Natural Selection: Empirical Studies in the Wild (L18)

Exam 3 Lecture 18

Galapagos Islands

• 33 Islands

• Isla Isabela

• Isla Fernandina

• Santa Cruz

Tree Finches

Small Tree Finch

• Geospiza parvula

• least concern

• small with a short, curved beak

• insect diet

Medium Tree Finch

• Geospiza pauper

• Critically endangered

• Only found in the highlands of Floreana

Large Tree finch

• Geospiza psittacula

• Vulnerable

• large, powerful beak with a thick base

• found on several islands

Ground Finches

• All least concern

Small Ground finch

• Geospiza fuliginosa

• most common, found on most islands

Medium Ground Finch

• Geospiza fortis

• found on several islands

• seed diet

Large Ground Finch

• Geospiza magnirostris

• The largest finch in both size and beak size

• seed/nut diet

Sharp-Beaked Ground Finch

• Geospiza difficilis

• found on Darwin and Wolf islands

• seed/large seabird blood diet

• AKA Vampire finch

Cactus Finches

• All least concern

Common Cactus Finch

• Geospiza scandens

• Feed on Opuntia cacti/pollen/nectar/seeds/fruit

• will also eat vegetables and small invertebrates

Large Cactus Finch

• Geospiza conirostris

• varies heavily in appearance

• Range of foods, including Opuntia cacti

Other Finches

Mangrove Finch

• Geospiza heliobates

• critically endangered

• rare, only found on Isabela

Woodpecker Finch

• Geospiza pallida

• vulnerable

• uses tools to dislodge invertebrates from trees

Green Warbler Finch

• Certhidea olivacea

• vulnerable

• became a separate species in 2008

Grey Warbler Finch

• Certhidea fusca

• least concern

• found on small/dry islands

Oldfield Mice

• Light coloration can come from either a mutation of the Agouti or the Mc1r gene

• The Atlantic and Gulf coast mice evolved their light color independently

Snowshoe Hares

• Turn white in the winter, and brown in the summer

• Hares along the west coast will not turn white for the winter due to an Agouti mutation

• black + white tailed jackrabbits may be similar due to genetic introgression

Extended Phenotype

• A structure created by an organism that increases its performance/success

• Not part of the organism itself

Ex: Galls from gall flies or wasps serve as a food source/protection for developing larvae in oak trees or goldenrod

• Stabilizing selection, parasite wasps attack small galls, and Downy woodpeckers feed on big galls

John Snow + Cholera

• Natural experiment

• A major Cholera outbreak in Soho

• John Snow determined the source was a public water pump by mapping out where each death occurred

Three-spined Sticklebacks

• Anadromous (lives in seawater but breeds in fresh/brackish water)

• Some colonized lakes due to glaciers withdrawing

• Marine sticklebacks have heavier plating and longer dorsal spines

• Freshwater sticklebacks have less plating and shorter dorsal spines due to a low expression of the Eda gene

• armor is energetically costly, and there are fewer large predators in freshwater environments

Domesticated crops

• Wild cabbage → broccoli, collard greens, kale, brussels sprouts, etc.

• Corn used to have like 10 kernels total

Pesticides and Herbicides

• 52% of US land is attributed to agriculture

• Danish housefly populations adapt and become resistant to pesticides very quickly

• More than 220 species of weeds have become resistant to herbicides

• ESPS leads to roundup resistance in plants

• Refugees slow the evolution of resistance (Bt-free refugees take up 20% of crop area and are required by law)

Cane Toads

• Introduced in Australia

• Began evolving smaller bodies/poison glands and longer legs

• Black snakes that eat these toads are evolving increased toad toxin resistance, larger body size, and smaller mouths

Cod

• In 1992 northern cod fell to 1% due to overfishing

• Even after protections were put in place, the cod never recovered

• The remaining cod breed earlier and are much smaller