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University of Toronto Scarborough
Biological Sciences
Rudy Boonstra

Lecture 6Biological impacts onClimate ChangeBiological Impacts of Climate Change Species Distribution Factors to consider 1 Niche 2 Tolerances 3 Geographic Ranges 4 Ecotypes 5 Community Organization 6 Extinction Processes 7 Species Ranges from Refugiato Habitat Expansion Niche Hypothetical diagram of the niche space of two species S1 and S2 Only two environmental variables are used for illustration but thisapproach could be extended to three variables to define volume or to four or more variables to define a hyper volume This has been called the fundamental niche of a species The niche space of species may overlap to a greater or lesser extentAreas that overlapcompetitionTemperature and Moisture are key factors Tolerances Hypothetical comparison of the tolerance of an organism and the temperature or moisture ranges of the microclimate where it livesThe tolerance zone is measured for the stage of the life cycle that is most sensitive to temperature or moisture and is subdivided into two zones the optimal zone dark blue and the marginal zone light blueThis organism can live in A and in B but not C or D This can be applied to any environmental factorShelfords law The distribution of a species will be controlled by the environmental factor for which the organism has the narrowest range of toleranceEx blue grey bill can eat food from 2 mm12 mmbut is best at 35mm due to less predationGeographical Ranges Natural distribution limits dashed line and calculated climatic limits solid line of the loblolly pine in SE USAWinter temperature and rainfall set the northern and western limits of this pine The rate of water uptake in roots decreases rapidly at low temperatures and this would accentuate winter drought in northerly areasThus this pine can not move unless climate changesand this will move the range limitsExample 2 Winter distribution of the Eastern Phoebesit and eat predatorLimited by temperature has an isotherm barrier of4 C creating range boundary Example 3 Winter distribution of the Aedes aegypti the carrier of yellow fever The 10C degree isotherm is the lower limit for adults and larvae but not always for eggs Eggs can overwinter at lower temperaturesIf this isotherm barrier range goes up higher we could have Lime disease dangae fever Ecotype a subspecies or race that is especially adapted genetically to a particular set of environmental conditions Example races of a perennial plantyarrowwere collected at various spots taken to a common garden best environment for growing plants and grown The major attributes of these races were retained when grown under uniform conditions Higher elevation plants that were smaller stayed small after being grown in common gardenLoss of genetic diversity with climate change ecotypes factor Each rectangular panel represents the same geographical space over timeDifferent colours represent different ecotypesAs climate changes the species may not be able to live in all suitable areas because of inability to migrateAs a consequence of climatic change the species potential range shifts northeastwards with time losing ecotypes because organisms cant adapt fast enough Area occupied by species decreases because the rate at which the species population is able to migrate is less than the rate required to maintain equilibrium with the rapidly changing climate Models of Community OrganizationA Fundamental unit concept of a plant community ClementsTansley B Individualistic continuum model Whittaker C Resource partitioned continuum model strong competition D Resource partitioned continuum model with several strata eg trees shrubs and herbs QuestionWhich one is right A is definitely wrong from examples 1 and 2 And D looks like the best estimate for reality
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