Wild-Crop-Weed Complexes

Weed Origins

Read:  
Origins of Weeds:  DeWet, J.M.J. 1966. The origin of weediness in plants. Proc. of the Okla. Acad. of Sci. 47:14-17 [.pdf]

Wild plants that became weeds with the advent of agriculture
        Where do weeds come from?  
        How long have we had weeds?     

Plant pre-history:
458 million years ago            Ordovician Period            1^st land plants
428 million years ago            Silurian Period                  Cooksonia, one of first land plant species found
60-140 million years ago       Cretaceous Period            1^st flowering plants, angiosperms
10,000 B.P.                          Recent Epoch                   Human agriculture: 1^st weeds

Weeds started 10,000 B.P., with human Ag which resulted over time in wild-crop-weeds plant complexes.  

Examples of wild-crop-weed plant complexes of species: 
-sunflowers, Helianthus
-amaranthus, pigweeds, Amaranth
-foxtails, foxtail millet, korali
-mustards, Brassica hort crops, rapeseed
-oats
-lambsquarters
-rice, red rice
-barley, foxtail barley, hordeum weeds
-sorghum, johnsongrass, almum grass, shattercane
-Solanum spp.: nightshades and potatoes

    The species lines are fuzzy within a particular w-c-w group due to gene flow and introgression, and this fuzziness varies between different w-c-w groups.     
    Some pre-human wild colonizing species possessed pre-adaptations that made them ideal weeds with the introduction of agriculture.  Some other wild colonizing species were not as good as weed colonizers with the advent of agriculture as before.   Pre-agriculture wild colonizing broken into 2 groups with advent of Ag:

• wild plants that thrived in human selected disturbed habitats (agriculture) and therefore became successful weeds that we have today; formed wild-crop-weed complexes

• wild species whose colonizing pre-adaptatations were not selected for, they were not as fit, and therefore did not thrive in agricultural habitats

©jdekker-2005