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Barriers evolving : reproductive isolation and the early stages of biological speciation
The process of speciation can be complex and represents the ultimate basis for biodiversity on the planet Earth. The contribution of various intrinsic reproductive barriers and their underlying phenotypic mechanisms were studied using two Drosophila model systems: the cactophilic sister species Drosophila arizonae and D. mojavensis, from the deserts of Mexico and the Southwestern USA, and populations of the circumboreal, hydrophilic fly, Drosophila montana, from North America and Northern Europe. Levels of premating isolation between D. arizonae and D. mojavensis as well as between populations of D. montana were significant and sensitive to experimental design. Further investigations of intrinsic barriers to gene flow among populations of D. montana from Canada, Finland and the USA showed that different mechanisms (premating vs. postmating) act with different strengths depending on the populations. Premating isolation was significant between all populations and postmating isolation was strongest in crosses between American (Colorado) females and Canadian (Vancouver) males. This was found to be due to a postmating, prezygotic barrier; while sperm from Canadian males were successfully transferred and stored after matings with American females, the majority of these eggs were not fertilized. The last study in this thesis aimed to determine whether cuticular hydrocarbons might play a role in sexual selection in D. montana. The study revealed significant variation in cuticular hydrocarbons among populations and between the sexes, as well as correlations between particular principal components or individual hydrocarbon peaks and behavioural measurements relevant to sexual selection. These effects appeared to be strongest in the Canadian population of the species. Thus, cuticular hydrocarbons may be involved in sexual selection within and sexual isolation between populations, although more direct tests using manipulation of CHCs are still needed. ...
- Artikkeli I: Jennings, J.H. & Etges, W.J. (2010). Species hybrids in the laboratory but not in nature: A reanalysis of premating isolation between Drosophila arizonae and D. mojavensis. Evolution, 64, 587-598. DOI: 10.1111/j.1558-5646.2009.00834.x
- Artikkeli II: Jennings, J., Mazzi, D., Ritchie, M., & Hoikkala, A. (2011). Sexual and postmating reproductive isolation between allopatric Drosophila montana populations suggest speciation potential. BMC Evolutionary Biology, 11(68). DOI: 10.1186/1471-2148-11-68
- Artikkeli III: Jennings, J., Snook, R. R., & Hoikkala, A. (2014). Reproductive isolation among allopatric Drosophila montana populations. Evolution, 68(11), 3095-3108. DOI: 10.1111/evo.12535
- Artikkeli IV: Jennings, J., Etges, W. J., Schmitt, T., & Hoikkala, A. (2014). Cuticular hydrocarbons of Drosophila montana: Geographic variation, sexual dimorphism and potential roles as pheromones. Journal of Insect Physiology, 61, 16-24. DOI: 10.1016/j.jinsphys.2013.12.004
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Sexual and postmating reproductive isolation between allopatric Drosophila montana populations suggest speciation potential Jennings, Jackson; Mazzi, Dominique; Ritchie, Michael; Hoikkala, Anneli (BioMed Central, 2011)Background - Widely distributed species with populations adapted to different environmental conditions can provide valuable opportunities for tracing the onset of reproductive incompatibilities and their role in the ...
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