evolution

Rewinding the Tape of Life

Journal of Ecology Blog

If evolution happened anew, what would the present-day plant world look like?  That is, would the randomized processes that govern evolutionary change tell a different story? And particularly for plants which are sessile organisms, is the starting point of ‘who gets there first’ the most important of all?

Priority effects – the order and timing of species arrival into local communities – can affect ecological community structure and functioning, with profound effects for species persistence and ecological interactions (Chase et al., 2000; van de Voorde et al., 2011). As such, the arrival of different species at different times can dramatically alter the evolutionary tapestry of any given system on ecological time frames, but also in evolutionary time. In particular, the diversification of early arriving species can pre-empt available niche space to prevent the establishment, dominance or diversification of species that arrive later on down the road.

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A closed loop of ideas

Notes:
1) Throughout this text, I will use the word “terrestrial” to refer to the planet Earth as opposed to “space”, which slightly pains my aquatic biologist heart.
2) As a lot of the talks had some link with plant sciences, I feel like, despite this entry being space or lake focused, it also has a place on this green and leafy blog!

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”.

Melissa_lake

Terrestrial lake eco-loop. Copyright: ESA.

 

What drew me to this workshop is that this closed loop is based on lake ecosystems, as depicted in the diagram above. Whether lake ecosystems are truly closed is debatable, and in my opinion is rather incorrect (I still believe in the importance of allochthony!). However, in the natural terrestrial environment, lakes are probably the system that comes nearest to the idea of a closed loop, due to their ecological isolation and the limitation of external inputs. In lakes, the processing of waste products via plant and algal metabolic activity fuels the regeneration of food, clean air, and pure water – and this is why the lake aquatic ecosystem is used as a model for MELiSSA.

Concretely, they try to reproduce this via the following compartmentalization of tasks:

I Organic waste degradation & solubilisation by thermophilic anoxygenic bacteria
II Carbon compounds removal by photoheterotrophic bacteria
III Nitrification by nitrifying bacteria
IV a Food and oxygen production by photosynthetic bacteria
IV b Food, oxygen and water production by higher plants
V The crew

 

Which recreates the loop:

MELiSSA_loop_diagram

The 5 compartments of the MELiSSA loop. Copyright: ESA. See Godia et al. (2002).

 

The two-day workshop brought together 140 participants from 21 countries, from academia and industry, who discussed solutions to issues associated with space travel. With more than 40 speakers, you can imagine the days were long, but invigorating, and made even more enjoyable by the quality of the tea breaks and meals (a giant parmesan filled with rice for lunch!). To give you an idea of the breadth of topics discussed, here are the titles of the 6 sessions that made up the workshop: 1) Waste processing, 2) Water recycling, 3) Air recycling, 4) Food production & preparation, 5) Chemical & microbial safety and 6) System tools. These covered subjects as seemingly divergent as food production and new food sources, clean showerheads, anaerobic digestion, human feces disposal, and hydroponic plant-fish interactions.

My thoughts about space research have always been that the money put into it could instead be used to solve terrestrial problems. Scientific terrestrial problems – feeding the world, conserving biodiversity, predicting the effects of global change – urgently need solutions. As an aquatic biologist, I have heard many times that the deep sea has been infinitely less explored than the surface of the moon. Why should we keep investing into space research then? Is sending men to the Moon or to Mars a sci-fi dream, a demonstration of our technological power, or a serious and, perhaps in the future, necessary escape from a damaged planet Earth? Whichever of these it may be, I have come to understand that spending money on what may first sound utopic is actually beneficial to our planet in much more concrete and terrestrially applicable ways than I ever imagined. What the conference taught me is that there’s a kind of closed loop of ideas: space research takes from ecology, and vice versa.

And indeed, there is no doubt that the vast majority of the research and new technologies discussed throughout the workshop aims to bring more sustainable innovations or alternatives to extant ones. Ultimately, the idea of the closed loop is about recycling: anything that is part of the loop needs to be reused, recycled, and regenerated. By incorporating this ecological idea into technological principles, the closed loop can also yield a new form of economy, a “circular economy”, whereby waste is limited and the value of products is retained. Of course, I am skeptical about some of the proposed projects – too utopic, not financially viable, no real advances made. For instance, I would love to dive in underwater gardens (large glass tanks maintained at supposedly constant temperature), but I don’t understand how they could ever be part of the solution to feed the world.

In addition to this little inner discussion I had with myself, what I can really take home from this meeting is a lot of new knowledge on microbial communities – how they interact among themselves but also with their environment, how they process nutrients, and how they can be studied. One question that particularly triggered my interest is whether prosperous and diverse microbial communities that can auto-regulate are less harmful, or risk-prone, than disinfected zones whereby resistant microbes have the potential to thrive and be pathogenic? I also saw how my current research could be applied in various ways. As a PhD student, not getting results can sometimes distract you from the focus of your project, and leave you wondering why you are there and for what purpose. Seeing the potential – both theoretical and applied – of my research, gave me a surge of motivation and new ideas. It also pushed me to think of subjects that had never even crossed my mind, namely the number of issues associated with space travel – microbial contamination, food and water supply, waste removal, breathing clean air…

Finally, I would like to say that my most valued moments of the workshop were occasions to exchange ideas with Mark Nelson. Mark was part of the first Biosphere 2 mission from 1991 to 1993 (if you don’t know about this 2-year closed loop experiment, in Arizona, with 8 crew members, I recommend reading about it) and is one of the founders of the Institute of Ecotechnics. I have to admit I was a little nervous about attending the workshop, fearing that I would feel out of place amongst all these engineers and businessmen. In the first few minutes upon my arrival though, I met Mark and felt like I was in the right place, and that I could learn a lot from this workshop. Mark is an ecologist – the academic son of H.T. Odum, and the academic grandson of G.E. Hutchinson – and has been involved with MELiSSA for many years. It was truly engaging to discuss space exploration, closed systems, systems ecology, urbanization and many other exciting or demoralizing topics. Special encounters like these can give large events a whole other dimension.

In the end, I came to the conclusion that environmental thinking can successfully be integrated into space activities, and can promote synergies between space and terrestrial research. I am glad I attended this workshop, which gave me space for thought as well as a taste of something new. And to open up the discussion: how do you feel about closing the loop?

IMAGE_MAIN

Copyright: ESA.

 

 

Explaining the origins of species diversity

The July 2015 issue of New Phytologist has come out and its a doozy!  The entire issue features work on evolutionary plant radiations, drawing together a range of papers that summarize the current state of knowledge about “where, when, why, and how” plant radiations happened.  An editorial by Colin Hughes, Reto Nyffeler Peter Linder outlines the content of what will surely be a landmark issue for years to come!

Many, if not all, of these papers were presented at a symposium organized in Zurich that we attended with our New Zealand collaborators Professors Bill and Daphne Lee in June 2014:

We're somewhere in the crowd

We’re somewhere in the crowd …

For me, this was possibly one of the most intellectually stimulating meetings that I’ve ever attended.  Talks drew major figures in plant ecology, evolution, and systematics and really pushed the boundaries out on ‘diversification’ research.  The field itself is still arguably quite new, with many of the key questions synthesized in a 2008 paper by Peter Linder.  In fact, we have a PhD studentship available to follow-up some of these questions and build on what we talked about at the meeting.

You might have noticed that we even have a contribution in the New Phytologist Special Issue.  Our paper tests the mechanisms by which plant evolutionary radiations emerge and influence ecological dynamics.  We apply more of our expertise in structural equation modelling to focus on 16 species-rich genera in the alpine zone of New Zealand.

Diversity in New Zealand’s alpine.  Celmisia, Chionochloa, Dracophyllum, and Veronica all appear in this photo.

One of the most exciting aspects of our paper is that we’ve tried to reconstruct the niche space that each genus has occupied over the last 20 million years.  This is fairly ambitious and has involved tasks like reconstructing sea surface temperatures through the Cenozoic from isotopic measurements of foraminifera deposited in marine sediment cores, and then using these to estimate past land temperatures.  We’ve also had to consider that the alpine zone has grown immensely over time with uplift of the Southern Alps.  To do so, we collated radiometric dates of rocks and tried to infer their rate of uplift since the Miocene.

Overall, our results suggest that genera that colonized New Zealand earlier encountered more ‘vacant’ environmental space, which promoted species diversification and further occupancy of the environment.  Genera that occupied more environmental space were subsequently more dominant in present-day vegetation plots.  The key message is that time not only explains why diversity arises, but how this diversity influences ecological dynamics.  The Special Issue has many other fabulous papers, so do check it out!

Drooling over plants (literally!)

It is really nice to be able to write about our latest paper, which just came out in Biology Letters to a fair bit of fanfare.  It got picked up by Science, New Scientist – including in their 23 July print issue – and even the Royal Society had a piece about it.  BBC Radio recently had me out to talk to them:

 

Why so much attention?  Well the paper is one of those quirky but interesting scientific discoveries.  And it is based on drool.  Yup, you read that right, the saliva of large mammals.

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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.