FOUR LIMITS TO ADAPTATION

1
SUMMARY OF LAST TIME
Biologists have no agreed definition of the term
species Morphological Reproductive Species
Concepts both have multiple problems No surprise
to Darwin if organisms are evolving, a species
is merely a human term
2
LECTURE 13 RIMs
Reproductive Isolating Mechanisms
3
TWO FLAWED SPECIES CONCEPTS
Morphological Species Concept Conspecifics
look alike Reproductive Species Concept
Only conspecifics interbreed
4
A COMMON THEME GENE FLOW
Not definitions, but comments
Morphological Species Concept two
populations can only diverge genetically if
little gene flow Biological Species Concept
low hybridization means little gene flow

5
RIMs
Reproductive Isolating Mechanisms - central
to Reproductive Species Concept Anything
preventing gene flow between species, except
geography
6
RIMs
Name should be changed but new one not agreed
Factors preventing gene flow between populations,
except geography
7
THINGS PREVENTING GENE FLOW
EXTRINSIC Geography INTRINSIC
Pre-zygotic RIM
Post-zygotic RIM
8
GEOGRAPHY
Reduces gene flow by distance
9
GEOGRAPHIC ISOLATION
TEAL

North America
Eurasia
10
PRE-ZYGOTIC RIMs
Reduce gene flow by preventing hybrids from
being formed
11
ECOLOGICAL RIM
RED CAMPION WHITE CAMPION
FOREST GRASSLAND
12
Fertile hybrid
13
ECOLOGICAL RIM
CONIFER GREEN
LACEWING LACEWING
14
SEASONAL RIM
Conifer Lacewing Green Lacewing
15
BEHAVIOURAL RIM (a) Own behaviour, including song
16
BEHAVIOURAL RIM (b) Pollinator behaviour
Creeping Thistle Spear Thistle
17
Red-tailed White-tailed
BUMBLE BEES
Creeping Thistle Spear Thistle
18
MECHANICAL RIM
Spider copulation
19
MECHANICAL RIM
r
F epigyne
M

pedipalp
20
MECHANICAL RIM
EPIGYNE
PEDIPALP

21
CHEMICAL RIM
Pollen grain
ovules
Pollen Tube
22
THALE CRESS ECOTYPES
Single-stem
Multi-stems
23
THALE CRESS ECOTYPES
Pollen tubes of another ecotype grow randomly
24
POST-ZYGOTIC RIMs
Gene flow reduced by selection against hybrids
25
HYBRIDS ARE FREQUENT
Mallard Gadwall
26
HYBRIDS ARE FREQUENT
27
HYBRIDS ARE FREQUENT

Gelada Hamadryas
28
HYBRID INVIABILITY
Wood Frog Leopard Frog
29
Wood Frog Leopard Frog
FOREST GRASSLAND
Quiet clucks Loud snore
30
WHOOPS!

Wood Frog with dying hybrid brood
31
HYBRID STERILITY
Mum Dad Horse Ass
Mule
32
HYBRID BREAKDOWN
Thai Rice
Japanese Rice

Grandchild