After another day identifying all the unidentified Solanaceae in both the herbarium of the Instituto and the Universidad Nacional de Cuyo, we went in search of Solanum juncalense, a species we had been looking for on previous field trips in the Mendoza area.
I had accumulated much locality information for this solanum in the herbaria – we have very few collections of this species in the Museum’s collections, so my work in the collections here in Mendoza has really helped my understanding of its distribution and variation. One of the localities was in the department of Tunuyán, up the valley from where Claudio’s parents had a farm. We had intended to spend the day there anyway, so went in search of Solanum juncalense – the last chance to find it!
Today was the first Sunday of a long holiday, and everyone was out with tents camping or barbeques having a Sunday asado in the countryside. We headed up the valley, on a road that crossed several streams – a bit worrying, as it had rained every day and the arroyos grow quickly and become impassable. We carried on past a guardia post where we had to leave our names to a confluence of two valleys – one of the localities I had found in the herbarium yesterday.
The valley is called Cajón de los Arenales, and is the jumping off place for the ascent of the mountain at its head
And there it was…. at the side of the road, right where we parked the car was Solanum juncalense in full flower. The botany gods were smiling on us for sure….. everywhere else we had been looking for this we had looked in vain, but there it was!
Solanum juncalense is a member of the Morelloid clade Tiina and I are currently working on, and an endemic to this part of Argentina and adjacent Chile (although I think the one Chilean collection is actually from the Argentine side of the border!). It is a relative of Solanum sinuatiexcisum, which we collected high up in the northern Andes of Argentina last year
Solanum juncalense is a member of a species complex that I thought I understood before I saw the material here in Argentine herbaria. Previous taxonomic treatments distinguished the species by length of hairs (tiny to extremely tiny!!) and colour of flowers; I thought I had found another difference when I was in Córdoba, but looking at the many herbarium sheets of these plants in Mendoza I am now thinking this is all a cline – variation from north to south that is continuous, and not several species at all!
In addition, these plants we found sometimes had white flowers and sometimes purple (more commonly purple… but both colours were there!). So maybe I am more confused now than I was before, but maybe not, at least now I know what to look for….. If I am right and this is all just continuous variation, then the correct name will be Solanum echegarayi, published a few years before Solanum juncalense.
The size of the plant had also been important in previous treatments, and plants were described as annuals. But how wrong…. these plants all grow from deep underground rhizomes (underground stems) and shoots grow up from buds along the stem to reach the surface, a bit like a potato grows from the eyes on the tuber. One of the rhizomes we dug up was about 1 centimetre in diameter and very corky. The snow is very deep in this area in winter and the plants die back to survive from Another example of why field work is so important – these sorts of characteristics are just not apparent from herbarium specimens, and are often not noted down on labels.
Several different 'plants' of Solanum juncalense are sprouting from this rhizome – if a collector just pulled at the above-ground stem it would seem it was an annual plant!
I would have liked to dig some more and see if all the plants in one area were connected, but we needed to get back before the arroyo began to flood (we could see it raining up higher). In addition all the plants we found were growing in the loose soil of ant nests; the ants were not at all happy with us disturbing them and they both bit and stung. Apologies to my hymenopterist colleagues for not collecting them, all I could think of was to get them off me!
What a find though for my last day in Argentina – this time. This is an amazingly diverse and fascinating country, with many endemic species and genera of Solanaceae. I have great colleagues here in Argentina – Gloria and Franco in Córdoba and Iris in Mendoza – so I am sure I will be back….. but this has been a wonderful field trip, topped off by a great find and some new discoveries about the plant!
Iris Peralta and her husband Claudio Galmarini in Cajón de los Arenales