DARWIN’S FINCHES © 2016 Paul Billiet ODWS.

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Presentation transcript:

DARWIN’S FINCHES © 2016 Paul Billiet ODWS

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

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

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

The Galàpagos Islands © 2016 Paul Billiet ODWS

Daphne Major © 2016 Paul Billiet ODWS

Peter & Rosemary Grant © 2016 Paul Billiet ODWS

Geospiza fortis Drought © 2016 Paul Billiet ODWS Peter R. Grant* and B. Rosemary Grant SCIENCE VOL 313 pp224-226

Drought reduces small seeds Selective pressure Drought reduces small seeds © 2016 Paul Billiet ODWS Peter R. Grant* and B. Rosemary Grant SCIENCE VOL 313 pp224-226

Geospiza magnirostris arrives Arrival of G. magnirostris & El Niño event © 2016 Paul Billiet ODWS Peter R. Grant* and B. Rosemary Grant SCIENCE VOL 313 pp224-226

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 pp224-226

Another drought Drought © 2016 Paul Billiet ODWS Peter R. Grant* and B. Rosemary Grant SCIENCE VOL 313 pp224-226

Competition makes a difference Drought © 2016 Paul Billiet ODWS Peter R. Grant* and B. Rosemary Grant SCIENCE VOL 313 pp224-226

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