Author: Ambroise

Identifying a mysterious Lamiaceae from St Jean Cliffs

In July 2003, I collected and pressed an intriguing Lamiaceae while exploring the woodlands at the base of the St Jean Cliffs, Geneva, Switzerland. This was part of my personal efforts to develop my botany skills and explore Geneva’s urban biodiversity. The plant had the unusual characteristic to present ten calyx lobes, which pointed to the genus Marrubium. However, the plant did not match the only Marrubium known from Switzerland.

Asking my contact at the Geneva Botanic Garden did not lead to a specific identification neither. A few years later I brought my specimen to Reading Botanic Garden and helped by Ronnie Rutherford, I narrowed the identification to Ballota rupestris (Biv.) Vis. (syn. Ballota hispanica (L.) Benth.) of Italian origin i.e. not a Marrubium species and not a species recorded in standard Swiss Floras to my knowledge to date.

Population size and local flora

In 2003 and 2004, I returned to the site a few times because of numerous species of floristic interest present (Arabis turrita, Erysimum cheiri, Saponaria ocymoides, Tanacetum parthenium, Campanula alliariifolia, Campanula persicifolia, Smyrnium perfoliatum, Scrophularia canina)

I also revisited the site one time in winter in 2007-2009 and counted about a dozen plants of the mysterious Lamiacea in a thorough search for the plant by the path and on the slope between the path and the cliff base. Unfortunately, I lost the paper sheet with my notes from this latter visit.

Returning on the 23^rd of October 2022, I can report a healthy and growing population. The path has been substantially remodelled and improved for walkers, in addition, some of the slopes have been stabilised with geotextiles. There appears to be a much larger population than I remember and also plants of variable size, possibly indicating dynamic natural regeneration by seed.

The site was surveyed systematically for the production of the landmark publication : Flore en Ville – Sites et espèces d’intérêt en Ville de Genève (Plantes à fleurs, fougères, mousses et lichens), Mombrial F., Bäumler B., Clerc P., Habashi C., Hinden H., Lambelet-Haueter C., Martin P., Price M. & Palese R., (2013). The authors list 146 vascular plants, including seven species threatened at the national level. Moreover, they highlight the exotic character of the local flora which, they go on to write, is partly due to 19^th Century intentional introductions. There is historical evidence for a much more open habitat in the past and up to about 1900,and even vineyards.

The presence of Pseudodictamnus hispanicus (L.) Salmaki & Siadati certainly fits, in terms of exotism, but one can only speculate about the origin of the plant at this location. The first step to formulate a hypothesis would be thorough searches at the Herbarium of Geneva Botanic Garden and find out whether there are specimens pre-dating the one I collected in 2003. There is a very long tradition of botanising and collecting specimens to document the Geneva flora.

Distribution

In 2018, Siadati et al. resolved some of the taxonomy and nomenclature within the tribe Marrubieae and created the new combination Pseudodictamnus hispanicus (L.) Salmaki & Siadati for this species, which was previously widely known as Ballota hispanica (L.) Benth. (other synonyms can be accessed e.g. here). Despite the binomial’s epithet “hispanicus”, a search in Flora Iberica strongly suggest the absence of the taxa in in the Iberic penisula. The known native distribution is restricted to “Albania, Bulgaria, Italy, Sicilia, Yugoslavia” and the plant is unknown from other countries as a non-native organism.

Within Italy, P. hispanicus is only known from the southern parts (Calabria, Campania, Puglia and Sicilia). Therefore, the Geneva population expands considerably the distribution of the species. Information included in this note also confirms a continuous presence for a period of at least 20 years at the St Jean site, supporting a long-term establishment. Until more evidence emerges, we can assume a relatively recent introduction in Geneva (19 or 20 Century) and I would recommend the status of neophyte. In addition, I propose the French name ballote douce (referring to the French name for the closely allied genus Ballota, avoiding any reference to the confusing epithet hispanicum, or other synonyms, and describing the softness of the leaves to the touch and smell, contrasting with the other Ballota taxa in the area).

The binomial’s epithet hispanicus requires commenting, given the known distribution of the taxa. The specific name is inherited from Carl Linnaeus’s publication of Marrubium hispanicum in the second volume of Species Plantarum in 1753 (p. 583). Linnaeus wrote “Habitat in Hispania” for the species. There is clearly a geographical discrepancy between distribution and name, which will be explored further in the next section. A similarly confusing binomial coined by Lineaeus is that of Scilla peruviana, a species not at all from Peru, but an endemic to the Western Mediterranean that allegedly reached Northern Europe, where it was described, on a ship called “Peru”.

Why hispanicum for this taxa

The confusing nature of this botanical name has been discussed previously during the 20^th century and helpfully synthesised by Charlie Javis in 2007. The name Marrubium hispanicum L. has been applied to the Italian and Balkan taxa (i.e. what is now known as Pseudodictamnus hispanicus (L.) Salmaki & Siadati), based on a 1959 decision by the botanist Vernon Heywood to link this name to a herbarium specimen. This process of linking a name to a specimen is called “typification” in botany, the specimen becoming a “type”. Linnean names, such as Marrubium hispanicum, are typically typified retrospectively because the designation of a type specimen only became the norm in botany after c. 1900. Heywood’s typification in this case linked the name M. hispanicum L. to a specimen belonging to a species unknown from Spain.

The roots of the problem may be traced to Linnaeus’s original description in Species Plantorum, published in 1753, and potentially a poorer understanding of the range of species in this group of plants at the time. The description provided for Marrubium hispanicum matches better the Italian taxa, than the specimen within Linnaeus’s collection that is labelled as M. hispanicum. However, it is important to note that the M. hispanicum description in Species Plantarum is not incompatible with Pseudodictamnus hirsutus, from Spain, the taxa appearing on Linnaeus’s herbarium sheet labelled Marrubium hipanicum L. However, it is to be noted that Linnaeus did not work solely with his own collection of specimens and it may not be ever possible to fully clarify his exact intentions and knowledge of these taxa at the time.

We may be stuck with a confusing name, for what is a lovely species, now know to have wider distribution range.