No of seeds per flower

1. Spartina alterniflora(Smooth cordgrass), native to the Altlantic coast, now invading Pacific coast estuaries:

3. Isolated Meadow No of individuals with seed No of seeds per flower Different sites Different sites Seed set of plants at the low density leading edge of the invasion was reduced to 1/8th compared to pantswithin meadows of Spartina. From Davis et al. 2004

4. The Mauna Kea silversword is extremely rare and cannot self.

5. Silversword Alliance: 30 species in 3 genera, the descendents of possibly a single introduction.

6. Haleakakasilversword:near extinction • good to eat • do not self • recruit rarely

7. By 1970’s, only 42 individual plants were left, clinging on to cliffs and rock faces inaccessible to sheep.

8. Animals grouping together to lower the risk of predation

9. Big horn sheep have a very high predation risk from mountain lion, bobcat, coyote. They spend a large amount of time and energy on looking out for predators. From Mooring et al. 2004

10. The African hunting dog, Africa’s most endangered large carnivore: Adults live in same-sex packs of up to six individuals. When they meet a group of opposite sex, they form a new group. However, only one pair will breed, the others hunt and look after the young.

11. The biology behind the Allee effect: • 1) Reproductive challenges at low density: • Males and females rarely meet (compatible male and female gametes rarely meet); • Inbreeding depression; • 2) Increased predation risk at low density: • Losing the safety of numbers. • 3) Cooperative behavior suffers at low density: • 10 eyes see more than 2; • No one to hunt with; • No one to look after the kids (cooperative breeding).

12. dN Ndt 0 N Allee Effect: When populations at low numbers have a positive relationship between per-capita population growth rate and population density. Warder. C. Allee (1885 – 1955)

13. dN Ndt 0 N Allee Effect:

14. Identify on this graph all population sizes where the population growth rate is zero. • Identify the range of population sizes over which population size increases. • Identify the range of population sizes over which population size decreases. dN dt 0 N

15. dN dt Stability analysis for model with Allee effect: 0 N K0 K

16. Plug & Play • Excel Worksheets: • Allee Effect

17. Definition of an “unstable equilibrium” in population dynamics: An equilibrium N* is said to be locally unstable if population sizes that are slightly smaller or slightly bigger move away from the equilibrium state.

18. dN dt Stable equilibrium Stable equilibrium Stability analysis for model with Allee effect: 0 N Unstable equilibrium

19. dN Ndt dN Ndt 1) No density-dependence: 0 N 2) Negative density-dependence: (often created by competition) 0 N Density-dependence: = the way that per-capita population growth rates depend on population sizes:

20. dN Ndt Density-dependence: = the way that per-capita population growth rates depend on population sizes: 3) Positive density-dependence: (often created by cooperation) 0 N

21. The sad story of the Passenger Pigeon: In the early 18th century, at an estimated 3 – 5 billion, the passenger pigeon may have been the most abundant bird species that ever lived. By the late 1889 there were no more free-living flocks. The last known individual, a female called Martha, died in 1914 in the Cincinnati Zoo.

22. The sad story of the Passenger Pigeon: The last known individual of the passenger pigeon species was "Martha" (named after Martha Washington). She died at the Cincinnati Zoological Garden, and was donated to the Smithsonian Institution, where her body was once mounted in a display case with this notation: MARTHA Last of her species, died at 1 p.m.,1 September 1914, age 29, in theCincinnati Zoological Garden.EXTINCT