ARTs and sperm competition

Question 1

alternative reproductive tactics

Answer 1

alternative ways that members of one sex obtain fertilization and reproduce.
discontinuous behavioural/morphological/physiological traits selected to maximize fitness in 2+ alternative ways. Individuals will allocate resources to either one or the other ways of achieving reproduction

Question 2

bluegil sunfish ARTs

Answer 2

territorial male
sneaker male (later satellite male)

territorial male takes care of the nest and attracts females.
the sneaker males imitate females and are allowed towards the nest, fertilizing young without the territorial male knowing.

Question 3

how do ARTs evolve?

Answer 3

if there is fitness to be gained in pursuing different reproductive tactics.
there is some investment to be exploited by same sex competitors.
when intermediate expression of a trait is not possible or is selected against. (disruptive selection)

polymorphic genotypes (frequency dependent selection, where alternatives have equal lifetime fitness)
monomorphic genotypes (condition dependent selection, where tactic is adopted dependent on condition or status. “best of a bad job”, and dont have equal fitness)

Question 4

frequency dependent selection

Answer 4

fitness of a trait depends on how common it is in the population

positive- fitness increases as trait becomes common
negative- fitness decreases as trait becomes common (this allows the traits to co-exist, as rare traits will have high frequency. at some point the fitness of either tactic will become equal)

Question 5

condition dependent selection

Answer 5

monomorphic genotype
tactics adopted due to diverging conditions. no assumption of equal fitness.

Question 6

strategy vs tactic

Answer 6

strategy is a genetically based decision rule. differences in strategy are due to differences in genes.
tactic is a behavioural pattern played as part of a strategy. there is only one set of genes but 2+ alternative tactics within that one conditional strategy. tactics result from bad luck, not bad genes.

Question 7

sperm competition

Answer 7

competition between sperm of 2+ males for the fertilization of a female’s eggs

Question 8

forms of sperm competition tactics

Answer 8

mating plugs
mate guarding
release anti mating substances to prevent remating from females

Question 9

correlation between sperm number and fertilization success?

Answer 9

positive.

Question 10

what influences sperm number

Answer 10

relative testes mass
sperm density
ejaculate volume

Question 11

increased sperm competiton leads to what condition in sperm motility?

Answer 11

faster swimming sperm, and longer swimming duration

Question 12

as sperm competition increases, what can we predict will also increase?

Answer 12

sperm number
tail length
swimming speed
swimming duration
testes mass

Question 13

what mating system sees the most and least amount of sperm competition?

Answer 13

multiple mating systems see the most, and monogamous systems see the least

Question 14

how do different reproductive tactics compare in sperm competition?

Answer 14

territorial males invest in growth, courting and resources.
sneaker males invest in reproduction, so they invest more heavily in sperm competition.

Question 15

what is a morphological difference between territorial and sneaker males due to sperm competition?

Answer 15

sneaker males have relatively much larger testes and faster swimming sperm, with more sperm density and helical heads on their sperm

Question 16

describe strategic sperm allocation

Answer 16

ejaculates are costly and finite, so when rivals are around, there will be more ejaculation to increase competitiveness. subordinates will do this more than rivals since its all they have.if theres no rival, no need to ejaculate as much since your sperm has a higher chance of fertilizing.

Question 17

sperm allocation in humans study

Answer 17

males were given porn to ejaculate to, and when the porn had other men in it (high sperm competition), their sperm was more motile