Species Interactions in Communities

Types of Interactions (type of impact on each species in parentheses) Competition ( - , - ) interspecific vs. intraspecific Predation ( + , - ) carnivory or herbivory Parasitism (+ , - ) Commensalism ( + , 0 ) Mutualism ( + , + )

The Competitive Exclusion Principle If two species, with the same niche (job/role), coexist in the same ecosystem, then one will be excluded from the community due to 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

Impacts of Competition Species B

Resource Partitioning Ruddy turnstone searches under shells and pebbles for small invertebrates Resource Partitioning Herring gull is a tireless scavenger Brown pelican dives for fish, which it locates from the air Avocet sweeps bill through mud and surface water in search of small crustaceans, insects, and seeds Dowitcher probes deeply into mud in search of snails, marine worms, and small crustaceans Black skimmer seizes small fish at water surface Flamingo feeds on minute organisms in mud Figure 4.5: Specialized feeding niches of various bird species in a coastal wetland. This specialization reduces competition and allows sharing of limited resources. Louisiana heron wades into water to seize small fish Oystercatcher feeds on clams, mussels, and other shellfish into which it pries its narrow beak Piping plover feeds on insects and tiny crustaceans on sandy beaches Scaup and other diving ducks feed on mollusks, crustaceans, and aquatic vegetation Knot (sandpiper) picks up worms and small crustaceans left by receding tide Environmental Science: Problems, Concepts, and Solutions. (12th ed.) by G. Tyler Miller, Jr. and Scott Spoolman

Black-throated Green Warbler Yellow-rumped Warbler Resource Partitioning Blakburnian Warbler Black-throated Green Warbler Cape May Warbler Bay-breasted Warbler Yellow-rumped Warbler 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) Environmental Science: Problems, Concepts, and Solutions. (12th ed.) by G. Tyler Miller, Jr. and Scott Spoolman

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. 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. Grey Squirrel Range 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, published records and a few additions up to 1997. Red Squirrel Range

Africanized & European HB Interspecific competition AHB mature faster and are more opportunistic feeders

Spread of AHB (also good example of a nonnative species)

Speaking of Bees… 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…

Impacts of Predation

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!

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.

Commensalism vs. Mutualism How do you decide?

Shark & Remora Commensalism or mutualism? Depends… If remora gets transport, protection and scraps and shark nothing ( +, 0 ) If shark has parasites removed by remora ( +, + )

Oak & Mycorrhizae Fungi Mutualism Oak tree provides sugars for fungi Fungi absorbs moisture and nutrients for tree

Lichen (algae & fungus) Tricky? Mutualism (self) Commensalism (with living tree)

Eastern Lamp Mussel & Largemouth Bass Commensalism: Glochidia (larvae) live on fish gills for about a month…

Speaking of Eastern Lamp Mussels… Carnivory predation by herons

More on Eastern Lamp Mussels… Interspecific competition with Zebra Mussels Zebra Mussels are also nonnatives from Europe that arrived in ship’s ballast tanks

Spread of Zebra Mussels (good example of a accidentally introduced nonnative species)

Epiphytes and Trees Spanish Moss Commensalism Epiphyte roots on bark and has better access to light and water--no harm to tree

More Epiphytes… A common site on tropical or temperate rain forest trees

Humans and E. coli Bacteria Mutualism Humans provide food and shelter (large intestine) for the bacteria E. coli assist in human digestion and provide Vitamin K for host

Quiz Time

You decide! Herbivory predation or Mutualism? MUTUALISM!

You decide! Easy? HERBIVORY PREDATION!

You decide! A hermit crab with an anemone attached to the shell… MUTUALISM!

You decide! A Tobacco Hornworm covered with wasp pupae… ECTOPARASITE! Adult: Carolina Sphinx Moth A Tobacco Hornworm covered with wasp pupae… ECTOPARASITE!

You decide! Mistletoe? ECTOPARASITE!

So…species must: Adapt (in other words, coevolve due to competition, predation, or develop symbiosis) Migrate (run away) Die (go extinct)