10/29/2013

1

EVOLUTIONBiology 145

Lecture 13 – Speciation

FOUNDER EFFECT

In a population with AA, Aa, and aa individuals, if ONE founds a subpopulation, it might well be a HOMOZYGOTE

Polydactyly –AmishAllele 1:14 versus 1:1000

General: 1:180,000PA Mennonites 1:176

Maple Syrup Urine Disease

10/29/2013

2

Genetic BOTTLENECKS

10/29/2013

3

SPECIATION

Gene flow must be interrupted!.

Anagenesis versus cladogenesis (speciation)

Chronospecies

Anageneticchange

10/29/2013

4

Allopatric speciation

Gene flow interrupted by a physical barrier

10/29/2013

5

Sciurus aberti aberti Sciurus aberti kaibabensis

Parapatric Speciation

Agrostis

10/29/2013

6

Sympatric speciation

10/29/2013

7

RIMS   Reproductive Isolating Mechanisms

RIMS – pleiotropy

Food type

Song

10/29/2013

8

Ring species