BIOL 1020U Lecture Notes - Lecture 22: Peripatric Speciation, Allopatric Speciation, Sympatric Speciation
Species and Speciation Lecture
Chapter 22 (Part 2) (pp. 450-459)
Speciation
•How do two populations become reproductively isolated from each other?
Overtime – random mutations – genetic divergence
Many genetic differences accumulate (genetic drift, natural selection) inability
to interbreed
•What is speciation?
•2 groups of organisms becoming reproductively isolated from other
•During the process of speciation can interbreeding occur?
Yes, if the populations have not diverged enough genetically
Partially reproductively isolated populations – not yet separate species – hybrid
offspring have reduced fertility or viability
Modes of Speciation
Allopatric vs. Sympatric Speciation
Allopatric speciation characteristics:
-Requires genetic isolation between diverging populations
-Easiest way for this to happen is via geography
-Allopatric speciation begins with formation of allopatric populations –
geographical separation – long periods of time genetic divergence –
subspecies
Example of speciation in action: Salamander (Ensatina spp.) Speciation in
California Video
Notes on video: same species look similar but behave differently,
based on their adaptation to their environments – species that
produced offspring on their way to becoming 2 different species
based on their adaptation
Allopatric Speciation:
Two ways populations become allopatric:
1. Dispersal – where individuals colonize a distant place, such as an island
2. Vicariance – where a geographic barrier arises within a population
Regardless of mode by which populations become allopatric, end result is 2
separate populations that will diverge genetically until speciation’s occurs
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•Dispersal – Peripatric Speciation (a type of allopatric speciation)
•Characterized by:
-important in peripatric speciation
-dispersal from mainland population to new, remote location
-may be accidental or intentional (migration)
-2 populations than evolve separately
•Result: distant, isolated, “island population”
•What is meant by “island population”?
Often small and in an environment that is slightly different from mainland
population – may be habitat patch; need not be true island
•Why do changes accumulate faster in “island population”?
Genetic drift is more pronounced in smaller populations – population faces
new selective pressures in new environment
•Example: New Guinea
kingfishers:
•Dispersal – Adaptive Radiation (also still allopatric)
• Example: Adaptive radiation - Darwin’s finches – natural selection greatly
accelerates both speciation and adaptation – started off as off-shoot, but produced
multiple different species (15 different species, adapted to foods available on the
island)
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Document Summary
Yes, if the populations have not diverged enough genetically. Partially reproductively isolated populations not yet separate species hybrid offspring have reduced fertility or viability. Easiest way for this to happen is via geography. Allopatric speciation begins with formation of allopatric populations geographical separation long periods of time genetic divergence subspecies. Example of speciation in action: salamander (ensatina spp. ) Notes on video: same species look similar but behave differently, based on their adaptation to their environments species that produced offspring on their way to becoming 2 different species based on their adaptation. Two ways populations become allopatric: dispersal where individuals colonize a distant place, such as an island, vicariance where a geographic barrier arises within a population. Regardless of mode by which populations become allopatric, end result is 2 separate populations that will diverge genetically until speciation"s occurs. Page | 1: dispersal peripatric speciation (a type of allopatric speciation, characterized by: Dispersal from mainland population to new, remote location.
