Divergence at neutral and non-neutral loci in Drosophila buzzatii populations and their hybrids

Abstract

The impact of intraspecific hybridisation on fitness and morphological traits depends on the history of natural selection and genetic drift, which may have led to differently coadapted gene-complexes in the parental populations. The divergence at neutral and non-neutral loci between populations can be evaluated by estimating F ST and Q ST respectively, and hence give an estimate of drift and selection in the populations. Here we investigate (1) whether divergence between populations in quantitative traits (wing size and shape) can be attributed to selection or drift alone, (2) The impact of intraspecific hybridisation on estimators for divergence at neutral (F ST ) and non-neutral loci (Q ST ) in hybrids, (3) If measurement of shape is more informative than size in order to detect divergence in quantitative traits between populations. The aims were addressed by performing two hybridisations between three populations of Drosophila buzzatii, one between populations from Argentina and the Canary Islands (separated for 200 years), and the other between populations from Argentina and Australia (separated for 80 years). We observed the highest divergence at neutral loci between the Argentinean and Canary Island populations, but highest morphological divergence between the Argentinean and Australian populations, indicating that natural selection is acting on the wings. Divergence based on Q ST measures in the hybrids was sensitive towards increased phenotypic variance (r 2 p) within groups and should be used with care when r 2 p of populations differ. Our results indicate that measures of shape give a better estimate of divergence at the underlying quantitative traits loci than measures of size.

Elucidating the role of genetic drift and natural selection in cork oak differentiation regarding drought tolerance

“…Higher relative divergence in quantitative traits than in neutral markers ( Q ST > F ST ) suggests a spatially divergent selection, which favours different genotypes in different populations, whereas the opposite ( Q ST < F ST ) suggests that the same genotypes are favoured in different populations, which suggests spatially homogenizing selection. If the two measures do not differ significantly, the population differences in quantitative traits could be attributed to genetic drift and other neutral evolutionary processes (Andersen et al. 2007).…”

Interspecific hybridization does not affect the level of fluctuating asymmetry (FA) in the Drosophila bipectinata species complex

“…Literature is replete with studies concerning FA in hybrids (and comparison with parents) and the results are a mixed bag (Jackson 1937a, b;Felly 1980;Zaharov 1981;Graham and Felly 1985;Leary et al 1985;Ferguson 1986; Lamb and Avise 1987;Ross and Robertson 1990;lamb et al 1990;Markow and Ricker 1991;Graham 1992;Blows and Sokolowaki 1995;Hutchinson and Cheverud 1995;Alibert et al 1997;Andersen et al 2002Andersen et al , 2006Andersen et al , 2008Rego et al 2006;Carreira et al 2008;Vishalakshi and Singh 2009;Demontis et al 2010;Trotta et al 2010;Novicic et al 2011). Alibert and Auffray (2003) said that 71 % published work show an increase in FA in hybrids (of different genera, or species) from parents.…”

“…Also, we had no scope of checking the effect of breakdown of coadapted complexes having no option but to stop at the F1 generation, hybrid sons being sterile. However, coadaptation per se is more the attribute of a species and through interracial (intraspecific) hybridization studies it is often checked whether different populations or races within a species have evolved their own coadapted complexes (Singh 1972;Andersen et al 2002Andersen et al , 2008Novicic et al 2011). Among the members of this complex, D. bipectinata which is most widely distributed and genetically more variable has been used for investigations concerning coadaptation.…”

QST < FSTAs a signature of canalization

“…*Updated references are Andersen et al . (); Badri et al . (2008a,b); Chenoweth & Blows (); Demont et al .…”

“…For instance, Andersen et al . () showed that populations from highland or lowland environments (contrasted atmospheric conditions) generally presented a low Q ST (low genetic variance between populations), which is always lower than the F ST . At this stage, it is difficult to define a threshold between uniform selection and canalization.…”