A molecular investigation of polymorphism in the North Atlantic red alga Chondrus crispus (Gigartinales)*

Abstract

Seven samples of Chondrus crispus Stackhouse, representing widely contrasting forms from both sides of the North Atlantic, were compared by restriction digestion of their plastid DNA. The similar banding patterns confirmed that the seven forms were conspecific and distinct from Chondrus ocellatus Holmes f. ocellatus from Japan, used as an outgroup. Nucleotide sequences of the internal transcribed spacers (ITS1 and ITS21 and the intervening 5.8s rRNA gene of the nuclear rRNA operon were investigated as a potential indicator of genetic divergence among morphological variants of C. crispus. The combined ITS regions were relatively short in Chondrus (between 719 and 731 base pairs [bpl in C. crispus and 724 bp in C. ocellatus f. ocellatus), and the sequence of the 5.8s rDNA fragment (152 bp) was identical in both species. In the aligned ITS regions, there were 0-18 base pair differences (0-2.18% divergence) in paitwise comparisons of the seven forms of C. crispus but no consistent pattern of variation according to gross morphology or geographic origin. However, the ITS sequence differed at 41-54 sites (6.22-7.56%) between C. crispus and C. ocellatus f. ocellatus, again illustrating the genetic distinctiveness of the latter species.

Phylogeographic analysis reveals a deep lineage split within North Atlantic Littorina saxatilis

“…Haplogroup A appears to have survived the LGM south of the Laurentide ice sheet [2,11], and Skyride analysis indicates that effective population size remained relatively high throughout the LGM (figure 3). Haplogroup J probably survived in a northern location, providing additional evidence for a periglacial refugium in North Atlantic Canada [3,7,[11][12][13][14]. Since the termination of the LGM (approx.…”

“…In the eastern North Atlantic, there is evidence for multiple southern glacial refugia, which buffered extinctions and allowed for northward recolonization events during interglacial periods [6][7][8][9]. In the western North Atlantic, regional extinctions were common among rocky shore species, because most of the suitable habitat was covered by the Laurentide ice sheet [2,8,10], although some species were able to survive in southern [2,11] or northern refugia [3,7,[11][12][13][14]. As a result, many of the current western North Atlantic rocky shore fauna (including the intertidal snails Littorina obtusata and Nucella lapillus) recolonized the region following the LGM, whereas other species (such as Semibalanus balanoides and Mytilus edulis) appear to have persisted in western North Atlantic refugia [2][3][4]8,10].…”

BIOGEOGRAPHYOF BATRACHOSPERMUM GELATINOSUM (BATRACHOSPERMALES, RHODOPHYTA) IN NORTH AMERICA BASED ON MOLECULAR AND MORPHOLOGICAL DATA1

“…Bakker et al 1992, Kooistra et al 1992, van Oppen et al 1995, Chopin et al 1996, Lindstrom et al 1996. The ribosomal DNA (rDNA) internal transcribed spacer (ITS) 1 and 2 sequences have been shown to be variable among and within species and have been proposed to be useful for study of infraspecific variation due to the apparently high evolutionaly rates of these regions (Steane et al 1991).…”

Investigations on Reproductive Affinities in Red Algae

“…Cystocarps were produced on the female from the Gulf of St. Lawrence in the presence of the male from the Bay of Fundy, whereas no reaction was seen in the reciprocal cross. Their different temperature response may maintain "habitat segregation," and as a result, may restrict the genetic exchange between these localities, though Chopin et al (1996) suggested low genetic diversities of Chondrus crispus around the Atlantic Canada. The difference in the upper or lower temperature for maturation within the same species, which have been reported in many kinds of red algae (e.g., Molenaar and Breeman, 1994;Molenaar et al, 1996;West et al, 1996), may also be an important factor for ecological isolation.…”