Endemic --a taxon with a distribution restricted to a particular geographic area

1. Endemic--a taxon with a distribution restricted to a particular geographic area

2. 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.

3. The hoatzin is the only species in the avian family Opisthocomidae--found only in northern South America

4. 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

5. 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

6. 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)

7. Often organisms are both evolutionary and climatic--coelacanth

8. Some groups are not endemic and are considered cosmopolitan--widely distributed throughout the world • Homo sapiens • Falco peregrinus • Daphnia genus (water fleas) • Vespertilionidae family

9. Cosmopolitan mammal families • Soricids (shrews) • Sciurids (squirrels and chipmunks) • Cricetids (hamsters and lemmings) • Cervids (deer) • Ursids • Felids • Mustelids (weasels and badgers) • Bovids (cows)

10. Murids (rats) • Canids • Leporids (rabbits)

11. 51 mammal families are endemic to only one biogeographic region

12. 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

13. 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

14. Areas with high degrees of endemism are typically isolated

15. Cosmopolitan species are often better dispersers and have broader ecological tolerances than endemic species

16. 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)

17. Krakatau—island located between Sumatra and Java, was destroyed August 27, 1883, by several volcanic eruptions

18. 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

19. Physiognomy of the island has also changed

20. 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

21. Dispersal infrequently results in range changes but these are important events

22. Three types of dispersal events that may cause range expansion 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

23. 2. Diffusion—individuals spreading out from the margins of a species’ range over several generations Invasion and establishment Very fast range expansion Slowing of range expansion as barriers are reached

24. Cattle egrets in New World

25. 3. Secular migration • Range expansion over hundreds of generations • Evolution of species

26. Mechanisms of dispersal • Active—flying, swimming • Passive—phoresy, wind, water currents, rafting

27. Dispersal routes—classified on their likelihood of being traversed 1. Corridors—Bering landbridge

28. Dispersal routes 2. Filters—dry lowlands between Rockies and Sierra Madre in Mexico

29. Dispersal routes 3. Sweepstakes—colonization of oceanic islands

30. Other types of movements • Seasonal migrations • Irruptions