Mate guarding, sperm competition and sexual conflict Flashcards
What is the primary goal of sexual selection in males?
To maximise their paternity, even after mating
What is Parentage assurance?
evolved mechanisms to increase one’s chances of being the parent of offspring:
1.) Mate guarding
2.) Sperm competition
3.) Sexual conflict
What is mate guarding?What is the ultimate aim?
when one sex (typically male) prevents same-sex competitors having access to it’s mate (in an attempt to achieve reproductive monopoly of mate).
Name an example of Pre-copulatory mate guarding
Pupal mating in Heliconius butterflies where males search for females on host plant and compete for the possession of pupa (no female choice involved).
What are the two main types of mate guarding?
Pre-copulatory and post-copulatory mate guarding
What is sperm competition?
Competition for fertilizations by sperm from different males within a single female’s reproductive tract.
How do males ensure parentage assurance?
Through mechanisms like mate guarding, sperm competition, and decreasing female receptivity
What is a mating plug?
A structure left by a male after mating to prevent reinsemination by other males.
In which species was a significant percentage of male matings found to fail due to recent mating?
Locusts (Locusta migratoria).
What is the effect of mating plugs on female mating success?
They can significantly decrease the likelihood of successful subsequent matings.
What role do sperm scrapers play in sperm competition?
They allow males to remove rival sperm from the female’s reproductive tract.
What is the significance of the last male to fertilise a female?
The last male typically gains the most fertilisations of eggs
How do cooperative sperm work in wood mice?
50-100 sperm form a ‘train’ to enhance speed and fertilization efficiency.
What is sexual conflict?
An evolutionary conflict arising between sexes due to differing fitness optima.
How does mating affect female longevity in Drosophila melanogaster?
Mating can decrease female longevity due to toxic effects of male seminal fluid.
What is the relationship between testis mass and sperm competition?
There is a positive correlation; larger testis mass often indicates higher levels of sperm competition.
What is the evolutionary rationale behind male manipulation of female receptivity?
Males may manipulate females to decrease receptivity to secure their paternity.
What is the benefit of pre-copulatory mate guarding?
It ensures that the male is present when the female becomes receptive, thus securing paternity
Why might mate guarding be costly for males?
It can involve risks like predation, loss of feeding opportunities, and missed chances to find other mates
What is the mating strategy of Heliconius butterflies?
Males guard female pupae to mate as they emerge.
What is the role of seminal fluid peptides in Drosophila melanogaster?
They boost male fertilisation success, increase female egg production, and decrease female receptivity
How do male damselflies compete for fertilisation?
They use spines on their secondary genitalia to scrape out rival sperm.
What is the significance of cooperative sperm in murine rodents?
They show variations in sperm shape and curvature, which correlate with testis mass and competition intensity.
What is the mating behaviour of the Yellow Dung Fly?
Males mount females post-copulation to prevent sperm displacement by other males.
What is the cost of mate guarding to males?
-cost of feeding
-cost of increased risk of predation
-cost of lost opportunities to find other females close to their receptive period
Name an example of post-copulatory mate guarding
-Pondskater–> precopulatory phase (1.5 min) plus copulation (16.2 min)
-Postcopulatory phase (male rides passively on the back of the female without genital contact (11 min–> 48 h)
How is Post-copulatory mate guarding favoured?
-Females remain receptive post copulation (hence mating with new male is possible)
-Interval between copulation and egg-laying is short hence guarding male doesn’t have to guard for too long
-finding mates is easier (encountering is high).
-last male to fertilise female gains most fertilisations of eggs (hence new male would gain paternity of young at expense of original male).
Name another example of post-copulatory guarding
Canids but where is high predation risk
How does polyandry affect sperm competition?
Females mating with multiple males increases competition among sperm for fertilization
What is the expected outcome of sexual conflict in mating systems?
It often leads to males favoring short-term female health to maximise their reproductive success
What is the relationship between mating systems and sexual conflict?
The occurrence of sexual conflict depends on mating systems, social systems, and relatedness structures.
What is the significance of the cooperative behaviour of sperm in competition?
It enhances the chances of fertilisation by working together against unrelated sperm.
What does the term “mating plugs” refer to in locusts?
Structures that prevent females from mating again shortly after a successful mating
Give an example of mating plugs
-26% of male matings fail if female has recently mated
-successful matings still last 4 times longer than matings with females
–> mating males leave a mating plug to prevent reinsemination
How do males in some species manipulate female fitness?
By transferring substances that can decrease female longevity and receptivity.
What is the benefit of post-copulatory mate guarding?
It protects the male’s sperm from being displaced by subsequent matings.
What is the evolutionary interest of a male in the short-term welfare of a female?
To ensure she remains healthy long enough to lay the eggs he has fertilised.
How does the mating behaviour of males in species like crickets illustrate sperm competition?
Males with smaller, more numerous sperm tend to father more offspring when competing with others.
What is Sexual selection a balance of?
male-male competition and female choice
What does sexual selection give males?
a platform to show females their traits where females ultimately choose to create the next generation of offspring
What is Sperm competition?
competition for fertilisations by sperm from different males within a single female’s reproductive tract
What is Sperm competition driven by?
selection on each male to maximise his paternity
How does a mating plug function in locusts?
In locusts (Locusta migratoria), successful matings last about four times longer than unsuccessful ones, and males leave a mating plug to prevent females from mating again
How do male damselflies engage in sperm competition?
Male damselflies use spines on their secondary genitalia to scrape out the sperm of rival males from the female’s reproductive tract.
What is the significance of testis mass in birds regarding sperm competition? What does this indicate?
There is a significant positive correlation between relative testis mass and the level of extra-pair paternity, indicating that males with larger testes produce more sperm and have a higher chance of fertilisation
Describe the cooperative sperm behaviour observed in Wood Mice
In Wood Mice (Apodemus sylvaticus), 50-100 sperm can form a ‘train’ using hooks on their heads or entwined tails, which gives them a speed advantage over single sperm.
How do males of Drosophila melanogaster manipulate female fitness?
Males transfer peptides in seminal fluid that boost their fertilization success, increase female egg production in the short term, but decrease female receptivity and longevity in the long term
What is the evolutionary rationale behind male manipulation of female receptivity?
Males may manipulate female receptivity to prevent her from mating with other males, thus ensuring their paternity, even if it shortens her lifespan
Why is the duration of mate guarding a compromise for males?
The duration and frequency of mate guarding balance the costs of not feeding, increased predation risk, and lost opportunities to find other receptive females.
What is the relationship between sperm size and quantity in the context of sperm competition?
The evolution of numerous, small, motile sperm and larger testes is driven by the need to maximize the chances of fertilization in competitive environments.
