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Seeking nightshades in South America

32 Posts tagged with the species_discovery tag

Sierra de Santa Barbara

Posted by Sandy Knapp Feb 16, 2012

Another wonderful day exploring and hunting the wild solanums of Argentina! Some might think we were a bit crazy – but not as crazy as the chaps we met up in the puna near the dunes a couple of days ago (forgot to write about them) who were traversing Argentina on motorbikes from Tierra del Fuego to the Bolivian border – 5000 km each way!! - in 15 days; this definitely makes botanists look sane.


Today we went to a small mountain range in the eastern part of the province of Jujuy – specifically to look for a plant known only from its type specimen (Solanum fabrisii), to see if we could recollect it. We did – it turns out to be the same (we think) as a species someone described earlier (Solanum glandulosipilosum – great name); this makes it a synonym – not a mistake, but a different interpretation of the evidence to hand (a story for another time!). On the way – we saw spectacular scenery, this huge canyon had no roads or trails leading to it – tierra incognita – or so it seemed to us.


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Today has made us both think about why field work is so important for the science we do at the Museum; not only do we find new things and sort out who is who, but field work is essential for looking at the natural variation of plants in the wild. Take, for example, a species we saw all day today – Solanum “aloysiifolium” (in quotes because we are not quite sure what its correct name is yet!). We saw this plant all over the Sierra de Santa Barbara (and have before today), but each time it looks a little bit different – just like individual people look different in small details. Big leaves, small leaves; white flowers, purplish flowers….. This is variation – the very stuff of evolution. Seeing this species in many different places, and looking a little bit different every time lets us calibrate how we are defining species, and shows just how much variation there is in nature. Doing this together, all three of us can discuss what matters, what we see (and we all do see very different things!) and just how we might deal with the complexity of what we observe. Collecting specimens that we will later look at carefully in the herbarium will let us connect the differences we see in the field with the data we take from pressed specimens and from DNA sequences to come to decision about what constitutes this particular species – is this one species or three or seven?


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Collecting a species more than once is definitely NOT a waste of time! It does, however, mean we have more plants to dry every night on Gloria’s field dryer – here set up in our hotel in the town of Libertador   General San Martín; we set it up every night and it works a treat. Looking for electric sockets in tiny hotels in villages in out of the way places can be a challenge though…..


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Setting the scene...

Posted by Tiina Feb 2, 2012

We all like eating tomatoes and potatoes - what could be better than chips with ketchup ! But did you know tomatoes and potatoes are extremely closely related? Although a red juicy tomato looks totally different to a pale yellow potato, the two plants share much of their DNA.


Potato and tomato belong to a group of plants known as Solanaceae - the nightshade family. In actual fact, they are so closely related they belong to the same genus within Solanaceae, known as Solanum. Tomato is called Solanum lycopersicum L. in scientific latin, whilst potato is known as Solanum tuberosum L.



Other well known species in the group include the bell peppers, chili peppers, eggplants, petunias, and tobacco - yes, incredibly this strongly flavoured plant is related to commonly eaten yummy things! South Americans might know more fruits from the family, such as naranjilla (Solanum quitoense Lam.), or tamarillo (Cyphomandra betacea Sendt.) used for making preserves and juice. If you visit Mexico and indulge in local food culture, you come across another species from the family, tomatillo (Physalis philadelphica Lam.) which is used to prepare salsa for buritos, tacos and tortillas.


Below is a lovely phylogeny of the nighshades which illustrates how the species are related within the family. It's based on a small set of DNA data. It is still not complete as it only includes roughly 30% of all the species in the family. Our aim is to add more species as our research progresses. What you can see is that eggplant, tomato, potato and pepino are really closely related, and tobacco is the furthest relative of them all. Solanaceae_large_phylogeny_SMALL_for_blog.jpg



The nightshades were known to be a group of closely related plants before anybody even knew they are related based on their DNA. This is because all species in the group share a set of morphological characters. Some of these are very obvious such as flowers which are generally stellate, with five corolla lobes, and five stamens. The most clear character that unites the family is seeds. Seeds are small – think of tomato seeds! – flattened, kidney-shaped, and have puzzle-piece shaped cells if looked under a microscope. Most of seeds in the nightshade family have curled embryos. If you are curious, try looking at dried tomato seeds closely! You will see the impression of the curled embryo on the seed quite easily.



Other characters of the nightshade family are more hidden. For example, all nightshades have internal phloem which means that sugars produced in leaves via photosynthesis are transported down to roots inside the water transport system known as xylem. Most plants have an opposite type transport system where sugars are transported outside the waterpipe system.



Anyways, why all this ramble? Well, the thing is that we are about to go hunting for nightshades in the Andes! There are an estimated 4,500 species of nightshades in the world, and large number of these is found in the Andes. These are wild relatives of tomatoes and potatoes and such likes, some weirder than other, some with tubers, whilst other climb trees! There are still species remaining to be described, waiting in the forests and mountain sides for discovery. We will be travelling in the northern part of Argentina and in Peru over the next coming 3 months – our aim is to collect as many species of Solanaceae on our way. This time we are targeting the particularly poorly known species of the Morelloid clade in the genus Solanum, a set of roughly 60 species.

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