A closed loop of ideas

This week, I was lucky enough to go to Lausanne, a small Swiss city on Lac Léman, to attend the MELiSSA Workshop. What is MELiSSA? As an ecologist, it is unlikely that you are acquainted with this European Space Agency (ESA) project, which stands for Micro-Ecological Life Support System Alternative. It was created in 1989 (read more on how it began here) and brings together European and Canadian partners from 13 different countries in an attempt to fulfill human needs in outer space via the development of life in closed systems. The main ideas include: recycling waste and carbon dioxide aboard spacecraft by using bacteria; and producing food, water, and oxygen in a regenerative way to keep costs low. Put in their words, it aims “at a total conversion of the organic wastes and CO2 to oxygen, water and food”.


Terrestrial lake eco-loop. Copyright: ESA.


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Harnessing the Tree of Life for conservation

I spent Monday in London at The Royal Society for a discussion meeting on Phylogeny, extinction risks and conservation.  As someone who is increasingly using comparative phylogenetic tools to ask how evolutionary history might influence conservation decisions, I took away at least three points (several more rattling in my mind at present):

(1) Measures of phylogenetic diversity are increasingly being used to inform conservation decisions (or at least that was the perception I got).

Perhaps the most notable way this is being done is through the EDGE (evolutionarily distinct globally endangered) programme.  EDGE classifies species based on the product of their IUCN Red List category and their evolutionary distinctiveness (ED).  ED is itself calculated by dividing the lengths of each branch in a phylogenetic tree by the number of species that subtend that branch.  These values are then summed for all the branches from which a species is descended.

(2) Risk of extinction is fairly clustered within evolutionary lineages – and this can lead to rather large losses in phylogenetic diversity (PD).  Losing PD may reduce ecosystem function and limit the range of biodiversity features that can respond to future change – if in fact there is an association between PD and function – though this is debatable.

This of course also assumes that closely-related species are more likely to go extinct because they share similar traits that make them more vulnerable to threats.  Large mammals are an excellent example of such a group.  But this might not be true for plants, particularly in areas with rapid diversification where species most classified as threatened are the recently-evolved ones that cluster within short branches at the tips of phylogenies.

(3)  Systematists are developing great new tools for assembling dated phylogenetic trees.

We heard about two specific resources.  The first was TimeTree, which is essentially a curated database collating all published estimates of divergence times among organisms.  By visiting the website, you can instantly search for a divergence time between any two species and find all published estimates, allowing you to not only get a date but also a statistical distribution for that estimate.  Unfortunately this means that its only as good as the primary literature and the curators’ ability to keep up with it.  I tried it quickly for two of our NZ alpine species (Ourisia macrocarpa and Veronica odora) but was told that “No molecular data available for this query”, which was surprising considering they do exist.

The second resource we heard about was the Open Tree of Life.  As the name says, it’s essentially trying to assemble a giant “tree of life” that will be continuously updated by the scientific community.  This is a really nice complement to TimeTree because rather than focusing on branch lengths, it’s just concerned with synthesizing tree topologies.  You can begin to explore the tree here.

Can plants get more carbon for less water?

This week’s group meeting featured a special joint production with Molecular Physiology to welcome Prof Graham Farquhar from the Australian National University.  Graham was in the UK to receive a Rank Prize Fund award for his contributions to food security by helping to guide the breeding of wheat varieties that use water more efficiently.

His talk, “Water user efficiency and water use effectiveness, a stomatal perspective using stable isotopes” was a far-reaching overview of his amazing research career, dating back to his time as a PhD student.  But he started his talk with a very provocative and timely consideration of global changes in rainfall and human population growth.

Rainfall is inherently random.  Sometimes there is too much, sometimes there is too little.  Australia is a country that experiences both these extremes.  For example, there are often heavy floods in the monsoon region while other areas, particularly where agriculture is concentrated in the southern part of the country, is drying up.  The desire to expand cultivated land inevitably means there is more pressure on more marginal rainfall.  An astounding statistic that Graham rolled off was that 1 ha of cultivated land was needed to feed 20 people.  20 people are added to the world’s population about every second!  Clearly, that’s a problem.

Graham’s talk then focused on how plants can use the least amount of water for a fixed amount of carbon.  He began by introducing his classic work on stomatal regulation of transpiration relative to carbon assimilation, which shows the two processes are fundamentally linked.  Changing evaporation will always change assimilation.  He then considered how plants could arrange the temporal expenditure of water to maximize assimilation of CO2.  Carbon isotopes are particularly useful here for discriminating among transpiration efficiencies associated with different genotypes and can help identify future crop varieties that use water more efficiently.  In dry conditions,  greater transpiration efficiency improves crop yield and selects for low C isotope discrimination in leaf dry mater.

As we ran out of time, we were left with questions about how the process of balancing carbon and water demands might be influenced by life history strategy (perennial versus annual) and competition for water in soil.

Slide of the week

Recently I read a nice blog post over on Dynamic Ecology discussing what different research groups choose to do with their weekly group meetings. Reassuringly (or is it worryingly?) most groups end up doing much the same thing, with the majority of time being spent either presenting new work or discussing papers. During our meeting, we tend to have a guest speaker that presents an overview of their research, somewhat like an informal seminar.  

This week, however, we followed Ed ’s suggestion and tried something a bit different: we called it “slide of the week”. The idea is simple: each person attending the meeting provides a single powerpoint slide and then spends no more than 5 minutes discussing it with the rest of the group. The aim is to bring together the positive features of the tried and tested groups meeting formats (e.g., presenting new work, new papers, discussing methods etc.) into a single session.  

Overall, I would say it was a success. People talked about a wide range of topics: we discussed the pitfalls of null model selection when inferring processes shaping community assembly in plants; we learned about the role of nutrient cycling in the litter as a mechanisms shaping coexistence between two dominant Iberian oak species; we talked about the role of sea grasses as a source of nutrients for coastal dune plant communities; and we explored the use of Thiessen polygons as a way of mapping land use and land ownership. Quite a lot for an hours work, in my opinion! What I especially liked was the fact that people brought different things to the table, ranging from problems they were having with their work, to preliminary results, statistical advice and recently published research. It also served as a good approach to get the discussion going, because everyone presented something and because we covered a wide range of topics which meant everyone had something to contribute.

I say everyone presented, but actually this isn’t true and this leads me to my one concern about the “slide of the week” format: it’s hard to stick to the allotted 5 minutes. We inevitably ended up spending more than 5 minutes on each slide (especially at the beginning, when everyone was getting into the discussion). As a result, not everyone got to present, which isn’t ideal. In the future we might need to be stricter about the time limit. I guess the only consolation is that at least we already have plenty more slides for future meetings!