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- Title
A new monotypic family for the enigmatic crustose red alga Plagiospora gracilis.
- Authors
Maggs, Christine A.; Saunders, Gary W.
- Abstract
Plagiospora gracilis, a mucilaginous crustose red alga growing on subtidal pebbles on both coasts of the North Atlantic Ocean, forms distinctive tetrasporangia (red algal meiotic structures that release haploid tetraspores), but gametophytes have never been reported. In the absence of gametangia, the taxonomic position of this monotypic genus has always been uncertain; it is currently placed provisionally in Gloiosiphoniaceae (Gigartinales) by comparison with sporophytes of Gloiosiphonia obtained in culture. Dioecious gametophytic crusts of P. gracilis are now reported for the first time, forming gametangia in inconspicuous superficial sori. There is no evidence that fertilization ever occurs in the field although fertile males and females were collected together. In culture, tetraspores grew into tetrasporophytes for three successive generations, by presumed apomictic sporophyte recycling. The life history of P. gracilis may represent a late stage in the loss of sexual reproduction leading to tetraspore-to-tetrasporophyte life histories such as that in Hildenbrandia. Phylogenetic analysis of sequences of rbcL, large subunit (28S) rDNA and coxI (COI-5P) for P. gracilis with other Gigartinales resolved P. gracilis as a distinct lineage in a well-supported clade of the families Sphaerococcaceae, Gloiosiphoniaceae, Endocladiaceae, Nizymeniaceae and Phacelocarpaceae. We here propose the monotypic Plagiosporaceae fam. nov. to accommodate P. gracilis.
- Subjects
NORTH Atlantic Ocean; MONOTYPIC taxon; RED algae; GLOIOSIPHONIACEAE; DIOECIOUS plants; ENDOCLADIACEAE
- Publication
Botanical Journal of the Linnean Society, 2016, Vol 182, Issue 1, p1
- ISSN
0024-4074
- Publication type
Article
- DOI
10.1111/boj.12450