L34 Conservation Genetics

Question 1

Causes of extinction

Answer 1

• predators
• habitat loss of fragmentation
• climate change

Question 2

Extinction vortex

Answer 2

see onenote

Small populations prone to:

• random genetic drift/allele frequency
• inbreeding => homozygosity
• maladaptation to local environment

Question 3

The mountain pygmy possum

Answer 3

see onenote

• hibernates under a cover of snow
• found in 3 isolated geographic regions
• prime habitat occurs in ski resort areas
• numbers less than 200 - endangered

Question 4

The mountain pygmy possum - habitat

Answer 4

restricted to alpine and boulderfields

cold wet climate

mountain plum-pine

Question 5

Past distribution

Answer 5

see onenote
Mt Kosciuzko
Bogong High Plains
Mt Buller

Widely distributed in the past and population sizes were large

Question 6

Current distribution

Answer 6

• 3 isolated regional populations
• <10km squared habitat
• Population in Mt Buller the most badly threatened

Question 7

High levels of variation despite genetic fragmentation in populations of pygmy possum

Answer 7

see onenote

Indication of distinct population

Overall snapshot of allelic variation that exists at microsatellite loci in this species

These three population are quite distinct in their genetic variation

1 species, 3 distinct gene pools

Fewer heterozygotes and more homozygotes than expected, significant Hw P-value, indicates inbreeding

Question 8

Pygmy possum - biology

Answer 8

• seasonally hibernating
• polygynous mating system = one male, multiple females, 1 male : 5 females
• 20-50% diet bogong moths

Question 9

Mt Buller population

Answer 9

<1km squared habitat

Question 10

Mt Buller 1996

Answer 10

see onenote

Highly significant values between expected and observed heterozygotes

There is not only high inbreeding and low heterozygosity but also distortion of male : female ratio, reduce probability of all these females reproducing

sex ratio 1m : 10f

Question 11

Habitat modification at Mt Buller

Answer 11

see onenote

6 points

Question 12

Mt Buller 2004

Answer 12

see onenote

Expected level of heterozygosity has dropped, inbreeding coefficient is high

Population size has reduced

Sex ratio is now 1 male : 22 female

Half genetic diversity now compared to what it was

Question 13

Mt Buller 2005

Answer 13

see onenote

• further decline

Forced into lower elevations, aren’t doing so well, less moths that they feed on , less snow

Habitat is fragmented, animals isolated from each other, there is not equal chance of reproduction amongst individuals

Question 14

Consequences

Answer 14

• loss of genetic diversity
• highly inbred
• reduction in fitness
• functionally extinct?

HOWEVER
The species does exist in the central and northern region, provides a solution

Question 15

Habitat improvement

Answer 15

see onenote

Ski resort developments designed to protect possum

Population still in decline
- There was only 30 animals and only one of them was a male, the population will not restore itself despite all the changes made

Question 16

Genetic rescue

Answer 16

Enlarge gene pool
Resolved sex ratio problem

Shown using genetic markers, the animals were genotyped, possible to show that they were reproducing with the females present at mount Buller = hybrids. Size of gene pool has increased.

Central genes = genes from the central gene pool

Ne = 4(number of females x number of males) / (number of females + number of males)

Gradually increase size of gene pool by bringing in more individuals from another population

If the species has gone down this extinction path, genetic rescue only works if there is a closely related species that could allow it to produce offsprings