The history of biogeography

Transcription

1 The history of biogeography

2 Prehistory Humans have always used biogeographic knowledge

3 First ideas Aristotle (384 BC BC) First one who asked the central biogeographic question (and left a written record): How are organisms distributed around the world? Also had a view of a dynamic and changing Earth

4 Age of European Exploration World exploration in 18 th and 19 th centuries Specimens were collected, cataloged and compared Until mid 18 th century, religion drove naturalists God created all species Earth, climate, species changed little over time, or not at all Single species origination event How could currently isolated animals and plants adapted to different climates coexist on Noah s Ark?

5 Age of European Exploration Carl Linnaeus ( ) Species classification system (hierarchical, binomial) Kingdom Phyla Class Order Family Genera Species Species are immutable Hypothesis to explain biodiversity distribution: Paradisical Mountain

6 Age of European Exploration Linnaeus Paradisical Mountain Hypothesis All species housed on slopes of equatorial mountain-island ~6000 years ago Flood receded, continents expanded, terrestrial species expanded to new sites In accordance with biblical events (Noah s Ark, biblical timeline) and biblical beliefs (species do not change; later abandoned this idea)

7 Age of European Exploration Georges-Louis Buffon ( ) Studied live and fossilized mammals Believed in a single species creation event Recognized climatic shifts & their importance to understanding species spread Critique of Linnaeus: Different regions (even with same environment) often had different species If species were incapable of adaptation, they could not have traveled through hostile environmental barriers from a single

8 Age of European Exploration Buffon s Hypothesis of Species Dispersal Species originated around the north pole during a warm period As globe cooled, species migrated south Species changed and adapted to new environments ( improved or degenerated ) Species survived that were improved, and degenerated species died out Importance of hypothesis: Dynamic climate Adaptation of species Buffon s Law environmentally similar but isolated regions have distinct assemblages of mammals and birds (becomes principle of biogeography)

9 Age of European Exploration Johann Reinhold Forster (Cook s 2 nd voyage; ) Affirmed Buffon s law for plants, mammals, birds Recognized plant assemblages and relationship with specific climatic conditions Insights into patterns of species diversity Habitat (island) size Latitude on species diversity Captain James Cook s Voyages First (red) Second (green) Third (blue)

10 Age of Enlightenment Lots of data regarding species diversity and global distribution had been gathered Sought rational explanations for & conceptual understanding of observed patterns of biodiversity

11 Age of Enlightenment Alexander von Humboldt ( ) Father of phytogeography Covariation of vegetation and climate Invented isobar and isotherm Expanded latitudinal biodiversity gradients into elevational gradients

12 Age of Enlightenment Agustin de Candolle ( ) Species competition for resources as a key factor for species persistence Factors other than island area influence biodiversity: isolation, climate, geological history, age

13 The 19 th century

14 Charles Lyell ( ) Studied geology & fossils Uniformitarianism physical processes now operating are timeless Earth s climate changes & so do species distributions Species go extinct! Multiple creation events & sites Earth must be older than 6,000 yrs

15 Darwin in 1840 Charles Darwin ( ) year voyage on HMS Beagle to South America Collected samples of rocks, plants, animals, fossils Developed the theory of evolution by natural selection; The Origin of Species (1859) Emphasized importance of longdistance dispersal in biogeographic distribution of species

16 Darwin s voyage Galapagos fascinating wildlife Argentina discovered large mammalian fossils

17 Argentinian Fossils Giant ground sloths Giant armadillo-like creatures

18 Galapagos

19 Galapagos Giant Tortoise

20 Galapagos Finches

21 Finches and tortoises - different islands, different appearance Darwin could not connect biblical views with natural evidence Darwin concluded species change over time!! One finch and tortoise diversified to many species Remembered fossils concluded they were ancestors of current armadillo and sloth

22 Did embryonic stages of animals have characteristics of ancestors? Ontogeny recapitulates phylogeny Whales had teeth (descended from sea creatures with teeth?) Snakes had rudimentary legs (descended from lizards?) Human have structures similar to gill (descended from fish?) Species were related in tree of life

23 Alfred Russel Wallace ( ) Self-trained English naturalist Developed the theory of evolution (independently from Darwin) Species evolved due to pressure from competition, predation, and environmental factors that favor one variety over another Father of zoogeography Developed numerous biogeographic principles (box 2.1, p. 33)

24 Wallace Line

25 Species are not immutable, but dynamic responding to biotic/abiotic factors But what explains the geographic distribution of species? -cosmopolitan vs. disjunct species Debate: Dispersalists vs. Extensionists Dispersalists - Long-distance dispersal events (Darwin) Extensionists - Landbridges connecting continents (lack of evidence; Lyell) Further study of dispersal ecology and greater understanding of geological processes (e.g. continental drift) would help settle dispute

26 First half of the 20 th century

27 Alfred Wegener ( ) Theory of continental drift (first introduced by Antonio Snider- Pelligrini in 1858) Not widely accepted until the 1960s Revolutionized biogeography rethink reasons for species distributional patterns

28 Wegener s Theory of Continental Drift Theory: Continents formerly joined Slowly drifting on Earth s surface Evidence: Landmasses fit together like a jigsaw Geological similarity between matching sides of continents Fossil similarities between matching sides of continents Did not know mechanism

29 Ernst Mayr ( ) Biological species concept (group of individuals that can reproduce among themselves and not with other groups) Insights into mechanisms of allopatric speciation

30 G. E. Hutchinson ( ) Multidimensional niche concept Mechanisms of species coexistence Father of Limnology

31 Late 20 th century

32 Theory of Island Biogeography - Mechanistic explanation of species richness - large islands close to mainlands have greater biodiversity than small, isolated islands Robert H. MacArthur ( ) Mathmatician & theoretical ecologist Strong emphasis on hypothesis testing Edward O. Wilson (1929 ) Naturalist & evolutionary biologist Global biodiversity and conservation

33 Evolution of ideas Age of European Exploration (early 18 th century) Catalogue/classify species Strongly influenced by religion Single origination of immutable species Age of Enlightenment (late 18 th century) Distribution & patterns of biodivsersity Climate variability important Species compete 19 th century Earth is old Species are dynamic and respond (i.e. adapt) to biotic/abiotic factors Species evolve by natural selection, go extinct Early 20 th century Geographic distribution of species due to geological (e.g. continental drift) as well as biological (species coexistence) factors Mechanisms of speciation & coexistence Late 20 th century Island biogeography: conceptual mechanism explaining species richness

34 Contemporary Biogeography Increasing diversification in Biogeography paleontology, geology, meteorology, botany, zoology Technological advances allowed complex analyses Personal computers, multivariate statistical techniques GIS, remote sensing

35