Plant Speciation – Part 1

1. Plant Speciation – Part 1 Spring 2011

2. Major topics • Variation in plant populations and species (1) • Gene flow and reproductive isolating barriers (1) • Speciation mechanisms (2) • Species concepts (2)

3. A B C D E F Cladogenesis Cladogenesis Cladogenesis Anagenesis Cladogenesis

4. Biological Variation • All populations of organisms have inherent variation within them – a range of genetic variation of which part is expressed as phenotypic variation • Influences of the environment can change how this variation is expressed = phenotypic plasticity • Observations by biologists can be interpreted in a number of ways to determine the similarities or differences in groups of organisms, depending on which characteristics are measured or emphasized • Need to understand speciation (the process) in order to understand patterns of diversity (and vice versa) and to provide a means to define species

5. Variation in Plant Populations and Species

6. Figure 6.4 from the text Variation in the orchid labellum

7. Clinal variation within a species

8. One P. jeffreyi ecotype is adapted to serpentine soils. This ecotype has less overall genetic diversity than ecotypes of this species adapted to more fertile soils. Figure 6.6 from the text

9. Genetic variation within and among species of native American canes

10. Mutation is the ultimate source of all genetic diversity. Figure 6.7 from the text

11. Types of mutations • Point mutations (Fig. 6.7) • Insertions, deletions, inversions, duplications of parts of a chromosome • Gains or losses of whole chromosomes (aneuploidy) • Changes in whole genomes (the full set of chromosomes in the nucleus) (polyploidy)

12. Genetic Recombination Figure 6.8 from the text

13. Review of Mitosis and Meiosis http://www.pbs.org/wgbh/nova/miracle/divide.html

14. Genetic Drift: chance fixation of genes (alleles) in small populations (5/10 plants leave offspring) (2/10 plants leave offspring) Generation 3 Generation 2 Generation 1

15. Gene flow and reproductive isolating barriers

16. Gene flow • Gene flow = exchange of genes (alleles) between populations • In plants, occurs through the dispersal of pollen or fruits/seeds • Expected to occur between populations of the same species, but in plants also occurs between populations of different species (hybridization)

17. Usually measured in meters, but can occur over long distances. Figure 6.9 from the text

18. Gene flow • Gene flow between populations of a species tends to maintain the cohesiveness of a species • Lack of gene flow (due to reproductive isolating barriers) is normally required for speciation to occur

19. Reproductive Isolating Barriers Table 6.1 from the text

20. Habitat isolation Prairie Woodland White lady’s slipper Yellow lady’s slipper

21. Adaptation to different pollinators Figure 6.13 from the text

22. Figure 6.14 from the text

23. Habitat isolation & floral isolation Columbines (Aquilegia) in California Aquilegia formosa mesic sites < 3,050 m Aquilegia pubescens exposed, xeric sites > 2,750 m

24. Table 4.1 from the text

25. Beetle pollination is relatively unspecialized

26. Figure 4.23 from the text

27. Moraceae – The Fig and The Fig Wasp

28. Breeding Systems • Outcrossing = fertilization between different individuals; depends on ability to screen pollen by the stigma and style (incompatibility) • Uniparental reproduction • Self-fertilization (pollen from a flower fertilizes ovules of the same individual) • Agamospermy (production of seed without fertilization)

29. Breeding systems are not necessarily mutually exclusive! Later season, closed, self- pollinated flowers in Viola Early season, open, cross- pollinated flowers in Viola

30. http://www.youtube.com/watch?v=4YQ5q1cjEU4