Abstract
Despite their near ubiquity across global ecosystems, the underlying mechanisms contributing to the success of invasive plants remain largely unknown. In particular, ecophysiological traits, which are fundamental to plants’ performance and response to their environment, are poorly understood with respect to geographic and climate space. We evaluated photosynthetic trait variation among populations, ecotypes and home climates (i.e. the climates from the locations they were collected) of the widespread and expanding invader Johnsongrass (Sorghum halepense). We found that populations vary in the maximum net photosynthetic flux and the light-saturated net photosynthetic rate, and that agricultural and non-agricultural ecotypes vary in apparent quantum yield and water-use efficiency (WUE). We also found that populations from warmer home climates had lower dark respiration rates, light compensation points and WUEs. As Johnsongrass expands across the USA the abiotic and biotic environments are driving variation in its genetics, phenotypes and its underlying physiology. Our study demonstrates the importance of evaluating physiological traits in invasive plants, especially as they relate to home climates.
Highlights
Invasive species cause broad ecological and economic damage worldwide (Vilà et al 2011), and pose a growing threat with worsening global change (Simberloff 2000)
We found that populations vary in the maximum net photosynthetic flux and the light-saturated net photosynthetic rate, and that agricultural and nonagricultural ecotypes vary in apparent quantum yield and water-use efficiency (WUE)
Our study demonstrates the importance of evaluating physiological traits in invasive plants, especially as they relate to home climates
Summary
Invasive species cause broad ecological and economic damage worldwide (Vilà et al 2011), and pose a growing threat with worsening global change (Simberloff 2000). Despite our broad understanding of invasive species, we still lack basic mechanistic information on what drives their success in most cases (Ren and Zhang 2009). Photosynthetic traits have been shown to be higher in invasive than native species (McDowell 2002), and vary among populations along environmental gradients (Jonas and Geber 1999). McDowell (2002) found that two invasive Rubus species had higher photosynthetic capacity and maintained higher net photosynthesis for longer than two co-occurring natives, though Feng et al (2007) did not find differences in photosynthetic parameters between two invaders and one native across different irradiance levels. There is equivocal evidence on whether photosynthetic traits differ in invasive than native populations, Received: 4 February 2020; Editorial decision: 10 April 2020; Accepted: 28 April 2020
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