3.10 cycas megacarpa K. Hill
Cycas megacarpa occurs from the Many Peaks and Calliope Ranges south to near Kilkivan. The distribution of C. megacarpa has a range of approximately 240 km and encompasses an area of occurrence of approximately 28000 km2. It is most commonly found on undulating to hilly terrain on gentle to steep slopes and hill crests in eucalypt woodland or open forest at altitudes of 40 to 500 m. The soils are generally well drained, shallow, often stony, sandy loam to clay loam. There is no quantitative data on populations. However, it has been reported as being rare to very common at collection sites. Current or perceived threats to the continued survival of C. megacarpa are considered to be loss of habitat, destruction of plants, illegal removal of seeds, seedlings and mature plants and inappropriate fire regimes.
3.10.2 Species description and identification
The genus Cycas is placed in the family Cycadaceae and occurs from East Africa to Japan and Australia (Mabberley 1997). It is estimated to contain approximately 40 species over its range with 27 species in Australia (Hill 1996).
Cycas megacarpa K. Hill was formally described in 1992 from material collected west of Miriam Vale (Hill 1992). The botanical description of Cycas megacarpa is as follows:
A small to medium sized cycad with an erect trunk to 3 m tall and 8-14 cm diameter, and a dense erect to rounded crown of leaves. Mature leaves are 40-110 cm long, glossy and mid to dark green. Each leaf consists of a stalk with 120 to 170 leaflets. The leaflets are linear, leathery and 12-20 cm long x 0.5-0.75 mm wide. The lowest leaflets are reduced to spine-like structures (approximately 0.5 cm long). The male and female reproductive structures develop on separate individuals. Male plants produce brown, hairy cylindrical cones 18 cm long x 17 cm diameter. The female plants produce loose open cone-like structures at the top of the plant. Two to four seeds are borne on hairy stalks up to 25 cm long, with a broad flat spear-shaped tip. As the seeds mature the stalks lengthen and spread outward from the top of the plant. Seeds are egg-shaped, greenish to light brown and 4-6 cm long x 3.5-4.5 cm diameter. For a more detailed description and illustrations refer to Hill (1992) and Jones (1993).
Prior to its formal description Cycas megacarpa had been previously referred to as Cycas media to which it is closely related. It can be distinguished from C. media by its usually more slender trunk, smaller leaves and larger seeds. C. megacarpa is also closely related to C. ophiolitica but differs by having uncrowded leaflets and larger seeds. The detail of these differences are presented in Table 3.10.1.
Table 3.10.1. Characters distinguishing Cycas megacarpa, Cycas media and Cycas ophiolitica.
Seed size (cm)
4-6 x 3.5-4.5
3-4 x 2.5-3.5
3-4 x 2.5-3.5
3.10.3 Current conservation status
C. megacarpa K. Hill is presently listed on the schedule of the Queensland Nature Conservation 1992 as “vulnerable wildlife”. However, a change in conservation status from Vulnerable to Endangered on the Queensland schedule is pending. It is listed on Schedule 1 Part 1 (endangered) of the Commonwealth Endangered Species Protection Act 1992. The species has not been assigned a national conservation status by ANZECC (1993).
3.10.4 Distribution and abundance
Details from Queensland Herbarium specimens of C. megacarpa are listed in Appendix 1.9. A total of 26 specimens of C. megacarpa have been collected from Many Peaks and Calliope Ranges, south of Gladstone, to near Kilkivan. Another six specimens collected from the Mt Morgan area have been identified as intermediates between C. megacarpa and C. ophiolitica. There are also 47 unvouchered locality records within its known range in the CORVEG database. Over its range it is recorded from two National Parks and from seventeen State Forest areas. Other localities are on road reserves, freehold and leasehold land. There is no quantitative data available on population sizes, although it has been reported as being rare to very common at the collection sites. The distribution of C. megacarpa has a range of approximately 240 km and encompasses an area of occurrence of approximately 28000 km2.
C. megacarpa is most commonly found in eucalypt woodland or open forest, and rarely in hoop pine dominant rainforest or on rainforest margins at altitudes of 40 to 500 m. It occurs on undulating to hilly terrain either on gentle to steep slopes and hill crests. The soils are generally well drained, shallow, often stony, sandy loam to clay loam in texture and derived from sandstones, fine grained sediments and acid and basic volcanic rocks. The more frequent tree species recorded with this species are Eucalyptus crebra, Corymbia erythrophloia, C. citriodora and E. melanophloia.
There have been no studies into the biology or autecology of C. megacarpa. The majority of the following information is extrapolated from our understanding of other cycads. However, it is also becoming increasingly clear that the reproductive processes and behaviour of different species within the same genus may differ considerably, so that information collected for one species cannot necessarily be extrapolated to another.
C. megacarpa is a dioecious, perennial plant that reproduces by sexually produced seeds. The longevity of the plants is unknown. Estimates of life span of other cycads range from 120 to 1500 years (Benson and McDougall 1993, Pate 1993). Coning has been recorded occurring in C. megacarpa from May to January. The factors controlling the level of reproduction are unknown. There are reports suggesting a cyclical nature to the level of reproductive episodes (Jones 1993, Vorster 1995). It is suggested that variable rates of coning will in turn lead to variable rates of seedling recruitment. The level of survivorship from seed to adult is unknown. Other cycad species have been reported to have levels of 3-4 percent survivorship with the greatest mortality occurring from seed germination to seedling stage(Connell and Ladd 1993).
Traditionally cycads have been thought to be wind-pollinated (Chamberlain 1935), but evidence has been mounting that most cycad species are in fact pollinated by insects, specifically by beetles (Tang 1987, Norstog and Fawcett 1995). Ornduff (1991) reported small beetles and small weevils present on male cones of C. media. However, whether these insects are involved in pollination remains to be determined. He also observed that the cones were visited by small bees (Trigona sp.) which were collecting pollen.
The seeds have a light brown thin fleshy outer layer and fall from the sporophyll at maturity. It has been reported that the fleshy outer layer attracts animals which feed on this fleshy tissue and secondarily disperse the seed. Possums, kangaroos, wallabies and rodents have been reported as dispersal agents for Macrozamia species (Jones 1993).
The seeds of most cycad species will not germinate immediately on maturity, as the embryo requires an after-ripening period (Jones 1993). Jones (1993) reported that generally species of Cycas require an after-ripening period of six to twelve months and that germination usually takes twelve to eighteen months. The length of time that the seeds of C. megacarpa retain their viability is unknown. It is reported that Cycas seed in general has a limited period of viability (Jones 1993).
As germination occurs the micropylar end of the hard seed coat is ruptured by the emerging radicle, which turns down into the soil and grows rapidly. The greater part of the cotyledons remain inside the seed on the soil surface, absorbing all of the endosperm and transferring the food resources into the young root and developing underground stem of the seedling. Usually only one leaf appears initially at the soil surface some months after germination. The length of time taken from seed germination to maturity is unknown. The time taken to reach maturity for cultivated cycads ranges from 2 to 30 years (Jones 1993).
From field observations it is suggested that seeds and the early stages of the seedling development are fire-sensitive. The time required before the seedling can tolerate fire is unknown. Mature plants are not greatly affected by fire apart from the loss of the entire crown of leaves. There are some suggestions the some cycads may benefit from periodic exposure to fire (Zunckel 1995).
C. megacarpa is capable of reshooting from the base of the trunk if the growing tip is killed.
There is no doubt that past habitat alienation for agriculture in the species’ geographical range has led to a decline in populations. Those populations on freehold and leasehold land are still potentially threatened by clearing for agricultural development.
The leaves contain toxic compounds which when ingested cause poisoning in domestic stock. Poisoning is often more prevalent in dry seasons when other feed is scarce. In the past landholders were encouraged to destroy cycads and many rural landholders continue to take measures to eradicate cycads from areas where domestic stock graze.
Cycads world-wide have become extremely desirable plants to collect. Cycad populations have also declined in the past as a result of removal of plants from the wild by nurserymen and cycad enthusiasts. C. megacarpa is potentially threatened by the illegal removal of plants from the wild.
Mature cycads generally cope very well with fire and as pointed out earlier may benefit from periodic exposure to fire. However, fire can certainly affect the recruitment of new individuals because the seeds and young seedlings of C. megacarpa are fire-sensitive. The limited knowledge available on the effect of fire and species’ response makes it difficult to assess the total impact of varying fire regimes. However, too frequent a fire regime would lead to a gradual decline in the population as mature plants became senescent and there was a lack of recruitment of new plants.
3.10.8 Management, research and conservation measures
Field surveys should be conducted in areas where the species has been recorded in the past to assess population levels.
There is little information available on the role of fire in the ecology and reproductive biology of C. megacarpa. This needs to be understood if successful management techniques are to be developed for the effective conservation of the species in the wild. Research into the effect of fire on coning and seedling survival is required.
To reduce the illegally removal of plants and propagules of C. megacarpa from the wild, locality information on populations should not be supplied to persons who do not have appropriate permits from Department of Environment and Department of Primary Industries. Current legislation to prevent illegal collection of threatened species from the wild needs to be enforced.