Island Evolution, Natural Selection and Darwin’s Finches Measuring Natural selection and evolution using island environments

Biological Evolution on Islands Islands are unique because they are similar Unique effects Similar processes Islands are smaller versions of continents Smaller size + populations Fewer species/Less complexity Change occurs more rapidly

Biological Evolution on Islands Island Evolution Predictable Deterministic Natural Selection “Survival of the fittest” Genetic Drift “Survival of the lucky” Random Stochastic Both are easier to observe/study on islands

Island Evolution - Unique Effects Dispersal Ability/Loss of Dispersal Ability Island species must be good at dispersal/ colonization Often show loss of dispersal ability after colonization Kiwi – New Zealand Dodo - Mauritius

Island Evolution - Unique Effects Size Change Dwarfism Gigantism Pygmy Hipp0 - Madagascar Giant Tortoise - Galapagos

Island Evolution - Unique Effects Loss of defensive mechanisms Lack of predators Lesser Bird of Paradise – New Guinea Rattleless Rattlesnake – Santa Catalina

Island Evolution - Process Survive Reproduce Adapt Evolve Migrate Don’t Survive Don’t Reproduce Don’t Adapt Extinction Evolution and Extinction occur at faster rates on islands

Measuring Natural Selection and Evolution Peter and Rosemary Grant – Princeton University Research from 1973 – present Research on Daphne Major in Galapagos Islands Small island with simple ecology Able to mark, measure and track every bird, every birth, every death

Galapagos Islands Daphne Major

Daphne Major Daphne Major from the air Area = 0.31 km2 Elevation = 120 m Peter and Rosemary Grant in 2010 Spent 30+ research seasons on Daphne Major

Daphne Major Plants/Finch Food Prickly Pear Cacti Tribulus seeds

Darwin’s Finches Geospiza scandens Geospiza magnirostris Geospiza fortis

Beak shapes and sizes are adapted to bird’s primary food source Darwin’s Finches Beak shapes and sizes are adapted to bird’s primary food source

°=1976 population and • =1978 population Research Question 1: Is beak size inherited/heritable? What hypothesis? What data to collect? Offspring Bill Depth (mm) Midparent Bill Depth (mm) °=1976 population and • =1978 population

Research Question 2: Did natural selection occur? What hypothesis? What data to collect?

Natural Selection Data Natural Selection = differential survival

Research Question 3: Did evolution occur? What hypothesis? What data to collect?

Evolution = Change over time Evolution Data Evolution = Change over time

Conclusions Natural selection occurred in extended dry season of 1977 Birds lived and died based on beak size, where large beak size was advantageous in cracking large seeds Evolution occurred between 1976 and 1978 Beak size of population increased because of survivor reproduction

Conclusions Natural selection occurred in the El Nino wet season of 1982 Birds lived and died based on beak size, where smaller size was advantageous in eating smaller seeds Evolution occurred between 1981 and 1983 Beak size of population decreased because of survivor reproduction