1,721,064 research outputs found
The genus Lithophyllum (Corallinales, Rhodophyta) in the Mediterranean: current knowledge of its taxonomy, phylogeny and biogeography.
No full textWith 142 species currently accepted, Lithophyllum is the most species-rich genus in the coralline algae, a cosmopolitan group of calcareous seaweeds belonging to the phylum Rhodophyta (red algae). The genus has a particularly high floristic and ecological relevance in the Mediterranean Sea, where its presence since the mid Miocene is documented by fossil records. Our understanding of the taxonomy, distribution and biogeography of Lithophyllum in the Mediterranean has progressed in recent years thanks to the use of molecular data (DNA sequence data and transcriptomic data). At present, 17 species of Lithophyllum are known from the Mediterranean; some are recent records, for which the presence has been revealed by DNA sequence data. The actual diversity of the genus, however, is certainly higher, as the existence of a complex of cryptic species (the Lithophyllum stictiforme complex) was recently demonstrated. Molecular studies also revealed contrasting biogeographic patterns: whereas some species are widespread, others appear to have a circumscribed distribution and are known only from a few locations or regions. These patterns are considered a consequence of speciation/population fragmentation events related to hydrogeological changes of the Mediterranean in the last 5 mya. A full taxonomic and biogeographic reassessment will require further studies based on extended geographic sampling, re-examination of herbarium collections and sequencing of selected type specimens
Potential of epiphytic macroalgal vegetation as indicator of conservation status of Mediterranean algal forests
No full textMacroalgal forests are habitats of critical importance in coastal areas because of the ecosystem services they provide, since these communities represent major biodiversity repositories, nursery areas, and bioindicators of high environmental quality1. In the Mediterranean, most macroalgal forests are formed by habitat-forming brown seaweeds (Cystoseira, Ericaria, Gongolaria). These ecosystems are seriously threatened by multiple stressors, both natural and anthropogenic, and regressed in the last decades with consequent habitat fragmentation1, shifting from complex tridimensional ecosystems to algal communities with smaller size and simpler structure. The interactions between macroalgal forests and their associated biota have a crucial ecological relevance, resulting in a key-interplay which should be considered to plan conservation programs in coastal areas2. Epiphytes respond faster to anthropogenic stressors than canopy-forming algae. Therefore, the assessment of common patterns in epiphytic communities may allow the use of these assemblages as tools for the evaluation of changes in the status of macroalgal forests3. Epiphytic assemblages associated with forests of the brown seaweed Gongolaria barbata in different conservation conditions (continuous and fragmented) were investigated in late spring-early summer 2023 at 5 sites along the Conero Riviera (Ancona). Sampling was carried out following a nested design; a branch was collected from six thalli of G. barbata at each each site. Morphometric parameters of the branches were measured (length, width, number of secondary branches per branch and surface). Epiphytes were manually removed from each branch and identified by microscopic observation. The most common epiphytes were also identified based on a DNA barcoding approach, using suitable markers for species identification (tufA, rbcL, psbA, COI, ITS). Overall, 21 macroalgal epiphytes were recorded, 5 of which were primary epiphytes (directly attached to Gongolaria) and 16 were also found as secondary and tertiary epiphytes. Vertebrata fruticulosa was present in all samples as primary epiphyte. Ceramium siliquosum was the species most frequently found as secondary epiphyte, mostly growing on Vertebrata, and Didymosporangium repens was the species most frequently found as tertiary epiphyte, exclusively growing on C. siliquosum. The results did not show clear differences between continuous and fragmented populations, although the epiphytic community at the most urbanized site differed significantly from the others both in terms of abundance and species number. The DNA sequence data unraveled some cases of cryptic diversity in some genera of green and red algae (Ulva, Corallina, Pachymeniopsis, Vertebrata). Further analyses are currently ongoing and the study is being extended to populations of Gongolaria barbata of other Mediterranean regions. Moreover, the work will be complemented by DNA metabarcoding data based on sequencing of the 23S marker (flank Domain V of the 23S plastid rRNA gene). For this purpose, 23S sequences are being produced and processed to build a sequence library to be used for species assignment of eDNA results
Diversity of Mediterranean coralline algae: recent advancements in the knowledge of a highly threatened group of seaweeds
No full textCoralline algae are globally distributed ecosystem engineers that in the Mediterranean Sea act as key builders of habitats (such as coralligenous concretions, rims of Lithophyllum byssoides, rims of articulated corallines and rhodolith beds) extending on large stretches of coastal rocky bottoms. Due to the semi-enclosed nature and oceanographic features of the basin, Mediterranean corallines are considered particularly vulnerable to future climatic changes. For this reason they have attracted much interest in the last decades, with many investigations focusing primarily on responses to ocean acidification and responses of coralline-dominated communities to anthropogenic stressors. Several aspects of their diversity, however, have also received great attention. Taxonomy and systematics of Mediterranean corallines have been studied for more than two centuries but, until recently, the classification of these seaweeds was based entirely on traditional morphoanatomical grounds. The introduction of molecular data has substantially reshaped our view of their taxonomic diversity. The first DNA sequence data for Mediterranean corallines were published in 2009 and unraveled the presence of Corallina caespitosa, an articulated species now known to be widespread and formerly confused with Ellisolandia elongata. Overall, Lithophyllum is the genus that has been most studied by an integrative approach combining morphological and molecular data. Such studies revealed in the Mediterranean a striking case of cryptic diversity, a phenomenon that is now known to be pervasive in coralline algae: the Lithophyllum stictiforme complex. Two recent studies showed that this alga, previously known as a single species, represents a complex of at least 11 different cryptic species (of which not less than 8 present on the French coasts). Lithophyllum incrustans, the type species of Lithophyllum, has been shown to be primarily an infralittoral species, despite of frequent reports in mesolittoral habitats. Mediterranean populations of Lithophyllum byssoides, known as builders biogenic rims, are likely to represent a separate species from Atlantic populations. Molecular data also allowed the phylogenetic assessment of Pneophyllum cetinanensis, the first coralline alga discovered in freshwater. Additional molecular data led to new records for the Mediterranean and to an improved biogeographic circumscription for several species, especially of the genus Mesophyllum and Phymatolithon. The current number of 59 coralline species recorded for the Mediterranean should not be considered a definitive estimate and new species can be expected to be discovered in the near future (particularly in the genera Lithophyllum and Neogoniolithon)
Biodiversity associated with Mediterranean fucalean forests and mechanisms regulating it: an assessment of the current knowledge
No full textForests formed by fucalean brown algae of the Cystoseira s. l. complex (genera Cystoseira, Ericaria and Gongolaria) are a typical feature of shallow Mediterranean seascapes. These seaweeds play a key role in shaping biodiversity on shallow rocky bottoms; due to their highly branched morphology, they increase tridimensionality and structural complexity of benthic assemblages, providing a high diversity of habitats for many sessile and mobile organisms. Studies concerning the biodiversity of Cystoseira s. l. forests have largely focused on the associated macroalgal and invertebrate assemblages. Inventories presented in these studies usually consist of floristic and/or faunal lists based on traditional morphological identifications. The majority of them was carried out at local spatial scales, i. e. an individual site or a few sites in a geographic area; Ericaria crinita is the species for which the largest sampling effort and geographical coverage is currently available. To date, information concerning the microalgal assemblages associated with Cystoseira s. l. is completely lacking. Knowledge of the microbiomes associated with Cystoseira s. l. is also extremely limited, despite of the role plaid by this component on the well-being of the macroalgae. Several hundreds of macroalgal and invertebrate taxa have been reported in association with Cystoseira s. l. species (up to 597 taxa recorded for Ericaria corniculata and E. brachycarpa),
with substantial differences among species. For individual species, significant variation in associated biodiversity has been detected at regional scale. Experimental studies demonstrated that loss of Cystoseira s. l. canopies involves major changes in the structure of benthic assemblages. Density of the canopy and size of Cystoseira s.l. patches directly affect the number of associated benthic taxa. Future investigations should increase the number of Cystoseira s. l. taxa sampled and extend the geographic coverage (especially to eastern Mediterranean regions). Molecular data such as eDNA sequences should be incorporated in future studies. Finally, the microbiomes associated to Cystoseira s. l. forests should be investigated with more detail
Can epiphytic vegetation be used as an indicator of the recovery state of Cystoseira s.l. forests? A study carried out along the Conero Riviera (N Adriatic).
No full textNew discoveries reveal unexpectedly wide taxonomic diversity and call for a new classification of the green algal family Prasiolaceae (Trebouxiophyceae)
No full textAlgal lineages with small size and low morphological complexity are typically among the most difficult to resolve taxonomically. They are often characterized by high levels of cryptic diversity and environment-driven plasticity that complicate species recognition. Their full taxonomic diversity is even more difficult to unravel when their evolution has also resulted in great ecological diversity, encompassing many different habitats including unusual ones. An example of this case is the Prasiolaceae, a family of filamentous, leafy and packet-like green algae occurring in marine, freshwater and terrestrial environments. They are well known for their preference for habitats subject to high loads of organically derived nutrients, mainly in the form of seabird guano found in upper littoral habitats. In recent years, new surveys and new molecular phylogenetic studies have produced the surprising discovery of many new lineages, revealing an unexpected high taxonomic diversity. DNA sequence data obtained from cultured strains called for the description of several new genera and species. Prasiola, type genus of the family, was subjected to a major rearrangement. The genus was shown to be polyphyletic, which required its splitting into four genera: the real Prasiola (in which the type species Prasiola crispa belongs), Eaprasiola, Mariprasiola and Vittaprasiola. The marine species of this grouping, classified in the genus Mariprasiola, represent a remarkable case: they exhibit clear morphological and life history differences, although sequences of the most common markers used for species delimitation are identical. Conversely, in the genus Vittaprasiola DNA sequence divergence demonstrates the existence of cryptic entities that require separation at species level. Further studies of this group should expand the body of molecular markers available and, in combination with fieldbased studies making use of environmental DNA, might reveal an even higher phylogenetic and taxonomic diversity
New discoveries in the family Prasiolaceae (Trebouxiophyceae) and a new taxonomic rearrangement of the genus Prasiola
No full textDNA cloning demonstrates high genetic heterogeneity in populations of the subaerial green alga Trentepohlia (Trentepohliales, Chlorophyta)
No full textMats of the green alga Trentepohlia, a genus widely distributed in the tropics as well as temperate regions,
have always been perceived as homogeneous (i.e., formed by only one species). As such, their general
nature and specific feature play a supportive role in the species delimitation. However, the presence of
morphologically dissimilar thalli was observed under the light microscope and when cultivating a piece of a
single mat. To address this, we performed DNA cloning of the rbcL gene on mat fragments of T. abietina, T. annulata, T. jolithus and T. umbrina sampled in Europe to reveal if they are composed of one or more species. We revealed that more Trentepohlia haplotypes may coexist in a single mat. In consideration of this, we conclude that the use of material isolated in unialgal culture will be almost mandatory for a taxonomic reassessment of this complicated genus. Another direct implication of this problem is that herbarium specimens consisting of field-collected material should not be used for direct sequencing. We further hypothesize the reasons why multiple haplotypes of Trentepohlia occur more frequently in the tuft-like mats. Possibly, fragments and/or cells of other microalgae, including other species of Trentepohlia, might be retained in such mats more easily than in the crustose trentepohlialean mats
Osservazioni su una prateria di Halophila stipulacea (Forssk.) Aschers. (Hydrocharitaceae) nel Mar Tirreno Meridionale
No full textA Halophila stipulacea meadow was observed near Vulcano Island harbour (Aeolian Islands, Italy). This is the first report of such species in the Western Mediterranean Sea. It covers about two hectares of substrate ranging from 3 to 27 meters depth. Data on H. stipulacea phenology and epiphytic flora are also given
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