Here are a few questions that did not end up on the exam, but should give you an idea of the kinds of
questions that were used:
1. Mertz, from his study of California condor demography, indicated that at low density, and with low
intraspecific competition, these birds might attempt to initiate reproduction at an earlier age (lower ), but
that this change would only accelerate their decline. How did he explain this apparently counter-intuitive
result?
The explanation is that their current demography is leading to population decline. That decline is
due to their adult proportional survivorship being insufficient to maintain an R0 of 1 or more. If
they reproduce a year earlier they shift from pre-reproductive survivorship  to the insufficient p
earlier, and the rate of population decline becomes even more rapid.
2. How would the following changes in life history affect the advantage of iteroparity? Indicate whether
advantage increases or decreases and briefly explain why the change occurs.
a) an increase in the litter size, b – the advantage of iteroparity decreases. With increasing
litter size the difference between iteroparous and semelparous litters represents a smaller
proportional increase for the semelparous species to ‘keep up’.
b) an increase in the age of first reproduction,  - the advantage of iteroparity increases. The
semelparous species reproduces less frequently, but the iteroparous species reproduces annually
once it has reached age .
c) a decrease in pre-reproductive survivorship,  or C – from Cole’s result the required increase
in litter size is P/C. If C is lower then the advantage of iteroparity increases.
d) a decrease in adult annual survivorship, px or P – using the same formula, if P decreases, the
advantage of iteroparity decreases.
3. It has been suggested that Onycophora, a strange animal in its own phylum somewhere on the line of
evolution between annelids and arthropods, could provide a means to test whether there is a “cost to
reproduction”. Here is a little background about the phylum: Females simultaneously brood a number of
offspring (up to about 10) at different stages of their (the offspring) development. The gestation period is
about 7 months. Thus, there are offspring of radically different sizes drawing upon the energy intake and
reserves of the female parent. Formulate two hypotheses that suggest ways in which a cost of reproduction
might be evident in Onycophora, indicating relationships among aspects of reproduction that would
indicate cost.
There should be a tradeoff between offspring size and number. If a female is brooding a larger
number of offspring, even though there are varying ages of offspring in the brood pouch, the
average size should be smaller if there are more there. We assume here that offspring size should be
correlated with offspring success.
There should also be a tradeoff between parental survivorship and offspring biomass/number. If we
follow the survivorship of females with differing numbers of offspring in their brood pouches, we
should find a lower average survivorship (or ex measured from initiation of the experiment) among
females carrying larger numbers of offspring.
Many other such hypotheses could be generated and simply tested by monitoring the Onycophora.
4. Gadgil and Bossert suggested that there are characteristic benefit/cost relationships as functions of
reproductive effort that differ in semelparous and iteroparous species. What specific curves for profit as a
function of reproductive effort predicts iteroparity? What cost curves similarly predict iteroparity? What
explanation(s) of combinations of profit and cost lead to suggestions of semelparity?
Iteroparity is suggested when either (or both) the profit function for the species is convex or the cost
function is concave. When neither of these conditions is seen, then reproduction is predicted to be
semelparous, i.e. cost is convex (unless profit is also convex) or profit is concave (unless cost is also
concave) and other combinations particularly involving linear profit or cost.
5. The basic theory of metapopulation biology that determines an equilibrium fraction of patches occupied
is based on a number of assumptions, some of which are ‘gloriously’ unrealistic. List two of those
assumptions, and why they are unrealistic, i.e. how they are violated by natural populations and in natural
environments.
The most obvious ones are that all ‘islands’ or isolates are equidistant from all others, that habitats
are all identical, and that only occurrence is important, not population size.
Only in systems of no more than four isolates can they be equidistant, and that is too small a
number to be considered a metapopulation. In any larger system there are unequal distances
between component populations in the metapopualtion.
We know that habitat conditions are important and that habitat variation is virtually certain to
occur among geographically scattered isolates, yet it is assumed noty to occur among habitats of
component populations in a theoretical metapopulation according to basic models.
We also know that population size is important in determining the probability of generating
migrants and of local extinction occurring, but population size is not considered in basic
metapopulation models. Demographic and environmental stochasticity make small populations
much more prone to extinction than larger ones.