geneflow and persistence
DESCRIPTION
Geneflow and persistence. Geoff Squire. Scottish Crop Research Institute. Concerns. Ecological feral populations or hybrids with wild relatives interfere with the habitat Food purity outcrossing between nearby fields feral populations contributing to yield. The system. - PowerPoint PPT PresentationTRANSCRIPT
Geneflow and persistence
Geoff Squire
Scottish Crop Research Institute
ConcernsEcological • feral populations or hybrids with
wild relatives interfere with the habitat
Food purity • outcrossing between nearby fields • feral populations contributing to
yield
The system
• Soil - genesis, resilience • Primary production – crops and weeds• Decomposition – bacteria, fungi,
protozoa, nematodes, collembola, etc. • Element cycling • Herbivory – nematodes, insects,
cattle/sheep + humans
The scales
• Fine soil structure – bacterial, fungal
• Field patch – plant populations• Field – management unit• Farm or group of farms• Landscape
3D View 2D View3D View 2D View
Soil is a complex medium
Oilseed rape• Reappeared as a common crop in
1970s• Most Brassica napus, some B. rapa• As a ‘break’ crop in cereals• Oil has a wide range of uses• Outcrossing (contact, wind, insect)• Feral descendents (pod shatter,
inducible dormancy)
It has joined joined the seedbank
In this small plot of 200 m-2
• 10,000 original OSR crop plants
• >100,000 seed shed at harvest
• 100 feral plants one year later
• >1000 feral seeds still in the seedbank
1 km
It has good regional coverage
1. Will it disturb the habitat?
• Soil structure • Habitat processes• Other organisms
Other arable plants
• Seedbank – 1000 to >10,000 individuals in a square metre
• 10 target weeds • 30 common, 150 less common
species• Non-target species highly valuable
to arable food web• From glacial and more recent
Common Cruciferae
Brassica napus Brassica rapa
Raphanus raphanistrum
Sinapis arvensis
0
10
20
30
40
50
0 200 400 6000
10
20
30
40
50
0 200 400 600
Will OSR affect rest of seedbank ?
Community-scale properties
Will it affect transmission through food webs ?
Ecological impact - conclusions
Ferals and hybrids -• Negligible effect on integrity of soil • Negligible effect on main habitat processes• Mainly fill vacant space – ferals typically 100
m-2
• But might alter seedbank species abundance or species composition
• And some transmission of effect to food web
2. Impurities in yield
• Distance and frequency• Persistence over time• Food quality• Perception and
preference
1 km
Distance and time?
Gene flow depends on context
f
d
2 km
Green – oilseed rape fields
Black – GM oilseed rape fields
Analysis in progress (2002)
Impurities in OSR decay slowly
0
0.2
0.4
0.6
0.8
1
0 3 6 9 12 15
time (years)
co
nta
min
ati
on
herbicide
no herbicide
Impurity in yield - conclusions
• Not preventable in oilseed rape under present arable cropping – at low frequency over several km, mediated by a range of
insect vectors and wind-borne pollen – regional process depending on the configuration of fields in a
locality – cross pollination between nearby fields is 1 in 1000 or less
(higher to fields of partial male fertility) – In-field ferals can contribute more (i.e. 1 in a 100) to
impurities
• Can be limited < 0.1% not practicable< 1% uncertain and only with the most rigorous
standards
Conclusions
Of ferals and hybrids –
• Ecological effects small
• Low level of impurity in harvest will be difficult to manage
• First conclusion might have to be modified if field practice changes