Monthly Archives: December 2017

The holly, the mistletoe, and the pollinators: an update on an old story


Holly and mistletoe are two of Europe and Scandinavia’s most iconic plants, steeped in folklore and cultural significance, and redolent of the dark days of mid-winter and its festivities.  Last year, together with my colleagues Jim Rouquette and Tom Breeze, I published a study of the value that pollinators add to the wholesale auction prices of these two plants using data from the UK’s largest holly and mistletoe auction that has been held in the town of Tenbury Wells for 160 years.

Holly and mistletoe are excellent subjects for a study of the added value that pollinators bring to a crop as they are 100% reliant on pollination by a range of wild bees, flies and other insects.  This is because both species are dioecious with separate sex plants, therefore any berries produced on a female plant must be due to the activities of pollinators.

Here’s a link to last year’s blog post about that paper and here’s the reference for the paper itself, with a link to the journal where you can download it for free:

Ollerton, J., Rouquette, J.R. & Breeze, T.D. (2016) Insect pollinators boost the market price of culturally important crops: holly, mistletoe and the spirit of Christmas. Journal of Pollination Ecology 19: 93-97

The data set in that paper only developed the story up to 2015 as the 2016 auctions took place too late to include within our analyses.  However I’ve collected the auction reports for 2016 and 2017 and added them to the data set.  The results are graphed below*.

The auction price for holly with berries is rather volatile, but on average over this time period, berried holly has twice the commercial value of holly without berries.  Indeed in the last auction of 2017, holly without berries failed to sell, hence the value of £0.00.  The very wintry weather on the auction day reduced the number of buyers, but nonetheless, to have no one bidding for the unberried holly was unprecedented.

Holly auction prices plot

The pattern for mistletoe is rather similar, but in this case the value of berried material is less volatile than that of holly, and the average value is around three times greater than for auction lots of unberried plants.

Mistletoe auction plot

This data set offers a unique insight into the value of pollinators for two culturally important crops (all other such studies have focused on food or, rarely, fibre crops).  I’ll continue to archive the auction reports and to update these analyses every few years in the run up to Christmas.  If anyone is interested in accessing the data, please drop me a line.

If you want to learn more about the botany of different types of mistletoe follow this link to Mike Fay’s blog post on the Kew website.

Also worth checking out is Manu Saunders’ recent piece highlighting some old Christmas-themed blog posts.

Yesterday was my last day in the office, I’m now officially on leave and looking forward to a restful Christmas and New Year break.  Season’s greetings to all of my readers and thank you for your continued support and interest in biodiversity!



*There are three auctions each year and therefore three data points per annum, except for 2016 when only two auction reports were produced.



Filed under Biodiversity and culture, Ecosystem services, Pollination

Local and regional specialization in plant–pollinator networks: a new study just published

Euphorbia canariensis pollinators 2016-04-29 17 58 00

A fundamental feature of the natural world is that no species exists in isolation: all organisms interact with other organisms during their lives. These interactions take many forms and the outcome varies with the type of interactions. For example predator-prey interactions are clearly negative for the prey species, but positive for the predator. Other interactions result in positive outcomes for both species, including relationships between pollinators such as bees, birds and flies, and the flowers that they pollinate. An important feature of such interactions is how specialized or generalized it is; that is, how many different pollinators are actually involved in pollinating a particular type of flower, or how many types of flower does a specific pollinator visits.

In a newly published study, I have collaborated with colleagues from Denmark and Brazil to assess how local specialization (within a community) relates to regional specialization (across communities) using two separate data sets from the Brazilian rupestrian grasslands and Canary Island/North African succulent scrub vegetation.

Here’s the citation with a link to the paper (drop me a line if you can’t access it and need a PDF):

Carstensen, D.W., Trøjelsgaard, K., Ollerton, J. and Morellato, L.P.C. (2017) Local and regional specialization in plant–pollinator networks. Oikos (in press) doi:10.1111/oik.04436

The abstract is as follows:

“Specialization of species is often studied in ecology but its quantification and meaning is disputed. More recently, ecological network analysis has been widely used as a tool to quantify specialization, but here its true meaning is also debated. However, irrespective of the tool used, the geographic scale at which specialization is measured remains central. Consequently, we use data sets of plant–pollinator networks from Brazil and the Canary Islands to explore specialization at local and regional scales. We ask how local specialization of a species is related to its regional specialization, and whether or not species tend to interact with a non-random set of partners in local communities. Local and regional specialization were strongly correlated around the 1:1 line, indicating that species conserve their specialization levels across spatial scales. Furthermore, most plants and pollinators also showed link conservatism repeatedly across local communities, and thus seem to be constrained in their fundamental niche. However, some species are more constrained than others, indicating true specialists. We argue that several geographically separated populations should be evaluated in order to provide a robust evaluation of species specialization.”

This is what those two different habitats look like:

If you would like more information on plant-pollinator networks, including details of an edible game for Christmas (!), follow this link to the standingoutinmyfield blog.

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Filed under Bees, Biodiversity, Biogeography, Brazil, Macroecology, Mutualism, Pollination, Tenerife

Pollinators, flowers, natural selection and speciation: a virtual conference

Ashy Mining Bee 2017-06-17 10.55.45

It’s been a couple of years since I posted my previous “virtual conferences” on Pollinators, Pollination and Flowers and Ecology and Climate Change, a lapse that has largely been due to lack of time (my default excuse for most things these days….).  However Judith Trunschke at Uppsala University in Sweden has risen to the challenge of guest-curating her own virtual conference*.  The theme here is how pollinators impose (or sometimes don’t impose) natural selection on flowers that results in the formation of new plant species:

Timo van der Niet (IIASA 2010): Plant-diversification through pollinator shifts

Timo van der Niet (Congresos UCA 2014): Disentangling the contribution of pollinators in shaping angiosperm orchid genus Satyrium

Anne Royer (Evolution 2016): Plant-pollinator association doesn’t explain disruptive selection & reproductive isolation

Brandon Campitelli (Evolution 2016): Pollinator-mediated selection and quantitative genetics

Yuval Sapir (Evolution 2016): Rethinking flower evolution in irises: are pollinators the agents of selection?

Ruth Rivken (Evolution 2014): The mechanisms of frequency-dependent selection in gynodiocious Lobelia siphilitica

Gonzalo Bilbao (Botany 2017): Pollinator-mediated convergent shape evolution in tropical legumes

My grateful thanks to Judith for curating this great set of talks; if anyone else would like to do the same, please get in touch.

Feel free to discuss the talks in the comments section and to post links to other talks on the same topic.


*I’m assuming that, as all of these videos are in the public domain, none of the presenters or copyright owners objects to them being presented here.  If you do, please get in touch and I’ll remove it.


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Filed under Bees, Biodiversity, Birds, Butterflies, Evolution, Honey bees, Hoverflies, Mutualism, Pollination, Wasps