Lecture 6- Species and their formation 3 Flashcards
What is an evolutionary radiation?
The proliferation of a large number of daughter species from a single ancestor
When is an evolutionary radiation said to be adaptive?
When the evolutionary radiation results in an array of species living in a variety of environments and differ in characteristics to exploit that environment
When is an evolutionary radiation said to be nonadaptive?
When the radiation is not accompanied by any observed ecological differentiation among species
When does an adaptive radiation begin?
Genetic differentiation between populations evolves in response to differences in the environments they inhabit and resources they use
When is genetic differentiation more likely to occur?
Environments with abundant resources
When is a population likely to encounter underutilized resources?
When it colonizes a new environment containing relatively few species
Give some examples of adaptive radiations on the Hawaiian Islands.
1000 species of flowering plants
10,000 species of insect
1000 land snails
100 bird species
How many species did the 10,000 known species of insect on the Hawaiin island evolve from? What about the 100 bird species
400 immigrant species of insect
7 immigrant species of bird
How many of the 1000 plant species on the Hawaiian islands are endemic?
more than 90%
What does endemic mean?
They are found nowhere else
What do some flower species on the islands show that their mainland relatives do not?
Wider variety of habitat and life histories
How many species are there of Hawaiian sunflowers?
28
What are the Hawaaiian sunflowers called?
Silverswords
To what genera do these silverswords belong?
Argyroxiphium
Dubautia
Wilkesia
What does DNA sequences of the Hawaiian silverswords show?
They have a recent common ancestor with a species of Tarweed from the Pacific coast of North America
What are the features of mainland tarweed?
Small, upright herbs (nonwoody plants)
What are the features of Hawaaiian silverswords?
Prostrate and upright herbs, shrubs, trees, and vines
Despite their morphological diversification, silverswords are…
Genetically similar
Why are silverswords more diverse than their mainland counterparts?
Original colonizers arrived when there were very few plant species- few trees and shrubs
Why did mainland tarweed not become a tree or shrub?
Ecological communities contained trees and shrubs
Opportunities to exploit tree way of life had been preempted
Where else has adaptive radiation occured?
Ice plants, mostly endemic to South Africa
1563 species radiated in that region in the last 9 million years
What are ice plants?
Succulents, who utilize crasulacean acid metabolism
