Trees outside of forests Devising options for conservation of two tree species outside of forests...
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Transcript of Trees outside of forests Devising options for conservation of two tree species outside of forests...
Trees outside of forests
Devising options for conservation of two tree species outside of forestsDavid Boshier
What are the impacts of human interventions on trees?
What are the genetic impacts of human interventions on trees?
impacts of human interventions on trees? fragmentation, afforestation, silviculture, deforestation, agriculture, shifting cultivation, premature death, clear fell
genetic impacts of human interventions on trees?
hybridisation, inbreeding depression, dysgenic selection, loss of genetic diversity, species loss, increase variance between populations, genetic loss/erosion
Examples from other classes
Genetic impacts of human interventions on trees
Humans impact forests in a variety of ways, eg
• conversion of forest to agriculture & other uses
• forest fragmentation
• logging, harvesting of different types
• domestication/breeding
Need to consider influence of interventions on functionality of tree populations & relevance to conservation
Genetic impacts of human interventions on trees
All interventions influence genetic diversity of trees to greater or lesser extent
In many circumstances impacts on genetic diversity may not be a priority
Foresters/conservation managers need to be able to identify -
– how patterns of genetic variation are altered
– under what sort of circumstances genetic diversity and its loss may become limiting
Where & how should we conserve?
In situ - reserve system of undisturbed, protected areas within natural distribution (ecosystem based)
Ex situ - artificial maintenance of populations outside natural distribution (species based)
In situ - Ex situ
6
Impacts of human disturbance
• often superimposed on habitat heterogeneity
• may lose species and populations adapted to lowlands/good soils
not random
Conservation of biodiversity in situ: trees as a paradigm
ideal reserve model
emphasis: large, continuous, protected areas
limitations: location, size, security, biology:– movement of animals– extensive distribution of many species– gene flow between populations– upland, non agricultural areas
essential but not sufficient
Where should we conserve?
In situ - reserve system of undisturbed, protected areas within natural distribution (ecosystem based)
Ex situ - artificial maintenance of populations outside natural distribution (species based)
In situ - Ex situ
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Conservation of biodiversity ex situ: methods and limitations
seed banks - problems of regeneration
plantations - changes in gene frequencies, few populations
botanical gardens - deficiencies for gene pool conservation
11© RBG Kew © RBG Kew
a large number of individuals of many species have long ago ceased being ecologically (and evolutionarily) reproductive; they flower but set no seed, or if they set seed, the seedlings never lead to recruitment of adults. 12
© DH Boshier
© DH Boshier
These are the living deadJanzen 1986
• Conservation of species and genotypes• Conservation paradigms – in situ, ex situ,
through use on farms – circa situm• Fragmentation – gene flow patterns and
maintenance of viable populations• Reproductive materials: source and collection
Issues of concern – conservation of tree genetic resource outside of forests
Theory
direct impacts
decrease pop. size
increase spatial isolation
decrease densities
change local environment
genetic processes
genetic drift
gene flow
mating - inbreeding
selection
Fragmentation
x yz
x yz
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Fragmentation
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A: Low genetic structure
B: High genetic structure
Low genetic differentiation (Gst)
High genetic differentiation (Gst)
Extinction
x yz
x yz
x yz
x yz
Extinction
x xx
y yy
B: Gene flow reduces loss of genetic diversity
Reduced genetic differentiation (Gst)
Increased genetic differentiation (Gst)
A: Drift and extinction: loss of genetic diversity
x xy
x yz
x xx
z zz
x xx
y yy
Drift – no gene flow
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Drift
gene flow
B: fragmentation
Low genetic differentiation (Gst)
High genetic differentiation (Gst)A: fragmentation
x xx
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y yy
x xy
x zz
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y z x y
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with drift among isolates
with gene flow via ‘isolated’ trees
Range of land-use systems may be important for long term genetic viability of some tree species
through– conservation of particular genotypes not found in
reserves – facilitation of gene flow between existing reserves– maintenance of MVPs (Minimum Viable Populations) – intermediaries & alternate hosts for pollinators & seed
dispersers
Broad vision of corridors - mosaic of land-uses that promote connectivity & conservation of biodiversity more generally
Isolated trees– can we collect seed?
Altered mating patterns in fragments
Predictions: increased inbreeding
greater pollen dispersal
fewer sires
Isolated tree Continuous forest
inbreedingdispersal
sires
Can valuable tree genetic resources persist outside of forests and if so what measures need to be taken to ensure they persist?
Swietenia humilis – IUCN listed as vulnerable, also on CITES appendix II monoecious flowers, self-incompatible, bee pollinated, wind dispersed
trees sampled at Punta Ratón, Honduras
Swietenia humilis
White, Boshier & Powell, 2002
Pollen flow into fragmentsSwietenia humilis
Fragment Fragment % pollen from
“size” outside
Las Tablas* 97 36.0
El Jicaríto 44 47.0
Cerro El Jiote 22 38.3
Tablas Plains 8 68.4
Tree 501** 1 100.0
* part of continuous forest, surrounded by unsampled trees** an “isolated” tree
White, Boshier & Powell, 2002
Frequency of pollen flow to S. humilis trees in Cerro Jiote fragment and to an “isolated” tree, Honduras
0
0.4
0.8
>1.50.9-1.20.3-0.6Distance, km
Pollen donors
White, Boshier & Powell, 20020
0.4
0.8
4.53.3-3.60.9-1.2 2.1-2.4
Distance, km
Pollen donors ‘Isolated’ tree
C. Jiote
>20 trees selfed - no seed
Pachira quinata
Central + South America
Deciduous tree
Hermaphrodite flowers
Self-incompatible
Bat (& moth) pollinated
Seed + ‘kapok’
wind dispersed
Costa Rica: Forest vs Pasture
Stewart PropertyLomas Barbudal Reserve
Pasture
Stewart Property
SP01
SP02
SP03
SP04
SP05
SP06
SP07SP08
SP09
SP10
SP11
SP12
SP13
SP14
SP15SP16
SP17
SP18
SP19
SP20
0
200
400
600
800
1000
0 200 400 600 800 1000 1200 1400 1600 1800
West (m)
No
rth
(m
)
Forest
Results: Forest vs Pasture
SiteOutcrossing
rate (SE)Correlationof tm (SE)
Numberof sires
Dispersaldistance
Forest0.926 (0.021)
0.117 (0.045) 3.3 - 4.1 48 metres
SiteOutcrossing
rate (SE)Correlationof tm (SE)
Numberof sires
Dispersaldistance
Forest0.926 (0.021)
0.117 (0.045) 3.3 - 4.1 48 metres
Pasture0.828 (0.085)
0.636 (0.148) 2.9 - 4.4 158 metres
Lower outcrossing & greater dispersal but not fewer sires in the pasture
Results: Forest vs Pasture
SiteOutcrossing
rate (SE)Correlationof tm (SE)
Numberof sires
Dispersaldistance
Forest0.926 (0.021)
0.117 (0.045) 3.3 - 4.1 48 metres
Fuchs
Forest0.915
(0.043) 1.8 - 2.6
Pasture0.828 (0.085)
0.636 (0.148) 2.9 - 4.4 158 metres
Fuchs Pasture
0.777 (0.114) 1.2 - 1.6
Fuchs et al 2003 suggest isolated (>500m)pasture trees receive less outcrossed pollen
Results: Forest vs Pasture
Costa Rica: Pasture
Predict that selfing will increase with isolation
But it doesn’t!
Stewart Property
SP01
SP02
SP03
SP04
SP05
SP06
SP07SP08
SP09
SP10
SP11
SP12
SP13
SP14
SP15SP16
SP17
SP18
SP19
SP20
0
200
400
600
800
1000
0 200 400 600 800 1000 1200 1400 1600 1800
West (m)
No
rth
(m
)
82%71%
51%29%
29%20%
Isolated by 350m
Self-incompatibility system
Reduced germination of self pollen–Slower growth rate of self pollen
Ability to self varies among trees– 50% non-selfers– 12.5% selfers
Pollen reaching ovary Self Cross
48 hours 15% 56%
72 hours 64% 90%
120 hours 89% 90%
WCMC World List of Threatened Trees (IUCN Red List categories of threat)
http://www.wcmc.org.uk/trees/Background/intro.htm
9% of world's tree flora globally threatened with extinction
accuracy of assessment?
IUCN this studyS. humilis - vulnerable ?P. quinata - not listed ?
Your task
Derive an action plan to ensure effective conservation and use of both species outside of forests