Lab meeting 18 December - change of plans

Posted for Anders

Unfortunately Per Peetz Nielsen has to stay at home with a sick daughter tomorrow. Instead Anders will show some recent results on sex differences in learning capacity in the great tit (just like in Swedish school kids females are better). During this talk you will also eat some coffee bread. After this we will stroll down to the bird rooms in Biology house D. Here you will be able to test your spatial memory capacity against the marsh tits.

Lab meeting 18 December: meet Per Peetz Nielsen

Posted for Anders

For the last lab meeting of 2012, we will meet Per Peetz Nielsen. Per is keen to meet people interested in animal behaviour in Lund and he will give a small presentation called “From working rats to swimming pigs and all the way to high tech dairy cows!” 

Anders will bring coffee and coffee bread.

There is currently a vivid debate in Swedish media about the welfare of our domesticated animals. Come and meet someone who tries to do something about this. Per Peetz Nielsen is an ethologist who graduated with a PhD at the Swedish University of Agricultural Science in 2008. He took his BSc in animal science from the Royal Danish University of Veterinary and Agricultural Sciences and a MSc in Applied Animal Behavior and Animal Welfare from the University of Edinburgh. Per has worked with how different management routines and environmental designs affect dairy cows' behavior and production, especially how different management routines affect dairy calves feeding behaviour and welfare in intensive systems. Recently Per has started working with how automatically registered data can be used to detect problems with the cows’ health and welfare. This also includes developing new techniques for automatic registration of behaviour in the barn and on pasture. Per is currently supporting several networks and authorities with information on dairy cows' behaviour and welfare on a national and international level regarding animal welfare legislations.  

Anna Runemark receives postdoctoral research grant from the Swedish Research Council

It is with great pleasure and happiness that we note that Anna Runemark, who defended her PhD-student in May earlier this year, has received a prestiguous postdoctoral grant from The Swedish Research Council (VR). Congratulations Anna! This requires celebration with some sparkling wine at tomorrow's lab-meeting (December 11 at 10.30). The new postdoctoral grant system means that Anna will be employed at the Biology Department in Lund, being part of our lab, but will work abroad at the University of Oslo (Norway) for two of the coming three years. She will then perform research on the genomic consequences of homoploid hybridization among Passer-sparrows in southern Europe. 

Anna's achievement is well-deserved and impressive, particularly in the light of the severe competition for such grants (23 % success rate). To my knowledge, Anna was the only evolutionary biologist this year who got such a postdoc among the natural sciences in Sweden. Anna's achievement is hers, and hers only, but as a former PhD-advisor I do of course take some pride too, and takes the opportunity to boost my already big ego a bit further. I am glad that Anna keeps up my good statistics in terms of former PhD-students who get VR-postdocs: She is number five, out of five in total, resulting in a 100 % success rate (future students in this lab should take it as an encouragement and not feel stressed about it, I hope). 

We also have several other reasons to celebrate tomorrow: our postdoc Maren Wellenreuther got a "Junior Researcher" grant from VR earlier in November this year, and I myself also got a four-year grant from the same agency. Further, Jessica Abbott recently got 380 000 SEK for  buying equipment to the fly lab, and Maren got 100 000 SEK from the "Nilsson-Ehle Foundation". All in all a very successful year for the lab members in terms o grants, and hopefully this will continue in the near future. 

These are achievements we all should be proud of, whether we actually got a grant or not ourselves, as research is a collective enterprise and scientists do not work in isolation. One colleague's success can largely be attributed to his/her colleagues too, who have contributed to create an intellectually and scientifically stimulating research environment, and this is true whether you are a PhD-advisor, professor, lecturer, postdoc, PhD- or Master's student. 

New logo and some words about our visitor statistics and blog impact

Posted by Erik Svensson

Our blog continues to attract many outside readers, since it was first launched some years ago. We have had aobut 93 000 downloads, although all not unique ones, and although some come from automatic web searches and machines, I still think that we can safely conclude that we have had thousands of human visitors. The number of downloads is currently about 1000 per month, which is a decline from about 7000 per month, before we changed the name and adress of the blog in August 2012. However, this cost in terms of lost visitors will probably be worth it in the long term, as we have a steady increase in visitors and the blog name is now more general and less person-centred.

Interestingly, the currently most popular and visited blog post of ours is the one where our new postdoc Lesley Lancaster was introduced to the other lab-members. This blog post has 1007 visits, which makes me wonder if Lesley is more famous and more popular than a post about Richard Dawkins who is number two, with only 845 downloads? Clearly, Lesley is a more up-and-coming scientist though, than Richard Dawkins who has passed his peak a long time ago. 

I have gotten many positive comments from colleagues from outside, as well as putative postdocs and PhD-students who have expressed interest in joining this laboratory. Several have also said that the combination of  laboratory experimental evolution approaches (flatworms and Drosophila) and field experimental work on non-classical model organisms (damselflies, lizards, birds) is a powerful and attractive combination. The new logo above should hopefully capture this synthetic spirit of our research laboratory. Below, you can download the new header of our blog and use as a logo if you wish, or promote us to interested collegues. 

Labmeeting on the genomics of species divergence

Posted by: Anna Runemark

For the upcoming labmeeting we will discuss the recent Nature-paper The genomic landscape of species divergence in Ficedula flycatchers (found here) where Ellegren et al. have studied the distribution of differentiated regions across the genome. I hope that the paper will stimulate discussions both on the genomics of speciation as well as on to which extent studying differences between diverged species is informative of speciation versus of differences that accumulate following speciation.

Since this paper is a quite short read I will also send out one of Lesley’s manuscripts which she is about to submit as voluntary extra reading. The paper is testing for assortative and disassortative mating preferences in the color polymorphic side blotched lizards (Uta stansburiana). This is interesting as conflicting sources of selection on polymorphic individuals are expected in this system: negative frequency dependent  selection (females should mate disassortatively with rare males to maximize fitness) and correlational selection (females should mate  assortatively to preserve co-adapted gene complexes).  I will send out the manuscript to the labmembers tonight.

I will bring fika!

Symposium on phenotypic plasticity in Lund: November 26-27 2012

Posted by Erik Svensson

Next week there will be no lab-meeting as there will instead be an exciting international symposium in our department on the evolution of phenotypic plasticity: November 26-27 (two full days). The program looks very exciting, with some wellknown researchers and international guests. For more information, contact Johan Hollander (johan.hollander@biol.lu.se).

Also, the week after there will not be a regular lab-meeting, as the Evolutionary Ecology Unit will have its annual "Christmas Meeting" between December 4 and 5. There will be research talks, social activites and Christmas Dinner. If you are affiliated with the Evolutionary Ecology Unit and would like to participate, contact Anne Fogelberg (anne.fogelberg@biol.lu.se) or Per Lundberg (per.lundberg@biol.lu.se).

Lab meeting Tuesday November 20th

Posted by Jessica Abbott

It's my turn to host the lab meeting next week, so I thought I'd continue the trend of picking unusual papers.  One that I think sounds interesting came to my attention the other day via the Oikos blog.  It's about red colouration in leaves, and whether this functions as a warning signal to herbivorous insects.  Anti-herbivory is one theory explaining why we see bright autumn colours, although the paper itself is a study of young plants.  Anyway, I thought that the question of why plant leaves can change colour might be a good subject for some discussion and speculation.  Usual time and place.


This picture is from Paudash Lake, which is fairly close to where I grew up.  I got it from Wikimedia Commons.

Here is the Oikos post, which gives some background on the paper: https://oikosjournal.wordpress.com/2012/11/13/why-red-leaves/

The paper:

Chen & Huang (2012) Red young leaves have less mechanical defence than green young leaves.  Oikos, in press.

http://onlinelibrary.wiley.com.ludwig.lub.lu.se/doi/10.1111/j.1600-0706.2012.20852.x/pdf

Abstract:

In many plants, leaves that are young and/or old (senescent) are not green. One adaptive hypothesis proposed that leaf color change could be a warning signal reducing insect attack. If leaf coloration involves less herbivory, it remains unclear why leaves in many species are constantly green. To examine whether green leaves reduce herbivory by physical defense as an alternative to the supposed warning signal of red leaves, we conducted comparative analyses of leaf color and protective tissues of 76 woody species in spring. The protective features (trichomes, enhanced cuticle and multiple epidermis) and the distribution of red pigments within leaves were examined in both young and mature leaves. We observed that redness was more frequent in young leaves than in senescent leaves. Compared to 36 species with red young leaves, 40 species with green young leaves showed a significantly higher incidence of enhanced cuticle and trichomes in both phylogenetic and non-phylogenetic analyses. The phylogenetic analysis indicated that the multiple origins of mechanical protection were generally associated with loss of red coloration. Our finding of relatively poor mechanical protection in red young leaves provides additional evidence for the adaptive explanation of leaf color change.

Lab-meeting about developmental biology and our ongoing Drosophila-research

This coming Tuesday (November 6 2012), we will listen to an informal research presentation by our Japanese postdoc Natsu, who will tell us about her research progress on the genetics and function of Wing Interference Patterns (WIP:s) in Drosophila melanogaster. This is a collaborative project, involving Natsu, Jessica, Jostein Kjaerandsen and myself. Above, you see three of us and Yuma working in the laboratory, trying to get matings between males from inbred lines that differ in their WIP:s and wild-type females. Below that, you see some of the test vials where mate choice is taking place, in this case against black background, which is though to increase perception of the signal (WIP:s).

Time and place for lab-meeting as usual: "Argumentet" at 10.30 (Wednesday, November 6). Natsu will also tell us a little about her PhD-work on plant developmental biology, that took place in Japan, before she came to Lund for her postdoc to work on Drosophila. It should be very interesting, I hope. I also hope that Natsu can bring some unusual "fika", hopefully with Japanese touch :).

Most welcome!

Congratulations to Maren Wellenreuther for obtaining "Junior Project Grant"

The Swedish Research Council (VR) recently announced its grants decision for 2012, and I am happy to congratulate one of our lab-members and current postdoc Maren Wellenreuther, to have obtained a "Junior Project Grant" for the next four years. These highly attractive but competitive grants is one way of entering the job market and path towards a research or faculty position in Sweden. Competition was severe this year, as previous years, with only about 16 % of all applications being granted. Well done Maren! It will be exciting to follow Marens research the coming  years, which will focus on chromosomal inversions and evolutionary divergence in seaweed flies around the coasts of Scandinavia.

Last year Jessica Abbott got a similar grant, and it continues to go very well for young researchers both within our lab and in the rest of the Biology Department in Lund. I also encourage those of you who applied this year and did not get a grant (no one mentioned, but nobody forgotten), to not give up but try again next year. Competition is severe, and margins are often tight, but it is necessary to be persistent and believe in one's idéas. I, for myself, is also very happy and grateful that I got a grant this year, and I am looking forward to not have to apply for a while, but concentrate on research.

Lastly, I would like to congratulate former PhD-student Anna Runemark, who recently got one of her thesis-papers accepted in Molecular Ecology: a study on the relationship between inbreeding depression and secondary sexual character divergence in islant populations of Podarcis-lizards. I wish Anna all luck as she awaits the postdoctoral grant decisions from VR and EU/Marie Curie later this year. 

Policy regarding blog posts about lab-meetings

Posted by Erik Svensson

I have been approached by several different students and colleagues who wish to obtain e-mail updates about blog posts and lab-meetings. This is of course very nice, and our regular policy should be to welcome any new readers and have an open mind to those who might wish to attend our lab-meetings. Still, however, I think we should strive to have a "core" group that always comes (or nearly always), i. e. students and postdocs associated with Jessica, me and Anders.

E-mail updates can be provided to a maximum of 10 persons ("Blogger" does not accept more e-mail adresses). That means that we can have only 10 people at a time - if somebody new comes in - some other has to go out. I have solved this problem of limited number of e-mail adresses by removing names for those colleagues (former PhD-students) who are now abroad, working in other labs, i. e. Tom Gosden, Fabrice Eroukhmanoff and Tina Karlsson. The logic is that those who are abroad cannot (for obvious reasons) participate in our regular lab-meetings, for simple logistical reasons.

Still, we might not be able to provide e-mail alerts to all interested in participating in our lab-meetings, there are at least two other ways to get information and be able to download papers: 1/Bookmark the blog (www.exeblund.blogspot.com), and check it weekly or daily or 2/join our Facebook group ("Experimental Evolution, Ecology & Behaviour"). Both these options work, and after all, e-mail is only one way of communicating and obtaining information, and not necessarily the best one.  

Lab-meeting on Drosophila evolution: epistatic networks and thermal adaptation

Posted by Erik Svensson

There is now a lot of activity in the Drosophila-lab, with one undergraduate student, one postdoc (Natsu) and yesterday also a PRAO-student (my daughter My). Given this, Jessica and I felt it was time to have a lab-meeting focussed on some interesting new research in evolutionary biology, focussed on the Drosophila-system.

We have therefore picked two recent PNAS-papers for discussion, one more genetic and molecular (dealing with epistasis and gene regulatory networks of starvation resistance and chill coma recovery) and one more macroevolutionary, dealing with the evolution of upper thermal limits in a phylogenetic context. Both have in common a focus on thermal adaptation. You will find Abstracts here and here, and Abstracts and titles below.

In addition, we hope Natsu could bring anbd show some printout pictures of the beatiful Wing Interference Patterns (WIP:s) of Drosophila melanogaster inbred lines. This will just be a taster, however, as Natsu will give a more formal seminar later in November telling the lab-group about the ongoing work and some preliminary results.

Time: Tuesday October 23 at 10.30
Place: "Argumentet", 2nd floor

Epistasis dominates the genetic architecture of Drosophila quantitative traits              

Abstract

Epistasis—nonlinear genetic interactions between polymorphic loci—is the genetic basis of canalization and speciation, and epistatic interactions can be used to infer genetic networks affecting quantitative traits. However, the role that epistasis plays in the genetic architecture of quantitative traits is controversial. Here, we compared the genetic architecture of three Drosophila life history traits in the sequenced inbred lines of the Drosophila melanogaster Genetic Reference Panel (DGRP) and a large outbred, advanced intercross population derived from 40 DGRP lines (Flyland). We assessed allele frequency changes between pools of individuals at the extremes of the distribution for each trait in the Flyland population by deep DNA sequencing. The genetic architecture of all traits was highly polygenic in both analyses. Surprisingly, none of the SNPs associated with the traits in Flyland replicated in the DGRP and vice versa. However, the majority of these SNPs participated in at least one epistatic interaction in the DGRP. Despite apparent additive effects at largely distinct loci in the two populations, the epistatic interactions perturbed common, biologically plausible, and highly connected genetic networks. Our analysis underscores the importance of epistasis as a principal factor that determines variation for quantitative traits and provides a means to uncover genetic networks affecting these traits. Knowledge of epistatic networks will contribute to our understanding of the genetic basis of evolutionarily and clinically important traits and enhance predictive ability at an individualized level in medicine and agriculture.

Upper thermal limits of Drosophila are linked to species distributions and strongly constrained phylogenetically

Abstract

Upper thermal limits vary less than lower limits among related species of terrestrial ectotherms. This pattern may reflect weak or uniform selection on upper limits, or alternatively tight evolutionary constraints. We investigated this issue in 94 Drosophila species from diverse climates and reared in a common environment to control for plastic effects that may confound species comparisons. We found substantial variation in upper thermal limits among species, negatively correlated with annual precipitation at the central point of their distribution and also with the interaction between precipitation and maximum temperature, showing that heat resistance is an important determinant of Drosophila species distributions. Species from hot and relatively dry regions had higher resistance, whereas resistance was uncorrelated with temperature in wetter regions. Using a suite of analyses we showed that phylogenetic signal in heat resistance reflects phylogenetic inertia rather than common selection pressures. Current species distributions are therefore more likely to reflect environmental sorting of lineages rather than local adaptation. Similar to previous studies, thermal safety margins were small at low latitudes, with safety margins smallest for species occupying both humid and dry tropical environments. Thus, species from a range of environments are likely to be at risk owing to climate change. Together these findings suggest that this group of insects is unlikely to buffer global change effects through marked evolutionary changes, highlighting the importance of facilitating range shifts for maintaining biodiversity.

 

 

Open science and "Encyclopedia of Life" - competition for projects

As we all know, our research field (ecology and evolutionary biology) are becoming increasing data-driven and to an increasing extent we are also using data collected by "others" from various internet sources. One such example is our recent paper in Ecology, where we used GBIF-data from thousands of species occurrence records, including from the Swedish source "Artportalen" ("The Species Portal") to model  and understand the environmental factors behind northern range limits in two Fennoscandian demoiselle species (the genus Calopteryx). 

Increasingly, evolutionary biologists interested in organismal biology and phenotypic evolution will use phenotypic data from sources like DRYAD, as has already been used for a long time for molecular data (DNA-sequences), where GenBank is now a common source of information when constructing phylogenies for comparative purposes. Thus, researchers will not only rely on data they have collected themselves (which is often expensive and it is logistically impossible to gather more than a limited amount of data in short time), but can to an increasing extent also use data from public open databases such as GBIF.

Now, another such initiative - Encyclopedia of Life (EOL) - announces a competition for project proposals (deadline November 15). One can propose data-driven projects - a "wish list" - of what kind of data one wants and in what form, and the "best" projects will be realized. This might be an opportunity for someone in our lab (Lesley?), provided that we can come up with a good project proposal to enter this competition. Think about it at least  until November 15.  

Odonates would be an example of a group where distribution data collected from amateur naturalists should ideally be compiled and become available for research projects through open databases. Unfortunately, the odonate research community is small, full of rivalry and have an unfortunate tradition of publishing in low-impact journals. Some odonate researchers and self-appointed experts are also extremely territorial about their collected occurrence data. This type of territoriality certainly hinders scientific progress and the establishment of odonates as respectable model organisms in ecology and evolutionary biology. Science should be characterized by openness and data-sharing - not by rivalry. 

Lab meeting Oct. 9th

Posted by Jessica Abbott

It's my turn to choose the topic for our next lab meeting, and this time I thought we'd discuss a paper that's rather different than the ones we've had so far this fall.  It's called Increasingly radical claims about heredity and fitness, and is published in the journal Philosophy of Science.  As you might guess, this paper is more about ideas than empirical research, so I hope it will generate some interesting discussion.  It questions a lot of the assumptions we make as evolutionary biologists, so I'd like everyone to think about whether you agree with the arguments the author makes, and if not, then why not.

October 9th at 10:30 in Argumentet

Abstract:
On the classical account of evolution by natural selection (ENS) found in Lewontin and many subsequent authors, ENS is conceived as involving three key ingredients: phenotypic variation, fitness differences, and heredity. Through the analysis of three problem cases involving heredity, I argue that the classical conception is substantially flawed, showing that heredity is not required for selection. I consider further problems with the classical account of ENS arising from conflations between three distinct senses of the central concept of ‘fitness’ and offer an alternative to the classical conception of ENS involving the interaction of distinct evolutionary mechanisms.

Lesley Lancaster's informal research talk: Promotion and maintenance of diversity in multiple ecological/evolutionary systems

Hello! As one of the newest postdocs in the EXEB group, I will be presenting some of my past and current research at lab meeting next week, on Tuesday Oct. 2 at 10:30, in the Argumentet, 2nd floor, Ecology Building.

If I can identify a common thread in my rather eclectic research background, it is a fascination with the processes maintaining and promoting biological diversity.

1. For my dissertation research, I considered adaptations that contribute to the maintenance of phenotypic diversity (in the form of stable polymorphisms) within populations. My research was conducted in the side-blotched lizard system (Uta stansburiana), under Barry Sinervo at UC Santa Cruz:



Polymorphic phenotypes ("morphs") tend to involve multiple, often unlinked traits that are differentiated on more than one axis (e.g., alternative mating, foraging, antipredator, and dispersal strategies). These alternative strategies, when present, are advantageous because they increase the niche breadth of the population. However, this advantage is potentially opposed by correlational selection (multivariate disruptive selection favoring alternative combinations of traits), which can impose a recombinational genetic load, lowering the fitness of the population.

Part of my research focused on identifying facultative maternal effect mechanisms which induce adaptive traits in offspring in a context-dependent manner, thus resolving correlational selection pressures and promoting phenoypic and genetic diversity within the population. (Lancaster et al. 2007, Ecology Letters; Lancaster et al. 2010, Evolution)


2. For my first postdoctoral research project at NCEAS, I examined factors promoting and maintaining species diversity in the California flora.

With Emma Goldberg and Rick Ree, I examined the role of the threatened and unique habitat of chaparral in promoting species diversification within two key California shrubs, Arctostaphylos and Ceanothus. These genera inhabit mesic, forest habitats in California as well as the dynamic, fire- and flood-prone, nutrient-poor, and arid chaparral habitats. Our study also piloted Emma's GeoSSE method for phylogenetic estimation of range shifts and habitat-dependent diversification. (Goldberg et al. 2011, Sys. Biol.)

Ceanothus

Arctostaphylos

With Kathleen Kay, I examined the historical factors of speciation, extinction, and migration that have contributed to the California Floristic Province's status as a biodiversity hotspot. We also examined classical hypotheses for California's diversity, which are: 1) its Mediterranean climate, and 2) its location at a broad ecotone between two Tertiary geofloras (Raven and Axelrod 1978). (Lancaster and Kay, accepted with revisions, Evolution)




3. For my work at Lund University, I will be studying adaptation at range limits in the polymorphic blue-tailed damselfly, Ischnura elegans. Range limits are thought to be maintained by a combination of gene flow and trade-offs: adaptations to extreme conditions at range limits are often in trade-off with traits that are more advantageous towards the center of the range. Gene flow from the center of the range prevents organisms at the edges from maximizing their fitness and adapting further to more extreme conditions (beyond the stable limits). Under conditions of climate change, environmental conditions ancestrally characterizing the center of the range are expected to shift towards the edges, such that range expansion is possible. We will look for the genetic and phenotypic signatures of expanding ranges, partially focusing on changes in genetic and phenotypic diversity and thermal adaptations to extremes of heat and cold. This work is largely to be carried out, but I will present some preliminary results on how sex, developmental phase, and polymorphism explain individual variation in response to extreme heat and cold within non-range-limit populations. These results suggest possible demographic changes under changing climates and at range limits.



For more information about each of these studies, and to access the manuscripts cited here, please visit my research website: http://www.nceas.ucsb.edu/~lancaster/Welcome.html.

Thanks for coming!!

Genomic basis of adaptation and linkage in sticklebacks

Posted by Anna Runemark

Recently there has come out some interesting papers on the genomic basis of adaptation, linkage and recombination in sticklebacks, and I suggest that we read one of these papers and one a bit older review on linkage for this labmeeting, Jones et al. 2012 in Nature, found here and Slatkin 2008 in Nature Reviews Genetics found here, please find the abstracts posted below. Although I don’t dare to suggest more reading I would also recommend just looking at Figs. 2-3 on page 2856 in a nice paper by Roesti et al. 2012 in Molecular Ecology (found here) which shows how reduced recombination rate at centromeres result in chromosome centre biased divergence. If anyone is interested in more extra reading there is also a paper on LD in sticklebacks by Hohenlohe et al. 2012 in Phil Trans (found here) which might also be of interest for extra reading.

I’m hoping for good discussions on the implications of these findings for our expectations of adaptation in nature, and I will bring fika to hopefully stimulate such discussions.

 

The genomic basis of adaptive evolution in threespine sticklebacks

Marine stickleback fish have colonized and adapted to thousands of streams and lakes formed since the last ice age, providing an exceptional opportunity to characterize genomic mechanisms underlying repeated ecological adaptation in nature. Here we develop a high-quality reference genome assembly for threespine sticklebacks. By sequencing the genomes of twenty additional individuals from a global set of marine and freshwater populations, we identify a genome-wide set of loci that are consistently associated with marine–freshwater divergence. Our results indicate that reuse of globally shared standing genetic variation, including chromosomal inversions, has an important role in repeated evolution of distinct marine and freshwater sticklebacks, and in the maintenance of divergent ecotypes during early stages of reproductive isolation. Both coding and regulatory changes occur in the set of loci underlying marine– freshwater evolution, but regulatory changes appear to predominate in this well known example of repeated adaptive

evolution in nature.

Linkage disequilibrium —understanding the evolutionary past and mapping the medical future

Linkage disequilibrium — the nonrandom association of alleles at different loci — is a sensitive indicator of the population genetic forces that structure a genome. Because of the explosive growth of methods for assessing genetic variation at a fine scale, evolutionary biologists and human geneticists are increasingly exploiting linkage disequilibrium in order to understand past evolutionary and demographic events, to map genes that are associated with quantitative characters and inherited diseases, and to understand the joint evolution of linked sets of genes. This article introduces linkage disequilibrium, reviews the population genetic processes that affect it and describes some of its uses. At present, linkage disequilibrium is used much more extensively in the study of humans than in non-humans, but that is changing as technological advances make extensive genomic studies feasible in other species.

On the evolution of large insects

Posted by Erik Svensson

Our last lab-meeting contained an interesting discussion about the evolutionary significance of large body size in insects, stimulated by the excellent talk by Yuma Takahashi about his ongoing research on Ischnura-damselflies. I thought we should continue on the theme of body size evolution and its drivers in insects, by reading two recent papers that should hopefully be entertaining and interesting.

Both papers discuss the rise and fall of large insects, such as gigantic dragonflies during the Carboniferous Period, and the biotic and abiotic factors driving selection on both body size and wing size. Among the most discussed (but also controversial) idéas is that atmospheric oxygen levels might have been important, but predation has also been suggested to play a role.

Time and place of lab-meeting as usual: "Argumentet" (2nd floor, Ecology Building) at 10.30 on Tuesday September 18 2012. 

Below, you will find the title of the papers and Abstracts and links that should allow you to download the paper if you are on the Lund University network. You can also download them here and here. You might also be interested in the short comment on the latter paper by Steven Chown, which you can download here. 

Environmental and biotic controls on the evolutionary history of insect body size

Author(s): Clapham, ME (Clapham, Matthew E.)1; Karr, JA (Karr, Jered A.)1

Source: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA  Volume: 109   Issue: 27   Pages: 10927-10930   DOI:10.1073/pnas.1204026109   Published: JUL 3 2012

Abstract: Giant insects, with wingspans as large as 70 cm, ruled the Carboniferous and Permian skies. Gigantism has been linked to hyperoxic conditions because oxygen concentration is a key physiological control on body size, particularly in groups like flying insects that have high metabolic oxygen demands. Here we show, using a dataset of more than 10,500 fossil insect wing lengths, that size tracked atmospheric oxygen concentrations only for the first 150 Myr of insect evolution. The data are best explained by a model relating maximum size to atmospheric environmental oxygen concentration (pO(2)) until the end of the Jurassic, and then at constant sizes, independent of oxygen fluctuations, during the Cretaceous and, at a smaller size, the Cenozoic. Maximum insect size decreased even as atmospheric pO(2) rose in the Early Cretaceous following the evolution and radiation of early birds, particularly as birds acquired adaptations that allowed more agile flight. A further decrease in maximum size during the Cenozoic may relate to the evolution of bats, the Cretaceous mass extinction, or further specialization of flying birds. The decoupling of insect size and atmospheric pO(2) coincident with the radiation of birds suggests that biotic interactions, such as predation and competition, superseded oxygen as the most important constraint on maximum body size of the largest insects.

Atmospheric oxygen level and the evolution of insect body size

Harrison, JF (Harrison, Jon F.)1; Kaiser, A (Kaiser, Alexander)2; VandenBrooks, JM (VandenBrooks, John M.)1

Source: PROCEEDINGS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES  Volume: 277   Issue: 1690   Pages: 1937-1946   DOI: 10.1098/rspb.2010.0001   Published:JUL 7 2010

Abstract: Insects are small relative to vertebrates, possibly owing to limitations or costs associated with their blind-ended tracheal respiratory system. The giant insects of the late Palaeozoic occurred when atmospheric PO(2) (aPO(2)) was hyperoxic, supporting a role for oxygen in the evolution of insect body size. The paucity of the insect fossil record and the complex interactions between atmospheric oxygen level, organisms and their communities makes it impossible to definitively accept or reject the historical oxygen-size link, and multiple alternative hypotheses exist. However, a variety of recent empirical findings support a link between oxygen and insect size, including: (i) most insects develop smaller body sizes in hypoxia, and some develop and evolve larger sizes in hyperoxia; (ii) insects developmentally and evolutionarily reduce their proportional investment in the tracheal system when living in higher aPO(2), suggesting that there are significant costs associated with tracheal system structure and function; and (iii) larger insects invest more of their body in the tracheal system, potentially leading to greater effects of aPO(2) on larger insects. Together, these provide a wealth of plausible mechanisms by which tracheal oxygen delivery may be centrally involved in setting the relatively small size of insects and for hyperoxia-enabled Palaeozoic gigantism.