Chp 3: Evolution, Biodiversity, and Ecology
Central Case Study: Saving Hawaii’s Native Forest Birds
Disruptive selection favors two extremes
Directional selection favors one trait
1) Summarize
This study focused on how Hawaii’s island chain has supported the life of so many species of
birds. It used to be the habitat of over 100 species, however, half of the species have recently
gone extinct due to human-introduced species like pigs, cattle, rats, and cats (which are the #1
cause of bird deaths in the billions per year). Additionally, avian malaria (carried by vector =
mosquitos) has targetted native bird species at lower elevations (increasingly a problem with
warming temperatures where mosquitos thrive, and gain elevation).
- Rats came on ships, cats were brought to catch rats
- Mongoose- eat anything + supposed to eat rats but eat native bird eggs
- Great egg foragers
- Pigs eat everything and decimate the landscape
2) Importance
This study mentions that because Hawai’i is so isolated, only bats (mammal) came naturally
meaning that there was a lack of selective pressures to change the defenses of native plants and
animals. With this peaceful history, the introduction of new species by colonizers has caused the
extinction of many native species. It shows how important and delicate ecosystems are and how
without previous pressures, anthropogenic changes come too sudden for nature to adapt
leading to mass extinctions (the sixth).
Central Case Study: Saving Hawaii’s Native Forest Birds
Disruptive selection favors two extremes
Directional selection favors one trait
1) Summarize
This study focused on how Hawaii’s island chain has supported the life of so many species of
birds. It used to be the habitat of over 100 species, however, half of the species have recently
gone extinct due to human-introduced species like pigs, cattle, rats, and cats (which are the #1
cause of bird deaths in the billions per year). Additionally, avian malaria (carried by vector =
mosquitos) has targetted native bird species at lower elevations (increasingly a problem with
warming temperatures where mosquitos thrive, and gain elevation).
- Rats came on ships, cats were brought to catch rats
- Mongoose- eat anything + supposed to eat rats but eat native bird eggs
- Great egg foragers
- Pigs eat everything and decimate the landscape
2) Importance
This study mentions that because Hawai’i is so isolated, only bats (mammal) came naturally
meaning that there was a lack of selective pressures to change the defenses of native plants and
animals. With this peaceful history, the introduction of new species by colonizers has caused the
extinction of many native species. It shows how important and delicate ecosystems are and how
without previous pressures, anthropogenic changes come too sudden for nature to adapt
leading to mass extinctions (the sixth).
