Abstract:Chromosome numbers of 1 N=24 were determined for three species of Gracilaria (G. Gracilariopsis ( G. lemaneiformis and G. tenuifrons) were found to have slightly larger 2 C genome contents of 0.42-0.47 pg. No intraspecific variation in 2 C genome sizes was found in regional populations of Gracitaria tikvahiae and Gracilariopsis tenuifrons.
“…In the present study, all European (including Mediterranean samples), Argentinian, and Namibian samples were confirmed to form a homogenous G. gracilis group on the basis of rDNA ITS sizes. This group includes Grucilariu gracilis from Cape Gris-Nez (northern France), which is reported to have an anomalous chromosome number of n = 16-18 (Godin et al 1993, Kapraun 1993 instead of the typical number of n = 24 found in other populations of G. gracilis (Bird andRice 1990, Kapraun 1993). In contrast, our results on rDNA ITS sizes show that the Grucilariu sample from Japan initially ascribed as G. gracilis is different from our other samples of G. gracilis.…”
Four single locus microsatellites identified in the red alga Gracilaria gracilis (Stackhouse) Steentoft, Irvine, et Farnham (Rhodophyta) were examined for allelic diversity at different spatial and taxonomic levels. First, because simple morphological diagnostic characters are often missing within the Gracilariaceae, we developed a simple and rapid method based on rDNA ITS size variation in order to verify the taxonomic status of the samples used in this study. All European (including Mediterranean samples), Argentinian, and Namibian samples used in our study were confirmed to be a homogenous G. gracilis group. By contrast, our results on rDNA ITS sizes showed that Gracilaria from Japan, initially identified as G. gracilis, was different from the rest of the G. gracilis group. Secondly, microsatellite polymorphism and conservation at the species level was tested on the worldwide collection of G. gracilis and within a single population. The loci Gv1AAG and Gv1AAC showed no allelic variation, whereas two others, Gv1CT and Gv2CT, were highly polymorphic. All microsatellite loci were conserved within G. gracilis, except in the sample from Japan. The taxonomic status of G. gracilis from Japan is thus questionable. This study revealed a high level of within‐population polymorphism (52 alleles for Gv1CT and 12 for Gv2CT). Moreover, the combination of these two loci was shown to be very powerful for identifying individuals within a population, that is, 93% of the individuals were characterized by a unique genotype. Finally, conservation of the four loci was tested in taxonomically related species of Gracilaria (G. chilensis, G. pacifica, and G. tikvahiae) and two Gracilariopsis species (Gs. sp. and Gs. longissima). The results suggest that the polymorphic locus Gv2CT may provide a valuable genetic marker within the different species of the Gracilariaceae.
“…In the present study, all European (including Mediterranean samples), Argentinian, and Namibian samples were confirmed to form a homogenous G. gracilis group on the basis of rDNA ITS sizes. This group includes Grucilariu gracilis from Cape Gris-Nez (northern France), which is reported to have an anomalous chromosome number of n = 16-18 (Godin et al 1993, Kapraun 1993 instead of the typical number of n = 24 found in other populations of G. gracilis (Bird andRice 1990, Kapraun 1993). In contrast, our results on rDNA ITS sizes show that the Grucilariu sample from Japan initially ascribed as G. gracilis is different from our other samples of G. gracilis.…”
Four single locus microsatellites identified in the red alga Gracilaria gracilis (Stackhouse) Steentoft, Irvine, et Farnham (Rhodophyta) were examined for allelic diversity at different spatial and taxonomic levels. First, because simple morphological diagnostic characters are often missing within the Gracilariaceae, we developed a simple and rapid method based on rDNA ITS size variation in order to verify the taxonomic status of the samples used in this study. All European (including Mediterranean samples), Argentinian, and Namibian samples used in our study were confirmed to be a homogenous G. gracilis group. By contrast, our results on rDNA ITS sizes showed that Gracilaria from Japan, initially identified as G. gracilis, was different from the rest of the G. gracilis group. Secondly, microsatellite polymorphism and conservation at the species level was tested on the worldwide collection of G. gracilis and within a single population. The loci Gv1AAG and Gv1AAC showed no allelic variation, whereas two others, Gv1CT and Gv2CT, were highly polymorphic. All microsatellite loci were conserved within G. gracilis, except in the sample from Japan. The taxonomic status of G. gracilis from Japan is thus questionable. This study revealed a high level of within‐population polymorphism (52 alleles for Gv1CT and 12 for Gv2CT). Moreover, the combination of these two loci was shown to be very powerful for identifying individuals within a population, that is, 93% of the individuals were characterized by a unique genotype. Finally, conservation of the four loci was tested in taxonomically related species of Gracilaria (G. chilensis, G. pacifica, and G. tikvahiae) and two Gracilariopsis species (Gs. sp. and Gs. longissima). The results suggest that the polymorphic locus Gv2CT may provide a valuable genetic marker within the different species of the Gracilariaceae.
“…Conspicuous exceptions include Acanthophora spicifera with 2 n = 64 and 2C = 1.1 pg, and Antithamnion villosum with 2 n = 48 and 2C = 2.0 pg. Clearly, in some genera, polyploidy events were followed by chromosome reorganization, including fission/fusion processes ultimately resulting in aneuploidy as described for species of the Rhodomelaceae genus Polysiphonia ( Kapraun 1993 a ). Fig.…”
Section: Resultsmentioning
confidence: 96%
“…No new nuclear DNA content estimates are available for this order, but previous data indicate that nuclear genome sizes are small (0.3–0.5 pg) ( Kapraun 1993 b , 2005 ). The Gracilariales, unlike the Gelidiales, is noted for genome size constancy, with all species of Gracilaria investigated having identical 2C DNA contents of 0.4 pg and chromosome complements of 2 n = 48 ( Kapraun and Dutcher 1991 ; Kapraun 1993 a ). Species of the closely related Gracilariopsis ( Bird et al .…”
Section: Resultsmentioning
confidence: 99%
“…Polyploidy has been reported widely in the Rhodophyta ( Cole 1990 ; Kapraun 2005 ), especially in the Ceramiales, which have both the largest nuclear genomes and the highest chromosome numbers ( Kapraun 1993 a , 2005 ; Kapraun and Dunwoody 2002 ). For a recent review of concepts associated with adaptations and genetic variability associated with hybridization and polyploidy in algae, see Coyer et al .…”
This paper compiles and discusses all currently available nuclear genome size data for red algae in relation to their most recent taxonomic classification.
“…Despite its reinstatement, Hydropuntia has been considered a synonym of Gracilaria by some phycologists (e.g., Abbott et al 1991;Gargiulo et al 1992, Abbott 1995, Plastino & Oliveira 1997, Bellorin et al 2002, Lyra et al 2015, Iha et al 2018. Still others recognized it as a distinct genus, either as Polycavernosa (e.g., Chang & Xia 1963;Xia [Bangmei] and Abbott 1985;Fredericq & Norris 1985) or Hydropuntia (e.g., Xia & Abbott 1987;Fredericq & Hommersand 1990b;Kapraun 1993;Wynne 1989;Conklin et al 2014, Yang & Kim 2015Núñez-Resendiz et al 2015), or as a subgenus of Gracilaria (e.g., Tseng & Xia 1999).…”
The Gracilariales is a red macroalgal order and the main global source of the economically important agar, a marine phycocolloid. Independent comparative morphological and molecular phylogenetic studies over the last 20 years have revealed the existence of seven major clades recognizable as distinct genera. Of these major clades only four free-living genera have been widely accepted taxonomically: Curdiea, Melanthalia, Gracilariopsis, and Gracilaria. Three other clades comprise the reinstatement of the genus Hydropuntia and the proposal of two new genera, Agarophyton and Crassa, described herein. Based on new rbcL DNA sequences, and along with a reassessment of published comparative morphological and molecular phylogenetic studies, we argue that the latter three genera represent distinct evolutionary lineages in the Gracilariaceae, and propose a new classification for the order Gracilariales. Our new proposal incorporates the most current understanding of the evolutionary history of the order, establishes a natural and stable classification system, and provides the basis for the recognization of intra-family ranks. Our classification scheme reconciles all molecular phylogenetic studies published to date.
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