152,895 species and infraspecific names are in the database, 20,947 images, 59,136 bibliographic items, 408,271 distributional records.

Austrolithon A.S.Harvey & Woelkerling, 1995

Classification:
Empire Eukaryota
Kingdom Plantae
Subkingdom Biliphyta
Phylum Rhodophyta
Subphylum Eurhodophytina
Class Florideophyceae
Subclass Corallinophycidae
Order Hapalidiales
Family Hapalidiaceae
Subfamily Austrolithoideae

Holotype species: Austrolithon intumescens A.S.Harvey & Woelkerling

Original publication and holotype designation: Harvey, A.S. & Woelkerling, W.J. (1995). An account of Austrolithon intumescens gen. et. sp. nov. and Boreolithon van-heurckii (Heydrich) gen. et. comb. nov. (Austrolithoideae subfam. nov., Corallinaceae, Rhodophyta). Phycologia 34: 362-382.

Precise date of publication25 September 1995

Taxonomic status: currently recognized as a distinct genus.

Most recent taxonomic treatment adopted: Schneider, C.W. & Wynne, M.J. (2007). A synoptic review of the classification of red algal genera a half a century after Kylin's "Die Gattungen der Rhodophyceen". Botanica Marina 50: 197-249.

Description: Plants calcified (but see comments), lacking genicula, composed largely of unconsolidated filaments but becoming pseudoparenchymatous in areas of conceptacle production; entirely endophytic except for portions of conceptacle roofs, growing within deformed gall-like growths of Jania rosea (the only known host ‘substrate’); haustoria unknown.

Thallus without apparent dorsiventral, radial or isobilateral organization; thallus construction diffuse to monomerous, consisting of discrete, branched filaments that become partially consolidated in areas of conceptacle production but collectively lack any regularised internal structure. Endophytic filaments apparently lacking epithallial cells but most conceptacle roof filaments each terminating in an epithallial cell; outermost walls of epithallial cells rounded or flattened but not flared at the corners; cell-elongation characteristics uncertain; cells of adjacent filaments apparently not linked by cell fusions or by secondary pit-connections.

Gametangia and carposporangia developing in uniporate conceptacles that are largely but not entirely buried within deformed gall-like growths of the host. Spermatangia (male gametangia) and carpogonia (female gametangia) produced in separate conceptacles; male and female conceptacles apparently formed on different plants. Spermatangia formed on branched or more often on unbranched filaments that arise from the conceptacle chamber floor and roof; spermatangial initials at first each overlain by one or several protective cells that soon degenerate; spermatangial conceptacle roof formation occurring centripetally from groups of vegetative filaments peripheral to developing spermatangial filaments on the conceptacle chamber floor. Carpogoina terminating 2 celled unbranched filaments that arise from the conceptacle chamber floor. Carposporophytes developing in carpogonial conceptacles after presumed fertilization; mature carposporophytes composed of a central fusion cell and several-celled filaments bearing terminal carposporangia.

Tetrasporangia formed in conceptacles on separate plants from gametangia and carposporangia, conceptacles largely but not entirely buried within deformed gall-like growths of the host. Roofs of tetrasporangial conceptacles multiporate and composed of cells. Tetrasporangia each containing four zonately arranged spores and producing an apical plug that blocks a roof pore before spore release. Bisporangia unknown.

Information contributed by: Wm. J. Woelkerling. The most recent alteration to this page was made on 5 Oct 2010 by M.D. Guiry.

Characters considered diagnostic of Austrolithon: Characters collectively considered diagnostic of the genus: Austrolithon is the only known genus of Hapalidiaceae, Subfamily Austrolithoideae with: 1) a largely endophytic thallus composed mainly of unconsolidated filaments except in areas of conceptacle production; 2) diffuse to monomerous thallus construction without any regularised internal vegetative structure; 3) haustoria unknown; and 4) conceptacles largely buried within the host thallus, with only portions of the roof visible at the host thallus surface.

Characters considered diagnostic of higher taxonomic ranks known/presumed to occur in all species of Austrolithon: 1) calcification in the form of calcite; 2) pit plugs with two cap layers at cytoplasmic faces, the outer cap dome shaped; membrane absent; 3) cell walls impregnated with calcite; 4) gametangia and carposporangia produced within uniporate conceptacles; 5) tetrasporangia/bisporangia possessing zonately arranged spores and produced within conceptacles; 6) tetrasporangial/bisporangial conceptacles possessing multiporate plates or roofs; 7) tetrasporangia/bisporangia producing apical plugs; 8) tetrasporangial/bisporangial conceptacles with multiporate roofs composed of cells; lacking an acellular multiporate plate recessed below a single outer opening; and 9) cells of contiguous vegetative filaments not linked by cell fusions or by secondary pit-connections. Characters 1-2 are considered diagnostic of the Corallinophycidae, 3-5 of the Corallinales, 6-7 of the Hapalidiaceae, and 8-9 of the Austrolithoideae.

Generic synonyms: No synonyms of Austrolithon are known.

Comments: Knowledge of Austrolithon and the single known species, A. intumescens, is based on the original detailed account of the type and other collections by Harvey & Woelkerling (1995) and the subsequent floristic account of Woelkerling & Harvey (1996). According to those authors, the extent to which vegetative thallus filaments are calcified is uncertain, but conceptacle roofs definitely are calcified. In terms of growth-form (Woelkerling et al. 1993), plants of Austrolithon are classed as unconsolidated.

The only known host ‘substrate’ is Jania rosea (Corallinaceae, subfamily Corallinoideae) (formerly Haliptilon roseum; see separate AlgaeBase entry). The development of gall-like deformities of infected branch tips of the host are thought (Harvey & Woelkerling 1995: 366) to be reactions triggered by the invasion of developing Austrolithon plants. Except for portions of conceptacle roofs, plants of Austrolithon develop entirely within the host. The extent to which Austrolithon intumescens may be dependent upon the host as an energy source is unknown. No haustoria or other cellular connections between host and endophyte have been found.

Biogeographically, Austrolithon presently is known only from the southern coast of Australia (South Australia, Victoria and Tasmania).

The lists below of diagnostic characters of Austrolithon, and of the higher taxa to which it belongs, are derived from data in Harvey & Woelkerling (1995), Harvey, Broadwater, Woelkerling & Mitrovski (2003), Harvey, Woelkerling & Millar (2003), Le Gall & Saunders (2007), Woelkerling et al. (2008: 282) and/or Le Gall et al. (2009). Diagnostic characters are those that taken together distinguish a taxon from others of the same taxonomic rank (e.g. characters distinguishing Austrolithon from other genera of the Hapalidiaceae, subfamily Austrolithoideae).

Numbers of names and species: There is only one species or infraspecific name in the database at present, which has been flagged as accepted taxonomically on the basis of the listed literature under the species name. In some instances, opinions on taxonomic validity differ from author to author and users are encouraged to form their own opinion. AlgaeBase is a work in progress and should not be regarded as a definitive source only as a guide to the literature..

Names: ('C' indicates a name that is accepted taxonomically; 'S' a homotypic or heterotypic synonym; 'U' indicates a name of uncertain taxonomic status, but which has been subjected to some verification nomenclaturally; 'P' indicates a preliminary AlgaeBase entry that has not been subjected to any kind of verification. For more information on a species click on it to activate a link to the Species database):

Click here to also show infraspecific names in the list below.

References
Harvey, A.S., Broadwater, S.T., Woelkerling, W.J. & Mitrovski, P.J. (2003). Choreonema (Corallinales, Rhodophyta): 18S rDNA phylogeny and resurrection of the Hapalidiaceae for the subfamilies Choreonematoideae, Austrolithoideae and Melobesioideae. Journal of Phycology 39: 988-998.

Harvey, A.S. & Woelkerling, W.J. (1995). An account of Austrolithon intumescens gen. et. sp. nov. and Boreolithon van-heurckii (Heydrich) gen. et. comb. nov. (Austrolithoideae subfam. nov., Corallinaceae, Rhodophyta). Phycologia 34: 362-382.

Harvey, A.S., Woelkerling, W. J. & Millar, A.J.K. (2003). An account of the Hapalidiaceae (Corallinales, Rhodophyta) in south-eastern Australia. Australian Systematic Botany 16: 647-698.

Harvey, A.S., Woelkerling, W.J. & Millar, A.J.K. (2009). The genus Amphiroa (Lithophylloideae, Corallinaceae, Rhodophyta) from the temperate coasts of the Australian continent, including the newly described A. klochkovana. Phycologia 48: 258-290.

Le Gall, L. & Saunders, G.W. (2007). A nuclear phylogeny of the Florideophyceae (Rhodophyta) inferred from combined EF2, small subunit and large subunit ribosomal DNA: establishing the new red algal subclass Corallinophycidae. Molecular Phylogenetics and Evolution 43: 1118-1130.

McNeill, J., Barrie, F.R., Burdet, H.M., Demouline, V., Hawksworth, D.L., Marhold, K., Nicolson, D.H., Prado, J., Silva, P.C., Skog, J.E., Wiersema, J.H. & Turland, N.J. (2006). International Code of Botanical Nomenclature (Vienna Code) adopted by the Seventeenth International Botancial Congress Vienna, Austria, July 2005. pp. [i-iv], v-xviii + 1-568. Liechtenstein: A.R.G. Gantner Verlag.

Le Gall, L., Payri, C.E., Bittner, C.E., & Saunders, G.W. (2010). Multigene polygenetic analyses support recognition of the Sporolithales, ord. nov. Molecular Phylogenetics and Evolution 54(1): 302-305.

Le Gall, L. & Saunders, G.W. (2007). A nuclear phylogeny of the Florideophyceae (Rhodophyta) inferred from combined EF2, small subunit and large subunit ribosomal DNA: establishing the new red algal subclass Corallinophycidae. Molecular Phylogenetics and Evolution 43: 1118-1130.

Woelkerling, W.J. & Harvey, A.S. (1996). Subfamily Austrolithoideae. In: The marine benthic flora of Southern Australia – Part IIIB. Gracilariales, Rhodymeniales, Corallinales and Bonnemaisoniales . (Womersley, H.B.S. Eds), pp. 160-163. Canberra: Australian Biological Resources Study.

Woelkerling, W.J., Millar, A.J.K., Harvey, A. & Baba, M. (2008). Recognition of Pachyarthron and Bossiella as distinct genera in the Corallinaceae, subfamily Corallinoideae (Corallinales, Rhodophyta). Phycologia 47: 265-293.

Verification of data
Users are responsible for verifying the accuracy of information before use, as noted on the website Content page.

Contributors
Some of the descriptions included in AlgaeBase were originally from the unpublished Encyclopedia of Algal Genera, organised in the 1990s by Dr Bruce Parker on behalf of the Phycological Society of America (PSA) and intended to be published in CD format. These AlgaeBase descriptions are now being continually updated, and each current contributor is identified above. The PSA and AlgaeBase warmly acknowledge the generosity of all past and present contributors and particularly the work of Dr Parker.

Descriptions of chrysophyte genera were subsequently published in J. Kristiansen & H.R. Preisig (eds.). 2001. Encyclopedia of Chrysophyte Genera. Bibliotheca Phycologica 110: 1-260.

Created: 28 December 2000 by M.D. Guiry

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Please cite this record as:
Guiry, M.D. & Guiry, G.M. 2018. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. http://www.algaebase.org; searched on 22 September 2018.

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