Ch 9Key concepts terms Biogeography concepts Biome faunal

Ch. 9—Key concepts & terms • Biogeography concepts – – – Biome / faunal realm Dispersal routes and barriers Centers of dispersal Latitudinal diversity gradient Island biogeography • Paleobiogeography and plate tectonics – – Pangaea Viking funeral ships / Noah’s Ark Accreted terranes Mammalian paleobiogeography Fossils & Evolution—Chapter 9 1

Chapter 9—Biogeography • Biogeography is the study of the geographic distribution of plants and animals (on a scale larger than that of ecologic analysis) • Biogeography is intimately linked with geology because the modern distribution of organisms has arisen over millions of years, in response to changes in climate and geography • Paleobiogeography is concerned with determining the geographic ranges of extinct taxa and geographic expansion from evolutionary centers of origin Fossils & Evolution—Chapter 9 2

Biomes • Biome = a broadly homogeneous association of plants and animals that occurs over a large area of land – Governed by climate • A given biome cannot occur in widely separated land areas (e. g. , different continents) because of barriers to dispersal • Faunal realms usually correspond with portions of continents or even groups of continents Fossils & Evolution—Chapter 9 3

North American biomes tundra coniferous forest rain forest temperate deciduous forest cold desert hot desert temperate Fossils & Evolution—Chapter 9 grassland 4

Terrestrial faunal realms Fossils & Evolution—Chapter 9 5

Paleobiogeography • Paleobiogeography is concerned with determining the geographic ranges of extinct taxa and geographic expansion from evolutionary centers of origin Fossils & Evolution—Chapter 9 6

Dispersal routes and barriers • Biogeographic routes and barriers vary in the degree to which they limit migration (virtually no barrier is absolute) – Corridors = unobstructed migration routes (e. g. , Bering land bridge during Tertiary) – Sweepstakes routes = dispersal routes that are crossed rarely and only by chance (e. g. , terrestrial vertebrate rafted across narrow ocean) – Filters = intermediate between corridor and sweepstakes (sometimes one-way only) • Plate tectonics can cause changes in the nature of barriers Fossils & Evolution—Chapter 9 7

Bering Land Bridge (Paleogene through Wisconsin glacial stage) Fossils & Evolution—Chapter 9 8

Sweepstakes to Corridor transition (or corridor to sweepstakes? ) • Isthmus of Panama – No isthmus existed for most of Cenozoic time – South American mammal fauna was endemic with only a few immigrants via sweepstakes routes (e. g. , monkeys from Old World) – North American mammal fauna enjoyed free interchange with NE Asia – Isthmus of Panama was emplaced in Pliocene (~3 to 3. 5 Ma), establishing a land corridor for interchange (and marine barrier between Atlantic and Pacific) – North American predators largely out-competed South American ones; South American marsupials invaded North America (opossum) Fossils & Evolution—Chapter 9 9

Fossils & Evolution—Chapter 9 Miocene (20 Ma) 10

Isthmus of Panama (~3. 2 Ma) Fossils & Evolution—Chapter 9 11

Barriers and provincialism • Paleozoic foram example Fossils & Evolution—Chapter 9 12

Mississippian forams New World endemics Old World endemics cosmopolitan Rheic Ocean (marine corridor) Fossils & Evolution—Chapter 9 source: Ron Blakey: http: //www 4. nau. edu/geology/ 13

Pennsylvanian forams New World endemics cosmopolitan Old World endemics Fossils & Evolution—Chapter 9 source: Ron Blakey: http: //www 4. nau. edu/geology/ 14

Fossils & Evolution—Chapter 9 15

Centers of dispersal • Idea that major taxa originate and undergo initial diversification in particular regions – Diversity of species declines away from center of dispersal • Tropical and subtropical regions seemingly have been centers of dispersal throughout much of the Phanerozoic – e. g. , dispersal of hermatypic reef corals Fossils & Evolution—Chapter 9 16

Generic diversity of hermatypic corals centers of dispersal 9 Fossils & Evolution—Chapter 17

Latitudinal diversity gradient • Tropics contain greatest number of species, with diversity declining in higher latitudes • Dt = Dt-1 + No – Ne, where No = number of originations and Ne = number of extinctions • So, is No greater in the tropics? Is Ne lower in the tropics? No lower in the high latitudes? Ne higher in the high latitudes? • Answer: higher Ne in high latitudes (at least for birds and mammals) Fossils & Evolution—Chapter 9 18

Island biogeography • “Island biogeography” is an important concept because there are lots of isolated habitats (real and virtual islands) – Lakes are islands surrounded by a sea of land – Mountain tops are islands surrounded by a sea of lower elevation – Patch reefs are islands surrounded by a sea of level bottom seafloor Fossils & Evolution—Chapter 9 19

Island biogeography • Species diversity increases as area of island increases S = c. Az, where S = diversity; c = constant; A = area; z = constant ranging from 0. 20 to 0. 35 Fossils & Evolution—Chapter 9 20

Species diversity vs. island area Fossils & Evolution—Chapter 9 21

Island biogeography • Why does species diversity increase with increasing area? – Probability of immigration is higher on larger islands – Less crowding on larger islands – Greater variety of habitats on larger islands Fossils & Evolution—Chapter 9 22

Island biogeography • Relict faunas = faunas whose geographic range is but a remnant of a previously much larger range • e. g. , Cold-adapted species that today are stranded on mountain tops – In Pleistocene ice age they were widespread – As climate warmed, species with poor dispersal mechanisms were left stranded in cold climates on mountain tops Fossils & Evolution—Chapter 9 23

Paleobiogeography • Modern day distribution of plants and animals is governed largely by climate and continental configurations • Distribution of fossil taxa on modern continents does not make sense except in light of continental drift and accreted terranes Fossils & Evolution—Chapter 9 24

Paleoiogeography (cont. ) • Wegener and other early proponents of continental drift cited fossil evidence for the existence of a Late Paleozoic–Early Mesozoic supercontinent (Pangaea) • Such evidence was largely discounted (even by G. G. Simpson) until 1960 s when overwhelming geophysical evidence “proved” sea-floor spreading Fossils & Evolution—Chapter 9 25

Fossil evidence for fusion of southern continents (Gondwanaland) Fossils & Evolution—Chapter 9 26

Lystrosaurus Fossils & Evolution—Chapter 9 27

Modes of dispersal • Recall Simpson’s modes of dispersal – Corridors, filters, sweepstakes routes • With acceptance of plate tectonics, two additional modes are now recognized: – Viking funeral ship = fossils rafted to a new land mass aboard a microcontinent or island arc – Noah’s Ark = living organisms rafted to a new land mass aboard a microcontinent or island arc Fossils & Evolution—Chapter 9 28

Viking funeral ship • Example: Late Paleozoic accreted terranes of western North America • Permian fusulinid faunal provinces were recognized in 1960 s, but their distribution on modern continents was difficult to explain prior to acceptance of plate tectonics • Now, exotic crustal belts in western North America are interpreted as accreted terranes – Permian sedimentary rocks and oceanic crust that were accreted to North America during early Mesozoic Fossils & Evolution—Chapter 9 29

Continental accretion Fossils & Evolution—Chapter 9 30

icrocontinents th Permian fossils Asian affinity Jurassic Fossils & Evolution—Chapter 9 31

western accreted terranes Fossils & Evolution—Chapter 9 32

Permian paleogeography Fossils & Evolution—Chapter 9 33

Plate tectonics and isolation of Australian marsupials • Plate tectonic isolation has allowed certain primitive animals to survive on Australia – Marsupials originated in North America – Migrated to South America in late Cretaceous – Then to Australia via Antarctica by Oligocene time • Convergent evolution between placental and marsupial mammals – Similar forms among animals adapted for similar life styles Fossils & Evolution—Chapter 9 34