Native climate uniformly influences temperature-dependent growth rate in Drosophila embryos
Steven G. Kuntz, Michael B. Eisen
(Submitted on 22 Jun 2013)
It is well known that temperature affects both the timing and outcome of animal development, and there is considerable evidence that species have adapted so that their embryos develop appropriately in the climates in which they live. There have, however, been relatively few studies comparing development in related species with different optimal developmental temperatures. To determine the species-specific impact of temperature on the rate, order, and proportionality of major stages of embryonic development, we used time-lapse imaging to track the developmental progress of embryos in 11 Drosophila species at seven precisely maintained temperatures between 17.5C and 32.5C, and used a combination of automated and manual annotation to determine the timing of 34 milestones during embryogenesis. Developmental timing is highly temperature-dependent in all species. Tropical species, including cosmopolitan species of tropical origin like D. melanogaster, accelerate development with increasing temperature up to 27.5C, above which growth slowing from heat-stress becomes increasingly significant. D. mojavensis, a sub-tropical fly, exhibits an amplified slow-down with lower temperatures, while D. virilis, a temperate fly, exhibits slower growth than tropical species at all temperatures. The alpine species D. persimilis and D. pseudoobscura grow as rapidly as tropical flies at cooler temperatures, but exhibit diminished acceleration above 22.5C and have drastically slowed development by 30C. Though the fractional developmental time of major events is affected by heat-shock, developmental stages are otherwise uniformly affected by temperature, independent of species. Our results suggest that climate has a major effect on developmental timing and comparisons should be performed based on developmental stage rather than time.