Browsing by Author "De Araujo, Liana Isabel"
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- ItemDispersal-reproduction trade-offs in Drosophila: implications for geographic distributions(Stellenbosch : Stellenbosch University, 2019-04) De Araujo, Liana Isabel; Terblanche, J. S.; Karsten, Minette; Stellenbosch University. Faculty of AgriSciences. Dept. of Conservation Ecology and Entomology.ENGLISH ABSTRACT: Life-history and performance trade-offs are common among insects. One major trade-off reported and frequently studied in a handful of taxa (e.g. butterflies, moths and crickets) is a dispersal-reproduction trade-off, such that individuals within a species that choose to disperse typically sacrifice reproductive output. However, the generality of this hypothesis has not been well examined, and its implications for invasion biology, geographic distributions and responses to climate change have yet to be fully determined. Here, I aimed to experimentally measure the magnitude and direction of potential dispersal-reproduction trade-offs between flies that choose to disperse (dispersers) and those that do not (resident) from five Drosophila species collected within South Africa, varying in their ecology. Next, to better understand how flight performance may be correlated to geographic range extent and potential responses to climate variability, I estimated the thermal performance curves of flight ability in 11 Drosophilidae species after two generations under standard laboratory conditions, and tested if any major morphological or ecological factors (e.g. sex, body mass, wing loading, geographic range size) predicted traits of thermal flight performance curves (optimum temperature, maximum performance, breadth of performance). My results showed two major sets of findings. First, there was only weak support for the dispersal-reproduction trade-off and that the reproduction trait scored (egg number vs. adult survival) yields different outcomes. For reproductive fitness (offspring’s adult emergence rates), only one of the five species (Drosophila melanogaster) tested showed statistically significant evidence of the trade-off in the direction expected. Furthermore, there was no correlation between the magnitude of the trade-off and geographic distribution ranking. Second, aspects of thermal performance curves for flight differed between species; however, the best explanatory model of these flight responses included significant positive effects of test temperature and wing area. Rank of the breadth of geographic distribution and phylogeny failed to explain significant variation in any of the traits of thermal flight performance curves in these 11 species. In conclusion, I argue that dispersal-reproduction trade-offs are unlikely to contribute greatly to an insect species’ invasion success or its geographic distribution, although environmental temperature and wing size will mediate dispersal responses upon introduction into novel environments. This study therefore suggests that dispersal-reproduction trade-offs are not as common as might have been expected when assessed systematically, at least not in the genus Drosophila, and moreover, that the extent of such trade-offs, and their magnitude and direction, require further investigation.