PLANTS AND PEOPLE - LECTURE NOTES
Hugh D. Wilson 
Variation, Evolution, Domestication

SPECIES [basic unit] - DEFINE: 'POTENTIALLY INTERBREEDING POPULATIONS THAT ARE REPRODUCTIVELY ISOLATED FROM RELATED POPULATIONS'. DEFINED GENETICALLY IN TERMS OF 'HOME' DNA - MANY BOTANTISTS REJECT THIS APPROACH IN FAVOR OF 'STRUCTURE-BASED' SPECIES CIRCUMSCRIPTION

CLASSIFICATION - CONSERVED FAMILY NAMES - ACEAE
 
 

Taxon
Common Bean
Indian Corn
CLASS MAGNIOLOPSIDA (Dicot) LILIOPSIDA (Monocot)
SUBCLASS ROSIDAE COMMELINIDAE
ORDER FABALES CYPERALES
FAMILY FABACEAE [LEGUMINOSAE] POACEAE [GRAMINEAE]
GENUS Phaseolus Zea
SPECIES vulgaris mays
AUTHORITY L. (Linnaeus) L.

See the Flowering Plant Gateway for 3 different ways to classify - take 'browse' options

1. REVIEW FROM LAST TIME:

SUCCESS IN EVOLUTION - INCREASE NUMBERS OF INDIVIDUALS/POPULATIONS AND INCREASE GEOGRAPHIC RANGE - I.E., INCREASE THE AMOUNT, DIVERSITY, DISTRIBUTION OF 'HOME' DNA

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EVOLUTION - THINGS ARE GOOD - NO CHANGE - SELF-POLLINATION OR ASEXUAL REPRODUCTION [Apomixis - VEGETATIVE ('cloning' of various sorts - layering, rhizomes, stolons, etc.) OR FLORAL - (AGAMOSPERMY - ameiotic, asexual seed production], or minimal recombinational change via 'selfing' or inbreeding (examples) - but .....

TIMES ARE CHANGING - NEED TO TRY DIFFERENT TACKS OR, NEED TO MOVE OUT AND ESTABLISH MORE TERRITORY- MAXIMIZE VARIATION (VIA RECOMBINATION) BY OUT-CROSSING [BETWEEN PLANTS, BETWEEN POPULATIONS - BETWEEN SPECIES} - VIA IMPERFECT FLOWERS, PROTOGYNY, 'LOCK AND KEY' (Orchids, Milkweeds) pollen vectoring and animal or wind-mediated DISPERSAL MECHANISMS.

2. HYBRIDIZATION - OUT-CROSSING TO THE EXTREME - BRINGING TOGETHER 'FOREIGN' DNA - USUALLY PRODUCES BAD GENETIC COMBINATIONS, BUT SOMETIMES - HETEROSIS - CONTINUUM OF GENETIC RELATIONSHIPS - AT THE EDGE - STRENGTH BUT STERILITY - MULE - ALSO, STRENGTH AND FERILITY - HYBRID CORN BREEDING - 'INBREAD' LINES WITH CROSSES TO PRODUCE F1 HYBRID SEED FOR SALE (yield over time)

POLYPLOIDY - MAINTAINING HETEROSIS AND FERTILITY [COMMON IN PLANTS] DIPLOID 9AA+9BB = 18AB [PROBABLY STERILE], 2X [DOUBLE VIA UNREDUCED GAMETES OR SOMATIC DOUBLING] = 36 [ALLOTETRAPLOID [AABB], 9C+18AB=27 [STERILE TRIPLOID] - 2X [DOUBLE] = 54 [AABBCC - ALLOHEXAPLOID] - examples from Brassica and Triticum.

AUTOPOLYPLOIDY - MULTIPLICATION OF THE SAME OR SIMILAR GENOMES (AA X A'A'=AA' [DOUBLE] = AAA'A'

Perhaps 40% ANGIOSPERM SPECIES ARE POLYPLOID.  Why so high in plants (vs. animals)?

indeterminate pattern of growth [lack of developmental complexity, ALSO can grow till doubling occurs], perhaps some 'buffering' provided by the chloroplast genome. What is the advantage: 1) heterosis, 2) greater internal genetic diversity (more loci, alleles), 3) with one locus 'covered' the duplicated locus can 'experiment' in terms of change of function.


Return to Course syllabus
1 Feb 2011