Differences in C₃ and C₄ start-of-season (SOS) (a), end-of-season (EOS) (b), growing season length (c), and growing season productivity (d).

<p>Y-axis for panels (a)–(c) is the Julian day-of-year or DOY; y-axis for panel (d) is integrated NDVI, which is unitless, based on logistic models using 10-year timeseries of MODIS NDVI (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0107396#s2" target="_blank">Methods</a>). The growing season in Hawaii crosses the calendar year so that SOS begins at a later DOY than EOS. Most Poaceae species fall within the ‘BEP’ or ‘PACMAD’ clade. All C₄ grasses are in the ‘PACMAD’ clade.