Fundamental question

1. Fundamental question • How do species interact? • Direct and indirect effects

2. Kinds of interactions • Predation +/- • Competition -/- • Parasitism +/- • Mutualism +/+

3. Zebra mussels • Arrived in U.S. 1988: Great Lakes • Native to Caspian and Black sea area of eastern Europe http://www.nuigalway.ie/freshwater/zebra/Europe%20c.jpg

4. How did zebra mussels get here? • Ballast water: what is it? • BW full of marine creatures • Most don’t survive sea crossing; some do • mid-ocean exchange; problems http://invasions.si.edu/nbic/forms/NBICReportingForm.pdf

5. Why are zebra mussels so successful? • Larvae: adapted for long-distance dispersal • Few natural predators in North America • Fish and ducks in native range • Native and introduced fish don’t control them

6. Zebra mussel interactions • Predation +/- • ZM natural predators missing (fish, ducks) • ZM are filter feeders, preying on phytoplankton (bad for phytoplankton; also bad for other phytoplankton feeders  COMPETITION) • BUT: water with ZM much clearer, so more sunlight reaches bottom: good for large, rooted aquatic plants AND also good for some fish that use these plants for cover

7. Other aspects of predation • Carnivore: eat other animals • Herbivore: eat plants • Evolutionary arms race • As predators evolve better ways to catch prey, their prey evolve better defenses • eg: milkweeds and insects that feed on them • Milkweed contains compounds poisonous to most insects • A few insects tolerate milkweed poisons. As a result, they avoid competition from other insects and gain a defense.

9. Parasitism • Also +/- • Parasite weakens host, rarely kills it. WHY? • Endoparasites – internal. eg: tapeworm • Ectoparasites – external. eg: tick

10. Competition • Competition -/- • intraspecific (Same Species) or interspecific (Different Species) • What do individuals compete for? RESOURCES • Eg: food, mates, nesting spots, roosting spots, shelter from predator, sunlight

11. Intraspecific competition • Imagine: • Plants growing in a field • If low density: low seed production. WHY? • If medium density: increasing seed production. • But, high density: at some density, seed production crashes. WHY? • sketch how this would look on a graph

12. Zebra mussel interactions • Interspecific competition • 1000 ZM can settle on a native bivalve, smother it • ZM compete with other phytoplankton eaters • One ZM can filter a liter or more of water a day

13. Interaction benefits both: +/+ Examples? Picture: ants tending aphids. aphids protected from predators, ants get honeydew Mutualism

14. Taking without harming +/0 Common in tropical forests: epiphytes Small plants, live on or attached to trees Mosses, ferns, orchids Commensalism

15. Overall impact of species interactions • Can be hard to estimate • eg: Flowering shrubs live in pine forest. • Both compete for resources such as soil moisture, minerals • BUT the flowers produce nectar that is eaten by insects that prey on other, needle-eating insects. • SO, if removed flowering shrub, would impact on pine be positive or negative??

16. Food web

17. NICHE • = ``ecological niche’’ • Loosely: organism’s role in ecosystem • Includes where it lives, what it eats, what eats it, what organisms it interacts with, even interactions with abiotic components. • NOT synonym for ``habitat’’

18. Differences in niche • Specialists: organisms with a relatively narrow niche. Specific requirements to thrive. • Generalists: organisms with broad tolerances • EXAMPLES??

19. Fundamental vs. Realized niche • A species may be capable of using wider range of resources than it actually does: fundamental niche • Actual role and lifestyle of organism is its realized niche • Q: what leads to smaller realized niche?

20. Limiting resources • Any resource that is scarce (compared to need) • Can restrict ecological niche • Examples: • Mineral content of soil may limit plants • Nest sites may limit breeding population of birds

21. Competition • When 2 or more species overlap in fundamental niche, they compete. • If one species competes for a limiting resource better than the other, it can entirely replace that species in the habitat. • = COMPETITIVE EXCLUSION

22. Resource partitioning • Natural selection may lead species that use the same limiting resources to evolve to LESSEN competition. • = resource partitioning

23. Resource partitioning

25. Fundamental vs realized niche • Brown anole & green anole in FL. • BA is introduced • Initially, large niche overlap • BA outcompetes GA, restricts its niche • Competition is KEY

26. Ecological levels • Individual organism • Population • Species: fundamental unit of biology. A group of interbreeding (or potentially interbreeding) organisms • Community • Ecosystem • Biosphere

27. How do species interact and coexist? How do communities change through time? What determines the makeup of a community (species identity and number)? Community = all populations that live in the same place at the same time Population = all members of one species in one place at one time Community ecology

28. Producers = green plants = autotrophs Consumers = heterotrophs Primary 1° Secondary 2° Tertiary 3° Feeding relationships

29. Trophic levels and energy relationships

30. Key understandings • What is the source of energy in ecosystems? • How is energy transferred between trophic levels? • Rule of thumb: • How is energy lost? • Pyramid of biomass • Pyramid of numbers

31. (sea star) Keystone Species Removing the sea star (the top predator) greatly reduced species diversity. Similar removal of other species had little effect on community structure.

32. Resource Partitioning Closely related warbler species can occupy the same tree if they partition resources.