tree seed supply chains

Forest Genetic Resources Training Guide

Tree seed supply chains

Genetic bottlenecks in the restoration of Araucaria nemorosa

David Boshier &Chris Kettle


Location of New Caledonia


What are the impacts of human interventions on trees?

13 of the 19 species of Araucaria


What are the impacts of human interventions on trees?


A. ruleiendangered

A. muellerilower risk – conservation dependent


Araucaria nemorosa – critically endangered (IUCN)

monoecious flowers, self-compatible, wind pollinated, wind dispersed


A. nemorosa


StudyCompared genetic diversity in plants from

i.cones collected from trees

vs

ii.seed from forest floor


Where & how should we conserve?


Production of ripe cones in six natural populations

Population

Code Area (ha)

N Sample size

# of trees >15cm dbh

# of trees with cones

# cones/ trees with cones

Mean dbh (cm)

Minimum dbh of trees with cones (cm)

Kaanua N1 22.68

>1000

25 13 1 2 14.9 16

Vane N2 15.72

>1000

15 8 1 7 25.6 48

New Forest

N3 15.2 >1000

63 45 4 1,2,3,3 18.2 18.5

Mini Nuri N5 1.28 <500 36 22 4 2,2,7,5 18.4 22.5Foret Nord

N6 0.44 93 28 11 5 1,1,1,3,9

17.1 32.7

Natasha’s N7 1.48 <100 62 23 2 2,8 12.9 23.5


How big is “big enough”?

• 50/500 rule (Franklin 1980)

• 50 - inbreeding depression to acceptable level

• 500 - sufficient for new variation from mutation to replace that lost by genetic drift

• refers to effective population size (Ne) rather than survey numbers (N) – so may need many more!

• in trees Ne smaller than N due to: overlapping generations, dioecy, asynchronous flowering, fecundity differences between individuals


Genetic diversity, % rare alleles (<0.1), inbreeding coefficients in: adults (A), wild seedlings (W), nursery seedlings (N)

Population

Code Sample type

AE (S.E.) He (S.E.) % rare alleles

FIS Ne

Kaanua N1 A 9.53 (2.46)

0.72 (0.09)

84 0.135*

Kaanua N1 W 8.83 (1.90)

0.71 (0.09)

74 0.194* 30

Kaanua N1 N 2.81 (0.46)

0.46 (0.09)

38 -0.024n.s.

1

Foret Nord

N6 A 6.12 (1.11)

0.65 (0.07)

68 0.009n.s.

Foret Nord

N6 W 5.59 (0.90)

0.62 (0.07)

65 0.168* 11

Foret Nord

N6 N 6.40 (0.87)

0.69 (0.05)

65 0.282* N/C


Theory

• direct impacts

• decrease pop. size

• increase spatial isolation

• decrease densities

• change local environment

genetic processes

genetic drift

gene flow

mating - inbreeding

selection


Bottleneck genetic drift


Your mission

• draw out the seed supply chain

• design a strategy for the collection and use of germplasm

Objective – ensure the maintenance of genetic diversity in the on-going restoration efforts for this threatened species


How?

• Step 1 - map out the seed/germplasm supply chain for A. nemorosa

• Draw a flow diagram of the chain, from the source to the final user, within the field of restoration (from seed tree to a new plant in its final use).

• The map should identify• players (individuals, institutions) and processes in the chain

(what the players do)• influences of the chain on genetic variation (bottlenecks,

selection, genetic drift)• limiting social factors in the chain (e.g. policies/laws, business,

institutions or resources)


How?

• Step 2 – analysis

• What are the genetic risks associated with the actual system of seeds?

• Specific recommendations to improve the situation, dealing with the diversity within the seed system (e.g. practical methods of collecting germplasm that ensure genetic diversity in restoration efforts)

tree seed supply chains

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