Lecture 24

Question 1

major threats to biodiversity

Answer 1

• habitat destruction
• overexploitation
• invasive species
• pollution
• climate change

often have synergistic effects

Question 2

what four things can result from environmental change?

Answer 2

acclimation, adaptation, range shifts or extinction

Question 3

give 4 examples of changes to the environment due to humans

Answer 3

• ice disappearing
• forests cut down
• primates sold as pets or bushmeat
• mercury put in rivers
• microplastics

Question 4

effects of increasing atmospheric CO2 levels in the last century

Answer 4

• human activities adding more CO2
• intensifies greenhouse effect and causes global warming
• global temperature has increased dramatically

Question 5

how is climate changing other than temperature?

Answer 5

• circulation patterns are changing: Hadley cells get stronger and therefore larger, causing desert belts shifting poleward beyond 30 degrees
• extreme weather events becoming more frequent

Question 6

what happens to organisms as the climate changes?

Answer 6

acclimatisation through phenotypic plasticity
adaptation to new conditions
range shift migration to suitable conditions
extirpation, which is global or local extinction

Question 7

acclimation

Answer 7

Early or gradual exposure to environmental stress can reduce its negative impacts
- Porcelain crabs (Petrolisthes) acclimated
to cold temperatures function better at colder temperatures
- But acclimation to warm temperatures increases high-temperature tolerance only minimally

Question 8

give an example of how climate change is more than just the direct effects of warming

Answer 8

Snowshoe hares (Lepus Americans) are white in winter and brown in summer
Coat colour is important for reducing predation, and white animals are conspicuous against a snowless background

Question 9

Mills et Al.

Answer 9

• studied snowshoe hares in western Montana over 3 consecutive winters
• radio-collared hares and performed weekly measurements of coat colour and snow around each hair
• wanted to determine whether there I sufficient, current plasticity in the initiation or rate of coat colour change to reduce mismatch and respond to changes in snow cover

Question 10

Mills et Al. results

Answer 10

• it is getting cooler later in the fall and warmer earlier in spring
• in general, snow is arriving later and leaving earlier
• there is little variation in fall coat change; there is more variation in spring coat change

Question 11

so, will plasticity alone in coat colour change able to respond to changes in conditions?

Answer 11

No, there is not enough plasticity to avoid mismatches
- projections of future snow duration show there will be greater mismatch between snowshoe hare coat colour and its background

Question 12

how is coat colour mismatch predicted to affect hare population growth?

Answer 12

predicted to slow it

Question 13

so, will hares adapt?

Answer 13

open question; depends on the amount and type of genetic variation underlying the timing of coat colour change

Question 14

range shifts

Answer 14

• species moving polewards
• also up mountains

Question 15

give an example of an animal that can’t go up mountains

Answer 15

pikas; death zone at low altitude

Question 16

the Great Basin

Answer 16

many small mountain ranges, green ‘sky islands’ in a matrix of desert

Question 17

are pikas threatened by climate change?

Answer 17

The elevational range of American pikas in the Great Basin is getting smaller
- Sites where pikas have gone locally extinct often had temperatures above 26°C, which can be lethal to pikas (if they cannot behaviourally thermoregulate)
- The American pika was under consideration to be listed as an endangered species in the US (but the US ultimately decided against it)
- On the other hand, American pika populations in the Rocky Mountains and elsewhere appear to be healthy
(Smith et al. 2020)
- In Canada, the Collared pika (which lives in the Yukon, Northwest Territories, and BC) is federally designed as a species of “Special Concern’

Question 18

example of landscapes defeating migrations

Answer 18

Pronghorns can run but not jump. Whole herds have been killed at fences in the winter

Question 19

is extinction reversible

Answer 19

no

Question 20

most extinction models ignore

Answer 20

many factors thought to be important in determining future extinction risks such as species interactions, dispersal differences, evolution