Three decades of research on Kimberley orchids

The remote Kimberley region in northern Western Australia is famous for its rugged gorges and isolation. With a strong seasonal climate, including a nine month dry season, one might think there is little habitat available for orchids, a diverse group of plants that usually require very specific environmental conditions to thrive.

Photo: Cymbidium canaliculatum, the most widespread orchid in the Kimberley region.

Yet careful searching during the wet season, with helicopters, 4WDs, quad bikes and on foot, has located twenty orchid species in the region, documented in a new research paper, with potential for even more discoveries in the future. Three epiphytes, or tree orchids, and seventeen ground orchids have been recorded so far.

Photo: Spinifex (Triodia) tussocks on a sandstone pavement providing habitat for Calochilus barbarossa and Phoringopsis byrnesii in the Prince Regent National Park.

Finding orchids in such a remote region can be a slow process, and this research has taken 30 years to reach publication. Many people have assisted with the search over the decades, particularly Kimberley locals Robin and Butch Maher, both with a keen eye for potential habitats, and crucially, a helicopter at hand.

Photo: Butch Maher on a collecting trip in the north-west Kimberley with the Barrett brothers.

One of the key challenges in understanding species diversity has been the many connections between the Kimberley, South-east Asia, and other parts of northern Australia. Establishing sound species concepts requires an understanding of morphological variation over vast distances, often with limited collections available.

Four new species are described in this paper, three endemic to the Kimberley region, Calochilus kimberleyensis, Dipodium ammolithum and Dipodium basalticum, while Calochilus barbarossa is also found in the Northern Territory.

Photo: Kingsley Dixon, Lionel Johnstone, Pat Dundas and Matt Barrett with the newly discovered Calochilus barbarrosa on the bonnet of the Barrett family landcruiser in 1994.

Some sites contain multiple orchid species, particularly a seasonally wet woodland habitat dominated by a combination of White gums, Pandans, and Tropical Banksia over rich grasses and sedges. Here, species of Calochilus, Didymoplexis, Empusa, Eulophia and Pecteilis can co-occur.

A few species remain very poorly known in the Kimberley, with only a single location known for three of the ground orchids, Habenaria hymenophylla, Spiranthes sinensis, and Zeuxine oblonga. Only a single site has been recorded for the tree orchid Dendrobium foelschei, but the population was subsequently killed by a hot fire that scorched the Melaleuca trees it grew in, so this species may no longer occur in the Kimberley.

Photo: The only known location in Western Australia for the Rein orchid, Habenaria hymenophylla, is in a native Nutmeg forest in the bottom of a deep gorge which provides a stable environment for this rainforest orchid.

Fire frequency and intensity can threaten orchids by modifying habitats, especially through the reduction of humus content and soil moisture-holding capacity, critical for fungi that orchids rely on for germination, and key nutrients for growth and flowering. orchids like Didymoplexis pallens and Eulophia bicallosa can be easier to find after fire, when there is less grass to hide in, but that doesn't mean that fire is good for these species.

Feral animals also pose threats to Kimberley orchids, especially pigs. Pigs can target particular habitats, looking for roots and tubers, digging below the depth of orchid tubers, destroying both individuals and habitats.

Photo: Extensive disturbance to orchid-rich habitat by feral pigs searching for roots and tubers in the upper Prince Regent National Park.

Many orchid relationships remain poorly understood and new genetic data is likely to lead to additional name changes in coming years, and perhaps even additional species. Orchids such as Habenaria eurystoma occur in very discreet areas in Western Australia, the Northern Territory and Queensland, separated by 1000 km or more. It remains to be determined how long these populations have been separated, and whether more than one species should be recognised. Genetic data is likely to be crucial in answering such questions.

For now, we hope that this paper will increase our understanding and appreciation of Kimberley plants and landscapes, and promote further research.

Photo: Vine thickets and rainforest at base of sandstone cliff in Pitta Gorge, habitat for Dendrobium dicuphum, Eulophia picta and Habenaria hymenophylla, while the upper plateau provides habitat for Calochilus holtzei and Pecteilis elongata.

A gallery of all orchid species known to currently occur in the Kimberley is presented below.

Calochilus barbarossa (newly described). A. Habit. B, C. Flower. D. Capsule. E. Leaves at advanced anthesis. F. Close-up of leaf. G. Inflorescence. Photos by R.L. Barrett & M.D. Barrett.

Calochilus holtzei. A. Habit. B. Inflorescences. C. Flower being pollinated by a scoliid wasp (Radumeris radula). D. Inflorescence with open flower and developing fruit. E, F. Flowers showing variation in colour between populations. G. Developing fruit. H. Dehisced fruit. Photos by R.L. Barrett & M.D. Barrett.

Calochilus kimberleyensis (newly described). A. Habit. B. Inflorescence. C–G. Flowers. H. Fruit. Photos by R.L. Barrett & M.D. Barrett.

Cymbidium canaliculatum. A–C. Habit and habitat in broken branches of living eucalypts. D. Flowers. E. Fruiting plant. F. Inflorescence. G. Flower. Photos by R.L. Barrett.

Dendrobium dicuphum. A. Habitat. B–D. Habit. E–G. Flowers. Photos by R.L. Barrett & M.D. Barrett.

Didymoplexis pallens. A. Flowering plant post-fire. B. Fruiting plant on edge of burnt area. C. Whole plant including root system. D–F. Flower. Photos by R.L. Barrett.

Dipodium ammolithum (newly described). A. Habit. B, C. Inflorescence. D. Infructescence. E–G. Flower. Photos by R.L. Barrett& M.D. Barrett.

Dipodium basalticum (newly described). A–C. Habit. D. Inflorescence. E. Unidentified scoliid wasp pollinating flower. F, G. Flowers. Photos by R.L. Barrett & M.D. Barrett (A, D). & R. Maher (B, C, E–G).

Empusa habenarina. A, B. Habit. C. Pleated leaves. D. Inflorescence. E–G. Flowers. Photos by R.L. Barrett & M.D. Barrett.

Eulophia bicallosa. A, B. Habit. C. Pseudobulbs. D. Habitat and habit. E–G. Flowers. Photos by R.L. Barrett (A–C) & R. Maher (D–G).

Eulophia picta. A, B. Habit. C. Pleated leaf. D. Infructescence. E–H. Inflorescence. Photos by R.L. Barrett & M.D. Barrett.

Habenaria hymenophylla. A, B. Habit. C. Aerial rosette of leaves. D. Budding inflorescence. E–G. Flowers. Photos by R.L. Barrett.

Nervilia holochila. A, B. Pleated leaves. C. Inflorescence. Photos by R.L. Barrett.

Pecteilis elongata. A. Habit. B. Leaves and tuber. C, D. Inflorescence. E. Fleshy roots and tuber. F, G. Flowers. Photos by R.L. Barrett & M.D. Barrett.

Pecteilis eurystoma. A, B. Habit. C. Leaves, roots and tuber. D. Inflorescence. E–G. Flowers. Photos by R.L. Barrett & M.D. Barrett.

Pecteilis ochroleuca. A–C. Inflorescence. D–F. Flowers. Photos by R.L. Barrett & M.D. Barrett.

Phoringopsis byrnesii. A, B. Habit and habitat in Triodia clumps. C–D. Inflorescences. E–G. Flowers. Photos by R.L. Barrett & M.D. Barrett.

Spiranthes sinensis. A. Inflorescence. B, C. Close-up of inflorescence and flowers. Photos by M.D. Barrett.

Zeuxine oblonga. A. Habit. B. Leaf rosette. C. Base of stem and leaves. D. Inflorescence. E, F. Flowers. Photos by R.L. Barrett (A); G. Sankowsky (B–F).

Our research paper is freely available in the journal of the National Herbarium of New South Wales, Telopea (Download PDF here).