Evolution of Discontinuous Gas Exchange Cycles
Despite being well described, the mechanisms responsible for the evolution of discontinuous gas exchange cycles are largely unknown. Discontinuous gas exchange cycles have long been thought to be an adaptation to conserve water when living in a terrestrial environment (the hygric hypothesis). However, recent studies question the hygric hypothesis, and several alternative hypotheses have been proposed. For discontinuous gas exchange cycles to be considered adaptive, the origin and subsequent persistence of the trait must be demonstrated to be a result of natural selection.
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