Biotic Environment and Biota of the Hawaiian Islands

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Biotic Environment and Biota of the Hawaiian
Islands

• Weather patterns in Hawaii have remained constant
  over past several 100 thousand years.
• Climate has changed as evidenced by many
  different factors that can be measured now.

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Glacial and Interglacial Periods

• Pleistocene was characterized by at least 4
  glacial periods occurring in very regular, cyclic
  patterns
• ? Nebraskan
• ? Kansas
• ? Illinoian
• ? Wisconsin

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Sea Level Fluctuations During Glacial Periods
From Stearns 1978
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What Did the Ocean Levels Do?

• Glacial ocean levels dropped below current sea
  levels
• 400 feet during major glaciations
• 340 feet during the Malama Low
• Interglacial ocean levels rose during periods
• 95 feet during Kaena period
• 25 feet during Waimanalo period

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Sea wall notch
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25 Ma
20 Ma
PH
Ku
PH
La
Li
15 Ma
10 Ma
Ma
Li
G
La
Ma
LP
G
Ne
5 Ma
Present
Ni
G
Ka
Oa
LP
MN
Ne
Ni
Ha
Ka
From Price Clague 2002
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Evidence Suggests Climate on Oahu was very
different during glacial and interglacial periods.

• Rainfall about double present during glacial
  periods
• Rainfall far less than present during
  interglacial periods

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Factors InvolvedKoolau Mtns. Were Probably
Much Higher in the Past Than at Present

• Probably were over 4000 feet elevation (now
  between 2500 and 3000 feet)
• Erosion and subsidence brought mountains down to
  current height.

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Inversion Layer

• Height of Inversion Layer is Dependant upon Air
  Temperatures

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Glacial Periods Inversion Layer Much Lower Than
Present

• Air and ocean temperatures cooler than present
• Moist air is trapped at lower elevation for
  increased orographic affect
• Higher precipitation occurs at lower elevation

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Interglacial Period Inversion Layer Was Much
Higher Than Present

• Air temperatures were warmer pushing inversion
  higher
• Moist air was not trapped in orographic affect
• Less precipitation occurred at lower elevations

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Glaciation Events in Hawaii

• Island of Hawaii is the only tropical mid-pacific
  island to have evidence of glaciation
• Evidence of four glacial drift sheets observed on
  Mauna Kea beginning about 280,000 years ago
• Periglacial (near glacial) features observed on
  Haleakala
• Estimated there was a several degree drop in
  temperature during glacial periods
• No increase in precipitation likely occurred

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Botanical Evidence To Climatic Changes

• Pollen Cores
• Pollen grains are microscopic spores of flowering
  plants
• Morphologically variable
• Hard outer coat that preserves well
• Pollen is either wind borne or insect transmitted
• If falls into a boggy environment will preserve
  as a permanent record of plant in vicinity

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Examples of Pollen Grains
Artemisia nova
Pinus echinata
Agropyron sp.
Acacia sp.
Eucalyptus sp.
Hibiscus sp.
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Steps to Recovering Pollen

• Shove core sampler into the soil to a specific
  depth
• Recover the soil sample
• Spread a thin layer on microscope slide
• Identify species on basis of pollen morphology
• Compare to current ecology of species
• Deeper recovered pollen is from longer ago

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Hawaiian Bog Study

• High elevation bogs sampled in several locations
• Elevation of bogs 4000 - 5000 feet

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Alakai Swamp, Kauai
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Alakai Swamp, Kauai
Three (3) distinct zones identified

• ZONE 1
• Finding
• Dominated by xerophytic sub-alpine species
• Rainforest species geographically restricted
• Interpretation
• Mid-glaciation period
• Inversion layer is depressed to low elev.

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Alakai Swamp, Kauai
Three (3) distinct zones identified

• ZONE 2
• Finding
• Dominant Rainforest Vegetation
• Interpretation
• Interglaciation period
• Inversion layer at high elevation
• High rainfall to upper mountain elevation

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Alakai Swamp, Kauai
Three (3) distinct zones identified

• ZONE 3
• Finding
• Vegetation similar to what is extant today
• Interpretation
• Flora was at its present composition

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Fossils in Hawaii?

• Fossils found in
• Salt Lake Tuft dated to
• ca. 350,000 years ago

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Does anybody recognize this leaf part?
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Does this section of a leaf help? Pritch
ardia sp Loulu palm
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15 different plant species all rainforest sp.
koa ohia lehua
Ann. ppt now 500 mm Ann. ppt then 1000-1750 mm
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Big Island Fossils from Kilauea
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Mostly fern impressions
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Foreign Top Soil

• Wahiawa top soil in Kunia Rd. vicinity
• Tropospheric dust from continental Asia
• Adds about 1 mm per 1000 years
• Now about 200 mm deep
• Accumulating for at least 200,000 years
• Evidence of a relatively consistent environment
  despite fluctuations in ppt.

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How Did Plants and Animals Come to Hawaii?

• Hawaiian Islands are 2000 miles from nearest land
  source
• No natural land bridges or islands to hop
• Organisms that arrived here are pre-adapted to
  long distance dispersal
• Not necessarily for 1000s of miles

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Disharmonic Flora and Fauna

• Not all continental representatives are present
  in Hawaii
• As such, our flora and fauna do not reflect those
  of the continents from which they were derived

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Examples of Disharmony

• Only two native species of mammal
• Only one is terrestrial (hoary bat)
• Terrestrial land snails dominate forests instead
  of insects
• Plant groups common on continents are absent or
  nearly so
• Terrestrial birds had only a few colonists

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Do We Know Absolutely How They Got Here?

• NO! All evidence is circumstantial. However by
  understanding a species biology it is often
  evident

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What Means Did Plants and Animals Have to Get
Here?

• Swimming or floating in ocean
• Rafting on debris in ocean
• Floating or flying through the air
• Hitchhiking along with something else that comes
  here

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But What Are The Chances That a Species Could Get
Here That Way?

• Very Slim!
• However, given enough time and random events the
  likelihood of successful colonization increases

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Hawaii Contradicts Some Tenants of Island
Biogeography

• 1. Flora and Fauna will reflect continental
  source
• No, they are disharmonic
• Derivation of flora and fauna from all over
• 2. Large islands will have greater diversity
  than small islands
• No, Kauai has greater diversity than does
  Hawaii
• Age distribution of island responsible

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Specific Examples of ColonizationsTerrestrial
Birds

• Only 15 colonists radiated to ca. 80 species
• Land birds typically do not roam much
• These few probably were lost in storms and ended
  up here

Nihoa Finch
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Specific Examples of ColonizationsLand Mollusks
(snails)

• 20 colonists radiated to over 1000 species
• Probably by hitchhiking on birds

Achatinella sowerbyana
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Specific Examples of ColonizationsInsects

• ca. 250 colonists have radiated to over 4000
  species
• Most of these probably arrived via air streams
• Adult
• Pregnant female
• Egg sac
• Some also arrived via rafting

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Specific Examples of Colonizations
Mammals

• Two mammals have made colonized the Hawaiian
  islands
• Only one is a terrestrial mammal - the Hoary Bat

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Specific Examples of Colonizations
Ferns

• Spores are easily wind blown
• Lower level of endemism than in flowering plants

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Specific Examples of ColonizationsFlowering
Plants

• Estimated to have been about 270 colonists
• These have radiated to over 1000 species
• Some radiations large with many species
• Some radiations with only a few species
• Some species have not radiated at all
• Plants have arrived by sea, air, or transported
  by birds

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Estimated that 22 Arrived via Floating
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About 3 Arrived by Air
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And About 75 Arrived Transported by Birds

• By Sticky Attachment

• By Barbs or Hooks

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• In Mud Attached to Bird

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Ingested by Birds