A comparative study of clines, developmental time, viability and thermal adaptation in two species of Drosophila

FOLGUERA, G,; CEBALLOS, S.; SPEZZI, L.; FANARA, J. J.; HASSON, E.

BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY

Blackwell Publishing

Lugar: Oxford, Inglaterra; Año: 2008 vol. 92 p. 233 - 245

0024-4066

Understanding variation in life history traits is one key to understand natural selection. Larval developmental time (DT) is a very important trait in the life history of organisms that typically mature in ephemeral resources and studies in Drosophila brought up the possibility that DT and body size may be involved in a trade-off. In addition, latitudinal clines for body size are widely documented in Drosophila. The first question addressed in this study is whether developmental time (DT) and, also, viability (VT) vary clinally along latitudinal and altitudinal gradients in the specialist autochthonous Drosophila buzzatii and the generalist invasive D. melanogaster. Coincident and positive altitudinal clines across species and, direct and inverse latitudinal clines were observed for DT in D. melanogaster and D. buzzatii, respectively. Opposing latitudinal and altitudinal clines were detected for VT only in D. melanogaster. The patterns observed along altitudinal gradients led us to investigate whether flies living at lowland and highland environments may respond differentially to thermal treatments consisting of regimes of constant and alternating temperatures. Flies reared at higher mean temperature developed faster than at lower mean temperature in both species. In contrast, the response in VT differed greatly between species. Highland D. melanogaster were more viable than lowland regardless the treatment, whereas in D. buzzatii highland flies were more viable than lowland in alternating thermal regimes and the reverse was true in treatments of constant temperature. Our results suggest that thermal amplitude should be considered in investigations of complex matters such as thermal adaptation.