Population genetic analysis of microsatellite variation of guppies ( Poecilia reticulata ) in Trinidad and Tobago: evidenc...
Outline <ul><li>Introduction </li></ul><ul><ul><li>Review of key terms </li></ul></ul><ul><ul><li>Study Area </li></ul></u...
Key Terms <ul><li>Source and Sink Dynamics </li></ul><ul><li>Founder Events </li></ul><ul><li>Bottlenecks </li></ul>http:/...
Study Area
Poecilia reticulata <ul><li>Ideal for population genetic effects of geographic isolation and small population size </li></...
Hypothesis  <ul><li>Contemporary vs. Long Term Gene flow </li></ul><ul><ul><li>Contemporary: heavily downstream biased </l...
Methods : <ul><li>Collected from four rivers in the Caroni Drainage </li></ul><ul><ul><li>Caura, Lopinot, Guanapo, Aripo <...
Results : <ul><li>There was no evidence of linkage disequilibrium </li></ul><ul><li>Pr36 and 9-1 from the LA showed depart...
Results : <ul><li>Upland populations had high  F ST   (0.443-0.927), which indicates high level of genetic differentiation...
Methods : Long-Term Gene flow <ul><li>MIGRATE was used </li></ul><ul><ul><li>Estimates  M,  which is  m/µ </li></ul></ul><...
Results : Long-Term Gene flow <ul><li>M : </li></ul><ul><ul><li>Migration rates were highly variable ( N e m:  0.093 – 6.6...
Methods : Contemporary Gene flow <ul><li>Contemporary: BAPS  was used </li></ul><ul><ul><li>Detects the levels of admixtur...
Results : Contemporary Gene flow <ul><li>Admixture: </li></ul><ul><ul><li>All lowland populations show considerable admixt...
Results : Contemporary Gene flow <ul><li>Migration: </li></ul><ul><ul><li>Downstream geneflow was greater than upstream mi...
Results : Souce/Sink Status of the Populations <ul><li>Upland populations contribute migrants (source) </li></ul><ul><li>L...
Methods : Long-term N e  in upland and lowland populations <ul><li>MIGRATE was used </li></ul><ul><ul><li>Θ  =  4N e µ </l...
Results : Long-term N e  in upland and lowland populations <ul><li>Θ </li></ul><ul><ul><li>Lowland populations were on ave...
Methods:  -Upland Populations would show evidence of population bottlenecks resulting from extinction-recolonization dynam...
Results : Upland Populations would show evidence of population bottlenecks resulting from extinction-recolonization dynami...
Discussion: Gene Flow and Admixture <ul><ul><li>Highest level of admixture found in the Caura River (the furthest downstre...
Discussion: Bottlenecks <ul><ul><li>Immigration from genetically differentiated populations into the lowland populations c...
Discussion: Admixture <ul><ul><li>Admixed lowland populations may constitute genetically diverse ‘sink ‘ populations with ...
Discussion:  F ST  and  N e <ul><ul><li>Upland populations have small effective population sizes and large  F ST </li></ul...
Favorite Quote <ul><ul><li>‘ The Caroni drainage can be considered as a source-sink metapopulation, with the river furthes...
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Barson et al

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Barson et al

  1. 1. Population genetic analysis of microsatellite variation of guppies ( Poecilia reticulata ) in Trinidad and Tobago: evidence for a dynamic source-sink metapopulation structure, founder events, and population bottlenecks N. J. Barson, J. Cable, C. Van Oosterhout Crystal Meadows
  2. 2. Outline <ul><li>Introduction </li></ul><ul><ul><li>Review of key terms </li></ul></ul><ul><ul><li>Study Area </li></ul></ul><ul><ul><li>Species </li></ul></ul><ul><li>Hypothesis </li></ul><ul><li>Methods </li></ul><ul><li>Results </li></ul><ul><li>Discussion </li></ul><ul><li>Favorite Quote </li></ul>http://www.zoohaussenti.ch/bilder/guppy.JPG http://www.petfrd.com/images/articles/94/4.jpg
  3. 3. Key Terms <ul><li>Source and Sink Dynamics </li></ul><ul><li>Founder Events </li></ul><ul><li>Bottlenecks </li></ul>http://www.petfrd.com/images/articles/94/4.jpg https://courses.washington.edu/fish340/Images/guppies.jpg
  4. 4. Study Area
  5. 5. Poecilia reticulata <ul><li>Ideal for population genetic effects of geographic isolation and small population size </li></ul><ul><ul><li>Wild range: small fragmented headwater streams to deep lowland pools </li></ul></ul><ul><li>Guppy populations </li></ul><ul><li>are highly structured </li></ul><ul><li>and headwater </li></ul><ul><li>populations show signs </li></ul><ul><li>of local inbreeding. </li></ul>http://www.tropicalfishforum.net/photopost/data/500/guppies.jpg
  6. 6. Hypothesis <ul><li>Contemporary vs. Long Term Gene flow </li></ul><ul><ul><li>Contemporary: heavily downstream biased </li></ul></ul><ul><ul><li>Long term: balanced due to upstream movement </li></ul></ul><ul><li>Long-term N e in upland and lowland populations are relatively similar </li></ul><ul><ul><li>Drift plays and important role </li></ul></ul><ul><li>Upland Populations would show evidence of population bottlenecks resulting from extinction-recolonization dynamics </li></ul><ul><li>Small Tobago population shows evidence of a recent founder event </li></ul>
  7. 7. Methods : <ul><li>Collected from four rivers in the Caroni Drainage </li></ul><ul><ul><li>Caura, Lopinot, Guanapo, Aripo </li></ul></ul><ul><li>Two rivers in the Northern Drainage </li></ul><ul><ul><li>Yara and Marianne </li></ul></ul><ul><li>Samples were collected from the Lambeau River in Tobago </li></ul><ul><li>DNA was extracted and microsatellite loci were used </li></ul><ul><li>FSTAT was used to calsulate F ST </li></ul><ul><li>GENEPOP was used to calculate HWE and linkage </li></ul>
  8. 8. Results : <ul><li>There was no evidence of linkage disequilibrium </li></ul><ul><li>Pr36 and 9-1 from the LA showed departure from HWE </li></ul>
  9. 9. Results : <ul><li>Upland populations had high F ST (0.443-0.927), which indicates high level of genetic differentiation and population isolation </li></ul><ul><li>F ST was considerably lower for lowland populations (0.028-0.288) </li></ul>
  10. 10. Methods : Long-Term Gene flow <ul><li>MIGRATE was used </li></ul><ul><ul><li>Estimates M, which is m/µ </li></ul></ul><ul><ul><li>µ= 5x10 -4 </li></ul></ul>http://img267.imageshack.us/i/img6826cn7.jpg/
  11. 11. Results : Long-Term Gene flow <ul><li>M : </li></ul><ul><ul><li>Migration rates were highly variable ( N e m: 0.093 – 6.686) </li></ul></ul><ul><ul><li>There was evidence of unidirectional migration except between the Lopinot and Caura river which was upstream </li></ul></ul>
  12. 12. Methods : Contemporary Gene flow <ul><li>Contemporary: BAPS was used </li></ul><ul><ul><li>Detects the levels of admixture within each individual </li></ul></ul><ul><ul><ul><li>Describe the number of populations </li></ul></ul></ul><ul><ul><ul><li>Admixture analysis on the groups identified from above </li></ul></ul></ul><ul><ul><ul><li>Mixture analysis: estimates the proportion and source of admixture within each individual of a population </li></ul></ul></ul><ul><ul><ul><li>Estimate gene flow for downstream vs. upstream </li></ul></ul></ul><ul><li>Souce/Sink Status of the Populations </li></ul><ul><ul><li>Total immigration – Total emigration </li></ul></ul>http://www.ta-aquaculture.co.uk/Stick_Foods.htm
  13. 13. Results : Contemporary Gene flow <ul><li>Admixture: </li></ul><ul><ul><li>All lowland populations show considerable admixture </li></ul></ul><ul><ul><li>Tended to have more of their genome admixed from tributaries further east (upstream) than further west (downstream) </li></ul></ul>
  14. 14. Results : Contemporary Gene flow <ul><li>Migration: </li></ul><ul><ul><li>Downstream geneflow was greater than upstream migration in all comparisons </li></ul></ul>
  15. 15. Results : Souce/Sink Status of the Populations <ul><li>Upland populations contribute migrants (source) </li></ul><ul><li>Lowland populations net receivers of migrants (sink) </li></ul>
  16. 16. Methods : Long-term N e in upland and lowland populations <ul><li>MIGRATE was used </li></ul><ul><ul><li>Θ = 4N e µ </li></ul></ul><ul><ul><li>µ= 5x10 -4 </li></ul></ul>http://www.ta-aquaculture.co.uk/Stick_Foods.htm
  17. 17. Results : Long-term N e in upland and lowland populations <ul><li>Θ </li></ul><ul><ul><li>Lowland populations were on average twice as large as upland populations </li></ul></ul>
  18. 18. Methods: -Upland Populations would show evidence of population bottlenecks resulting from extinction-recolonization dynamics -Small Tobago population shows evidence of a recent founder event <ul><li>BOTTLENECK was used </li></ul><ul><ul><li>Garza and Williamson’s M- </li></ul></ul><ul><ul><ul><li>Ratio between the number of alleles and the allelic range </li></ul></ul></ul><ul><ul><ul><li>Measure of the ‘fullness’ of the allelic distribution </li></ul></ul></ul><ul><ul><li>Critical M- </li></ul></ul><ul><ul><ul><li>Detects an excess in heterozygosity because allelic diversity declines faster than heterozygosity due to a loss of rare alleles </li></ul></ul></ul>
  19. 19. Results : Upland Populations would show evidence of population bottlenecks resulting from extinction-recolonization dynamics <ul><li>No evidence for a recent bottleneck in any lowland or upland population in the Caroni Drainage </li></ul><ul><li>Populations from the Northern Drainage showed evidence of a population bottleneck </li></ul><ul><ul><li>Yarra: P =0.055 and Marianne: P =0.020 </li></ul></ul><ul><li>The Tobago population showed clear signs of a bottleneck or founder event </li></ul><ul><ul><li>M = 0.324, M crit = 0.761; P = 0.000001 </li></ul></ul>
  20. 20. Discussion: Gene Flow and Admixture <ul><ul><li>Highest level of admixture found in the Caura River (the furthest downstream population) </li></ul></ul><ul><ul><li>Caura constitutes a ‘super sink’ population </li></ul></ul><ul><ul><li>Ongoing downstream migration during wet season rains contributes significantly to the lowland gene pools </li></ul></ul>
  21. 21. Discussion: Bottlenecks <ul><ul><li>Immigration from genetically differentiated populations into the lowland populations creates an excess of novel alleles and an incomplete allelic distribution </li></ul></ul><ul><ul><li>Northern Drainage populations show evidence of population bottlenecks because the rivers drain into a marine environment (Caribbean Sea) </li></ul></ul><ul><ul><li>Tobago has undergone a population bottleneck and founder event followed by a rapid population expansion </li></ul></ul>
  22. 22. Discussion: Admixture <ul><ul><li>Admixed lowland populations may constitute genetically diverse ‘sink ‘ populations with small isolated upland populations acting as source populations </li></ul></ul>http://dm.hccfl.edu/cgs2822/07fa63686/jgammons/FinalProject/images/Freshwaterfish/guppies.jpg
  23. 23. Discussion: F ST and N e <ul><ul><li>Upland populations have small effective population sizes and large F ST </li></ul></ul><ul><ul><li>Alleles in these popualtions differ by one or two repeat units suggesting that mutation is driving genetic diversity in these populations </li></ul></ul><ul><ul><li>This suggests that the populations are in a mutation-drift balance </li></ul></ul><ul><ul><li>Upland populations are stable but small </li></ul></ul><ul><ul><li>Lowland populations are large and fluctuating </li></ul></ul>
  24. 24. Favorite Quote <ul><ul><li>‘ The Caroni drainage can be considered as a source-sink metapopulation, with the river furthest downstream a super sink, reciving immigrants from rivers upstream in the drainage’ </li></ul></ul>http://i.ehow.com/images/GlobalPhoto/Articles/4617306/guppy1-main_Full.jpg

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