Allozyme variation was examined in 7 species and 4 varieties of Caulerpa sampled from the central Great Barrier Reef region. The species examined were: Caulerpa racemosa, (vars imbricata, laetevirens, and racemosa, and a peltate morph of C. racemosa), C. cupressoides, C. lentillifera, C. peltata, C. serrulata, C. sertularioides, and C. taxifolia.
Differences were examined between species and between populations of the same taxon sampled from different geographical locations, and typically included fixed gene differences (no alleles found in one taxon shared by the other taxon) at two or more loci.
Cluster and cladistic analyses were carried out. Eight of 13 plants identified initially as C. serrulata were distinguished at several loci, indicating the presence of an undetermined cryptic taxon.
Population genetic analysis of polymorphisms, which occurred in some taxa, demonstrated strong spatial differentiation among some populations and significant but variable degrees of clonality and/or inbreeding within these populations.
Allozymes proved to be a useful tool for defining species boundaries and investigating population structure in Caulerpa, but not for determining phylogenetic relationships within the genus.
Collection locations: Shelly Beach (SB), Cape Pallarenda (CP), Kissing Point (KP), The Strand (ST), The Breakwater at Townsville Harbour (EB), Horseshoe Bay on Magnetic Island (HB), Lodestone Reef (LR).