Myriophyllum implicatum - critically endangered species listing

The Scientific Committee, established by the Threatened Species Conservation Act, has made a Final Determination to list the herb, Myriophyllum implicatum Orchard as a CRITICALLY ENDANGERED SPECIES in Part 1 of Schedule 1A of the Act, and as a consequence, to omit reference to Myriophyllum implicatum Orch. from Part 4 of Schedule 1 (Species presumed extinct) of the Act. Listing of Critically Endangered species is provided for by Part 2 of the Act.

NSW Scientific Committee - final determination

The Scientific Committee has found that:

1. Myriophyllum implicatum Orchard (family Haloragaceae) is an inconspicuous creeping matted herb 2-10 cm high, with erect unbranched flowering stems arising from a tangled mat of prostrate stolon-like stems. All stems slender, 0.4 mm in diameter, the prostrate stems rooting freely at the nodes.  Leaves monomorphic, all alternate (rarely, a few subopposite), linear, 2.5-5.0 mm long, 0.6-0.7 mm wide, tapering slightly to each end, margins entire, tip blunt with a small red terminal gland, midrib obscure; a very small (0.1 mm) hydathode sometimes present on each side of the base of the leaf. Plants dioecious. Inflorescence a simple spike with the flowers borne singly in the axils of the leaves. Bracteoles sexually dimorphic; bracteoles of male flowers linear to lanceolate 0.8-0.9 mm long, 0.2-0.4 mm wide, margins entire, tip acute; bracteoles of female flowers ovate to lanceolate, 0.4-0.5 mm long, 0.2-0.3 mm wide, margins entire, tip acute.  Male flowers 4-merous, on pedicels 0.6-0.7 mm long; sepals absent; petals 4, 1.8-2.5 mm long, 1.2-1.4 mm wide, hooded, not keeled or claw-like, tip rounded; stamens 8, filaments 0.3 mm long; anthers linear-oblong, 1.3-1.4 mm long, 0.3 mm wide, non-apiculate; styles and ovary absent.  Female flowers 4-merous, sessile; sepals, petals and stamens all absent; styles 4, sessile; stigmas white, fimbriate; ovary more or less cubic 0.8 mm long, 0.7 mm wide, rounded on angles, weakly verrucose.  Fruit sessile, reddish-purple, cubic, 0.8-0.9 mm long, 0.8 mm diameter; mericarps separating freely at maturity, cylindrical, 0.8-0.9 mm long, 0.4 mm diameter, rounded at base, slightly obliquely truncate at apex, strongly papillose on dorsal surface, the papillae arranged in 3-5 vertical rows, but somewhat irregular. (Description adapted from Orchard 1985, which includes the best available illustration [Fig. 27]; a diagnostic illustration of the fruit is available at http://plantnet.rbgsyd.nsw.gov.au/search/florasearch.htm). Many species of Myriophyllum exhibit quite different leaf forms and sizes depending on whether growing submerged or emergent.  M. implicatum maintains only one leaf form and usually grows emergent from very shallow water or in exposed mud.  M. implicatum is also one of the few Australian species thought to be strictly dioecious (male and female flowers borne on separate plants). Reliable identification depends on having flowering and mature fruiting material.

2. Myriophyllum implicatum is related to  M. filiforme Bentham, which occurs across tropical Australia, and the species share distinctively papillose fruits.  M. filfiforme differs however in its monoecy, usually smaller fruits (0.7-0.8 mm long, 0.4-0.5(-2.0) mm wide), sessile male flowers, and multiple flowers per leaf axil.  M. implicatum is also closely related to the mixed monoecious/dioecious  M. striatum Orchard (NSW, Queensland, Victoria) and the strictly monoecious  M. costatum Orchard (WA), both of which have longitudinally ridged fruits.

3. Myriophyllum implicatum is recorded from New South Wales and Queensland. The only previous occurrence in New South Wales is an undated (but old) collection from the Hastings River. In Queensland the species is known from the Moreton Bay area and sporadic records up the east coast to at least Townsville, and inland to the Desert Uplands; it is listed in that State as Rare flora on Schedule 4 of the  Nature Conservation (Wildlife) Regulation 2006.

4. Myriophyllum implicatum has been listed on Part 4 of Schedule 1 since the commencement of the  Threatened Species Conservation Act 1995 as a species presumed to be extinct in New South Wales. A collection in August 2008 (NSW 785016, J. Benson 2589 & S. Waller) from Pilliga National Park has been authoritatively identified as  M. implicatum (P.G. Wilson and P. Kodela pers. comm. June 2009).  Myriophyllum implicatum has a very highly restricted geographic distribution in NSW. Both the area of occupancy and extent of occurrence are estimated to be 4km² based on occupancy of a single 2 x 2 km grid cell, the scale recommended for assessing area of occupancy by IUCN (2008).

5. Myriophyllum implicatum is found in moist situations, in or adjacent to fresh water. The 2008 rediscovery in New South Wales was in a large open partly inundated gilgai depression on cracking clays, in an area otherwise dominated by an open forest/woodland of  Allocasuarina luehmannii (Buloke), and  Eucalyptus blakelyi (Blakely’s Red Gum). The depression was drying out and supported an ephemeral paludal and shallow-aquatic association, characterisable as ‘dense to mid-dense low to mid-high sedgeland - grassland – rushland’ (S. Waller and J. Benson, pers. comm. June 2009). Taller species included the rushes  Juncus aridicola and  J. continuus, the sedges  Cyperus gunnii and  Schoenoplectus erectus (an introduced weed), and the grasses  Pseudorophis spinescens (Spiny Mudgrass) and  Panicum decompositum (Native Millet). Plants of lower growth included the sedges  Eleocharis pusilla,  Cyperus gymnocaulos and  Isoletis hookeriana, and the mat-grass  Cynodon dactylon (Couch). Forb species include  Bulbine semibarbata (Leek Lily),  Myriocephalus pluriflorus (Woolly-heads),  Triglochin calcitrapa (Spurred Arrowgrass),  Myriophyllum striatum,  Crassula sieberiana (Australian Stonecrop),  Brachyscome nodosa,  Brachyscome ciliaris var.  subintegrifolia,  Centipeda minima (Spreading Sneezeweed),  Isotoma fluviatilis (Swamp Isotome),  Stellaria sp.,  Anagallis arvensis (Pimpernel); and the Nardoo ferns  Marsilea hirsuta and  Marsilea drummondii. The association is thought to be a distinctive ecological community (J. Benson pers. comm. June 2009). However,  M. implicatum in New South Wales may not be confined to this association, as in Queensland it occurs in a wide range of moist microhabitats (Orchard 1985; Thompson and Sharp 2003a, b) ranging from freshwater seepage areas of coastal dunes to muddy areas near streams or swamps (and rarely in shallow flowing water); inland occurrences in that State are commonly in ephemeral billabongs and floodplain depressions prone to periodic inundation.

6. Myriophyllum implicatum is also noted as a constituent species (in Queensland) of the Endangered Ecological Community listed under the Commonwealth  Environment Protection and Biodiversity Conservation Act 1999 under the title ‘The community of native species dependent on natural discharge of groundwater from the Great Artesian Basin’. A similar listing, of the ‘Artesian Springs Ecological Community’ exists under the  Threatened Species Conservation Act 1995, although  M.  implicatum is not yet known to occur in that community in this State.

7. Myriophyllum implicatum probably germinates opportunistically (with inundation). Flowering is reported from August into summer, and fruiting until February (Orchard 1985); the actual period of flowering at any one site may however be quite short. Pollination mode is uncertain, although Kubitzki (2007) states that most genera of the family are wind-pollinated. Reproduction is by seed held in mericarps, but in common with many species of  Myriophyllum, node-rooting pieces of stem may also form new plants. Kubitzki (2007) also notes ‘the aptitude of the mericarps of Myriophyllum ... for dispersal by fish or waterfowl’, as well as the obvious likelihood of dispersal by water movement.

8. The site in Pilliga National Park where Myriophyllum implicatum was recently found has been heavily disturbed by Feral Pigs and shows some disturbance by four-wheel drive vehicles (S. Waller pers. comm. June 2009). ‘Predation, habitat degradation, competition and disease transmission by Feral Pigs,  Sus scrofa Linnaeus 1758’ is listed as a Key Threatening Process under the  Threatened Species Conservation Act 1995.  M. implicatum is likely, over much of its inland range, to be dependent on periodic inundation of habitat at a frequency that maintains the ecological integrity of the microhabitat (e.g. the paludal zone of ephemeral billabongs) and allows renewal of the soil-stored seed bank. Changes to inundation, rainfall frequencies, or artesian spring flows that run counter to this are likely to lead to decline of the species and its habitat. ‘Alteration to the natural flow regimes of rivers and streams and their floodplains and wetlands’, and ‘Anthropogenic Climate Change’ are listed as Key Threatening Processes under the  Threatened Species Conservation Act 1995. Some of the above threats are also addressed in Commonwealth Key Threatening Process listings, under the  Environment Protection and Biodiversity Conservation Act 1999.

9. Some potential habitat in New South Wales may be subject to degradation by the establishment of exotic grass species; ‘Invasion of native plant communities by exotic perennial grasses’ is listed as a Key Threatening Process under the Threatened Species Conservation Act 1995. Other potential threats, not known to be operating at the Pilliga site at this stage, include invasion of habitat by the exotic weed Lippia ( Phyla canescens), and salination of water and soil.

10. Myriophyllum implicatum Orchard is eligible to be listed as a Critically Endangered species as, in the opinion of the Scientific Committee, it is facing an extremely high risk of extinction in New South Wales in the immediate future as determined in accordance with the following criteria as prescribed by the  Threatened Species  Conservation Regulation 2002:

Clause 15

The geographic distribution of the species is estimated or inferred to be:

and either:

Clause 16

The estimated total number of mature individuals of the species is:

and either:

Dr Richard Major
Chairperson
Scientific Committee

Proposed Gazettal date: 16/07/10
Exhibition period: 16/07/10 - 10/09/10

A notice of determination to provisionally list this species as a critically endangered species was gazetted on 21/08/09

References:

IUCN (2008) ‘Guidelines for using the IUCN Red List Categories and Criteria. Version 7.0.’ (Standards and Petitions Working Group of the IUCN Species Survival Commission Biodiversity Assessments Sub-committee: Switzerland).

Kubitzki, K (2007) Haloragaceae. In ‘The families and genera of flowering plants. Vol. IX Flowering Plants – Eudicots Berberidopsidales [to] Sabiaceae’. (Ed. K. Kubitzki) pp. 184-190. (Springer: Berlin)

Orchard AE (1985) Myriophyllum (Haloragaceae) in Australasia. II. The Australian Species,  Brunonia 8,173-291

Thompson EJ, Sharp D (2003a) Regional ecosystems of the Desert Uplands: 10.3.14 River red gum and/or coolabah open-woodland along channels and on floodplains. Queensland Environmental Protection Agency. (accessed 23 June 2009)

Thompson EJ, Sharp D (2003b) Regional ecosystems of the Desert Uplands: 10.3.15 Grasslands, sedgelands, ephemeral herblands and open-woodlands in depressions on sand plains. Queensland Environmental Protection Agency. (accessed 23 June 2009)