The Comparative Evolutionary Biology of the Sibling Species, Drosophila melanogaster and D. Simulans

Parsons, P. A.

doi:10.1086/408437

Cited by 79 publications

(42 citation statements)

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“…For example, D. melanogaster appears to be more tolerant of high ethanol concentrations, and the two species differ in their seasonal abundances and thermal tolerances (Parsons 1975b(Parsons , 1977. Moreover, it is known that their geographic centers of diversity vary, with D. melanogaster being most diverse in South-Central Africa While differences in the strength of clinal variation in D. simulans compared to D. melanogaster may suggest that the two species are responding to their local environments in different ways, the findings of Machado et al (2015), differentiation in patterns of gene expression , and phenotypic clines in traits such as body size indicate that D. simulans is likely evolving, in at least some capacity, to spatially varying selection.…”

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Genomic Patterns of Geographic Differentiation in Drosophila simulans

2016

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Geographic patterns of genetic differentiation have long been used to understand population history and to learn about the biological mechanisms of adaptation. Here we present an examination of genomic patterns of differentiation between northern and southern populations of Australian and North American Drosophila simulans, with an emphasis on characterizing signals of parallel differentiation. We report on the genomic scale of differentiation and functional enrichment of outlier SNPs. While, overall, signals of shared differentiation are modest, we find the strongest support for parallel differentiation in genomic regions that are associated with regulation. Comparisons to Drosophila melanogaster yield potential candidate genes involved in local adaptation in both species, providing insight into common selective pressures and responses. In contrast to D. melanogaster, in D. simulans we observe patterns of variation that are inconsistent with a model of temperate adaptation out of a tropical ancestral range, highlighting potential differences in demographic and colonization histories of this cosmopolitan species pair.KEYWORDS geographic variation; population genomics; Drosophila T HE geographic distribution of genetic or phenotypic variation can provide valuable insight into the process of adaptation. For example, consistent patterns of genetic variation across space have long been interpreted as evidence for local adaptation owing to spatially varying selection (Endler 1977; Adrion et al. 2015). This is well illustrated in populations of Drosophila melanogaster, a model system showing consistent phenotypic and molecular clines across environmental gradients (Hoffmann and Weeks 2007). Among these, the association of latitude with variation in ecologically relevant traits such as heat knockdown resistance, chill coma recovery, and diapause incidence Schmidt and Paaby 2008) provides strong support for local adaptation to climate.Despite efforts to understand the potential adaptive nature of molecular variation in populations of Drosophila, there remains some disconnect between our understanding of allele-frequency clines and phenotypic clines, of which the latter are more easily and intuitively interpretable. For the vast majority of clinal molecular polymorphisms in Drosophila, the mechanisms underlying their maintenance are poorly understood. Nevertheless, because gene flow in Drosophila is thought to be high, strong differentiation often can be argued as evidence of local adaptation. Moreover, because the physical scale of linkage disequilibrium (LD) in Drosophlia is often smaller than the size of genes (Langley et al. 2012), differentiation between populations generally is associated with hypotheses regarding individual genes as targets of selection.Observation of parallel patterns of differentiation furthers the argument for an adaptive basis to differentiation, and in general, comparisons of patterns of variation across independent replicate geographic transects may contribute to an understanding of...

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Genomic Patterns of Geographic Differentiation in Drosophila simulans

2016

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“…Many studies of the ecology, ecophysiology and genetics of these domestic species have attempted to understand their population dynamics, ecology and other reasons of which may underlie their demographic success (e.g., Parsons, 1975;l980a;Parsons and Stanley, 1981).…”

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Enzymatic and quantitative variation in European and African populations of Drosophila simulans

et al. 1985

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Allozyme polymorphism at 15 loci of D. simulans was studied in 7 natural populations from Europe, North and tropical Africa. Morphological traits were studied in nine European and eleven Afrotropical strains.Within a population, the biochemical polymorphisms of Drosophila simulans and its sibling Drosophila melanogaster are not very different, although D. simulans has a lower heterozygosity. Between-populations genetic differentiation is however much lower in D. simulans than in D. melanogaster. Several loci of D. simulans do exhibit latitudinal trends but these are relatively weak.For morphological traits, both species show an increase of size with latitude, but geographic variation is again less pronounced in D. simulans. Both species are native to tropical Africa and have colonised the rest of the world. During this process, D. simulans has undergone much less geographic differentiation than has D. melanogaster, so that the ecological success of the two species is not correlated with similarities in their genetic properties. INTflODUCTIONAmong about 2500 species known in the drosophilid family (Wheeler, 1981), only 21 have a subcosmopolitan status, in that they exist in at least three non-adjacent biogeographic realms (David and Tsacas, 1981). All these species occupy their present geographic range as a result of involuntary transport by man. Among the 21 species, the sibling D. melanogaster and D.simulans are especially interesting since they are the only two which possess large populations in both tropical and temperate conditions (David and Tsacas, 1981). Many studies of the ecology, ecophysiology and genetics of these domestic species have attempted to understand their population dynamics, ecology and other reasons of which may underlie their demographic success (e.g., Parsons, 1975; l980a;Parsons and Stanley, 1981).Populations of D. melanogaster, are genetically highly differentiated, for chromosomal polymorphism (Ashburner and Lemeunier, 1976;

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“…In the laboratory, D. melanogaster has a physiological optimum at 21 °C (DAVID & CL A VEL, 1966; (Mc KENZIE, 1978; T A NT AW Y & M ALLAH , 1961), and longevity (PARSONS, 1977;. These observations are in accordance with most of the geographical and seasonal distributions of these species: D. simulans outnumbers D. melanogaster in the regions where temperature fluctuations are small (PARSONS, 1975;ROCH A -P ITE , 1980 …”

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confidence: 72%