12 December 2018

Hunting the wild tobaccos

Kew’s Mark Chase discusses a diverse group of wild tobacco species found in a challenging environment…

Mark Chase

By Professor Mark W Chase

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From South America to Australia

The native Australian species of tobacco (Nicotiana section Suaveolentes) originated in South America and are thought to have arrived in Australia about six million years ago via long-distance dispersal on bird feet and feathers. Some species are used by Aboriginal people as chewing tobacco (mingkulpa or pituri), and thanks to their attractive, scented flowers they have potential in horticulture. This group of species is unexpectedly diverse and can tolerate dry conditions. The research being undertaken at Kew is focused on how these species  survive in the arid “red centre” of Australia. This major collaborative project between Kew (led by me) and colleagues in Australia, Austria and Brazil is tackling this puzzling phenomenon. 

Man kneeling beside plant.
Mark with Nicotiana gossei, growing on Uluru (Uluru-Kata Tjuta National Park, Northern Territory). Image © Maarten Christenhusz / RBG Kew.
Nicotiana velutina growing in a highly exposed site in a fossilized red sand-dune in central South Australia.Image © Maarten Christenhusz / RBG Kew.
Rocky outcrop covered with plants.
Nicotiana benthamiana growing in protected rocky sites on sandstone cliff faces, Western Australia. Image © Maarten Christenhusz / RBG Kew.

Unexpected diversity in the outback

All Australian tobacco species originated through doubling of chromosome number (from 12 to 24 pairs), a process known as polyploidization. Originally, the world-traveling ancestors of the Australian species grew under relatively mild, humid conditions around the northern and eastern coasts. Then, about two million years ago they moved into the outback. Put simply, my research is focused on answering the question: how do thin-leaved herbaceous plants survive in some of the driest places on the planet? 

When I started on this project in the late 1990s, it was thought that there were about 21 species of tobacco in Australia, but during my programme of fieldwork, collecting material of each species for use in genetic studies, it soon became obvious that many of the plants did not fit into any of the known species. My colleagues and I now believe there to be about 45 species! 

This diversity was hidden by their variable response to moisture availability. In years with adequate precipitation, these plants can grow up to more than a metre tall, with multiple branches and many flowers, whereas in dry years the plants produce only 1–4 flowers – in drought years, no germination occurs. Growing these plants at RBG Kew has allowed me to study their morphological differences under standard conditions. Twelve species, including four newly recognized, are featured in the latest issue of Curtis’s Botanical Magazine (illustrated beautifully by Deborah Lambkin), and the genetics of the group is now being studied using cutting-edge DNA techniques.

Two paintings of foliage.
Two of the recently described new species, as painted by Deborah Lambkin. Left: Nicotiana karijini, native to the Karijini National Park, Western Australia; right: Nicotiana faucicola, native to the Flinders Ranges, South Australia.
Men walking along shaded hillside.
Mark and a National Park Ranger climbing Uluru in search of Nicotiana gossei (Uluru-Kata Tjuta National Park, Northern Territory). Note the generally flat landscape with red soil. Image © Maarten Christenhusz / RBG Kew.

Exploring demanding areas

Sporadic germination and remoteness of their habitats have made fieldwork challenging and sometimes frustrating. Many months in advance, applications for permits have to be submitted and flights to Australia arranged, and if there is no rain in the intervening months, the chances of finding plants are decreased.
Health and safety considerations mean that my team is required to send a message twice a day via a satellite tracking-device with our location. Mobile phones are of little use in the Australian outback, and it is not unusual to drive for a whole day without seeing another vehicle. Despite these challenges, our fieldwork has taken us to fascinating places that most Australians haven’t visited, and following good winter rains the flora can be amazing. We’ve also had many opportunities to learn first-hand about Aboriginal culture, and we were even given their permission to collect material of the species known locally as mingkulpa (Nicotiana gossei) on Uluru (Ayer’s Rock), which is a sacred Aboriginal site.

References

Chase, M.W. & Christenhusz, M.J.M. (2018). Nicotiana karijiniCurtis’s Botanical Magazine 35: 228–236. Available online

Chase, M.W., Conran, J.G. & Christenhusz, M.J.M. (2018). Nicotiana faucicolaCurtis’s Botanical Magazine 5: 237–244. Available online

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