MOLECULAR DELINEATION OF SPECIES AND SPECIES RELATIONSHIPS IN THE RED ALGAL AGAROPHYTES GRACILARIOPSIS AND GRACILARIA (GRACILARIALES)¹

Abstract

Delineation of species in the economically important agarophyte genera Gracilaria and Gracilariopsis has proven extremely difficult using available morphological characteristics. In this study, we examine the usefulness 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 ribosomal DNA of the nuclear ribosomal repeat region. In addition, a plastid spacer region and flanking regions of coding genes were amplified from the RUBISCO operon. Both regions were sequenced for individuals and populations of Gracilariopsis lemaneiformis (Bory) Dawson, Acleto, et Foldvik to determine the usefulness of these spacers in delimiting populations. These studies reveal that there is as much variation among individuals of a population as there is between individuals of geographically separate populations. In addition, the ITS spacer regions were compared between different species of Gracilariopsis and Gracilaria. The nuclear ITS spacer region is conserved at a species level in both genera and provides phylogenetically informative characters that can be used to examine species interrelationships among relatively closely related taxa. However, because of the difficulties of aligning this entire region among species from the two genera, the ITS region is not useful for examining intergenera relationships. ITS interspecies sequence comparisons 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. lemaneiformis 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 related 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 similar conclusions about species relationships.

Molecular and Ecological Evidence for Species Specificity and Coevolution in a Group of Marine Algal-Bacterial Symbioses

“…was 4 to 7%, a level of variation similar to those observed among other algal ITS sequences used successfully for phylogenetic analysis (13,24,29). A limitation of the analysis of ITS sequence variation is the difficulty in defining suitable outgroups (relatives close enough that confident alignment is possible) for phylogenetic analyses.…”

“…The ability to unambiguously align the six algal host ITS sequences used in this study implies, based on the low level of sequence divergence among taxa, that a relatively recent radiation of these algal taxa has occurred. The ITS region is transcribed but then spliced out of mature rRNA during processing, leading to higher rates of evolution in this region relative to the rDNA (7,24). This increase in sequence variability limits phylogenetically informative comparisons of the ITS to closely related taxa (intergeneric comparisons or very closely related genera) (7,24).…”

“…Total DNA was isolated from galls on P. filiformis (Lufenholtz population) and P. decipiens and from the thalli of P. filiformis (Lufenholtz population), P. filiformis (Carmel population), P. decipiens, P. lyalli, and Prionitis sp. (Mission Bay) by using Chelex-100 extraction (Bio-Rad, Richmond, Calif.) as described previously (6,24). Amplification of 16S rDNA gene sequences and algal ITS sequences by PCR, cloning, and initial screening of amplification products was also carried out as described previously (6,24).…”

“…(Mission Bay) by using Chelex-100 extraction (Bio-Rad, Richmond, Calif.) as described previously (6,24). Amplification of 16S rDNA gene sequences and algal ITS sequences by PCR, cloning, and initial screening of amplification products was also carried out as described previously (6,24). Plasmid DNA was prepared for sequencing by Wizard miniprep following the manufacturer's recommendations (Promega, Madison, Wis.).…”

Inferências filogenéticas na ordem Fucales (Phaeophyceae), com ênfase no gênero Sargassum C. Agardh do Atlântico Sul

“…A região espaçadora intergênica (rbcLS) tem sido freqüentemente empregada em análises moleculares em representantes das algas vermelhas na comparação de populações isoladas de diferentes regiões biogeográficas e/ou em reconstruções filogenéticas inter e intra específicas devido a alta variabilidade nessa região (Maggs et al 1992, Goff et al 1994, Zucarello & West 1997Milstein 2006).…”