lecture 7 : pathways for plant domestication Flashcards
PREREQUISITES: Biological
Annual self-propagating plants
Adequate variation in wild population
Availability of cultivatable land
Prerequisites: Cultural
Need or desire to be fulfilled
Technology or lifestyle pattern to accommodate domestication
some defenitions
Gathering: people
gathered plants from wild stands;
Cultivation: wild plants
systematically sown in fields of choice;
repetitive cycle of sowing, collecting and sowing gives rise to ‘domestication syndrome’.
Agriculture: when
communities are dependent upon
domesticated plants for the bulk of their diet, and where cultivating
plants forms the basis of subsistence and economy. - after some time of cultivation
important
PLANT PATHWAYS TO
DOMESTICATION
- Cereal
- Weeds
- Tubers
- Ecosystem Engineered
- Tree fruit
- Directed fiber
1.Cereal Pathways
ex: wheat
Results from repeated planting and harvesting of wild seeds
Domestication syndrome largely results from unconscious selection
Mutualistic relationship results in labour traps (ratchet effect)
Slow, protracted process (1000s years to achieve fully domestic
DOMESTICATION
SYNDROME -
CEREALS
1.Loss of seed dispersal
(non-dehiscent)
-
Loss of grain dispersal aids
(awns, hooks, hairs) - Increase in seed size and number
-
Plant architecture (apical
dominance) - uses less space so people can plant more cereals around them -
Timing of reproduction
(simultaneous germination &
ripening) - certain types of the year it is expected for these cereals to grow so they grow together
CEREALS–SEEDSIZE
Larger seeds have a competitive advantages
- head-start light and space
Unconscious selection resulting from
deliberate planting
- Larger seeds with thinner seed coat germinate more quickly
Selection pressure is not very strong
- Slow, steady change over millennia
CHANGES IN
REPRODUCTION
Loss of seed dormancy, simultaneous germination
and ripening driven by unconscious selection
Increases likelihood of being
planted the following year
More difficult to track in the
archaeological record
NON-SHATTERING MUTATION
Previously thought to have changed rapidly under selection
Archaeological data indicates slow fixation of trait (millennia)
Why did domestication take so long?
- Re-occurrent gene flow between wild
and cultivated crops?
- Relatively weak selection for non-shattering types
-Harvesting before full maturity
-Strong selection only with sickle use(tool)
APICAL
DOMINANCE - Plant architecture
May be associated with fertilized and managed crops
Soil improvement may result in tall, productive, less bushy plants
Could occur later in the domestication process
Role of conscious selection
ADAPTIVE
INTROGRESSION
crossing wild and domestic cereals
Hybridization with wild crops is important in cereal pathway
Aids in crop diversification–
increases variation
Adaptation to new
agricultural environments
4 LESSONS
LEARNED
LATELY
- Cereal domestication is
protracted - Early domestication driven in
large part by unconscious
selection - Hybridization is important in the
spread of domestic crops - Parallel genetic evolution is
common (convergent evolution)
2.WEED
PATHWAY
ex:oat,rye,Eggplant,Wild mustard, Chilis
Squash family
- plants that because they they trive in simmilar enviroments as cereals they also end up being domesticated - very uncousius
CEREALS - VAVILOVIAN MIMICRY
Weedsevolveoneormore
shared characteristics
withdomesticated
cropsthroughartificial
selection
Unconscious selection by
humans:
Involves Model (domestic
plant), Mimic (weed), Dupe
(humans)
OAT
DOMESTICATION
Wild species widely
distributed
Unconscious selection
promotes increase in
seed size and tough
rachis mutations
Crop adapted to cooler,
temperate climates
RYE DOMESTICATION
Wild rye widely distributed in
Mediterranean
Originally a weed in wheat and barely fields
Perennial plant -> selection for mutants that set seed.
Unconscious selection increases fitness
Results in new crop
Thrives on poor soil, enhances water
penetration, reduces soil erosion
CAMP FOLLOWING WEEDS
Humans collect plants from distinct
environments and bring them to camps (e.g., floodplains)
Some seeds colonize and thrive in disturbed soils around the camp
Eventually are deliberately cultivated
- Domestication often occurs outside of wild range
- Examples: Andean tomatoes, Eastern US sunflower
**Domestication syndrome: **
- Increase in edible portion, loss of seed dormancy
3.TUBER
PATHWAYS
ex:potatoes,sweet potatoes, cassava, ginger, turmeric, taro
Focus on short cycle ecosystem
management
- Humans become dispersers and
propagators
Unconscious selection:
- Landscapemodification–clearing,
burning
- Soildisturbance–looseness,friability
Conscious selection:
- Direct selection for favoured
phenotypes through vegetative
propagation(clones)–planting,
translocations
Rapid Selection for:
Ease of growth & productivity
Hardiness and resistance to stress;
Ease of processing and cooking
Toxicity, acridity, palatability; colour,
texture
Domestication syndrome:
Loss of sexual reproduction; edible
yield, harvesting, timing of production;
plant architecture; loss of defenses.
High phenotypic plasticity - be able to adpt
Timing:
Can be very rapid selection and fixation of desired traits
Sexual recombination with wild types
can allow adaptation to new
environments
Difficult to document domestication
Few morphological markers preserve
Starch grains differ in size and
morphology in domestic types
Phytoliths‘silicabodies’display
morphological variation
HOW ARE PLANT AND ANIMAL PATHWAYS
overlap?
- cereal and commensal - unconsious domestication
- weed and prey- unconsious domestication
- tuber and direct - consencious domestication
- ECOSYSTEM
ENGINEERING
ex: Areca Nut Palm, Rubber tree
Olive trees,(a lot of threes are)
Arboriculture: Promoting survival of long-lived trees
**Techniques: **Land clearance, burning, planting, fertilization, pest and pathogen control, pruning, shaping, plant protection (ownership/stewardship)
Landscapemanagementratherthan‘domestication’
Domestication syndrome:
May reflect little to no morphological change
Pollen cores may display changes in vegetation & ecology
Change in fruit/nut/kernel size
OIL PALM
ARBORICULTURE
Oil palm use extends over 5000 years
Arboriculture may extend to 3600-3200 BP by Kintampo culture of Ghana (‘forager-farmers’)
Mayhavestartedas‘camp-follower’
Semi-sedentary lifestyle allows for
‘ownership’oflong-lived,productive
stands
- Bear fruit after 5 years, fully mature
at 12 years
