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IMPACTS OF LOGGING ON GENETIC DIVERSITY OF TWO DIPTEROCARPS WITH CONTRASTING BREEDING SYSTEMS PowerPoint PPT Presentation


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Case study 2. IMPACTS OF LOGGING ON GENETIC DIVERSITY OF TWO DIPTEROCARPS WITH CONTRASTING BREEDING SYSTEMS. Introduction. Levels of genetic diversity can be quantified using various parameters: Allelic richness ( mean number of alleles per locus or effective number of alleles per locus)

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IMPACTS OF LOGGING ON GENETIC DIVERSITY OF TWO DIPTEROCARPS WITH CONTRASTING BREEDING SYSTEMS

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Impacts of logging on genetic diversity of two dipterocarps with contrasting breeding systems

Case study 2

IMPACTS OF LOGGING ON GENETIC DIVERSITY OF TWO DIPTEROCARPS WITH CONTRASTING BREEDING SYSTEMS


Impacts of logging on genetic diversity of two dipterocarps with contrasting breeding systems

Introduction

  • Levels of genetic diversity can be quantified using various parameters:

    • Allelic richness (mean number of alleles per locus or effective number of alleles per locus)

    • Gene diversity (heterozygosity)

    • Etc


Impacts of logging on genetic diversity of two dipterocarps with contrasting breeding systems

Therefore

Logging activities should maintain genetic diversity because it is required for a species for long-term evolutionary adaptation and short-term fitness

In theory

Reduced heterozygosity can result in decrease of population growth due to inbreeding depression (Charlesworth and Charlesworth, 1987).

Allelic richness could contribute to population growth through its effect on evolutionary potential, or the ability of a species to respond to changes in its selective environment (Koehn and Hilbish, 1987).


Impacts of logging on genetic diversity of two dipterocarps with contrasting breeding systems

Species selection

  • Two dipterocarp species with contrasting breeding systems

    • Shorea leprosula (predominantly outcrossed)

    • Shorea ovalis (apomictic; tetraploid)


Impacts of logging on genetic diversity of two dipterocarps with contrasting breeding systems

S. leprosula


Impacts of logging on genetic diversity of two dipterocarps with contrasting breeding systems

S. leprosula (domatia)


Impacts of logging on genetic diversity of two dipterocarps with contrasting breeding systems

S. leprosula (flowers)


Impacts of logging on genetic diversity of two dipterocarps with contrasting breeding systems

S. leprosula (seeds)


Impacts of logging on genetic diversity of two dipterocarps with contrasting breeding systems

S. ovalis (fruiting tree)


Impacts of logging on genetic diversity of two dipterocarps with contrasting breeding systems

S. ovalis (dry leaves)


Impacts of logging on genetic diversity of two dipterocarps with contrasting breeding systems

S. ovalis (stipule)


Impacts of logging on genetic diversity of two dipterocarps with contrasting breeding systems

S. ovalis (seeds)


Impacts of logging on genetic diversity of two dipterocarps with contrasting breeding systems

Gene flow

Demograhic structure

logged

Next mature crop

logged

In theory

Demographic structure (levels of genetic diversity at various developmental stages) and gene flow from adjacent populations can compensate the possible genetic erosion due to logging

Logging events involve extraction of mature trees

Next crop


Impacts of logging on genetic diversity of two dipterocarps with contrasting breeding systems

Pollen & seed

Seed only

Outcrossed species

Apomictic species

S. leprosula

S. ovalis

Seed dispersal is mainly by gravity – short distance


Impacts of logging on genetic diversity of two dipterocarps with contrasting breeding systems

Question

Does S. ovalis (apomictic) more susceptible to negative impacts of logging than S. leprosula (outcrossed)?

Therefore

Genetic erosion of S. ovalis (apomictic) after logging is unlikely to be compensated by gene flow from adjacent populations


Impacts of logging on genetic diversity of two dipterocarps with contrasting breeding systems

Study sites

NS = Natural site

LS = Logged-over site

Pasoh Forest Reserve

LS = Logged-over stand (logged in 1955)

Intensity of logging – 13.5% reduction of basal area (trees >10 cm dbh) with large-diameter trees showing the largest reduction

(Lee et al. 2002: Biological Conservation 104: 107-118)


Impacts of logging on genetic diversity of two dipterocarps with contrasting breeding systems

Sample collection


Impacts of logging on genetic diversity of two dipterocarps with contrasting breeding systems

SSRs analysis

(Shc01, Shc02, Shc03, Shc04, Shc07, Shc09 & Shc17; Ujino et al. 1998)

Data analysis

(Aa & He)

DNA extraction


Impacts of logging on genetic diversity of two dipterocarps with contrasting breeding systems

S. leprosula

Inverse J distribution

  • Natural – Large tree > pole-sized tree ≈ seedling

Predominantly outcrossing species

  • Logged - Reduction of genetic diversity at all the three stages

  • Elimination of alleles with low frequency (rare alleles)


Impacts of logging on genetic diversity of two dipterocarps with contrasting breeding systems

S. ovalis

Inverse J distribution

  • Natural – Large tree ≈ pole-sized tree ≈ seedling

Apomictic species

  • Genetic diversity maintained after logging

  • No obvious reduction of Aa at all the three stages


Impacts of logging on genetic diversity of two dipterocarps with contrasting breeding systems

For apomictic species (S. ovalis), maintaining of genetic diversity can be due to apomictic mechanisms and tetrasomic inheritance that maintained genetic diversity at pole-sized trees and seedlings

For predominantly outcrossed species (S. leprosula), loss of genetic diversity in logged-over stand still prevailed even after 50 years of regeneration. This might indicate that the population dynamic processes (i.e., gene flow) were unable to restore the loss of genetic diversity

Instead of relying on gene flow to restore the loss of genetic diversity, logging activities on S. leprosula

should designed in a way that the current levels of genetic diversity can be maintained even after logging


Impacts of logging on genetic diversity of two dipterocarps with contrasting breeding systems

Simulated-removal of individual based on cutting limit (dbh) to maintain maximum levels of genetic diversity

  • Using the 154 large S. leprosula from Natural Site

  • Simulated-removal of individuals based on dbh (cm): >100, >95, >90, >85, >80, >75,…..>35

  • Also tested for the prescriptions of:

  • Malayan Uniform System (MUS) - removing of trees >45 cm dbh

  • Selective Management System (SMS) - removing of trees >50 cm dbh


Impacts of logging on genetic diversity of two dipterocarps with contrasting breeding systems

100%

95%

SMS

MUS


Impacts of logging on genetic diversity of two dipterocarps with contrasting breeding systems

S. leprosula (large trees)

35 m

BIG

0.15

0.1

0.05

I

0

Moran's

-0.05

-0.1

Ng et al. 2004: Molecular Ecology 13: 657-669

-0.15

1

2

3

4

5

6

7

8

9

Distance class

Simulated-removal of individual at random versus in clump

It is postulated that loss of genetic diversity will be more rigorous if logging activities are anticipated to extracts trees in clump rather than random


Impacts of logging on genetic diversity of two dipterocarps with contrasting breeding systems

  • Simulated-removal of individual at random

    • Using random number generator

    • Individuals were identified and removed randomly


Impacts of logging on genetic diversity of two dipterocarps with contrasting breeding systems

Resampling 3

Resampling 2

Resampling 1

  • Simulated-removal of individual in clump

    • Using random number generator

    • A focal individual was selected

    • Based on XY coordinates, other nearest individuals were selected and removed in clump


Impacts of logging on genetic diversity of two dipterocarps with contrasting breeding systems

Random

Clump

Removal of <12% individuals at random will be able to maintain ≈100% alleles

14.6%


Impacts of logging on genetic diversity of two dipterocarps with contrasting breeding systems

Conclusion:

Does S. ovalis (apomictic) more susceptible to negative impacts of logging than S. leprosula (outcrossed)?

No, apomictic mechanisms and tetrasomic inheritance of S. ovalis maintain genetic diversity at pole-sized tree and seedling

Simulated-removal of individual based on cutting limit

To conserve 100% of alleles, the tolerable cutting limits > 85 cm dbh

(It is important, however, to keep in mind that this estimate might be species and even population specific)

Simulated-removal of individual at random versus in clump

Support the postulation that loss of genetic diversity will be more rigorous if logging activities are anticipated to extracts trees in clump rather than random


Impacts of logging on genetic diversity of two dipterocarps with contrasting breeding systems

Thank You


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