Evolutionary responses of invasive grass species to variation in precipitation and soil nitrogen

Abstract

Summary1. Global climate models suggest that many ecosystems will experience reduced precipitation over the next century and the consequences for invasive plant performance are largely unknown. Annual invasive species may be able to quickly evolve traits associated with drought escape or tolerance through rapid genetic changes. 2. We investigated the influence of 5 years of water and nitrogen manipulations on trait values in a southern California grassland system. Seeds from two annual grass species (Avena barbata and Bromus madritensis) were collected from experimental plots and grown in a common environment over two generations. We measured 14 physiological, morphological, phenological and reproductive traits. 3. Both species displayed phenotypic differences depending on the water treatment from which they were collected, but not depending on the nitrogen treatment. Both species displayed trait values characteristic of drought escape (e.g. earlier flowering in A. barbata and B. madritensis, lower water-use efficiency in B. madritensis) when grown from the seeds collected from plots that experienced five years of reduced precipitation. Furthermore, A. barbata individuals grown from the seeds collected from drought plots had higher reproductive output and higher photosynthetic performance than individuals grown from water addition plots, with individuals grown from ambient plots displaying intermediate trait values. Notably, we found no phenotypic variation among treatments for six root traits. 4. Synthesis. Trait differences were observed following two generations in a common garden, suggesting that treatment differences were genetically based. This suggests that populations were responding to selection over the 5 years of water manipulations, a remarkably short time period. The rapid evolutionary responses observed here may help these two widespread invasive grass species thrive under reduced precipitation scenarios, which could have important implications for fire dynamics, invasive species management and native plant restoration in communities invaded by annual grasses.

The response of root traits to precipitation change of herbaceous species in temperate steppes

“…Larson and Funk () reported that diverse directions and extents of responses in root traits to watering treatments were detected both in seedlings of woody and herbaceous species. However, Nguyen et al () found no phenotypic variation in the examined root traits among water treatments. Therefore, the mechanisms underlying the diverse response patterns warrant further exploration.…”

“…Several studies exploring the intraspecific responses of root morphological and chemical traits to changing water availability have revealed that both of the hypotheses are tenable (Larson & Funk, 2016;Nguyen et al, 2016;Padilla, Miranda, Jorquera, & Pugnaire, 2009;Ryalls, Moore, Johnson, Connor, & Hiltpold, 2018). For example, Ryalls et al (2018) found that the SRL of a meadow grass (Microlaena stipoides) decreased and diameter and tissue density increased under deluge.…”

“…The results on responses of root traits to water treatments mainly came from the greenhouse experiments (Larson & Funk, 2016;Nguyen et al, 2016;Padilla et al, 2009;Ryalls et al, 2018). However, the interactions between plants and environments are more complex and variable in field conditions than in controlled conditions, thus leading to substantial differences in morphological traits between controlled environments and under field conditions (Poorter et al, 2016).…”

High standing genetic variation in an invasive plant allows immediate evolutionary response to climate warming

“…For instance, Skroppa and Kohmann 48 demonstrated adaptation of Norway spruce ( Picea abies ) to local climatic conditions after only one generation, and Franks et al 49 found rapid evolution of flowering time in the annual Brassica rapa in response to climate change after just three generations. More recently, Nguyen et al 50 showed earlier flowering in two invasive plant species in response to selection over few generations of water manipulations, and Nowak et al 51 demonstrated adaptive evolution of the Alpine Pennycress Noccaea caerulescens after one generation of exposure to various levels of zinc contamination in the soil. Due to multiple introductions and admixtures between differentiated populations, either prior or post-introduction, invasive plants can exhibit large within-population genetic diversity 52 , This has also been found for ragweed in Europe 23,44,45 .…”

Optimal control of invasive species with economic benefits: Application to the Typha proliferation

“…In this direction, it is shown in Brooks et al (2004) and Brown, Mitchell, and Graham (2002) that a possible hybridization with apparent native species can lead to genetic integrity issues. The evolutionary responses of some invasive species to nitrogen and water manipulations have been studied in Nguyen et al (2016), and the main observation is that their high capability of adaptation correlates with their genetics. This heralds the response of invasive species to future climate change.…”