lecture 16 Flashcards
biogeography
study of distributions of biodiversity, both past and present.
- high interdisciplinary: history, biology, geography, geology, ecology, conservation, evolution, systematics, genetics, climate, and many more…
- differs from other fields of science: comparative and observational, takes advantage of natural experiments.
somewhere between 2 million to 100 million species on earth
- most species are restricted to a small geographic area and a narrow range of environmental conditions.
- biogeographic patterns are a consequence of the ways in which the limited geographic ranges of millions of species overlap and replace each other over the earth.
themes in biogeography
- classify geographic regions based on their biotas.
- reconstruct the origins, spread, and diversification of lineages and biotas.
- understand the differences in diversity of species among geographic areas, and along geographic gradients (climate, latitude, elevation, and depth).
- explaining geographic variation in the characteristics of closely related species, including trends in morphology, behavior and demography.
aristotle (384 BC - 322 BC)
how are organisms distributed around the world? viewed earth as changing and dynamic. explained variation in life over space and time.
age of european exploration
world exploration in 18th and 19th centuries.
up to the mid 18th century
religious explanations for patterns of diversity.
- god created all species.
- little/no change in earth, climate, or species through time.
carl linnaeus (1700s)
- provided a necessary method for classification.
- believed that God speaks through nature.
- Paradisical Mountain 6,000 years ago - all life originated at the equator on the slopes of a “Paradisical Mountain.” each species adapted to a particular habitat along the slope.
- mount arourat in turkey - where Noah’s Ark landed, and species colonized mountain during flooding.
- deserts and rainforests? remote islands?
georges-louis buffon (1707-1788)
- species dispersal hypothesis: single species creation/origination at north pole during warm period, followed by southern migration and adaption to new environments.
- importance: dynamic climate + species adaption.
- Buffon’s law: environmentally similar but isolated areas have distinct assemblages of birds and mammals.
sir joseph banks (1743-1820)
Cook’s first voyage. collected over 1,000 new plant species and support for Buffon’s law.
johann reinhold forster (1729-1798)
cook’s second voyage. described global botantical regions and support for Buffon’s law.
- latitudinal diversity gradient - diversity down from equator to pole.
- island biogeography - size and species richness.
19th century “golden age for biogeography”
- age of earth.
- dynamic nature of the earth’s surface.
- origin and spread of biological diversity.
alexander von humboldt (1769-1859)
- covariation of vegetation and climate.
- pytogeography.
- elevational diversity gradient.
augustin de candolle (1778-1841)
- species competition for resources a key factor for persistence.
- climate, geology, and age are factors in biodiversity.
adolphe brongniary (1801-1876)
- reconstructed ancient climates using fossil plants.
- found tropical fossils in temperate areas: climate change.
charles lyell (1797-1875)
- species go extinct, species distributions change.
- earth must be older than 6,00 years.
charles darwin (1809-1882)
- theory of evolution by natural selection.
- importance of long0distance dispersal in biogeography.
how do species get to isolated islands, and across oceans?
- dispersalists - long0dsitance dispersal.
- extensionists - landbridges connecting continents.
> proposed a variety of vanished land bridges to account for the observed distributions of terrestrial organisms.
alfred russel wallace (1823-1913)
- geography affected the ranges of species.
- rivers and mountain ranges marked the boundaries of species.
- similar climate regions contained very different animals.
- biogeography was a record of inheritance.
- recognized six biogeographical regions on earth, and Wallace’s line divided the Oriental and the Australian regions.
continental drift
continents formerly joined together. slowly drifting on earth’s surface (moved by waves and tides).
- evidence: continents fit together nicely, geological similarities, and fossil similarities.
plate tectonics
1960s; mapping of the ocean floor helped find mechanisms for continental drift.
theory of island biogeography
Robert MacArthur (1930-1972) and Edward Wilson (1929-); mechanisms to explain species richness on islands.
- extinction rate higher for smaller islands.
- immigration rate higher for larger islands.
- immigrations rate higher for near islands and lower for far islands.
phylogenetic methods in biogeography
4 general types:
- diffusion models.
- island models.
- hierarchical vicariance model.
- reticulate model.
diffusion model
trace the geographic spread of species across a continuous landscape, both through time, across space. combine genetics + spatial analysis (GIS).
island model
areas fall into discrete categories (islands are one example). estimate the rate of movement between each discrete area.
- equal dispersal rate, steeping stone, and general with carrying capacities.
hierarchical vicariance model (HVM)
areas fall into discrete categories. different area configurations over time. species can only occur in one area.
- event based methods: vicariance, dispersal, and extinction.
reticulate model
areas fall into discrete categories. different area configuration over time. species can occur in more than one area.
- range expansion (geodispersal) and range contraction (local extinction).
- duplication (within area diversification) and alloperipatric speciation (one daughter within one area).
- NOT ALLOWED: sympatric speciation (across multiple areas) and classical vicariance (both daughters in > 1 area).
