The Environment InstituteWhere ideas grow

Professor Leigh Simmons

Sperm competition and sexual selection

Sperm Competition and Sexual Selection

Leigh W SimmonsCentre for Evolutionary Biology, University of Western Australia

“…… [sexual selection] depends, not on a struggle for existence in relation to other organic beings or to external conditions, but on a struggle between the individuals of one sex, generally the males, for the possession of the other sex. The result is not death to the unsuccessful competitor, but few or no offspring.” (chapter iv)

The Origin of Species, 1859

The Decent of Man and Selection in Relation to Sex, Darwin 1871

Sperm Competition and its Evolutionary Consequences in the Insects, Parker 1970

• behaviour

• morphology • physiology

Sperm Competition and its Evolutionary Consequences in the Insects, Parker 1970

70’s 80’s 90’s 00’s

Num

ber o

f pub

licat

ions

Year

100

200

300

• ISI July 2009

Sperm displacement and optimal copula duration in the yellow dung fly, Scatophaga stercoraria

• Behaviour

• Image from Hosken 1999

• Parker 1970

Sperm displacement and optimal copula duration in the yellow dung fly, Scatophaga stercoraria

Small males

Large males

P2

tl* ts*156.5 min

• Evolution, 46, 366

• Behaviour

• Image from Hosken 1999

Sperm displacement and optimal copula duration in the yellow dung fly, Scatophaga stercoraria

• Evolution, 54, 924

-200

20406080

100120140160180200

5 10 15 20 25 30 35 40 45 50 55

Cop

ula

dura

tion

(min

)

Hind tibia length 3

• Behaviour

• Image from Hosken 1999

t*

expenditure ongaining matings

n matings

ejaculate expenditure, x

gain v per matingW = n.v

TotalReproductiveExpenditure

Modelling the ESS ejaculate expenditure

• Parker 1998

• Physiology

Modelling the ESS ejaculate expenditure

0.00 0.20 0.40 0.60 0.80 1.000.00

0.10

0.20

0.30

0.40

0.50

r =1.0

r =0.5

r =0.1

r =0.01

A

ES

S e

jacu

late

exp

endi

ture

Probability of double mating, q • Parker et al 1997

• Physiology

• Physiology

Evolution of ejaculate expenditure

• J. Evol. Biol., 15, 347

-.6

-.4

-.2

0

.2

.4

.6

.8

-1.2 -1 -.75 -.5 -.25 0 .25 .5 .75 1 1.25

Contrasts in sperm competition indexCrinia georgiana

• Physiology

Evolution of ejaculate expenditure

• unpublished

Crinia georgiana1.51.31.10.90.70.50.30.3

1.2

1.4

1.6

1.8

2.0

2.2

log Maximum male density

g

A

• PhysiologySperm competition games between sneaks and guards

ES

S E

jacu

late

exp

endi

ture

0.0 0.2 0.4 0.6 0.8 1.00.0

0.1

0.2

0.3

Probability of a sneak mating

Behavioural biology of onthophagine dung beetles

• Physiology

Testis size variation across alternative mating tactics of dung beetles

• Evolution, 61, 2684

-.2

-.15

-.1

-.05

0

.05

.1

.15

-.4 -.3 -.2 -.1 0 .1 .2 .3 .4

-.4

-.2

0

.2

.4

.6

.8

1

-.6 -.4 -.2 0 .2 .4 .6 .8

X 6

X 60

50

50

Mating Brooding Incubation Maturation

Experimental evolution: breeding regimes

Px3

Mx3

Ne ~ 106

Ne = 100

10 10

• Physiology

Evolution of ejaculate expenditure

• Evolution, 62, 2580

22201816141210864-0.12

-0.08

-0.04

0.00

0.04

0.08

0.12

Generation

Enforced monogamy

Sperm competition

• Physiology

Evolution of ejaculate quality

• Evolution in press

monogamy polygyny-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

Monogamous polygamous

Selection history

Mating regime:

A

Monogamous Polygamous

• % motile• VAP• Longevity

• Morphology

Evolution of male genital morphology among Onthophagines

O. vacca

O. furcusO. sticticus

O. hirtusO. punctatus

O. taurus

• Morphology

Evolution of male genital morphology among Onthophagines

5

1

• Biol. J. Linn. Soc., 93, 257

• Morphology

Evolution of male genital morphology among Onthophagines

• Curr. Biol., 19, 1442

• Morphology

Evolution of male genital morphology among Onthophagines

-4.0 -2.0 0.0 2.0 4.0

0.00

0.50

1.00

Aedeagus shape (PC2)

• Curr. Biol., 19, 1442

• Morphology

Evolution of male genital morphology among Onthophagines

1 2 3 1 2 3-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

Monogamy Polygamy

• Curr. Biol., 19, 1442

• Clarissa House• John Hunt• Paco García-González• Joseph Tomkins• Michael Werner• Phil Byrne• Martin Dziminski• Dale Roberts• Renée Firman• Maxine Beveridge

Acknowledgements

The Environment InstituteWhere ideas grow

Next Seminar: 13 November

Dr Damien Fordham

Predicting ecological turmoil: modelling the dynamics of global change on biodiversity