Transcript Adaptive Radiations on Islands, and Evolutionary Change

Adaptive Radiations and Evolutionary
Change on the Hawaiian Islands
Presentation By Diana Roberts
June 3, 2003
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?
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
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
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
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
Hawaiian Islands
Hawaiian Island Adaptors
• Hawaiian
Honeycreepers
• Hawaiian Fruit
Flies
(Drosophilidae)
• Pelia
• Silverswords
• Cytrandia
Hawaiian Honeycreepers - Drepenidiae
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
I’IWI
• Vestiaria coccinea
• Found in the ‘ohi’a
lehua forests
• Feed on the nectar of
‘ohi’a lehau flowers
and tubular
blossoms
‘APAPANE
• Himatione sanguinea
• Found in the ‘ohi’a
lehau forest
• Feeds primarily on
nectar, also feed on
insects
‘AKOHEKOHE
• Palmeria dolei
• Feed mainly on
nectar and seeds
• Found in the
rainforests of Maui
• Endangered
PALILA
• Loxioides balleui
• Found only on the
dry forest slopes of
Mauna Kea
• Endangered
• Feed mainly on
seeds
‘AKIAPOLA’AU
• 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
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
Hawaiian Fruit Flies Con’t
• Each species has individual preference for
mating ceremonies and territories which
involve factors of light, temperature, and
humidity
• Differences in food sourcesherbacous v. carniverous
• Body, wing size and shape
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
• Cyrtandra hawaienses
• Cyrtandra platyphylla
• Cyrtandra cordifola
• Cyrtandra calpidecarpa
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
• Adaptive situations
often cause plants to
evolve the available
pollinators, such as
changing from insects to
birds or vis versa
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
• 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
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