Taxonomy, molecular biodiversity and ecology of coralline algae (Corallinales: Rhodophyta), with special emphasis on maerl-forming species

Abstract

Coralline algae are important biological and ecological components in coastal environments around the world, and in this study a comprehensive molecular and ecological analysis of the group was performed. Questions related to molecular diversity, species delimitation and the diagnosis of morphological features were investigated. In Chapter 2, the inclusion of rhodolith-forming species for the first time in the phylogeny of the order Corallinales showed that a monophyletic group of samples within the genus Neogoniolithon was associated with this feature. So, there is a possibility that the rhodolith habit is a combination of environmental conditions and genotypic control. In Chapter 3 it was shown that there are three common species of Lithophyllum distributed in Europe, which were identified as Lithophyllum incrustans, L. dentatum and L. hibernicum using sequences obtained from type specimens. Morphological characteristics were observed and described for each of the three species. Nine other species were found and the names for the entities will require additional studies. In Chapter 4 the new genus Chamberlainia was described using molecular affinities and morphological features; it was separated from Phymatolithon using sequence data. The phylogenetic position and taxonomy of Chamberlainia are discussed in context with representatives of related genera in the family Hapalidiaceae. In Chapter 5 the cox 2-3 marker was shown to be useful to separate taxa in the order Corallinales. Nevertheless, in some cases the taxonomic level at which the separation is established is not clear (e.g., species? Populations? Genus?). This marker was also useful for population level diversity in Phymatolithon calcareum, Chamberlainia purpurea and Lithothamnion corallioides. In Chapter 6 three maerl beds of the western Irish coast were examined and it was found that rhodoliths forming the three beds studied (Mukinish Inlet, Carraroe Bay and Mannin Bay) differed in sizes, coverage, reproduction and shape. Observations conducted over a year at Mukinish Inlet showed differences only in the reproductive phenology of the species forming the bed (Chamberlainia purpurea). Even the composition in coralline species was different in the three sites. The information acquired herein is useful for conservation strategies, ecological monitoring or even to study further questions related with molecular diversity in the group.