Biogeography

1. Biogeography Study of distribution of organisms

2. Biogeography • Comparative observational science • Experiments – limited utility • Multiple scales • Comparative has uses, though • Synthetic science

3. Subjects Used in Biogeography • Anatomy • Physiology • Taxonomy • Developmental • Evolution • Geology • Geography • Ecology • Climatology, Paleontology……

4. Relevance of Biogeography • What enables a species to live where it doe, and what prevents it from colonizing other areas? • What are a species closest relatives and where can they be found? Where did its ancestors live? • How have historical events shaped a species’ distribution?

5. Overarching question: What shapes global patterns of biodiversity?

6. The Importance of Time • Historical biogeography • Ecological biogeography • Paleoecology

7. “While the process of science owes much to admirable human traits……..it is also retarded by characteristics such as prejudice, jealousy, short-sightedness, and stupidity.”

8. History of Biogeography • Roots from questions that developed during the “Age of Exploration” • Shares common lineage with ecology • Early questions • From where did life come? • How did it diversify across the planet?

9. Persistent Themes in Biogeography • Classifying geographic regions based on their biota • Reconstructing historical development or lineages and biota, including their origin, spread, and diversification • Explaining differences in numbers and types of species among geographic areas, and along geographic gradients • Explaining geographic variation in characteristics of individuals and populations of closely related species

10. Age of Exploration • 250 yr ago, only 1% of species known today identified • Mission – reveal mysteries of creation by learning of the diversity of life • Prevailing view – stasis • With increasing identification of species, was a clear need for organization

11. Carolus Linneaus (1707 – 1778) • Understanding organization would lead to knowing Creator’s plan • Took static view of Earth • Explain origin and spread of life • Challenge was to explain diversity and distribution

12. Carolus Linneaus (1707 – 1778) • How could life have spread from Paradise then landing spot of the Ark • Linnaeus – “Paradisical Mountain” – a mountain island life along the slopes, perfectly adapted for biotic and abiotic conditions at their “station” • Based on known conditions of tropical mountains • Later formation of land allowed spread

13. Comte de Buffon (1707 – 1788) • Contemporary of Linaeus • Disagreed with his view of spread of life (living and fossil specimens) • Places with same climate had different species • Inhospitable environment around Mount Ararat • Proposed origin in northern Europe

14. Buffon’s hypothesis – climate was cooler at time allowing species to move to new areas and change • Key points – climate and species were dynamic (central to modern biogeographic theory and precursor to development of evolutionary theory)

15. Comte de Buffon (1707 – 1788) • Buffon’s Law – Environmentally similar but separated regions have different species of birds and mammals • Considered first principle of biogeography • Later studies by Joseph Banks and Johann Forster found Buffon’s Law applied to plants

16. Phytogeography • End of 18th century – natural theology still primary biological theory • Willdenow (1765-1812) and Humboldt (1769-1859) – phytogeography – geographic distribution of plants • Studies of plant distribution on Andes mountain (5,600 m elevation Mt. Chimbaruzo

17. Phytogeography • Identified floristic belts from tropical to arctic • Observed plant communities closely associated with local climate • Hints at competition (Candolle) Mt. Chimbaruzo

18. Biogeography of 19th Century • First three themes established • Classifying geographic regions based on their biota • Reconstructing historical development or lineages and biota, including their origin, spread, and diversification • Explaining differences in numbers and types of species among geographic areas, and along geographic gradients

19. Biogeography of 19th Century • Buffon’s Law • Early biogeographers tested • Classify regions based on biota (theme 1) • Reconstructing origin and spread of life (theme 2) • Changes along gradients (theme 3) • Established approachs still used • Perception of static earth and life to dynamic

20. Limitations • Number of local species increased with area • Number of species decreased from equator • Needed to move to next step (rigorous testing) but first needed WHY??????

21. Needs for Better Understanding • Better estimate of age of Earth (natural theology and 6,000 yr) • Understanding of dynamic nature of continents and oceans • Understanding of spread and diversification – dispersal, vicariance, extinction, evolution)

22. Early Advances of 19th Century • Borngniart – father of paleobotany • Lyell – father of geology • Both used fossil record to conclude climate changes over time (life forms of tropical climates in northern Europe • Lyell – changes in sea level and the lifting and erosion of mountains; extinction • New species arose through new creations after extinctions; new species created for new climate

23. Early Advances of 19th Century • Lyell proposed uniformitarianism • Also, realization that processes occur slowly (gradualism) • Time needed for geological processes + continual replacement of biota = Earth much older than 6,000 years

24. Four British Scientists • Charles Darwin, Joseph Hooker, Philip Sclater, Alfred Russell Wallace • Naturalists, traveling the world and discovering diversity • Shared their observations, building a broader image of life • Did not agree on all points

25. Darwin • Origin of Species – contribution is obvious • Proposed ideas on dispersal of life (countering Agassiz’s view of point near creation) • The “dispersalist” view made dispersal dynamic • Disagreement then moved to mechanisms of dispersal (dispersalists vs. extensionists)

26. Extensionists & Land Bridges

27. Further Contributions • Hooker – study of southern hemisphere plant distributions lead to development of vicariance biogeography • Sclater – used distribution of passerine (perching) birds to develop a system of six biogeographic regions still used today • Also developed zones based on marine mammals (Fig. 2.8)

29. Wallace • Greatest contributions to biogeography (father of zoogeography) • Expanded view provided by Sclater’s zones • Established many of the basic principles of biogeography (see Box 2.1) • Observed a distinct change in fauna of Southeast Asia and Australasia (Wallace Line)

31. Other 19th Century Contributions • Bergmann’s rule – homeotherms, body size, and surface-to-volume ratio from poles • Allen’s rule – limbs of birds and mammals become shorter and stouter as move from equator. • Cope’s rule – groups tend to increase in size during their evolution • Limitation of generalities but open new thoughts

32. Other 19th Century Contributions • Merriam’s life zones • Study of elevational changes – found vegetation types and species composition are similar to longitudinal patterns • Confirmed Humboldt’s work

35. Twentieth Century • Burdgeoning info from paleontology • Origin, dispersal, radiation, and decline of terrestrial vertebrates • Development of phylogenies • New groups rise • Increase in number of species • Radiate to fill niches and expand range • Still – question of how dispersed

36. Twentieth Century • Relationships between geological and ecological properties of environment • Patterns of morphological variation • Coincided with Modern Synthesis • Linking lead to formulation of biological species concept (Ernst Mayr) • Also identified allopatric speciation

37. Continental Drift • Earth’s crust believed fixed until 1960s • Continental drift 1st proposed 1858 • Resurfaced by Wegener and Taylor using geological and ecological evidence • Criticized and denied until evidence became overwhelming • Changed dispersal from land bridges to movements of continents

38. New Phylogenetic Methods • Continental drift lead to study of disjunctions • Vicariance biogeography • Examination and revision of phylogenies

39. Further Aids • Computers • Geographic information systems • Geostatistics