The large-leaved Aciphylla speargrasses or taramea are difficult plants to collect. Their rigid leaves are tipped in a sharp point and the bracts on their flower spikes are similarly ferocious. These defences are thought to have evolved to avoid browsing by moa, but they also work against botanists! Consequently, speargrasses are under-represented in plant collections (herbaria). Te Papa Research Scientist Lara Shepherd and Botany Curator Leon Perrie describe how they approached sampling speargrasses on their recent collecting trip.
Our research into the taxonomy of speargrasses requires us to collect leaves and flowers for analysis. Not only are speargrass leaves sharp, they also form rosettes, where leaves radiate from a central point. This make accessing the bases of the leaves and flower spikes even more challenging.
For each plant included in our study, part of a leaf was preserved for DNA analyses and a whole leaf or rosette pressed to make a herbarium specimen, along with flowers or fruit where available.
Many speargrass species have outgrowths called stipules near the leaf base. Stipules are a potentially important character for distinguishing between some of the species. However, in order to collect the stipules we had to reach right into the centre of the speargrass plant – a potentially dangerous prospect!
Safety first in the field
Prior to embarking on our fieldtrip we purchased safety glasses and cut-resistant gloves. These provided protection for our eyes and hands. We also found walking poles useful for directing the pointy ends of the leaves away from our faces when reaching into a speargrass rosette to extract a leaf.
When collecting non-spiky plants we usually cut off leaves or shoots with secateurs. However, our preliminary sampling of speargrasses revealed that it was much easier to carefully reach into the centre of the speargrass rosette and cut off a leaf with a knife. For smaller speargrass species we used the knife to remove an entire rosette.
Spiky speargrass storage
Once a leaf (and flowers) were removed, the next challenge was to transport them back to the vehicle. We discovered pretty quickly (and painfully!) that leaves and flower spikes placed directly into our backpacks could easily puncture the material of the bag (and the skin of the bag wearer!).
Instead, we found a better option was to transport the leaves in a telescopic artist tube. The tough plastic of the tube was not punctured by the sharp leaves but it was lightweight enough to carry on an 8-hour tramp. To fit the leaves in the tube we labelled each leaf and tied it up to make a ‘speargrass roll’. This way we could fit leaves from multiple individuals into the tube.
The next step in the process was to press the leaves and flowers between paper in a plant press. This flattens and dries them out. Care was also required during this stage to avoid the sharp points of the leaves and bracts.
Herbaria on the road
The leaves and flower stalks of speargrasses are quite fleshy and difficult to dry. If they aren’t dried quickly, they can go mouldy and rot. Fortunately, the staff of the Allan Herbarium at Manaaki Whenua kindly let us use their plant dryer to dry our specimens. We passed by their Lincoln base several times during our six-week trip through the South Island.
Our specimens are now back at Te Papa and in the process of being added to the museum’s herbarium collection. Each specimen is databased, mounted on archival card (which also requires care not to get pricked!), imaged, and filed away.
Having harvested Aciphylla aurea biomass samples as part of a tussock fire project in Otago, I found a sharp spade was the way to go.
While “These defences are thought to have evolved to avoid browsing by moa, ” another published train of reasoning is the possibility that the spikes evolved through a morphogenetic process (such as biased gene conversion). Moas may not have been able to feed on the plants as a result, but the moa browsing itself was not the evolutionary mechanism.
Always enjoy your blogs Lara and Leon. Some inventive stuff needed for this work. Thanks for sharing.