Marion Adelheid Wolf

Ulva (Chlorophyta, Ulvales) Biodiversity in the North Adriatic Sea (Mediterranean, Italy): Cryptic Species and New Introductions.

Ulva Linnaeus (Ulvophyceae, Ulvales) is a genus of green algae widespread in different aquatic environments. Members of this genus show a very simple morphology and a certain degree of phenotypic plasticity, heavily influenced by environmental conditions, making difficult the delineation of species by morphological features alone. Most studies dealing with Ulva biodiversity in Mediterranean waters have been based only on morphological characters and a modern taxonomic revision of this genus in the Mediterranean is not available. We report here the results of an investigation on the diversity of Ulva in the North Adriatic Sea based on molecular analyses. Collections from three areas, two of which subject to intense shipping traffic, were examined, as well as historical collections of Ulva stored in the Herbarium Patavinum of the University of Padova, Italy. Molecular analyses based on partial sequences of the rbcL and tufA genes revealed the presence of six different species, often with overlapping morphologies: U. californica Wille, U. flexuosa Wulfen, U. rigida C. Agardh, U. compressa Linnaeus, U. pertusa Kjellman, and one probable new taxon. U. californica is a new record for the Mediterranean and U. pertusa is a new record for the Adriatic. Partial sequences obtained from historical collections show that most of the old specimens are referable to U. rigida. No specimens referable to the two alien species were found among the old herbarium specimens. The results indicate that the number of introduced seaweed species and their impact on Mediterranean communities have been underestimated, due to the difficulties in species identification of morphologically simple taxa as Ulva.

Gracilaria viridis sp. nov. (Gracilariales, Rhodophyta): a new red algal species from the Mediterranean Sea

Sfriso A., Wolf M.A., Sciuto K., Morabito M., Andreoli C. and Moro I. 2013. Gracilaria viridis sp. nov. (Gracilariales, Rhodophyta): a new red algal species from the Mediterranean Sea. Phycologia 52: 65–73. DOI: 10.2216/12-007.1 We characterized a new Gracilaria species from the Venice Lagoon, Italy, using molecular analyses based on the plastid large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase gene (rbcL) and the intergenic RuBisCO spacer (rbcL-rbcS), combined with morphology data. This new entity was recorded on the artificial substrata of the Venice Gulf from March to July, adding to 12 Gracilaria taxa already recorded in the Mediterranean and Adriatic seas. Thalli exhibited a green-yellowish pigmentation with pink shades, and there was dense branching in the distal portions. Tetrasporangia were scattered on thallus cortex and distributed mostly on short, stipitate branchlets. The inner pericarp was connected to the gonimoblast by tubular nutritive cells. The male gametophytic plants formed round-elliptical spermatangial verrucosa-type conceptacles. This species grew attached on artificial rocky substrata of the low midlittoral and upper sublittoral zone in spring and early summer. Molecular analyses based on the plastid-encoded rbcL gene showed a 99.66% nucleotide identity with another Gracilaria sp. from southern Sicily. We compared our rbcL-rbcS spacer sequences with those of two cryptic species, and the phylogenetic analyses confirmed that the Venice populations were a new species. We suggested that the discovery of this new species was not due to an extra-Mediterranean introduction but the consequence of its misidentification as Gracilaria gracilis, which has a similar gross morphology.

Problems and solutions in Gracilaria systematics: an example from G. bursa pastoris (Gmelin) Silva.

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Rediscovery of a Forgotten Mediterranean Chaetomorpha Species in the Venice Lagoon (North Adriatic Sea): Chaetomorpha stricta Schiffner (Cladophorales, Chlorophyta)

Abstract On the basis of bibliographical, morphological and molecular studies (SSU rDNA), the reinstatement of species rank for Chaetomorpha stricta Schiffner, a poorly known Mediterranean endemic species described in the early 20th century, is proposed. Previously reduced to a posterior heterotypic synonym of C. linum (O.F. Müller) Kützing, C. stricta clearly differs from the latter by its small, light green, free-living filaments entangled in dense masses, the cells 0.5 to 1.6 (rarely 2) times as long as broad, with cell walls lamellate and broad up to 75–90 μm thick, and by molecular data. Chaetomorpha stricta was rediscovered, in May 2011, in oligotrophic clear waters of a closed fishing pond in the Valle Cavallino (northern basin of the Venice Lagoon). A critical review of Chaetomorpha taxa reported in the Mediterranean Sea and a taxonomic key to the Mediterranean taxa currently accepted are presented.