Adaptive Radiations and Evolutionary Change on the Hawaiian Islands

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Adaptive Radiations and Evolutionary Change on
the Hawaiian Islands

• Presentation By Diana Roberts
• June 3, 2003

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Questions, Questions

• What are adaptive radiations and what criteria
  defines them?
• What role does evolution play in adaptive
  radiations and the rate at which they occur?
• What are some examples of adaptive radiations in
  Hawaiian birds, insects and plants?
• Why is adaptive radiation important to the
  speciation of animals?

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Adaptive Radiations

• Adaptive Radiation is the evolution of a single
  ancesteral species into several new species
  within a relatively short amount of time in a
  specific geographic area
• Adaptive Radiations describe the process by which
  a group adapts to a broad variety of situations,
  such as changed ecological environment, dispersal
  barrier and lack of competition or preditors

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Evolution

• Evolution is the process of change in the traits
  of organisms or their populations over time
• Evolutionary changes occur in populations as a
  result of genetic mutations that are passed to
  surviving generations or eliminated
• Natural selection can result in the formation of
  new species by promoting the species with the
  better advantage in the specific environment

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Speciation

• Allopatric Speciation Speciation that occurs
  when two populations that are geographically
  isolated from each other enough to diverge into
  different species
• Parapatric Speciation Speciation that occurs
  when two populations that live in adjacent,
  bordering territories with no barrier between
  them diverge far enough to form different species
• Sympatric Speciation Speciation that occurs when
  members of a single population, all living in the
  same environment diverge to form distinct species

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Criteria for Adaptive Radiation

• Reproductive Isolation
• Ecological Isolation
• Exploitation of ecological niches- high islands
  good place because populations can be seperated
  by physical features such as water
• Disharmony of Island fauna and flora
• Rapid Speciation- bursts of new species

• Pollination Relationships with surroundings
• Dispersal Barrier, likely to radiate at or near
  the limits of the range of dispersal
• Variation in feeding and mating rituals
• Wide range in habitat and growth form

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Hawaiian Islands
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Hawaiian Island Adaptors

• Hawaiian Honeycreepers
• Hawaiian Fruit Flies (Drosophilidae)

• Pelia
• Silverswords
• Cytrandia

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Hawaiian Honeycreepers - Drepenidiae
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Honeycreeper Radiation

• Occupy an array of foraging and dietary niches
  which correspond with the variety of bill
  morphologies, variety and natural variation
  allowed random mutations to succeed at a higher
  rate because of the openness of niches during
  first colonization
• Repeated inter-island colonization allowed
  allopatric differentiation, followed by sympatric
  reinforcement and ecological divergence because
  of the lack of competing species and a broad
  variety of ecological niches
• Thought to have adapted like the Galapagose
  Finches, most common ancestor is thought to be
  the Eurasian Rose finch

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IIWI

• Vestiaria coccinea
• Found in the ohia lehua forests
• Feed on the nectar of ohia lehau flowers and
  tubular blossoms

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APAPANE

• Himatione sanguinea
• Found in the ohia lehau forest
• Feeds primarily on nectar, also feed on insects

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AKOHEKOHE

• Palmeria dolei
• Feed mainly on nectar and seeds
• Found in the rainforests of Maui
• Endangered

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PALILA

• Loxioides balleui
• Found only on the dry forest slopes of Mauna Kea
• Endangered
• Feed mainly on seeds

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AKIAPOLAAU

• Himignathus munroi
• Found only on big island of Hawaii
• Endangered
• Woodpecker like in they eat insect larvae by
  chipping away bark, also effectively eats the
  nectar of lobeloids

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Hawaiian Fruit Flies-Drosophila

• 250 species of Drosophila are known, but numbers
  are expected to double
• 114 species of Scaotomyza on Hawaiian Islands,
  only 70 species are known on the rest of the
  world
• Isolation is thought to be the main cause of new
  species, preference to a particular host can
  isolate a species to where adaptive changes may
  occur

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Hawaiian Fruit Flies Cont

• Each species has individual preference for mating
  ceremonies and territories which involve factors
  of light, temperature, and humidity
• Differences in food sources-
• herbacous v. carniverous
• Body, wing size and shape

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Cyrtandra

• Has formed the most diverse species on the
  Hawaiian Islands
• 129 species on Oahu alone
• Most vary in leaf and flower morphology, also
  fruit

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• Cyrtandra hawaienses
• Cyrtandra platyphylla

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• Cyrtandra cordifola
• Cyrtandra calpidecarpa

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Geranium

• 50- 100 species known on Hawaiian Islands
• Occupy almost all of the habitats available to
  them
• Vary widely in leaf and bud morphology, also in
  growth form

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• Adaptive situations often cause plants to evolve
  the available pollinators, such as changing from
  insects to birds or vis versa

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Overview

• Adaptive radiations are the process by which
  plants, animals, and insects adapt to their
  surroundings in a way that they form new species
  in a relatively short period of time
• Some criteria for adaptive radiation to occur is
  a dispersal barrier, ecological isolation,
  biological isolation,etc.
• Evolution of the Hawaiian islands has influenced
  the radiation of the plants and animals over the
  years because the islands have been moving and
  changing ecologically, pathing the way for
  adaptive radiation to occur

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• Examples of adaptive radiations can be seen in
  many Hawaiian species such as the Honeycreepers,
  Fruit flies, and the growth forms of Cyrtandra
  and Geranium
• Adaptive radiation is important to the Hawaiian
  Islands and many island alike because it
  increases the diversity of the wildlife, but with
  recent invasion of tourism and foreign plants and
  animals, the available area to be exploited by
  nature is decreasing, in turn not allowing as
  much diversification to occur

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Bibliography

• Carlquest, Sherwin. Hawaii A Natural History.
  Honolulu SB Printers, Inc. 1980. Ch. 5.
• Carr, Dr. Gerald. U of Hawaii, Botany
  Department. http//www.botany.hawaii.edu
• Schulter, Dolph. The Ecology of Adaptive
  Radiation. Oxford U Press. Oxford, New York.
  2000.
• Bermingham, Eldredge Lovette, Irby J.
  Clade-specific Morphological Diversification and
  Adaptive Radiation in Hawaiian Songbirds. The
  Royal Society. 2001.
• U of Southwestern Adventist, Biology Department.
  http//biology.swau.edu