Michelle T. Casanova

An overview of Chara L. in Australia (Characeae, Charophyta)

Charophytes (family Characeae) are a cohesive group within the green algae. The genus Chara is abundant and diverse in a variety of Australian habitats. Approximately 37 taxa of Chara have been described on the basis of Australian collections. The current status of charophyte taxonomy is confused. RD Wood revised Australian charophytes in 1972 on the basis of an erroneous species concept, and charophytes are rarely identified lower than genus by ecologists and water managers. Many species were described by overseas experts in the mid-1800s, and this trend continues to the present day. Typically, species descriptions have been based on examination of few specimens, and sometimes not even fertile representatives of each species. In this study Wood’s (1972) taxonomic treatment of Australian members of the genus Chara is examined and analysed in relation to historical species concepts and more recent experimental taxonomy and oospore morphology. Thorough studies based on determination of reliable indicators of genetic incompatibility through culture studies, including oospore morphology and genetic analysis and objective analysis of fertile specimens, are now required.

An overview of Nitella (Characeae, Charophyceae) in Australia

The genus Nitella Ag. in algal family Characeae is characterised by furcate (forked) branchlets, compressed oospores (i.e. oval in cross-section), terminal antheridia and a 10-celled coronula on the oogonium. Species of Nitella are submerged plants that grow in a variety of wetland and riverine habitats. Approximately 89 taxa of Nitella (species, subspecies, varieties and forms) have been described on the basis of Australian collections, and published estimates of the number of species range from 18 to >35. The lower value is based on the assumption that infra-specific variation is great, species have a wide distribution, monoecy and dioecy are not indicative of speciation and the number of furcations and the ratio of branchlet segment lengths vary for a species owing to the environment in which they grow. The higher value is based on evidence that morphological characters are relatively constant for a species, that oospore variation is a good indication of speciation and that monoecious and dioecious entities are not inter-fertile. An overview of Australian members of the genus is presented here as a framework for further taxonomic work. Representatives of all three subgenera of Nitella occur in Australia, with subgenus Nitella poorly represented, and subgenera Tieffallenia and Hyella equally speciose. The subgenera are defined here in relation to the Australian taxa they contain. In the present treatment, section Migularia is transferred from subgenus Tieffallenia to subgenus Hyella, and several species are transferred to subgenus Tieffallenia. Within subgenus Tieffallenia, variation in vegetative and oospore morphology is useful for distinguishing among sections and species. However, although members of subgenus Hyella display a similar range of variation in vegetative morphology, most of the species have similar, reticulate, oospore ornamentation. Australia is home to a large number of endemic species of Nitella, many of which are dioecious. The total number of species and the degree of endemism have been underestimated in earlier studies, and it is likely that more than 50 species of Nitella will be recognised on the basis of Australian specimens. A key to the subgenera, and keys to sections in the subgenera are provided.

A revision of Chara sect. Protochara, comb. et stat. nov. (Characeae: Charophyceae)

Abstract. A revision of a group of ecorticate species of Chara is presented, on the basis of fresh, pressed and spirit-preserved material. The following seven species are recognised, characterised by a very simple morphology, with few or inconspicuous accessory cells (cortication, stipulodes, bract cells, bracteoles) and large gametangia: Chara australis R.Br., C. lucida (A.Braun) Casanova & Karol comb et. stat. nov., C. porteri Casanova, sp. nov., C. protocharoides Casanova & Karol, nom. nov. (=Protochara australis Womersley & Ophel) and C. stuartiana (Kütz.) Casanova & Karol comb. et. stat. nov. from Australia, and C. corallina Klein ex Willd. and C. wallichii A.Braun from Asia. A new section, Chara subg. Charopsis sect. Protochara (Womersley & Ophel) Casanova & Karol, comb. et stat. nov., is erected to accommodate these taxa, formerly placed in sect. Charopsis.

Lamprothamnium in Australia (Characeae, Charophyceae)

Abstract. Charophytes in the genus Lamprothamnium exhibit a large amount of diversity, particularly in the examples from Australia, although little of that variation has been recognised at species level in the past. The Australian members of the genus are revised here on the basis of extensive new collections, examination of specimens in herbaria and comprehensive review of the literature and available type material. The existing species Lamprothamnium macropogon (A.Braun) Ophel, L. inflatum (Fil. & G.O.Allen ex Fil.) A.García & Karol and L. heraldii A.García & Casanova are retained, eight new species are described (L. australicum Casanova, L. beilbyae Casanova, L. capitatum Casanova, L. compactum Casanova, L. coorongense Casanova, L. diminutum Casanova, L. macroanthum Casanova and L. stipitatum Casanova) and two taxa variously treated at infraspecific rank in Lychnothamnus are transferred to Lamprothamnium at species rank (L. cockajemmyense Casanova, L. tasmanicum (A.Braun) Casanova). Neither L. papulosum (Wallr.) J.Groves nor L. succinctum (A.Braun) R.D.Wood are confirmed for Australia after examination of the type material of these species. Species are distinguished by the arrangement of the gametangia, morphology of the fertile whorls and characteristics of the oospores. Four of these species are dioecious and nine are monoecious, which supports published conjectures concerning the biogeography of charophyte species (Proctor (1980): J. Phycol. 16, 218–233, doi:10.1111/j.1529-8817.1980.tb03023.x).

Review of the species concepts Chara fibrosa and C. flaccida (Characeae, Charophyceae)

Abstract. Taxonomic circumscriptions of the charophyte taxa Chara fibrosa C.Agardh ex Bruzelius. and C. flaccida var. wightii A.Braun are revised, and both taxa are recognised at species rank, as C. fibrosa and C. wightii (A.Braun) Casanova. Both species are illustrated and a review of relevant morphological characters is also presented.

Monoecious Nitella species (Characeae, Charophyta) from south-eastern mainland Australia, including Nitella paludigena sp. nov.

Identification of Australian species of Nitella is problematic. Several species of monoecious Nitella have been described from south-eastern mainland Australia, but identification of these based on current treatments has been difficult. In response to the discovery of a new monoecious Nitella from the swamps of the Fleurieu Peninsula in South Australia, the monoecious species of Nitella from south-eastern mainland Australia were examined and compared. N. paludigena M.T.Casanova & K.G.Karol is distinguished from other monoecious species on the basis of its overall vegetative morphology and oospore morphology. N. paludigena is found in peaty tea-tree (Leptospermum sp) swamps on the Fleurieu Peninsula in South Australia, and in the south-west of Victoria. A description of the morphology and ecology of the five monoecious Nitella species from south-eastern mainland Australia is given, along with a key.

Typification and circumscription of Nitella sonderi (Characeae, Charophyceae)

Nitella sonderi A.Braun in family Characeae was described in 1852, on the basis of a single specimen collected by Ferdinand von Mueller from Melbourne. This specimen was lost and not referred to again, nor illustrated. From 1857 until 1935, three other specimens of N. sonderi were examined or referred to in published literature. The species was amalgamated with the Asian species N. pseudoflabellata in 1962 and a neotype (Lewis 6) was assigned in 1972. In the year 2000, a specimen with the same collection locality and collector as the type of N. sonderi, labelled N. sonderi ,w as found in the National Herbarium of Victoria (Mueller, September 1852). In the present paper, I deal with the following two issues: typification of N. sonderi (i.e. is the Lewis or the Mueller specimen the most appropriate type?) and whether N. sonderi and N. pseudoflabellata are the same species. The Lewis and the Mueller specimens were compared with the protologue, and the neotype is retained. Oospores and vegetative features of N. sonderi were compared with type material of N. pseudoflabellata var. imperialis (sensu R.D.Wood) and N. sonderi is reinstated as a separate species on the basis of its vegetative morphology, dioecy and oospore morphology, and a description is given with reference to specimens from its entire range. N. sonderi is a spring and summer-growing annual of sheltered sites in temporary wetlands throughout Victoria, New South Wales, and upland south-eastern Queensland. It persists during dry times via a bank of dormant, long-lived oospores in the seed bank. Linking a good taxonomy with thorough ecological studies in this way can inform management of water resources.

What makes a swamp swampy? Water regime and the botany of endangered wetlands in western Victoria

Freshwater temporary wetlands are a little-studied ecosystem worldwide. They have been recognised as critically endangered in south-eastern Australia under Australian biodiversity conservation legislation. However, little has been recorded about their hydrology, functioning or biodiversity values; i.e. the factors that make them intrinsically ‘swampy’. In this paper, we developed a simple threshold model of wetland hydrology based on historical rainfall records and calculated evaporation records matched to records and recollections of the owners of swamps, and documented water-plant and microalgal species richness. The model indicated that swamps were inundated to at least 10-cm depth in an average of 6.3 years per decade for most of the 20th century. The average dry time between inundations was 1.27 years (maximum of 4.5 years). Since 1998, the frequency of inundation appears to have decreased, and the average dry times have increased. Despite, or because of, their temporary nature, these swamps have high biodiversity values among the vegetation and the microalgae, more than has been recorded for near-by permanent wetlands. There is no evidence that a drier and warmer climate will have a negative impact on biodiversity values; however, land management is likely to be important for maintaining these systems as the climate changes.

A revision of Chara sect. Charopsis (Characeae: Charophyceae) in Australia, including specimens collected for Bush Blitz

Abstract. Australian species of Chara L. sect. Charopsis (Kütz.) Leonh. are revised. Multivariate analysis supports recognition of four species: Chara braunii C.C.Gmel., C. evanida Casanova, C. karolii Casanova and C. muelleri (A.Braun) F.Muell. These taxa are described and illustrated, and a key is provided.

Historical water-plant occurrence and environmental change in two contrasting catchments

Historical conditions in riparian systems can be derived from the recorded distribution of water plants and their ecological requirements. Herbarium and literature records were used to assess historical species occurrence, and a field survey and a seed-bank study were used to assess present-day occurrence in two adjacent, southern Australian catchments: the Angas River and the Tookayerta Creek. There was an increase in the proportion of salinity- and drought-tolerant species detected in the Angas River catchment since European settlement. Field-survey data and the seed-bank study data were similar for that catchment, indicating that the submerged flora of the Angas River catchment is resilient to drought. In contrast, the dissimilarity of the seed-bank study data and the survey data from the Tookayerta Creek catchment indicated that the submerged flora in that catchment is not tolerant of drought. Although submerged species in the Tookayerta Creek catchment are dependent on the presence of permanent fresh water, there were more salinity-tolerant species in the lower Tookayerta catchment in the present study than were detected in the past. Comparison of the historical plant distribution and present-day distribution in catchments can provide interpretation of environmental conditions and ecological filters now, and since European settlement.