Fossils & Evolution—Chapter 91 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 92 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 93 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 94 North American biomes temperate deciduous forest coniferous forest temperate grassland rain forest cold desert hot desert tundra

Fossils & Evolution—Chapter 95 Terrestrial faunal realms

Fossils & Evolution—Chapter 96 Paleobiogeography Paleobiogeography is concerned with determining the geographic ranges of extinct taxa and geographic expansion from evolutionary centers of origin

Fossils & Evolution—Chapter 97 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 98 Bering Land Bridge (Paleogene through Wisconsin glacial stage)

Fossils & Evolution—Chapter 99 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 910 Miocene (20 Ma)

Fossils & Evolution—Chapter 911 Isthmus of Panama (~3.2 Ma)

Fossils & Evolution—Chapter 912 Barriers and provincialism Paleozoic foram example

Fossils & Evolution—Chapter 913 Mississippian forams source: Ron Blakey: cosmopolitan Old World endemics New World endemics Rheic Ocean (marine corridor)

Fossils & Evolution—Chapter 914 Pennsylvanian forams source: Ron Blakey: Old World endemics cosmopolitan New World endemics

Fossils & Evolution—Chapter 915

Fossils & Evolution—Chapter 916 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 917 Generic diversity of hermatypic corals centers of dispersal

Fossils & Evolution—Chapter 918 Latitudinal diversity gradient Tropics contain greatest number of species, with diversity declining in higher latitudes D t = D t-1 + N o – N e, where N o = number of originations and N e = number of extinctions So, is N o greater in the tropics? Is N e lower in the tropics? N o lower in the high latitudes? N e higher in the high latitudes? Answer: higher N e in high latitudes (at least for birds and mammals)

Fossils & Evolution—Chapter 919 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 920 Island biogeography Species diversity increases as area of island increases S = cA z, where S = diversity; c = constant; A = area; z = constant ranging from 0.20 to 0.35

Fossils & Evolution—Chapter 921 Species diversity vs. island area

Fossils & Evolution—Chapter 922 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 923 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 924 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 925 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 1960s when overwhelming geophysical evidence “proved” sea-floor spreading

Fossils & Evolution—Chapter 926 Fossil evidence for fusion of southern continents (Gondwanaland)

Fossils & Evolution—Chapter 927 Lystrosaurus

Fossils & Evolution—Chapter 928 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 929 Viking funeral ship Example: Late Paleozoic accreted terranes of western North America Permian fusulinid faunal provinces were recognized in 1960s, 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 930 Continental accretion

Fossils & Evolution—Chapter 931 Jurassic microcontinents with Permian fossils of Asian affinity

Fossils & Evolution—Chapter 932 western accreted terranes

Fossils & Evolution—Chapter 933 Permian paleogeography

Fossils & Evolution—Chapter 934 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 935 Eocene (~50 Ma) rifting of Australia from Antarctica

Fossils & Evolution—Chapter 936 Noah’s Ark? Isolated faunal realm

Fossils & Evolution—Chapter 937 Geographic phylogeny of marsupials