November 17, 2008. Lecture 28 - Introduction to life-tables. Today’s lecture will be heavy on methods, but we will use life tables a lot in the next several lectures. Please read the Kareiva paper for Wednesday. We will discuss this in depth.

Cod, Gadus morhua big, long-lived, but a prolific spawner once it reaches a large size

Heterandria formosa - least killifish (Not in killifish family - it’s a livebearer - Poeciliidae). Arguably, smallest vertebrate in N.A. Very small, relatively small clutch, but rapid time to maturity.

Salvelinus fontinalis, brook trout, also known as speckled trout. Found in marine waters but also in freshwater. Found in L. Michigan.

Note: It’s the exact same lx data, but the m(x) is switched. The l(x)m(x) is the exact same except that more reproduction is taking place later in life. This increases the generation time, and decreases r and λ BUT Ro is unchanged.

Increase m(x) to 5 in year 1. Ro, λ, r all go up. What happens if we increase fecundity just a little bit in early life stages? Increase m(x) to 5 in year 1. Ro, λ, r all go up. Generation time goes down.

What happens if we increase survival in early life stages?

Ro, r, and lambda all go up. Generation time also goes up. What happens if we increase survival in early life stages? Change mortality schedule so that most of the animals die late in life. Ro, r, and lambda all go up. Generation time also goes up.

Sensitivity – change in λ relative to a change in one of the elements of the life-table How much does λ change with an increase (or decrease) in a given element?

Sensitivity appears higher for survival than for fecundity. But wait -- there’s a problem. They are in different units.

On Wednesday, we will discuss the Kareiva paper in depth On Wednesday, we will discuss the Kareiva paper in depth. Please read this. I will be calling on you and expect you to know something about this. This paper examines a very important question -- whether or not removing dams in the Pacific Northwest will result in a positive growth rate for chinook salmon. They used a life-table analysis to approach this question.

Review Questions. A population of Aphredoderus sayanus starts out with 1000 newborn individuals. At age 1, there are 200 animals left, at age 2 there are 100, at age 3 there are 20. At age 4 there are 2. At age 5 they are all dead. Reproduction begins at age 2. Females at age 2 produce an average of 10 eggs. At age 3, they produce 200 eggs. At age 4 they produce 250 eggs. From this data, calculate the life-table including p(x), l(x), m(x), the product of l(x)m(x), Ro, T, r, and λ. Define in words p(x), l(x), m(x), the product of l(x)m(x), Ro, T, r, and λ. Calculate the sensitivity and elasticity that results from a 10% increase to each of the elements in the life-table. Which elements have the biggest effects on λ? Which elements do you think are most likely to be modifiable? Which ones can humans effect by alterations to habitat? Which ones might be capable of responding to selection?

Review Questions (Cont’d.) 1. Book Question: Describe the trade-off between early versus late maturation. Why does this occur? 2. Book Question: Describe the trade-off between egg number and egg size. What are the benefits to having larger eggs?