Chapters 54 PART 1

Concept 4: Community Ecology – Analyzing the interactions and relationships within and between species and the effects of environmental factors on species diversity and composition. Community Ecology (Ch 54) The difference between a fundamental niche and a realized niche The role of competitive exclusion in interspecific competition The symbiotic relationships of parasitism, mutualism, and commensalism The impact of keystone species on community structure The difference between primary and secondary succession

Review – Define the following! Population Community Ecosystem Biome Biosphere Habitat Niche

Review Population – a group of individuals all of the same species living in the same area Community – a group of populations living in the same area Ecosystem – describes the interrelationships between the organisms in a community and their physical environment Biome – a major ecosystem, classified by the predominant vegetation and characterization of adaptations of organisms to that particular environment Biosphere – composed of all the regions of the earth that contain living things. Habitat – type of place where an organism lives Niche – all biotic and abiotic resources in the environment used by an organism.

Try This What are four factors that may limit the geographic distribution of a species? Give an example of each of the factors.

Try This What are four factors that may limit the geographic distribution of a species? Give an example of each of the factors. - Dispersal: an area may be beyond the dispersal ability of a species - Behaviour and habitat selection: insect larvae may be able to feed on more plants, but females oviposit on a single type of plant - Biotic factors: the presence of predators or competitors may restrict a species’ range - Abiotic factors: climate (sunlight, water, temperature, wind) may determine whether a species can inhabit an area

Community Ecology Community Ecology is concerned with interspecific interactions (relationships between populations of different species). We will look at three types of community interactions: 1. Interspecific Competition – competition between different species for resources 2. Predation – partial or complete consumption of a plant or animal 3. Symbiosis – two species living in close contact

Community Ecology Interspecific Competition Competitive exclusion principle (Gause’s principle) Resource partitioning Character displacement (niche shift) Realized niche Predation True predator ParasiteParasitoid Herbivore Symbiosis Mutualism Commensalism Parasitism

Interspecific Competition How do the following principles relate to each other? What are some examples? Competitive Exclusion Resource Partitioning Character Displacement Fundamental Niche vs Realized Niche

Interspecific Competition Competitive exclusion principle (Gause’s principle) States that no two species can occupy the same niche In other words, if two species are competing for exactly the same resources, one is more likely to be successful Example: Paramecium

Interspecific Competition Resource Partitioning When some species coexist in spite of apparent competition for the same resources These species occupy slightly different niches! Example: five species of warblers coexist in spruce trees by feeding on insects in different regions of the tree and by using different feeding behaviours to obtain the insects

Interspecific Competition Character displacement (niche shift) A result of resource partitioning Selection for characteristics that enable individuals to obtain resources in their partitions more successfully Example: Two similar species of Finches coexist on the same island in the Galapagos; both eat seeds. One has a beak specialized for small seeds, one has a beak specialised for larger seeds

Interspecific Competition Realized Niche In absence of interspecific competition, a species will occupy its fundamental niche In presence of interspecific competition, one or both species may be able to exist by occupying its realized niche, taking out any overlap Example: barnacle species C can experimentally live on the entire intertidal. In the natural environment barnacle species B outcompetes C at the lower tide levels. C will survive in its fundamental niche: the higher tide levels.

Predation How do the following principles relate to each other? What are some examples? True Predator Herbivory Parasite Parasitoid Adaptations Cryptic vs. Warning Colouration Mullerian vs Batesian Mimicry

Predation True Predator Kills and eats an animal Most predators have adaptations such as acute senses, speed, agility, claws, teeth, fangs, stingers, or poison Prey defenses include hiding, fleeing, forming herds or schools, self-defense, and alarm calls Shark preying on seals (BBC) ure=related ure=related

Predation Herbivore Animal that eats plants Includes granivores (eat seeds), grazers (eat grasses), borrowers (eat leaves) Leads to adaptations as well! Ex) plants may produce toxic chemicals - Tannins, nicotine, morphine, the flavours of cinnamon, cloves, peppermint

Predation Parasite Spends most or all of its life living on another organism (the host), obtaining nourishment by feeding on its tissues. Endoparasite: live within their host Ex) tapeworms, malarial protist Ectoparasite: feed on the external surface of their host Ex) mosquitoes, aphids

Predation Parasitoid Special kind of parasite (insects) that lay eggs in or on living hosts. Eggs hatch and larvae feed on body of living host… eventually killing it. Ex) some small wasps Video: National Geographic (2 min) Fungus Video!:

Predation - Adaptations Cryptic colouration, or camouflage, makes predator or prey difficult to spot Ex) fur of snowhare is white in winter, brown in summer Ex) canyon tree frog Warning colouration, or aposematic colouration, warns predators Ex) Black and Yellow bees = DANGER! Ex) Poison dart frog

Predation - Adaptations Mullerian mimicry Several animals, all with the same defense mechanism, share the same colouration Ex) bees, yellow jackets, wasps Batesian mimicry An animal without any special defense mechanism mimics the colouration of one that does Ex) defenseless fly “pretending to be a bee”! Ex) larvae mimicking a poisonous snake

Symbiosis How do the following principles relate to each other? What are some examples? Mutualism Commensalism Parasitism

Symbiosis Mutualism Relationship in which both species benefit (+,+) Ex) lichens: fungi and algae! Ex) clownfish and sea anemones Ex) Ocean sunfish and birds Many have evolved from predator-prey or parasite-host relationships Ex) flowering plants attracting animals to pollinate or disperse seeds

Symbiosis Commensalism Relationship in which one species benefits, while the seond species in neither helped nor harmed (+,0) Ex) birds building nests in trees Ex) egrets gathering around cattle Examples difficult to find in nature

Symbiosis Parasitism Relationship where the parasite benefits, while the host is harmed (+,-) Note: Some Biologists prefer to use the term symbiosis for mutualism or commensualism only.

Coevolution The evolution of one species in response to new adaptations that appear in another species Ex) specific pollinators of specific plants In reality, very hard to find evidence in nature for TRUE coevolution! Why? – Most adaptations are in response to a category of organisms, rather than coupled interaction between just two species. ie) lions have depth perception as an adaptation to hunting many species, not just another! ie) warning colour of tree frogs to alert many predators

Adaptations Although true examples or coevolution is difficult to find, most biologists agree that interspecific interactions lead to evolutionary adaptations through natural selection… Predation and Competition are the key processes in driving community dynamics. Summary of adaptations: Secondary compounds in plants (poisons), camouflage (cryptic colouration), aposematic colouration (warning colouration), Mullerian mimicry, Batesian mimicry, coevolution of pollinators and plants

Try This What kind of mimicry do the following represent? Harmless species resembles a poisonous or distasteful species Mutual imitation by two or more distasteful species

Try This What kind of mimicry do the following represent? Harmless species resembles a poisonous or distasteful species Batesian mimicry Mutual imitation by two or more distasteful species Mullerian mimicry

Try This Two species, A and B, occupy adjoining environmental patches that differ in several abiotic factors. When species A is experimentally removed from a portion of its patch, species B colonizes the vacated area and thrives. When species B is experimentally removed from a portion of its patch, species A does not successfully colonize the area. What might you conclude from the results?

Try This What might you conclude from the results? Species A is limited to its range by abiotic factors, and species B is limited to its range because it cannot compete with species A. Species A is living in its fundamental niche, while species B is living in its realized niche. Species A’s fundamental niche and realized niche are the same.