The toucan bill as a thermal radiator: adaptation or exaptation?

Have you ever visited a rainforest in the New World, such as in Costa Rica or elsewhere in Latin America? If so, it is a great chance you have seen a toucan, those big fruit eating birds with HUGE bills (see picture above).

The function of such large bills has been quite unknown, but now a new study published in Science indicates a surprising novel function: the bill might be important as thermal radiator (bottom figure). Using a thermal image camera of similar kind as we have bought to our lab, the researchers were able to demonstrate that the many blood vessels in the bill helped to quickly cool down the bird and get rid of excess heat. The birds could actually cool down by ten degrees in only a few minutes (yellow areas are high temperature areas in the bottom picture).

This study is interesting for several reasons. First, it shows how new techniques can help to answer old questions and give new answers (sometimes quite surprising, as in this case). Second, it shows that one has to have an open mind when trying to understand the adaptive functions of traits and what traits are "for". Most people, including myself, probably thinks that the bill evolved "for" the specific purpose of efficiently picking fruit. This might very well be the case, but once the bill have reached a certain size, it can also secondarily get another function in the form of a thermoregulator.

In this context, perhaps the thermoregulatory function is simply an exaptation, i. e. not a true adaptation in the language of paleontologist Stephen Jay Gould? Or perhaps the bill was further exaggerated once it had reached its "optimum" size from the perspective of fruit picking, and only the extra length is a true adaptation in the context of thermoregulation? Perhaps future phylogenetic comparative studies involving other toucan species with different bill sizes and the thermal image camera can provide some answers to these fascinating questions?

(Thanx Maren for the tip!)

Update from the Ischnura field season

The damselflies are certainly happy this summer.  Anna Norden (see pic at right) and I have found ourselves with plenty of specimens from our surrounding Skåne populations, especially with the recent sunshine.  The Swedish sun has even managed to give us slight sunburns today.

The new IR camera is up and running in the lab.  We are taking pictures of both Ischnura elegans and Colopteryx sp. under cold and hot treatments.  We are refining the experimental setup and hope to keep adding more dimensions to the study.  IR imaging is quick and easy and seems to have endless potential.

Along with IR we are continuing wing analyses, behavioral and fitness studies, and population surveys of I. elegans.  If conditions stay hot and sunny we hope to continue wandering Skåne catching damselflies well into August.

This season we have begun collaborating with the Lund Vision Group who are keen on deciphering the Ischnura vision system.  Almut Kelber and Miriam Henze are using the polymorphic damselfly system to investigate how male vision relates to the spectral variation of the female color 

morphs.  Pairing vision with signal, they are investigating both sides of the interaction by measuring male spectral sensitivity and visual acuity (see pic at left), while quantifying the reflectance and structure of female color.  We look forward to their results from this first season!

We are also keen on getting volunteers out in the field with us.  We have had a few super enthusiastic students come out and to learn about the damselfly system and we look forward to having more. 

On isopod antipredator adaptations in PLoS ONE

This week, Fabrice Eroukhmanoff and I have a paper about antipredator adaptations and phenotypic integration in the famous aquatic isopod (Asells aquaticus), the main study organism in Fabrice's Ph.D.-thesis work. The paper is published in the popular and fast growing "Open Acess"-journal PLoS ONE, which despite some initial skepticism, has rapidly emerged as a major scientific publisher.

I would encourage you to read this paper and if you have time and have registered as a user at PLoS, feell free to comment upon it. This is one of the major strength of publishing in PLoS-journals: the interactivity between readers and published articles.

Here is the abstract for those who are interested:

Fabrice Eroukhmanoff, Erik I. Svensson

Abstract

"It is increasingly being recognized that predation can be a strong diversifying agent promoting ecological divergence. Adaptations against different predatory regimes can emerge over short periods of time and include many different traits. We studied antipredator adaptations in two ecotypes of an isopod (Asellus aquaticus) that have, diverged in parallel in two Swedish lakes over the last two decades. We quantified differences in escape speed, morphology and behavior for isopods from different ecotypes present in these lakes. Isopods from the source habitat (reed) coexist with mainly invertebrate predators. They are more stream-profiled and have higher escape speeds than isopods in the newly colonized stonewort habitat, which has higher density of fish predators. Stonewort isopods also show more cautious behaviors and had higher levels of phenotypic integration between coloration and morphological traits than the reed isopods. Colonization of a novel habitat with a different predation regime has thus strengthened the correlations between pigmentation and morphology and weakened escape performance. The strong signature of parallelism for these phenotypic traits indicates that divergence is likely to be adaptive and is likely to have been driven by differences in predatory regimes. Furthermore, our results indicate that physical performance, behavior and morphology can change rapidly and in concert as new habitats are colonized."

Welcome to Sophia Engel, our new postdoc!

This bloggpost has also been published on the CAnMove-blogg.

Together with my co-PI Anders Hedenström, I am pleased to introduce our first CAnMove postdoc Sophia Engel. Sophia will join CAnMove soon on a project dealing with insect flight adaptations and evolutionary ecology, dealing with adaptations for dispersal and predator avoidance. This is an exciting project that will combine field and wind tunnel studies, using moths and calopterygid damselflies as model organisms. Both Anders and I are thus extremely happy to host Sophia as a shared postdoc. Below, I will let Sophia introduce herself in her own words:

"I am interested in the interaction of physiological capabilities, ecology, and evolution in shaping a species’ life-history. My previous research has been at the interface of ecology and physiology: For my doctoral work I focused on avian migration. I combined wind tunnel studies and detailed measurements of water- and energy budgets at various ambient conditions with modeling approaches, and showed that dehydration can be a limiting factor for flight duration under naturalistic ambient conditions for my model species, the Rose-coloured Starling. A more recent project is focused on understanding the effects of climate variability on primary productivity, arthropod consumer performance and ultimately the structure and function of the food web in the Chihuahuan Desert of central New Mexico. I am looking forward to combine these two lines of research, wind tunnel studies and insect ecology, in the project “insect flight and morphological trade-offs” at the CAnMove center in Lund!"

Annual Barbecue in Dalby 30 June

It is time for our annual lab-barbecue in Dalby, at Erik's & Pia's place (Lyftvägen 10). Above, you see some pictures from last summer and how fun it can be. This annual barbecue now goes in to its tenth season, as I started it in the summer of 2000, my first real field season with damselflies.

Please bring something to put on the grill, as well as something to drink. We will serve some sallads and desert. Also, if you feel for it, you might of course bring some entertainment, such as music instruments etc. We hope for good weather and an evening as fun as last year.

Since our research laboratory is a modern one, you can sign up for this event through Facebook, or by more old-fashioned means such as calling me or by sending me an e-mail. You can also leave a comment after this bloggpost that . This event is open for everyone who has worked with Erik or his associates this year, whether it was lizards, isopods or damselflies. Please inform anybody who I might have missed.

When: Tuesday June 30, 18.00
Where: Lyftvägen 10, DALBY

Day 2: Genomics of speciation

The second day at Kristineberg has mainly been devoted to the genomic basis of speciation and the genetics of postzygotic isolation. Interesting talks by Michael Nachman, Hopi Hoekstra, Axel Meyer and Dave Presgraves. In general, though, it has been a bit too much about postzygotic isolation, though, to my taste. This, however, reflects that it is a meeting that was organized by Hans Ellegren, whose main interests are in these genomic aspects of speciation and evolution.

Again, my general feeling from yesterday remains: the field of speciation have reached the phase of "normal science", where there are not that many exciting discoveries or new concepts, but rather a lot of "problem solving" and filling in of the gaps. This might not necessarily be a bad thing: when fields are too hot and fast moving, the best science is not necessarily made because people tend to jump on bandwagons and reflect very little once they are on those bandwagons.

I had an interesting lunch discussion with Trevor Price today about the role of learning in evolution, particularly the role of learned mate preferences. This was quite refreshing, since Trevor thinks learning is extremely important and underestimated in the speciation process (as I also believe). When I first brought up the issue of learned mate preferences in on of our lab-meetings about 1 1/2 years ago, I saw mainly a lot of blank faces in the room, but I am more convinced than ever that this is one of the most exciting areas of speciation research in the future (and our coming postdoc Machteld Verzijden would probably agree, I suspect). It is also a natural area where field ecologists and behavioural ecologists could make important contributions and add to a more balanced picture of the speciation process than we would have had if we only relied on genomics data from Drosophila-research.

Another general reflection of this meeting is how large resources many research groups in the US have, compared to us in Sweden. This is particularly evident when it comes to genomic studies, such as large-scale DNA-sequencing efforts, transcriptomics, "454" and microarrays. All these techniques cost a lot of money, more money than we can ever dream of getting in Sweden with the current research financing system. So how then to seriously compete with these groups?

Perhaps the correct answer is not to try to compete at all, but rather try to specialize in areas where these groups are weaker, and not be too frustrated that we do not have access to similar large-scale genomic resources. Our main strength in Lund is our ecological and experimental tradition, not primarily our skills in genomics. This is also where we have to profile and advertise ourselves in the future, as this is an area that separates from other departments. In that sense, we have to push or Linnaeus-programme CAnMOVE in the future and emphasize the strong Lund research tradition of animal movement, dispersal and migration (and the consequences thereof).

Hans Ellegren, the organizer of this meeting, actually suggested that we in Lund should organize a similar meeting about animal movement in the future, and this seems like an excellent idéa. If there is something I think has been missing at this meeting, it is the field experiments and studies on animals in their natural environments, including mate preferences in the wild and dispersal behaviours.

"The Origin of Species - 150 years later"

I am currently at the Marin Biology Research Station in Kristineberg (Fiskebäckskil) in Bohuslän att symposium in celebration of Charles Darwin. This year (2009), it is 150 years since "The Origin of Species" was published, and 200 years since Darwin was born. To celebrate the memory of Darwin, Hans Ellegren (professor of evolutionary genetics in Uppsala) and Staffan Ulfstrand (professor emeritus of animal ecology, also from Uppsala) has arranged a symposium in the beatiful archipelago on the swedish west coast. Funding for this meeting comes from The Wennergren Foundation. Unfortunately, this meeting was only open for a small group of invited people, apart from the speakers, so here is a little report from the first day.

The theme of today has been theory and genetics of speciation, with some great contributions from evolutionary theoreticians Michael Turelli (University of California, Davies) and Sergey Gavrilets (University of Knoxville, Tennesse). Turelli talked about Haldane's rule and the genetics of postzygotic isolation, and Gavrilets presented models for the tempo and mode of adaptive radiations. Although some of these topics have been presented before by these two leading theoreticians, it is always nice to get un update.

Gavrilets have apparently got a big grant from the National Science Foundation (NSF) to set up a centre for mathematical and biological synthesis in Knoxville, similar to the ecological synthesis centre in Santa Barbara and the evolutionary synthesis centre in North Carolina. Worth checking up: there will be funding opportunities for both postdocs and workshops.

More "naturalistic" talks were given by Trevor Price (University of Chicago) and Jim Mallet (London) about bird and butterfly speciation, respectively. Trevor presented some idéas and phylogenetic patterns on bird diversification in the Himalayas, which challenges the current ecological speciation paradigm, which has almost been taken a bit too much for granted based on a few well-investigated model systems such as the Galápagos finches. Mallet questioned the views by Ernst Mayr about the reality of species and argued that Darwin's view on species was more realistic than some of the views that were advocated by Mayr and other architects of the so-called "Modern Synthesis" in the 1940'ties. In particular, Mallet argued that some of their idéas about reproductive isolation evolving to protect the "genetic integrity" of species relied on naive group-selectionism.

Two swedish contributions were by Kerstin Johannesson (parallell evolution of reproductive isolation in Littorina-snails) and Anna Qvarnström (genetics of speciation in Ficedula-flycatchers). In general, I would say that this meeting has been good to get updated on the classical concepts and discussion topics, although there has not been many surprising news. In that sense, I have the feeling that perhaps the field of speciation might have reached a plateau (perhaps temporary) where it has now entered what science philosopher Thomas Kuhn would call "normal science" or "problem solving". Perhaps I am wrong, but I have the distinct feeling that we need some new idéas to focus on, as the classical allopatry-sympatry controversy seems to fade away and people loose interest. To me, the most thought-provoking talk today was the one by Trevor Price, although I do not necessarily agree with everything he had to say. In any case, his book "Speciation in birds" is highly recommendable.

Hopefully, I will be able to publish another bloggpost tomorrow about the genomic aspects of speciation, which will be discussed tomorrow. Food here is excellent, by the way.