opGenLec2 - Population Genetics Lecture 2.5 Fall 2006...

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Unformatted text preview: Population Genetics Lecture 2.5, Fall 2006 Reading assignment: Chapter 25 & The Florida Panther Study Dr. Charles Maynard 216 Marshall Hall x-6560 [email protected] What We Will Cover Today Review of populations & geography ! Discussion of the Florida Panther project ! Populations and Geography ! Barriers to gene flow Simple distance mountains, deserts, large lakes or oceans ! Genetic barriers polyploidy chromosome translocations & inversions Take selection & drift together and . . . Resulting patterns ! Clines and Ecotypes Cline An environmental gradient (temperature, rainfall, soil pH . . .) and a corresponding phenotypic gradient in a population of plants or animals. ! Where clines have been evaluated by provenance tests (also called commongarden studies), clines are often found to have a genetic basis. ! Cline Translation: Where you have gradual changes in the environment, you will see gradual changes in gene frequency. ! Example: balsam fir on Mt. Washington ! Ecotype A sub-population of a species that occurs in a particular well-defined environment, usually showing better adaptation to that environment than the species as a whole. ! Example: white spruce limestone ecotype ! When do you get an ecotype? Abrupt change in the environment Or some ! Intense selection pressure combination ! Strong barriers to gene flow of these two ! When do you get a cline? Gradual change in the environment ! Weak barriers to gene flow ! Suitable habitat all along the gradient ! The Population Genetics of Range Maps Douglas-fir range map Where would you expect to see clines? Where would you expect to see ecotypes? Where would you expect to see the most genetically variable populations? The least genetically variable? Which populations would you expect to have the most trouble conserving Clinal or Ecotypic variation? Clinal or Ecotypic variation? Acer rubrum Abies concola Clinal or Ecotypic variation? Red Pine: The genetic anomaly Large natural range Lots of natural barriers to gene flow Mixture of large & small populations Considerable range in environments You should expect to see lots of population structure, mostly clinal. But you don't! The species is nearly monomorphic How do you think it got that way? Real-World Application Conservation of Rare & Endangered Species ! Enough about trees & plants, let's talk about an animal species: ! The Florida Panther (Puma concolor coryi) ! The Florida Panther ! Discussion points: What was the pre-introduction situation? What was done? What was the result? What was the result? The unique Florida population was destroyed by contaminating its gene pool! ! The highly inbred and dwindling Florida population was saved by enriching its gene pool! ! Which statement is correct? ! How do you decide? ! Some questions to help you decide when or if to intervene How critical is the situation -- Really ! What caused the genetic isolation? ! Is the isolation due to human activities? ! Or is it of ancient (and presumably natural) origin ! Is the genetic uniqueness due to drift or natural selection? ! Is there one or more closely related populations from which to introduce genes? ! Assuming the decision to introduce has been made, How do you do it sensibly? Genetic Considerations (Remember: we are talking about enriching an existing but inbred population, not replacing a completely extinct Population) ! Pick a nearby population (genetically) ! Don't add so many introductions that you swamp the original population ! 1% is undoubtedly too few 25% is probably too many, especially if you are attempting to preserve its uniqueness 10% feels about right Practical Considerations ! Have you done your homework? What caused the population to decline Habitat loss--forget genetics, spend your money on habitat restoration ! What is the life-history of the species Do you release males or females? Young or adults? Is there unoccupied habitat? What do you think? ! Were they right to introduce Texas genes into the Florida panther? For Next Time: Start reading: Chapter 26: Evolutionary Genetics ! ...
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