1. Ch. 5: Population Structure and Changes

2. Plants “Special” High phenotypic plasticity (Done) Indeterminant growth (Done) Clonal growth (Done) Seed dormancy Dana Carvey as the Church Lady

3. Plant Features 4) Seed dormancy Dormancy: arrested growth embryo –Lupinus arcticus (10,000 yr) (arctic lupine) –Lotus (400 yr)

4. Seed dormancy Seed bank: pop’n dormant seeds –In soil

5. Seed dormancy Seed bank (/m 2 ): –Ag fields: 20,000-40,000 –Tropical forest: <1,000 –Subarctic forest: 10-100

6. Seed dormancy Seed bank: population dormant seeds –On plant closed cone pines (ex, knobcone pine) –Serotinous cones (open postfire) Banksia (Australia)

7. Dormancy mechanisms 1) incomplete embryo development

8. Dormancy mechanisms 2) biochemical trigger –environment cue starts germ. –stratification: cold) –sumorization: heat. Some desert annuals. Max. germ.: 50 C, 4 wk

9. Dormancy mechanisms 3) impermeable seed coat/fruit wall –scarification: breaks Sand paper!

10. Dormancy mechanisms Scarification: Fire Ex: chaparral (shrub vegetation: Mediterranean climate) –Pine Hill flannel bush (Fremontodendron decumbens) –Best germ.: 5 min @ 100 C! Another study by Tony Danza!

11. Dormancy mechanisms Scarification: Mechanical abrasion Ex, smoke tree in arroyo (

12. Dormancy mechanisms 4) germination inhibitors (seed coat/fruit wall)

13. Importance of seed banks 1) May differ from vegetation –Ex, African rain forest 147 tree spp. 22 in seed bank (none same as growing)

14. Importance of seed banks 2) Most pop’n: seed bank –Ex, CA annual grassland. –100 grasses/m 2, 30,000 seeds/m 2

15. Importance of seed banks 3) Seed bank genetic reservoir –Differ from

16. Ch. 5: Population Structure and Changes

17. Population Models 1) Simple discrete-time model –N (t) = number now Future time (t+1): N (t+1) =N (t) + B + I - D – E

18. Population Models 1) Simple discrete-time model Usu. ignore I & E

19. Population Models 1) Simple discrete-time model Usu. ignore I & E Important metapopulations ( Ex, Cakile (sea rocket)

20. Population Models Ex, Cakile (sea rocket) summer winter Tony D!

21. Population Models Ex, Cakile (sea rocket) –Beach pop’n “source”, dune “sink” pop’n wintersummer

22. Population Models 1) Simple discrete-time model N t = number now At time (t+1): N (t+1) =N t + B + I - D – E

23. Population Models 2) Continuous time models –b=birth rate –d=death rate –r max =b-d; intrinsic rate of natural increase –Rate pop’n change=dN/dt –dN/dt=Nr max Curve?

24. Population Models 2) Continuous time models –dN/dt=Nr max –Exponential growth. Ideal conditions…

25. Population Models 2) Continuous time models –Limiting –Logistic growth. Pop. max. @ K (carrying capacity):

26. Population Models 2) Continuous time models –Eqn.? Start dN/dt=Nr max –Add “scaling factor” (K-N)/K dN/dt=Nr max (K-N)/K N small, (K-N)/K almost 1 N near K, (K-N)/K very small

27. Population Models Plant Point 1: K based on density Animals: most inds. Plants: hi modular Crowding capacity: combine density