North Atlantic Rhodolith Beds

Aggregations of living unattached corallines, previously often referred to as nodules, were given the name rhodoliths by Bosselini and Ginsburg ( 1971 ). Adey and MacIntyre ( 1973 ) provided an early discussion of their genesis and distribution. Such aggregations have long been known as maerl in the North East Atlantic, a Breton term for unattached thalli that lack a shell or pebble core (Irvine and Chamberlain 1994 ). Here, we provide an overview of rhodolith/maerl occurrence in the colder/temperate waters of the North Atlantic and summarize the distribution, species composition, biodiversity and ecological importance of these habitats

Analysis of the cox2-3 spacer region for population diversity and taxonomic implications in rhodolith-forming species (Rhodophyta: Corallinales)

Coralline red algae demonstrate phenotypic plasticity related to environmental factors, rendering their identification difficult. The cox2-3 spacer is a mitochondrial marker widely used for phylogeographic studies and discrimination between closely related species in red algae; however, cox2-3 spacer sequence data for coralline algae are still limited. In this study we substantially increase the number of cox2-3 spacer sequences available for coralline algae, exploring their usefulness for different types of molecular investigations in coralline algae (DNA barcoding and phylogeography), with emphasis on rhodolith-forming species. Specimens from North Atlantic Europe, the Caribbean region and the Gulf of California (Mexico) were sequenced and two datasets were built, one for the subfamily Lithophylloideae and one for the Melobesioideae. Our results suggest the utility of cox2-3 spacer as barcoding marker for coralline algae with a slight variation in the barcode gap depending in the way gaps in the alignment are treated. Analyses on both datasets found a barcode gap or separation between intra and interspecific divergence (p distance and ABGD analysis) while some inconsistencies were evident when the results were compared with morphology-based classification. Using the cox2-3 spacer region, the morphospecies Lithophyllum margaritae from the Gulf of California revealed the existence of two well-supported clades, with the possibility of respectively five and two additional species; haplotype networks for Phymatolithon calcareum and P. purpureum revealed similar patterns when Mediterranean and NW Europe specimens were analysed, and P. calcareum was shown to consist of a single population in NW Europe. Based on our analyses the marker cox2-3 spacer has strong potential applications for studies of phylogeography and DNA barcoding in coralline algae after understanding its variation

Distribution and genetic variation of two bioconstructor coralline algae (Lithophyllum byssoides (Lamarck) Foslie and L. stictaeforme (Areschoug) Hauck) along the Italian coasts

Coralline red algae represent a worldwide component of hard-bottom coastal communities, where they play a key role in many ecological processes. Some species are ecosystem engineers that produce biogenic platforms, reefs and other calcified structures providing a wealth of habitats for many other species, especially in temperate seas. In the Mediterranean Sea these bioconstructions are widespread and occur both in the littoral zone (trottoirs of Lithophyllum byssoides) and in the sublittoral zone (coralligenous bottoms, where coralline algae are one of the main constituents). A detailed knowledge of their distribution and composition is essential for their conservation, but molecular data assessing taxonomic identity and population structure in corallines are extremely limited. The distribution and genetic variation in two important bioconstructor corallines, Lithophyllum byssoides and L. stictaeforme (Corallinales, Corallinaceae) are investigated using sequences of the plastid psbA gene and mitochondrial cox2,3 spacer. Populations of L. byssoides occur on all parts of the Italian coastline where rocky shores exist and the molecular data show that Mediterranean populations of this species represent a sister lineage to Atlantic populations. L. stictaeforme is widespread along the Italian shores, particularly along the Ligurian and Tyrrhenian sides. In molecular phylogenies Mediterranean populations of L. stictaeforme form a well-supported clade, to which North Atlantic Lithophyllum spp. are the closest relatives. Overall the results indicate a high genetic variability in these species, with the possible existence of cryptic species

Distribution and genetic variation of two bioconstructor coralline algae (Lithophyllum byssoides (Lamarck) Foslie and L. stictaeforme (Areschoug) Hauck) along the Italian coasts

Coralline red algae represent a worldwide component of hard-bottom coastal communities, where they play a key role in many ecological processes. Some species are ecosystem engineers that produce biogenic platforms, reefs and other calcified structures providing a wealth of habitats for many other species, especially in temperate seas. In the Mediterranean Sea these bioconstructions are widespread and occur both in the littoral zone (trottoirs of Lithophyllum byssoides) and in the sublittoral zone (coralligenous bottoms, where coralline algae are one of the main constituents). A detailed knowledge of their distribution and composition is essential for their conservation, but molecular data assessing taxonomic identity and population structure in corallines are extremely limited. The distribution and genetic variation in two important bioconstructor corallines, Lithophyllum byssoides and L. stictaeforme (Corallinales, Corallinaceae) are investigated using sequences of the plastid psbA gene and mitochondrial cox2,3 spacer. Populations of L. byssoides occur on all parts of the Italian coastline where rocky shores exist and the molecular data show that Mediterranean populations of this species represent a sister lineage to Atlantic populations. L. stictaeforme is widespread along the Italian shores, particularly along the Ligurian and Tyrrhenian sides. In molecular phylogenies Mediterranean populations of L. stictaeforme form a well-supported clade, to which North Atlantic Lithophyllum spp. are the closest relatives. Overall the results indicate a high genetic variability in these species, with the possible existence of cryptic species