Overcoming Seed Dormancy By Animal Ingestion

The Native Currant (Acrotriche depressa) and Honeypots (Acrotriche serrulata) belong to an interesting group of Australian heath plants called the epacrids.Little is known about the pollination and reproduction of epacrids with seventy-eight species regarded as poorly known in Australia. Epacrids are widespread throughout southern Australia but are currently rarely involved in revegetation, as they are notoriously difficult to propagate both by cuttings and by seed.

Both the Native Currant and Honeypots produce tiny, tubular flowers with hairs at the tips of the petals.  Pollen is released within the flower tube before the bud opens.  As the petals open, the hairs scoop up the pollen and hold it above the face of the flower for pollinators (possibly insects) to collect. I am trying to identify pollinators for both plants because they must be present in areas where the plants are used in revegetation. Pollination of other epacrid flowers is known to involve lizards, vibrating bees, birds and possibly Antechinus species.

Honeypots is a fairly common species that grows in South Australia, Victoria, Tasmania and New South Wales.  The Native Currant is rare in some areas of South Australia, including the Southern Mt Lofty area, and is presumed extinct in Victoria.  Both species produce fruit, nectar and pollen that provide a food source for many different native animals so would be valuable inclusions in revegetation efforts.The Native Currant is used to make jam on Kangaroo Island and could be used as a possible native food crop if it were easier to grow.

The diet of Australian native animals has long included the epacrids. Thornbills, honeyeaters, possums and Antechinus also eat nectar from these plants.The berries produced by Honeypots and Native Currant are eaten by Australian wrens, quail thrushes, silvereyes, honeyeaters and parrots among other birds. Native birds that eat the fruit both distribute and fertilise the seeds within.

Only 2% of untreated Honeypots seeds will germinate this indicates some kind of seed dormancy. Scarifying seeds and using smoke water does not increase germination rates.Seed germination must be fast and predictable to justify the time and effort involved in the collection of seed for revegetation purposes.A seed treatment must be determined to overcome the dormancy of Honeypots and Native Currant if it is to be used in revegetation.

Little research has been carried out on the breaking of multiple seed dormancies such as those found in epacrids.

Passage through the digestive tract of animals subjects seeds to conditions that would not otherwise be experienced such as lack of oxygen, high acidity and interactions with gut microflora.Acid treatment is a laboratory method that has been used to overcome dormancy in some plants.

High acidity experienced in the gut of animals may increase germination rates of ingested seed in a similar fashion.

Bacteria and fungi within the gut of animals may act upon seeds passing through to overcome dormancy.

Germination is increased in at least three other epacrid species after passage through the guts of birds.

I have devised an experiment to determine whether the ingestion of seeds by animals increases the germination rates of the seeds of Honeypots and Native Currant.Sleepy lizards, possums and a black faced cuckoo shrike were fed fruit and the seeds collected from their scat and planted in bush soil. 

Many thanks to the Fauna Rescue carers involved who kindly supplied and fed the black faced cuckoo shrike that was undergoing rehabilitation through Fauna Rescue .This bird hopefully will be the key to overcoming the seed dormancy of the two plants, enabling their use in revegetation and thus supplying many other native animals with food.Cooperation between fauna carers and plant researchers can help to overcome seed dormancy found in many Australian native plants. This means more plants would be suitable for use in revegetation. Revegetated areas that are more diverse in plant species support a wider array of animals.  If food is more abundant, released animals have a greater chance of survival.

Melanie Schneemilch
Adelaide University