Description:
The charophytes, or stoneworts, are a group of green algae with six extant genera in one family, distributed worldwide in freshwater ponds and lakes. They are among the green algal groups most closely related to land plants and exhibit a complex thallus, with multinucleate internodal cells joined at nodes comprising smaller, uninucleate cells giving rise to whorled branchlets. Two genera (Chara, Nitella) contain most of the described species, with a third (Tolypella) containing several dozen taxa. The remaining genera have one or a few species. Reproduction is oogamous, with sperm and eggs produced in separate multicellular structures. The thallus is haploid; the zygote is the only diploid cell in the life cycle, and meiosis is followed by the development of a resistant spore. Thalli and spores are often encrusted with calcium carbonate. Such spores are abundant in the fossil record of the Charales, which extends to the Upper Silurian, and many genera and families have become extinct. These algae provide important ecosystem services, for example, as colonizing species, as biological agents for producing water clarity, or as the base of the food web. Charophytes are important for the study of evolution of embryophyte development, growth meristems, and cell biophysics. As one of the green algal groups most closely related to land plants, the rich charophyte fossil record may reveal clues regarding the earliest algae that invaded the land.
Description:
This study of Northern Territory charophytes documents 22 species in 3 of the genera in tribe Chareae, family Characeae, including 15 previously described species (Chara benthamii, C. erythrogyna, C. globularis, C. karolii, C. lucida, C. porteri, C. protocharoides, C. setosa, C. submollusca, C. wightii, C. zeylanica, Lamprothamnium capitatum, L. compactum, L. stipitatum, Lychnothamnus barbatus) of which 2 are new for the Australian flora (C. erythrogyna and C. wightii), as well as 5 varieties raised to species rank (C. aridicola, C. arnhemensis, C. bancroftii, C. behriana, C. duriuscula), and 2 newly described species (C. lamprothamniformis, C. schultae). Three previously reported species in the tribe (C. braunii, C. corallina, C. fibrosa) are not recorded from the Northern Territory in this study, as previous records were based on erroneous identifications or localities. Although Northern Territory specimens of Lychnothamnus barbatus have not been seen, it has been included in this treatment, because it occurs in south-eastern Queensland, the Gulf of Carpentaria, Papua New Guinea and Timor-Leste. A key, illustrations and descriptions of all the species are provided.
Description:
This study of Northern Territory charophytes documents 22 species in 3 of the genera in tribe Chareae, family Characeae, including 15 previously described species (Chara benthamii, C. erythrogyna, C. globularis, C. karolii, C. lucida, C. porteri, C. protocharoides, C. setosa, C. submollusca, C. wightii, C. zeylanica, Lamprothamnium capitatum, L. compactum, L. stipitatum, Lychnothamnus barbatus) of which 2 are new for the Australian flora (C. erythrogyna and C. wightii), as well as 5 varieties raised to species rank (C. aridicola, C. arnhemensis, C. bancroftii, C. behriana, C. duriuscula), and 2 newly described species (C. lamprothamniformis, C. schultae). Three previously reported species in the tribe (C. braunii, C. corallina, C. fibrosa) are not recorded from the Northern Territory in this study, as previous records were based on erroneous identifications or localities. Although Northern Territory specimens of Lychnothamnus barbatus have not been seen, it has been included in this treatment, because it occurs in south-eastern Queensland, the Gulf of Carpentaria, Papua New Guinea and Timor-Leste. A key, illustrations and descriptions of all the species are provided.
Description:
To clarify species diversity of Tolypella (Characeae, Charophyceae) and the relationship between Tolypella and other genera in Characeae, sequence data from the nuclear ribosomal operon were assembled for 18 individuals of Tolypella. These represented nine named species and two potentially new species from Australia, as well as 13 other taxa of Characeae. Phylogenetic analyses were performed on ribosomal gene sequences (18S, 5.8S and 28S) for Characeae and on ribosomal gene and internal transcribed spacer (ITS) sequences (ribosomal genes þ ITS1 þ ITS2) for Tolypella. Analyses were also performed on the ribosomal gene and ITS sequences combined with plastid gene sequences (atpB, psbC and rbcL). Ribosomal gene sequences alone were conservative and their phylogenetic analyses resulted in topologies similar to a previously published plastid gene-based study but with less support and resolution. In contrast, ITS sequences showed greater variability and their addition resulted in greater resolution among some species relationships of Tolypella. The addition of plastid sequences also resulted in greater support and increased resolution in some lineages but not all.