Trait variation, trade‐offs, and attributes may contribute to colonization and range expansion of a globally distributed weed

Abstract

Premise Trait variation, trade‐offs, and attributes can facilitate colonization and range expansion. We explored how those trait features compare between ancestral and nonnative populations of the globally distributed weed Centaurea solstitialis. Methods We measured traits related to survival, size, reproduction, and dispersal in field sampling following major environmental gradients; that of elevation in Anatolia (ancestral range) and that of precipitation in Argentina (nonnative range). We also estimated abundance. Results We found that overall variation in traits in ancestral populations was similar to that in nonnative populations. Only one trait—seed mass—displayed greater variation in ancestral than nonnative populations; coincidentally, seed mass has been shown to track global range expansion of C. solstitialis. Traits displayed several associations, among which seed mass and number were positively related in both ranges. Many traits varied with elevation in the ancestral range, whereas none varied with precipitation in the nonnative one. Interestingly, most traits varying with elevation within the ancestral range also displayed differences in attributes between ancestral and nonnative ranges. Unexpectedly, ancestral plants were more fecund than nonnative plants, but density was greater in the nonnative than ancestral range, indicating that C. solstitialis survives at larger proportions in the nonnative than ancestral range. Conclusions Our results suggest that maintaining levels of trait variation in nonnative populations comparable to those in ancestral populations, avoiding trait trade‐offs, and developing differences in trait attributes between ranges can play a major role in the success of many weeds in novel environments.

Trait evolution during a rapid global weed invasion despite little genetic differentiation

“…Our evidence of geographical trait differentiation supports previous findings of increased seed mass in the C . solstitialis non‐native range compared to the native range (Eren & Hierro, 2021; Graebner et al, 2012; Hierro et al, 2013, 2020) but do not support other evidence that C . solstitialis had evolved towards larger plant size in the introduced area (Barker et al, 2017; Dlugosch et al, 2015; Eriksen et al, 2012; García et al, 2013; Widmer et al, 2007).…”

“…Evidence of trait divergence in C . solstitialis from the literature is mixed, with some studies reporting no differences in plant size between native and non‐native ranges (Andonian et al, 2011; Eren & Hierro, 2021; Hierro et al, 2006), while others showed increased growth and higher aboveground biomass in C . solstitialis introduced range (Dlugosch et al, 2015; Eriksen et al, 2012; García et al, 2013; Graebner et al, 2012; Montesinos & Callaway, 2018a, 2018b; Widmer et al, 2007).…”

“…Specifically, another study found that native individuals in Anatolia have smaller capitulum size and produce more seeds without a pappus compared to non‐native individuals in Argentina which showed the opposite pattern (i.e. larger capitula and more pappus seeds) (Eren & Hierro, 2021). According to Miguel et al (2017), seed dimorphisms in C .…”

“…Moreover, the study by Barker et al (2017) identified similar levels of genetic diversity between native and introduced ranges and overall low genetic structure in the invaded range as well as evidence of multiple introductions from different sources in some areas of North America. Several phenotypic studies in this species demonstrated a higher performance of invasive genotypes compared to native genotypes including an increase in plant size (Barker et al, 2017; Dlugosch et al, 2015; Eriksen et al, 2012), increased seed size (Eren & Hierro, 2021; Hierro et al, 2013, 2020), and increased biomass production (Montesinos & Callaway, 2018a, 2018b; Widmer et al, 2007), faster growth rates (Graebner et al, 2012; Montesinos & Callaway, 2018a, 2018b), earlier flowering time (Dlugosch et al, 2015; Eriksen et al, 2012), increased leaf chemical defenses (Sotes et al, 2015), and higher reproductive output (Dlugosch et al, 2015), which suggests that rapid local adaptation has occurred in the introduced range. Still, there are few genetic studies in this species that have aimed to gain insights into evolutionary forces and identify potential adaptive traits contributing to fitness advantages and invasion across the global invasive range.…”