Cucumis althaeoides, a climbing herb - critically endangered species listing

The NSW Threatened Species Scientific Committee, established under the Biodiversity Conservation Act 2016 (the Act), has made a Final Determination to list the climbing herb Cucumis althaeoides (Ser.) P.Sebastian & I.Telford as a CRITICALLY ENDANGERED SPECIES in Part 1 of Schedule 1 of the Act. Listing of Critically Endangered species is provided for by Part 4 of the Act.

NSW Threatened Species Scientific Committee - final determination

The NSW Threatened Species Scientific Committee has found that:

1. Cucumis althaeoides is unlikely to be nationally threatened using the Common Assessment Method (CAM MOU 2015) applied at the national scale (NSW TSSC 2017). Consequently, this species is eligible to be listed as a threatened species on the basis of the risk of extinction in New South Wales (NSW).

2. Cucumis althaeoides (Ser.) P.Sebastian & I.Telford (family Cucurbitaceae) is described as a trailing or climbing perennial vine, monoecious, most vegetative parts hispid, sometimes pilose; stems to 3 m long, to 1.6 mm diameter, ribbed, annually sprouting from a perennating rootstock. Tendrils simple, to 15 cm long. Leaves: subsessile or petiole to 38 mm long; lamina ovate or broadly lanceolate in outline, sometimes hastate, 24–75 mm long, 18–70 mm wide, cordate, unlobed or shallowly 3-lobed, rarely 5-lobed, obtuse or acute, mucronate. Inflorescences unisexual. Male flowers in 3–15-flowered fascicles, sometimes in racemes with peduncles to 3 mm long; pedicels to 7 mm long. Female flowers 1 or 2, rarely 3 or 4 per axil; pedicels to 2 mm long; ovary ellipsoidal, ca. 3 mm long, pilose with antrorse hairs. Fruit globose, 8–18 mm diameter, pale green with darker longitudinal markings, at maturity sparsely pilose, red, with 9– 25 seeds; fruiting pedicel to 6 mm long. Seeds ovate, 3.8–4.5 mm long, 2.3–2.8 mm wide, buff, the faces convex, verrucose, the margin thickened and raised (adapted from PlantNET 2017).

3. Cucumis althaeoides is widespread across northern Australia and in NSW is known from three small populations in Oxley Wild Rivers National Park, approximately 40 km east of Walcha in the New England Tablelands Bioregion. These NSW populations of  C. althaeoides are disjunct with the nearest known population occurring approximately 400 km to the north in southeastern Queensland (Telford  et al. 2011). In Oxley Wild Rivers National Park, populations of  C. althaeoides have been recorded from three sites along the Apsley River and Green Gully Creek (L. Copeland  in litt. May 2016).

4. Cucumis althaeoides is a perennial vine which can be relatively dormant during dry periods and can then grow rapidly from the thickened rootstock during more favourable conditions. It is unclear how long individuals live or how quickly they may reproduce. In NSW,  C. althaeoides is known to occur on rocky soil in gravel beds along freshwater rivers and streams. The species has been documented in open habitats beneath River Oaks ( Casuarina cunninghamiana) in association with  Melaleuca bracteata,  Stephania japonica,  Cleome viscosa,  Digitaria sanguinolentis and  Mitracarpus hirtus (L. Copeland  in litt. May 2016). Across its broader Australian range,  C. althaeoides occurs on coastal sands or riverine alluvium in herbfields and  Casuarina or  Eucalyptus woodland (Telford  et al. 2011).

5. The number of mature individuals of Cucumis althaeoides in NSW is estimated to be very or extremely low with only 16 plants known across the three populations (L. Copeland  in litt. May 2016). Searches of potentially suitable habitat for  C. althaeoides within the vicinity of known populations by several botanists since 2007 have failed to locate additional populations (L. Copeland  in litt. May 2016).

6. The distribution of Cucumis althaeoides in NSW is very highly restricted. The extent of occurrence (EOO) is estimated as 39 km2. The EOO is based on a minimum convex polygon enclosing all sites of occurrence of the species, the method of assessment recommended by IUCN (2016). The area of occupancy (AOO) is estimated as 12 km2 based on 2 x 2 km grid cells, the scale recommended for assessing AOO by IUCN (2016).

7. Threats to Cucumis althaeoides in NSW include grazing by feral animals, including horses, goats and cattle, and competition from various weed species, including  Bidens pilosa (Cobbler’s Peg),  B. subalternans (Greater Beggar’s Tick),  Zinnia peruviana,  Tagetes minuta (Stinking Roger),  Cuscuta campestris (Golden Dodder),  Galinsoga parviflora (Potato Weed) and  Lantana camara (Lantana) (L. Copeland  in litt. May 2017). The population’s limited extent makes it highly susceptible to localised events such as grazing by feral animals and competition from weeds. ‘Competition and habitat degradation by Feral Goats,  Capra hircus Linnaeus 1758’ and ‘Invasion, establishment and spread of Lantana ( Lantana camara L. sens. lat)’ are listed as Key Threatening Processes under the Act.

8. Cucumis althaeoides (Ser.) P.Sebastian & I.Telford is eligible to be listed as a Critically Endangered species as, in the opinion of the NSW Threatened Species 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  Biodiversity Conservation Regulation 2017:

Clause 4.3 - Restricted geographic distribution of species and other conditions (Equivalent to IUCN criterion B)

Clause 4.4 - Low numbers of mature individuals of species and other conditions (Equivalent to IUCN criterion Clause C)

Clause 4.5 - Low total numbers of mature individuals of species (Equivalent to IUCN criterion D)

Dr Marco Duretto
Chairperson
NSW Threatened Species Scientific Committee

Exhibition period: 27/04/18 – 22/06/18
Proposed Listing date: 27/04/18

References:

CAM MOU (2015) Intergovernmental memorandum of understanding - Agreement on a commonassessment method for listing of threatened species and threatened ecological communities.

IUCN Standards and Petitions Subcommittee (2016) Guidelines for Using the IUCN Red ListCategories and Criteria. Version 12. Prepared by the Standards and Petitions Subcommittee.

NSW TSSC (2017) National Assessment of Cucumis althaeoides. Report to the NSW Threatened Species Scientific Committee.

PlantNET (The NSW Plant Information Network System) Royal Botanic Gardens and Domain Trust, Sydney.  (accessed 24 April 2017).

Telford IR, Sebastian P, Bruhl JJ, Renner SS (2011) Cucumis (Cucurbitaceae) in Australia and eastern Malesia, including newly recognized species and the sister species to  C. melo.  Systematic Botany 36, 376–389.