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On the Hunt for Hibiscus

Hibiscus-hunter extraordinaire Dr. Todd McLay, a recent addition to the Royal Botanic Gardens Victoria team, has been working on an exciting project in the sacred chambers of the Australian National Herbarium in Canberra and the National Herbarium of Victoria at Melbourne Gardens. A hibiscus aficionado, Todd has been poring over thousands of native Hibiscus specimens, using revolutionary DNA sequencing techniques to investigate the evolutionary history of the genus in Australia. 

Hibiscus (family Malvaceae) comprises over 500 species across the globe. Typically bringing to mind exotic, balmy climates, the roughly 100 Hibiscus species which naturally occur in Australia aren’t limited to the tropics – they can also be found in rainforests and arid climates. It’s the mysterious species endemic to arid regions that most fascinate Todd. Many of them have not been revisited since they were originally described from tiny collections made in the mid-1800s, some of them by the first director of the Royal Botanic Gardens Victoria and founder of the National Herbarium of Victoria, Baron Ferdinand von Mueller. 

Todd didn’t originally set out to work with native Hibiscus. “I did my masters in New Zealand working on a bizarre, rare parasitic plant (Dactylanthus taylorii). It’s basically a clump of tissue that produces a flower, and that flower is pollinated by the New Zealand lesser short-tailed bat which climbs around on its elbows. My PhD was, on the other hand, focused on native grass trees”. When the opportunity came up to work at the Australian National Herbarium, part of the CSIRO, focusing on Hibiscus taxonomy, Todd jumped at the chance. “It needed to be worked on. No-one has really looked at hibiscus in Australia for a long time, especially in the arid zone”. 

Part of his research was to look at these taxa and begin the long and involved process of databasing these rare and little-known species online, so people seeking more information regarding Hibiscus have an easily-accessible resource. “Previously there’s been no flora treatment for the Malvaceae family in general, so people don’t really have a resource to go to”. The other major part is a genetic component. Todd has used a high-throughput sequencing method to sequence over 600 genes from more than 300 herbarium sheets of Hibiscus and other related genera. The data has a number of uses, including helping to resolve the evolutionary history of Australian Hibiscus in different ecological biomes, and identifying new species of Hibiscus.  

The amount of new species that Todd has discovered is quite remarkable. “Basically what you do is you have a pile of herbarium sheets, and you go that looks like this, put it in one pile, that looks like that, put it in another pile. Eventually, you’ve divided the sheets into all these different piles of morphologies. I think I probably got about 40 new piles of species.” Naming the new species has proven difficult. “There are some rules. Actually, coming up with names for 40 species is pretty hard. So far, I’ve got three. One new species I described from Western Australia I’ve named after the little droplets of golden resin present on its leaf hairs, and for a new species from Queensland I’ve used a name meaning 'innocent' or 'delicate' because it’s a cute little plant.” Names can be based on physical and morphological traits, location-based, or you can name a species after a person. 

Todd’s work cataloguing and understanding biodiversity of Hibiscus is important for conservation. “A big part of it is trying to understand the ecology of Australia - there’s still massive gaps in our knowledge, especially in the arid zone.” As climate change escalates, so does the importance of work like this. “It would be nice to understand what we have before we lose it [due to climate change induced extinction], and try to stop these species from being lost. 

The rarest species Todd has identified so far is only known from one tiny population growing on a rockface in Kakadu, and if bushfires pass through the area, it’s likely the species will be totally eradicated. Rising temperatures in general are a massive threat. “These native arid Hibiscus are adapted to hot, dry conditions, but if the climate continues to get hotter, drier, and more volatile, we’re likely to experience species loss. There are whole ecosystems which rely on these species to survive, including pollinators like bees and butterflies. Some of these species might be also useful horticulturally, pharmaceutically –  even as a food source.”

Todd joins Royal Botanic Gardens Victoria as the Pauline Ladiges Plant Systematics Research Fellow, and will be continuing his work on native Hibiscus funded by the Australian Biological Resources Study, as well as a Eucalypt Australia funded project on Corymbia and Eucalyptus.

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