Brian suggests ‘Giant H. erato FG hybrids maybe (DdSdsd)’. Any more suggestions regarding their genotype/species?

The trailer can be seen here on YouTube

Here are some links that give more details:
Science perspective article by Sean Carroll
Link to original article

The study focused on the Amazonian species Heliconius numata, which mimics several other butterfly species at a single site in the rainforest. One population of Heliconius numata can therefore feature many distinct wing colour patterns resembling those of other butterflies, such as the Monarch’s relatives Melinaea, which are unpalatable to birds. This acts as a disguise, protecting them against predators.

The researchers located and sequenced the chromosomal region responsible for the wing patterns in H. numata. The butterfly’s wing-pattern variation is controlled by a single region on a single chromosome, containing several genes which control the different elements of the pattern. Known as a ‘supergene’, this clustering allows genetic combinations that are favoured for their mimetic resemblance to be maintained, while preventing combinations that produce non-mimetic patterns from arising. Supergenes are responsible for a wide range of what we see in nature: from the shape of primrose flowers to the colour and pattern of snail shells.

The researchers found that three versions of the same chromosome coexist in this species, each version controlling distinct wing-pattern forms. This has resulted in butterflies that look completely different from one another, despite having the same DNA.

“We were blown away by what we found”, said Dr Mathieu Joron of the Muséum National d’Histoire Naturelle, who led the research. “These butterflies are the ‘transformers’ of the insect world. But instead of being able to turn from a car into a robot with the flick of switch, a single genetic switch allows these insects to morph into several different mimetic forms – it is amazing and the stuff of science fiction. Now we are starting to understand how this switch can have such a pervasive effect”

Professor Richard ffrench-Constant of the University of Exeter added: “This phenomenon has puzzled scientists for centuries – including Darwin himself. Indeed, it was the original observations of mimicry that helped frame the concept of natural selection. Now that we have the right tools we are able to understand the reason for this amazing transformation: by changing just one gene, the butterfly is able to fool its predators by mimicking a range of different butterflies that taste bad.”
This single supergene also appears important in melanism in other species, including moths. In April 2011, a team led by Liverpool University explained in the journal Science how the Peppered Moth developed its black wings in nineteenth-century Britain’s sooty industrial environment.
“This supergene region not only allows insects to mimic each other, as in Heliconius, but also to mimic the soot blackened background of the industrial revolution – it’s a gene that really packs an evolutionary punch,” added Professor Richard ffrench-Constant.

Evolving wings
The Edmonton meeting was no exception to the rule, and there was a generous helping of Heliconius biology to boot. Much of this revolved around wing pattern genetics, with ongoing efforts to identify the genes that control wing patterns finally starting to come to fruition after some ten years of effort in labs on several continents. Perhaps most exciting, the identification of striking expression patterns at a transcription factor previously associated with eye development, by Arnaud Martin and Riccardo Papa, appear to signal the identification of the loci controlling red pattern elements in both Heliconius erato and melpomene. Similarly, Marcus Kronforst has now identified a regulatory gene (transcription factor) that controls the switch between yellow and white in the Heliconius cydno group, while Nicola Nadeau presented data for a cell cycle regulator that is prime candidate for the switching of yellow patterns in Heliconius melpomene.

For me, the identification of these genes has been something of an obsession over the past few years and it is a relief that we are finally close to an answer. The results seem to confirm the hunch that we have had for a while now, that the same genes are involved in producing similar patterns across many Heliconius species. There really is a common ‘toolkit’ of wing patterning genes that are shared across many species. What is surprising is that the genes identified so far do not seem to obviously fall into a single signalling pathway, or interacting network. The challenge now is to figure out how they have evolved to produce the remarkable patterns of Heliconius from their fritillary ancestors, and whether there is something specific to the way patterns are generated that allows such remarkable diversity to be produced in Heliconius.

There was another surprising result presented at the meeting, from linkage mapping projects in Bicyclus (a satyrid or brown butterfly) and the peppered moth. In both species, genes affecting wing patterns (eyespots and melanic wing colouration respectively) map to the same regions of the genome as one of the Heliconius wing patterning genes that was first mapped in our lab. If it really turns out that the same genes are involved in these species, this would imply that there is a shared mechanism for wing evolution across moths and butterflies, which dates back to the time of the dinosaurs. Now that is pretty cool.

Hissing peacocks and new dimensions to communication
One of the most surprising talks for me was a tale of hissing peacocks and mice. Peacock butterflies are known for the stunning eyespots on their wings, which are used to startle predators when they are approached. What is less well known, is that they also make a hissing sound with their wings. This proves remarkably effective at deterring mice, that would otherwise make a meal of them during hibernation. Videos of hibernating butterflies presented by Martin Olofsson showed mice approaching sleeping butterflies, and being startled off by wing flaps, in the complete darkness of a winter roost. It seems that the startle display of the stunning peacock eyespots is complemented by an equally scary audible signal generating by rubbing the wings together. Heliconius cydno are also supposed to make clicking noises (although I have never heard them myself) – perhaps they serve a similar function.

While sounds may be important for some butterflies, a far more ubiquitous mode of communication is through scents. However this remains a black box of butterfly biology, which is only just beginning to be opened. Fritz Muller (famous for the discovery of Mullerian mimicry), was the first to described the feathery ‘androconial’ scales on butterfly wings that diffuse their scents, in the 1860s. In Edmonton, Carla Penz and Naomi Pierce, discussing owl butterflies and blues respectively, both described remarkable patterns of diversity in the placement, shape and form of these androconial patches on the wings. Such rapid evolution generally signals strong selection, and in this case it is likely driven by sexual selection. This was confirmed by Caroline Nieberding, who has identified the compounds that the African butterfly, Bicyclus anynana, uses for sex. The females of this species choose to mate with males based in part on their chemical bouquet, with the older males having a distinct smell that is preferred by females. This makes sense, as older males have survived the trials of life on the African savannah and are therefore more likely to have successful combinations of genes that will produce fit caterpillars. However, the puzzle is why males don’t cheat the system and pretend to be older than they really are by producing the characteristic chemical signal. Perhaps the signals are expensive or difficult to produce, but there is clearly potential for conflict between the sexes in the use of these chemical signals that could lead to an evolutionary arms race and perhaps explain the rapid evolution of the androconial patches and their chemical bouquet.

In Heliconius, a poster by Catalina Estrada described a different set of chemicals known as anti-aphrodisiac pheromones. These have the opposite effect to the Bicyclus sex phermones, and as their name suggests deter mating by males. The chemicals are transferred from males to females at mating, and presumably serve the interests of females who benefit by avoiding pestering by ardent suitors (although such a benefit has yet to be demonstrated). Strikingly there is also a similar pattern of rapid evolution in these chemicals, with closely related species commonly differing in their chemical composition. Catalina has demonstrated that species in the pupal-mating clade evolve more slowly than the non-pupal-maters. This also fits with the idea that conflict could lead to rapid evolution, as among pupal-maters the males call the shots and there is little opportunity for females to choose their partners, while in non-pupal-maters both species can choose so there is more chance for them to differ in opinion – hence more conflict. Once again, sexual conflict is associated with faster evolution of chemical signals.

Researchers are just beginning to explore the world of butterfly scents, and this is clearly an exciting area for future research. No doubt ‘Biology of Butterflies’ in 2014 will have more on this topic…

And more…
Overall the meeting included many more aspects of butterfly biology than I can even begin to mention here. Butterflies continue to be at the forefront of our understanding of the biological response to climate change, with striking range changes very evident at both the warm and cold fringes of species ranges. However, at this meeting there was a shift in emphasis away from simply documenting range changes in response to climate, towards investigating how we might best respond to such changes. Other talks covered so many aspects of butterfly ecology, population biology and evolution that I was exhausted by the end of the week. To recover, we headed south to the Alberta prairies and Drumheller, for some dinosaur therapy.

Over the two days, Heliconius biologists, bioinformaticians, others from sequencing centers and places of the sort, developed a timeline and framework for annotating, curating, sharing and analyzing the H. melpomene genome. The first freeze and release of an assembled H. melpomene genome could be within the next 3 months. Servers at UCI are already in place in order to hold the sequence data, a BLAST server and a GBROWSE server. Over the coming months CHADO databases will be built, annotation pipelines will be laid, and preliminary genomic analyses will begin.

Beyond the first H. melpomene reference genome being done with 454, we have had our eyes on other races and species of Heliconius to sequence. Plans were outlined for re-sequencing the genomes H. cydno, H. numata, H. erato and more H. melpomene races using Illumina. Plans were also made for RAD-tagging, using Illumina. Mapping families are currently being raised in Panama to create a RAD-tag linkage map for the H. meplomene genome. We are also considering using RAD-tags to scan for population differentiation between the various races of H. erato and H. melpomene. At this point the genome project seemed to be expanding significantly, but the biology was getting a lot more interesting. We just need to convince some funding agencies.

The meeting slowed to a discussion of funds, and how to afford all these awesome experiments. Grant opportunities were discussed and working groups on various topics/aspects relevant to the genome project, were assembled. The meeting ended with a fantastic dinner at the St. John’s College, where they offered many of us way too much wine and port.

All in all, the HGC seems to have a solid game plan, a strong group of interested researchers, some money, and data pouring in, making it very soon that we can expect to see good working draft of the Heliconius genome.

Accommodation will be available from Weds 24th until Friday inclusive at no cost, thanks to support from St Johns College.  The meeting will be held in the Old Music Room in St Johns College. For a map of college, see here.

Draft schedule:

Thursday 25th March

• Morning – Assembly of a reference genome. A brief description of the data collected so far and status of the current assembly. Discussion of priorities for obtaining an improved assembly of the reference genome.
• Comparative genomics goals. Review of the scientific goals outlined at the previous meeting for genome resequencing and comparative genomics.  Discussion of resequencing data obtained so far (if any) and goals for remaining funds in the initial round of money.
• Afternoon – Annotation and databasing. Discussion of tools available for genome annotation and databasing.  Assignment of tasks to different research groups.
• Publication plans. Discuss plans for publication of the genome, and in particular for how further data collection might be focused.

Friday 26th March

• Morning – Presentations and comments from non-HGC members. Attendees with experience in genomics of other organisms will be invited to briefly introduce their own interests and comment on the project.
• Afternoon – Future plans. Outline specific plans for grant proposals to take advantage of the preliminary data.
• Conference Dinner in the Wordsworth Room of St Johns College at 7 for 7:30pm (let me know of vegetarian/dietary requirements)

Homework: Please try to have a look at previous genome papers with a mind to what we want to achieve in ours.  Here is a Zip file with some recent papers to look at.

Attendees (with accommodation)

Mark Blaxter (not friday)
John Davey
Brian Counterman
Richard ffrench-Constant
Paul Wilkinson (veg)
Alexie Papanicolaou
Jim Mallet
Owen McMillan
Marcus Kronforst
Nicola Chamberlain
Bob Reed
Chris Elsik
Stephen Richards
Sean Mullen
Riccardo Papa
Rainer Lehtonen
Mathieu Joron
Lise Frezel
Marian Goldsmith
Durrell Kapan

Attendees (no accommodation)

Kanchon Dahamasapatra
Jamie Walters
Gos Micklem
Adrian Carr
Daniel Lawson
Simon Baxter
Laura Ferguson
Nicola Nadeau
Rob Jones
Richard Merrill
Adam Spargo
Annabel Whibley

Travel
A couple of people have asked me about travel to Cambridge from the US, so I thought I’d send out a general email rather than replying individually. The closest airport is London Stansted but unfortunately not many transatlantic flights go into there. So you are most likely to be looking at a flight to either London Heathrow or London Gatwick. Both of these are a couple of hours travel from Cambridge, either by bus or train. I tend to prefer the bus from Heathrow (this avoids using the London Underground, which can be hectic at busy times), and the train from Gatwick (you should get a ThamesLink train to Kings Cross St Pancras, from where you can change to the train for Cambridge – avoid the Gatwick Express which goes to Victoria station).

See also the University web pages about travel

On the wings of a butterfly

Since Darwin’s time, Amazonian butterflies have fascinated evolutionary biologists as examples of evolution in action.

On reading Henry Walter Bates’ 1862 account of his travels in the Amazon, Charles Darwin was captivated not only by Bates’ description of the stunning diversity of butterfly species and wing patterns found in the Amazonian jungle, but also by the impressive mimicry between unrelated species. He wrote: ‘It is hardly an exaggeration to say, that whilst reading and reflecting on the various facts given in this Memoir, we feel to be as near witnesses, as we can ever hope to be, of the creation of a new species on this earth.’1

Bates hypothesised that mimicry evolved to confuse predators. Edible butterflies, for instance, copied the wing patterns of toxic species so that predators would avoid eating them. He also described what looked like evolution in action: he observed a continuum, from variable species, in which different wing patterns were found together in the same locality, through to related species with different wing patterns. Now, 150 years later, modern science has taken this to another level, with new research that attempts to uncover the genetic predictability of evolution by identifying the genetic basis of wing pattern mimicry.

The importance of pattern

We now recognise that not only do edible species mimic nasty ones (today called Batesian mimicry), but that several nasty species can also benefit from mimicking one another (Müllerian mimicry) – bees and wasps being a familiar example. Many of the Amazonian butterflies described by Bates are in fact Müllerian mimics, and the best-studied group are the genus Heliconius, the passion vine butterflies. Recent work has focused on the Heliconius butterflies as a case study in evolutionary biology.

Studies of Heliconius wing patterns in the wild have confirmed Bates’ hunch: changes in wing pattern play a big role in determining how successful the butterflies are in both mating and avoiding being eaten. Using flapping models with different patterns, the researchers have shown that the butterflies choose to mate with individuals that look the same as themselves; because of this, over time, different patterns are likely to split into new species. In addition, hybrids between populations with different patterns have intermediate patterns that are not recognised by predators as harmful and therefore suffer disproportionately from attacks, reinforcing the split into new species.

This dual role of wing patterns in signalling both to predators and to potential mates makes pattern a ‘key trait’ for speciation. As Bates suggested, shifts in wing patterns do indeed lead to the evolution of new species.

Signatures of selection

One of the current hot topics in evolutionary biology is to what extent we can predict the path of evolution. One particular Heliconius species (Heliconius melpomene) is an ideal system in which to address this question because it has many geographic populations with very different colour patterns. A major collaborative project focusing on the genetic basis of wing patterns is underway with funding from the Biotechnology and Biological Sciences Research Council (BBSRC), Royal Society, Leverhulme Trust and Natural Environment Research Council (NERC).

Over the past decade, the researchers have been collecting different forms of H. melpomene from around South America, carrying out genetic crosses at a field station in Panama. These crosses have shown that dramatic differences in colour pattern are controlled by just a handful of genes, and that these genes are clustered together on four out of the 21 Heliconius chromosomes. The genes act as wing pattern ‘switches’, turning on and off the presence of major pattern elements, such as a large red forewing band. The challenge is to find out precisely what these genes are and how they work.

In collaboration with the Welcome Trust Sanger Institute, regions of the butterfly genome are being sequenced to try and identify the specific nature of the pattern switches. The expectation was that the switches would correspond to well-known genes, perhaps controlling wing development or colour pigments. In fact the two genomic regions studied so far each contain around 20 genes none of which is known for its involvement in these processes. This is in itself exciting as it implies that novel mechanisms of pattern determination are operating; current research is focused on determining which, of all these genes, are having an effect in the butterfly.

Genetics of mimicry

What attracted Darwin and others to mimicry as a case study in evolution is its repeatability – the same patterns evolve in distantly related species. A key question for an evolutionary geneticist is therefore whether the patterns are generated by the same genetic mechanisms, or different ones. Again, Heliconius butterflies are a good system to study this.

Heliconius melpomene co-mimics another species, Heliconius erato, all over the neotropics – in any location you care to look you will find that the two species have evolved identical patterns. Recently, in collaboration with research groups in the USA, it has been shown that pattern switches in the two species are controlled by the same regions of DNA, such that genes at identical locations in the genome code for either a red forewing band or a yellow hindwing bar. This implies that evolution of the same mimicry patterns in the two species has been made easier by a shared genetic system. While predation against abnormal wing patterns drives the evolution of mimicry through Darwinian natural selection, a shared developmental system may bias the raw materials in favour of certain kinds of patterns.

Of course, the link between wing pattern adaptation and speciation requires changes in behaviour. The mating preferences of divergent populations need to evolve in order to match their wing patterns. Remarkably, crossing experiments currently being carried out in Panama show that the genes underlying these changes in behaviour are closely associated with colour pattern genes. It seems that there are ‘hotspots’ in the genome for evolutionary change, influencing traits as diverse as wing patterns and mating preference.

An enduring example

It is an exciting time to be studying butterfly mimicry. The combination of population genetic, developmental and behavioural approaches is starting to answer the issues Darwin and Bates themselves debated; questions which were posed at the very dawn of evolutionary biology. Over the last 150 years, Heliconius butterflies have persisted as an example of evolution in action. With the imminent sequencing of the Heliconius melpomene genome, they will no doubt continue to be so for some time yet. Charles Darwin would surely have approved.

1[Darwin, C.R.] 1863. [Review of] Contributions to an insect fauna of the Amazon Valley. By Henry Walter Bates, Esq. Transact. Linnean Soc. Vol. XXIII. 1862, p. 495. Natural History Review 3: 219–224.

Thanks to those in my lab who helped with the text, Laura Ferguson in particular.  If anyone is interested in reading more about the idea of genomic ‘hotpots’ for evolution, there is a nice recent review of the evidence in Heliconius by Riccardo Papa and others, and a more general overview in Science magazine.

We have also applied to NESCENT to fund HGC meetings based at Duke University in North Carolina.

Another of the winners was Nick Barton, who also worked with Jim on Heliconius hybrid zones in the late 1980′s when they were both at UCL (Jim was a postdoc with Nick).  Apparently, Nick visited Tarapoto, Peru during the fieldwork – after months of carrying butterflies across treacherous terrain for release on the other side of the hybrid zone, Jim was getting depressed at lack of progress (a familiar feeling to anyone who has spent long periods in the field). Nick turned up and did a quick likelihood calculation on the back of an envelope to show that the mark-release-recapture experiment was showing significant selection and all was well.  In those days Tarapoto was a pretty remote place…

Anyway, if you want to know more about the linnean society medals, have a look at their press release.

Winners of the Darwin-Wallace Medal, 2009