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Levels of endemism
• The rodent family Heteromyidae is endemic to the Nearctic and Neotropical regions
• The genus Dipodomys, the kangaroos rats, is restricted to North America and Mexico
• The species Dipodomys stephensi is endemic to southern California.
• The hoatzin is the only species in the avian family Opisthocomidae--found only in northern South America
• Devil's Hole pupfish population is 38 individuals (as of April 2006) which live in one pool of 60 square meters in the Mohave Desert of Nevada
Endemics may be classified by place of origin
• autochthonous endemics exist today where they originated; silversword subspecies of Hawaii
• allochthonous endemics exist today in an area apart from where they originated. Ex. tuatara
Biogeographic relict--a surviving taxon from a group that was once widespread and/or
diverse • evolutionary (or taxonomic) relict--the only
survivor of a once more-diverse taxonomic group (ex. tuatara)
• climatic relict--species whose geographic ranges have constricted due to recent climatic changes (ex. musk ox)
Some groups are not endemic and are considered cosmopolitan--widely distributed
throughout the world • Homo sapiens
• Falco peregrinus
• Daphnia genus (water fleas)
• Vespertilionidae family
Cosmopolitan mammal families
• Soricids (shrews)• Sciurids (squirrels and chipmunks)• Cricetids (hamsters and lemmings)• Cervids (deer)• Ursids• Felids• Mustelids (weasels and badgers)• Bovids (cows)
• Cosmopolitan groups are likely to be:
• Eurytopic—ecologically tolerant, with efficient dispersal mechanisms
• Endemics with very restricted ranges are likely to be:
• Stenotopic—specific preferences and limited ecological tolerance
Rapoport made further distinctions
• Endemics--species found in only one biogeographic region
• Characteristic species--species found in two biogeographic regions
• Semicosmopolitan species--species found in three or four biogeographic regions
• Cosmopolitan species--found in five or more biogeographic regions
Cosmopolitan species are often better dispersers and have
broader ecological tolerances than endemic species
Lake Baikal
• Largest freshwater lake in world
• Deepest lake
• May be oldest lake
• Lake is in a rift valley
• Huge percentage of endemic forms (of 1550 and 1085 animals and plants in lake, 1000 are endemic)
Krakatau—island located between Sumatra and Java, was destroyed August 27, 1883, by
several volcanic eruptions
Opportunity to watch the assemblage of a
community from nothing • May 1884—one tiny spider, spinning a web• Fall 1884-a few shoots of grass, probably two
species• 1886—15 species of grasses and shrubs• 1897—49 species of plants• 1928—nearly 300 species of plants• 1984-85—600 invertebrate species, nine bat
species, two rat species, nine reptiles species, 30 land bird species
Dispersal--the movement of organisms away
from their point of origin
• Organisms balance need to avoid competition/mating with relatives with need to stay in environment they are adapted to
1. Jump dispersal-long-distance dispersal over a relatively short time period
• Easier for some organisms than others• Great element of chance in which species
reach an area
Three types of dispersal events that may causerange expansion
2. Diffusion—individuals spreading out from the margins of a species’ range over several
generationsInvasion and establishment
Very fast range expansion
Slowing of range expansion as barriers are reached