The Scope and History of Biogeography Tuesday, January 14th

Origins of Biogeography Knowledge of geographic variation of life on this planet was unavoidable and essential to the survival of ancient societies Scientists would later rediscover these patterns and add many additional insights into the geography of nature during the Age of Exploration Eventually their explanations for the development and distribution of life would include references to past environments, extinct life forms, and competition and predation among species. The geography of nature became the foundation to entirely new fields of science including geology, meteorology, paleontology, evolution, and ecology

Origins of Biogeography “Nothing in biology makes sense except in the light of evolution” Theodosius Dobzansky Fundamental theme of modern biogeography is that few patterns in ecology, evolution, conservation biology, and biological diversity make sense unless viewed in a geographic context Biogeography is the science that attempts to document and understand spatial patterns of biological diversity

Questions posed by Biogeography Why is the species or higher taxonomic group (genus, family, order…) confined to its present range? What enables a species to live where it does, and what prevents it from colonizing other areas? What role does geographic variation in climate, topography, and interactions with other organisms play in limiting the distribution of 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? How does a species come to be confined to its present range? What are a species’ closest relatives, and where can they be found? Where did its ancestors live?

Alligator Distribution

Persistent Themes in Biogeography Classifying geographic regions based on their biotas Reconstructing the historical development of lineages and biotas, including their origin, spread, and diversification Explaining the differences in numbers as well as types of species among geographic areas, and along geographic gradients including those of area, isolation, latitude, elevation, and depth Explaining geographic variation in the characteristics of individuals and populations of closely related species, including trends in morphology, behavior, and demography

Biogeography Subdisciplines Phytogeographers Zoogeographers Ecological biogeography Historical biogeography Analytical biogeography Conservation biogeography

Origins of Biogeography Traditional biogeography is defined as the study of the distribution of organisms, past and present Modern biogeography now includes studies of all patterns of geographic variation in nature - from genes to entire communities and ecosystems - elements of biological diversity that vary across geographic gradients including those of area, isolation, latitude, depth, and elevation

Origins of Biogeography The idea that the Earth is dynamic didn’t begin with Darwin, Linnaeus, and Wallace Aristotle: But if rivers come into being and perish and if the same parts of the Earth are not always moist, the sea also must necessarily change correspondingly, And if in places the sea recedes while in others it encroaches, then evidently the same parts of the Earth as a whole are not always sea, nor always mainland, but in the process of time all change. From Meteorologica, ca 355 BCE

Age of Exploration Natrualist/Explorers were originally driven by a calling to serve God. The thinking being that the mysteries of creation would be revealed as they cataloged the diversity of life. AS this Age continued, it became clear that Noah’s ark would not have been large enough It was also difficult to explain how animals and plants, now isolated and perfectly adapted to dramatically different climates and environmetns, could have coexisted at the landing site of the ark before they spread to populate all regions of the glbe

Carolus Linnaeus 1707-1778 God spoke most clearly through the natural world The world was a dvine museum Believed world was unchanging He releazed the challenge was explaining patterns of diversity and distrubution Linneaus (1781) Paradisical Mountain

George-Louis Lleclerc, Comte de Buffon (1707-1788) Found flaws in Linneaus’s paradiscal mountain Buffon ovserbed that different portions of the flove with the same climatic and environmental condicitons were often inhavited by distinct kinds of plants and animals Second, Buffon noted that species would have had to spread through inhospitible havitats to reach their prefered one after the Flood Buffon (1761) hypothesized that life originated in northwestern Europe during warmer climates and then spread south as climates cooled. During the migrations, populations were separated and became modified Buffon: Man is totallhy a production of heavenl; but the animals are createures of the Earth only. Those of one coninent are not found in another, or if there are a few exceptions, the animals are so changed that tey are hadly to be recognized.

Comte de Bufon

Alexander von Humbolt (1769-1859) Father of Phytogeography The fundamental laws of nature could be discovered through the study of distributions Expanded on Buffon’s Law Floristic zones could also be described along elevational gradients Plant assemblages strongly correlated with local climate

Biogeography of the 19th Century Objectives Study distinctness of regional biotas, their origin and spread, and factors responsivle for diffeences in the numbers and kinds of species among local and regional biotas Important advances in biogeography came only when With a better estimate of the Earth’s age A better understanding of the dynamic nature of continents and oceans A better understanding of the mechanisms involved in the spread and diversification of species

Charles Darwin (1809-1882) On Galapagos, observed different tortoises and finches suggesting that geographic isolation facilitates change Darwin and Wallace provdied the basis for understanding chaanges in the adaptations and distributions of organisms across time and space Darwin argued that long distance dispersal led to isolated biotas

Dispersalists vs Extensionists

Biogeographic Principles Advocated by Alfred Russel Wallace

Biogeography since 1900 Major developments: Acceptance of plate tectonics Development of new phylogenetic methods New ways of conducting research in ecological biogeography Investigations of the mechanisms that limit distributions Climate change Competition, mutualisms, and predation influencing distribution Importance of disturbance

Biogeography since 1900 Robert H MacArthur and E.O. Wilson’s 1963 Equilibrium Theory of Island Biogeography Importance of immigration and extinction