CES researchers discover a new plant species in Western GhatsWed, 2015-06-10 16:26
On discovering a new plant species
This was first published at Ecology Students Society blog "https://cesess.wordpress.com/2015/06/09/on-discovering-a-new-plant-species/"
In early 2014, Navendu Page published a paper describing a new species of woody plant from the Western Ghats. I spoke to him about the discovery of this plant and the work that went into describing it. This is the first part of a two-part interview. The paper is available here: http://biotaxa.org/Phytotaxa/article/view/phytotaxa.158.3.7
(Photos © Navendu Page; Illustrations © Shreekant Deodhar)
Hari: Did you know it was a new species as soon as you saw it?
Navendu: No, not immediately. When I saw its brilliant red fruits I knew rightaway that it belonged to Annonaceae, the Custard apple family. Annonaceae fruits are peculiar – each is made up of many fruitlets, which can either be clustered together like in Custard apple, or free like they are in this plant. I am familiar with most genera of Annonaceae in the Western Ghats, and this plant didn’t resemble any of them. So I knew it was something interesting.
H: Take us back to the discovery. When and where did it happen? What were you doing? Who else was with you?
N: This happened on 21st November 2010, around noon. I was doing fieldwork for my Phd in Kathlekan reserve forest, along with Sneha who was also doing her PhD research on birds. Kathlekan is close to Jog falls not very far from Honnavar. At the time, my friends from Bangalore – Sartaj, Jahnavi, Jayabharathy and Sandhya – were visiting. One day after finishing regular plot work, we decided to visit the forest along the backwaters of the Gairsoppa dam, in the downstream area of Jog Falls. From the crest of the Ghat we could look down into the backwaters and it looked beautiful. The forest guard who was accompanying us told us that there was a trekking trail to reach there and so we decided to go. It took us almost three hours to reach the banks of the backwaters – lovely low elevation evergreen forest. As we were walking I was looking at all the plants along the banks when I came across this climbing shrub which I had never seen before. I looked around and found many more individuals in the same area. Luckily a few had fruits and one even had a flower. From the fruit I could make out that it was a member of the Custard apple family. I took lots of photographs but I didn’t collect a specimen. You could call it a superstition – I feel that every time I see something that might be interesting and collect a specimen, it turns out to be uninteresting. So I have decided that I will only take photos the first time, and if it is something interesting then I will go back and collect specimens.
H: What did you do next?
N: Once I went back to Bangalore, I tried to identify it with available floras for the region – Flora of the Presidency of Bombay and Flora of the Presidency of Madras. These were written by the British and it is still what we use today. There are no floras as comprehensive as these for the region. But it didn’t match with any of the species in these floras. Then I decided to look up the Flora of Ceylon, again an old flora written by a Britisher. Sri Lanka and the Western Ghats have many plants in common. But in this too I didn’t find a match. Then I looked up this really old revision of Annonaceae of the subcontinent by this chap called King, published in the Annals of the Royal Botanical Garden, Calcutta. In that I found one genus, which was not recorded in any of the peninsular Indian floras, whose flower and fruit seemed to be similar to this plant I had found. Interestingly, only two species of this genus have been recorded from within India – one which is found in northeast India and the Andaman islands and another which is endemic to the Nicobar islands. I knew rightaway from looking at the flower that it wasn’t either of these species – the petals were much shorter. Also, normally in this family the petals occur in two whorls – an inner and an outer – and the outer petals are much longer in this genus. But in this plant the two whorls were of almost equal length.
H: So at this stage, you had narrowed it down to the correct genus?
N: Not yet. The Custard apple family is found all through the tropics. I wanted to check it against species from other parts of the world. There is this person called Lars Chatrou who has made morphological keys for Annonaceae genera on all continents – South America, Africa, Asia, and Australia. I looked these keys up and found that it matched again with the same genus – what was earlier called Oxymitra and is now called Friesodielsia. Interestingly, I found this genus both in the African and Asian keys, which means that members of this genus are found both in Africa and Asia. Recent molecular work, however, has shown clearly that the African and Asian groups are not monophyletic, although the generic characters are the same. The pollen morphology of the two groups and many other morphological characters are also quite different. Which means that there needs to be some taxonomic revision and the African and Asian groups should be different genera. But strangely, if you look at the floral characteristics of the new species, you will see that it resembles the African group more than the Indian species. So I felt that it will be worthwhile doing some molecular work to see if our new species is more closely-related to the African or the Asian species. I roped in Siddharth, a post-doc. in Praveen Karanth’s lab, who has experience in plant molecular work. Luckily there were sequences available of both African and Asian Friesodielsia species available online. We used that along with sequences from our new species and built a tree. The new species clearly clustered with the Asian elements. We also obtained Scanning Electron Microscope (SEM) images of the pollen and found that here too, this new species was more similar to Asian ones.
H: You went back and got specimens of the plant?
N: Yes, I went back in November 2012 and got leaf and pollen samples from the exact same location. This whole process didn’t happen at one go, but gradually, over 2 years. I did it whenever I could find time off from my regular PhD work.
I also sent photos of the plant to Richard Saunders in The University of Hong Kong. Saunders’s lab focusses on phylogenetic studies of Annonaceae, especially on the southeast Asian species. One of his students, in fact, works on the Friesodielsia genus. We sent Dr. Saunders detailed morphological information and the photographs and asked him if it matched any of the southeast Asian species. He said it didn’t.
H: All the molecular work and SEM work was done in IISc?
N: Yes, in Praveen’s lab and in IISc’s SEM unit. Lakshminath Kundanati from the mechanical engineering department helped me with the microscopy. I was lucky that Siddharth was right here to help with the phylogeny. The molecular work was crucial to our paper because it clearly established that the new species was related to the Asian group. There was another incentive for doing it. If without doing the molecular work I had gone ahead and included it under Friesodielsia, and later it turned out that it was more related to the African group, then when the taxonomy is eventually revised, this species would have been renamed and I would have lost some of the credit for it. According to taxonomic convention, whenever someone writes a scientific name of a species, it has to be followed by the name(s) of the person who described it. But if the name is changed by someone, then that person’s name would be written there instead and mine would follow in parentheses or would be completely left out.
H: How did Shreekant (Shreekant Deodhar is a PhD student in Kavita Isvaran’s lab in CES) end up doing the illustrations for the paper?
N: I was looking for someone to do the illustrations, ideally someone near where I was to make it easy for me to supervise. I knew that Shreekant was a really good artist and that he would be interested since he hadn’t done scientific illustration before. I asked him and he said he would give it a try. It is all about getting the details right, from photos and specimens. I told Shreekant what details were important to capture – reticulation of leaf, leaf shape, position of flower, proportions – proportions are very important – texture as well. He took a few weeks, working in his free time, and he pretty much got it all right the first time.
H: When were you sure that it was a new species? What did you feel at that moment?
N: It didn’t happen suddenly. I started feeling more and more confident as I progressed. First encouraging sign was that it wasn’t in any of the southern floras, then when I identified the genus and it didn’t match with any species in India, and most importantly when Richard Saunders confirmed that it was a new species. So it is not sudden – the happiness built gradually.
H: The paper itself is quite technical and difficult to read. Can you tell us, in simple terms, what sets this species apart?
N: The almost-equal lengths of the inner and outer whorls of petals sets it apart from all other Asian species of this genus. We can forget about the African group now.
H: What sets this genus apart from other members of the Custard apple family?
N: All members of this genus are climbing shrubs – the technical term is scandent shrub. They can grow independently upto a certain height but beyond that they need support from other host plants. But with this new discovery, the generic characters need to be revised. Earlier, all members of this genus had unequal petals in inner and outer whorls, which is not the case for this new species. All members also had fruits that contained fruitlets which are two or more seeded. The new species’ fruitlets contain as many as five seeds. So the Friesodielsia genus needs to be redefined.
H: I am confused now. What characters make it belong to Friesodielsia then?
N: Scandent nature; underside of leaves are a dull milky-green or white; the peculiar arrangement of petals in two whorls of three each. I forgot to mention earlier – the inner petals of species of this genus are all joined together edge to edge forming a dome which encloses the reproductive structures. So these characteristics clearly make it a Friesodielsia.