Brief history of domestication LECTURE 1

When hunter-gatheres started to cultivate

• Start of the Holocene

• began cultivation of plant species for

  • fibre

  • food

  • other uses

Why did they make the descision?

• Unconcious inate descisions

  • unconsciously picked ones they liked the most when hunter gathering

  • then brought seeds with them to camps

  • accidental cultivation

Cultivations reinforced by

Pleistocene→ Climate change:

Risk of decreasing food supply

• decrease available big game

• increasing human occupation of local habitats

To descrease risk of decreasing food supply

• gathered second and third choice food

• e.g species that required food preparation

→ Began intentionally transporting wild plants to productive habitats

→ began controlled cultivation and breeding

Cons of being a farmer (vs Hunter-Gatherer)

• more work

• shorter stature

• worse nutritional conditions

• more disease in societies

BUT→ has still outcompeted hunter gatherer societies today

How did farming outcompete hunter gatherer

• settle permantantly

• not mirgation

→ Explosion in human popualation

How this human population explosion caused?

1. sedentary lifestyle→ shorter birth cycles

   • babies not carried on migration= more babies

2. greater density of edible foods (compared to wild distributions

3. FURTHER led to: technology, crafts, vocation, social stratification, political centralisation, standing armies

What is domestication

• Process of speciation and/or species transformation

• occurs when one species (domesticator) controls reproduction and dispersal of

• another species (the domesticated)

  → In order to meet the needs of the domesticator (mainly fo food but could also e for e.g antibiotics or smth)

Domesticated crop species

• result of evolutionary processses

• acting at human time scales

• not geological timescales

i.e→ humans inflict selection pressures on the domesticated

What causes the evo processes of domestrication

Wild species exposed to:

1. new selective environments (natural selection)

   • associated with with practices of agriculture and cultivation

2. Selection pressures from humans

   • e.g artificial selection

How is crop domestication a mutualistic relationship a co-evolution?

1. Plant species adapted to human control and surival under human manipulation to→ enhance Human survival

2. Domestication results in increased fitness of domesticated species

   • expansion of domesticated spcies outside its normal→ enhancing domesticated species pop size and survival

What this means e.g with Wheat

Relationship is tightly bound:

• Wheat found on 218 million hecatres

  → If no wheat→ human pop decline and/or shown to have civil unrest (think of graph)

  → If no humans→ Wheat cannot thrive without cultivation

  • e.g now reliant on humans for dispersal (see loss of seed shattering below)

Plant vs animal domestication

1. 1000-2500 plant species

2. 20-31 mammal species

Why such a difference?

Non- human farmers

1. Bark beetles, termites and ants farming fungi

2. Ants farming plants

1. Non-human Domesticators→ Attine ants farming fungi

Farm fungi for food

• cultivation of fungus gardens

• Daughter queen leaves nest and carries fungus with her

• Starts new garden

  • → Crucial inter-dependence→ Shows the co-evolution→ Cannot live without eachother

E.g Attine ants→ Leaf cutter ants

• cut forest vegtation

• used as nutritional substrate for fungal gardens

When did ant farming evolve?

• 50000000 years ago

Much older than human farming

Attine ant agriculture→ with 4 separate organisms

1. Domesticator ants

2. Domesticated fungi

3. Parasitic fungus Escovopsis infect fungal gardens (pest)

4. Bacterium (symbiotic relationship with ants)→ controls the fungal pest

2. Non-human farmers: Ants farming plants

1. Plant produce domatia

   • hollow sweelings to house ants

2. ants gives plant

   • protection from predators

   • nutrients from feaces

3. Plants gives ants

   • sugary reward

E.g Ant: Philidris nagasau

Plant: Squamelleria→ epiphytic plant (grows on other plants)

How does Squamelleria work

1. extracts seeds

2. deliberately inserts them into cracks of host plant

3. germinate

4. Young plants grow→ ants protect them/ fertilise

5. EVEN the ants have shown to sow seeds on sunny side of trees→ optimise growing conditions

Origins of Domesstication

• All originated in a number of dicrete areas in the world

  → Centres of origin

Characteristics of Centres of Origin

1. high co-occurence of wild ancesters with related domesticated species

2. Show higher varietal diversity comapred to other areas

   • because those domesticated and moved to new areas, favoured varieties→ bottle-neck

   • if area didnt have had as much or less diversity→ doesn’t really show that a trait was selected for and bottle necked!

3. Long history of crop use

Centres of Origin

Spread of domesticated plants

• More rapidly on the eat-west axis

WHY:

• areas of same latitude

• identical day-lengths and seasons

• similar climates and habitats and disease

→ less evo change needed to domesticate species

→ Less technologies and practices needed

Multiple evolutionary origins of Domestication

• we grow a range of stuff that its distantly related

• But there are hotspots of domestication where crops have come from particular evolutionary lineages

• some lineages: do not contribute anything at all!

Hotspots of evo lineages

1. Order Poales→ grass and cereal (rice, wheat barley oats)

2. Order Rosales→ temperate fruit species (apple pear plum)

3. Order Fables→ legumes (beans, legumes, chickpeas)

4. Solanales→ (tomato, potato, auberine, tobacco)

Why are osme lineages of plants so rich in example of crops and domestication, whilse others there are very few?

Domestication Syndromes

Traits that have been selected for and enhanced by humans to make the plant

• more productive and nutritious

• more amenable to cultivation

This results in…

• plants that are distantly related having similar traits

Examples of domestication syndromes

Important note:

• distinct phenotypic consequences that are shared

• by domesticated plants

• regardless

• of geographical or organismal origin

More subtle selection pressures for Domestication syndromes

1. Increased seed size and fruit size Wheat

   • larger seed= sown deeper and still emerge above ground

2. Shorter and less bushy maize vs Teosinte

   • Easier to access fruit, less resource wasted growing vegetation

3. Absence oof toxins and spines→ so can eat easier

4. Sync of germination and ripening

   • cultivation happen to whole crop at once

5. Reduced seed shattering and dispersal e.g wild rice

   • Really means that plant relies on human to spread seed

     → Co evolution and inter-dependence!

6. Self fertilisation

   • Not dependent on pollinators

   • limits potential for introgression of unwanted alleles

   • ensures beneficial traits are maintained

Angiosperms are the most successful group of plants on Earth.” To what extent do you agree with this statement? What features of angiosperms have contributed to their success?

Example: Increased grain size of wheat

Example: Reduced branching of modern Maize vs Teosinte

Example: Loss of abscission zone→ wild rice

• Intentionally weakend abscission zone

• Lost

• Reduces seed dispersal

Points of domestication

Initiation:

• Domestication

  → unconscious

Propagation

• Diversification

  → evolution of the domesticated species

  • Also to different habitats

  • different traits coming into selection at different points

Stages of Domestication

1. Onset of Domestication (Initiation)

   • Plant exploitation, harvesting and stewardship

     → isolates it from wild relative

2. Increase in frequency of desired alleles

   • populations with desired alleles amplified

   • yield increases begin to be seen

   • diversity of phenotypes

3. Adaptation of pops to new environments

   • spread from centre of origin

   • now selected for even more different environments/ cultures

4. Deliberate breeding

   • different crop varieties (now that we have them from stage 3) deliberately bred to max:

     • yield, ease farming, uniformity and quality

E.g stages of Maize Domestication

1. merging distinction between

   • wild ancestor teosinte and

   • early form of Maize

2. Increases selection for desirable alleles

   • With a degree of variation (see picture)

3. Selection for different variteies by cultures

   • e.g Native Indians→ ornamental

   • e.g Peru → pop-corn

   • e.g Italy → red sweet corn

4. Modern varietal maize

   • result of dedicated breeding approaches

Other examples→ throughout stages, the traits selected for changes