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. 2022 Oct 11;13:880728. doi: 10.3389/fphys.2022.880728

FIGURE 2.

FIGURE 2

Map of the direction of spread and clinal variation of Drosophila melanogaster. Ancestral populations of Drosophila melanogaster from sub-Saharan Africa (Zambia) dispersed to Europe (ca. 10-19,000 years ago) and Asia (ca. 5,000 years ago) (David and Capy 1988; Haudry et al., 2020). From Europe there were subsequent dispersals to Australia and North America [<200 years ago (Keller, 2007)]. Population recently dispersed from Africa to North America and this dispersal is considered to be mediated through human movement. Clinal variation in D. melanogaster across latitudes and altitudes has been denoted by yellow circles and red triangles, respectively. Each circle or triangle represents particular geographic locations (not to scale) from which populations were collected. Latitudinal and altitudinal clines have been observed for D. melanogaster in Africa, Europe, Asia, and Australia. In North and South America only latitudinal clines are known for D. melanogaster and no clines are known across altitudes. Instead D. buzzati (blue) exhibits an altitudinal cline (thermal tolerance) in South America (Sørensen et al., 2005). Numbers in boxes represent the approximate time in years when D. melanogaster dispersed throughout the world from the ancestral population in Africa. Latitudinal clines have been depicted for desiccation tolerance (Asia: India (Karan et al., 1998)), chromosomal inversion (Asia: Japan (Inoue and Watanabe 1979)) and wing area (Australia, (James et al., 1995)), (South America, (Land et al., 1999)). Altitudinal clines have been depicted for body pigmentation (Asia (Parkash and Munjal, 1999)), diapause incidence (North America (Schmidt and Conde 2006)) and cold tolerance (Australia, (Collinge et al., 2006)). Latitudinal and altitudinal clines for wing area mirror each other in Europe and Africa (Klepsatel et al., 2014). All traits depicted exhibit positive clinal variation. Thus, wing area is larger for populations at higher latitudes and altitudes compared to populations at lower latitudes and altitudes (Klepsatel et al., 2014).