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Chapter 45 Community Ecology. 45.1 Fighting Foreign Fire Ants Native to Brazil, imported fire ants (Solenopsis invicta) nest in the ground and have painful.

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Presentation on theme: "Chapter 45 Community Ecology. 45.1 Fighting Foreign Fire Ants Native to Brazil, imported fire ants (Solenopsis invicta) nest in the ground and have painful."— Presentation transcript:

1 Chapter 45 Community Ecology

2 45.1 Fighting Foreign Fire Ants Native to Brazil, imported fire ants (Solenopsis invicta) nest in the ground and have painful stings Global trade and shipping brought fire ants to the US and to other countries around the world Fire ants have a negative impact on native species of plants, insects, birds, and other animals

3 Red Imported Fire Ants

4 Communities Species interactions such as competition or predation are one focus of community ecology A community is all the species that live in a region Species interactions and disturbances can shift community structure (types of species and their relative abundances) in small and large ways

5 45.2 Which Factors Shape Community Structure? Community structure refers to the number and relative abundances of species in a habitat Habitat The type of place where a species normally lives Community All species living in a habitat

6 Species Diversity Communities vary in their species diversity Two components of species diversity: Species richness: the number of species Species evenness: the relative abundance of each species

7 Community Structure Many factors influence community structure Abiotic factors such as climate Gradients of topography Species interactions (direct and indirect) Symbiosis refers to direct, long-term interactions: Commensalism: One species benefits and the other is neither benefited nor harmed Mutualism: Both benefit Parasitism: Parasite benefits, host is harmed

8 Table 45-1 p810

9 Commensalism

10 Take-Home Message: What factors affect species in a community? The types and abundances of species in a community are affected by physical factors such as climate and by species interactions. A species can be benefited, harmed, or unaffected by its interaction with another species.

11 45.3 Mutualism Mutualism is a species interaction in which each species benefits by associating with the other Flowering plants and animal pollinators Birds that disperse seeds Lichens, mycorrhizae, and nitrogen-fixing bacteria that help plants obtain nutrients Animals share nutrients with mutualistic microorganisms in their gut Two species may protect one another

12 Obligate Mutualism: Yucca and Moth

13 Mutual Protection

14 Take-Home Message: What are the effects of participating in a mutualism? A mutualism benefits both participants. In some cases, two species form an exclusive partnership. In others, a species provides benefits to, and receives benefits from, multiple species. Participating in a mutualism has both benefits and costs. Selection favors individuals who maximize their benefits while minimizing their costs.

15 45.4 Competitive Interactions Resources are limited; individuals of different species often compete for access to them Interspecific competition hurts both species Competition among individuals of the same species is more intense than interspecific competition

16 The Niche Each species requires specific resources and environmental conditions that we refer to as its ecological niche Both physical (abiotic) and biological (biotic) factors define the niche The more similar the niches of two species are, the more intensely the species will compete

17 Interspecific Competition Interference competition One species actively prevents another from accessing a resource Exploitative competition Species reduce the amount of a resource available to the other by using that resource

18 Interference Competition

19 Effects of Competition Competitive exclusion When two species require the same limited resource to survive or reproduce, the better competitor will drive the less competitive species to extinction in that habitat Competitors can coexist when their resource needs are not exactly the same Competition suppresses growth of both species

20 Competitive Exclusion in Paramecium Stepped Art Time (days) Relative population density P. caudatum alone Time (days) Relative population density P. aurelia alone Time (days) Relative population density Both species together

21 ANIMATED FIGURE: Competitive exclusion To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERECLICK HERE

22 Competing for Pollinators Mimulus Lobelia

23 Resource Partitioning Resource partitioning is an evolutionary process by which species become adapted to use a shared limiting resource in a way that minimizes competition (directional selection) Example: Eight species of woodpecker in Oregon feed on insects and nest in hollow trees, but the details of their foraging behavior and nesting preferences vary

24 Character Displacement Over generations, directional selection leads to character displacement – the range of variation for one or more traits is shifted in a direction that lessens the intensity of competition for a limiting resource Example: Where two species of salamanders coexist, differences in body length becomes more pronounced

25 Character Displacement in Salamanders

26 ANIMATED FIGURE: Hairston's experiment To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERECLICK HERE

27 Take-Home Message: What happens when species compete for resources? In some interactions, one species actively blocks another’s access to a resource. In other interactions, one species is simply better than another at exploiting a shared resource. When two species compete, selection favors individuals whose needs are least like those of the competing species.

28 45.5 Predator–Prey Interactions Predation is an interspecific interaction in which one species (predator) captures, kills, and eats another species (prey) Relative abundances of predators and prey shift over time in response to species interactions and changing environmental conditions

29 Predator Responses to Changes in Prey Density Type I response (passive predators) Number of prey killed depends on prey density Type II response Number of prey killed depends on the predator’s capacity to capture, eat and digest prey Type III response Number of kills increases only when prey density reaches a certain level

30 Responses of Predators to Prey Density

31 A Type 2 Response

32 Figure 45-9b2 p814

33 ANIMATED FIGURE: Predator-prey interactions To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERECLICK HERE

34 Cyclic Changes in Abundance Time lag in predator response to prey density can lead to cyclic changes in abundance When prey density is low, predators decline, prey are safer, prey numbers increase When prey density is high, predator numbers increase, prey numbers decline

35 Canadian Lynx and Snowshoe Hare

36 Predator and Prey

37 Take-Home Message: How do predator and prey populations change over time? Predator populations show three general patterns of response to changes in prey density. Population levels of prey may show recurring oscillations. The numbers in predator and prey populations vary in complex ways that reflect the multiple levels of interaction in a community.

38 45.6 An Evolutionary Arms Race Predators select for better prey defenses, and prey select for more efficient predators Prey defenses include exoskeletons, unpleasant taste, toxic chemicals or stings, and physical adaptations such as camouflage

39 Coevolution of Predators and Prey Predator and prey populations exert selective pressures on one another Genetic traits that help prey escape will increase in frequency Defensive improvements select for a countering improvement in predators Example: Spraying beetles and grasshopper mice

40 Defense and Counter Defense

41 Some Physical Adaptations of Prey Warning coloration Many toxic or unpalatable species have bright colors and patterns that predators learn to avoid Mimicry A harmless animal looks like a dangerous one Camouflage Body shape, color pattern and behavior that make an individual blend in with its surroundings

42 Warning Coloration and Mimicry

43 Camouflage in Prey and Predators

44 Coevolution of Herbivores and Plants With herbivory, an animal feeds on plants Two defenses have evolved in response to herbivory: Some plants withstand and recover quickly from the loss of their parts Some plants have physical deterrents (spines, thorns, tough leaves); or chemical deterrents (secondary metabolites that taste bad or sicken herbivores)

45 Take-Home Message: How do predation and herbivory influence community structure? In any community, predators and prey coevolve, as do plants and the herbivores that feed on them. Defensive adaptations in plants and prey can limit the ability of predators or herbivores to exploit some species in their community.

46 45.7 Parasites and Parasitoids With parasitism, one species (parasite) benefits by feeding on another (host), without immediately killing it Endoparasites such as parasitic roundworms live and feed inside their host An ectoparasite such as a tick feeds while attached to a host’s external surface

47 Endoparasites

48 Ectoparasites

49 Parasite Diversity Parasitism has evolved in members of a diverse variety of groups Bacterial, fungal, protistan, and invertebrate parasites feed on vertebrates Lampreys attach to and feed on other fish Parasitic plants that withdraw nutrients from other plants

50 Dodder: A Parasitic Plant

51 Strangers in the Nest With brood parasitism, one egg-laying species benefits by having another raise its offspring Examples: European cuckoo, cowbird One cowbird can parasitize 30 nests per season, decreasing the reproductive rate of the host species

52 Cowbird with Foster Parent

53 Parasitoids Parasitoids are insects that lay eggs in other insects Their larvae develop in the host’s body, feed on its tissues, and eventually kill it As many as 15 percent of all insects may be parasitoids Example: parasitoid wasps

54 Biological Pest Controls Some parasites and parasitoids are raised commercially for use as biological pest control agents Example: Parasitoid wasps lay eggs in aphids Introducing a species into a community as a biological control has both advantages and risks

55 Biological Pest Control Agent

56 Take-Home Message: Effects of parasites, brood parasites, and parasitoids Parasites reduce the reproductive rate of host individuals by withdrawing nutrients from them. Brood parasites reduce the reproductive rate of hosts by tricking them into caring for young that are not their own. Parasitoids reduce the number of host organisms by preventing reproduction and eventually killing the host.

57 45.8 Ecological Succession Ecological succession is a process in which one array of species replaces another over time It can occur in a barren habitat such as new volcanic land (primary succession) or a disturbed region in which a community previously existed (secondary succession)

58 Pioneer Species Primary succession begins when pioneer species such as lichens and mosses colonize a barren habitat with no soil Pioneer species are opportunistic colonizers of new or newly vacated habitats Pioneers help build and improve soil for later successional species

59 Primary Succession: Alaska’s Glacier Bay

60 ANIMATED FIGURE: Succession To play movie you must be in Slide Show Mode PC Users: Please wait for content to load, then click to play Mac Users: CLICK HERECLICK HERE


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