Biogeography Exam 2

Small populations

founder effects, drift, inbreeding

founder effect

colonists carry subset of mainland diversity

Inbreeding

Lower fitness (inbreeding depression)

ecological release

niche expansion, high densities

generalists win over specialists

broader diets and habitat flexibility

small islands

fewer coexisting niche competitors

over generations we see…

less dispersal capacity favored

evolution works faster on…

islands rather than the mainland

plant diaspores

achene increase, pappus decrease

time scale

few generations on small islets

tendency (the island rule)

small vertebrates —> larger; large —> dwarfs

drivers (the island rule)

resource limits, enemy release, stability

examples (the island rule)

komodo (giant varanids); pygmy elephants

caveat (the island rule)

mixed empirical support across taxa

hotspot chain (Hawaii)

age gradient NW(old) —> SE (young)

each island (hawaii)

stages: emergence —> growth —> erosion

high relief (Hawaii)

“islands within islands” mountain isolates

result (Hawaii)

extreme endemism & repeated isolations

plants (Hawaii)

mostly bird-borne (zoochory), wind, sea minority

insects (hawaii)

overwhelmingly airborne to reach the island

vertebrates (hawaii)

bats (native), many groups absent initially

humans later added what to Hawaii?…

Ants. and other invaders —> reshaped the biota of the island

wind-dispersed dispersal

tiny seeds ride air currents

Zoochory dispersal

animals eat seeds and poop it somewhere else

Phoresy (dispersal)

small animals (ectoparasites) move through other animals

By sea dispersal

buoyant seeds float on currents to new shorelines

Rafting dispersal

whole organisms raft on something after a storm/flood to new place

passive airborne dispersal

animals picked up and carried by wind

active airborne

animals fly themselves to islands

sequential islands

stepwise isolation and opportunities

topographic diversity

microhabitats and climate zones

strong selection + small Ne = …

fast divergence

ETIB = Equilibrium Theory of Island Biogeography

that the number of species on an island is a dynamic balance between immigration and extinction. This equilibrium is determined by two key factors: the island's size (larger islands have lower extinction rates) and its distance from the mainland (closer islands have higher immigration rates).

Immigration Curve (I) (ETIB)

fast at first, steep drop as “easy” colonists arrive, isolation matters. bigger islands present a bigger target

Extinction Curve (E)

rises with species, area matters (larger islands = larger N). Immigration to near islands lowers effective E

Species-Area Relationship (SAR)

habitat diversity increases, pop size increases, sampling increases

Habitat “Islands” Predictions

larger/less isolated fragments sustain higher S

single large —> SLOSS (Single Large Or Several Small)

lower E, more interior habitat, supports area-demanding taxa

several small —> SLOSS (Single Large Or Several Small)

capture beta-diversity, insure against local catastrophes

SLOSS answer…

context-specific —> consider heterogeneity, covariance of risks, target taxa

ETIB to GEIB (Generalized/Integrative)

blend area, isolation, heterogeneity, traits, interactions, evolution

land

clear regions, strong barriers (ocean, mountains, deserts, etc.)

sea

high-density medium, fully pelagic lifestyles common

pelagic (water column)

dynamic, circulation-driven

benthic (seafloor)

substrate/depth-driven, higher local endemism

continental shelf (ocean architecture)

(to ~200m) —> shelf break —> slope —> rise

abyssal plain (ocean architecture)

(3,500-6,000m) most extensive environment

trenches (ocean architecture)

(~11,000m) hadal

euphotic zone (zonation)

photosynthesis possible, upper few tens of m

epipelagic zone (zonation)

wind-mixed; ~tens of m to ~200m

Pycnocline zone (zonation)

most important boundary

what is the most important/distinguishing factor in the ocean?

the pressure, light, and temperature

upwelling

tiny area, huge fishery yield

great ocean basins

major biogeographic units

ocean basins

primary biogeographic backdrop

case hook

mid-latitude peak in planktonic foraminifera tied to pycnocline structure

Longhurst biomes…

polar, westerly winds, and trade winds biomes (33 different provinces in the biomes)

spalding realms…

coherent higher-taxon histories; high endemism

spalding biomes

group provinces with shared ocean processes biomes

spalding provinces

large epipelagic areas with stable/recurrent drivers

Range Extension (Diffusion)

Devonian “Greening”

vascular plants/first trees expand, because of this there is a long-term cooling and “ice-house” tendencies set up

Carboniferous Coal Forests

350-300million yrs ago, ever-wet equatorial rainforests: massive peat/coal formation

Permian Worldbuilding

300-250million yrs ago, regional floras (Angaran, cathaysian, euramerican, gondwanan) Late Permian collisions → Pangaea

Jurassic-Early Cretaceous Flora Belts

200-150million yrs, equatorial summer-wet tropics, subtropical deserts, winter-wet belts, warm/cool temperate zone.

High-latitude Warmth

Late Jurassic to Early Cretaceous (~160-110 Ma)

Angiosperms & Foraging Heights

Early cretaceous (~125-100mil yrs) High browse (palms/conifers/angiosperms)

Asteroid Impact

K/Pg, Yucatán the asteroid impact killed all the dinosaurs 66 million yrs ago. Lots of ejecta, soot, and sunlight reduction/ozone loss/acid rain.

“Age of the mammals”

65mya to present, mammals diversified greatly. Professor thinks this is biased naming cause we are mammals, lots of animals diversified at this time

PETM

rapid carbon release, strong global warming (56 mya) ocean acidification, biogeographic turnover

regionalization

the process of dividing the world into areas that share distinctive species and evolutionary histories

regionalization inputs

species composition & range data; endemism and turnover patterns; environmental and barrier context

Quantifying Regions Inputs (clustering)

species range maps by grid cell

Quantifying regions outputs (clustering)

regions + subregions that are testable and comparable