Offspring Number Versus Size

1. BIOL 3240 Plant and Animal Ecology – Life Histories Offspring Number Versus Size • ___________________: If organisms use energy for one function such as growth, the amount of energy available for other functions is reduced. • Leads to trade-offs between functions such as…

2. BIOL 3240 Plant and Animal Ecology – Life Histories Egg Size and Number in Fish • _____ show more variation in life-history than any other group of animals. • Turner and Trexler found darter populations that produce many small eggs showed less difference in allelic frequencies than populations producing fewer, larger eggs. • Proposed larvae from larger eggs hatch earlier, feed earlier, do not drift as far, and thus do not disperse great distances. • Greater isolation leads to rapid gene differentiation.

3. BIOL 3240 Plant and Animal Ecology – Life Histories Seed Size and Number in Plants • Many families produce small number of larger seeds.

4. BIOL 3240 Plant and Animal Ecology – Life Histories Seed Size and Number in Plants • Westoby et al. recognized four plant forms: • _______________: Grass and grass-like plants. • _______________: Herbaceous, non-graminoids. • _______________: Woody thickening of tissues. • _______________: Climbing plants and vines. • Woody plant and climbers produced 10x the mass of seeds than either graminoids or forbs.

5. BIOL 3240 Plant and Animal Ecology – Life Histories Seed Size and Number in Plants • Westoby et al. recognized six seed dispersal strategies: • ___________: No specialized structures. • ___________: Hooks, spines, or barbs. • ___________: Wings, hair, (resistance structures). • ___________: Oil surface coating (elaisome). • ___________: Fleshy coating (aril). • ___________: Gathered, stored in caches.

6. BIOL 3240 Plant and Animal Ecology – Life Histories Seed Size and Number in Plants • Small plants producing large number of small seeds appear to have an advantage in… • Plants producing large seeds are constrained to producing fewer seedlings more capable of surviving environmental hazards.

7. BIOL 3240 Plant and Animal Ecology – Life Histories Seed Size and Number in Plants • Jakobsson and Eriksson found seed size variation explained many differences in recruitment success.

8. BIOL 3240 Plant and Animal Ecology – Life Histories Seed Size and Number in Plants • Seiwa and Kikuzana found larger seeds produced taller seedlings. • Energy reserve boosts seedling growth. • Rapid growth helps seedling penetrate thick litter layer.

9. BIOL 3240 Plant and Animal Ecology – Life Histories Adult Survival and Reproductive Allocation • Shine and Charnov pointed out vertebrate energy budgets are different before and after sexual maturity. • Before - • After - • Increased reproduction rate.

10. BIOL 3240 Plant and Animal Ecology – Life Histories Life History Variation Among Species • Gunderson found clear relationship between adult fish mortality and age of reproductive maturity. • Species with higher mortality show…

11. BIOL 3240 Plant and Animal Ecology – Life Histories Life History Variation Within Species • Bertschy and Fox studied the influence of adult survival on pumpkinseed sunfish life histories. • Findings supported theory that when adult survival is lower relative to juvenile survival, natural selection will…

12. BIOL 3240 Plant and Animal Ecology – Life Histories Life History Classification • MacArthur and Wilson • ______________(per capita rate of increase) • Characteristic high population growth rate. • ______________(carrying capacity) • Characteristic efficient resource use. • Pianka: r and K are ends of a continuum, while most organisms are in-between. • r selection: • K selection:

13. BIOL 3240 Plant and Animal Ecology – Life Histories r and K: Fundamental Contrasts

14. BIOL 3240 Plant and Animal Ecology – Life Histories Plant Life Histories • Grime proposed two most important variables exerting selective pressures in plants: • Any process limiting plants by destroying biomass. • External constraints limiting rate of dry matter production.

15. BIOL 3240 Plant and Animal Ecology – Life Histories Plant Life Histories • Four Environmental Extremes: • Low Disturbance : Low Stress • Low Disturbance : High Stress • High Disturbance : Low Stress • High Disturbance : High Stress

16. BIOL 3240 Plant and Animal Ecology – Life Histories Plant Life Histories • ____________ (highly disturbed habitats) • Grow rapidly and produce seeds quickly. • ____________(high stress - no disturbance) • Grow slowly - conserve resources. • ____________(low disturbance low stress) • Grow well, but eventually compete with others for resources.

17. BIOL 3240 Plant and Animal Ecology – Life Histories Plant Life Histories

18. BIOL 3240 Plant and Animal Ecology – Life Histories Opportunistic, Equilibrium,and Periodic Life Histories • Winemiller and Rose proposed new classification scheme based on age of reproductive maturity (α), juvenile survivorship (lx) and fecundity (mx). • Opportunistic: low lx – low mx – early α • Equilibrium: high lx – low mx – late α • Periodic: low lx – high mx – late α

19. BIOL 3240 Plant and Animal Ecology – Life Histories Opportunistic, Equilibrium,and Periodic Life Histories

20. BIOL 3240 Plant and Animal Ecology – Life Histories Reproductive Effort, Offspring Size, and Benefit-Cost Ratios • Charnov developed a new approach to life history classification. • Took a few key life history features and converted them to dimensionless numbers. • By removing the influences of time and size, similarities and differences between groups are easier to identify.

21. BIOL 3240 Plant and Animal Ecology – Life Histories Reproductive Effort, Offspring Size, and Benefit-Cost Ratios

22. BIOL 3240 Plant and Animal Ecology – Life Histories Review • Offspring Number Versus Size • Animals • Plants • Adult Survival and Reproductive Allocation • Life History Classification • r - Selected • K - Selected • New Models