Thursday, September 25, 2014

A second try to go the Himalayas

 Posted by Erik Svensson

Since we did not have time to discuss the paper on avian species diversity in eastern Himalaya last week, due to the fact that we enjoyed so much listening to Jessica's talk and drinking cava, we make a new try this coming week. Here is the paper by Trevor Price and his colleagues in Nature.

 For a short summary of the findings in the paper I also recomment this a brief comment about the study by Arne Mooers, in a "News & Views"-article in the same issue of Nature, which is also worth reading.

The picture above shows the national bird of Nepal, the charismatic Himalayan Monal, a pheasant that I was lucky to see myself during my bird watching tour to Nepal in 1991, along the slopes of the Anapurna Trekk. The paper interests me for personal reasons, as already as a young bird watcher in 1991, I wondered about the amazing species diversity and how it came about, before I was very knowledgeable in ecology and evolutionary theory.

Date and time: Tuesday September 30, 10.30
Where: "Argumentet", second floor (Ecology Building)

I will bring fika!

Friday, September 19, 2014

Lab-meeting on ERC-interview, PNAS-accept, niche-filling, supply and demand and avian species richness in the Himalayas

Morphological evolution.

Next week, we will listen to Jessica Abbott, giving her "practice talk" before her interview in Brussels (Belgium) for an ERC Junior Grant, which we certainly hope she will get this time (it is the second year in a row that Jessica has been shortlisted for this prestiguous grant). We should all try to give good feedback to Jessica so that her chances to get this grant are maximized!

We will also celebrate that Jessica, I, our two former postdocs Natsu and Yuma and Jostein Kjaerandsen got an accept on our paper on sexual selection on Wing Interference Patterns (WIP:s) in Drosophila melanogaster in Proc. Natl. Acad. Sci. USA. Jessica has promised to bring some nice "fika", and I will bring some "bubble" to celebrate this.

Finally, Jessica asked me to pick a short paper to discuss as well, and I have chosen a relatively recent paper on adaptive radiation, speciation and niche filling in the Himalayan bird fauna. I do this partly for personal reasons, as this is a fascinating and extremely species-rich region of the world where I travelled as a young student and avid bird watcher in 1991, just before the start of my PhD in 1992. I hope you will enjoy this beatiful paper (Abstract is provided below). You might also want to read the "News and Views" comment on this paper by Arne Mooers, which summarizes the main findings.

Date and time: Tuesday, September 23, 10.30
Where: "Argumentet", 2nd floor, Ecology Building. 
Trevor D. Price et al.

Niche filling slows the diversification of Himalayan songbirds

Nature 509, 222–225doi:10.1038/nature13272

Speciation generally involves a three-step process—range expansion, range fragmentation and the development of reproductive isolation between spatially separated populations1, 2. Speciation relies on cycling through these three steps and each may limit the rate at which new species form1, 3. We estimate phylogenetic relationships among all Himalayan songbirds to ask whether the development of reproductive isolation and ecological competition, both factors that limit range expansions4, set an ultimate limit on speciation. Based on a phylogeny for all 358 species distributed along the eastern elevational gradient, here we show that body size and shape differences evolved early in the radiation, with the elevational band occupied by a species evolving later. These results are consistent with competition for niche space limiting species accumulation5. Even the elevation dimension seems to be approaching ecological saturation, because the closest relatives both inside the assemblage and elsewhere in the Himalayas are on average separated by more than five million years, which is longer than it generally takes for reproductive isolation to be completed2, 3, 6; also, elevational distributions are well explained by resource availability, notably the abundance of arthropods, and not by differences in diversification rates in different elevational zones. Our results imply that speciation rate is ultimately set by niche filling (that is, ecological competition for resources), rather than by the rate of acquisition of reproductive isolation.

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:


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.