1. 1 How small can a population get before inbreeding becomes intolerable? If F = 1 and N e = 4 M F 2N e M + F Then F = 1 and F = 1 + 1 2 4 M F 8F 8M M + F 60a Important! Formulas first:

2. 2 How small can a population get before inbreeding becomes intolerable? F = 1 + 1 8F 8M Research on domestic farm animals: natural selection for performance can balance inbreeding depression if the ΔF is no more than 1% per generation. So, F = 0.01 is a tolerable level of inbreeding 60a

3. 3 How small can a population get before inbreeding becomes intolerable? F = 1 + 1 8F 8M If F = 0.01 is a tolerable level of inbreeding, then.01 = 1 + 1 so F = 25 and M = 25 8F 8M or, N e = 50 60a Magic number!

4. 4 Number of females Number of males 15.01 tolerance.005 tolerance What happens to the ‘magic number’ when sex ratios are unequal? 25 1 8N m 8N f + F = Conclusion: 15 = smallest number of effective individuals of one sex 60 25

5. 5 Population bottlenecks Population size Time bottleneck H = 1 - 1 = expected proportion of H o retained after a 2N e 1-generation bottleneck H t = H o 1 - 1 t = proportion of H o retained t generations after 2N e a bottleneck if N e = 4 at t=0, then H t=1 = 1 - 1 = 7 i.e. 1/8 of original H 2 x 4 8 was lost in 1 generation 61A

6. 6 The effect of bottlenecks on H Proportion of original heterozygosity remaining in small populations 61-1

7. 7 Probability of retaining a rare allele after a bottleneck of size N for a single generation Population size (N e ) 25 0 q =.05 q =.01 q =.10 Probability of retention 1.0 0 61-2

8. 8 Conclusions: Effects of Inbreeding and Bottlenecks  H  P ---------------------------------------- Bottleneck:decreases by 1/2NeLARGE decrease with reproductionespecially of rare alleles Inbreeding: LARGE decreaseno change 65

9. 9 Effects of a genetic bottleneck in a plant: Lakeside daisy (Hymenoxys acaulis) - only one population survived agricultural development - self-incompatibility - requires mates of a different mating type -but alleles for only one mating type survived the bottleneck…..

10. 10 Founder Effect Wild population zoo Speke’s gazelle Founders to zoo in 1970s: 1 male, 3 females N = 4, but N e = 2 Initial severe inbreeding In 1982, N = 29 Inbreeding depression eliminated. Escaped F - vortex? 65A (Founders)

11. 11 Contribution of 16 founders to the captive Guam Rail population Founders % Founder contribution 0 20 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 31 32 33 36 98 10 5 15 65e Expected 1/16 =.0625

12. 12 http://www.ultimateungulate.com/gazellespeke.html Speke’s gazelle

13. 13 http://www.ultimateungulate.com/okapi.html Okapi

14. 14 Goeldi's monkey and Okapi 40% loss of genetic diversity in captive populations due to unequal founder contribution Drosophila on Hawaiian Islands 95 of 100 species are endemic to only one island or volcano (results of migration of single, fertilized “eves”)

15. 15 Population Management: Founder Effect Wild population founders 65A Problem: Founding event--> forced inbreeding --> inbreeding depression Best Solution: MAXIMIZE GROWTH OF THE POPULATION A.S.A.P.!!

16. 16 What is the minimum Ne necessary to maintain evolutionary potential??? 500 The other magic number Selection balances Drift…..Maybe!!!!

17. 17 III.The Biology of Small Populations 1.Population Dynamics of Small Populations 2.Genetics 3.Population Viability Assessment IV. The Ecology of Conservation and Extinction

18. 18 Minimum Viable Population First stab: 50 / 500 rule. John James Audubon – the first PVA

19. 19 Mauritian Kestrel 1970’s: Rarest bird in the world!

20. 20 Triage Triage: Sorting the casualties of war into those too badly wounded to recover, those who can survive without help, and focusing on the remainder.

21. 21 Triage Conservation Biology “We might abandon the Mauritius kestrel to its all-but-inevitable fate, and utilize the funds to proffer stronger support for any of the hundreds of threatened bird species that are more likely to survive” - Norman Myers, The Sinking Ark

22. 22 Hopeless Cases? There are no hopeless cases, only people without hope and expensive ones – Michael Soulé

23. 23 But... The Mauritius kestrel was never exceptionally common The fact still remains that we have limited resources to allocate to many species –10 million $ to rent a Panda