Resolving the naturalization strategy of Solidago × niederederi (Asteraceae) by the production of sexual ramets and seedlings

Abstract

In this study, the authors aimed to revise the ability of Solidago 9 niederederi, a hybrid between S. canadensis and S. virgaurea, to produce sexual ramets and seedlings as a part of its naturalization strategy. Based on a two-season garden cultivation experiment, we showed that the hybrid produces more generative ramets than vegetative ones and the number of generative ramets increases from one season to another with an increasing number of stem buds located on the caudices. We also revealed a spontaneous seedling recruitment by the hybrid during cultivation in the garden. Based on the seed germination test under laboratory conditions, we evidenced that the hybrid can reach a higher final germination percentage than S. canadensis but a lower one than S. virgaurea. Based on field studies conducted in 35 populations in Poland, the hybrid formed the largest populations in tree plantations and on abandoned fields, reaching 16.5 and 15.7 ramet clusters on average, respectively. The most abundant populations were found on abandoned fields; however, the mean number of ramets per cluster did not differ remarkably among habitats (H = 6.5, p = 0.163). In all populations, the mean number of vegetative ramets per cluster reached 0.85, while the generative ones achieved 6.43 on average. The statistical analysis proved that the aforementioned differences are significant (t = -12.6, p = 0.0002). Our results suggest that S. 9 niederederi is able to generate its own offspring by sexual reproduction and that abandoned fields seem to be the most suitable habitats for its establishment.

The importance of sexual, asexual and mixed ramet clusters in production of descendant ramets in populations of Solidago ×niederederi (Asteraceae)

“…In this study, the stem buds and young leaf rosettes located on the caudices of the hybrid were treated as potential descendant ramets; however, their transformation into new shoots was not investigated. Although it was recently evidenced that the number of ramets in S. ×niederederi can effectively increase from one season to another (Pliszko and Kostrakiewicz-Gierałt 2017), the lifespan of ramets and the longevity of clones of the hybrid remain unknown. Interestingly, S. virgaurea, in which the clonal clusters of ramets resemble those found in the hybrid, has perennial ramets and low vegetative mobility (Tamm et al 2002).…”

“…However, the number of shoots in clonal clusters of the hybrid is usually higher than in S. virgaurea (Pliszko 2013). Moreover, as currently known, the hybrid has no ability to form long rhizomes which are found in S. canadensis (Pliszko and Kostrakiewicz-Gierałt 2017). Interestingly, based on field observations, the clonal clusters of shoots of the hybrid can be divided into three types, namely sexual ramet clusters (all shoots with the capitula), asexual ramet clusters (all shoots with no capitula), and mixed ramet clusters (some shoots with and other without the capitula).…”

“…The hybrid origin of Solidago ×niederederi was successfully confirmed by morphological, molecular, and phytochemical methods (Karpavičienė and Radušienė 2016;Pliszko and Zalewska-Gałosz 2016;Radušienė et al 2018); however, its ecology is poorly recognized Kostrakiewicz-Gierałt 2017, 2018). It has been naturalized in several countries in Europe, including Austria, Poland, Lithuania, and Latvia (Pliszko and Kostrakiewicz-Gierałt 2017;Jaźwa et al 2018 and literature cited therein). It occurs in anthropogenic habitats such as abandoned fields, disused quarries, roadside slopes, railway embankments, tree plantations, and arable fields with grass-legume mixtures, being associated with its parental species (Pliszko and Kostrakiewicz-Gierałt 2017 and literature cited therein).…”

“…All the ramets in clonal clusters of the hybrid arise from the resting buds located on the caudices (Pliszko and Kostrakiewicz-Gierałt 2017). During the growing season, some of the resting buds develop into shoots (asexual or sexual) or small leaf rosettes at the base of the shoots, whilst others stay untransformed.…”

“…Furthermore, leaf rosettes of the hybrid can also sprout into new shoots from one season to another, similarly to leaf rosettes of S. virgaurea. According to Pliszko and Kostrakiewicz-Gierałt (2017), the resting buds located on caudices are essential for S. ×niederederi persistence and ramet production and the hybrid produces more sexual shoots (generative ramets) than asexual ones (vegetative ramets) regardless of the type of habitat and the size of the clone.…”