Clone-specific differences in Phragmites australis: Effects of ploidy level and geographic origin

Abstract

Phragmites australis (Cav.) Trin. ex Steud. is virtually cosmopolitan and shows substantial variation in euploidy level and morphology. The aim of this study was to assess clone-specific differences in morphological, anatomical, physiological and biochemical traits of P. australis as affected by the geographic origin, the euploidy level (4x, 6x, 8x and 12x), and to assess differences between native and introduced clones in North America. Growth, morphology, photosynthetic characteristics, photosynthetic pigments and enzymes were measured on 11 geographically distinct clones propagated in a common environment in Denmark. Any differences between the measured parameters were caused by genetic differences between clones.Overall, the largest differences between clones were found in ontogeny, shoot morphology and leaf anatomy. The North Swedish clone was adapted to short growing seasons and sprouted very early in the spring but senesced early in July. In contrast, clones from southern regions were adapted to warmer and longer growing seasons and failed to complete the whole growth-cycle in Denmark. Some clones from oceanic habitats with climatic conditions that do not differ much from conditions at the Danish growth site did flower in the common environment.The octoploid genotype in general had larger dimensions of leaves, taller and thicker shoots and larger cell sizes than did the hexaploid and tetraploid clones. The dodecaploid clone was neither bigger than the octoploid, nor significantly different from tetraploid and hexaploid clones in most of the morphological characters observed. Stomatal density decreased with increasing ploidy level, while length of guard cells increased. Tetraploid clones generally had morphometric dimensions, similar to hexaploids. Hence, polyploidy did not always result in an increase in plant size, probably because the number of cell divisions during development is reduced.Four North American clones were included in the study. The clone from the Atlantic Coast and the supposed invasive European clone resembled each other. The Gulf Coast clone differed from the rest of the clones in having leaf characters resembling Phragmites mauritianus Kunth. Thus, morphological characters are not unmistakable parameters that can be used to discriminate between introduced and native clones.The physiological and biochemical processes also differed between clones, but these processes showed considerable phenotypic plasticity and were therefore very difficult to evaluate conclusively.It is concluded that P. australis is a species with very high genetic variability which is augmented by its cosmopolitan distribution, clonal growth form and the large variation in chromosome numbers. It is therefore not surprising that large genetically determined differences in ontogeny, shoot morphology and leaf anatomy occur between clones. #

Morphometric structural analysis ofPhragmites australisstands in Lake Balaton

“…Morphological parameters of Phragmites in Lake Balaton fit well within the literature of European reed populations (Ku¨hl et al, 1999;Pauca´-Coma´nescu et al, 1999;Hansen et al, 2007), although significant differences were observed between and within the three study sites. In general, the morphological acclimation of Phragmites in the northern die-back stand resulted in significantly smaller plants as a result of developmental (lower number of nodes) and growth (shorter internode length) decline.…”

“…ex Steud.) is able to monopolize littoral zones and become the dominant species (Clevering, 1998;Ku¨hl et al, 1999;Bart and Hartman, 2000;Vretare et al, 2001;Hansen et al, 2007;Engloner, 2009). Phragmites is characterized by high growth rates and predominantly clonal vegetative reproduction.…”

Molecular data provide strong evidence of natural hybridization between native and introduced lineages of Phragmites australis in North America

“…Plants can reproduce both sexually, through wind-pollinated seeds, or asexually, through rhizomatous growth (Mal and Narine 2004). The species is allopolyploid (Raicu et al 1972), and has a base chromosome number of 12 with various ploidy levels including tetraploids (2n = 48), which dominate in Europe and North America, and octoploids (2n = 96), which dominate in Asia (Clevering and Lissner 1999;Hansen et al 2007). Although this species is native to North America, a comparison of chloroplast genotypes from current and herbarium samples revealed that there was a cryptic invasion of a European P. australis lineage into North America, most likely during the nineteenth century (Saltonstall 2002).…”

Genetic diversity and differentiation of fragmented reedbeds (Phragmites australis) in the United Kingdom

“…Plants can reproduce sexually through wind-pollinated seeds, or asexually through rhizomatous growth (Mal & Narine, 2004). The species is allopolyploid (Raicu et al, 1972), and has a base chromosome number of 12 with various ploidy levels including tetraploids (2n = 48), which dominate in Europe and North America, and octoploids (2n = 96), which dominate in Asia (Clevering & Lissner, 1999;Hansen et al, 2007). Several population genetic studies have been done on European P. australis (e.g., Koppitz, 1999;Pellegrin & Hauber, 1999;Koppitz & Kühl, 2000;Lambertini et al, 2008), but we know nothing about the population genetics of P. australis in the UK, where genetic diversity may be impacted by its geographical separation from continental Europe, by the significant declines that have been documented, or by ongoing management practices.…”