The Evolution of an Invasive Plant, Sorghum halepense L. (‘Johnsongrass’)

Abstract

From noble beginnings as a prospective forage, polyploid Sorghum halepense ('Johnsongrass') is both an invasive species and one of the world's worst agricultural weeds. Formed by S. bicolor x S. propinquum hybridization, we show S. halepense to have S. bicolor-enriched allele composition and striking mutations in 5,957 genes that differentiate it from representatives of its progenitor species and an outgroup. The spread of S. halepense may have been facilitated by introgression from closelyrelated cultivated sorghum near genetic loci affecting rhizome development, seed size, and levels of lutein, a photochemical protectant and abscisic acid precursor. Rhizomes, subterranean stems that store carbohydrates and spawn clonal propagules, have growth correlated with reproductive rather than other vegetative tissues, and increase survival of both temperate cold seasons and tropical dry seasons. Rhizomes of S. halepense are more extensive than those of its rhizomatous progenitor S. propinquum, with gene expression including many alleles from its non-rhizomatous S. bicolor progenitor. The first surviving polyploid in its lineage in ∼96 million years, its post-Columbian spread across six continents carried rich genetic diversity that in the United States has facilitated transition from agricultural to non-agricultural niches. Projected to spread another 200-600 km northward in the coming century, despite its drawbacks S. halepense may offer novel alleles and traits of value to improvement of sorghum.

A genome-wide investigation of the effect of farming and human-mediated introduction on the ubiquitous seaweed Undaria pinnatifida

“…This kelp presents the rare characteristic of being independently cultivated in its native range and introduced in four continents outside its native range. This situation contrasts with other well-studied cases such as Oryza 33 and Sorghum 34 in which domestication preceded escape to the wild. Recent studies have demonstrated the importance of genome-wide analyses, based on whole-genome sequencing data, to understand human-driven evolutionary change, notably with respect to domestication 4 – 7 , with fewer studies examining invasive species 8 , 9 , and none addressing both aspects at the same time.…”

Rapid Evolution of Invasive Weeds Under Climate Change: Present Evidence and Future Research Needs

“…With climate change, S. halepense is predicted to spread further northward in North America, causing greater yield loss in Zea mays (corn) crops (McDonald et al, 2009). S. halepense exhibits many other evolutionary adaptations in addition to what we have listed here, enabling continual change of S. halepense populations at the northern edge of its range (Paterson et al, 2020).…”

“…Indeed, the evolutionary novelty allowing S. halepense to colonize more northerly environments in North America has been attributed to this genetic diversity. Its rhizomes have evolved cold tolerance, even though when it was introduced in the early 1800s it was a C 4 grass adapted only to the warmer climates consistent with its origin in western Asia (McWhorter, 1971;Paterson et al, 2020). Furthermore, northern populations may exhibit an annual life history, allowing S. halepense to overwinter more readily along the northern edge of its range (Warwick et al, 1986).…”

“…Because invasive weed life histories are so extremely diverse, along with the associated reproductive characteristics and genetics (Barrett et al, 2008), there are numerous questions regarding the implications of this diverse array of life histories under climate change. Even within individual weed species, there can be multiple life history strategies at play, such as for R. × bohemica (Gillies et al, 2016) or Sorghum halepense (Paterson et al, 2020). New methods of genetic analysis, including even whole-genome characterizations offer promising possibilities for understanding weed life histories better (e.g., see Liu et al, 2020a).…”

“…Ecosystem resistance, the third element of the invasive plant research framework (Young et al, 2017), is subject to wide variation in the face of climate change, such as the vulnerability of drought prone areas in the western USA to invasion and concomitant evolution of plant invaders taking advantage of low levels of ecosystem resistance (Table 3). Research on particular species like Sorghum halepense (Paterson et al, 2020) and Impatiens glandulfera (Cuda et al, 2020;Gruntman et al, 2020) indicates that invasive plants may invade new habitats under climate change, raising the alarm that other invasive plants may adapt to new habitats as climate changes. This presents a clear challenge to developing proactive management systems; as well as the need to understand and monitor the formation of novel invasive weed ecotypes, there is the need to manage ecosystems for greater resistance to invasion.…”