Notes from the field: finding Lapeirousia pyramidalis

Color variability in a population of Lapeirousia pyramidalis subsp. regalis

The reason of my field trip to the Cape was to study Lapeirousia pyramidalis. This plant species occurs in two subspecies: subspecies regalis, with mostly purple flowers, is distributed within a 80-km-long, ~1-km-wide stretch of the succulent Karoo region, along the Olifants river and West of the Cederberg; subspecies pyramidalis has mostly white-pink, scented flowers and is widespread in the Karoo East of the Cederberg. The two subspecies differ also by their pollinators: long-tongued flies for subsp. regalis and moths for subsp. pyramidalis.I was oblivious of the existence of this plants until after I moved to South Africa and chatted with Prof. Bruce Anderson, one of my local collaborators. While discussing my research project, Bruce mentioned that L. pyramidalis shows a high variability in floral traits such as flower color, shape, and tube length not only between subspecies, but also within subspecies and even within populations. Since my research aims at finding the drivers of such a floral variability within populations, Lapeirousia pyramidalis sounded like a good species to focus on.
For studying L. pyramidalis, one must first find it. To this goal, my first move was to visit the Compton Herbarium in Cape Town (by the Kirstenbosch Botanical Gardens), go through their specimens, note the place of collection and hope that the plants were still there. In the case of Lapeirousia, the task of locating and recognising the species is eased by a monographic book recently written by Goldblatt and Manning (http://biodiversityadvisor.sanbi.org/wp-content/uploads/2015/11/Strelitzia_35_2015.pdf). The book’s maps and drawings made my life, a clueless European ecologist’s recently moved to studying South African flora, easier.

Lapeirousia jacquinii

In spite of having this knowledge on my side, hunting Lapeirousia pyramidalis populations around the Cape did not happen without a learning curve dotted by hilarious mistakes. For example, I found my first population of “L. pyramidalis subspecies regalis” while still in Florent’s company. We were on our way to Namaqualand when we stumbled on a beautiful, large, dense population of purple-flowered Lapeirousias in full bloom. We stopped in awe and started taking measurements: tube length, nectar volume and sugar concentration for a few tens of flowers, plus plant community composition. I wrote all this down on my tidy, freshly-printed data sheets, and we left. That very evening we looked for the data sheets to check a few measurements. They were nowhere to be found. A few hours of work, my first batch of precious data, as well as tens of untouched data sheets were vanished. I was probably the last one handling the sheets, so I was feeling responsible and ashamed as a thief. I would have driven back to recollect the data if Florent did not convince me otherwise. Luckily for us, on our way back two weeks later, the “regalis” population was still flowering. We recollected the data and set to Cape Town, my heart a bit lighter.
You might be thinking: “so you lost some data and you recollected them. It happens. What was so hilariously wrong in all this?” Well, it took us another week to check the pictures we took that day and realize that the “regalis” population we made such a fuss about was not regalis but Lapeirousia jacquinii, a different species with similar flowers.

Color variability in a population of Lapeirousia pyramidalis subsp. pyramidalis

A similar event happened a few weeks later in the semi-desertic area of Tankwa Karoo. I was sampling L. pyramidalis subspecies pyramidalis, white and scented, when I stumbled in what looked like a mutant version of it. As I wrote in an excited email to the professors I’m working with: “the latest finding: dwarf, geophytic [Lapeirousia pyramidalis] plants with short-tubed, almost actinomorphic flowers and no trace of the typical pyramid-like shape.” I thought I discovered a new species. A few evenings later, sipping coffee with a farmer friend of mine and looking through a flower guide of the area, we saw my “newly discovered” species: it was Lapeirousia plicata, first described in 1795.

Lapeirousia plicata

Click here for more pictures of Tankwa Karoo: