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The flight to Mendoza was short and sweet, and I was met by my colleague Iris Peralta, with whom I had written a monograph of the tomatoes and their wild relatives when she was in London on a post-doctoral fellowship in 2001. We spent the afternoon in the herbarium, looking at the Solanum and Nicotiana from Mendoza province to see where was best to go in the field over the next few days.

 

Our first field excursion was to the valley of Cerro Aconcagua. Pablo Molina, a new PhD student studying the phylogeny of cacti and their close relatives the purslanes (Portulacaceae) came with us to look for his plants as well! The peak of Aconcagua is at almost 7000 m above sea level, making it the tallest peak in South America. The area around Mendoza and into the high mountains is a high elevation desert – the vegetation is of shrubs and grasses, and at higher elevations vegetation is almost absent.

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The vegetation on the way up the valley to Uspallata is dominated by creosote bush (Larraea); this genus also occurs in the deserts of California and Arizona in the USA

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All along the roadsides in the disturbed soil we found Nicotiana noctiflora – we were early enough in the morning to see the flowers still open; at one site a nectar-robbing carpenter bee was carefully alighting on each flower and biting a hole in the base to suck out the nectar – this species flowers at night (hence the name!) and is pollinated by moths

 

Although the area is arid and dry, in winter it is snowy and the pass over the mountains to Chile (this is a major connection between the two countries) is often closed; all up and down the upper parts of the valley were ski areas, very popular in winter. The region has been shaped by the action of glaciers and landslides – ancient rockfalls and terraces were easy to see with the light vegetation cover.

 

We came to Puente del Inca – now I truly felt I was following Darwin around! After the Beagle had rounded the tip of South America, the ship suffered damage that had to be repaired. They docked in Valparaiso, Chile to repair the damage. Darwin took two men with him and rode over the Andes and then to Mendoza, riding back across the Andes into Chile along exactly the same valleys we were driving along. He described the unusual geological formation of the Puente del Inca beautifully in his book about the voyage of the Beagle.

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The stone bridge over the river was formed from the concretion of chemicals from a thermal spring – this was the site of a thermal spa in the early 20th century with a posh hotel and baths. An avalanche completely destroyed the hotel (to the far right in the picture) but spared the church

 

Our first sight of Cerro Aconcagua came at Quebrada Horcones – it was a completely cloudless day – we were very lucky, the peak is often shrouded in clouds. What a mountain. Climbing it is tightly controlled – every year climbers die and they are buried in the “Cemeterio del Andinista” in the valley.

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Quebrada Horcones is one of only a few places where climbers begin the ascent – apparently the record climbing time is 15 hours, incredibly speedy, most take longer and spend the night on the glaciers

 

Although we a lot of locality information for the Solanum and Nicotiana we were seeking, they were nowhere to be found. Like Patagonia, it was very dry, so we suspect it has been a bad year. We did find several of the purslane species Pablo and Iris were seeking though, on the way up an incredible set of switchbacks (called caracoles – snails – in Argentina) to a pass at 4000 metres.

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Montiopsis andicola was named by John Gillies, a Scottish botanist who, between 1823 and 1828, explored this region botanically for the first time; this entire plant is smaller than a 5 pence coin!

 

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The switchbacks to the statue of the “Cristo Redentor” were amazing – but the road had been fixed so it was full of cars and microbuses, the tourists in summer clothes had a shock at the top in the cold wind

 

Our amazing day ended with a new route back to Mendoza, along the way we collected some Fabiana for Iris’s PhD student at an amazing petroglyph site.

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It had rained as we came down the valley from the high mountains and the resinous foliage of this species had a wonderful incense-y smell

 

Our last stop was at the plaque Iris and colleagues had organised to commemorate Darwin’s travels in the area. The plaque sits in the site of a petrified forest that Darwin described…  it was quite moving to think of him on horseback seeing these same hills and the same vegetation. Seeing it myself brought it home to me how much his entire experience in South America must have shaped his ideas, not just the Galapagos.

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Just behind the plaque we think we found the Solanum I was looking for, but only as tiny plants just breaking the soil…..  frustrating, but I hope we find it elsewhere in the region, it seems to be common, but might just be fussy and not grow some years. What a day…. and at the very end, the mountain let us see it again from the top of the pre-cordillera, an ancient range just to the east of the Andes themselves, we were indeed very lucky!

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After our sauna unloading the truck at the Instituto we got all our plants and equipment up to the herbarium – just in time it turns out! The skies that had been dark as we were unloading opened in a truly impressive storm – thunder, lightning and hailstones the size of golfballs! A few hours later, the sky was clear again, and the air had cleared a bit.

 

The flora of Argentina

Gloria and I spent the rest of that day and the weekend looking over Solanum species for our joint treatment of the genus for the flora of Argentina. The new flora will be a guide to all the plants of the country, and will be a modern treatment with illustrations and descriptions of all the species.

 

Sometimes scientists feel that flora writing is not as important as evolutionary studies, or molecular biology, but they couldn’t be more wrong. A good flora allows local scientists (and those from outside the region) to identify plants so that new studies can begin locally, and if done well, can reveal problems that can’t be solved in the timespan of a flora, but can form the basis for postgraduate work in local universities where field work can be undertaken more easily than from a European or North American university.

 

Solanum synonymy

We had a couple of really tricky problems in the group we were both working with and took advantage of our time together to discuss them with all the specimens from the Córdoba herbarium in front of us. One of these problems was that we had decided earlier to recognise two species in the Morelloid group (the black nightshades) that had greenish black fruits that fell with their stalk – Solanum cochabambense and Solanum aloysiifolium.

 

This time in Patagonia we had not collected any of these plants, but had some questions about some of the synonyms. A synonym is when a plant receives two names from two different (or even from the same!) botanists, and a later worker in the group decides that both names represent part of the same entity. The name that was published first has priority, and so the second one becomes a synonym.

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Solanum aloysiifolium

 

One way of deciding synonymy is to look only at the type specimens and see if they are similar, but a better way to assess this is to look at as many specimens of the group in question as possible. This way, one can see if the type specimens, that might look quite different if they come from the extremes of variation, are connected by continuous variation in different characters. The great advantage of being in Córdoba for this was that since these are common Argentine species, there was LOTS of material to compare.

 

We went back and forth trying to separate the masses of specimens into piles that corresponded to the types, and in the end, decided we couldn’t do it reliably with the data to hand. So, for the flora, we will recognise these as a single species with the name Solanum aloysiifolium (described in 1852, while Solanum cochabambense was described in 1912).

 

The complex pattern (or non-pattern) of variation needs close study by a local student who can go in the field regularly and can also bring seeds and plants back and grow them in a common garden – we suspect some of the differences we can see are environmental in nature. For example, plants with larger leaves are always found in wetter forests, and other characters seem to vary in the same way.

 

It might seem a bit of a cop-out to not resolve this problem here and now, but making these decisions is a practical compromise – the flora needs to be finished by a particular date, and best of all, we now have a great project for a student who likes plants and field work!