Transcript Indicators of change

Measuring and predicting
change
in crop wild relative species
by Toby Hodgkin and Jozef Turok
International Plant Genetic Resources Institute
(IPGRI), Rome, Italy
What is a crop wild relative?
• Self- and out-pollinating annuals
• Grassland species
• Temperate forest trees
(angiosperms, gymnosperms)
• Weedy species
• Rare, mountain endemic plants
Large variation in the
characteristics…
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Distribution extent and pattern
Longevity
Life form
Habitat
Are crop wild relative species different
with respect to change, erosion and
pollution?
Pollution
• Substantial gene flow from cultivated
species to primary genepool species,
which are fully inter-fertile, occur
together and overlap in flowering
period
• Examples: Hordeum spontaneum,
Oryza rupifogon, Teosinte,
Pennisetum, Beta maritima
Conservation objectives
• Conservation of the full amplitude of
variation within a species
• Conservation of specific traits (frost or
drought resistance)
Change
• Erosion and genetic pollution
• Global changes of the environment
• Effects of the global climate change on
crop wild relative species
• Factors and processes of evolutionary
change
• Methods to assess change
Dispersal capability
• Depends on seed biology and vector
of dispersal
• For long-term survival of a species
under global climate change, the
dispersal capability must be greater
than the speed of environmental
change
Inter-population differentiation
Constraints
Natural
selection
Genetic
drift
Promoters
Eriksson (2003)
Factors and processes
of evolutionary change
•
Natural selection
•
Genetic drift
•
Mutation
•
Gene flow
•
Mating system and recombination
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Phenotypic plasticity
Phenotypic plasticity
20
Change of survival, %
10
Norm of
reaction
0
Phenotypic
plasticity
–10
–20
–30
+3
+2
northwards
+1
0
–1
–2
Latitudinal transfer
–3
–4
–5
southwards
Eriksson (2003)
Indicators of change
Indicator taxa:
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Utility value or known ecological significance
Existence value, for species under threat of extinction
Value for species known to be paradigms of a large
class of species
Indicators of genetic variation:
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Easy to implement, based on good experimental
design, indicate processes and flows, give early
warnings, have clear objectives
Application of population genetics – conservation of
the processes that maintain current genetic variation
Namkoong et al. (2002); McKenney et al. (1994)
Indicators of change
1. Number of sub-specific taxa
2. Population size and physical location
3. Environmental amplitude of populations
4. Genetic diversity at marker loci within
individuals and populations
5. Quantitative genetic variation
6. Inter-population genetic structure
7. Mating system
Brown et al. (1997)
Indicators of change
Criterion: Conservation of the processes
that maintain genetic variation
1. Levels of genetic variation
2. Directional change in gene or
genotype frequencies
3. Gene migration between populations
4. Reproductive processes/ mating
system
Namkoong et al. (2002)
Gene flow
Raybould et al. (1996)
Genetic erosion
“The loss of genetic diversity, in a particular
location and over a particular period of
time, including the loss of individual genes
(alleles), and the loss of particular
combinations of genes such as those
manifested in landraces or varieties. It is
thus a function of change of genetic
diversity over time.”
FAO (GDEV paper prepared for 9th Session of
CGRFA, 2002)
Genetic erosion – measurement and
monitoring
Characteristics of species
populations
everywhere
Geographic
distribution
local
Population size
Large/
Small/
abundant
sparse
Genetic pollution
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Exotic species (crops, forages and forest
trees)
Artificial hybrids (Populus, Brassica
napus)
Exotic provenances (crops, forages and
forest trees)
Artificially selected plants (mainly forest
trees and forages)
GMOs (mainly crops such as cotton,
maize, Brassica, soybean relatives)
Potts et al. (2001)
Pollution – why does it matter?
• Loss or disruption of adaptive gene
complexes
• Introduction of “domestication genes” and
therefore loss of natural survival capacities
• Increase of susceptibility to pests
• Loss of out-breeding characteristics (thus
inbreeding depression)
• Vigor loss in hybrids
• Increase in weedy habit
Genetically modified organisms
• Vigor and likelihood of out-crossing (e.g.
through spread of crop to new areas)
• The genes themselves – herbicide
resistance, pest resistance
• Disruption of pollinator and plant
communities
Transgene escape
• Plant containing it persists after harvesting
in an agricultural or disturbed habitat or
invades a natural habitat
• Transgene is transferred by pollination to
another crop which persists in an
agricultural, disturbed or natural habitat
• Transgene is transferred by pollination to a
related wild plant which persists in
agricultural habitats, disturbed habitats or
natural habitats
Raybould and Gray (1993)
Potential indicators
• Existence of crop wild relatives in area
(numbers and relationships)
• Viability and fertility of progeny
• Breeding system and extent of synchrony
of flowering; presence of pollinators
• Extent to which subsequent generations
can remain fertile and backcross
• Migration selection balance for transgene
Gepts and Papa (2003)
Conclusions
• Sufficient genetic variation
within species
• Criteria and indicators:
baseline data to show trends
• Important measurements,
methods
• Early warning
• Trans-national monitoring
and policy advice