Artificial Selection on Plant
Morphology
Artificial selection
during
Crop Domestication
Kellogg et al 2007, Cur Op Pl Bio
The power of artificial selection
Human-driven evolution
Darwin used domestication as a proxy for evolution by natural selection
(pigeons and plants)
h"p://imagecache2.allposters.com/images/pf/PHD0308_f.jpg h"p://www.wsdot.wa.gov/environment/biology/usfw-­‐list/images/wolf.jpg Here is the wolf. What is the chihuahua?
http://www.first-nature.com/flowers/images/brassica_oleracea1.jpg
The range of cole vegetables domesticated from the wild cabbage,
Brassica oleracea
David R. Smyth. Flower Development: Origin of the cauliflower. null, Volume 5, Issue 4, 1995, 361–363
http://dx.doi.org/10.1016/S0960-9822(95)00072-8
Flower Development: Origin of the cauliflower
David R. Smyth
A mutant gene that is responsible for generating cauliflower-like heads in the model
laboratory plant Arabidopsis has been cloned, and the same gene has been shown to
be mutant in edible cauliflowers.
Figure 2. (a) Wild-type flowering stem (right) and the cal mutant phenotype (left) of Arabidopsis thaliana.(b) Scanning electron
micrograph of an Arabidopsis cal mutant, showing extensive proliferation of inflorescence meristems that occur in increasingly higher
order branches (photo courtesy of John Bowman)
David R. Smyth 1995, Curr. Biol.
Domestication of peppers
Bananas
Plant transcription factors have been the target of
artificial selection during crop domestication
Fruit size
Seed shattering
control
Branching
Left: Teosinte
Right: maize
Middle: teosinte,
maize hybrid
Teosinte plant
The evolutionary stages of domestication and diversification
The Effects of the Domestication
Bottleneck on Genetic Diversity
Domestication also leads to Selective sweeps: the reduction or elimination of
variation among the nucleotides in neighboring DNA of a mutation as the result
of recent and strong positive natural selection.
In-class discussion questions
J Doebley 2006 (bring paper)
1.  What type of change did the tb1 gene undergo during
the domestication of teosinte to maize?
2.  What type of change did the qSH1 gene involved in
seed shattering in rice undergo during domestication?
3.  Find an example of heterochrony in this reading and
explain it to the class.
4.  What do the mutations affecting domestication of crops
(rice, maize, wheat, tomato) discussed here have in
common?
5.  Are these examples of a “tinkering” or “crippling”
model of evolution? Explain