SpeciationDrift Drift is important in evolution Just because an allele is common doesnt mean selection favored it Speciation via drift Probably not Flies in allopatry same environment never ID: 269346
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Slide1
Allopatric Speciation—Drift
Drift is important in evolutionJust because an allele is common doesn’t mean selection favored itSlide2
Speciation via drift?Probably not.
Flies in
allopatry
, same environment never
RIMDrift may facilitate speciation, but probably cannot often cause speciation on its ownSlide3
Ecological Speciation
Sister species in the same lakeBig is benthic, small is
limnetic
No interbreeding in nature– habitat isolation or pre-mating RIM?Slide4
Low probability of spawning between different
ecomorphs
, even when closely related (A).
Ecology is important in RIM.
C = control (same species, same population, high probability of spawning)
D = same ecotype, distantly related (act like same species)
A = sympatric, closely related, different ecotype (act like different Biological species)
B =
allopatric
, distantly related, different ecotype
Reproductive compatibility determined more by ecotype than by genetic relatedness
No-choice mating trials in the labSlide5
RIM appears to be body size—did divergent natural selection on body size
speciation?Slide6
Speciation via Sexual Selection
Many sister lineages with same ecological niche, but different secondary sexual charactersSlide7
Greater species diversity in lineages with greater promiscuity. Due to stronger sexual selection?Slide8
Fig. 24-12
EXPERIMENT
Normal light
Monochromatic
orange light
P.
pundamilia
P. nyererei
Speciation by Sexual Selection
Under manipulated lighting, females made “wrong” mate choiceSlide9
Genetics and Timing of SpeciationSlide10
Time to Speciation
VariesSlide11
Fig. 24-19
One-gene speciationSlide12
RIM’s
can be generated by simple differences in geneticsSlide13
Ancestral species:
Triticum
monococcum
(2
n =
14)
AA
BB
Wild
Triticum
(2
n =
14)
Product:
AA BB DD
T. aestivum
(bread wheat)
(2
n =
42)
Wild
T. tauschii
(2
n =
14)
DD
Speciation may involve hybridization, so it can be quick for many speciesSlide14
Speciation involves a stochastic element…
Medium ground finches on Daphne major (
Gallapagos
Island)Slide15
Top to bottom: A to F show successive generations of the hybrids, which now mate only with each other.
Grant and Grant, PNAS, doi/10.1073/pnas.0911761106
Immigrant
F1
F5
F6
Immigrant
Geospiza
fortis
:
large body,
wide
beak,
unusual song (bad mimicry)Slide16
The Grants followed the fate of the immigrant over 7 generations (28 years)
The immigrant imitated (imperfectly) the local song and mated with a large femaleIn generation 4, severe drought, lineage reduced to a single brother and sister, which mated
From then on, this lineage was reproductively isolated—
premating
RIMRIM due to song culturally transmitted to sons (learned)?
sound may also be a consequence of bill shape