Sexual reproduction

1. Sexual reproduction Thomas Geburek Department of Genetics Federal Research Centre for Forests, Natural Hazards, and Landscape (BFW) Austria Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

2. Recall: The main source of genetic variation is recombination! Sexual reproduction is a very important component of the genetic system that stores, transmits, creates, tests genetic variation. Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

3. Sexual Systems Dioecious: all trees are either male or female Ginkgo biloba (male) Ginkgo biloba (female) Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

4. Sexual Systems Dioecious: all trees are either male or female Hermaphrodite: individual tree with both male and female functioning flowers. It may have either monoecious flowers (single sex flowers  monoecy) or hermaphrodite (=bisexual) flowers. Monoecious: hermaphrodite tree in which male and female gametes are produced in separated flowers (bisexual)  sex function Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

5. Sexual Systems Example: Mahagony (Swietenia spec.) Morphology  hermaphrodite flowers Functions  monoecious flowers, because anthers or ovaries are vestigial Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

6. red manjack (Cordia collococca) Flowers are clearly hermaphrodite, but sex function varies considerably. Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

7. Monoecious trees are found approx. 75 % in boreal and temperate zones approx. 10 % in tropical zones. Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

8. Sexual Function Sexual function refers to the frequency of the effective sexual types. Bisexuality does not mean that trees function equally as females or males. In monoecy, the sexual function (S) may be estimated by the number of effective female gametes vs. total number of effective gametes. S varies from zero (exclusively males) to one (exclusively females) Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

9. Si = N ♀ i /(N ♀i + N ♂i ) Effective number (N) of gametes can only be roughly estimated. If pollen is in surplus, census (C) ♀ can be regarded as effective. N♂i= (C ♂i /C ♂)C ♀ Si = C ♀i x C ♂/ (C ♀i x C ♂ + C ♀iC ♀) Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

10. Malaysian example Garciniascortechinii tended towards femalenees in a censused 25 ha area in the Pasoh Forest Reserve (West Malaysia). No males recorded, however 68 % of the adult trees fruited(Thomas 1997). Sexual function S = 1.0 Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

11. 0 1.0 0.5 Sexual Function and Structure 1.0 Relative Proportion 0.5 Sexual function Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

12. Dioecy excludes self-pollination thus reduces coancestry among offspring. In bisexual plants coancestry is reduced by • incompatibility systems, • avoidance of self-pollination by spatial separation of males and female stroboli. Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

13. Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

14. Dioecy excludes self-pollination thus reduces coancestry among offspring. In bisexual plants coancestry is also reduced by • incompatibility systems, • avoidance of self-pollination by spatial separation of males and female stroboli, • temporal separation of the flowers (protogyny or protandry) Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

15. Incompatability Systems homomorphic gametophytic self-incompatibility Gene product are ribonucleases (S-RNA-ases) expressed in the pistil constituting a barrier for certain pollen tubes. S-RNA-ase encoded by the same S-allele (from the maternal tree) reacts with the cytoplasm of the pollen carrying the same S-allele through enzymatic degradation of the r-RNA of the pollen tube. Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

16. (1) Homomorphic gametophytic self-incompatibility Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

17. Consequences: Prevents selfing and mating with closely related trees. Number of incompatability alleles determines number of possible crosses. Example: Leucaema diversifolia Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

18. Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

19. Incompatability Systems homomorphic sporophytic self-incompatibility Diploid genome of the pollen grain reacts with the diploid tissue of the receptive plant. Sharing of only one incompatibility allele between prospective mates prevents reproduction success. Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

20. (1) Homomorphic sporophytic self-incompatibility Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

21. Consequences: Prevents selfing and mating with trees sharing only one incompatability allele. Number of incompatability alleles determines number of possible crosses. Example: Ulmus Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

22. Heteromorphic sporophytic self-incompatibility Heterostyly ss Ss ss no yes Ss yes no Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

23. Example: Cordia alliodora Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

24. Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

25. Papaya (Carica papaya) • fruit tree • indigeneous to the American tropics • dioecious Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

26. Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

27. Female (pistillate) tree– functional ovary , no stamens, pollination from separate trees – genotype mm Male (staminate) tree – no ovary, only stamens – genotype M1m Hermaphroditic tree – low temperature gives a shift to femaleness, high temperature gives a shift to maleness - genotype M2m Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

28. Possible crosses mm (pistillate) x M1m (staminate)  1 mm : 1 M1m M2m (hermaphroditic) x M2m (hermaphroditic)  1 M2M2 (lethal) : 2 M2m : 1 mm (pistillate) Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

29. Incompatability Systems post-zygotic • Conifers have no pre-zygotic incompatibility system. • Embryonic abortion due to early acting inbreeding • lethal recessive mutants embryonic lethal equivalents or embryonic lethals Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

30. Embryonic lethals • Different models • Number can be estimated by Embryonic lethals = - 4 log e x relative self fertility relative self fertility = sound seed set after self-pollination sound seed set after cross -pollination Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

31. Embryonic lethals post-zygotic Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

32. Prediction of empty seeds and proportion of selfed seeds (example for 10 embryonic lethals) empty seeds proportion of selfed seeds Selfed Pollen Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

33. Pollination and pollen movement • Wind-pollinated tropical species, e.g. Shorea robusta, Artocarpus heterophylla, Atelia herbert-smithii. • Wind-dispersed pollen are produced in surplus and distributed undirectionally. Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

34. Pollination and pollen movement Morphology of ovulate cone maximizes the probability of species- specific pollen capture through close-proximity interaction. Unidirectional wind is deflected into cyclonic vortices. Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

35. Pollination and pollen movement Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

36. Pollination and pollen movement Fd = F0e-kd ρ = 1.205 kg/m3, μ = 1.83 x 10 -5 kg/m s Pollen Frequency Distance Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

37. Stoke‘s law – Estimation of the sedimentation velocity of spherical bodies r = radius of the pollen grain (m), g = gravity (m/s2), δ = density of pollen (kg/m3), ρ = density of air (kg/m3), μ = viscosity (absolute) of air (kg/m s). ρ = 1.205 kg/m3, μ = 1.83 x 10 -5 kg/m s European example: Larix decidua experimental  0,130 m/s predicted  0,127 m/s Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

38. Pollination and pollen movement Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

39. Pollination and pollen movement Effective pollen distribution can be studied by • pollen trapping of single trees • pollen trapping of radioactive-labelled sources • paternity analysis. Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

40. Animal-pollinations enhanced by visual cues Showy petals or sepals with obvious shape, size, and color. Butterflies and birds are attracted to red and yellow colors. Bees have vision that is shifted toward the blue end of our visible spectrum. White or very pale color are importsant for nocturnal vectors. olfactory cues rewards for the visiting vector (pollen, nectar) Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

41. Vector related questions: Alternate host species to provide food ? Example: Byrsonia crassifolia Pattern of vector movement e.g. „trap lining“ = day to day repeated vector movement over a relatively large area (larger bees, bat, butterfly, hummingbirds), typical for trees with relatively few flowers over extended periods  pronounced long distance gene flow, non random mating events Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

42. Mass flowering tree species  Higher selfing rate, close-distance intertree movement Example: Moca (Andira inermis): 70 bee species, only 8 were conspecific) Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

43. Mating Outcrossing rates may vary • from year to year • within the crown (in the apex higher rates) • with stand density. Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

44. Mating

46. By now you should know ........... Training Workshop on Forest Biodiversity, June 2006, Kuala Lumpur, Malaysia

49. Natural seed dissemination (migration) Wind-dispersed