Sunday, January 23, 2011

Lab-meeting on insect wing colouration and UV-vision

At the first lab-meeting of 2011 (January 26, at 10.15 in "Darwin"), I was thinking that we should discuss two new interesting papers about insect wing colouration and insect UV-vision. The first one is the beautiful paper in PNAS by some systematist colleagues from our own department in Lund (see pictures above), and the second one is about sexual selection and UV-vision in butterflies by Ron Rutowski's group. The two papers are partly related, and should be read as companions. They have some relevance to our past and ongoing work on wing colouration in damselflies, including the UV spectrum (as yet unpublished, but in preparation by Maren, Mikkel and myself). These two papers can be downloaded here and here.

The Morehouse/Rutowski-study deals with female choice of male wing colouration of white cabbage butterflies. It deals with vision in the UV-spectrum, and how male attractiveness and predation risk are linked to each other, when explicitly modelling the UV-vision properties of mates and predators. It has also been covered by the popular science site Science Shot. It is highly relevant to our own work on damselflies, I think. Incidentally, Ron Rutowski will be external opponent on a thesis on butterfly ecology in Stockholm on March 18, 2011, where I am in the committée and there will be a small symposium the day before where Mactheld and I will give research presentations, so we can ask him then about details this study if some questions come up during our lab-meeting on Wednesday.

The "Lund paper" in PNAS is about iridescent colouration on transparent insect wings ("Wing Interference Patterns", or WIP:s), how such WIP:s can be used as species and sex-identification cues and the implications for systematics and evolutionary developmental biology ("evo devo"). It might very well turn out that this paper will revolutionize and speed up the process of species identification in some difficult groups such as small hymenopterans and dipterids. If the paper holds what it promises, it might even be more useful than DNA-based species-identification methods, as it is faster, cheaper and non-invasive, making the method of much practical use when working with museum collections of small animals where one could not (or do not want) to sacrifice tissue, but need to identify species anyway. Obviously, the paper have implications also for speciation, species recognition and sexual selection.

There are two detailed and interesting blog posts about this paper by evolutionary geneticist Jerry Coyne on "Why Evolution is True" and by Ed Young at "Not Exactly Rocket Science". Both are worth reading, in addition to the original paper. Ed Young points out another interesting implication of this study: "Since the colours come from the microscopic shape of the wing, every hair, bump, ridge and vein affects the pattern of the WIPs. If an insect evolves a larger, thicker wing, its colours change. If the wing gains or loses veins, the colours change. Indeed, the unseen influence of these colours could explain why the veins of some insect wings are incredibly varied, for no obvious reason. Through these changing colours, the evolution of flies and wasps may start becoming more transparent." 

 As we have often discussed the adaptive significance of various small morphological aspects of insect wings (e. g. shape, the number of positions of veins etc.) in our own work in our lab, this adds another interesting dimension to such structures, although it should be said that these WIP:s are only known to operate on small wings (1 cm or less) and are unlikely to be important in larger insects like odonates, unfortunately.

I hope you will enjoy these two interesting papers, as well as appreciate the links above. Time and place as usual for our lab-meeting: Wednesday (January 26) at 10.15 in "Darwin". Any fika volunteer?

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