Case study 2
This presentation is the property of its rightful owner.
Sponsored Links
1 / 29

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


  • 96 Views
  • Uploaded on
  • Presentation posted in: General

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)

Download Presentation

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

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


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)

    • Gene diversity (heterozygosity)

    • Etc


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).


Species selection

  • Two dipterocarp species with contrasting breeding systems

    • Shorea leprosula (predominantly outcrossed)

    • Shorea ovalis (apomictic; tetraploid)


S. leprosula


S. leprosula (domatia)


S. leprosula (flowers)


S. leprosula (seeds)


S. ovalis (fruiting tree)


S. ovalis (dry leaves)


S. ovalis (stipule)


S. ovalis (seeds)


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


Pollen & seed

Seed only

Outcrossed species

Apomictic species

S. leprosula

S. ovalis

Seed dispersal is mainly by gravity – short distance


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


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)


Sample collection


SSRs analysis

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

Data analysis

(Aa & He)

DNA extraction


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)


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


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


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


100%

95%

SMS

MUS


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


  • Simulated-removal of individual at random

    • Using random number generator

    • Individuals were identified and removed randomly


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


Random

Clump

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

14.6%


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


Thank You


  • Login