MOLECULAR DELINEATION OF SPECIES AND SPECIES RELATIONSHIPS IN THE REDALGAL AGAROPHYTES GRACILARIOPSIS AND GRACILARIA (GRACILARIALES)

Delineation of species in the economically important agarophyte genera Gracilaria and Gracilariopsis has proven extremely difficult using av ailable morphological characteristics. In this study, we examine the u sefulness of two transcribed spacers for molecular systematic studies of these genera. The polymerase chain reaction was used to amplify the internal transcribed spacers (ITSs) and the intervening 5.8S ribosoma l DNA of the nuclear ribosomal repeat region. In addition, a plastid s pacer region and flanking regions of coding genes were amplified from the RUBISCO operon. Both regions were sequenced for individuals and po pulations of Gracilariopsis lemaneiformis (Bory) Dawson, Acleto, et Fo ldvik to determine the usefulness of these spacers in delimiting popul ations. These studies reveal that there is as much variation among ind ividuals of a population as there is between individuals ofgeographica lly separate populations. In addition, the ITS spacer regions were com pared between different species of Gracilariopsis and Gracilaria. The nuclear ITS spacer region is conserved at a species level in both gene ra and provides phylogenetically informative characters that can be us ed to examine species interrelationships among relatively closely reba ted taxa. However, because of the difficulties of aligning this entire region among species from the two genera, the ITS region is not usefu l for examining intergenera relationships. ITS interspecies sequence c omparisons indicate that Gracilariopsis lemaneiformis from California is significantly different from G. lemaneiformis from China and that a species of Gracilariopsis from Peru is more closely related to G. lem aneiformis from North Carolina than it is to the other Gracilariopsis species examined. In addition, these studies indicate that Gracilaria chilensis Bird, McLachlan, et Oliveira from New Zealand and Gracilaria tenuistipitata Chang et Xia from southeast Asia are as closely relate d as are Gracilaria verrucosa (Hudson) Papenfuss, G. pacifica Abbott, and Gracilaria robusta Kylin. Phylogenetic analysis of aligned plastid spacer sequences from Gracilaria and Gracilariopsis taxa provide simi lar conclusions about species relationships.