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A weekend in the herbarium – Córdoba

Posted by Sandy Knapp on Feb 9, 2013 6:46:17 PM

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!

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