1. Inbreeding

2. A1A1
A1A2
A2A2
A1A1
A1A2
A2A2
A1A1
A2A2
A1A2
A1A1
A1A2
A2A2

4. Calculating inbreeding coefficients from pedigrees
half-sib mating
F = probability of [(a) or (b)] = 1/16 + 1/16 = 1/8

5. X X * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
Outbred population * * * X * * * * * * * * * * * * * * * * * * * * * * * *
Inbred population * * * X * * * * * * * * * * * * * * * * * * * * * * *

6. Consequences of inbreeding
inbreeding “exposes” deleterious recessive genes by making them homozygous
it causes a drop in fitness known as inbreeding depression
inbreeding depression = decline in fitness (survivorship, reproductive success) due to mating with relatives

7. Inbreeding depression in captive mammal populations

8. Inbreeding depression in humans

9. Inbreeding depression in plants is common
from Futuyma (1998), p. 313

10. In experimental studies of plants, inbreeding depression is widespread
In experimental studies of plants, inbreeding depression is widespread. It is also the likely cause of lower fitness in small and endangered plant populations.

11. Classic studies of inbreeding in natural populations
van Noordwijk and Scharloo (1981) studied inbreeding in an island population of great tits (Parus major) in Holland
a small isolated population:
pedigree for entire population
was determined by banding birds
inbreeding was common

12. from Futuyma (1998), p. 312

13. Inbreeding depression in Parus major
van Noordwijk and Scharloo (1981)
Failure of egg hatching increased with the inbreeding coefficient of parents

14. However...
while hatching failure increased with inbreeding, hatchlings that did survive showed even higher success when they bred
over several generations, a similar effect may “purge” the genome of deleterious genes

15. Implications for conservation
inbreeding depression can be severe and its onset can be rapid
endangered populations with a “history” of inbreeding may actually show fewer effects
but, the immediate effects to an historically outbred population could drive it to extinction

16. Genetic restoration of greater prairie chickens
males display on communal breeding sites known as leks
the species depends on intact grassland habitat for survival

18. Number of males displaying on leks
Prairie chickens in Illinois were nearly extinct by Birds were introduced from Nebraska, Kansas, and Minnesota.

19. Prior to introduction, there was a continuous decline in hatching success. Immediately after the introduction, hatching success improved.

20. Genetic restoration probably lowered inbreeding depression
assays of highly polymorphic microsatellite DNAs showed Illinois populations to be inbred prior to the introduction
this supports the inbreeding depression hypothesis for decline and recovery