Mammalogy Unit 1 - Biogeography

Biogeography

The study of causal processes and current distribution of species

Which of these factors do NOT determine the range of a species?

Geologic layers

Endemism

Restriction of a species range

Disjunction

A gap in the range of related species

How many faunal regions are there?

7

Paleartic

Largest Faunal region, Northern Old World (Europe, Asia, Northern Africa and the Middle East). 42 Families, 0 Endemic (Neartic + Paleartic + Holartic)

Neartic

Similar Biomes to Paleartic (North America, Canada, Greenland), 37 families, 2 endemic

Neotropical

Rainforests, Savanna, and Tropical Scrubland (South America), 50 families, 19 endemic. Historically isolated and better climate

Ethiopian

Sahara Desert, Savanna, Scrubland, Tropical Island (Africa, Madagascar) Shares 70% of families with Oriental. 52 families, 18 endemic

Oriental

Consistent climate of Tropical rainforest (India, Middle east, Maylasia) 50 families, 5 endemic. Not isolated

Australian

28 families, 17 endemic. Most isolated for longest time

Oceanic

Includes remote islands, Few native mammals on islands.

Historical Biogeography

Study of changes in species ranges that have taken place over evolutionary time

Evolutionary processes

Speciation, Extinction, Dispersal

Geological processes

Continental drift, climate change

Vicariance

The geographical separation of a population, typically by a physical barrier such as a mountain range or river, resulting in a pair of closely related species.

Continental Drift

Movement of land masses over geologic time

Supercontinent Pangea

Where first synapsids emerged

Laurasia

North America, Europe, Greenland, part of Asia

Gondwanaland

Southern continents (South America, Australia, Africa, Antarctica, parts of Asia)

When was the last glacial maximum?

~20,000 years ago

Refugia

Preserve biodiversity during periods of environmental change

Species Dispersal

Extension of species range, not necessarily over a single lifetime

Passive Dispersal

Not under the control of the animal, Human involvement or rafting

Active Dispersal

Under the control of the animal, Accumulation of ecological dispersal events

Corridor routes

Path of least resistance

Filter routes

Adapted species expand distribution, Bering land Bridge (cold), Panamanian land bridge (warm)

Sweepstakes routes

Most restrictive pathway: Rafting, Hurricanes

Ecological Biogeography focuses on…

How species ranges are influenced by certain factors

Species Richness

The number of species in an area

Insular Gigantism

Smaller mammals on islands tend to be larger than close relatives or ancestors on mainland

Insular dwarfism

Large mammals on islands tend to be smaller than close relatives or ancestors on mainland

Bergmann’s Rule

Body sizes of mammals tend to increase with increasing latitude (Bergmann Body size “BB”)

Large mammals have lower surface to volume raitios

True

Allen’s Rule

Mammals in colder climates have shorter appendages, mammals in warmer climates have longer appendages (Allen Appendages “AA”)

Gloger’s Rule

Pelage and Humidity- Polar bears in the arctic and Grizzlies in the humid tundra/boreal habitats

Rapoport’s rule

Species range increases from equator to poles, increasing climate variability at the poles (Polar species adapt to broader range of environments than tropical) (Rapoport Range “RR”)

Latitudinal gradient

Species diversity decreases from the equator towards the poles

Elevational & Peninsular gradient

The number of species declines towards the terminal end of a peninsula