Australia: A living laboratory for carnivorous plant research

Australian carnivorous plants

Australia is a known hotspot for carnivorous plant diversity, with six genera (Aldrovanda, Byblis, Cephalotus, Drosera, Nepenthes and Utricularia) occurring there. Of these genera, Drosera and Utricularia make up the bulk of carnivorous plant diversity in Australia.

Droseraceae

All species within the family Droseraceae are carnivorous. Two genera only have one species; Dionaea muscipula (venus flytraps) are endemic to the United States of America, while Aldrovanda vesiculosa (waterwheel plants) are more cosmopolitan, occurring in Australia, Africa and Eurasia. A third, highly diverse genus, Drosera (sundews) use 'flypaper traps' to capture prey and are endemic to all continents except Antarctica.

Drosera are most diverse in Australia, with over 160 species (ca. 60% of the global diversity) occurring within nutrient deprived environments in dry sclerophyll woodlands, tropical environments, alpine regions, heathland and acidic bogs. Despite the significant species diversity and diverse habitats, comparatively little is known about the finer scale evolutionary relationships between Drosera species in Australia.

Drosera aberrans

Drosera zonaria

Drosera orbiculata

Carnivores under threat

Some Drosera are highly vulnerable to environmental changes and are known from only a small number of populations. A recent paper highlights how these sites are precious resources that are often threatened by land use changes, rising salinity, eutrophication and other degrading processes. Researchers are constantly discovering and describing new Australian Drosera species; seven new species were described in 2023, six of these had an elevated conservation rating.

The threat of illegal poaching for the carnivorous plant trade is also ever-present in the minds of researchers working on Drosera, with most opting to closely guard locality information, lest these species disappear from the landscape entirely.

Drosera hookeri

Drosera gunniana

Drosera neesii

Unusual interactions

In the years since the carnivorous habit of Drosera was discovered by Charles Darwin in the first book on carnivorous plants in 1875, many interesting and often complex interactions have been uncovered between animals and carnivorous plants.

A fascinating but poorly understood relationship occurs between Drosera and a group of carnivorous dicyphine mirids, commonly known as sundew bugs (Setocoris spp.). Remarkably, these assassin-bug-like mirids are immune to the sticky trichomes of their host plants, using them instead as a passive trapping mechanism to capture easy protein rich meals. Potential coevolutionary relationships between Drosera and Setocoris are currently under investigation, led by researchers at the University of New South Wales and the University of Adelaide. You can read a little more about these remarkable insects in Prof. Gerry Cassis' blog post here.

Setocoris on Drosera hookeri (left) and Drosera whittakeri (right) in South Australia.

Understanding Drosera evolution

While traditional taxonomic approaches using morphology remain highly valuable to distinguish Drosera species, these are often limited in their ability to unravel complex evolutionary relationships in great detail.

My research focuses on understanding the evolution of Australian Drosera using large molecular datasets over a continental scale. These data are particularly useful to understand morphologically variable species groups and can have meaningful conservation outcomes, as it is often difficult to conserve species without understanding where species boundaries lie.

Drosera binata, a highly variable species from Australia and New Zealand. Image CC BY-NC Jono Dashper on iNaturalist (www.inaturalist.org/observations/192880634)

To this end, I have spent my PhD years collecting material, visiting herbaria and sequencing hundreds of Drosera specimens from morphologically diverse species groups across the Australian continent and beyond. Data from these projects will be published over the coming months and years, which will shed light on the evolution of this iconic genus in Australia.

To keep up with these ongoing projects, please visit these links:

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