GLOBAL PHYLOGEOGRAPHY IN THE COSMOPOLITAN SPECIES CLADOPHORA-VAGABUNDA (CHLOROPHYTA) BASED ON NUCLEAR RDNA INTERNAL TRANSCRIBED SPACER SEQUENCES

Phylogeographic relationships were inferred from nuclear rDNA internal transcribed spacer (ITS) sequences among ten biogeographic isolates o f the cosmopolitan green alga Cladophora vagabunda from the Atlantic a nd Pacific Oceans as well as the Red Sea and SW Australia. Representat ives of the closely related C. albida/sericea clade were used as outgr oup and root, based on previous studies using 18S rDNA. High bootstrap values and negative g(1)-statistics revealed a strong phylogenetic si gnal regardless of assumption sets that included or excluded alignment -gaps in the analyses. The two main lineages found within the C. vagab unda complex are hypothesised to have shared a common Pacific ancestor , based on the basal position of Indo-West Pacific isolates relative t o the outgroup. It is concluded that C. vagabunda represents the predi cted intermediate case between ancient tropical species that exhibit s trong vicariance imprints and recent, cold-temperate to boreal Lineage s that do not.