Biogeography

1. Biogeography By Michelle Cockrell

2. ASKS • Why is a species or higher taxonomic group confined to its present range? • What enables a species to live where it does, & what prevents it from colonizing other areas? • What role does geographic variation in climate, topography, & interactions with other organisms play in limiting the distribution of a species? • How do different kinds of organisms replace each other as we go up a mountain or move from a rocky shore to a sandy beach nearby? • How does a species come to be confined to its present range? • What are a species’ closest relatives, & where can they be found? Where did its ancestors live?

3. How have historical events – such as continental drift, Pleistocene glaciation, & recent climatic change – shaped a species’ distribution? • Why are animals and plants of large, isolated regions – such as Australia, New Caledonia, & Madagascar – so distinctive? • Why are some groups of closely related species confined to the same region, while others are found on opposite sides of the world? • Why are there so many more species in the tropics than at temperate or arctic latitudes? • How are isolated oceanic islands colonized, & why are there nearly always fewer species on islands than in the same kinds of habitats on continents?

4. Biogeography is: • The study of the distributions of organisms in space and time. • How does biological diversity vary over the surface of the Earth? • Attempts to ask and answer: Which? Where? How? Why? And Why Not? • Includes plant and animal species; in their past & present habitat, interim living sites, and/or survival locales

5. History • Aristotle – climate and geography determined an organism’s form • George-Louis LeClerk, Compte de Buffon – • 1st to offer a method to explain distribution patterns • Organisms changed over time to get along with their environment • 1st principle – environmentally similar but isolated regions have distinct assemblages of mammals & birds (Buffon’s Law) • AugustinPyramus de Candolle – • beginnings of ecological and historical biogeography • Recognized limiting factor of competition & problem of dispersal • Phillip LutleySchlater – each species created within & over the geographical area which it now occupies • Charles Darwin – • suggests that animals change to fill the niche available to them (finches) • Suggests that some of the differences between floras & faunas of the separate continents might have resulted from their having separate evolutionary histories.

6. History cont’d • Alfred Russel Wallace – • created 6 biogeographic regions based on the congruent patterns of endemic species • Identified & commented on many aspects of biogeography that still occupy us today: • Effects of climate, extinctions, dispersal, competition, predation & adaptive radiation • Need to be knowledgeable about past & present faunas, fossils & stratigraphy • Distribution of organisms might indicate land connections

7. History cont’d • Alfred Lothar Wegener – • Proposed continents were once connected = Pangea

8. History cont’d • Leon Croizat – • “Earth and life evolve together.” • Concept of a dynamic Earth evolving along with the organisms that inhabit it = Panbiogeography • Rejected concept of origin in a limited area & that of dispersal. Organisms always occupied the areas where we see them. Idea of vicariance. • Used a vast array of distributional data, representing each biogeographical pattern as a ‘track’, connecting its known area of distribution. Tracks of similar taxa combined to form a generalized track that connected different regions of the world.

9. 20th Century • Earth’s geography still assumed to be stable. Unable to explain the distribution of the glossopterus flora. • 60’s – Invention of techniques that used magnetized particles in rocks to trace movement of the rocks & of the land masses in which they lay

10. 20th Century cont’d • If continents never moved, these “fossil compasses” should all point to present magnetic poles • Types of rocks laid down in the continents also shows this. • Also supported and confirmed by study of the ocean floor.

11. Divisions in Biogeography • Ecological biogeography – study of distributions & geographic variation of biotas, with special emphasis on the influences of interations between organisms and their abiotic and biotic environments. • Historical biogeography – study of development of lineages and biotas including their origin, dispersal and extinction • 9 basic approaches

12. Patterns of Interest • Endemism – How did a taxa come to be endemic in an area? • Provincialism – If multiple taxa share same endemism, do they share same historical cause for present distribution? • Disjunction – Taxon on both sides of a barrier, is said to have disjunct distribution • Phylogeny – Hypothesis about distribution, also implicitly makes a statement about phylogeny. • Fossil record – Rich source of data on past distributions. • Historical Geology – Geologic action has a profound evolutionary effect. (continents coming together & moving apart; sea level rising & falling, glacial ice)

13. Processes of Biogeography • Dispersal – movement of organisms away from their point of origin. Basis that taxa are distributed via physiological adaptation and locomotion on a static Earth. • Vicariance – some barrier to genetic exchange causes the separation of the related taxa. Proposed in response to the discovery of a dynamic Earth. Organisms are forced to move (rising sea level) or move unwittingly (continental drift).

14. Processes of Biogeography • Speciation – evolutionary development of a biological species, as by geographical isolation of a group of individuals from the main stock. Formation of a new biological species by the development or branching of one species into 2 or more genetically distinct ones. • Extinction – fact of being extinguished; suppressed; coming to an end or dying out

15. Conclusion • Naturally integrative field of study that encompasses a broad range of methods, data, habitats, and organisms. • Helps us understand our planet; its geography, geology, and organisms, where they have interacted through time, evolving together to form the places we know today. • Comparative science that interprets the complexity of relationships and distributions of life on earth with respect to its geological history. • Common goal: to understand the relationship between life and its distribution.

16. Literature Cited • Cox, C. B. & Moore, P.D. 2005. 7th ed. Biogeography: An Ecological and Evolutionary Approach. Blackwell Publishing. • Crisci, J.V., Katinas, L., & Posadas, P. 2003. Historical Biogeography, An Introduction. Harvard University Press. • Huggett, R. J. 2004. 2nd ed. Fundamentals of Biogeography. Routledge. • Lomolino, M.V., Riddle, B.R. & Brown, J. H. 2006. 3rd ed. Biogeography. Sinauer Associates, Inc. • Parenti, L, & Ebach, M 2009, Comparative Biogeography : Discovering And Classifying Biogeographical Patterns Of A Dynamic Earth, University of California Press, eBook Collection (EBSCOhost). • Williams, D, Ebach, M, & Nelson, G 2008, Foundations Of Systematics And Biogeography, Springer, eBook Collection (EBSCOhost) • http://biomed.brown.edu/Courses/BIO48/29.Biogeography.HTML • http://evolution.berkeley.edu/evosite/history/biogeography.shtml • http://www.geo.arizona.edu/Antevs/ecol438/lect02.html • http://www.nyu.edu/projects/fitch/courses/evolution/html/geographic_distribution.html • http://www.nyu.edu/projects/fitch/courses/evolution/html/biogeography.html