Introduction to postcopulatory sexual selection- Week 4, part 1. Flashcards
What is postcopulatory sexual selection?
Refreshing your memory on Bateman’s 1948 fruit fly study.
Summarise the findings.
Does this study show a classic view?
How do males benefit?
Selection after mating has started.
Showed that males can benefit from mating with multiple females (increases the offspring they produce) + Females cannot benefit in the same way by mating with multiple males.
Yes.
Females lay eggs, the more eggs males get to fertilise it, the more offspring they leave behind.
In many species, can females benefit from mating with multiple partners?
Was it obvious why females can benefit?
What might this be because of?
Yes but not to the same extent that males can (a male can double the number of offspring he leaves behind by mating with two females).
No.
Could be because of male bias in scientific research.
What happened in the 1980s?
Name the 7 reasons:
In the 1980s, Robert Smith set out a number of reasons females could benefit from mating with multiple males.
1) “Good genes”.
2) “Sexy sons”.
3) Genetic diversity.
4) Fertility backup.
5) Material resources.
6) Protection.
7) Paternity confusion.
When are indirect benefits particularly relevant?
What happened in the 80s?
In mammal species where the males do not do much aside from provide sperm then disappear. The benefits of being choosy are indirect.
There was advances in fingerprinting technology.
What can species in the wild do at times?
What can females do in terms of this?
Who was this noticed in?
In the wild, males and females can raise offspring together. The male who is proving direct benefits does not necessarily have to be the genetic father of the offspring.
Females can get their direct benefit from one male (or more) and get their genetic heritable benefit from another male.
In birds.
Facultative polyandry for good genes:
What do bird species look like they have?
What happened once DNA fingerprinting became available?
What did behavioural ecologists realise?
Couples where they look after the chicks together.
It became apparent that the male visiting the nest and feeding the chicks was not necessarily the genetic father of the offspring.
They realised that females in some bird species were engaging in extra pair copulations (they formed their own pair but were copulating with other males).
Continuation from facultative polyandry for good genes:
What does facultative mean?
What does polyandry mean?
This is when an animal adjusts what it is doing in response to its situation to make the best of the situation.
Polyandry is when a female mates with multiple males (poly means multiple, andres means male).
Continuation from facultative polyandry for good genes:
What do females in some bird species do?
What might be the case?
Give an example of what females might do?
Females in some bird species mate with more than one male so they can get direct benefits from one male and indirect benefits from other males.
It might be the case that the male who is best at providing direct benefits might not be the one that is best at providing indirect benefits.
For example, they might get their food from one male and get their genetic material from another male that can give them sexy sons.
Genetic diversity:
Is this a less elaborate reason females can benefit from mating with multiple females?
What is the idea of genetic diversity? Explain and useful.
Yes.
The idea of it is, if you are going to have offspring and they all have the same father that male for example could be vulnerable to a particular disease and now your offspring will be vulnerable to that disease.
It might be useful to have variation in your offspring so that they are not all vulnerable to the same problems like if the environment changes some of them will be okay.
Continuation from genetic diversity:
What can females do and how is this beneficial?
What is this now?
Females can lay lots of eggs and benefit from getting those eggs fertilised by a variety of males so that they are all a little different.
This is one important potential benefit females could get from mating with multiple males.
Fertility backup:
Explain this.
What is it essentially?
The breeding season is short and females have to get their eggs fertilised quickly. Females might mate with a male that is not capable of fertilising their eggs, this is risky- they could mate with multiple males for fertility back up.
It is backup if one males sperm does not work.
Material resources:
How does this make females mate with multiple males?
What can this lead to?
Give an example of an insect which might engage in this for benefits reason (not saying that they do).
If females mate with multiple males, they could get multiple gifts.
This leads to them being better nourished and laying more eggs. They are better nourished because they could receive something like a spermatophore or saliva.
Female spiders- mate with multiple males as they will get to eat them after.
Protection:
Who is protection not only from?
Who can they get protection from?
What can happen?
Protection is not always from predators, it could be other members of the same species.
Multiple males.
If one of their males get eaten they can get another male and get protected by him.
Paternity confusion:
What can happen in some species?
What might some species not know and what would they use?
Males can be very aggressive to offspring that is not their own and even kill them.
In species like primates (monkeys) and lions, the males might not know if the offspring is actually there’s, they have to use rules of thumb to decide whether young members of a species is related to them.
Continuation from paternity confusion:
What is a simple rule of thumb they might use and what will this lead to?
Essentially, why do females mate with multiple males?
A simple rule of thumb is do these young belong to a female I have mated with recently, they are more likely to protect these offspring if that is the case.
Females might mate with multiple mates to create confusion to protect their offspring.
