New Hybrid Combinations Revealed by Molecular Analysis: The Unknown Side of North American Pondweed Diversity (Potamogeton)

• Published in: Systematic botany 2009-10, Vol.34 (4), p.625-642
• Main Authors: Kaplan, Zdenek, Fehrer, Judith, Hellquist, C. Barre
• Format: Article
• Language: English
• Subjects: Aquatic plants; Biological taxonomies; chloroplast DNA; descriptions; Direct Sequencing; DNA fingerprinting; DNA sequencing; Genetic aspects; genetic markers; genetic relationships; genetic variation; Genotypes; geographical variation; Hybridity; Hybridization; Hybridization, Vegetable; hybrids; Internal transcribed spacers; interspecific hybridization; Leaves; Methods; molecular sequence data; New Taxa; nucleotide sequences; Nucleotide sequencing; Observations; phenotypic variation; Plant morphology; plant taxonomy; Plants; Potamogeton; Potamogeton absconditus; Potamogeton aemulans; Potamogeton bicupulatus; Potamogeton epihydrus; Potamogeton gramineus; Potamogeton mirabilis; Potamogeton nitens; Potamogeton oakesianus; Potamogeton perfoliatus; Potamogeton richardsonii; Potamogeton versicolor; Relic Occurrence; restriction fragment length polymorphism; RFLP; Sequencing; Stipules; Structure; Taxa; Taxonomy; Varieties
• ISSN: 0363-6445; 1548-2324
• DOI: 10.1600/036364409790139745

The occurrence and diversity of Potamogeton hybrids was investigated in eastern North America, the region of the highest diversity of Potamogeton species in the world. For various reasons, however, the existence of hybrids in this area has been largely overlooked. ITS direct sequencing and RFLPs revealed four previously unknown hybrids, which are described as Potamogeton ×aemulans (P. bicupulatus × P. epihydrus), P. ×mirabilis (P. gramineus × P. oakesianus), P. ×versicolor (P. epihydrus × P. perfoliatus), and P. ×absconditus (P. perfoliatus × P. richardsonii). These are the first confirmed hybrids involving P. bicupulatus, P. epihydrus, P. oakesianus, and P. richardsonii. Another hybrid, P. ×nitens (P. gramineus × P. perfoliatus), is for the first time confirmed for North America with molecular markers. The hybrids' maternal parents were revealed by cpDNA sequencing. Phenotypically, two of the hybrids more closely resemble other taxa than their parents. Hybrid diversity and recognition in North America and in Europe are compared. Morphological versus molecular identification of hybrids, occurrence of hybrids in the absence of their parents, parental species relationships, long-term persistence of hybrid clones, vegetative dispersal, frequency of hybridization events, and hybrid distribution patterns are discussed.