Systematics

1. Systematics • Study of pattern and processes associated with biological diversity and diversification • Taxonomy – study of classification (hierarchy, naming  Diversity) • Phylogenetics – study of evolutionary relationships between species and groups (Diversification)

4. Species Concept • Biological species concept – definition • All species concepts have limitations • Classification is a human construct • Importance of defining a species

5. Phylogenetics • Homologies

6. Phylogenetics • Convergence

7. Phylogenetics • Apomorphy – derived trait • Pleisomorphy – primitive trait

8. Subspecies Populations – coat color of subspecies match local substrate

9. Evolution • Macroevolution – lineages of species and major groups, changes in diversity • Microevolution – changes in species, short and longer term; contemporary species • Not segregated; difference in scale

10. Macroevolution • Evolution does not proceed at a uniform rate • Bradytelic – lineages changing at slower rates than typical • Tachytelitic – faster rates than typical • Horotelic - typical

11. Punctuated Equilibrium • Proposed abrupt changes in lineages following long periods of stasis • Mass extinctions  adaptive radiation • Does not contradict natural selection; still a key process in punctuated equilibrium • Gradualism also occurs

13. Gradualism

14. Macroevolution • Rapid Radiation not always with mass extinctions • Cambrian Explosion • Mass extinctions may not be random • Species selection (large sp. end Cretacrous

15. Mechanisms of Evolution • Mutation • Genetic drift • Gene flow • Natural selection

16. Adaptation and Range Expansion • Range of a species includes range of populations • Populations on edge of range may adapt to a limiting condition • Some species may not have capacity to adapt morphologically, physiologically, or behaviorally peripheral conditions

17. Adaptation and Gene Flow • Gene flow changes allele frequencies of populations • Can, however, homogenize gene pool through exchanges between populations • Restricts further adaptation to local conditions • Other limitations to adaptation limit range expansion (not all species have wide ranges)

18. Distribution of karyotypes of Palestine mole rat (Nannospalax ehrenbergei) • Lack of overlap  reduced gene flow

19. Geographic Variation • Geographic isolation facilitates genetic drift and natural selection • Impedes gene flow • Genetic drift – isolation of small populations • Founder effect

20. Divergence of monarch flycatcher • Founder effect – colonizers of islands created gene pool for each

21. Allopatric Speciation • Speciation resulting from geographic isolation • Broader definition applying environmental and physical barriers • Dispersal barriers in heterogeneous environment • Geographic isolation after dispersing to another habitat (e.g., island to island)

22. Allopatric Speciation: Vicariance Endemic Mad. All in Family Ranidae

23. Sympatric Speciation and Adaptive Radiation

24. Extinction • Changing of the guard (dominance in given niches) • Cephalopod molluscs  teleost fishes • Dinosaurs & reptiles  birds and mammals • Species are eliminated or supplanted in their lineages

25. Extinction • Probability of extinction independent of evolutionary age • Is related to taxonomic and ecological status • Small, herbivorous mammals lower extinction rates than large carnivores • Same true for marine invertebrates • Ties back to point about more niches for small organisms?

26. Extinction of Species • Primary causal mechanisms for extinction • Reduction of population sizes • Habitat changes

28. What pushes numbers of a species down to the point where it is pushed to extinction?

29. Fossil Record and Mass Extinctions • Many events, many hypotheses • Pleistocene – megafauna of N. and S. Amer. 8,000 – 15,000 yr ago • Once thought to be climate change from recession of glaciers • More evidence that human colonization was a major contributor

30. Fossil Record and Mass Extinctions • Permian-Triassic 250 mya • 96% of marine species lost • Causal Agent? • Climate change but how • Glaciation • Global warming • Massive volcanic activity • Continental drift

31. > 100 Species 4 - 5 Species Seabed in P-T before and after mass extinction

32. Species Selection • What leads to species surviving and radiating after extinctions? • Appear to be key traits • Remaining species in range also a factor

33. Expansion of mammals after K-T extinction (65 mya) • Filled niches left behind by dinosaurs and reptiles pushed to extinction

34. Placental Mammals • Found globally in fossil record • Few extant species in N. & S. America • Australian marsupials • Why? • Adaptive radiation in absence of dominant reptiles • Later natural and human intro of placentals

35. Dispersal Advantage

36. Replacement