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

Abstract

Several studies have revealed a variety of mechanisms of invasion of alien plant species. However, little is known on how those mechanisms and their associated effects on native species change across different life-cycle stages. Under controlled conditions, we assessed the interactions between the alien invasive species Centaurea solstitialis L. (Asteraceae) and two pioneer native species to the Chilean matorral; Baccharis linearis (Ruiz et Pav.) Pers. and B. paniculata DC. (Asteraceae). Competitive effects of the invader on natives were evaluated by combining different life-cycle stages: seed-seed, plantseed, and plant-plant. Seed germination of C. solstitialis was explosive and much faster than that of the native species. The presence of C. solstitialis (individuals or seeds) did not affect negatively the seed germination of the two Baccharis species. However, the presence of C. solstitialis plants significantly decreased the total biomass of Baccharis plants. Thus, the effect of C. solstitialis on Baccharis species depended on the life-cycle stage at which the interactions occurred. In the Chilean matorral, the early emergence of C. solstitialis could be an important invasion mechanism, enabling established plants to competitively displace late emerging seedlings of Baccharis species. The huge abundance of C. solstitialis in some disturbed matorrals suggests that seedling establishment of these two pioneer species could be limited. KEYWORDS: Allelopathy, matorral, Mediterranean, seed germination, yellow starthistle. RESUMENVarios estudios han revelado una variedad de mecanismos de invasión en las plantas alóctonas. Sin embargo, aún se conoce poco sobre cómo tales mecanismos y sus efectos asociados cambian a través de diferentes estados del ciclo vida. En este estudio evaluamos, bajo condiciones controladas, el resultado de las interacciones competitivas entre la especie invasora Centaurea solstitialis L. (Asteraceae) y dos especies pioneras nativas del matorral chileno; Baccharis linearis (Ruiz et Pav.) Pers. y B. paniculata DC. (Asteraceae). Estas interacciones fueron evaluadas combinando diferentes estados del ciclo de vida: semilla-semilla, planta-semilla y planta-planta. La germinación de C. solstitialis fue explosiva, siendo mucho más rápida que la de las especies nativas. La presencia de C. solstitialis (plantas o semillas) no disminuyó la germinación de las especies nativas de Baccharis. Sin embargo, la presencia de plantas establecidas de C. solstitialis disminuyó significativamente la biomasa de las plantas de Baccharis. Entonces, el efecto de C. solstitialis sobre las especies de Baccharis varió en función del estado del ciclo de vida en el cual las interacciones ocurrieron. En el matorral chileno, la emergencia temprana y explosiva de C. solstitialis podría ser un importante mecanismo de invasión, ya que aquellas plantas prontamente establecidas podrían desplazar competitivamente a las plántulas de Baccharis que emergen más tarde. La enorme abundancia de C. solstitialis en algunas zonas de ...

Biogeographic differences in the allelopathy of leaf surface extracts of an invasive weed

“…During its colonization history, the species had evolved many trait differences in its introduced areas, relative to the native range, such as increased seed size, germination timing and adult plant size (Graebner et al 2012, Hierro et al 2013Barker et al 2017), and increased competitive ability (Montesinos and Callaway 2017), among others. Other species in the genus were found to be allelopathic (Callaway and Aschehoug 2000;Ni et al 2010;Chen et al 2013;Aschehoug et al 2014), but previous experiments did not find evidence of root-mediated allelopathy in C. solstitialis (Carpenter 2007;Qin et al 2007); however, some studies suggest that leaf leachates may be allelopathic (Zamora 1984;Gómez-González et al 2009;Filipe et al 2016). All aerial parts of C. solstitialis possess several sesquiterpene lactones (Stevens and Merrill 1985;Alvarez 2008;Sotes et al 2015) which have well known pharmacological and biological inhibitory activity (Cheng et al 1992;Özçelik et al 2009), and that can act as an inducible chemical defense against herbivory (Beck et al 2008;Smith and Beck 2013;Oster et al 2015) or mediate competitive interactions with neighboring plants.…”

Flower removal increases rhizome mass in natural populations of Alstroemeria aurea (Alstroemeriaceae)

“…observation), so that at least some of the metamers making up the aerial shoots of A. aurea may be described as preformed organs (Barthélémy and Caraglio, 2007). The preformation of organs in young shoots of rhizomatous plants may be a favourable trait whenever the annual period of aerial growth is short, and may provide a competitive advantage over other herbaceous plants in early spring (Billings and Mooney, 1968;Gómez-González et al, 2009;Rice and Dyer, 2001). Nonetheless, preformation constrains the plastic response of plants to unforeseen conditions (Diggle, 1997;Geber et al, 1997;Werger and Huber, 2006): preformed organs would have anatomical and morphological structures suited for a set of environmental conditions that may differ from those actually occurring at the time these organs complete their growth.…”