo-devo,” recently
emerged to study the diversity of development in animal and plant forms from
an evolutionary point of view ( Pennisi and Roush 1997, West-Eberhard 1998,
Holland 1999, von Dassow and Munro 1999, Dalton 2000, Jenner 2000, Muller
2007, Brakefield 2011 ). Evo-devo combines comparative embryology, paleontol-
ogy, molecular phylogenetics, and genome analysis. The goals of evo-devo are
to understand the following ( Hall 2000 ):
l
The origin and evolution of embryonic development,
l
How modifications of development and developmental processes lead to the
production of novel features,
l
The adaptive plasticity of development in life-history evolution,
l
How ecology affects development to modulate evolutionary change, and
l
The developmental basis of homoplasy and homology.
The assumption underlying evo-devo is that analysis of the evolution of devel-
opmental stages, processes, and mechanisms will enable us to understand how
organisms, organs, tissues, cells, and genes evolve. Evo-devo successes include
learning the following ( Hall 2000 ):
l
Genes that control major developmental processes (establishment of body
plans, formation of appendages and sense organs) are shared across the
animal kingdom and arose early in metazoan evolution.
l
New knowledge of developmental mechanisms underlying the formation of
organs or major body parts has led to an understanding of the mechanisms
involved in their origin from structures in ancestral organisms.
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