Genetics 101: Genetic differentiation in the age of ecological restoration

1. Genetics 101: Genetic differentiation in the age of ecological restoration Susan J. Mazer Department of Ecology, Evolution & Marine Biology University of California, Santa Barbara Mazer@lifesci.ucsb.edu

2. Genetics 101: Genetic differentiation in the age of ecological restoration Susan J. Mazer Department of Ecology, Evolution & Marine Biology University of California, Santa Barbara Mazer@lifesci.ucsb.edu

3. Genetic concepts to be considered • Rules of inheritance • Genetic processes • Consequences of mismatches between sources of material for restoration and • (a) the environment of the restoration site or • (b) the genotypes resident at the restoration site

4. Up and running: common vocabulary Population genetic processes Ecological considerations Genetic phenomena

5. Up and running: common vocabulary Population genetic processes Ecological considerations Genetic phenomena Inheritance in a nutshell Local adaptation Genetic differentiation Genetic drift Founder effect Genetic swamping

6. Up and running: common vocabulary Population genetic processes Ecological considerations Genetic phenomena Inheritance in a nutshell Local adaptation Genetic differentiation Genetic drift Founder effect Genetic swamping Ecotype Heterosis & “hybrid vigor” Inbreeding depression Outbreeding depression Hybrid breakdown

7. Up and running: common vocabulary Population genetic processes Ecological considerations Genetic phenomena Inheritance in a nutshell Local adaptation Genetic differentiation Genetic drift Founder effect Genetic swamping Ecotype Heterosis & “hybrid vigor” Inbreeding depression Outbreeding depression Hybrid breakdown Phenology Pollen limitation Climate change

8. Inheritance in a tiny nutshell • Gene: The sequence of DNA that determines the expression of a given trait.

9. Inheritance in a tiny nutshell • Gene: The sequence of DNA that determines the expression of a given trait. • Most species are diploid: Each gene is present in two copies or alleles, one on each member of a chromosome pair. Each allele is inherited from one parent.

10. Inheritance in a tiny nutshell • Gene: The sequence of DNA that determines the expression of a given trait. • Most species are diploid: Each gene is present in two copies or alleles, one on each member of a chromosome pair. Each allele is inherited from one parent. • One or more genes determine the appearance or performance of an individual for a given trait (e.g., drought tolerance, flower color, seed size, timing of flowering).

11. Inheritance in a tiny nutshell • Gene: The sequence of DNA that determines the expression of a given trait. • Most species are diploid: Each gene is present in two copies or alleles, one on each member of a chromosome pair. Each allele is inherited from one parent. • One or more genes determine the appearance or performance of an individual for a given trait (e.g., drought tolerance, flower color, seed size, timing of flowering). • When the two alleles of a gene are identical, an individual is homozygous for this gene or trait.

12. Inheritance in a tiny nutshell • Gene: The sequence of DNA that determines the expression of a given trait. • Most species are diploid: Each gene is present in two copies or alleles, one on each member of a chromosome pair. Each allele is inherited from one parent. • One or more genes determine the appearance or performance of an individual for a given trait (e.g., drought tolerance, flower color, seed size, timing of flowering). • When the two alleles of a gene are identical, an individual is homozygous for this gene or trait. • When the two alleles of a gene differ, the individual is heterozygous for this gene or trait.

13. Up and running: common vocabulary • Local adaptation: • The process in which natural selection favors different alleles or genetic types (genotypes) in different environments.

14. Up and running: common vocabulary • Local adaptation: • The process in which natural selection favors different alleles or genetic types (genotypes) in different environments.

15. Up and running: common vocabulary • Local adaptation: • The process in which natural selection favors different alleles or genetic types (genotypes) in different environments. • Result: genetic differences between plant populations in locations that differ in attributes such as… • soil quality • climate (temperature, rainfall, date of first frost) • identity of pollinators • presence and composition of competing species • presence of predators • presence and identity of diseases

16. Up and running: common vocabulary • Genetic differentiation • The process and the outcome of genetic divergence among populations, resulting from natural selection.

17. Up and running: common vocabulary • Genetic differentiation • The process and the outcome of genetic divergence among populations, resulting from natural selection. • Genetic differentiation among populations can also result from random processes such as genetic drift and founder effects.

18. Genetic differentiation: example • Broadleaf lupine, Lupinus latifolius (D. L. Doede, 2005) 84 populations sampled; 4 distinct seed zones detected associated with watershed, topography, and climate Populations differ in plant size and flowering time when raised in a common environment

19. Genetic differentiation: example • Broadleaf lupine, Lupinus latifolius 84 populations sampled; 4 distinct seed zones detected associated with watershed, topography, and climate Populations differ in growth form or habit

20. Genetic differentiation: example • Broadleaf lupine, Lupinus latifolius 84 populations sampled; 4 distinct seed zones detected associated with watershed, topography, and climate Populations differ in flower color

21. Up and running: common vocabulary • Genetic drift • Random fluctuations in the frequency of a specific gene in a small isolated population due to chance. • The process by which gene frequencies change at random from generation to generation in small populations due to the chance sampling of different genes among the successful egg and sperm.

22. Up and running: common vocabulary • Genetic drift • Random fluctuations in the frequency of a specific gene in a small isolated population due to chance. • The process by which gene frequencies change at random from generation to generation in small populations due to the chance sampling of different genes among the successful egg and sperm. • Over time, there is a net loss of heterozygosity and an increase in homozygosity until some alleles are lost forever…..

23. Up and running: common vocabulary • Genetic drift Start with 10 alleles Several generations of random sampling Only 6 of the original alleles have left descendants Several generations of random sampling Only 2 of the original alleles (and their descendants) remain.

24. Up and running: common vocabulary Up and running: common vocabulary • Founder effect • Genetic drift observed in a population founded by a small, non-representative sample of a larger population. Rare alleles may become common by chance.

25. Up and running: common vocabulary • Founder effect • Genetic drift observed in a population founded by a small, non-representative sample of a larger population. Rare alleles may become common by chance. • Example: A small group of seeds collected from a large population may contain genotypes that do not fully represent the population. • Small samples from large populations typically include less genetic variation than the original population. • This reduced genetic variation can limit the population’s ability to survive and to persist in a novel environment.

26. Founder effect: example • Hawaiian silverswords • Surviving populations of silverswords (Argyroxiphium sandwicense and A. kaunense: Asteraceae) have experienced severe bottlenecks and are genetically depauperate. A restored population of the Mauna Kea silversword, A. sandwicense, consists of 1500 individuals all derived from a two or three original parents.

27. Up and running: common vocabulary • Genetic swamping or Dilution • Rapid increase in the frequency of an introduced genotype that may lead to the replacement of local genotypes.

28. Up and running: common vocabulary • Genetic swamping or Dilution • Rapid increase in the frequency of an introduced genotype that may lead to the replacement of local genotypes. • Cause: a short-term or long-term fitness advantage of the introduced genotype.

29. Up and running: common vocabulary • Genetic swamping or Dilution • Rapid increase in the frequency of an introduced genotype that may lead to the replacement of local genotypes. • Cause: a short-term or long-term fitness advantage of the introduced genotype. • Consequence: a reduction in genetic variation relative to the initial mixture of resident and introduced genotypes.

30. Up and running: common vocabulary Population genetic processes Genetic phenomena Ecological considerations Inheritance in a nutshell Local adaptation Genetic differentiation Genetic drift Founder effect Genetic swamping Ecotype Heterosis & “hybrid vigor” Inbreeding depression Outbreeding depression Hybrid breakdown

31. Up and running: common vocabulary • Ecotype: • The smallest subdivision of a species, consisting of populations adapted to a particular set of environmental conditions. These populations may be infertile when crossed with other ecotypes of the same species.

32. Up and running: common vocabulary • Ecotype: • The smallest subdivision of a species, consisting of populations adapted to a particular set of environmental conditions. These populations may be infertile when crossed with other ecotypes of the same species. • In other words, ecotypes are genetically distinct populations within a species, resulting from adaptation to local environmental conditions.

33. Up and running: common vocabulary • Ecotype: • The smallest subdivision of a species, consisting of populations adapted to a particular set of environmental conditions. These populations may be infertile when crossed with other ecotypes of the same species. • In other words, ecotypes are genetically distinct populations within a species, resulting from adaptation to local environmental conditions. • G. Turesson. 1922. The species and variety as ecological units.

34. Ecotypes: example Mountain ecotype, erect shrub with hairless leaves Beach ecotype, prostrate habit with pubescent leaves Hybrid leaves Beach ecotype Mountain ecotype Ecotypes of Sida fallax and their hybrids in Hawai’i. A. Beach ecotype. B. Mountain ecotype. C, D, and E: hybrid leaves. F: Beach flower. G. Hybrid flower. H. Mountain flower.

35. Up and running: common vocabulary • Heterosis • Where heterozygotes within a species or within a population have higher fitness than homozygotes. Hybrid varieties of maize are often prized for their consistently high performance

36. Up and running: common vocabulary • Hybrid vigor (“interspecific heterosis”) • Where the hybrids between two species perform better than either of the parent species. Loganberry is a high-performing hybrid between raspberry and blackberry

37. Up and running: common vocabulary • Heterosis and “hybrid vigor” • Where heterozygotes within a species or the hybrids between species have a higher fitness than either of their parents. • Heterozygotes often grow better, are better able to survive, and/or are more fertile than the homozygotes.

38. Up and running: common vocabulary • Heterosis and “hybrid vigor” • Where heterozygotes within a species or the hybrids between species have a higher fitness than either of their parents. • Heterozygotes often grow better, are better able to survive, and/or are more fertile than the homozygotes. • This observation often causes people to think that mixing genotypes from two or more populations is always good.

39. Up and running: common vocabulary • Inbreeding depression • Reduction in performance following mating between very closely related individuals of the same species.

40. Up and running: common vocabulary • Inbreeding depression • Reduction in performance following mating between very closely related individuals of the same species. • The union of gametes produced by very close relatives can generate offspring with high frequencies of (recessive) genetic diseases in homozygous form.

41. Up and running: common vocabulary • Inbreeding depression • Reduction in performance following mating between very closely related individuals of the same species. • The union of gametes produced by very close relatives can generate offspring with high frequencies of (recessive) genetic diseases in homozygous form. • This observation often reinforces the assumption that mixing genotypes from multiple populations will improve the performance of the resulting population.

42. Up and running: common vocabulary • Inbreeding depression

43. Inbreeding depression: example • Port Orford Cedar (Scott E. Kolpak, Richard A. Sniezko, and Christine F. Hayot) • Ovules fertilized by self-pollination are less likely to mature successfully than those fertilized with outcross pollen • Seedings derived from self-pollination are shorter than those produced by outcrossing Seedling height by cross type % filled seed by cross type % Filled seed Height (cm) Outcross Open Self Outcross Self Cross type Cross type

44. Up and running: common vocabulary • Outbreeding depression • Reduction in population performance following hybridization between genetically distinct individuals of the same species. • Mating between genotypes adapted to different environmental conditions can generate offspring that are poorly adapted to the home environments of either parent.

45. Up and running: common vocabulary • Outbreeding depression • Reduction in population performance following hybridization between genetically distinct individuals of the same species. • Mating between genotypes adapted to different environmental conditions can generate offspring that are poorly adapted to the home environments of either parent.

46. Outbreeding depression: example • Lotus scoparius (Fabaceae: deerweed) • The success of crosses between populations decreases with the genetic distance between the populations (Montalvo & Ellstrand, 2001). Mean number of seeds per flower Genetic Distance between crossed plants

47. Up and running: common vocabulary • Hybrid breakdown

48. Up and running: common vocabulary • Hybrid breakdown

49. Up and running: common vocabulary • Hybrid breakdown

50. Up and running: common vocabulary • Hybrid breakdown • “Classic” definition: Where the first-generation hybrid offspring between two species are healthy, but subsequent generations resulting from the matings between these hybrids perform poorly.