Lecture 7: Alternative Mating Strategies

Question 1

Evolutionary Origin of Two Sexes:

Answer 1

• Ancestral state: equal sized gametes
• mutant with small gametes arises
• small + small = 50% of size
• Small + large = 75% of size

Question 2

Graphical model for calculating optimal size of embryo:

Answer 2

• S graph, optimal size of embryo, if half size is over half of survival then beneficial
• b = small and large embryo
• b > 1/2 of a (2 large)
• small must = half of large

Question 3

when are small gametes favoured?

Answer 3

only when in a population of large gametes, as 2 small = 50% of embryo, one small and one big = 75%

Question 4

sperm competition:

Answer 4

the competition between the sperm of two or more males inside the females reproductive tract

Question 5

Outcompeting rivals: Male damselflies

Answer 5

remove the sperm of rivals

Question 6

in insects polyandrous males produce a ____ proportion of viable sperm than monogamous males

Answer 6

higher

Question 7

Male Adelie penguins strategically allocate sperm to

Answer 7

-EPC
Male Adélie penguins withhold sperm from their mates, with whom they copulate frequently, and allocate it instead to extra-pair females, with whom they may have only one chance to mate.

Question 8

Magpie and Zebra finch method of outcompeting rivals

Answer 8

male guard their mates and drive off rivals

Question 9

sperm competition specifically tries to ensure ___ takes place, not simply just copulation

Answer 9

Fertilisation

Question 10

Mate guarding in Seychelles Warblers

Answer 10

males mate guard the females during their fertile period

-in experiment with fake egg (no mate guarding) higher number of intrusions, EPC attempts and successful EPC’s

Question 11

Mate guarding in Blue Milkweed Beetles experiment to see if they found new mates after being removed, is mate guarding beneficial??

Answer 11

• 25% of separated males found a new mate within 30 minutes. So guarding results in missed mating opportunities.
• 50% of females found a new mate after male removal. So guarding prevents females from relating.
• if the last male copulates wand fertilises >40% of the eggs, beneficial to mate guard

Question 12

male Fulmars method in ensuring paternity

Answer 12

• male fulmars copulate over 50 times with their partners

- frequent copulation ensures optimal thing of insemination relative to fertilisation

Question 13

Cryptic female choice:

Answer 13

female manipulation inside her reproductive tract to that a preferred male fertilises her eggs

Question 14

domestic chicken and cryptic female choice:

Answer 14

store sperm in storage tubule in the reproductive tract

Question 15

sperm ejection in chickens:

Answer 15

females eject the VIABLE sperm of subordinate males and accept the sperm of dominant males

Question 16

sperm ejection in Dunnocks:

Answer 16

male may peck at his partners cloaca if another male has been near her
-in response she may eject a droplet of fluid containing sperm but this sperm is NON VIABLE

Question 17

nuptial gifts and sperm acceptance in Mecoptera:

Answer 17

hanging flies males give a nuptial gift to the female, while she if snacking the male mates and transfers sperm

• once she has finished eating she chuck off the male and copulation ends, gift must be large enough to ensure sperm transfer occurs
• sex takes 20 mins

Question 18

why do females engage in CFC ?

Answer 18

1) higher quality offspring (by cryptically choosing high quality fathers)
2) more offspring (by cryptic choice of genetically compatible males)

Question 19

CFC for nuptial gifts, Nursery Web Spider (Pisaura mirabilis)

Answer 19

Female nursery spiders store more sperm from males that have given them nuptial gifts than from males that haven’t, and their eggs have greater hatching success if they mated with a gift giving male

Question 20

alternative mating strategies: 2 types

Answer 20

1) alternatives are not equally rewarding (best of bad job)

2) alternative that are equally rewarding

Question 21

alternative mating tactics in Scorpion Flies

Answer 21

-Large males: guard dead insects attractive to females
-medium: produce salivary gifts to attract females
-small: force copulations on females
–> alternative tactics with unequal fitness
- med will adopt large tactics if they’re removed
==best of bad bunch, smallest less successful than large

Question 22

alternative tactics: male morphs in an Isopod living in sponge

Answer 22

-Alpha (fighter)
-Beta (female mimic)
-Gamma (hider)
-three morphs have different genotypes
-and occur at frequencies at which their fitness is equal
-shuster & Wade 1991
== equal fitness for all methods

Question 23

alternative male tactics in Bluegills

Answer 23

• Territorial (large)
• Little sneakers (small)
• Satellies (medium)
• -> small and medium sneak and release spores at same time as territorial

Question 24

____ is the most important act in the life of any animal

Answer 24

passing on genes, hence the wide variety of behavioural strategies to achieve reproduction