Lecture 4 Gene+c Resources 1: ex+nc+on and crop gene+c resources BY2210 Trevor Hodkinson
Department of
Botany
Biodiversity is at risk
•  Genetic variation
A) Between
spp.
B) Within spp.
Species and variation within species are at risk
Major causes of extinction
•  Invasive species
•  Habitat loss
•  Climate/atmospheric change
Invasive species
outcompete native
species
Unintentionally or intentionally
introduced
e.g. Hogweed (Heracleum)
Rhododendron, Japanese
knotweed (Fallopia)
Extinction caused by habitat
loss expecially in biodiversity
hot spots
High endemism (many species that are
found nowhere else) and in greatest
danger of extinction
Wilson 1993Biodiversity
c.10,000
species
(1/4 endemic)
how
many
remain?
Figure 15.2 (B) Maxent distribution of the potential niche of F. angustifolia under a glo
warming scenario of doubled CO2.
Extinctions caused by climate change
Magnitude
Organisms can evolve or migrate when faced with
climate change (or go extinct)
adaptive
macro-evolution
adaptive
Adaptive
micro-evolution
microevolution
extinction
Changes
changes in in
geographical
geographical
distribution
distribution
behavioural changes
abundance changes
Rate
Figure 16.1 Species’ responses to climate change. Species exhibit six general types
Evolutionary
response to
climate change
Plasticity to cope
with minor climatic
fluctuations
Research
Adaptation/
speciation
Source: T. Sparks
Oak (Q. robur) leaf
emergence in England
Extinction may result
if species cannot
adapt quickly enough
Fig. 1 Stages of bud development in Quercus
petraea. Stage 0, bud is quiescent and
protected by scales; Stage I, swelling bud;
Stage II, opening of the bud has occurred;
Stage III, leaves have grown; Stage IV, one
leaf at least is completely out of the bud;
Stage V, internodes have started growing.
carried out separately on each bulk of 10 (or 30) buds. Hence,
four different extractions were made for each stage. Finally,
725
with a crescent series of ethanol and embedded in Araldite
(Epoxy resin). Sections (1 µm thick) were stained with toluidine
Earlier leafing date in oak
since 1950.
SPECIES CAN MIGRATE & CHANGE DISTRIBUTION
However if habitat is fragmented then it is hard to move
(latitude or elevation)
Trends in Ecology and Evolution
1oin
C lowland
increase,
145kmregions
latitudinal
migration
oraltitude-for-latitude
167m elevation
ent migrations
and mountain
predicted
based on an
model of temperature similarity. A 1 8C
ure results in a range change of !167 m in altitude but !145 km in latitude (based on a temperature lapse rate of -6 8C km"1 altitude and
a in Refs [3,14]). Trees are not to scale.
Jump &
Penuelas 2009
Extinction (estimations are
imprecise)
Extinction
Raven (1988)
200 spp./year
Myers (1988)
7% lost in a decade
(Rainforests contain 50% of world’s spp.)
Millenium impact assessment 1sp./year
Estimates based on habitat destruction
and recorded extinctions
Millenium ecosystem assessment
•  Average extinctions in fossil record 0.003
species per year
•  100 birds plus mammals extinct 1900-2000
Equates to 1 species per year
Underestimation?
However,
12% of birds, 25% of mammals, and at least
32% of amphibians are threatened by
extinction
Islands
World Conservation Monitoring
Centre
596 extinct plant taxa many of
which are from oceanic islands
such as Hawaii or Mauritius
Plant species extinctions
Island
Documented spp. extinctions
Hawaii
108
St Helana
7
Bermuda
3
Rodrigues
8
Prance (1997)
IUCN –International union for
conservation of nature
Red data books –list threatened species e.g. Plants
Australia
1,016
China
350
Malaysia
522
Mexico
883
USA
2,262
Ireland
Wildlife Act 1976
Rare in Ireland or rare in a European context
Wildlife Act protects nearly all birds and 22 other
animal species
Flora protection order 1999
Lists 68 spp. Protected by legislation
Why conserve plants and
animals?
A- Moral duty
B- Ecosystem function
C- Socio-economic reasons
Recovery rate after major extinctions is slow
Recovery rates from the big 5
extinctions (geological time):
5-10 million years
Are we in the sixth
big extinction?
Humans depend on a relatively narrow
range of plants and animals for
survival
Food crops
Waxes
Building materials
Perfumes
Medicines
Dyes
Oils
Fibres
Fuel
Lubricants
Resins
Rubber & other latexes
How quantify value? Only 10% of plants and
animals have been evaluated for their value
4 of top 5 crops are
grasses
‘Grass’ for grazing would
top this list if included
∴Reliance on a narrow range of species
B- Genetic diversity within spp.
is also at risk
For crops we need the diversity to
•  Increase growth and yield
•  Increase disease resistance
•  Adapt crops to environmental conditions to extend
their range
•  Adapt crops to changing agricultural practices
•  Improve nutritional quality
(Need crop wild relatives and landraces)
Vavilov (1926) Russian
• Recognised importance of crop genetic
resources
•  Centres of diversity
•  Centres of origin
8 centres of diversity
Centres of cereal diversity
Wheat,
Barley,
Rye,
Rice
Oats
Maize
Saccharum
Sorghum,
Eragrostis
teff, African
rice
Einkorn
wheat
wheat genetic
resources
concentrated in the fertile
crescent –all have useful
genes for wheat breeding
Pasta wheat
Bread
wheat
Potato
Solanum tuberosum
Domesticated 8000 ybp
Peru and Bolivia (Lake
Titicaca)
Potato
Introduced Europe 16th century
Starch, protein, Fe, vitamins B & C
1840s –potato crop failure
Phytophthora infestans -fungal blight
Narrow genetic base of crop –all
plants originated from just two
introductions
Bacterial wilt – Pseudomonas
solanaceum
World potato collection screened and no
resistance found
Resistance eventually found in six primitive
cultivars
Maize
male
female
Teosinte (Zea mays ssp.
parviglumis)
Zea mays (maize)
Central
america
teosinte
Zea mays -maize
Corn blight
Helminthosporium
maydis
1970, USA caused major crop failure
Over-reliance on ‘Texas T. hybrid plants’
Hybrid maize
Cross two inbred lines - vigorous hybrid
(heterosis)
Problems
Narrow genetic base of hybrid crops
Resistance found in genetic resource collections and
bred into hybrids
New species of Zea
Z. diploperrenis
Discovered Mexico 1979
Used in breeding
Gene pool concept
(Harlan & de Wet, 1971)
Value of genetic resources depends on
the ease in which they can be utilized by
the breeder
GP1
Individuals of the same
biological species. Gene
transfer is easy
GP2
Gene transfer is possible
but difficult
GP3
Gene transfer is very
difficult or even
impossible by
conventional methods
Conclusions
•  Extinction removes species and variation within
species (valuable bioresources)
•  Centres of diversity and origin need conservation
•  Crops should not rely on a narrow genetic base
•  Gene pools require conservation
Next lecture
Conservation of genetic resources….
A - Species as genetic
resources/extinction risk
1.4 million spp. of organism have been
described (Wilson1993)
-Gross under-estimation
Science (2003) volume 300: a conservative 4
million
See Hodkinson TR & Parnell JAN (2007) Reconstructing the
tree of life, for further discussion of species numbers.
If a plant species
is named it must
have an
associated
herbarium
specimen
Animal
specimens must
go to natural
history museum
collections.
Species diversity
Estimated number of plant species (Prance 1997)
Described
Estimated
Algae
40,000
200-350,000
Lichens
13,500
20,000
Ferns & allies
12,000
12,500
Bryophytes
14,000
16,000
Gymnosperms 650
650
Angiosperms
300,000
250,000