Macroevolution: speciation Tuesday 11/5/13

1. Macroevolution: speciation Tuesday 11/5/13 • Finish up microevolution lecture…… • What is a species? • Biological Species Concept • pre- & post-zygote barriers • Speciation • Rate of Speciation • Allopatric& Sympatric Speciation • adaptive radiation • Understanding Evolutionary Relationships • phylogenies / cladograms • taxonomy

2. Macroevolution: • splitting • evolution of fig 27.21 • So, what is a species? • when is it subspecies vs. full species?

3. Biological Species Concept • defines species based • NOTE: Can not be applied in all context!! • Scientists rely on other criteria when • hybridization does occur • if populations interbreed and produce young, are they always considered the same species?

4. Species in biology have typically be defined based on • different ways for isolation – fig 27.20

5. Prezygotic Barriers: • ecological / habitat isolation • temporal isolation

6. Prezygotic Barriers: • behavioral isolation • differences in • only mate with the individuals

7. Prezygotic Isolating Mechanisms: • Mating is attempted but not successful: • mechanical isolation • gametic isolation -- • receptors on • chemical signaling • sperm might

8. Postzygotic Mechanisms: prevents proper function of zygotes once formed: • hybrids not reproductively successful due to: • zygote mortality • hybrid sterility • hybrids

9. Postzygotic Mechanisms: prevents proper function of zygotes once formed: • F2 fitness  reduced fitness of hybrid’s offspring • NOTE: Hybridization does occur, despite isolating mechanism (though typically rarely). • If hybrids are less fit, or their offspring are less fit,

10. Rate of Speciation: fig 27.22 • Gradualism: • Punctuated equilibrium:

11. Patterns of Speciation: • Nonbranchingevolution (anagenesis): • Branching evolution (cladogenesis):

12. How does speciation occur? Allopatric Speciation: • divergence between populations • if barrier • speciation occurs if & when

13. Speciation and Geographic isolation

14. Adaptive Radiation in Isolate Population • speciation in allopatry • new species colonize other island(s) - (2)

15. Example of adaptive radiation: -- Hawaiian Honeycreepers:

16. Sympatric Speciation • new species emerges within parent population • (1) reproductive barriers emerge due to changes in chromosome # • polyploidy-- • for example -- allopolyploidy - (seen in plants) • hybridization • hybrid has • chromosomes double • four copies • reproductive barrier

17. fig 27.18 Sympatric speciation(2) resulting from diversifying selection • if mating with other • unless • assortative mating -

18. Phylogenies -- hypotheses about evolutionary relationships • Phylogeny - • more closely related --> • assumption more similar --> Systematics: - figure 25.8

19. Shared Primitive (ancestral) Character • Shared Derived Character: • Outgroup: notochord pharyngeal slits • Use of OUTGROUP - helps to determine primitive vs. derived

20. Reading the phylogenetic tree: fig 27.23 • branch points – • who is most closely related to whom…..

21. Homologous vs. Analogous Traits: • Divergences from a common ancestor may result in variation in traits, and blur the lines of descent • Convergent evolution

22. Homologous vs. Analogous Traits: • Homology • Remember: • Analogy

23. Calibrating the cladogram(phylogeny) with a molecular clock: • molecular data can help determine evolutionary relationships • information from fossil records • molecular clock: fig 27.24

24. Three Domain System: • using phylogenetics, scientists now classify organisms into three domains • Domains: • Bacteria • Archaea • Eukarya fig 27.26

25. Taxonomy: naming & classifying of species and groups of species • Hierarchical classification • Latin (scientific) name: