Topic 4 - Biogeography

Biogeography

study of distribution of species and ecosystems over geographic space and geologic time

Species range

geographic distribution for all individuals in a species

Ecological biogeography

• looks at current distribution of species

• explains distribution in terms of interactions at community level btwn organisms and environment

Historical biogeography

looks at changes in species range over evolutionary time

Endemism

restriction of species range to specific area

Disjunct distribution

two or more groups of related animals widely separated geographically

Biotic factors

living factors

Abiotic factors

non-living factors

Faunal Regions (Ecozones)

largest biogeographical division of Earth’s surface based on distribution of species

How many faunal regions are there? What determines a faunal region?

8; distinct due to factors like climate and topography that reduce gene flow in/out of that region

Palearctic

• Europe, North Africa (to Sahara), Asia (except India, Pakistan, & Southeast Asia), & Middle East

• largest terrestrial faunal region

• 42 mammalian familes

• no endemic families

Nearctic

• North America & Greenland

• 37 families

• 2 definitely endemic; possible 2 more endemic

Holarctic

Palearctic + Neaarctic

Neotropical

• South America, Central America, Antilles, & south Florida

• 50 families

• 19 endemic

Afrotropic (Ethiopian)

• Madagascar, sub-Saharan Africa, & southern half of Arabian peninsula

• 52 families

• 18 endemic

Indomalaya (Oriental)

• Pakistan, India, Southeast Asia, Philippines, & Indonesia west of wallace line

• 50 families

• 4 endemic

Wallace line

• boundary separating Indomalaya from Australasia

• active region of plate tectonics

Mammal distribution west of wallace line? east of wallace line?

West: placental mammals (Indomalaya)

East: marsupial mammals (australasia)

Wallacea

portion of australasia that borders wallace line

Australasia

• Australia, Tasmania, New Guinea, & Indonesian islands east of wallace line

• 28 families

• 17 endemic

Oceanic

• oceans & small, isolated, oceanic islands

• 14 families

• 100% endemic

Antarctic

• Antarctica

• no mammal families

  • all mammals found there are in transit or using it temporarily for breeding

What do biomes differ in?

soil makeup, precipitation, and plant types

Deserts

• less than 1cm annual rainfall

• roughly 30° latitude north and south

• many due to location in rain shadow of mountain range

• species evolved to prevent moisture loss

Dry Shrublands & Dry Woodlands

• in western/southern coastal regions between latitudes 30° & 40°

• semiarid lands (more rainfall than deserts)

  • long, hot, dry summers

  • most rainfall in winter

• plants have evergreen leaves

Dry Shrublands

• less than 25-60cm annual rainfall

• chaparrals

• fire controlled communities

• not enough rain for trees

Dry Woodlands

• receive 40-100cm annual rainfall

• have trees, but do not form dense, continuous canopy

Grasslands

• warm during summer & cold during winter

• 25-100cm of rainfall

• dominant animal: grazers & burrowers

Evergreen Broadleaf Forests

• tall trees forming continuous canopy

• lat 20° north & south

• rainfall excess of 200cm a year

Tropical rainforests

• type of evergreen broadleaf forest

• lots of rain, temps above 25°C, and average humidity of 80%

Deciduous Broadleaf Forests

• temperate latitudes

• rainfall not constant all year round

• two types: tropical & temperate

Tropical Deciduous Broadleaf Forests

drop leaves during dry season

Temperate Deciduous Broadleaf Forests

less rainfall annually & colder winters than tropical; soil holds nutrients

Coniferous Forests

• low rainfall & stressful winters

• above and below deciduous broadleaf forests

• boreal forests: found in regions having glaciers, cold lakes, and steams

  • rain mostly in summer with low evaporation

• montane forests (mountainside)

• temperate rainforests: receive lots of coastal rain

• southern pine forests: costal plains of south atlantic/gulf states

  • adapted to dry, sandy, nutrient poor soils

Arctic Tundras

• treeless plains located btwn polar caps and boreal forests

• very low temps, short growing season, low rainfall

Alpine Tundras

similar biome to arctic tundras but at elevations above tree line

Who proposed the idea of continental drift?

Alfred Wegner

Pangea

supercontinent during permian period

Break up of Pangea: first phase

during cretaceous split into Laurasia & Gondwana

Laurasia

• northern continent

• contains northern hemisphere continents

Gondwana

• southern continent

• contains southern hemisphere continents

Break up of Pangea: phase two & three

• Laurasia & Gondwana break up around 60 to 55 mya

• Laurasia: North America & Iceland broke free of Europe

• Gondwana: Africa broke free of South America & Antarctica

Quaternary or Pleistocene Ice Age

• began during last third of Cenozoic era: Quaternary period

• long term reduction in temp resulting in expansion of continental and polar ice sheets

Interglacial Period vs. Glacial Period

Interglacial: period of relative warmth during ice age

Glacial: period of relative cold during ice age

How did glacial periods affect mammalian distribution?

• expansion of ice sheets: caused groups to become separate increasing speciation

• sea levels dropped exposing land bridges: increased dispersal

Beringea

• Bering land bridge

• allowed for high levels of species dispersal btwn North America & Europe

Great American Interchange

Panama Isthmus appeared connecting North & South America; allowed for faunal exchange

How did interglacial periods affect mammalian distribution?

• sea levels rise: inc isolation

  • allows for inc dispersal of warm climate species closer to poles

Where are the oldest true marsupial fossils found?

North America; Peradectes minor

How did metatherians distribute?

1. crossed into South America before Gondwana fragmented

2. ancestors of Australidelphia migrated from South America to Australia

Sparasodonta

• 2nd group of metatherians that flourished in South America prior to migrating to Australia

• only mammalian predators at the time

What two geological events caused the Great American Interchange?

• volcanic activity causing rise of Panama Isthmus

• decreasing sea levels because of expanding glacial sheets

Which continental invader were more successful? Why?

• North American invaders

  • climate more amicable for southward migrants

  • NA was still in partial contact with Eurasia which allowed for more gene flow

    • gave NA a better competitive advantage