Figure 4.5: Specialized feeding niches of various bird species in a coastal wetland. This specialization reduces competition and allows sharing of limited resources.
Figure 6.4: Sharing the wealth: resource partitioning of five species of insect-eating warblers in the spruce forests of the U.S. state of Maine. Each species minimizes competition for food with the others by spending at least half its feeding time in a distinct portion (shaded areas) of the spruce trees, and by consuming somewhat different insect species. (After R. H. MacArthur, “ Population Ecology of Some Warblers in Northeastern Coniferous Forests, ” Ecology 36 (1958): 533–536)
Species Interactions in CommunitiesA good look at coevolution at work in our world…
Types of Interactions (type of impact on each species in parentheses)• Competition ( - , - ) – interspecific vs. intraspecific• Predation ( + , - ) – Carnivory (true) or herbivory – Parasitism, pathogens, parasitoids• Commensalism ( + , 0 )• Mutualism ( + , + )• Amensalism ( - , 0 )*Note some texts list parasitism as a separate interaction
The Competitive Exclusion PrincipleIf two species, with the same niche,coexist in the same ecosystem, thenone will be excluded from the niche dueto intense competition: • both species suffer so ( -, - ) • losers usually migrate or die or • this leads to resource partitioning and species assume smaller realized niches since they cannot occupy their full fundamental niches
Purple Martin & Starling • Interspecific competition • Starlings tend to fight off Martins, kill nestlings, and break their eggs
Red & Grey Squirrels • Interspecific competition • The Grey Squirrel (Sciurus carolinensis) was introduced to Britain in about 30 sites between 1876 and 1929. It has easily adapted to parks and gardens replacing the red squirrel.Grey Squirrel Range • The Red Squirrel (Sciurus vulgaris) is native to Britain but its population has declined due to competitive exclusion, disease and the disappearance mature conifer forests in lowland Britain. Maps prepared by the Biological Records Centre, CEH Monks Wood, from records collated by the Mammal Society and others mainly between 1965 and 1993, also including earlier,Red Squirrel Range published records and a few additions up to 1997.
Africanized & European HB • Interspecific competition • AHB mature faster and are more opportunistic feeders
Spread of AHB(also good example of a nonnative species)
Ruddy Resource Partitioning Herring gull turnstone searches is a tireless under shells scavenger and pebbles for small Brown pelican Avocet sweeps bill invertebrates dives for fish, through mud and which it locates surface water in Dowitcher probesBlack skimmer search of small from the air deeply into mud inseizes small fish crustaceans, insects, search of snails,at water surface and seeds marine worms, and small crustaceansFlamingo feeds on Louisiana heron Oystercatcher feeds on Piping ploverminute organisms wades into water clams, mussels, and other feeds on insectsin mud to seize small fish shellfish into which it and tiny pries its narrow beak crustaceans on sandy beaches Scaup and other diving Knot (sandpiper) ducks feed on mollusks, picks up worms crustaceans, and aquatic and small crustaceans vegetation left by receding tide Environmental Science: Problems, Concepts, and Solutions. (12th ed.) by G. Tyler Miller, Jr. and Scott Spoolman
Resource PartitioningBlakburnian Black-throated Cape May Bay-breasted Yellow-rumped Warbler Green Warbler Warbler Warbler Warbler Environmental Science: Problems, Concepts, and Solutions. (12th ed.) by G. Tyler Miller, Jr. and Scott Spoolman
Lion & Zebra • Carnivory predation • Zebra-prey • Lions-predator * While individual zebras are harmed, the prey population benefits by loss of old and sick members
Rough-Skinned Newt &Common Garter Snake • Carnivory predation • Newt-prey – Has genes to produce potent toxins which discourage predation • Snake-predator – Has genes for resistance to newt toxin • Results in an “evolutionary arms race”… coevolution! *see on YouTube
Monarch Butterfly & Milkweed • Herbivory predation • Milkweed-prey (defense) – Latex: A milky white sap that becomes sticky and coagulates when exposed to air. – Cardiac glycoside: To various degrees, it is toxic to herbivores with hearts (birds and mammals). Monarchs and several other arthropods that eat milkweed have a tolerance for cardiac glycosides, although evidently not at the high levels found in some milkweed species. • Butterfly-predator – Monarch larve cut the petiole of the leaf before beginning to eat it. This "leaf-notching" behavior cuts off the supply of latex.
Other forms of predation…• Parasites (endo and ecto) – Live off host, but do not consume large portion• Pathogens – Cause disease – Viruses, bacteria, fungi, protists, some worms• Parasitoids (endo and ecto) – Lay eggs in or on host & larve consume host
Remember those EHBs… • EHB larvae with a parasitic mite on it • Host = EHB • Parasite = mite • Example of ectoparasite
Elk and Liver Fluke • Parasitism • Elk = host • Fluke = parasite • Example of an endoparasite
Liver Fluke Life Cycle• Many endoparasites may have a cyst form or occupy intermediate hosts that they may not harm…
Ammensalism • One species is hurt, but the other does not benefit ( -, 0 ) • No apparent coevolutionary relationship (one way process) • Example: As wild pigs forage, they often disturb the upper layer of soil and many organisms may be taken from their burrows and exposed to predation by the action of the pigs, although the harm that the burrowers suffer does not improve the pigs situation at all.
Black Walnut & Azalea • Example of alleopathy (not in your text) • Black Walnut secretes chemical (juglone) that inhibits growth of other plants like azalea • Could be ammensalism, competition, or avoidance of predation?
So…species must:• Adapt (in other words, coevolve due to competition, predation, or develop symbiosis)• Migrate (run away) or• Die (go extinct)