Lecture 10- Sex allocation

Question 1

foundational sex ratio theory

Answer 1

idea that the only time fitness between the sexes is equal is when the sex ratio is 50/50, ideas of reproductive value of the sexes needing to balance out

Question 2

local resource enhancement

Answer 2

excess production of one sex being favoured

Question 3

example of local resource enhancement

Answer 3

wild dogs- males help rear offspring more, so producing more (60%) is overall beneficial, the costs and benefits of producing the sexes are not the same

Question 4

what assumptions of the fisher theory are likely to be untrue when sex ratios are unusual

Answer 4

reproductive values of males and females being equal
all relationships being the same- may not be true in haplodiploidy for example

Question 5

eusocial insects- example different pressures towards different sex ratios

Answer 5

queen wants 50/50, workers want 75/25 ratio (more females, as relatedness is higher here)

Question 6

how is local resource competition related to sex allocation

Answer 6

idea of the stay-at-home sex increasing local resource competition vs a dispersing sex- so reproductive benefit is skewed towards the dispersing sex

Question 7

example of local resource competition

Answer 7

primates- 70% male ratio in species where the males disperse significantly more

Question 8

local mate competition examples

Answer 8

seen in species such as parasitic wasps, spiders etc- competition among males in structured populations for mates so more females to offset this- can be as extreme as 99% female

Question 9

Seychelles warbler

Answer 9

has a very changeable sex ratio:
-more males- up to 80%- in low-quality territories so there is more dispersal and LRC decreases
-more females- up to 90%- as they act more as helpers, which acts as local resource enhancement