Interactions Between Populations

Traditional approaches to population interactions have been to consider just the direct pairwise interactions This is simplistic in that the population either interact, or they do not

Interactions Between Populations There are a number of ways in which the populations my impact one another, if they do

Interactions Between Populations Competition ( -, - ) is the most widely interaction we think of Both parties are negatively impacted If the resource is in short supply or high demand, there will be competition If that resource is prey, the form of competition is exploitation competition

Interactions Between Populations Other kinds of competition also occur It may be direct (agonistic) encounters such as allelopathy or territorial defense (interference)

Interactions Between Populations Predation, parasitism, and Batesian mimicry Predation is usually killing another organism, although can you think of exceptions? Parasitism could be considered a form of weak predation

Interactions Between Populations Batesian mimicry and herbivory could also be a form of weak predation

Interactions Between Populations Mutualism, Müllerian mimicry

Interactions Between Populations Commensalism

Interactions Between Populations Amensalism

Interactions Between Populations The interactions among populations can become quite intricate and therefore quite fascinating Consider the case of hummingbirds

Interactions Between Populations Four nectar feeding birds, two species of mites and four species of flowers Three hummingbirds are the primary pollinators Corollas differ in length Strong selection for a bird/ flower relationship

Interactions Between Populations One mite lives in Panterpe and Eugenes, others are specialists Even though suitable habitat is found in other flowers, they are not found there..why? Male mites will actively fight/kill other species of mites within the same flower

Interactions Between Populations Within this 10 species community there is (and please name them) exploitative competition, interference competition, facultative mutualism, parasitism, and commensalism

Interactions Between Populations Symbiosis is a term used for a general relationship in which organisms live together without harming one another Neutralism: who cares Mutualism: Acacia & ants

Interactions Between Populations Ants and many species of caterpillars

Interactions Between Populations Mesquite and root nodules housing bacteria that fix nitrogen Mycorrhizae (fungal roots)

Interactions Between Populations Bioluminescent bacteria and deep sea creatures Photosynthetic algae

Interactions Between Populations It has been hypothesized that endosymbiosis exists The certain of the cell organelles found in higher organisms, particularly chloroplasts and mitochondria, are actually the remnants of symbiotic prokaryotic organisms that have since been permanently incorporated into the eukaryotes

Interactions Between Populations Cattle egrets & oxpeckers

Interactions Between Populations Honey guides and honey badgers

Interactions Between Populations Cleaner wrasse Saber-toothed bleeny

Interactions Between Populations Think about the plant/pollinator relationships that exist Not just large animals, but many insects (e.g. euglossine bees and epiphytic orchids) Up to 23km Outcrossing

Interactions Between Populations Producing nectar and pollen (and fruit) has costs Rewards must be sufficient to allow returns to get them to specialize on a particular species (why?) However, they must be small enough to the animal will travel the distance between plants

Interactions Between Populations Obligate mutualisms are much less common than facultative ones Figs and fig wasps (100s)

Interactions Between Populations

Termites and the protozoans they house in their intestines Next generation of endosymbionts are passed to one another through shared intestinal contents

Interactions Between Populations Commensalism

Interactions Between Populations What about indirect interactions Darwin actually accounted for this E.g. clover, bees, mice and cats

Interactions Between Populations

There is the classical exploitative competition But there is also apparent competition (consider

Interactions Between Populations There are also food-chain mutualisms (aka cascading effects) Aquatic example: plants, minnows, and bass Is it bottom-up or top-down?

Interactions Between Populations Consider three species populations at the same trophic level (horizontal interactions) P1 and P3 are mutualists because they both inhibit P2

Interactions Between Populations A four-species system that results in an indirect mutualism is termed facilitation Consumers indirectly interact as they eat similar, but different prey items (but the plants themselves compete)

Interactions Between Populations Conditions that can lead to CM There is a considerable time lag in the indirect effects of CM

Interactions Between Populations