Climate Change and Speciation

How Do New Species Evolve?

• Speciation: one species splits into two or more species

• Geographic isolation: happens first; physical isolation of populations for a long period

• Reproductive isolation: mutations and natural selection in geographically isolated populations lead to inability to produce viable offspring when members of two different populations mate

Speciation Example• population of fruit flies laying eggs on several bunches of

rotting bananas• hurricane washes the bananas and the immature fruit flies

out to sea• bunch washes up on an island off the coast of the mainland• fruit flies mature and emerge on new island• populations, mainland and island, are now too far apart for

gene flow to unite them. Speciation has not occurred yet—reunited, they could produce viable offspring.

• conditions are different on the island with different selective pressures

• another storm reintroduces the island flies to the mainland but changes in courtship or mutations in genes prevent reproduction

Climate Change

• What factors change?– Weather patterns, water, overall temp

• What trophic levels are initially impacted?– Plants and herbivores– Any species with narrow niche requirements– Impact up food chain

Example

• Horses in Oregon

Punctuated Equilibrium

Migration

Behavior Change• Reindeer expected to disappear from current range by end of century• Marmots end hibernation 3 weeks earlier than they did 30 years ago• Canadian red squirrels breeding about 18 days earlier• Red foxes spreading north -- territory occupied by their arctic cousins• Polar bears thinner than those of 20 years ago• Elephant seal pups leaner because prey is migrating to cooler waters• Loggerhead sea turtles laying eggs 10 days earlier than 15 years ago• Rising temp affect the sex of Hawkbill turtle hatchlings—more females• Warm water organisms (barnacles, mollusks, tidal snails) moving north• Fish species moving north in search of cooler waters• Tree swallows laying eggs about nine days earlier 40 years ago• Common murres breeding 24 days earlier than a decade ago• Plants thriving in areas where growth was limited before• Plants like columbines and wild geraniums blooming earlier • Edith's checkerspot butterflies are moving northward

Adaptation

• Requires:– Genetic variety– Time

• Common Misconceptions– Not “for” anything– Predicting the future– “Survival of the fittest” is not “survival of the strongest” – Organisms do not develop traits out of need or want– No grand plan of nature for perfect adaptation

Climate Change and Catastrophes Affect Natural Selection

• Ice ages followed by warming temperatures

• Collisions between the earth and large asteroids – New species– Extinctions

Changes in Ice Coverage in the Northern Hemisphere During the last 18,000 Years

Fig. 4-9, p. 89

Geographic Isolation Can Lead to Reproductive Isolation

Fig. 4-10, p. 91