CONSERVATION GENETICS

1. CONSERVATION GENETICS READINGS:FREEMAN, 2005 Chapter 52 1206-1210 Chapter 54Pages 1272-1277

2. GENETIC DIVERSITY The diversity of life is fundamentally genetic. A variety of genetic methods have been used to investigate diversity both within and between species. Here are a few: • Morphological variation -- a good clue, but does not correlate perfectly with genetics; • Chromosomal variation -- inversions, translocations and polyploidy; • Soluble proteins -- blood groups, soluble enzyme polymorphism’s; • DNA markers -- microsatellites, “fingerprint” loci.

3. CONSERVATION OF GENETIC VARIATION • The foundation of diversity is the process of natural selection shaping genetic variation. • When genetic variation is absent (zero heterozygosity), the population (or species) has limited evolutionary potential and the risk of extinction is high. • The conservation of genetic variation provides a hedge against extinction.

4. An Endangered Species: Red Wolf • This canine family member was once found in the southeast. It disappeared in the wild by the late 1970s. • Reintroduced into Great Smoky Mountains National Park in 1990’s.

5. An Endangered Species: Red Wolf • Examination of DNA demonstrated that the red wolf is a hybrid between gray wolf and coyote. • Expansion of coyote range and shrinking of gray wolf range resulted in gene swamping of red wolf genes by coyote genes.

6. An Endangered Species: Cheetah • A species that shows a very low level of genetic variation. • May have experienced a genetic bottleneck near the end of the last ice age (10,000 - 12,000 years ago) when many other mammal species became extinct. • Low genetic variation in “fingerprint” loci compared to other cat species.

7. Population Size and Extinction Risk • Populations are subject to chance or sampling error in getting alleles from one generation to the next (genetic drift, genetic bottlenecks, founder effects). • Populations are subject reduction in gene flow and gene swamping. • Small populations are particularly vulnerable to extinction due to reduction in genetic variation (heterozygosity).

8. CONSERVATION GENETICS (I) • Conservation genetics is an area of study that determines genetic variation and the processes that diminish it. • Heterozygosity is a measure of genetic variation. • Processes that diminish heterozygosity, especially in small populations, are: 1) genetic drift; 2) genetic bottlenecks; 3) inbreeding.

9. CONSERVATION GENETICS (II) • The movement of alleles from one population to another is called gene flow. • Gene flow promotes heterozygosity by increasing the chances of outbreeding. • Fragmentation often results in a reduction of gene flow into isolated populations. • Gene swamping occurs when small populations are genetically assimilated by much larger populations.

10. Effective Population Size (Ne) • Effective population size gives a crude estimate of the average number of contributors to the next generation (Ne). • Always a fraction of the total population. • Some individuals will not produce offspring due to age, sterility, etc. • Of those that do, the number of progeny many vary.

11. Effective Population Size (Ne) • A variety of ways of estimating (Ne) have been formulated. • One that accounts for unequal sex ratios among breeding adults is: Ne = 4(NM * NF) NM + NF where NM = number of males NF = number of females

12. Effective Population Size (Ne) • What is the effective population size (Ne) of one with 100 females and 10 males? • Remember: Ne = 4(NM * NF) NM + NF where NM = number of males NF = number of females

13. Effective Population Size (Ne) • What is the effective population size (Ne) of one with 100 females and 10 males? Ne = 4(100 * 10) = 4000 = 36 100 + 10 110 • Remember: Ne = 4(NM * NF) NM + NF where NM = number of males NF = number of females

14. Genetic Drift • Random change in allele frequency due to sampling only a small portion of gametes from the previous generation. • Most likely in small populations (<100 individuals). • Least likely in large populations (< 1,000 individuals.

15. Genetic Drift

16. Genetic Drift The proportion of genetic variation retained in a population of constant size after t generations is approximately: Proportion = (1 -1/(2N))t where N = number of individuals t = number of generations

17. Genetic Drift What proportion of genetic variation is retained in a population of 10 individuals after 10 generations? Proportion = (1 - 1/20)10 = 0.9510 = .19 or 19% Proportion = (1 -1/(2N))t where N = number of individuals t = number of generations

18. Genetic Bottleneck • The loss of genetic variation when a population drops in size. • Effective population size (Ne) after a fluctuation in population size is estimated by: Ne = t/ sum of (1/Ni) where Ni = size of population in generation i t = number of generations

19. Genetic Bottleneck

20. Genetic Bottleneck What is the effective population size (Ne) of one that goes from 1,000 (t1) to 10 (t2) and recovers to 2,000 (t3)? Ne = t/ sum of (1/Ni) where Ni = size of population in generation i t = number of generations

21. Genetic Bottleneck What is the effective population size (Ne) of one that goes from 1,000 (t1) to 10 (t2) and recovers to 2,000 (t3)? Ne = _________ 3 ________ = 3/0.1015 1/1000 + 1/10 + 1/2000 = 29 individuals Ne = t/ sum of (1/Ni) where Ni = size of population in generation i t = number of generations

22. Inbreeding • Inbreeding occurs more frequently in isolated and small populations. • It acts to reduce Ne. It is estimated bY; Ne. = ____N_____ 1 + F where F is the inbreeding coefficient or probability of inheriting 2 alleles from the same ancestor.

23. Inbreeding vs Outbreeding

24. Inbreeding Depression • Prairie chickens in Illinois declined due to decreased hatching success. • Individuals from Iowa were introduced to the breeding population and hatching success improved.

25. Metapopulations Reduce Extinction Risk (I) • Studies of the Granville fritillary show how subpopulations stabilize overall population size. • In addition, provide opportunity for gene flow.

26. Metapopulations Reduce Extinction Risk (I) • Oerall population size remains relatively stable even when local populations go extinct. • The metapopulation provided for increased opportunity for gene flow between local populations.

27. Population Viability Analysis (I) • PVA provides a means for estimating the likelihood that a population will avoid extinction for a given period of time. • Freeman (2005) describes a study of how migration rates are likely to influence population viability of an endangered marsupial.

28. Population Viability Analysis (II) • This endangered marsupial lives in an old-growth forest in southeastern Australia and relies on dead trees for nest sites. • PVA was used to predict the consequences of habitat loss and forest fragmentation on this endangered species.

29. Population Viability Analysis (III)

30. Population Viability Analysis • Freeman describes demographic studies of a European lizard species that is declining in some areas. • He explains how migration maintains some local populations in spite of local extinction. • He presents a model of how migration rates are likely to influence population viability of an endangered marsupial.

31. Life History Characteristics, Population Size and Extinction Risk • Extinction risk is related to the life history characteristics of the species in question. • Small populations with “long-lived” life history characteristics are particularly vulnerable to extinction .

32. LIFE HISTORY CHARACTERISTICS • Population attributes such as lifespan, mortality and natality patterns, biotic potentials, and patterns of population dynamics are called life history characteristics. • Life history characteristics have important consequences for wildlife management and extinction risk.

33. FOUR IMPORTANT ASPECTS OF LIFE HISTORIES • 1. Lifespan --- the upper age limit for the species. • 2. Mortality --- the pattern of survivorship (I, II, or III). • 3. Natality --- the age to reproductive maturity and number of offspring produced. • 4. Biotic potential --- maximum rate of natural increase (rmax = births - deaths).

34. Short-lived. Type III survivorship high juvenile mortality; relatively secure old age. Many offspring from young adults. High maximum rate of population growth. Long-lived. Type I survivorship: low juvenile mortality; high mortality at old age. Few offspring from older adults. Low maximum rate of population growth. LIFE HISTORY EXTREMES

35. LIFE HISTORY TRAITS FORM A CONTINUUM (I) • Every species can be placed somewhere on a continuum with respect to the life history extremes. • Comparisons of life histories are best done between species that show similar evolutionary histories.

36. LIFE HISTORY TRAITS FORM A CONTINUUM (II) • Field mice and muskrats are rodents in closely related taxonomic families. • Field mice (short-lived) show a Type III survivorship and produce many offspring. • Muskrats (long-lived) have a Type I survivorship and produce few young.

37. LIFE HISTORY TRAITS FORM A CONTINUUM (III) • See Freeman (2005) page 1195 for full discussion.

38. Some Long Lived Species Whooping Crane Spotted Owl • These have moderate juvenile mortality, low adult mortality, and low fecundity. • They are endangered.

39. Some Short Lived Species Starling House Finch • These have high juvenile mortality, moderate adult mortality, and high fecundity. • They are thriving.

40. CONSERVATION GENETICS READINGS:FREEMAN, 2005 Chapter 52 1206-1210 Chapter 54Pages 1272-1277