Monthly Archives: October 2018

The biological mutualisms at the heart of sourdough bread

20181026_120748

During the road trip to Denmark that I mentioned in a post back in September – see “There ain’t no b(ee) in Starbucks” – my wife Karin received a special gift from her sister Pia.  It was a small jar containing a starter culture for sourdough bread, a culture that Pia has been using since she received it from a friend, who long ago received it from another friend.  I didn’t know much about sourdough bread and did some reading. That Wikipedia link is a good introduction but don’t be put off by the complexities of “refreshment” – we’ve kept the starter culture in the fridge since early September and it’s been fine.  Karin used the culture for the first time this morning and made the rye bread you see above.

But on to the biology.  In essence the sourdough culture is a mix of wild lactic acid bacteria and wild yeasts, plus flour and water.  When added to the bread mix (which in our case contained water, salt, seeds and molasses, as well as rye flour) the yeasts feed on some of the sugars within the mix and the lactic acid bacteria feed on other sugars that the yeast cannot metabolise.  During that bacterial fermentation, byproducts are also produced on which the yeasts feed.  The yeasts in turn produce carbon dioxide which serves to leaven the dough, and the bacteria produce lactic acid as another byproduct, which gives the bread its slightly sour flavour.  This lactic acid also lowers the pH of the environment and, together with the production of anti-fungal chemicals, the lactic acid bacteria prevent the growth of other bacteria and moulds.  The yeasts, however, can tolerate these conditions and they thrive.

At least six species of yeast and 25 species of lactic acid bacteria have been shown to be  involved in this process, often as multi-species mixtures.  The exact biodiversity of the culture is dependent upon its source: micro-organisms vary a lot across the world.  But the heart of the relationship between yeasts and bacteria is always the same: they each facilitate the growth and reproduction of the other, and so the relationship is mutualistic, much like (most) relationships between plants and pollinators, birds and berries, and sea anemones and clownfish.

Of course there is a third organism involved in this mutualism: Homo sapiens.  By producing the resources on which these organisms feed, and then distributing the starter culture, we are providing the right conditions for the yeast and lactic acid bacteria to increase their populations.  In turn the yeast and bacteria play an important role in producing food for us, and in fact this way of making bread is thousands of years old.  Microorganisms and people all benefit: what could be more mutualistic than that?  Indeed, these interactions could be classified as a rare example of a ménage à trois mutualism.

There’s also a social-cultural dimension to all of this as the passing of gifts such as the starter culture binds friendships.  If any of our local friends are reading we’d be happy to share the sourdough culture once we’ve bulked it up.  The bread that it makes is delicious and from now on we’re going to try to give up buying the shop-bought kind.

If you want to read more about all of this, and have a try at making your own starter culture from scratch, there’s some great information and links on the Microbial Menagerie blog.

Many thanks to Pia for sharing the starter culture, and to Karin for baking the bread!

5 Comments

Filed under Biodiversity, Biodiversity and culture, Mutualism

Seven things that I learned at the SCAPE 2018 meeting in Ireland

SCAPE 2018 group photo

The 32nd meeting of the Scandinavian Association for Pollination Ecology took place last week, and from Thursday through to Sunday 87 researchers from around the world met to discuss their latest findings.  For the first time the conference was held outside of Scandinavia, at Avon Rí, Blessington in Ireland.  As always it was a friendly and stimulating meeting, and a great opportunity to catch up with old friends and colleagues, and make new ones.

Here’s a link to the full programme with the abstracts.  I gave a talk about our recent work on the evolution of pollination systems in the plant family Apocynaceae which seemed to go down well enough and generated some discussion later in the bar and over breakfast.  The quality of the research and the standard of the presentations was very high and I don’t intend to single out individuals, but I did learn some things during the meeting that I wanted to highlight:

  • Some bird pollinated penstemons produce scent volatiles, even if we can’t detect them (Amy Parachnowitsch, University of New Brunswick).  Relates to this post of mine from earlier in the year on how hummingbirds have a sense of smell.
  • Staying with the theme of dispelling bird pollination myths – many of the supposedly sunbird-pollinated species of Aloe in southern Africa are in fact pollinated by non-specialist passerines such as bulbuls (Steve Johnson, University of KwaZulu-Natal).
  • There’s a data set on plant-pollinator interactions from the far north of Finland from the end of the 19th century and this area is being re-surveyed to assess changes between then and now (Leana Zoller, Martin Luther University Halle-Wittenberg).
  • Farmers who grow watermelons in Tanzania can improve their yields by encouraging more pollinators in their fields; the yields are better than adding fertliser or irrigating the crop (Thomas Sawe, Norwegian University of Life Sciences).
  • A weevil was introduced into Indonesia in the 1980s to improve yields of oil palm by increasing the rate of pollination (Lynn Jørgensen, University of Oslo).
  • There’s strong evidence that the current distributions of plants with specialised pollination systems in southern Africa are constrained by the environmental niche, and thus the distribution, of their pollinators (Karl Duffy, University of Naples).
  • Mobile saunas are a thing!  I took a photo of one (below) just to prove it.  Thanks to Dara Stanley and Jane Stout for organising that, and the rest of this brilliant conference!  Hope to see you all next year in Lund.

There was a lot more tweeting going on at SCAPE this year and you can see comments and images by searching Twitter for #SCAPE2018

If you attended SCAPE, what did you learn?  What surprised or interested you?  Please comment below.

SCAPE 2018 sauna

2 Comments

Filed under Biodiversity, Pollination

Pollinator availability, mating system and variation in flower morphology in a tropical savanna tree – a new, open-access study

Curatella image by Pedro Lorenzo

Widespread plant species can encounter a variety of different pollinators across their distributional range.  This in turn can result in local adaptation of flowers to particular pollinators, or to an absence of pollinators that results in adaptations for more self pollination.   A newly published study by one of my former PhD students, André Rodrigo Rech in Brazil, has looked at this in the widespread South American savanna tree Curatella americana.  André studied 10 populations separated in space by thousands of kilometres, in cerrado vegetation, one of the most threatened habitat types in Brazil.  Here’s the abstract:

Widely distributed organisms face different ecological scenarios throughout their range, which can potentially lead to micro-evolutionary differentiation at specific localities. Mating systems of animal pollinated plants are supposed to evolve in response to the availability of local pollinators, with consequent changes in flower morphology. We tested the relationship among pollination , mating system, and flower morphology over a large spatial scale in Brazilian savannas using the tree Curatella americana (Dilleniaceae). We compared fruit set with and without pollinators in the field, and analyzed pollen tube growth from self- and cross-pollinated flowers in different populations. Populations with higher natural fruit set also had lower fruit set in bagged flowers, suggesting stronger barriers to self-fertilization. Furthermore, higher levels of autogamy in field experiments were associated with more pollen tubes reaching ovules in self-pollinated flowers. Morphometric studies of floral and leaf traits indicate closer-set reproductive organs, larger stigmas and smaller anthers in populations with more autogamy. We show that the spatial variation in mating system, flower morphology and pollination previously described for herbs also applies to long-lived, perennial tropical trees, thus reemphasizing that mating systems are a population-based attribute that vary according to the ecological scenario where the plants occur

Here’s the full citation with a link to the paper which is open access:

Rech, A.R., Ré Jorge, L., Ollerton, J. & Sazima, M. (2018) Pollinator availability, mating system and variation in flower morphology in a tropical savannah tree. Acta Botanica Brasilica (in press)

The illustration of Curatella americana  and its pollinators is by Pedro Lorenzo.

This paper is a contribution to a special issue of Acta Botanica Brasilica dedicated to floral biology and pollination biology in Brazil It’s all open access and if you follow that link you can download the papers.

1 Comment

Filed under Bees, Biodiversity, Biogeography, Brazil, Evolution, Pollination

Is there really a “battle for the soul of biodiversity” going on at IPBES? UPDATED x 3

Carved demon

No.  But perhaps I should give some context to both question and answer…

The Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) describes itself as “the intergovernmental body which assesses the state of biodiversity and of the ecosystem services it provides to society, in response to requests from decision makers”.   Sounds a little dry, I agree, but in fact IPBES is the most exciting and innovative international environmental body to have emerged in recent years.  Exciting because its remit is specifically to assess how society is affecting global biodiversity in toto, but also its value to humans.  Innovative because it’s a broad church that is trying to bring together the knowledge and expertise of both natural and social scientists, practitioners, indigenous peoples, and stakeholders of all kinds. This broad approach is something which some other international bodies have not, traditionally, been so keen to adopt.

IPBES has its critics who see it as superfluous in that its mission overlaps too much with that of organisations such as the Convention on Biological Diversity, the Ecosystem Services Partnership, and the United Nations Environment Programme.  However I certainly think that there’s room for such an organisation.  We need as many voices as possible shouting about how important these issues are, at all levels of society, from the work of local conservation volunteers and the People’s Walk for Wildlife upwards to the highest levels of international governance.  So I’m a supporter of what IPBES is trying to do; perhaps I’m biased but I was especially impressed by the fact that the first major output of IPBES was a badly needed Assessment Report on Pollinators, Pollination and Food Production for which I acted as an expert peer reviewer over its two iterations.  I’ve written posts about this a couple of times – see for example this one.

In recent weeks, however, there’s been some reports of in-fighting within IPBES, and between IPBES and other organisations, that science journalists have seen as being a major war of ideas.  It culminated in Nature publishing a piece entitled “The battle for the soul of biodiversity“, backed up by an editorial suggesting that “the global body for biodiversity science and policy must heal rifts“.

The crux of the perceived disagreements centre on terminology and concepts as much as anything, and specifically the notion of ‘ecosystem services’ versus ‘nature’s contributions to people”.  These seem to me to be saying much the same thing using different words, and I have to say that I was shocked when I read those articles and wondered what the hell was going on: was IPBES really falling apart before it had even managed to firmly establish itself (remember it only launched in 2013)?  Or was this just journalistic hyperbole of the kind that serves no real purpose other than to increase sales and page views?

I have no inside track to IPBES’s workings so I kept an eye on developments.  I was delighted, therefore, to see the 19th September issue of Nature publish four letters from IPBES insiders and experts from other organisations.  All of these, plus the articles I linked to above, are open access.

The first letter is from Jasper Montana of Sheffield University pointing out that “ideas need time to mature” and that “debates are grist to the mill of innovation for environmental governance”.  In other words, IPBES is a young organisation and the sorts of terminology being used are far from mature: terms such as “ecosystem services” and “natural capital” are at most a few decades old.  Clearly there is an urgency in building governance systems that can effectively conserve biodiversity, but debates around the best terms to use will not hinder that process.

The second letter from Bernardo Strassburg in Brazil entitled “honour guidelines that reconcile world views” pointed out that IPBES’s own guide to such concepts notes that the ecosystem services approach is just one of several, all perfectly valid, ways of viewing the relationships between people and nature, and of seeing people as part of nature.

The next letter is from IPBES chair Sir Bob Watson assuring us that “squabbles don’t obscure the bigger picture” and that a diversity of opinions and ideas is one of IPBES’s strengths.  It’s worth noting here that the original model for IPBES was the IPCC (Intergovernmental Panel on Climate Change) which has in the past been criticised for not allowing a diversity of opinions among contributors to its reports.  You can’t please all the people all of the time, and clearly not Nature journalists….

Finally Rudolf de Groot, chair of the Ecosystem Services Partnership, plus colleagues Pavan Sukhdev & Mark Gough, argued that “sparring makes us strong” and write the most critical of the four letters, stating that they “strongly object to the tone and content” of the original article.  They assure us that the Ecosystem Services Partnership and IPBES are not in competition and that there is mutual respect for different opinions and concepts.  Furthermore “both organizations…stand united against biodiversity loss and ecosystem degradation…. Irrespective of the terminology used, our community is undivided in our knowledge that we fundamentally depend on nature in countless ways.”

So there you have it.  The Nature article and editorial were, in my opinion and those of the letter writers, over the top, exaggerating debates and disagreements that, whilst certainly real, do not endanger IPBES nor its mission.  I urge you to read the original articles then the letters, and make up your own mind.  Comments welcome as always.

UPDATE 1:  Just after I tweeted this post the Natural Capital Coalition added it to the bottom of a tweet thread that they had started when the original articles were published.  I confess that I missed these first time round but the thread adds extra detail to why the articles were misleading.  Well worth reading – here’s the start of the thread:

 

UPDATE 2:  It seems Nature is happy to continue the exchange of views following the article; the current issue of the journal contains another letter (once again open access), this time from Jim Harris (Cranfield University) and Janne S. Kotiah (University of Jyväskylä, Finland) pointing out that “the debate around which framework to use to value biodiversity could stem from the relatively recent coining and adoption of the concept of nature’s contribution to people (NCP).  Google Scholar returns only 19 hits for NCP and nearly 100,000 for ecosystem services, mainly because the latter has been in use for much longer“.

They go on to say (as all the correspondents on this article have) that they see no reason why the two worldviews of NCP and ecosystem services are irreconcilable. NCP seems new and different because it’s unfamiliar jargon   All of this reminded me of one of my first posts on this blog – “Business and biodiversity: oil and water?” which documented an event that I attended in London called “Biodiversity & ecosystem services: new collaboration opportunities for academics with businesses” .  It’s worth quoting what I said with regard to jargon within the field:

“In the workshop I attended there was some discussion as to whether technical language such as “biodiversity”, “natural capital” and “ecosystem services” (which one contributor referred to as “eco-babble”) deters senior business managers from engaging with nature conservation. I pointed out that words and phrases such as “email”, “internet” and “world wide web” were not so very long ago similarly considered to be technical jargon but are now part of our every day language.”

I still stand by this: technical language is only a barrier to engagement if people do not take the time to understand the jargon.  And jargon can become everyday language very swiftly.

UPDATE 3: This issue rolls on and Nature is still allowing commentary.  Just before Christmas Jonathan Davies and Peter Stoett wrote on behalf of the authors of the biodiversity section of the newest Global Environment Outlook (GEO-6) from UNEP  (due March 2019) that “Biodiversity loss is dire, don’t get distracted“.

 

17 Comments

Filed under Biodiversity, Ecosystem services, IPBES, Pollination