Abstract
According to the Norwegian Flora (Elven et al. 2022), we have three accepted species of eelgrass in Norway: Zostera marina L. (eelgrass, ålegras), Z. noltii Hornem. (dwarf eelgrass, dverg- ålegras), and Z. angustifolia (Hornem.) Reichenbach (narrow-leaved eelgrass, smalt ålegras). Other studies only support two species: Zostera marina (eelgrass, ålegras) and Z. noltii Hornem. (dwarf eelgrass, dverg- ålegras), and regards Z. angustifolia as a subspecies of Z. marina (den Hartog 1972, Borum et al. 2004, Larkum et al. 2006). This study aims to investigate how many Zostera species are present in Norway and whether the morphologically species delimitation is confirmed by the molecular analyses, and which names should be applied to these taxa. Target capture sequencing analysis was applied to resolve the genetic delimitations. The morphological analyses were statistically significant with respect to differences between the three taxa in several characters: leaf width, apexes, number of veins, sclerenchymatic tissue, flowers, and seeds. Zostera angustifolia have a higher percentage of specimens with long, tough strands of sclerenchymatic tissue, while none of the Z. noltii specimens had visible fibers. The molecular analyses only supported two species; Zostera noltii and Z. marina. The Zostera specimens examined were collected from eelgrass beds during fieldwork in Oslofjorden, including Bliksekilen in Vestfold and Kurefjorden in Østfold, where all three taxa co-occur.