Skip to main content
Login | Suomeksi | På svenska | In English

Browsing by Subject "plastid genome"

Sort by: Order: Results:

  • Johansson, Niko (2024)
    The taxonomy of the green macroalgal genus Monostroma is poorly known in the Baltic Sea region and worldwide.Two species of Monostroma are currently reported from the Baltic Sea: the cosmopolitan spring species Monostroma grevillei and a proposed endemic, free-floating summer species Monostroma balticum. However, previous work has highlighted the unclear taxonomic status of M. balticum, and some consider it a growth form of the cosmopolitan species M. grevillei or a monostromatic growth form of Ulva spp. No molecular data exists of M. balticum, and the morphological characteristics distinguishing this species from M. grevillei and similar species are unclear in the literature. The aim of this thesis is to explore the taxonomic status of M. balticum by firstly systematically reviewing the historical and contemporary literature, including the original description, to illuminate the current morphological circumscription of M. balticum and related species. Secondly, using DNA barcoding based on the tufA -marker, fresh collections of foliose monostromatic green algae from the Baltic Sea region are identified molecularly and put into an evolutionary context using phylogenetics. Thirdly, novel plastid genomes are produced from monostromatic green algae to explore the genomic features of these algae and to see if they aid in species delimitation or phylogenetic approaches. Based on the literature review, the morphological and ecological features used in specimen identification currently (micromorphology, free-floatingness and occurrence in summer) may not be enough for accurate identification, and especially the micromorphological features are quite vaguely described in contemporary literature making their use difficult in practise. All monostromatic specimens collected are identified using DNA barcoding as either M. grevillei, Kornmannia leptoderma or Ulva intestinalis, and those specimens mostly resembling the original description of M. balticum are recovered as U. intestinalis. Plastid genomes were produced from M. grevillei, K. leptoderma and U. intestinalis, from the latter species separate genomes were generated from a typical tubular-morphology specimen as well as a “M. balticum”-morphology specimen. M. grevillei and K. leptoderma plastids were unusual in being large, inflated by many introns and intrageneric regions and having many rearrangements. Produced U. intestinalis plastomes are similar and resemble previously published Ulva genomes. The accurate identification of M. balticum -like specimens is discussed, and for future work DNA barcoding is suggested to be the main tool for specimen identification. This thesis provides evidence towards a previous hypothesis that M. balticum is not a distinct species but a specific growth from of U. intestinalis. Investigating historical herbarium specimens, including original material, using molecular methods is proposed to verify if M. balticum should be synonymised formally with U. intestinalis. The potential drivers of the shift in growth form of U. intestinalis are discussed. Finally, the plastid genome landscape in these foliose green algae is discussed.