Monthly Archives: April 2017

Spiral Sunday #32 – from the Guimar Badlands of Darwin’s Unrequited Isle

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Our annual undergraduate Tenerife Field Course ends today and later I will say goodbye to the students and my University of Northampton colleagues Janet Jackson and Paul Cox: I’m staying on for another 10 days with Karin to do some additional field work.  The apartment complex where we were located had very poor wifi so I’ve not been able to post much, but we’ve moved now and I’ll try to do more in the coming week.

For Spiral Sunday this week here’s a shot of the logo for one of the protected areas that we always visit, and one of my favourite places on Tenerife: the stunning Malpais de Guimar (Guimar Badlands).

As you can see from the image below, the Guimar Badlands is a fascinating area of xerophytic scrub containing plants that are adapted to very low water levels.  It’s always the first site that we visit with the students, providing a great contrast to any habitats that they might have encountered in Britain.  A perfect introduction to Darwin’s Unrequited Isle.

Guimar 2014.png

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Spiral Sunday #31 – hola Tenerife!

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In a few hours I’m heading of to Tenerife with students and colleagues for our annual undergraduate field course, following which I’m staying on to be joined by Karin for a further 10 days of field work.  I’ll try to post as and when I can, though it’ll be a packed few weeks.

In the meantime this week’s Spiral Sunday is a piece of Canarian independence graffiti that I photographed a few years ago on the road above Guimar.  As I’ve mentioned before, the spiral is an ancient and important symbol in the Canary Islands.  Adios!

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Spiral Sunday #30 – paperclips

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On Wednesday I took my daughter Ellen up to Birmingham to drop off some bags and check on her flat (she’s been in California for a few weeks). Afterwards we went shopping in the city and I came across these beautiful paperclips made from flat copper wire.  They could have been especially designed for me and for Spiral (Easter) Sunday!  I couldn’t resist them and bought a bottle of 100.

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A fossilised flower in amber – with its pollinator!

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There have been only a handful of occasions in my professional life when I’ve been sent a manuscript to review that has caused my jaw to hit the floor with amazement.  The last time it occurred was July 2016 when I received a request to review a study that claimed to have found a fossil flower in amber, with an associated pollinator.  Not only that, but the flower appeared to belong to a species of asclepiad (Apocynaceae subfamily Asclepiadoideae) – the plant group on which I have focused a good deal of my attention over the years.  Even better, the study was by George Poinar, the originator of the idea to extract DNA from amber-encased fossils, thus inspiring Jurassic Park.  George is also the author of two books (Life in Amber and Quest for Life in Amber) that made a big impression on me when I was a PhD student and young post-doc*.

An asclepiad in amber?  From George Poinar?  How could I possibly refuse?!

One of the almost unique features of the asclepiads is that they disperse their pollen as discrete packages – pollinia – that attach en masse to their pollinators.  Only the unrelated orchids do anything similar, which means that identifying the pollinators of asclepiads is much more straightforward than for most plants, making them an ideal model group for studying plant-pollinator interactions.  I’ve had a deep interest in the asclepiads, and particularly their pollination ecology, for over 30 years. Over that time I’ve occasionally daydreamed that perhaps a fossil asclepiad flower in amber might be discovered in my lifetime, or an insect with a pollinarium attached, but I was amazed to see that this study had discovered both in the same piece of amber.  In the image at the top of this post, L and C point to some significant features of the flower, whilst T marks the pollinator.  And T stands for….

….a termite!  Termites are rare overall as pollinators and unknown in that role in relation to the asclepiads; P in this image points to the pollinia attached to the front of the head of the termite:

Poinar_FossilMilkweed_separate pollinia on head

You can get a better sense of the relationship between the flower and the pollinator from the photograph at the end of the this post.

After reading and re-reading and re-re-reading the manuscript I came to the conclusion that assigning the flower to a living group of asclepiads was problematical.  So (with the Editor’s permission) I solicited the views of a few colleagues with more experience than I of some of the less well-known groups of asclepiads, and related Apocynaceae s.s., the morphology of which may shed light on this intriguing fossil.  Without going into the technical details (which I’m happy to discuss with anyone who is interested) we concluded that the flower may well represent a transitional taxon as it has features of a number of different extant asclepiad lineages.  This amber, from the Dominican Republic, is estimated to be between 15 and 45 million years old, so it’s perhaps not unexpected that the set of floral features in this flower appear rather odd from a modern perspective: plants, and their flowers, evolve, just like all other organisms.

George has assigned the flower to a new genus and called it Discoflorus neotropicus  – the “different flower from the Neotropics”.  Millions of years ago this flower bloomed in the tropical forest that covered that part of the world, and attracted a worker termite to feed on its sweet nectar, pollinating the flower in the process.  Before that could take place both flower and pollinator found themselves entombed in the sticky sap being exuded by a leguminous tree called Hymenaea protera.  Many asclepiads are climbers so it’s quite possible that Discoflorus neotropicus was climbing through the branches of that tree when it got stuck.  A fateful day for flower and insect that has come down to the present day as an all-too-rare insight into ancient plant-pollinator interactions: the first fossil asclepiad flower and the first fossil asclepiad pollinator.

The study is published as follows, with a link to the journal:

Poinar Jr, G.O. (2017) Ancient termite pollinator of milkweed flowers in Dominican amber.  American Entomologist 63: 52-56

My sincere thanks to George for allowing me to highlight his research, and use his images, on my blog.  All images are (c) George O. Poinar Jr.

 

*I have a life-long interest in palaeontology that goes back to my youth, collecting fossils on the shale heaps produced from coal mining in the north of England (heaps, incidentally, that my father, grandfather, and paternal uncles had helped to create – all were coal miners in the area).  I very nearly became a professional palaeontologist but the lure of living ecosystems overcame my interest in those that are dead, though my fascination with fossils continues, particularly those in amber and (as I’ve related previously) human ancestors.

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Generalist pollination can evolve from more specialised interactions: a new study just published

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There’s a long-standing idea in biology that ecological specialisation is an evolutionary “dead end” from which species can never emerge.  In other words, if a species becomes so adapted to a particular ecological strategy (could be feeding or habitat requirements or how it interacts with other species ) then no amount of natural selection will result in its descendants evolving different strategies, thereby diversifying into new species.  In particular it’s traditionally thought that evolving broader, “generalist” strategies from narrower, “specialised” ones is highly unlikely.

This has been much discussed in the literature on the ecology and evolution of pollination systems, where traditionally this “dead end” scenario has been accepted.  However a small number of case studies have shown that generalised pollination systems can evolve within much more specialised clades, beginning with Scott Armbruster and Bruce Baldwin’s study of Madagascan Dalechampia (Euphorbiaceae), published in Nature in 1998.

To this limited body of examples we can now add another case study: in the genus Miconia (Melastomataceae), generalist nectar/pollen rewarding strategies can evolve within a clade of plants that predominantly uses a more specialised, buzz-pollinated strategy involving just bees.

The work is part of the PhD research of Vinicius de Brito who is one of the researchers I was privileged to do some field work with in Brazil when I was there in 2013 – see my post: “It’s called rainforest for a reason, right?  Brazil Diary 6“.  Vini is the guy on the left of the photo accompanying this post.  Here’s the citation and a link:

de Brito, V.L.G., Rech, A.R., Ollerton, J., Sazima, M. (2017) Nectar production, reproductive success and the evolution of generalised pollination within a specialised pollen-rewarding plant family: a case study using Miconia theizans. Plant Systematics and Evolution doi:10.1007/s00606-017-1405-z 

Here’s the abstract:

Generalist plant–pollinator interactions are prevalent in nature. Here, we untangle the role of nectar production in the visitation and pollen release/deposition in Miconia theizans, a nectar-rewarding plant within the specialised pollen-rewarding plant family Melastomataceae. We described the visitation rate, nectar dynamics and pollen release from the poricidal anthers and deposition onto stigmas during flower anthesis. Afterwards, we used a linear mixed model selection approach to understand the relationship between pollen and nectar availability and insect visitation rate and the relationship between visitation rate and reproductive success. Miconia theizans was visited by 86 insect species, including buzzing and non-buzzing bees, wasps, flies, hoverflies, ants, beetles, hemipterans, cockroaches and butterflies. The nectar produced explained the visitation rate, and the pollen release from the anthers was best explained by the visitation rate of pollinivorous species. However, the visitation rates could not predict pollen deposition onto stigmas. Nectar production may explain the high insect diversity and led to an increase in reproductive success, even with unpredictable pollen deposition, indicating the adaptive value of a generalised pollination system.

As always, I’m happy to send a PDF to anyone who wants a copy, just drop me an email.

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Spiral Sunday #29 – a pair of guest photos

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Spiral Sunday this week features a couple of photographs I’ve been sent recently.  The first is from one of my PhD students, Alex Laws, taken on a trip to Cornwall earlier this year.  The artist is James Eddy, not a name I was familiar with, but definitely worth checking out, especially as he is a land artist too.

Which leads us to the second picture, sent to me by a Polish colleague, Marcin Zych, of a spiral-shaped piece of land art he found near Olomouc, in the Czech Republic.  It reminds me (on a smaller scale) of Robert Smithson’s amazing sculpture Spiral Jetty (of which I was unaware until it was kindly introduced to me by Carrie McLaughlin of the Texas Pollinator Powwow).

Spiral from Marcin Zych

Many thanks to Alex and Marcin, and to Carrie too.

 

 

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British cuckoo bees – an aide-mémoire

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The British bee season is well underway with lots of reports on social media of queen bumblebees (and even workers in the south), and male and female solitary bees (especially early emerging mining bees – Andrena).  In my own garden I’ve already spotted a couple of bumblebee species, plus the Hairy-footed Flower Bee (Anthophora plumipes) and the Grey-patched Mining-bee (Andrena nitida), amongst others.  Running alongside the emergence of these nest-building bees is a whole suite of “cuckoo” or “cleptoparasitic” bees that, as the name suggests, lay their eggs in the nests of other bees, consuming the pollen that has been collected and, usually, the eggs and larvae of the host bee.

The specificity of the interactions between the cuckoos and their hosts varies a lot.  Some are very host specific, such as the bumblebee sub-genus Psythirus that only parasitises other Bombus species.  Others are much broader in their host use, such as the genus Nomada that parasitises five other British bee genera.

Personally I struggle to recall which cuckoo bees interact with which host bees, especially for those with a broader use of hosts, so I thought I would construct an aide-mémoire in the form of an interaction graph using the R package “bipartite”.  I took the information on which cuckoo bees parasitise which hosts from Steven Falk’s recent (and very good) book Field Guide to the Bees of Great Britain and Ireland.  If anyone spots any errors, please let me know!

The bipartite graph is structured such that the hosts (to the left, in black) are ranked from most to least parasitised (in terms of number of cuckoo genera that interact with them).  The cuckoo bees (in grey on the right) go in the reverse order, from most specialised to least specialised.  Note that this set of interactions only applies to Great Britain and Ireland; breadth of host-parasite interactions is wider on the Continent and elsewhere in the world.

Here’s a link to a better quality PDF of the plot that you’re free to use for your own use: Cleptoplot

Here’s the data matrix (Clepto) and here’s the R script if you want to play with it:

> library(bipartite)

#Turns the CSV data file into a data frame and assigns the first column to be the row names

> Clepto2<-data.frame(Clepto, row.names=1)

#Basic plot of the web

> plotweb(Clepto2)

#To turn the plot 90 degrees and centre the image, change spacing and text size, colours, etc.

> plotweb(Clepto2, method=”normal”, text.rot = 90, labsize =1.5, ybig = 0.7, low.y = 0.7, high.y = 0.98, plot.axes = FALSE, y.width.low = 0.05, y.width.high = 0.05, col.high = “lightgrey”, bor.col.interaction=”black”, bor.col.high=”black”, low.spacing=0.03, high.spacing=0.08)

#Note: save the figure as a PDF, much better quality than PNG

#With thanks to Kat Harrold who provided some of the script

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Spiral Sunday #28 – hearts and vine

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The sun was illuminating the coloured glass of a window ornament and I noticed two things: (i) the lovely juxtaposition between the metal spirals of the ornament and the spiral tendrils of Cyphostemma simulans, a member of the vine family (Vitaceae) that I grew from seed many years ago; and (ii) the fact that our front windows really need washing….  No time for that this weekend, though, been too busy working in the garden with Karin!  That’s Spiral Sunday, enjoy the weather while you can.

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