Thursday, September 11, 2014

How new colors evolve

Lately, we've been looking at macroevolutionary patterns and asking about the origin(s) and loss(es) of interesting traits. We've had exciting discussions about the lability of these traits and the problem of identifying cause and effect. So maybe it's a good time to look in more detail at one such trait and ask how does novelty arise? This is a bit old, but attempts to offer a compelling mechanism for the evolution of new pigments in Heliconius butterflies. What do you think?

Positive selection of a duplicated UV-sensitive visual pigment coincides with wing pigment evolution in Heliconius butterflies

Authors: Adriana D. Briscoe, Seth M Bybee, Gary D. Bernard, Furong Yuan, Marilou P. Sison-Mangus, Robert D. Reed, Andrew D. Warren, Jorge Llorente-Bousquets, and Chuan-Chin Chiao




Time: Tuesday September 16th at 10:30 in Argumentet

Abstract:The butterfly Heliconius erato can see from the UV to the red part of the light spectrum with color vision proven from 440 to 640 nm. Its eye is known to contain three visual pigments, rhodopsins, produced by an 11-cis-3-hydroxyretinal chromophore together with long wavelength (LWRh), blue (BRh) and UV (UVRh1) opsins. We now find that H. erato has a second UV opsin mRNA (UVRh2)—a previously undescribed duplication of this gene among Lepidoptera. To investigate its evolutionary origin, we screened eye cDNAs from 14 butterfly species in the subfamily Heliconiinae and found both copies only among Heliconius. Phylogeny-based tests of selection indicate positive selection of UVRh2 following duplication, and some of the positively selected sites correspond to vertebrate visual pigment spectral tuning residues. Epi-microspectrophotometry reveals two UV-absorbing rhodopsins in the H. erato eye with λmax = 355 nm and 398 nm. Along with the additional UV opsin, Heliconius have also evolved 3-hydroxy-DL-kynurenine (3-OHK)-based yellow wing pigments not found in close relatives. Visual models of how butterflies perceive wing color variation indicate this has resulted in an expansion of the number of distinguishable yellow colors on Heliconius wings. Functional diversification of the UV-sensitive visual pigments may help explain why the yellow wing pigments of Heliconius are so colorful in the UV range compared to the yellow pigments of close relatives lacking the UV opsin duplicate.

Friday, September 5, 2014

Parent-offspring conflict, placentas, fish!

Continuing the trend from last week of a phylogenetic comparative study published in Nature with a colorful tree graph and a little picture of an animal next to it, I suggest That we read:



Abstract: 

The evolution of the placenta from a non-placental ancestor causes a shift of maternal investment from pre -to post-fertilization, creating a venue for parent-offspring conflicts during pregnancy 1 , 2 , 3 , 4 . Theory predicts That The Rise Of These conflicts Should drive a shift from a reliance on pre-copulatory female mate choice to polyandry in Conjunction with post-zygotic mechanisms of sexual selection 2 . This hypothesis has not yet been empirically tested. Here we apply comparative methods to test a key prediction of this hypothesis, Which Is that the evolution of placentation is Associated with Reduced pre-copulatory female mate choice. We exploit a unique quality of the fish family Poeciliidae livebearing: placentas have repeatedly evolved or been lost, creating Diversity Among pray be closely related lineages in the Presence or Absence of placentation 5 , 6 . We Show That post-zygotic maternal provisioning by means of a placenta is Associated with the Absence of bright coloration, courtship behavior and exaggerated ornamental display traits in males. Further More, we found That background of placental species have smaller bodies and longer genitalia, Which Facilitate sneak or coercive mating and, hence, circumvents female choice. Moreover, We demonstrate That post-zygotic maternal provisioning correlates with superfetation, a female reproductive adaptation That May resulted in polyandry through the formation of temporally overlapping, mixed-paternity litters. Our results suggest That The Emergence of prenatal Conflict During The evolution of the placenta correlates with a suite of phenotypic and behavioral male traits That is Associated with a Reduced reliance on pre-copulatory female mate choice.

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Sunday, August 31, 2014

EXEB shrinks - but shows overcompensatory growth: introducing new members


Posted by Erik Svensson


EXEB is our own and dynamic research environment, and as such there is (and indeed should be!) a high turnover of new and old members, and a healthy balance between inflow (newcomers) and outflow (migrants). Recently, three co-workers have left us to take up new positions.

Our most recent outgoing migrants from EXEB include Tom Gosden, who has now moved back to Australia to start a DECRA Junior Research Position, Machteld Verzijden who has moved to Aarhus University for a new postdoc and Maren Wellenreuther, who has moved to New Zeeland to commence a position as Senior Scientist at the Plant & Food Research Institute (though Maren will be affiliated to Lund part-time for the coming couple of years). We thank Tom, Machteld and Maren for their time in Lund and wish them good luck in their new positions.

Here, we also welcome some new EXEB members, which are briefly introduced below. First, we are happy to welcome Tobias Uller, who is in the process of establishing himself in Lund as a faculty member at the Biology Department, after obtaining a prestiguous fellowship from The Wallenberg Foundation. This large grant enables him to build a research group in Lund. Tobias has research interests and competence that is largely complementary to already existing expertise within EXEB, and we are looking forward to integrate both him and his forthcoming PhD-students and postdocs to our research environment. His main interests is the role of developmental plasticity in evolution, and he will work with both invertebrates (Daphnia) and reptiles (lizards) to study these important questions.

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Tobias Uller

We also welcome our new PhD-student Beatriz Willink, who is from Costa Rica and who has a research background as a herpetologist, with special interests in colour polymorphisms and sexual selection. Beatriz will work under my supervision and will focus on the macroevolutionary consequences of sexual selection and colour evolution in Coenagrionidae ("pond damselflies"), using a combination of field experiments, observations and comparative approaches. She obtained a scholarship from The World Bank to do her PhD in Lund and she has already integrated quite well in to the EXEB environment, as she has been here for one field season and several months.  

Beatriz Willink

Next, we welcome Viktor Nilsson-Örtman as a new incoming postdoc. Viktor recently obtained a postdoctoral research grant from The Swedish Research Council (VR). He will spend the first part of this three-year grant at the University of Toronto in the laboratory of Locke Rowe, before he joins Lund and EXEB. Viktor has a strong background in ecological developmental biology, working with latitudinal variation in larval growth rates of damselflies of the genus Enallagma. Viktors expertise on the larval aquatic life-stage will largely complement our ongoing research on adult odonates, and we are looking forward to bring him in to the EXEB environment. 

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                                                                      Viktor Nilsson-Örtman

Another postdoc who will join us now in late September 2014 is Katie Duryea from Dartmouth College (New Hampshire, USA), who did her PhD in the lab of Ryan Calsbeek, and who has a background as a herpetologist and Anolis-lizard biologist. Katie recently obtained a prestiguous outgoing postdoctoral fellowship from the National Science Foundation (NSF), which enables her to spend two years in Sweden and to join EXEB. Katie is interested in postcopulatory sexual selection and sperm competition, and she has a strong bioinformatic and molecular biology background, having worked also in the laboratories of Hopi Hoekstra at Harvard University and with Kelly Zammudio at Cornell University, prior to entering the PhD-programme at Dartmouth. During her postdoc in Lund, Katie will work on postcopulatory sexual selection in the polymorphic damselfly Ischnura elegans, taking advantage of soon available transcriptomic and genomic resources for this species, as well as our large outdoor cages at Stensoffa Field Station. 







Katie Duryea

Finally, we also welcome Rosa Sanchéz, who originally did her PhD at University of Vigo (Spain), and who is currently on her second postdoc in Barcelona, where she currently studies mechanisms of postzygotic isolation in mammals. However, Rosa has a solid background as an odonatologist, having worked in the laboratory of Adolfo Cordero during her PhD. Rosa will study the genomic signature of  hybridiziation between Ischnura elegans and its sister species I. graellsii in Spain. Last year, she obtained a Marie Curie Postdoctoral Fellowship from the EU, which enables her to come to Lund and join EXEB in spring 2015. 

´Rosa Sánchez

 Rosa Sanchéz


Thursday, August 28, 2014

What determines genetic diversity?

Extended data Figure 2

For next week I thought it would be nice to read a recent Nature paper about the determinants of genetic diversity in animals. Various life history traits were associated with the amount of genetic diversity (see figure), but the most important single factor seemed to be fecundity; the more babies you have, the greater your genetic diversity.


Comparative population genomics in animals uncovers the determinants of genetic diversity

J. Romiguier et al. Nature doi:10.1038/nature13685 (currently still in press)

Abstract: Genetic diversity is the amount of variation observed between DNA sequences from distinct individuals of a given species. This pivotal concept of population genetics has implications for species health, domestication, management and conservation. Levels of genetic diversity seem to vary greatly in natural populations and species, but the determinants of this variation, and particularly the relative influences of species biology and ecology versus population history, are still largely mysterious. Here we show that the diversity of a species is predictable, and is determined in the first place by its ecological strategy. We investigated the genome-wide diversity of 76 non-model animal species by sequencing the transcriptome of two to ten individuals in each species. The distribution of genetic diversity between species revealed no detectable influence of geographic range or invasive status but was accurately predicted by key species traits related to parental investment: long-lived or low-fecundity species with brooding ability were genetically less diverse than short-lived or highly fecund ones. Our analysis demonstrates the influence of long-term life-history strategies on species response to short-term environmental perturbations, a result with immediate implications for conservation policies.

Thursday, August 21, 2014

Can female demographic dominance influence evolution?

Posted by Anna Nordén

Hi all,

Jessica mentioned this paper today, and I thought it would be nice to have a modeling paper for the next lab meeting. They show, with two simulation models (intralocus sexual conflict model and environmental sex determination model), how female demographic dominance can influence evolution.

Time: Tuesday August 26th at 10:30 in Argumentet as usual. Since it is my birthday this Saturday, I will bring some extra yummy fika!
 
  


Authors: Anna M. F. Harts, Lisa E. Schwanz and Hanna Kokko
  

Friday, August 15, 2014

What can possibly be cuter than a live-bearing skink?

Pygmy blue tongue by Aaron Fenner  http://www.arkive.org/

For the next lab meeting I've chosen a paper on the evolutionary origins and consequences of viviparity in reptiles. It makes a good combo of large data sets and an unexpected result... Hope you enjoy it!





Viviparity has putatively evolved 115 times in squamates (lizards and snakes), out of only ~ 140 origins in vertebrates, and is apparently related to colder climates and other factors such as body size. Viviparity apparently evolves from oviparity via egg-retention, and such taxa may thus still have the machinery to produce thick-shelled eggs. Parity mode is also associated with variable diversification rates in some groups. We reconstruct ancestral parity modes accounting for state-dependent diversification in a large-scale phylogenetic analysis, and find strong support for an early origin of viviparity at the base of Squamata, and a complex pattern of subsequent transitions. Viviparous lineages have higher rates of speciation and extinction, and greater species turnover through time. Viviparity is associated with lower environmental and body temperatures in lizards and amphisbaenians, but not female mass. These results suggest that parity mode is a labile trait that shifts frequently in response to ecological conditions.

Wednesday, August 6, 2014

First lab-meeting this autumn: on the remarkable diversity and evolution of sex determination systems



Posted by Erik Svensson

After field work and summer break it is time to start up this autumn's lab-meetings again. And what could be more interesting than an article about the remarkable diversity and evolution of sex determination systems? A recently published essay in the journal PLoS Biology, summarizes the current knowledge and state-of-the-art of research in this area. It should hopefully be an interesting read. Below, I attach the Abstract and a link to the paper, which is Open Access and downloadable. The figure above give you a taster about the content. Enjoy!

When: Tuesday, August 12 2014, 10.30

Where: "Argumentet", 2nd floor, Ecology Building.


Sex Determination: Why So Many Ways of Doing It? 

Doris Bachtrog Judith E. Mank, Catherine L. Peichel, Mark Kirkpatrick, Sarah P. Otto, Tia-Lynn Ashman, Matthew W. Hahn, Jun Kitano,Itay Mayrose, Ray Ming, Nicolas Perrin, Laura Ross, Nicole Valenzuela, Jana C. Vamosi, The Tree of Sex Consortium 

Published: July 01, 2014DOI: 10.1371/journal.pbio.1001899 

Abstract

Sexual reproduction is an ancient feature of life on earth, and the familiar X and Y chromosomes in humans and other model species have led to the impression that sex determination mechanisms are old and conserved. In fact, males and females are determined by diverse mechanisms that evolve rapidly in many taxa. Yet this diversity in primary sex-determining signals is coupled with conserved molecular pathways that trigger male or female development. Conflicting selection on different parts of the genome and on the two sexes may drive many of these transitions, but few systems with rapid turnover of sex determination mechanisms have been rigorously studied. Here we survey our current understanding of how and why sex determination evolves in animals and plants and identify important gaps in our knowledge that present exciting research opportunities to characterize the evolutionary forces and molecular pathways underlying the evolution of sex determination.