M 4.21

1. Small Mammals IDQ2. This Friday lab3. Wolves Pt 2 (Q 1-2)4. Competition Principles (cont’d)5. Lab 10B reminder

• Two Thurs seminars remain (10 SP each)• Last owl prowl this Wed 6:30 (30 SP)

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Lab Friday – 1pm

Wolves Pt 2

• Pro-con table to get you warmed up.

• Pt 1 Q 4?

Wolves Pt 2Wolf #21 spent a little over two years with his mother (#9) before venturing out to become the alpha male of another pack. He fathered pups every year from 1998–2004, including 20 pups in 2000. #21 became a legend to “wolf-watchers,” not only because of his size, but also because of his calm and gentle spirit. He was often seen walking away from a kill he had just made so that he could urinate or take a nap. This would allow the younger wolves to take their fill. Alphas typically eat first and will defend their right against others. #21 also was seen playing with the young wolves and letting them climb on top of him, much like a human father might do when wrestling with his young sons.

Rick McIntyre, a biological technician for the Yellowstone Wolf Project, describes #21 the following way: When pups harassed him by biting his tail or ears, #21 would often just walk away; I once saw him cross the road and hide in some bushes to get away from pups that were bothering him. Of course, he also used his great size and strength to benefit his pack. If the younger wolves were attacking an elk, but could not pull it down, #21 would run in and help bring it down (Smith et al. 2005).

#21 died in 2004, which made him an exceptionally long-lived wild wolf. He definitely left a legacy. In 2001, his pack numbered thirty-seven, the largest known wolf pack in history. Many of his pups went on to either join other packs or start other packs.

Part 3/4

• DUE: Parts 1-3 M 4/28• Part 4 for 10SP M 4/28

M 4.21

1. Small Mammals IDQ2. This Friday lab3. Wolves Pt 2 (Q 1-2)4. Competition Principles (cont’d)5. Lab 10B reminder

• Two Thurs seminars remain (10 SP each)• Last owl prowl this Wed 6:30 (30 SP)

Classic competition experiment, Georgy Gause

• Two spp of Paramecium, grown separately,

Paramecium

• BUT, when grown together,

Competitive Exclusion principle

• “No two species can occupy the same niche at the same time.”

• Obvs, this only works if Resources Are Limited

• Next up, models (L-V) of how these principles overlap to predict dynamics. Stay tuned!

• But first, more…

Gause, pt 2

• BUT,– When Gause added bits of crushed glass to the

culture vials, both species survived because they subdivided the habitat (created two separate niches)

• So, important:1. Resource availability2. Resource use3. Niche overlap4. Niche size

It’s all economics (again)

But wait, there’s more.

Of course, resources overlap too, and organisms compete for multiple resources simultaneously.

How would this graph look in 3D?

Do resources overlap?

• Trees and birds?• Water and fish?• Litter and worms?

• Or they can be repellent to each other…

Why do we care?

Biodiversity

• How might competition for resources contribute to biodiversity?

• How are these different:

What if?

• Greater breadth of the resource availability curve.

• Greater stability of the resource availability curve.

• Predation • Greater specialization

Specialization – p. ?

So…

• Most of what we consider “competition theory” is based on the relationship between current morphology and current niche.

• Any problems with this assumption?

So…

• Most of what we consider “competition theory” is based on the relationship between current morphology and current niche.

• Any problems with this assumption?

• It’s easy to study morphology and more difficult to study niche/resource separation. But when we examine morphology alone, there is still clear separation.

The Problem?

• One explanation is that competition has selected for differences in the species. In other words, the species have become more specialized, and thus reduced overlap.

Also,

BUT…

• Morphology is a result of the past. Organisms are not adapted to their present, they are adapted to the ancestors’ present.

• Right??

• Morphology is the “ghost of competition past”

Logistic Growth Equation

• (K-N/K) = proportion of environment still available for habitation

• Whole equation = “change in N is equal to population’s rate of increase multiplied by current population, multiplied by portion of environment still available.”

• (So, as N approaches K, (1-N/K) approaches 0, and multiplication by 0 is 0.)

ΔN = r * N * (K – N)/K

Definitions (lab p. 226)

N1

N2

r1r2K1

K2

• α• Β

Definitions (lab p. 226)

• N1 = size of pop 1

• N2 = size of pop 2

• r1 = growth rate of pop 1

• r2 = growth rate of pop 2

• K1 = carrying capacity for pop 1

• K2 = carrying capacity for pop 2• α = competition coefficient for pop 1• Β = competition coeffic1ent for pop 2

Competition coefficient (α and β)

• “per-capita effect”

• Effect of one individual of one species on one of the other

• Consider a herd of bison vs a colony of prairie dogs

What happens when we add species 2?

• The number of unoccupied spaces available to species 1 get taken up by species 2.

• So, the number of open spaces is now K1 – N1 – αN2

• But, remember, prairie dogs vs bison!

• α would be large (>0) if converting bison space to prairie dog space, but small (<0) if reversed.

By substitution:• Original equation:

ΔN = r * N * (K – N)/K• Substitute:

ΔN1 = r1 * N1 * (K1 – N1 – αN2)/K1

• Works both ways (use β for species 2 coefficient)

• Do Lab CYPs p 221 – 232 for practice, due with plant lab (10B)

Lotka-Volterra Models

• When graphed together, the point at which the lines intersect show the separation between growth and decline (p 232 – 235).

Lab 10B: Competition

• Check pots – no more than HALF of the numbers listed in rows 3 and 5 (final #) for each pot.

• We will continue to provided almost unlimited water.

• Sometime on 5/5, 5/6, or 5/7, do steps 4-6.• Answer all CYPS and Q 1-5 on p 240.