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by: Dejah Abbott

Ecology BIOL 250

Dejah Abbott
Xavier University
GPA 3.84

Brent Blair

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Brent Blair
Class Notes
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This 5 page Class Notes was uploaded by Dejah Abbott on Thursday October 29, 2015. The Class Notes belongs to BIOL 250 at Xavier University taught by Brent Blair in Fall. Since its upload, it has received 25 views. For similar materials see /class/231002/biol-250-xavier-university in Biology at Xavier University.

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Date Created: 10/29/15
Lecture 13 Parasitism Herbivory and Predation Today s Outline 0 Parasitism 0 Model behavior Announcements O Predator Satiation ORefuges O Predator strategies 0 Prey Strategies 0 Herbivory A n ty Introduction Exploitation Interaction between populations that enhances fitness of one individual While reducing fitness of the exploited individual Predators consume other organisms Parasites live on host tissue and reduce host tness but do not generally kill the host Parasitoid is an insect larva that consumes the host Pathogens induce disease c Oak bullet gall d Goldenrod ball gall Parasitism Egg of horse bot fly Last sta e larvae of attached to host39s hair g Adult horse bot y horse bot fly Horse Bot Fly Predation Model Behavior IO ILAWAEI hit your ADULT FLV middle Io Inn mmquot IUIAL STAG AWL FLV live 1 to 10th and lonupu no Host exponential growth often opposed by exploitation Host reproduction immediately translated into destruction by predator Increased predation more predators More predators higher exploitation rate Larger predator population eventually reduces host population in turn reducing predator population Model Behavior D D Typel e a Three types of funct1onal 3 1 a 3 Q I CSpOIlSC CUI VCS 52 Q m s E 92 Q O Q a D O 93 E E Type II 3 2 E g 8 if b a Q Q 5 6 922 1 E s 5 CL Type III Prey density Prey density C Model Behavior Type II 00 O N U I N o 0 L O l Uquot l l l l l l l l 50 100 150 200 250 300 350 400 Rodent density in autumn Individualsha O Autumn Winter predation by weasels as percent of autumn density of rodents a i 0 b i n 4313ub r JrI3 Predator Satiation gt by an Australian Tree lt 500 400 m g 300 I 200 100 39 I I I I o l I l l I i l 500 1 000 1 500 2000 Density of Microtus spp individualskmz a Predator Satiation protection in numbers Living in a large group provides protection Predator s response to increased prey density Prey consumed X Predators Prey Consumed Predator Area Area Wide variety of organisms employ predator satiation defense Prey can reduce individual probability of being eaten by living in dense populations Predator Satiation by Periodical Cicadasquotlt Synchronous Widespread seed and fruit production is known as masting Janzen proposed that seed predation is a major selective force favoring mast crop production 0 Dowd and Gill determined synchronous seed dispersal by Eucalyptus reduces losses of seeds to ants Periodical cicadas Magicicada spp emerge as adults every 1317 years Densities can approach 4X106 ind ha Williams estimated 1063000 cicadas emerged from 16 ha study site 50 emerged during four consecutive nights Losses to birds was only 15 of production Lecture 21 Island Biogeography and l39letapopulations M w 0 Logistic growth reconsidered 0 Island Biogeography OThe Meiapopulation O Colonization and Extinction 0 Patch size and isolation 0 Habitat heterogeneity O The rescue effect Island Biogeography Logistic Population GI OWth reconsidered What may make population variability more likely Environmental stochasticity Small populations but why Less genetic diversity Closer to minimum population where alee effect becomes important Island Biogeography Island Biogeography The number of different species found on different islands depend on the size ofthe island in a New Guinea 5quot m 0 ix Log bird species richness Island Biogeography Islands are similar to isolated patches on the landscape Ecologists now apply this concept to terrestrial habitats Refined Definition The number of species established on an island represents a dynamic equilibrium between the immigration of new colonizing species and the extinction of previously established ones Island Biogeography MacArthur and Wilson Model explaining patterns of species diversity on islands as result of immigration and extinction rates Reasoned rates of immigration would be highest on new island with no organisms As species began to accumulate rate of immigration would decline since fewer arrivals would be new species Predicted rate of extinction would rise with increasing number of species on an island for three reasons Presence of more species creates a larger pool of potential extmctlons As number of species increases population size of each must diminish As number of species increases potential for competitive interactions between species will increase Island Biogeography Island Biogeography Butter y Populations Point where two lines cross predicts the number of species that will occur on an island Proposed rates of extinction on islands would be determined mainly by island size LG near islands will support highest number SM far islands will support lowest number SM near and LG far will support intermediate number Metapopulations Ecologists have proposed landscape structure can in uence movement of organisms between potentially suitable habitats Metapopulations Populations of many species occur in spatially isolated patches with signi cant exchange of individuals Rate of movement of individuals between subpopulations can affect species persistence in a landscape Hanskz er al found butter y density significantly affected by size and isolation of habitat patches Population size within patch increased with patch area Population density decreased as patch area increased Isolated patches had lower butter y densities Population partially maintained by immigration Metapopulations Metapopulations Four traits of metapopulations The suitable habitat occurs in discrete patches that may be occupied by local breeding populations Even the largest populations have a significant risk of extinction Habitat patches must not be too isolated to prevent recolonization after local extinction The dynamics of local populations are not synchronized Metapopulation checkerspot butter y General defini ion Metapopulation population divided into discrete subpopulations linked by movement of individuals Subpopuation because the landscape is heterogeneous individuals can form smaller groups with much less interaction between groups han if the habitat were homogeneous 10000 5000 3000 1000 I 39 quoti 500 aoo quot Population size 100 50 30 10 1 l l l l l l l l i i l 60 62 64 66 68 70 72 74 76 78 80 82 84 86 Year 11 Patch Area and Isolation Habitat heterogeneity Skipper butterfly Hesperia comma iOO Primarily found in large patches 90 50 10 Habitat variability may be important in a changing environment Why might this be critical e g An extremely dry or wet year may mean that the ideal habitat of an organism changes Patch area ha Bush crickets prefer grasslands during normal years but prefer sandier areas in wet years 0 0001 of i 110 100 Sandy areas not always available in smaller patches Distance from nearest p0puiated patch km b war 131 0 32015 PawLuv Conner in cumming us Bunmrnivi Cumin Habitat heterogeneity The Rescue Effect 20 Rescue effect An increase in population size and a decrease in the risk 100 of extinction brought about by an increase of 3 immi ration into a o ulation an CVStdevmean g p p g 80 Mamland1sland metapopulatlon structure 5 Single habitat is the dominant source of immigrants g 60 quot Many nonisland populations have a similar structure 0 l 40 Metapopulatlons s1m11ar to the mamland1sland idea but emphasizes quality rather than size of 20 l l l l l l l l l l l 0 so 100 150 200 250 300 Habitat heterogeneity Source and Sink habitats Metapopulation a review Checkered white butter y Source population lives in unique habitat on vegetation that grows on dredge tailings this area is the only region of its range where it can overwinter successfully e 36 Copyright Benjamin Cummings an imprint of Addison Wesley39Longman


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