Evolution of isoprene emission capacity in plants

•Here, we propose a novel hypothesis on the evolution of isoprene biosynthesis and emission in plants.•We give an explanation for the different rates of isoprenoid emission between plant taxa.•We explain the apparent randomness of isoprene emission occurrence in plant lineages.•We present a guide to identify pre-conditions for large-scale emitters amid tropical tree taxa.

Light-dependent de novo volatile isoprene emission by terrestrial plants (approximately 2% of carbon fixed during photosynthesis) contributes as much as 0.5 Pg C/year to the global carbon cycle. Although most plant taxa exhibit either constitutive or inducible monoterpene emissions, the evolution of isoprene emission capacity in multiple lineages has remained unexplained. Based on the predominant occurrence of isoprene emission capacity in long-lived, fast-growing woody plants; the relationship between ‘metabolic scope’ of tree genera and their species richness; and the proposed role of high growth rates and long generation times in accelerating molecular evolution, we hypothesise that long-lived plant genera with inherently high speciation rates have repeatedly acquired and lost the capacity to emit isoprene in their evolutionary history.