Byron Flora and Fauna Study 1999 - Byron Shire Council

A GREENPRINT FOR A SUSTAINABLE FUTURE
Isoglossa (Isoglossa eranthemoides FAMILY ACANTHACEAE)
Introduction. Isoglossa is a small ground herb found in the rainforest understorey. It is known from a small number of
sites, four of which are in the Byron Shire. As it is similar to the common Pastel Flower (Pseuderanthemum variable), from
which it can be easily distinguished only during the brief flowering period, it is probable that Isoglossa has been overlooked
in the past. Surveys are currently underway through the NSW NPWS, and a draft Recovery Plan will be prepared
in the near future. Isoglossa is a host plant for the Australian Leafwing Butterfly Doleschallia bisaltidae australis.
Conservation status. Isoglossa is listed on Schedule 1 (Endangered) of the TSC Act, 1995 and has a ROTAP code of 2E
(Briggs and Leigh 1996).
Habit. A herb to 20 cm high (Harden 1992), although Bower et al. (1999) recorded specimens up to 50 cm high..
Flowers. White, lacking the staminodes which are found in the flowers of Pastel Flower. Flowering from the end of
September to early to mid November (Bower et al. 1999). No information about pollination is available.
Fruit. A capsule 9-12 mm long with concentrically ridged seeds (Harden 1992). No information about dispersal is
available. Seed capsules observed at Booyong suggest the dispersal method is ‘explosive’ (N. Nicholson pers. comm.).
Other members of Acanthaceae, e.g. Graptophyllum also have explosive seed capsules.
Habitat. Subtropical rainforest (Harden 1992).
Distribution. Collected only from the Tweed River and Booyong, near Lismore, NSW (Harden 1992), Mt Warning (H.
James pers. comm.) and Mortons Scrub, Johnstons Scrub, Herrmanns Scrub, Emerys Scrub and Dawes Bush (Bower et
al. 1999) and recently from Nobles Scrub (H. Bower pers. comm.).
Regeneration and horticulture. Isoglossa can be assumed to grow in the same way as the related Pastel Flower (Nicholson
and Nicholson 1991), from cuttings of roots or stems, or transplant of self-seeded seedlings.
Economic and cultural significance. Isoglossa is an ornamental herb. The related Pastel Flower makes an attractive pot
specimen indoors while flowering (Nicholson and Nicholson 1991), and Isoglossa would presumably also suit this purpose.
Otherwise, no particular use or significance is known apart from the aesthetic and ecological values of all native
rainforest species.
Abundance and reservation. Isoglossa is known from very few locations and is poorly reserved, making the plants occurring
in the study area of particular conservation significance.
Threats and amelioration. Isoglossa occurs in weed-infested Big Scrub remnants (Bower et al. 1999) and is particularly
threatened by ground-covering weed species such as Wandering Dew Tradescantia fluminensis and Asparagus Fern Protasparagus
plumosus. In addition, grazing, land clearing and habitat modification can be assumed to threaten Isoglossa. Since such a
small number of sites are known, Isoglossa is vulnerable to the effects of chance events.
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