Nile Perch from Lake Victoria
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Transcript of Nile Perch from Lake Victoria
![Page 1: Nile Perch from Lake Victoria](https://reader030.fdocuments.net/reader030/viewer/2022012906/5681308e550346895d966b74/html5/thumbnails/1.jpg)
Nile Perch from Lake Victoria
![Page 2: Nile Perch from Lake Victoria](https://reader030.fdocuments.net/reader030/viewer/2022012906/5681308e550346895d966b74/html5/thumbnails/2.jpg)
Genetic Diversity
![Page 3: Nile Perch from Lake Victoria](https://reader030.fdocuments.net/reader030/viewer/2022012906/5681308e550346895d966b74/html5/thumbnails/3.jpg)
Fitness
• evolutionary fitness is a measure of the number of offspring an individual produces
![Page 4: Nile Perch from Lake Victoria](https://reader030.fdocuments.net/reader030/viewer/2022012906/5681308e550346895d966b74/html5/thumbnails/4.jpg)
Loss of Fitness
• Another important aspect of polymorphism is that it tends to maintain fitness -
• populations of animals in zoos, which are typically low in genetic diversity, often have low fitness - low fertility and high mortality among offspring
![Page 5: Nile Perch from Lake Victoria](https://reader030.fdocuments.net/reader030/viewer/2022012906/5681308e550346895d966b74/html5/thumbnails/5.jpg)
Fitness of Zoo Animals
![Page 6: Nile Perch from Lake Victoria](https://reader030.fdocuments.net/reader030/viewer/2022012906/5681308e550346895d966b74/html5/thumbnails/6.jpg)
Reasons for Loss of Fitness
1. increased incidence of deleterious recessive homozygous individuals
2. lack of heterosis – heterosis (hybrid vigor) is the phenomenon where heterozygous individuals have higher fitness than do homozygotes - often heterozygotes are more resistant to disease
3. lack of evolutionary potential - with all homozygotes there is lack of variation and all individuals will be susceptible to the same problems
![Page 7: Nile Perch from Lake Victoria](https://reader030.fdocuments.net/reader030/viewer/2022012906/5681308e550346895d966b74/html5/thumbnails/7.jpg)
Inbreeding Depression
• Inbreeding depression is the loss of fitness resulting from the breeding of closely related individuals - it occurs due to the three reasons listed before
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Ngorongoro Crater
![Page 9: Nile Perch from Lake Victoria](https://reader030.fdocuments.net/reader030/viewer/2022012906/5681308e550346895d966b74/html5/thumbnails/9.jpg)
Lions at Ngorongoro Crater
![Page 10: Nile Perch from Lake Victoria](https://reader030.fdocuments.net/reader030/viewer/2022012906/5681308e550346895d966b74/html5/thumbnails/10.jpg)
Vipera berus - adder
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Glanville Fritillary Butterfly
![Page 12: Nile Perch from Lake Victoria](https://reader030.fdocuments.net/reader030/viewer/2022012906/5681308e550346895d966b74/html5/thumbnails/12.jpg)
Outbreeding Depression
• The loss of fitness that occurs when distantly related individuals breed –
• This occurs because certain populations may have been selected for traits that are successful in their environment, so that introducing novel traits may reduce fitness for that environment
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![Page 14: Nile Perch from Lake Victoria](https://reader030.fdocuments.net/reader030/viewer/2022012906/5681308e550346895d966b74/html5/thumbnails/14.jpg)
Austrian Ibex – Capra ibex ibex
![Page 15: Nile Perch from Lake Victoria](https://reader030.fdocuments.net/reader030/viewer/2022012906/5681308e550346895d966b74/html5/thumbnails/15.jpg)
Turkish Ibex – Capra ibex aegagrus
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Nubian Ibex – Capra ibex nubiana
![Page 17: Nile Perch from Lake Victoria](https://reader030.fdocuments.net/reader030/viewer/2022012906/5681308e550346895d966b74/html5/thumbnails/17.jpg)
Optimum outbreeding in Japanese Quail
![Page 18: Nile Perch from Lake Victoria](https://reader030.fdocuments.net/reader030/viewer/2022012906/5681308e550346895d966b74/html5/thumbnails/18.jpg)
Fitness
• evolutionary fitness is a measure of the number of offspring an individual produces
![Page 19: Nile Perch from Lake Victoria](https://reader030.fdocuments.net/reader030/viewer/2022012906/5681308e550346895d966b74/html5/thumbnails/19.jpg)
Maintenance of Polymorphism
without natural selection -
• random mating tends to maintain polymorphism – due to the benefits of sexual reproduction – recombination, independent assortment, and crossing over
![Page 20: Nile Perch from Lake Victoria](https://reader030.fdocuments.net/reader030/viewer/2022012906/5681308e550346895d966b74/html5/thumbnails/20.jpg)
Maintenance of Polymorphism
• The effects of nonrandom mating are variable - species may either mate assortatively (like with like) or disassortatively (like with unlike)
• assortative mating results in many homozygous individuals
• disassortative with many polymorphic, heterozygous individuals
![Page 21: Nile Perch from Lake Victoria](https://reader030.fdocuments.net/reader030/viewer/2022012906/5681308e550346895d966b74/html5/thumbnails/21.jpg)
Assortative Mating - Three spined stickleback
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Disassortative Mating – Nonbreeding Ruff
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Disassortative Mating - Breeding male ruff and variations on head pattern
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Maintenance of Polymorphism
• environmental variance - the environment may affect development of different genotypes so that which genotype dominates changes with the environment - if the environment varies or different habitats exist within the species range, then different genotypes will exist
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Backswimmers – winged or wingless forms
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Maintenance of Polymorphism
With Natural Selection
with selection, we would expect the most fit genotype to come to dominate the population, but polymorphism may still occur:
1. selection acts to maintain stable polymorphism so that different genotypes are most fit under different situations
2. fixation of a particular genotype is counteracted by mutation
3. fixation of a particular genotype in one population is counteracted by gene flow from another population
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Polymorphism under selection –in the Grove Snail - Cepaea
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Clines
• in many species, local populations have little variation, but the entire species exhibits much variation as local populations are adapted to different conditions - if these changes in genes change in response to certain environmental variables, we may see a cline - a gradual change along a geographic transect
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Clines with Body Size
• Bergmann's rule - many animals get larger in size as the species range approaches the poles - it is related to ability to keep warm - larger bodies maintain warmth better
• Allen’s Rule – size of extremities decreases towards the poles – heat is lost through things like large ears
![Page 31: Nile Perch from Lake Victoria](https://reader030.fdocuments.net/reader030/viewer/2022012906/5681308e550346895d966b74/html5/thumbnails/31.jpg)
Bergman’s Rule in same aged White-tailed Deer
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Allen’s Rule in Foxes
Arctic Fox Desert (Kit) Fox
![Page 33: Nile Perch from Lake Victoria](https://reader030.fdocuments.net/reader030/viewer/2022012906/5681308e550346895d966b74/html5/thumbnails/33.jpg)
Allen’s Rule in Hares
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Cline in Cyanide Production in White Clover
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Cline incyanideproductionby whiteclover
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Greater Racquet-tailed Drongocline in crest size
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![Page 38: Nile Perch from Lake Victoria](https://reader030.fdocuments.net/reader030/viewer/2022012906/5681308e550346895d966b74/html5/thumbnails/38.jpg)
Reductions in Polymorphism
• Gene Flow - the movement of alleles from one population to another tends to maintain genetic similarity among populations
![Page 39: Nile Perch from Lake Victoria](https://reader030.fdocuments.net/reader030/viewer/2022012906/5681308e550346895d966b74/html5/thumbnails/39.jpg)
African Wild Dog
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Rates of Gene Flow – Ne (effective population size) = 120
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Minimum Viable Population
• The smallest population for a species which can be expected to survive for a long time
• Many factors effect MVP – the study of those factors is often called Population Viability Analysis – or Population Vulnerability Analysis – or PVA
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Factors that make populations vulnerable to extinction
• Environmental fluctuations
• Catastrophes
• Demographic uncertainties
• Genetic problems
• Habitat fragmentation
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Environmental Fluctuations
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Kirtland’s Warbler
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Cheetah
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Habitat Fragmentation
• Fragmentation is the transformation of large expanse of habitat into a number of smaller patches of smaller total area isolated from each other by a matrix of habitat unlike the original
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Habitat Fragmentation
Habitat fragmentation occurs due to:
• Natural climatic shifts
• Human caused habitat loss: logging, agriculture, urbanization, dams, road construction, etc.
• Overexploitation of species
• Species introduction
• Secondary effects due to extinctions
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Domesday Book – 1085-86
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Selection from the Domesday Book
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![Page 55: Nile Perch from Lake Victoria](https://reader030.fdocuments.net/reader030/viewer/2022012906/5681308e550346895d966b74/html5/thumbnails/55.jpg)
Factors that make populations vulnerable to extinction
• Environmental fluctuations
• Catastrophes
• Demographic uncertainties
• Genetic problems
• Habitat fragmentation
![Page 56: Nile Perch from Lake Victoria](https://reader030.fdocuments.net/reader030/viewer/2022012906/5681308e550346895d966b74/html5/thumbnails/56.jpg)
Heath Hen – Extinction Vortex
![Page 57: Nile Perch from Lake Victoria](https://reader030.fdocuments.net/reader030/viewer/2022012906/5681308e550346895d966b74/html5/thumbnails/57.jpg)
Minimum Viable Population Size
• Another definition - often defined as 95% probability of 100 year survival, but can also plan for longer survival (500 or 1000 years)
• MVP is usually determined by modeling
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Forces which may cause extinction
1) deterministic - something essential is removed (habitat loss) or something lethal is added (pollutant, disease, introduced species) - presumably we can act to minimize these risks
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Forces which may cause extinction
2) stochastic (random) - environmental, catastrophic, demographic and genetic - this is what we need to worry about and what is hardest to prevent
• environmental randomness effects resources and conditions and we can't do much about it
• catastrophic randomness - floods, fires, hurricanes, volcanoes - can't really prevent but can spread individuals around to minimize the impact
• demographic - just natural random variation in birth and death rates can lead to extinction
• genetic - lack of genetic variability can lead to problems of inbreeding and poor response to diseases and environmental change
![Page 60: Nile Perch from Lake Victoria](https://reader030.fdocuments.net/reader030/viewer/2022012906/5681308e550346895d966b74/html5/thumbnails/60.jpg)
Bighorn Sheep and MVP
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Bighorn Sheep and MVP
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Grizzly Bear and 50/500 Rule
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MVP – 50/500 Rule?
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Reductions in Polymorphism
Reductions in population size can lead to losses of genetic polymorphism
Two special cases of reductions in population size are:
1. A few individuals move to a new area and start a new population that is isolated from other populations – founder effect
2. We can also experience a population bottleneck where a formerly large population is drastically reduced in size
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Founder Effect – Galapagos Tortoise
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Founder effect – Amish and Polydactyly
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Population Bottleneck – Northern Elephant Seal