The history of biogeography

Prehistory

Humans have always used biogeographic knowledge

First ideas

Aristotle (384 BC - 322 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

World exploration in 18th and 19th centuries

• Specimens were collected, cataloged and compared

Until mid 18th 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?

Age of European Exploration

Age of European Exploration

Carl Linnaeus (1707- 1778)

• Species classification system (hierarchical, binomial) – Kingdom – Phyla – Class – Order – Family – Genera – Species

• Species are immutable • Hypothesis to explain biodiversity

distribution: Paradisical Mountain

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)

Age of European Exploration

Georges-Louis Buffon (1707-1788)

• 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

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)

Age of European Exploration

Johann Reinhold Forster (Cook’s 2nd voyage; 1729-1798)

• 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

Age of European Exploration

Captain James Cook’s Voyages

First - 1768-1771 (red) Second - 1772-1775 (green)

Third – 1776-1779 (blue)

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

Age of Enlightenment

Alexander von Humboldt (1769-1859)

• Father of phytogeography

• Covariation of vegetation and climate

• Invented isobar and isotherm

• Expanded latitudinal biodiversity gradients into elevational gradients

Age of Enlightenment

Agustin de Candolle (1778-1841)

• Species competition for resources as a key factor for species persistence

• Factors other than island area influence biodiversity: isolation, climate, geological history, age

The 19th century

Charles Lyell (1797-1875)

• 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

Charles Darwin (1809-1882)

• 1831 – 5 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 long-distance dispersal in biogeographic distribution of species

Darwin in 1840

Darwin’s voyage

Argentina – discovered large mammalian fossils

Galapagos – fascinating wildlife

Argentinian Fossils

Giant ground sloths

Giant armadillo-like creatures

Galapagos

Galapagos Giant Tortoise

Galapagos Finches

• 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

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”

Alfred Russel Wallace (1823-1913)

• 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)

Wallace Line

• 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

First half of the 20th century

Alfred Wegener (1880-1930)

• Theory of continental drift - 1912 (first introduced by Antonio Snider-Pelligrini in 1858)

• Not widely accepted until the 1960s

• Revolutionized biogeography – rethink reasons for species distributional patterns

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

Ernst Mayr (1893-1969)

• Biological species concept (group of individuals that can reproduce among themselves and not with other groups)

• Insights into mechanisms of allopatric speciation

G. E. Hutchinson (1903-1991)

• Multidimensional niche concept

• Mechanisms of species coexistence

• Father of Limnology

Late 20th century

Robert H. MacArthur (1930-1972) • Mathmatician & theoretical ecologist

• Strong emphasis on hypothesis testing

Edward O. Wilson (1929 – ) • Naturalist & evolutionary biologist

• Global biodiversity and conservation

Theory of Island Biogeography - Mechanistic explanation of species richness - large islands close to mainlands have greater biodiversity than small, isolated islands

Evolution of ideas • Age of European Exploration (early 18th century)

– Catalogue/classify species – Strongly influenced by religion – Single origination of immutable species

• Age of Enlightenment (late 18th century) – Distribution & patterns of biodivsersity – Climate variability important – Species compete

• 19th century – Earth is old – Species are dynamic and respond (i.e. adapt) to biotic/abiotic factors – Species evolve by natural selection, go extinct

• Early 20th century – Geographic distribution of species due to geological (e.g. continental drift) as well as biological

(species coexistence) factors – Mechanisms of speciation & coexistence

• Late 20th century – Island biogeography: conceptual mechanism explaining species richness

Contemporary Biogeography

• Increasing diversification in Biogeography – paleontology, geology, meteorology, botany, zoology

• Technological advances allowed complex analyses

– Personal computers, multivariate statistical techniques

– GIS, remote sensing