Flies evolved small bodies and cells at high or fluctuating temperatures

Area of Science:

• Evolutionary Biology
• Cell Biology
• Physiological Ecology

Background:

• Recent theories propose that cell size evolution is driven by body temperature fluctuations.
• Smaller cells may enhance metabolism during warming but incur higher maintenance costs.
• Understanding cell size adaptation is crucial for predicting organismal responses to climate change.

Purpose of the Study:

• To experimentally test the theory linking cell size evolution to temperature fluctuations.
• To investigate the evolutionary response of cell size in Drosophila melanogaster under different thermal regimes.
• To determine if cell size is a direct target of selection related to temperature.

Main Methods:

• Populations of Drosophila melanogaster were maintained under constant (16°C or 25°C) or fluctuating (16°C and 25°C) temperatures for evolutionary study.
• Measurements of thorax, wing, and cell sizes were taken from evolved fly populations.
• Genetic variation in cell size was analyzed in relation to wing size variation.

Main Results:

• Flies evolved at fluctuating or constant 25°C showed smaller thoraxes, wings, and cells compared to those at constant 16°C.
• Cell size in flies from fluctuating environments was intermediate between those from constant high and low temperatures.
• Genetic variation for cell size was largely independent of wing size, indicating selection on cell size itself.

Conclusions:

• The results support the theory that cell size evolves in response to temperature fluctuations.
• Smaller cell size appears to be an adaptive trait under higher or fluctuating temperatures.
• Further research is needed to elucidate the specific mechanisms conferring a selective advantage to smaller cells in variable thermal environments.