Fragment type and water depth determine the regeneration and colonization success of submerged aquatic macrophytes
Submerged aquatic plants predominantly disperse via vegetative means, with shoot fragments being the most important propagules. The establishment of new macrophyte stands largely depends on two parameters, (i) the regeneration of plant fragments and (ii) the successful anchorage of these fragments in the sediment (colonization). Here we studied both the regeneration and colonization abilities of six submerged aquatic plant species (Myriophyllum spicatum, Myriophyllum heterophyllum, Ceratophyllum demersum, Lagarosiphon major, Elodea canadensis and Hydrilla verticillata) with two fragment types (with and without apical tips, 6 cm fragment length) at two water depths (12 and 3 cm). Overall, M. spicatum, L. major, E. canadensis and H. verticillata showed stronger regeneration and colonization abilities than C. demersum and M. heterophyllum. In M. spicatum, L. major and H. verticillata, fragments with apical tips had a significantly higher likelihood of regeneration and colonization than fragments without apices. The presence of apical tips increased regeneration by a factor of up to 5 (L. major), and colonization by a factor of up to 6.5 (H. verticillata). Water depth had an even stronger effect on colonization of M. spicatum, L. major, E. canadensis and H. verticillata, but did not affect regeneration of any species examined. A shallow water depth significantly increased the likelihood of colonization by a factor of 3.5 (L. major) to 31 (M. spicatum). Our findings demonstrate the differences in the likelihood for initial colonization of fragments among aquatic plant species, leading to better predictions of species-specific spread potentials through plant fragments.
KeywordsDispersal Establishment Fragmentation Invasive alien aquatic plants (IAAPs) Spread Vegetative reproduction
We thank Prof. Dr. Hanno Gottschalk (School of Mathematics and Science, University of Wuppertal) for valuable comments on the statistical analysis. This work was financially supported by the Deutsche Bundesstiftung Umwelt (DBU) [Grant number 20016/450; P. Heidbüchel].
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