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

x yz

x yz

zzz

yy z zy

yy z z zz

zzz xx yyy

x xxy y

y

y yy

x xx

Fragmentation

y z x y

x y z

y x z

z x y x

x yz

x yz

x yz

x yz

x xxy y

y

y yy

x xx

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

x yz

x yz

x yz

x yz

x xy

x zz

x yy

x yz

Drift

gene flow

B: fragmentation

Low genetic differentiation (Gst)

High genetic differentiation (Gst)A: fragmentation

x xx

z zz

x xx

y yy

x xy

x zz

x xz

y yx

y z x y

x y z

y x z

z x y x

x yz

x yz

x yz

x yz

y z x y

x y z

y x z

z x y x

x yz

x yz

x yz

x yz

x yz

x

x yz

x yz x y

z

z

y

x

x yz

x

x yz

x yz

x yz

z

y

x

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