Lecture 7: Alternative Mating Strategies Flashcards
Evolutionary Origin of Two Sexes:
- Ancestral state: equal sized gametes
- mutant with small gametes arises
- small + small = 50% of size
- Small + large = 75% of size
Graphical model for calculating optimal size of embryo:
- 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
when are small gametes favoured?
only when in a population of large gametes, as 2 small = 50% of embryo, one small and one big = 75%
sperm competition:
the competition between the sperm of two or more males inside the females reproductive tract
Outcompeting rivals: Male damselflies
remove the sperm of rivals
in insects polyandrous males produce a ____ proportion of viable sperm than monogamous males
higher
Male Adelie penguins strategically allocate sperm to
-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.
Magpie and Zebra finch method of outcompeting rivals
male guard their mates and drive off rivals
sperm competition specifically tries to ensure ___ takes place, not simply just copulation
Fertilisation
Mate guarding in Seychelles Warblers
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
Mate guarding in Blue Milkweed Beetles experiment to see if they found new mates after being removed, is mate guarding beneficial??
- 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
male Fulmars method in ensuring paternity
- male fulmars copulate over 50 times with their partners
- frequent copulation ensures optimal thing of insemination relative to fertilisation
Cryptic female choice:
female manipulation inside her reproductive tract to that a preferred male fertilises her eggs
domestic chicken and cryptic female choice:
store sperm in storage tubule in the reproductive tract
sperm ejection in chickens:
females eject the VIABLE sperm of subordinate males and accept the sperm of dominant males
sperm ejection in Dunnocks:
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
nuptial gifts and sperm acceptance in Mecoptera:
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
why do females engage in CFC ?
1) higher quality offspring (by cryptically choosing high quality fathers)
2) more offspring (by cryptic choice of genetically compatible males)
CFC for nuptial gifts, Nursery Web Spider (Pisaura mirabilis)
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
alternative mating strategies: 2 types
1) alternatives are not equally rewarding (best of bad job)
2) alternative that are equally rewarding
alternative mating tactics in Scorpion Flies
-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
alternative tactics: male morphs in an Isopod living in sponge
-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
alternative male tactics in Bluegills
- Territorial (large)
- Little sneakers (small)
- Satellies (medium)
- -> small and medium sneak and release spores at same time as territorial
____ is the most important act in the life of any animal
passing on genes, hence the wide variety of behavioural strategies to achieve reproduction
