Hawaii Flashcards
Lec 23
Typical Island Chain Formation
subduction zone results in the upwelling of magma –> results in volcano formation, island formation over time
same at diverging regions of tectonic plate formation
Hot spot islands
islands formed by moving over a magma column
new islands forming, old islands eroding
Atoll Formation
After loss of volcanic activity: soil erosion no longer offset by new land added from volcanic activity
landmass will erode into marine environment
creates coral reef surrounding the island grows
(circle of corals and sediment around water where mountain used to be)
how did life travel to Hawaii
dispersal very uneven (no reptiles native)
Ocean dispersal
Ex: coconuts
Big storms
Aerial dispersal
Air drift, eventually
Avian dispersal
Stuck in or on birds
the jetstream goes right over Hawaii, trade winds transport seeds, insects, animals
Founder species
mostly from Asia
genetic analysis links extant species from Hawaii to extant species (adaptive radiation when they got to the island)
What abiotic and biotic factors contributed to diversity?
biotic factors: genetic drift, founder effect, population size
abiotic factors: climatic heterogeneity, open niches
Random genetic drift
small populations can change gradually over time, even when not under selection pressure, randomly!
if two population species are isolated (like on an island), randomly can result in 2 different species
Founder population + effect
new population colonizing an island = Founding population
contains only a sub-set of the genetics of the original population
Environment heterogeneity
diverse range of different climatic conditions
greater diversity of niches –> more species
rain shadow effect
Differences in island habitat
no apex predator
open biotic niches
lots of ducks + birds that adaptively radiated
Consequences of lack of large predators
more vulnerable to invaders
island animals don’t have defenses because they don’t need to protect themselves
vulnerable to pests as well as bigger animals, need biocontrol
disturbance cycles (lava)
volcanically active islands
nutrient availability in changes over the life of an island
lava flows destroys all existing flora + fauna
remains of lava is mineral rich
abiotic + biotic processes
first colonizers after lava flow
lichens, ferns, mosses
contribute to soil formation
plants begin to grow with new nutrients –> peak in middle –> nutrient supply exhausted, biomass begins to decline
