Abstract
Tolerance of cold and heat and body size are traits that are important in thermal selection. Latitudinal and altitudinal transects include environments that gradually change in temperature. However, while there are studies on the effects on body size and cold tolerance in natural populations sampled mostly along latitudinal transects, there are few such studies along altitudinal transects. Resistance to starvation and desiccation, which are also thought to be affected by temperature, are the focus of studies on clines. In this study, we measured the variation in tolerance of cold (chill coma recovery time), body size, resistance to starvation and desiccation in isofemale lines of Drosophila melanogaster and D. simulans that originated from four locations (50 m - 1500 m) along an altitudinal transect in the southern part of Turkey. This revealed clines in the tolerance of cold and body size along the altitudinal transect with some degree of difference between these two species, whereas there were no clines in resistance to starvation and desiccation. This study revealed some differences and similarities between the sibling species D. melanogaster and D. simulans.
Highlights
Distribution of species and their phenotypic variation in many quantitative traits are shaped by different environmental factors
We determined the body size, chill coma recovery, resistance to starvation and desiccation in the laboratory of 3rd generation isofemale lines of D. melanogaster and D. simulans that were reared from females collected along an altitudinal transect
Intraspecific comparisons between locations revealed few differences: For D. melanogaster, the location was highly significant for body size (Table 3), but this significance was due to the result for the highest location Tufanbeyli, at which mean body size differed markedly from that recorded at the other locations (Table 2)
Summary
Distribution of species and their phenotypic variation in many quantitative traits are shaped by different environmental factors (temperature, air pressure, humidity etc.). Latitudinal and altitudinal transects show a remarkable difference in terms of geographic scales; the difference between the lowest and highest latitude can cover thousands of kilometres, whereas it can be only a few kilometres in altitudinal transects (Bubliy & Loeschcke, 2005). Even so, they show similar environmental patterns especially in climatic factors like temperature. They show similar environmental patterns especially in climatic factors like temperature In this way, altitudes are thought to mirror latitudes (Klepsatel et al, 2014) and similar clinal patterns are expected along altitudinal transects. Besides these differences and similarities, altitudinal transects occur over relatively short geographical scales, which may allow a relatively high gene flow between locations compared to latitudes and provide an opportunity to test the possibility of local adaptation in spite of gene flow (Keller et al, 2013)
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