1. DARWIN’S FINCHES
© 2016 Paul Billiet ODWS

2. Adaptive radiation
A single species migrating into a newly formed area (e.g. a lake, a volcanic island)
Lots of niches are vacant
The species diverges and fills the niches
Divergent evolution.
Darwin’s finches
© 2016 Paul Billiet ODWS

3. Divergent Evolution
Populations of a species that are separated and evolve under different selective pressures develop different adaptations as they diverge
They are usually geographically separated so that there is a barrier to the mixing of genes
Divergent evolution produces homologous organs
Organs where the same anatomical structure is adapted for different purposes.
e.g. the pentadactyl limb
© 2016 Paul Billiet ODWS

4. The pendadactyl limb
Lizard
Frog
Bat
Human
© 2016 Paul Billiet
ODWS

5. The Galàpagos Islands
© 2016 Paul Billiet ODWS

6. Daphne Major
© 2016 Paul Billiet ODWS

7. Peter & Rosemary Grant
© 2016 Paul Billiet ODWS

8. Geospiza fortis Drought © 2016 Paul Billiet ODWS
Peter R. Grant* and B. Rosemary Grant SCIENCE VOL 313 pp

9. Drought reduces small seeds
Selective pressure
Drought reduces small seeds
© 2016 Paul Billiet ODWS
Peter R. Grant* and B. Rosemary Grant SCIENCE VOL 313 pp

10. Geospiza magnirostris arrives
Arrival of G. magnirostris & El Niño event
© 2016 Paul Billiet ODWS
Peter R. Grant* and B. Rosemary Grant SCIENCE VOL 313 pp

11. Competition reduces large seeds
Selective pressure
Geospiza magnirostris
Geospiza fortis
Competition reduces large seeds
© 2016 Paul Billiet ODWS
Peter R. Grant* and B. Rosemary Grant SCIENCE VOL 313 pp

12. Another drought Drought © 2016 Paul Billiet ODWS
Peter R. Grant* and B. Rosemary Grant SCIENCE VOL 313 pp

13. Competition makes a difference
Drought
© 2016 Paul Billiet ODWS
Peter R. Grant* and B. Rosemary Grant SCIENCE VOL 313 pp

14. Over 30 years of research Food resources drove the selection G. fortis
Drought reduces small seeds and favoured larger seeds
Large beak sizes were favoured.
Competition with G. magnirostris reduced large seeds
G. fortis adapts to small seeds again
Both drought and competition reduces population size and favours small beak size.
© 2016 Paul Billiet ODWS