A taxonomic, phylogenetic and biogeographic study of the genus Acanthophora (Rhodomelaceae, Rhodophyceae)
Hitipeuw, C. (1996). A taxonomic, phylogenetic and biogeographic study of the genus Acanthophora (Rhodomelaceae, Rhodophyceae). MSc Thesis. VUB: Brussel. 61 pp. |
| Available in | Author | | Document type: Dissertation
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| Abstract | Global distribution of 6 Acanthophora species; viz. A. aokii, A. dendroides, A. muscoides, A. najadiformis, A. ramulosa, and A. spicifera shows a discontinuous pattern. Although there are widely distributed species (A. muscoides and A. spicifera), a separated distribution of other species occur in the Pacific (A. aokii), Indian Ocean (A. dendroides), the Mediterranean and the Red Sea (A. najadiformis), and the Atlantic region (A. ramulosa). In this study a cladistic analysis using PAUP (Phylogenetic Analysis Using Parsimony) program is carried out for 6 Acanthophora species using 18 characters. The determination of species affinities are based primarily on morphological distinguishable characters. However, the species are morphologically poorly defined and show few distinct character states, hence more emphasis was placed on the development of spinous features either in relation to vegetative or reproductive structures. The result gives one most parsimonious tree (tree length 49 steps, Consistency Index = 0.86). The topology of the obtained phylogenetic tree gives some information about the historical background of the distribution of the species. It may be suggested that the separated occurrence of closely related algal species in recent times, supports the hypothesis of a common distribution area of those species or their ancestor in the past. In the phylogenetic tree (cladogram), A. aokii is grouped separately from all others and has a close relation to the outgroup Chondria. It seems to be the most primitive species of Acanthophora. This may suggest that the genus Acanthophora originated from the Pacific region. Additionally, the isolated position of A. dendroides on the tree suggests that this species belongs to Indo-Pacific algal flora. The subsequent cladogeneses and geographical segregation of A. aokii, A. dendroides and A. ramulosa and possibly also A. najadiformis suggest a strong Tethyan imprint, although the presence of A. najadiformis in the Mediterranean can also be caused by a secondary introduction from the Atlantic. The two worldwide distributed species (A. spicifera and A. muscoides) have a biogeographical history that is more difficult to resolve, and may probably have been affected by a strong influence of dispersal events and migration. It is therefore concluded that the discontinuous distribution of the species can be explained to be assembled in response subsequently to vicariance events, in particular by the closure of the Tethys Sea and the relative uplift of continents, without excluding the possibility of additional transoceanic dispersal. |
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