Genetics and Reproductive Isolation of Rhagoletis Flies (Fruit Fly, Eclosion, Speciation, Electrophoresis, Host Selection)

100 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1986.The frugivorous flies of the Rhagoletis pomonella (Diptera: Tephritidae) species group have been cited as examples of sympatric speciation through divergence in host plant association. Despite the attention given to and the controversy engendered by the biology of these flies, both by applied entomologists concerned with the flies' status as agricultural pests and by evolutionary biologists interested in modes of speciation, this is the first study to provide substantial support for genetic differentiation for traits important in host selection and in maintenance of reproductive isolation among these sibling species and host-associated populations.Interspecific or interpopulational crosses have demonstrated three levels of partial barriers to hybridization. First, a measure of temporal isolation among host-associated populations is afforded by genetic control of seasonal divergence in post-diapause eclosion patterns. Second, the combined effects of the use of (a) the host plant as a rendezvous site for mating and (b) genetic differences among these flies for oviposition response to actual host fruits and to artificial fruits of different sizes limit the opportunity for encounter between flies from different populations. Third, even if interspecific encounters occur, differences in mating response and egg hatch success further reduce the potential for introgression.It is essential to emphasize that, while these factors must be important in maintaining reproductive isolation among these sibling species or host-associated populations of the R. pomonella group, it should not be concluded from this study that these factors were responsible for the divergence and subsequent speciation. Therefore, these results should not be construed as evidence in direct support of the hypothesis of sympatric speciation by these host-associated fruit flies.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD