special reading - post copulation sexual selection - 1 - multiple mating and genetically loaded sperm competition in gouldian finch

Question 1

what is the question of the experiment?

Answer 1

what is the benefit of extra pair copulation to gouldian finches

Question 2

what is the hypothesis?

Answer 2

females take part in EPCs to ensure comparable mates therefore increasing chance of offspring reaching adulthood

Question 3

what is the aim?

Answer 3

to understand pre and post copulatory selection for extra pair mates in gouldian finches

Question 4

what are the methods?

Answer 4

• had a population of gouldian finches - half compatible and half incompatible - then separated the pairs and placed a virgin male either incompatible or compatible with the female for 60 mins
• wanted to see if females in an incompatible pair were more likely to engage in EPCs with compatible mates - used the other treatments as controls
• experimental design provided a predicted adaptive context, a maladaptive context, and two selectively neutral situations

Question 5

what were the results?

Answer 5

despite morph mate preferences in selection against mix morph mating females across all experimental contexts were equally likely to engage in EPCs - 31/40

all successful copulations were preceded by active female solicitation

new males sexually displayed to females in 95% of trials - indiscriminate of colour morphs

Question 6

what was the outcome of sperm competition?

Answer 6

• the females can store sperm from the males for a while so postcopulatory sexual selection Is important
• as predicted the 31 successful EPCs resulted in a disproportionate number of fertilised offspring among broods
• furthermore more offspring per brood were fathered by the Extra pair male in the adaptive context i.e compatible
• females in incompatible pairs that partook in EPCs with compatible pairs had a 40% increase in offspring

Question 7

what do the results mean?

Answer 7

findings suggest that to understand the evolution of female polyandry in socially monogamous animals, we need to account for both pre and post copulatory processes
- results suggest that lack of research my underestimate behavioural infidelity and the adaptive benefits to females