Thursday, December 1, 2016

Lab meeting on December 6: Transcriptomics of sexual development without sex chromosomes

Two sexes, one genome: regulatory structure of sex-biased development without sexual chromosomes


Sexual dimorphism poses a challenge for genetically-minded scientists: How can animals with near-identical genomes be so strikingly different? Existing theories rely on selection for sex-linked genes, yet sexual dimorphism is present also in species that lack sexual chromosomes. How do these species induce and maintain different developmental trajectories?

I present the results of my research on the sexual development of the jewel wasp Nasonia vitripennis (Hymenoptera). Nasonia's sex is determined by the number of genome copies received by the zygote and does not show any sex-linked locus within its genome.

I compare the transcriptomes of developing male and female Nasonia in order to detect the mechanistic processes that induce sexual dimorphism throughout development. In particular, I test whether sex-specific differences are present at three molecular levels:
  1. Sub-gene, via alternative splicing
  2. Whole-gene, via differential expression
  3. Between-gene, via higher order transcript-transcript interactions
I show how splicing comprises only a minor portion of between-sex differences, whereas differential expression and sex-biased interactions complement each other and alternate in prevalence throughout development.

Finally, I reconstruct the structural organization of sex-biased developmental sub-networks and compare them to non sex-biased sub-networks. The regulatory architecture of sex-biased sub-networks shows stronger hierarchical organization and preferential integration of new genes in potentially regulatory positions.

Wednesday, November 23, 2016

"Half-time seminar" by PhD-student Beatriz Willink on colour evolution in damselflies on November 29





Posted by Erik Svensson 

As a proud advisor, I am pleased to announce that EXEB-member and my PhD-student Beatriz Willink will have her "Half-time seminar" next week. The title of Beatriz's talk is


"Colour Evolution in Damselflies"


Beatriz will present data and results, containing a mixture of field data from both temperate areas and tropical rainforests (like Guyana, where the picture above was taken), observations, behavioural experiments and phylogenetic comparative analyses on the macroevolutionary dynamics of colour evolution and its developmental changes in damselflies. 

It will thus be an integrative talk about a study system that still has a lot to offer and where many fascinationg questions remain to be answered. Beatriz talk will start at 14.30 (following a short coffee break after Gabriel Norevik's halftime seminar, which starts at 13.15 and ends at 14.15). Both halftime seminars will take place in the "Blue Hall" in the Ecology Building, and fika will be served after Gabriels talk and before Beatriz.

Time: Tuesday, November 29 at 14.30
Place: "Blue Hall", Ecology Building

Opponent on Beatriz's thesis will be Professor Stefan Andersson (Biodiversity Unit).

 Everybody should be most welcome!

Tuesday, November 22, 2016

Visit and talk by Lars Lønsmann Iversen on antagonistic coevolution and polymorphisms in beetles

 


 
 
 Posted by Erik Svensson

For next week's EXEB-meeting, we will have a visitor by a collaborator of mine from Copenhagen University (Lars Lønsmann Iversen), who will present the results of some ongoing research on diving beetle polymorphisms and antagonistic co-evolution. Time and place of meeting as usual:
 
When: Tuesday, October 29 at 10.00
Where: "Darwin" seminar room, 2nd floor Ecology Building.
 
Fika will be served!
 
About  Lars Lønsmann Iversen
 
I am a postdoctoral research fellow at the Freshwater biology laboratory at The University of Copenhagen. I have a background as a spatial ecologist and entomologist working with different aspects of community assembly in freshwater habitats. Currently, most of my work addresses community and functional trait compositions along lake to pond gradients in plant communities and freshwater invertebrates.

Can pairs of antagonistic traits create stable polymorphic populations?
 
The suction cups of male diving beetles (Dytiscidae) and the rough modifications on female beetles' elytra, is one of the few well known pair of antagonistic traits in the animal kingdom. It has been suggested that the interplay between these two traits might in some cases hold species at an evolutionary standstill, creating stable polymorphic populations. In this talk I will present some of our resent work on Swedish populations of the species Graphoderus zonatus, extending the current knowledge on the interaction between male and female antagonistic traits. By studying the male suction cup morphology along a female elytra morph frequency gradient, we are able to show that the dimorphic antagonistic trait of the female is met by a dimorphic trait of the male suction cups. Male and female morphs follow a near 1:1 relationship along the studied morph frequency gradient. But, form did not follow function of the male suction cups and there was no difference in mating abilities between the two morph types on females with rough elytra. This suggests an adaptive lag in the males counter adaptive trait to rough female elytra structure. Our results confirm that within Graphoderus zonatus populations, the occurrence of antagonistic traits is closely balanced between sexes. However, we find very little evidence of stable polymorphic populations due to sexual conflicts and in our case study, polymorphic populations might very well be a transitional stage moving toward stable monomorphic populations.

Welcome to Alfredo Rago, new postdoc in Tobias Ullers lab and in the EXEB environment
























 Posted by Erik Svensson

My aim is to understand how regulatory networks evolve to integrate genetic, developmental and environmental factors. I focus on how phenotypic evolution can be caused by changes in the interactions between groups of heterogeneous components rather than by individual genes. My methods include integrative analyses of heterogeneous high-throughput datasets based on theoretical evolutionary modelling.

I am using simulations of environmental and genetic networks to explain the evolution of phenotypic plasticity. I aim to provide a theoretical backbone for empirical studies on how environmental interactions affect the structure of developmental regulation and to understand which regulatory architectures evolve to dampen, propagate or interpret environmental inputs.

Wednesday, November 16, 2016

Lab-meeting on November 22: talk on sexual dimorphism in amphibians by Stephen De Lisle




 
































Posted by Erik Svensson

Next week's EXEB-meeting will deal with the evolutionary ecology of sexual dimorphism by new postdoc Stephen De Lisle, who recently defended his PhD at Toronto University in Canada, under the supervision of Prof. Locke Rowe. Stephen has worked with amphibians, particularly newts, using a combination of experiments in mesocosms on single species, and phylogenetic comparative methods of amphibian diversification. An Abstract is appended below.

Time: Tuesday, November 22, 10.00
Place: "Darwin", 2nd floor, Ecology Building


   Ecological Aspects of Sexual Dimorphism

    Abstract:

Sexual dimorphism represents a striking source of diversity in nature, and much of this diversity cannot be fully explained by the direct effects of sexual selection.  This talk focuses on empirically testing and conceptually unifying some of the non-exclusive adaptive causes of sexual dimorphismFirst, I present evidence from a newt indicating significant ecological sexual dimorphism and a possible role for at least some direct ecological causal component of dimorphism. I propose a framework for demonstrating an ecological cause of sexual dimorphism, via character displacement between the sexes, and marshal the first direct evidence in support of this hypothesis. I expand this program to examine how competition-driven disruptive selection, ecological sexual dimorphism and speciation interact during the early stages of adaptive radiation in newts.  These analyses suggest clade-wide character displacement between the sexes, and that evolution of ecological sexual dimorphism may play a key role in niche divergence among nascent species. Finally, I extend the test of dimorphism’s role in diversification to a higher level of organization, across Amphibians. I show that the evolution of sexual dimorphism is and has been a key driver of amphibian diversification by increasing speciation rates and reducing extinction.  These results suggest the novel hypothesis that sexual dimorphism may promote diversification by allowing lineages to exploit sex-specific ecological opportunity. The general conclusions are that sexual dimorphism can have significant ecological impact and even direct ecological causes, and contra traditional views, the evolution of sexual dimorphism in ecologically important traits can have important positive impacts on adaptive diversification.










Welcome Stephen De Lisle - new postdoc!




Posted by Erik Svensson 

I am pleased to introduce my new postdoc Stephen De Lisle, who recently defended his postdoc at University of Toronto, under the supervision of Prof. Locke Rowe. Stephen has a strong experimental evolutionary ecology background, complemented with skills in phylogenetic comparative methods and hence will fit well in to overall research profile of both my lab and the EXEB-environment in general. Stephen will stay in Lund for at least two years from now on, thanks to a large international collaborative grant that Tobias Uller obtained together with me, Charlie Cornwallis and Per Lundberg. Stephen will present some of his thesis research on next year's EXEB-meeting (Tuesday, November 22), which will follow in a separate blogpost. 

About Stephen's research, in his own words:

I am an evolutionary ecologist interested in understanding the adaptive origins of phenotypic diversity. Although my interests are broad, much of my research has focused on testing non-traditional models of sexual dimorphism and understanding how the evolution of such ‘ecological’ sexual dimorphisms may or may not influence the structure of ecological communities and the dynamics of evolutionary radiation.  I do this using a combination of experimental and comparative approached that bridge community ecology, microevolution, and macroevolution. 

Tuesday, November 8, 2016

Visit and talk on colour evolution in Hawaiian damselflies by Jonathan Brown on November 15 2016
















Posted   by Erik Svensson


As for next week's EXEB-meeting, we will have a visitor from outside who will give a small and informal research presentation: Jonathan M. (Jackie) Brown, GrinnellCollege, Iowa, USA. See title and Abstract below. You can also check his website for information about his research on various species of arthropods.

Jackie’s research explores the evolution of ecological interactions in arthropods. He is particularly interested in how changes in these interactions are associated with the formation of new species. Study taxa have included phoretic mites and their beetle hosts, herbivorous moths and flies and their host plants and enemies, and damselflies and their biotic and abiotic environments.  Ongoing projects include:  (1) the evolution of host plant association in Hawaiian tephritids; (2) the evolution of body color and color dimorphisms in Hawaiian damselflies; and (3) the evolution of unicoloniality in North American Formica ant species. Jackie has also been the director of Grinnell’s ConardEnvironmental Research Area, where he has integrated long-term research on fire effects in prairie and woodland ecosystems into undergraduate biology classes.   

Jackie will be in Lund the whole next week (November 14-18), meaning that there is plenty of time to meet and interact with him and discuss your and his research. We also plan to go out for beers on Tuesday evening (November 15). Please contact me (erik.svensson@biol.lu.se) if you are interested in participating or want to set up a meeting with Jackie. 

Time of EXEB-meeting: Tuesday, November 15 at 10.00
Where: "Darwin" seminar room, 2nd floor (Ecology Building)




Evolution of body color and color dimorphisms in Hawaiian damselflies: is there more to color than meets the eye?

Sexual dimorphism in color is common in insects, but some species also display sex-limited dimorphism.  Female-limited dimorphisms in damselflies are most often attributed to sexual interactions, i.e., negative frequency-dependent selection by males targeting the more common female morph.  In contrast, my collaborator Idelle Cooper has proposed that ecological selection, rather than sexual conflict in mating rate, explains female dimorphism in an endemic Hawaiian damselfly (Megalagrion calliphya). Pigments -- here the ommochromes that produce red body color -- can have non-visual functions as well, for example as antioxidants that protect against the oxidative stress produced by exposure to UV radiation.  We are now testing this ecological selection hypothesis across the Megalagrion radiation, which exhibits high interspecific variation in body color, in sexual dimorphism, and in the presence of female dimorphism. Our ongoing studies  (1) identify how body color is correlated with abiotic habitat variables, particularly exposure to solar radiation, during the evolution of species across the archipelago; (2) test whether variation in sexual interactions can explain the habitat/color correlations; (3) connect color with survivorship in different habitats; and (4) test pigment function as an antioxidant.  Early results suggest that the primary function of body color is not visual.