migratory divides and speciation

Question 1

olfaction navigation

Answer 1

Wallraff, cut the olfactory nerve of inexperienced birds, found that they could no longer navigate home

Question 2

infra-sound

Answer 2

• low frequencies can be heard by birds, as can whales
• humans hear down to 20 Hz, birds down to 0.1 Hz
• may allow birds to hear wind currents, thunderstorms, sea waves

Question 3

social learning

Answer 3

-many birds, ie. ducks, geese, cranes, learn socially how/where to migrate

Question 4

genetic control of migration

Answer 4

• Berthold and Helbig experimented with breeding and selection experiments, finding that tendency to migrate was highly heritable, capable of rapid evolutionary change
• found that different populations of a species, with differing genetics, were prone to migrating in different directions
• breeding birds with parents who migrated in opposing directions would yield offspring that migrated in the direction halfway between their parents’ directions

Question 5

aspects of migratory behaviour are inherited genetically

Answer 5

• direction, length of migration, feeding behaviour, timing of migration
• this may explain low survivability of hybrids, as their migration patterns are all thrown off and thus have lower reproductive rates

Question 6

reproductive isolation; premating/postmating

Answer 6

premating/prezygotic=factors preventing two groups from choosing each other as mates
-ie greenish warblers songs or plumage

postmating/zygotic=factors that cause direct selection against hybrid offspring
-ie. changed migration patterns, northwestern migrate to india, northeastern migrate to southeast asia

Question 7

ring species and migratory divide

Answer 7

• instinctive migratory direction changes abruptly in north, but gradually changes around the ring
• thus hybrids are found to migrate directly south, between india and southeast asia

Question 8

does migration promote speciation in greenish warblers?

Answer 8

need 4 things:

• separate origin of northern forms
• different migratory routes
• hybrids have intermediate migratory behaviour
• hybrids are selected against because of migration

Question 9

asian migration pattern survey

Answer 9

• tibet is large barrier to migrating birds
• species migrate only one way around tibet
• species that go both ways have a migratory divide between subspecies
• different migratory behaviors rarely coexist in same gene pool
• may play large role in speciation of siberian birds

Question 10

is there a narrow migratory divide in swainson’s thrushes

Answer 10

• migration differs more than any other trait between the forms
• narrow due to hybrids?
• hybrids took an intermediate route