Biology Reference
In-Depth Information
Badyaev
et al
.'s (2001) data on recently introduced populations of the house finch
provide a stunning example of how selection can rapidly lead to different patterns
of sex ratio adjustment in different populations of the same species. Charnov and
Hannah (2002) use data from an impressive 30 years of commercial catches of Pandalid
shrimp, to show that individuals change their sex-changing strategy in response to the
local age distribution of shrimp. Nothing is known about the physiological or social
mechanisms that shrimp could use to assess this. Burley (1981) was the first to suggest
that mate attractiveness should influence selection on the sex ratio. She obtained the
remarkable result that, in the zebra finch (
Poephila guttata
), the colour of a plastic leg
band placed on males influenced their attractiveness, and that females adjusted their
sex ratio accordingly.
TOPICS FOR DISCUSSION
1.
In honey bees, new colonies are formed by colony fission, where the worker force splits into two
swarms
, one of which is headed by a new queen that was produced in that nest, and the other
by the old queen. Would you expect the sex ratio of reproductives to be biased and, if so, why?
2.
Why is there often a female-biased sex ratio in the sexual stage of malaria and related blood
parasites (see Read
et al
., 1995; Reece
et al
., 2008)?
3.
In the parasitoid wasp
N. vitripennis
, the shift in offspring sex ratios with increasing number
of females on a patch is primarily caused by the presence of eggs laid by other females, and,
to a lesser extent, by the presence of other females (Fig. 10.5). Why would this have been
favoured? How would you test your hypothesis?
4.
Sex allocation is often argued to be one of the most successful areas of behavioural ecology.
Discuss why the fit between theory and data could be expected to be especially close in this
area.
5.
Discuss the extent to which the Trivers and Willard hypothesis is supported in ungulates
(Hewison & Gaillard, 1999; Cameron, 2004; Sheldon & West, 2004).
6.
Joan Roughgarden (2004) has argued that traditional Darwinian evolutionary theory has
problems explaining mating systems such as sex change. Do you agree?
7.
Discuss whether temperature-dependent sex determination in reptiles is an 'evolutionary
enigma' (see Shine, 1999; Janzen & Phillips, 2006; Warner & Shine, 2008).
8.
Discuss how meta-analysis can be used to test whether there has been selective reporting of
results (Palmer, 1999; Simmons
et al
., 1999b).
