Systematic significance of spore size in the Florideophyceae (Rhodophyta)

Abstract

Size variation in 92 populations of carpospores and tetraspores representing 57 tropical benthic algal taxa has been investigated. One size class predominates in each sample, but there is considerable variation in spore size in all populations of carpospores and tetraspores. Spore size is therefore not a useful taxonomic character at the species level despite the considerable range within the division Rhodophyta. Nevertheless, advanced Florideophyceae form chiefly tetrahedral tetrasporangia with large spores; less advanced groups generally form cruciate or zonate tetrasporangia with smaller spores. Carpospores are generally larger than tetraspores. The mucilage sheaths of a representative number of species comprising 56 populations of carpospores and tetraspores were studied. The diameter of the spore with its mucilage sheath is frequently twice the diameter of the spore excluding the sheath.