A revision of Cladophoropsis borgesen (Siphonocladales, Chlorophyta)

A reassessment of the genus Cladophoropsis results in the recognition of six morphospecies: C. macromeres, C. magna, C. membranacea, C. philippinensis, C. sundanensis and C. vaucheriiformis. The emended genus Cladophoropsis is characterized by mat- or cushion-forming plants attached to the substratum by tenacular cells or by rhizoids that sprout from the proximal pole of the basal cells or are formed in any part of the thallus, cell division by centripetal wall ingrowths or occasionally segregative, cells producing a single lateral but older cells occasionally producing secondary laterals, cross walls at the base of the laterals either absent or their formation markedly delayed and reinforcement of the thallus by entangling of the filaments or by anastomosis of adjacent filaments by tenacular cells. The different species are distinguished from each other based on thallus structure, mode of cell division, organization of branch systems, mode of thallus attachment and reinforcement, shape and dimensions of the cells and shape of the crystalline cell inclusions. Twenty Cladophoropsis species are excluded from the genus, including the widely distributed Indo-Pacific species C. herpestica and C. javanica, which have been found to be unrelated to other Cladophoropsis species but instead allied with species of the Cladophora section Longi-articulatae. Phylogenetic studies based on molecular data have furthermore demonstrated that Cladophoropsis is closely related to Boodlea, Phyllodictyon, Struveopsis, Struvea and Chamaedoris and that the genus probably does not form a natural group within this genus complex. Morphologically this can be illustrated by a number of Cladophoropsis species (e.g. C. magna and C. membranacea) crossing generic boundaries by sharing common features with Chamaedoris, Boodlea, Phyllodictyon and Struvea. For the benefit of taxonomic stability, Cladophoropsis is presently maintained, awaiting additional molecular evidence