We are excited to be part of a new Human Frontier Science Programme project starting in October 2021 to investigate the genetics and biomechanics of butterfly wing scale structure formation.
During the final stage of metamorphosis, butterfly wings sprout with hundreds of thousands of scales, each formed by a single cell and carrying precise chitin-based nanostructural motifs. Delicate control of scale structure on the single-scale level determines multiple functions of the wing, including brilliant colors, water repellency, thermoregulation, and lift generation. Despite these functions being of great interest to biologists and engineers alike, we only have limited knowledge of the mechanisms underlying scale formation. This project takes inspiration from nature, to understand how functional nano-structures are assembled in butterfly wing scales from a biological, physical and engineering perspective.
We are seeking an enthusiastic student with interests in ecology and evolution to work on a project investigating the evolution of wing scale nanostructures and thermal adaptation in tropical Andean butterflies. The wings of butterflies are covered in thousands of scales that have evolved to serve a range of functions including aerodynamic efficiency, colour signalling, camouflage, hydrophobicity and thermoregulation. Fundamental to these functions is the nanostructure of the scales.
Interest in organisms’ adaptation to their thermal environment has grown in recent years as we try to understand and predict how organisms will respond to climate change. Butterflies are one of the best-studied insect groups with respect to thermal adaptation. While the importance of the wings for thermoregulation has been known for some time, only recently has the importance of the wing scale nanostructures begun to be appreciated.
The project can be tailored to the interests of the student but would likely include working with museum collections of butterflies at the Natural History Museum (under the supervision of Dr Huertas), using cutting-edge techniques for measuring scale nanostructure (under the supervision of Dr Parnell) and computational analysis to investigate ecological correlates of wing scale nanostructure (under the supervision of Dr Thomas). It could also involve fieldwork in South America to obtain further butterfly specimens, ecological data and/or test hypotheses about thermal adaptation. This project builds on recent work in Dr Nadeau’s research group investigating the evolution, genetics and development of butterfly wing scale nanostructures and thermal adaptation in tropical Andean butterflies. The outcomes of this project could have applications in the design of nanomaterials to improve the thermal efficiency of man-made structures such as windows and solar panels.
UKRI provide the following funding for 3.5 years: • Research Council Stipend – at least £15,285 (UKRI rate for 2020/21) • Tuition Fees at the UK fee rate (2020/21 rate £4,406) • Research support and training grant (RTSG)
Please note that international and EU fee rate candidates would need to cover the remaining amount of tuition fees by securing additional funding. International and EU tuition fees for 2021 entry £23,750. Not all projects will be funded; the DTP will appoint a limited number of candidates via a competitive process.
This research, published in the Journal of Evolutionary Biology, started out as Masters project by Hannah Bainbridge. She investigated vairation in the size and shape of the red band found on the wing of two butterfly species that mimic each other, Heliconius erato and Heliconius melpomene. These two species are known to use the same major-effect genes to control major differences in colour and pattern that are found between popualtions, but more subtle variation has not been investigated to the same extent. We find that this variation is also controlled by some of the same major-effect genes, but overall the two species largely seem to use different genes to control it.
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.
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.
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.
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).