Thanks to funding from the Bentham Moxon Trust and the Guilin Botanical Garden, myself and colleagues explored five caves for plants in October of this year (2014). There are likely thousands of caves in the limestone karsts of south-east asia which contain plants. Whilst of great interest botanically and for conservation they are also beautiful in their own right and each cave is unique. I thought I would provide a portrait of each one to show how varied they are in their form, where plants grow in them and their size.
The cave above was one of the few that we spotted from the road and then were able to get to. It is also one of the few that had little evidence of human disturbance, very few footprints and areas of pure white travertine that had fallen from the roof had not been walked on or collected. The main plant-bearing cavern of the cave was about 25 m deep and the roof 15 m high and it had a well developed flora, you can see plants from the african-violet family (Gesneriaceae) in the foreground and we collected five species of nettle here.
Xiangshuidong Tian Keng cave in Guizhou was one of the largest caves that we have collected in, but also one of the most impacted by tourism and use by local communities. The main cavern is about 250 m deep with a roof between 45 and 30 m high and it is set within a huge cliff forming the side of a mountain. It also has a waterfall and river running across the back of it. It is in this cave that we found a very rare and unusual form of Elatostema oblongifolium that has its male flowers borne on specialised shoots but overall the plant diversity of the cave was quite low, presumably because of the large numbers of local tourists and associated trampling of much of the ground available for plants
This was the first cave that we encountered on this field trip. We found it after first being taken to a hole in the ground as what must have been a mistranslation from Mandarin into the local dialect. The cave was relatively big and had a trail running inside. The main cavern shelves very steeply meaning that very little light penetrates into the cave. Despite this and the relatively high altitude, 1500 m, we collected seven species of nettle from here.
This cave should have been perfect as it shelved gently meaning that light penetrated quite deep, it also had plenty of places for plants to grow, such as boulders and rocks. We only collected four species of nettle here, probably because the cave was heavily impacted by farmers using it as a barn to keep their water buffalo in at night. Evidenced by lots of hoof prints and dung. This is a very common use of caves and the trampling of buffalo and their herders can have a significant impact on the plants in the caves (see below).
Nettles have unisexual flowers, that is each flower functions only as a male or a female. Counter-intuitively though the flowers still retain the non-functional and often much-reduced organs of the non-functional sex. These are called pistillodes in the case of the rudimentary female organs in male flowers and staminodes in the case of the rudimentary male organs in female flowers. Inpart of the nettle family the staminodes are put to good use: ejecting the seed from the fruit.
This can be best understood by considering that nettles have male flowers which open explosively, pollen being released in tiny clouds (they are also very small). In fact one species, Pilea microphylla, is commonly known as the artillery plant for this reason. The mechanism for the explosive opening of the male flower is that the stalks (filaments) of the pollen sacks (anthers) are folded in on themselves in bud. As they develop these stalks fill with water until they are all pressing against each other within the flower bud and ready to burst. At a certain point the pressure becomes too great for the thin petals of the flower bud and they rip leading to the stalks being able to straighten explosively. This has happens incredibly quickly and although it has not been recorded for nettles, in the closely related mulberry where this also happens, the flower can open in 25 millionths of a second, moving petals to velocities in excess of half the speed of sound.
In one group of nettles which includes seven genera this explosive ability of the pollen sacks has been harnessed to release the seed from the fruit. Below you can see a close-up of the fruit of Pilea japonica showing the staminodes flexed and ready to eject the seeds (dark coloured).
I have just returned from collecting nettles in South West China with my great friend and colleague Professor Wei Yi-Gang and researcher Fu Long-Fei from the Guilin Botanic Gardens. For several years we have been working on documenting the nettle diversity of the limestone karst of this region, focusing on the poorly known cave-associated floras. Karst is a form of limestone which has been weathered by rain for millions of years resulting in finely divided and sharp surfaces and very steeply sided hills, small mountains and gorges. The karst where we have been working form part of a formation which runs from Myanmar, northern Thailand and Vietnam and across into southern China and includes the famous ‘stone forests’ of Yunnan and Guangxi. I am interested in karst because it is where nettles are most diverse, both in terms of genera (species groupings) and species. At a single location it may be possible to encounter eight genera and over a dozen species!
Because the limestone is porous it has resulted in the formation of thousands of caves whose entrances have been colonized by plants from a small group of families: nettles (Urticaceae), african violet family (Gesneriaceae), Begonias (Begoniaceae), ivy family (Araliaceae), the coffee family (Rubiaceae) together with ferns and mosses. The most diverse of these are the nettles, one group of which, Elatostema has about 1/5 of the species from this region known only from caves. As well as having very low light levels, sometimes 1/10 of 1% daylight, the caves have constant humidity and low temperatures which contrast strongly with the cave exterior. The cool air of a cave can be felt up to 20 m from the entrance, often before the cave itself can be seen. We believe that the species associated with caves have likely come from the deep shade of the forests that once dominated this area but which have since been lost to agriculture. It also possible that some of the species are relicts of a previous, cooler climate during the last ice-age. This is something that we have begun to study.
Caves represent a last refuge for several hundred species in SW China and now is a time of great change as caves come under threat from tourism, agriculture, urbanization and cement production. We want to help conserve these caves and the species that they include by first documenting their diversity and distribution across SW China. This information can be disseminated within China in the hope of raising awareness and protecting individual caves. It could also be used to identify a network of protected caves which include all of these species. Professor Wei would also like to develop protocols for cultivating the species outside of caves, something that is very difficult to achieve at the moment and which could represent a vital step for their conservation.
Since 2007 I have been working with colleagues at the Chinese Academy of Sciences Guilin Institute of Botany on documenting the unusual cave flora of SW China and Guangxi. My interest stems from the fact that one of the most common groups of plants in these caves are two particular groups of nettles, members of the succulent herbaceous genera Elatostema and Pilea. It is also heavily influenced by the presence of a very knowledgeable and dedicated botanist at the Guilin Institute of Botany, Professor Wei Yi-Gang.
More recently I have wanted to see whether it is possible to explain how, and when these plants occupied these ancient caves. Possible explanations are that they evolved in the caves, some of which are 15-25 million years old; alternatively that they represent plants which grew outside of the caves when the climate was different, during the last ice-age for example; lastly that they are relics of plants which grew in the forest understory outside of the caves prior to the arrival of agriculture in the area maybe 1,500 years ago. To try and answer these questions I have, together with a Masters student Alfred Gay, used DNA extracted from the leaves of the plants to look for patterns which may point to one of the three possible explanations above. Click here to see a slide show of the preliminary results.
Another interesting line of research would be how these nettles survive in such low light levels. In some cases 1/50th of 1% daylight! For the moment though I am focussing on documenting their diversity and describing the new species we find but in the long-term I am hoping to find collaborators to explore these other areas of research.
All large Museums and herbaria have backlogs of specimens that are waiting to be processed and incorporated into the collections, sometimes for a century or more. Whilst to many institutions, specimen backlogs can seem like an eternal cloud pulling at their consciences, the reality is that they are an inevitable consequence of uneven collecting effort, bequests, absent-minded scientists and the amount of money available to maintain natural history collections. It might be better to think of these collections in limbo as potential treasure troves for those who finally do get the time and resources to process them. Last week I went to meet Natural History Museum (NHM) curator Holger Thüs, herbarium technician John Hunnex and their volunteer team in the backlog processing area of the Botanical Collections.
Thanks to the efforts of Holger and his team at the NHM, over 2,300 boxes of lichen backlog have been processed in the last three years. During their efforts some important and hitherto unknown historical collections have been recovered which include specimens collected by Charles Darwin from Tierra del Fuego, David Nelson collections from Captain Cook’s third voyage and Francis Masson collections from South Africa, as well as many others. Maybe less glamorous though, but of great scientific value however are the big collections of 19th and early 20thC lichens from the UK as these provide an important snap shots that help document the impact of industrialisation on air quality and the landscape as it began and later as it gained momentum. These collections plug gaps in our knowledge thereby making the UK biota one of the most completely known.
Of particular value was the discovery of what is likely William Mudd’s personal lichen collection from the middle of the 18thC and which contains specimens which formed the basis of the first UK lichen flora published in 1861, ‘A manual of British Lichens‘. The 52 book-like fascicles of unbound sheets and hundreds of specimens were rediscovered dispersed between cupboards in the Cryptogammic Herbarium and in stores at the top of the Museum’s towers where they were thought to represent spare / duplicate material for distribution. The fact that such a treasure was found in the backlog hints at what other amazing collections could be found in the coming years as the work to process it continues.
As well as promoting sustainable alternatives to slash-and-burn our Darwin Initiative Forest Futures project also seeks to raise awareness of the value of natural forest and alternatives to its unsustainable use. With this aim Juan Fernando Reyes and Rolman Velarde from Herencia ran a two-part course for 60 students and lecturers from the Environmental Engineering programme of the Amazonian University of the Pando (UAP). The first part of the course took place at UAP and provided an overview of the ecosystem services that the Amazon provides to the Pando but also at a regional and global level.
The second part of the course took part at one of our partner communities, Palacio. This consisted of demonstrating sustainable agricultural practices: aquaculture and the restoration of soils to productivity using Inga agroforestry. The students were also able to visit our monitoring plot where together with partners from the Museo Noel Kempf we are evaluating the biodiversity and carbon sequestration of the Pando’s forests.
I have been very lucky to present some of the work that Tonya Lander at Oxford University and I have been working on at the UNESCO ‘Botanists of the 21st C’ Conference in Paris. The work builds on a project whose aim was to provide scientific tools for the sustainable harvesting of the underutilized crop and tropical forest tree, Brosimum alicastrum that Tonya and myself undertook in association with the Maya Nut Institute and which was funded by the Darwin Initiative. Tonya and colleagues at Exeter and Oxford University developed a clever way of using investment risk data to help prioritise conservation actions. The basis of this was to use investment risk ratings as a surrogate for the risk of a conservation action failing because of corruption, lack of government infrastructure or capacity
On the 13th of September I had the pleasure of working with the Naked Scientists, a media-savvy group of physicians and researchers from Cambridge University who use radio, live lectures, and the Internet to strip science down to its bare essentials, and promote it to the general public. I also had the pleasure of meeting Liz Booker, a coffee taster from Starbucks. The interview was about coffee and the chemistry and the genetics behind its flavour and was in response to scientists having now sequenced the genetic code of one of the the coffee species used to make coffee. I am no expert on coffee but served as botanist for the piece. After the event I took Liz Booker and Starbucks Press Officer Nicky Gaskell to visit our coffee collections in the Herbarium where we looked at a number of 18thC specimens. The peice was broadcast on BBC Cambridgeshire, BBC 5 Live and Australian ABC, click here to hear the interview and read the transcript
We have established Inga agroforest plots on abandoned slash-and-burn sites, degraded pasture and land used for road grading where the topsoil is removed with a bulldozer. After six months seedlings have established on all of these sites but with slower growth and some mortality on the bull-dozed and pasture sites. We planted out our plot at Motacusal, an abandoned slash-and-burn site at the end of February and since then the seedlings here have done very well, most over 1.5 m in height. At this site we have 1,200 plants growing and they may well ‘capture’ the site a year after planting in six months time. By capture we mean that they dominate the weeds and other competing vegetation and control the site. Now that the dry season has ended and the seedlings have become saplings we are well on the way to delivering our first agroforest.
On my recent trip collecting nettles in the Dominican Republic we came across what is very likely a new species of Pilea, a group of about succulent nettles. I thought it might be useful to outline what happens from collecting / discovering something new to it being published as a new species, from my own botanical perspective of course. In the case of this species, it has a couple of distinctive features which make it stand out from similar looking Pilea species: 1) a well developed above-ground tuber, up to the size of a small potato, and 2) relatively large male flower clusters for the group of species it is in. This gives me two diagnostic characters to check with in existing collections and in the literature. Pilea is a genus of over 700 species found in tropical and subtropical Asia, Madagascar, Africa and the Americas. All but a few species are restricted to one of these areas or a much smaller area and this knowledge enables me to delimit my search area. In this case, the Greater Antilles (Cuba, Jamaica, the Cayman Islands and Hispaniola).
My second job is to see if the species has already been described. To do this I need to look through the collections of the most appropriate herbaria for this area, starting with the National Herbarium of the Dominican Republic. This can take quite a long time although many collections have been digitised and are available online. I then need to follow this up by reviewing the literature for the region to see if I find any descriptions which match or are close. Once I have done this I should have a list of species that are possible or close matches. These I can then compare in more detail with my possible new species and confirm whether it is new or not. This I will do by looking at the type specimens under a microscope and comparing their key features: leaf and stem shape, the nature of their hairs, the size and shape of the flowers and of course in this case, the presence or not of a tuber. This also provides me with the information I need to write the diagnosis of the new species. Once I am sure that this is a new species I can start writing the description and think of a name. A new species description will include a detailed description of the plant, a line drawing illustrating the diagnostic features and a species conservation assessment which will provide an indication as to how threatened with extinction it is.
Alex Monro's blog about the documenting and conservation of biodiversity