Assignment 1

1. Assignment 1 Table of data available on website- Katie emailed a few clarifications/errors Draft due in drop box today-- no big deal if a few days late email Katie if need more time Annotated drafts will be staggered in their return as large number of these for Katie to handle

2. Population Ecology & Interspecific Competition • Population Ecology • Density-dependent effects on growth, birth and death rates • Life history patterns • Interspecific Competition • Ecological effects of competition • Evolutionary effects of competition • Competition and community structure

3. Exponential & Logistic Population Growth r = b-d intrinsic rate of natural increase

4. Density-dependent birth and death rates determine K, the carrying capacity

5. Sea otters well below carrying capacity in a resource-rich environment:Washington coast: N =600; increasing 10%/yr (K approx. 2400)

6. “Sigmoidal” or Logistic Population Growth is expected in most populations: changes in density-dependent mortality or fecundity occur as population nears K Bacterium Lactobacillus annual Juncus modules Willow tree Salix What determines an organism’s K? (population density) Is this K variable from place to place & year to year?

7. Net recruitment curves as density increases towards K- defined as births - deaths brown trout fruit flies, experimental herring What population size allows greatest harvesting rate?

8. Life History Theory:-natural selection on “life history traits” influencing demographic variables-optimal life history evolves in ecological arena of selective pressures • How long to live? (lifespan) • Single bout of reproduction or many? (iteroparity/semelparity) • Many flimsy offspring or a few robust ones? (allocation of reproductive effort into offspring size vs. litter size) • Reproduce early or wait (and die later)? (age at first reproduction) • How large to grow vs. allocate resources to reproduction? (allocation of resources into growth vs. reproduction)

9. Trade-off between growth and reproductionDouglas fir Pseudotsuga ragwort Senecio

10. Trade-off between offspring number vs. size in the Australian snake Austrelaps ramsayi Size of offspring (snout-vent length) vs. Litter size Residual refers to statistically controlling for effect of maternal size

11. r-selection where adult survivorship low or uncertainK-selection when adult survivorship highAllometry of life history traits: + correlations with body sizelifespan, survivorship (but variable!) age at first reproduction, iteroparity offspring size - correlations with body size (lower value with increasing body size)litter size, fecundityHumans as relatively r-selected: does high reproductive rate, relative to other great apes, indicate evolutionary history of relatively high mortality?

12. Large organisms (trees) in K-selected habitats:a) iteroparous & low reproductive allocationb) large offspringc) delayed reproduction and long lifespans

13. Interspecific Competition • Occurs when individuals of one species suffer reduction in fecundity, survivorship or growth because of exploitation of resources or interference by another species • Therefore, these interactions affect population dynamics • …and affect species distributions and evolution • Therefore, competition influences the species composition of biological communities • Competition in practice can have less impact than its potential • Use of similar resources does not indicate competition is occurring, as resources may not be limiting to populations

14. Competitive exclusion in laboratory populations of two diatom species Synedra outcompetes Asterionella even when starting population is smaller Synedra Asterionella

15. Sympatry Allopatry Why are Dolly Varden charr found at higher altitudes in Japanese streams compared than White-spotted charr?Interference competition mediated by temperature-dependent aggressive behavior… but no evidence for dominance of DV charr at hi elevations (low temperature streams)Fundamental niche larger than realized niche: expanded range where only one species

16. Exploitative competition in Rocky Mountain Bombus:- when sympatric, specialize on preferred flower species- preference determined by feeding efficiency, matching proboscis length- the “realized niche” are the resources & conditions for a population to exist, grow and reproduce in presence of competing population

17. Niche partitioning between diatoms where Si or P limited resource

18. Most interspecific competition is asymmetric: intertidal barnacles …Balanaus outcompetes Chthamalus except in high dessication zone

19. Experimental removal of orange-crowned warblers resulted in 129% increase in Virginia warbler nestlings; and 78% reciprocally- hypothesized due to improved feeding efficiency …but instead due to preferred nest site competition and reduced predation

20. “Diffuse competition”between “guilds” of similar species with overlapping diet: - overlap in seed size use was experimentally demonstrated to constrain relative abundances (American SW desert)

21. Asymmetric & diffuse competition among Bornean frugivores

22. The Competitive Exclusion Principle • Coexistence of species in a stable environment depends on differences in their realized niches • Without such differentiation, one species will exclude the other • Pattern not always linked to process: Different niches does not necessarily imply past or present competition • (species may differ from other evolutionary causes) • Close competitors may coexist because environmental disturbance rarely allows competitive exclusion • Disregard the Lotka-Volterra competition equations as they make simplistic assumptions about individual and environmental homogeneity, … but these indicate that coexistence possible when niches vary

23. Poorer competitors but better colonizers The sea palm Postelsia colonizes gaps in mussel beds, and coexists by ephemeral occupation of these patches- but coexist only if high rates of gap formation

24. First come, first served Early germinating and growing plants% Bromus depends on when germinatesPhysa snails reproduce earlier and survive better in ephemeral ponds than superior competitor Lymnaea

25. Aggregated distributions can deflect superior species towards intraspecific competition Experimental plantings from seedsin different mixtures of 3-4 coexisting annual plant speciesThree competitive inferiors grew better when aggregated than randomly planted…but competitively superior Stellaria plants grew less well when seeds were aggregatedillustrates coexistence in heterogeneous environments

26. Distribution of 3 Herpestes species Character displacement: evidence of the “ghost of competition past”-competitive release on islandsmale & female Indian mongoose canine size(H. javanicus) H.j. H.e.

27. Character displacement: Stickleback fish in freshwater lakes (British Columbia) - if two species, feeding apparatus morphology diverges

28. Species “packing” in communities structured by competition: Phytoplankton diversity associated with number of limiting resources (nitrogen, phosphorus, silicon & light) n=221 samples from 3 Wyoming lakes Species diversity increased with no. resources limiting growth

29. Evolutionary Effects of interspecific competitionLimiting similarity: how differentiated must niches be to allow coexistence? - note: selection favors individuals with less overlap with competing species- coexistence easier when individuals compete more with conspecificsd>w, narrow niches & little competition d<<w, wide overlapping niches & high competition