1. 11 June 2015 Pop-Ecol2108.ppt1 POPULATIONS & CARRYING CAPACITY

2. 11 June 2015 Pop-Ecol2108.ppt2 Population Number of individuals of a species in a defined place and time.

3. Dynamic characteristics of populations Size, number of individuals (N) Density (N/ area) Dispersion, uniform, clumped, random appropriate scale Age distribution, proportions of young, middle-aged, old 11 June 2015 Pop-Ecol2108.ppt3

4. Age Structure 11 June 2015 Pop-Ecol2108.ppt4

5. 11 June 2015 Pop-Ecol2108.ppt5 Changes in populations growth decline May affect size, density, dispersion, age distribution. May be affected by size, density, dispersion, age distribution.

6. Changes in populations ΔN = +B +I –D –E B = births (birth rate) I = immigrants (immigration rate) D = deaths (death rate) E = emigrants (emigration rate) For many [most] natural populations I and E are minimal. 11 June 2015 Pop-Ecol2108.ppt6

7. 11 June 2015 Pop-Ecol2108.ppt7 Population growth B > D Exponential growth, dN/dt = rN N = number, pop.size r = biotic potential, intrinsic rate of increase.

8. 11 June 2015 Pop-Ecol2108.ppt8 Population growth Exponential growth unlimited Instantaneous growth rate dN/dt = rN Unrealistic

9. 11 June 2015 Pop-Ecol2108.ppt9 Population growth Logistic growth, dN/dt = rN (K - N)/ K N = number, pop.size r = biotic potential, intrinsic rate of increase. K = carrying capacity Better represents real populations

10. 11 June 2015 Pop-Ecol2108.ppt10 Population growth Do real populations grow according to the logistic model (equation)? Bacteria Collared turtledove in Gr. Britain

11. 11 June 2015 Pop-Ecol2108.ppt11 Logistic model Logistic model works, to a point. Real organisms have time lags for growth, time to develop eggs, flowers, etc. seasonality, longevity Real populations may exceed carrying capacity. Easter Island Kaibab Deer Pribloff Reindeer

12. 11 June 2015 Pop-Ecol2108.ppt12

13. Pribloff reindeer St. Paul Island 11 June 2015 Pop-Ecol2108.ppt13

14. 11 June 2015 Pop-Ecol2108.ppt14 Logistic model Carrying capacity modeled as a constant. May be variable Interspecific competition Seasonal change resources abundant in summer, rainy season; resources scarce in winter, dry season Events may alter resource availability. storms, mild years, human intervention

15. 11 June 2015 Pop-Ecol2108.ppt15 Population growth, biotic potential, & life history strategy. Various species have various strategies for coping with a variable world.

16. 11 June 2015 Pop-Ecol2108.ppt16 “Natural selection” Phenotypes preserved that maximize fitness  Fitness = Reproductive rate X Survivorship to increase R may decrease S to increase S may decrease R  Given certain quantity of energy = food More smaller eggs  more smaller offspring  Low S for each Fewer larger eggs  few larger offspring  Must increase S for each (or lower fitness)

17. 11 June 2015 Pop-Ecol2108.ppt17 Life History Strategies: Two general types Life History traitr-strategists, Opportunistic K-strategists, Equilibrium OffspringMany, small (high r)Fewer, large (low r) Offspring survivalLowHigh Parental careRareCommon Reproductive ageEarlyLater Reprod. “seasons”1-fewMany HabitatUnstable, temporaryStable, permanent CompetitivenessLowHigh Population regulationDensity independentDensity dependent Population fluctuationIrruptiveStable near K

18. 11 June 2015 Pop-Ecol2108.ppt18 Life History Strategies Examples:  Fly  Robin  Dandelion  Bison  Oak

19. Life History Strategies Survivorship curves “Late loss” (type I curve) K-strategists “Early loss” (type III curve) r-strategists Type II ? 11 June 2015 Pop-Ecol2108.ppt19

20. Cost of parental care Parental care affects survival of parents Normal brood = 5-6 nestlings Enlarged broods = 7-8 nestlings Reduced broods = 3-4 nestlings 11 June 2015 Pop-Ecol2108.ppt20

21. Population Regulation 11 June 2015 Pop-Ecol2108.ppt21 Density-dependent controls  i.e. “biotic components.” Competition Territoriality Stress responses to crowding Disease, parasitism Predation  Wolf, moose

22. Isle Royale N. P. 11 June 2015 Pop-Ecol2108.ppt22

23. 11 June 2015 Pop-Ecol2108.ppt23 Population Regulation Density-independent controls  i.e. “abiotic components.” Drought, extreme temperatures, Light (or lack of), Oxygen (or shortage), etc.