3030 Assignment

Assignments
BIOL 3030

Assignment - Seminar 12

DUE DATES
Wednesday seminar sections: due Wed April 16, 4:30 PM

Friday Seminar sections: due Thurs April 17, 4:30 PM (Fri is a holiday)
Friday seminars ONLY: assignments can be submitted by email, to: lgosselin@tru.ca (no later than 4:30 PM).
Please note that if you submit your assignment by email, it will be printed out in black and white (no colour) and this printed copy will be marked.

Life history strategies

This assignment is a story of two little fishies.

Two fish species coexist in several lakes in the Yukon Territory, but do not compete for limiting resources. Under ideal conditions, the 2 species have the following life history traits:

- the 2 species have the same R₀ = 1.64;
- species 1 is iteroparous and species 2 is semelparous;
- if left undisturbed (i.e. no predators, diseases, extreme physical changes, etc.) the 2 species have survivorship schedules as shown in the tables below;
- the iteroparous species reproduces for the first time when they are one year old. Then, from that point on, fertility increases each year of their life as the individuals grow older and larger.
- in both species, all reproduction takes place during one brief period of the year and the population counts are made shortly after breeding.

A recent census of the S_x values of these 2 species in 2 lakes in the Yukon revealed the same total population size (448) and same age structure in both lakes (see tables below).

Start by completing the life tables for each species according to the life history traits listed above. The survivorship schedule (l_x) is already given, and the current number of fish in each age class are provided. However, you will have to 'design' the fecundity schedules of your 2 species so that they correspond to the traits listed above.

Age	Species 1: Ofteneis beteri
Age	S_x	l_x
0	160	1
1	112	0.7
2	80	0.5
3	48	0.3
4	32	0.2
5	16	0.1
6	0	0

Age	Species 2: Woncis enufi
Age	S_x	l_x
0	204	1
1	142	0.7
2	102	0.5
3	0	0

What would happen to these 2 species in each of the following lakes?

1. The first lake, lake Bigbite, is inhabited by predators that feed heavily on these 2 fish species, although they primarily feed on larger fish. These predators ignore fish younger than 2 years, as they are too small. However, each year they do kill some of the 2 year old fish, reducing survivorship by 30% of what it would be in the absence of the predator. The predators feed even more heavily on the older fish, decreasing survivorship of the 3 and 4 year olds by 60%, and decreasing survivorship of the 5 year old fish by 80% of what it would be in the absence of the predator.

2. The second lake, lake Steamy, has no predators but is shallower than lake Bigbite. As a result, on particularly hot summers the water of lake Steamy warms up to a point where the embryos are unable to develop normally. When this happens all the embryos of both species die shortly after being spawned, although the older fish are not affected. These unusually warm conditions occur once every 5 years. The rest of the time the summers are cooler and as a result the fish embryos develop and survive "normally". The next hot summer in the region is expected to occur 5 years from now. You will have to think carefully about how to use Populus to find out what happens to the populations in this lake; there is no direct way to tell Populus that the survivorship changes from one year to the other, so you'll have to find a different way (for example, work out population changes over short periods, such as 1 or 2 years at a time, and change the survivorship values as appropriate).

For each lake, which species would be most successful? Also, for each of the 2 lakes, explain why each species would do well or poorly (i.e. relate your predicted outcome to the particular life history traits of the species).
Provide graphs, as needed, to support your conclusions. Also be sure to include life tables listing all the population parameters (vital statistics) for the ideal conditions, as well as modified life tables as appropriate for the 2 lakes.