Enhanced Growth and Seed Properties in Introduced vs. Native Populations of Yellow Starthistle (Centaurea solstitialis)

Abstract

There is much discussion as to why a plant becomes invasive in a new location but is not problematic in its native range. One example is yellow starthistle, which originates in Eurasia and is considered a noxious weed in the United States. We grew yellow starthistle originating from native and introduced regions in a common environment to test whether differences in growth would be observed. In growth chamber studies, seedlings originating from the invasive range were larger than seedlings from the native range after 2 wk. Seed starch content is an important component of initial seedling growth. The starch content of seeds from introduced populations was higher than that of seeds from native populations. Regression analysis showed a relationship between the amount of starch in the seeds and the weight of yellow starthistle seedlings after 2 wk growth. There was no difference in chromosome number, except in accessions originating from Sicily and Sardinia. Field studies conducted in France and Russia revealed that rosettes and mature plants grown under natural conditions were larger when grown from seeds originating from the invasive range than from seeds originating from the native range. The number of capitula per plant and stem diameters were not significant among all populations, but differences were noted. The F1 progeny of plants originating from U.S. seed, but grown and pollinated in France, showed no differences in seedling growth, mature plant characteristics, and seed starch content from the plants grown from field-collected U.S. seed. The changes in seed starch resource allocation and its relation to plant growth is useful in understanding factors that contribute to yellow starthistle's invasibility.

Neo-Allopatry and Rapid Reproductive Isolation

“…Other studies indicate that local adaptation in seed and seedling size, seed morphology, and seed dormancy has occurred since the introduction of C. solstitialis into the United States (Widmer et al 2007;Hierro et al 2009). Such local adaptation and reproductive isolation might contribute to invasiveness (e.g., by fixing advantageous adaptations in the more adapted populations of the nonnative range), but since the noninvasive C. sulphurea also shows evidence of intercontinental reproductive isolation, isolation per se may be unlikely to explain invasiveness.…”

Competitive Effects of the Alien Invasive Centaurea Solstitialisl. On Two Chilean Baccharis Species at Different Life-Cycle Stages

“…However, Quin et al (2007) reported the same results when they performed greenhouse experiments to evaluate the competitive interactions between C. solstitialis and five herbaceous species natives to California grasslands. Widmer et al (2007) suggest that C. solstitialis success in California is not fully explained by its life history traits (i.e., prolific seed production, high seed viability, deep-root system, etc. ), because those traits are also present in its native range.…”

“…), because those traits are also present in its native range. In fact, Widmer et al (2007) showed that C. solstitialis has changed the resource allocation in the invaded range, since seeds have larger reserve of starch compared to its native range. As consequence, seedlings are larger in the invaded range and it could give these plants an early competitive advantage against native plants (Widmer et al 2007).…”

“…In fact, Widmer et al (2007) showed that C. solstitialis has changed the resource allocation in the invaded range, since seeds have larger reserve of starch compared to its native range. As consequence, seedlings are larger in the invaded range and it could give these plants an early competitive advantage against native plants (Widmer et al 2007). This support the hypothesis that C. solstitialis has evolved in the invaded range, increasing its competitive ability (EICA hypothesis, Blossey & Nötzold 1995).…”

“…However, less investigation has been focused on how different mechanisms interact across different life-cycle stages of invasive and native species to explain the invasion success (e.g. Orr et al 2005, Widmer et al 2007, Ens & Frens 2008, Muoghalu 2008.…”