Category Archives: News

New publication! Clines in iridescent structural colour

We have a new paper out in Molecular Ecology where we investigate variation in iridescent structural colour in the mimetic butterflies Heliconius erato and Heliconius melpomene. Both of these species vary from having to blue iridescent colour in Colombia to being matt black in Panama.

In her PhD thesis work Emma Curran showed that the colour change is more gradual in H. melpomene than H. erato and this is most likely due to weaker selection acting on the colour in this species. She also investigated population genomic structure and fund that while H. erato clusters into two different groups in Panama and Colombia, H. melpomene doesn’t. While the colour change happens in a similar place in both species, strongly suggesting that mimicry between the species has been important in its evolution, the differences between species hint at different evolutionary histories.

This is the first time that variation in iridescent structural colour has been investigated in wild Heliconius populations. This trait is also different to the colour pattern traits that have most commonly been investigated in Heliconius because it is a quantitative trait, controlled by many loci, rather being controlled by a single genetic locus. Our results therefore also shed light on the major question of how differences in quantitative traits evolve.

New publication! Altitude and life‐history shape the evolution of Heliconius wings

We have a new paper out in Evolution about the effects of altitude and life history on wing size and shape in Heliconius butterflies. Work done by PhD student Gabriela Montejo‐Kovacevich, and former Masters student Jennifer Smith, shows that species found higher up the slopes of the Andes tend to have larger and rounder wings. We also found that in species with gregarious larvae, females were larger than males, while the opposite was the case for species with solitary larvae. This is the first publication from our NERC funded project on adaptation to altitude in tropical insects.

Jennie and Gabby (and Kathy) collecting butterflies in the Andes
Jennie and Gabby (and Kathy) collecting butterflies in the Andes

Congratulations Mel!

Congratulations to Mel Brien who submitted her PhD thesis in August, just in time to go and present her work at the ESEB Congress in Turku, Finland.

The lab hanging out with one of the residents of Moonin land at the ESEB congress dinner

New publication! Phenotypic variation in Heliconius erato crosses shows that iridescent structural colour is sex-linked and controlled by multiple genes

We have a new paper out in the Journal of the Royal Society, Interface Focus, as part of a special issue on structural colour. Mel has used the variation in iridescent blue colour that we see in crosses between blue and black subspecies of Heliconius erato, to investigate the genetics of this trait. She shows that it is controlled by multiple genes, one or more of which are located on the Z sex-chromosome. Juan also investigates how one aspect of scale structure (ridge spacing) varies in these crosses. He shows that closer ridge spacing produces brighter blue colour, and that this trait also appears to be controlled by several genes. This is the first investigation of the genetics of structural colour in Heliconius. In fact, very little is known about the genetic control of structural colour in any animal. We plan to follow up this work by investigating the molecular genetics of structural colour production in these butterflies.

Crosses in Heliconius erato

Congratulations Dr Curran!

Congratulations to Emma who successfully defended her thesis at the end of November. Mel made this amazing hybrid zone cake to celebrate. It (very accurately) shows the hybrid zone that Emma worked on for her thesis, where the butterflies go from being black (in the north) to blue (in the south).

Festival of the Mind

Next week the university is hosting the Festival of the Mind a collaboration between our academic colleagues and experts from Sheffield’s cultural and creative industries.

We have been working with artist Sarah Jane Palmer to create artwork telling the story of some our research. this will be on display in the millennium gallery from Thursday 20 – Thursday 27 September as part of the Futurecade.  Sarah will also be giving a talk at 4pm on 20 September, with a question and answer session with Nicola.

Postdoc and research assistant positions on new NERC funded project

We have recently been awarded a NERC grant to investigate adaptation to altitude in Heliconius butterflies. The project is in collaboration with Chris Jiggins at the University of Cambridge, Marjo Saastamoinen at the University of Helsinki and Caroline Bacquet at IKIAM University in Ecuador.

We are currently advertising two positions on this grant:

A 3-year postdoc position. This will It will involve intensive rearing and phenotyping of butterflies to characterize both inter- and intra-specific differences in thermal adaptation at different altitudes in the Andes. This will be followed by generation and analysis of high-throughput genomic data to identify underlying genetic differences. The rearing and phenotyping will be conducted in Ecuador, therefore you will be expected to spend significant amounts of time working in Ecuador with partner organisations. You will have a strong commitment to evolutionary research with skills in at least one of:
analysis of large genomic data sets; analysis of quantitative trait variation; or insect ecophysiology. Being able to communicate in Spanish would also be an advantage.You will hold a PhD or equivalent experience in evolutionary biology and will have experience of research in evolutionary genetics and analysing large data sets.

Apply here.

A 2-year graduate research assistant position. This will involve assisting the postdoc, primarily with rearing and phenotyping of butterflies to characterize both inter- and intraspecific differences in thermal adaptation at different altitudes in the Andes. The rearing and phenotyping will be conducted in Ecuador, therefore you will be expected to spend significant amounts of time working in Ecuador. You will have an interest and enthusiasm for evolutionary research with good attention to detail and experience of accurate collection and handling of data. You will have a good honours degree or equivalent experience in a biological discipline and experience of recording and checking numerical data in a research context. You will have an enthusiasm for evolutionary/ ecological/ entomological research and experience of rearing insects. Being able to communicate in Spanish would also be an advantage.

Apply here.

The closing date for applications for both positions is the 18th of June 2018. The starting dates for both positions are around the 1st of September 2018, but there may be some flexibility. Contact Nicola for further information or informal enquiries about either position.

New publication! Wing scale ultrastructure underlying convergent and divergent iridescent colours in Heliconius

Our paper describing the structures responsible for producing iridescent blue colour in five species of Heliconius butterfly is out in print today in the Journal of the Royal Society Interface.

Heliconius, also know as Passion-vine butterflies, from rainforests in Ecuador have bright wing colours to warn predators that they are toxic. Different species have evolved similar colours, helping predators learn to avoid them. Some of their colours are iridescent, changing with angle. These colours are produced, not by light absorbing pigments, but by nano-structures. Colours of this type are known as structural colours.

Mimetic butterflies, Heliconius erato cyrbia and Heliconius melpomene cythera, with structurally produced blue colour. Credit: Melanie Brien

In our paper we have identified the nano-structures that produce these colours: layered ridges on hairs-width-sized scales covering the wing, which cause constructive interference of blue light.

Part of a Heliconius eleuchia scale, showing the scale ultrastructures. Blue iridescent colour is produced by the layered ridge lamellae.

Similar structures are used by different species, but the colour and brightness of the species differs because of slight differences in the nano-structural features. It seems that some features can evolve faster than others, suggesting that these are more easily modified. There are noticeable differences, particularly in brightness, between the mimetic species pairs, H. erato cyrbia, H. melpomene cythera and H. eleuchia, H. cydno. These differences in brightness come from features of the ridges, including how flat they are and how many layers are present, as well as how densely packed the ridges are on the scale. We find that the packing of the ridges appears to evolve relatively quickly and is fairly similar between co-mimics, while the features of the ridges themselves appear to evolve more slowly, explaining the lack of perfect mimicry.

The evolution of iridescent blue colour in Heliconius. This colour is found in just a few species (blue branches) but has evolved multiple times. The labelled species, accompanied by wing photographs, are those we investigated in our paper.

The project was a collaborative effort with colleagues in the Physics Department, in particular Andrew Parnell, as well as using data we collected at the ESRF, and with key input from Pete Vukusic in Exeter. The butterflies were collected in and around the Mashpi Reserve in Ecuador, providing a unique ecological viewpoint by allowing us to investigate butterflies from the same community.