Single dispersal of modern humans to Eurasia

Dolne Vestonice burial 16, South Moravia, Czech Republic (Credit: Martin Frouz)

Dolne Vestonice burial 16, South Moravia, Czech Republic
(Credit: Martin Frouz)

In a typical ancient DNA study where the number of authors exceeds the number of specimens (actually, equals this time), Cosimo Posth and colleagues sequenced 35 pre-Neolithic modern humans from Europe.

By sequencing 35 mitochondrial DNA (mtDNA) genomes, Posth et al. tripled the currently available dataset of hunter-gatherers spanning in age from 35 ka (thousand years) to 7 ka, which covers most of time that hunther-gatherers were present in Europe. Continue reading

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New faces: Elin Videvall

(Elin Videvall)

(Elin Videvall)

This week we’re pleased to welcome a big group of new contributors to the blog. By way of introduction, I asked each of them to answer a few quick questions about him- or herself. —Jeremy

Who am I? Elin Videvall, PhD candidate in Evolutionary Biology

Where am I? I’m in the Molecular Ecology and Evolution Lab at Lund University, Sweden

What do I study? I study host-microbe interactions in avian systems using genomic and transcriptomic tools. In one of my projects I analyse changes in gene expression of both the avian host and its malaria parasite during an ongoing infection, and in another project I study gut microbiome composition and how it relates to fitness in ostriches.

What do I do when I am not studying? When I’m not working I like travelling, watching movies, enjoy good food and reading.

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New faces: Reid Brennan

(Reid Brennan)

(Reid Brennan)

This week we’re pleased to welcome a big group of new contributors to the blog. By way of introduction, I asked each of them to answer a few quick questions about him- or herself. —Jeremy

Who are you? Reid Brennan

Where are you? I’m a PhD candidate in Andrew Whitehead’s lab at the University of California Davis.

What do you study? My work focuses on the mechanistic basis of local adaptation to abiotic environments. I work primarily on the killifish, Fundulus heteroclitus. These fish are typically found in marine habitats, but a few populations inhabit exclusively freshwater environments. I combine physiological, transcriptomic, and genomic approaches to understand how selection has shaped phenotypes in these different salinities.

What do you do when you’re not studying it? When I’m not working I try to spend my free time enjoying the great landscape California has to offer. I like to backpack and hike as well as run, bike, and play soccer.

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How to build a mimic

Image from Wikimedia Commons, Source: Mattias Starkenberg

Image from Wikimedia Commons, Source: Mattias Starkenberg

The history of evolutionary and ecological studies on mimic species is deep and chock-full of familiar names (Bates, Darwin, Muller, Wallace are just a few). There has also been no limit on the number of jaw-droppingly gorgeous species that have been under investigation.

A new paper by Evan Twomey and colleagues presents an integrative view into the process of mimetic speciation in yet another beautiful taxon, a poison dart frog appropriately named Ranitomeya imitator.

This frog species is a mullerian mimic of four different members of Ranitomeya and is  interesting due to the multiple, independent instances of mimetic divergence that are in replicate across Peru.

Four Peruvian morphs of Ranitomeya imitator and their associated described in Figure 1 from Twomey et al (2015)

Four species of Ranitomeya dart frog and their associated Peruvian mimic as shown in Figure 1 from Twomey et al (2015)

The authors studied three transition zones in R. imitator by quantifying color phenotypes, genetic variation, and mate choice preferences. Hypothesizing that mimetic divergence is promoting reproductive isolation in these morphs, they predicted that:

  1. phenotype clines should be narrow
  2. genetic divergence among mimetic morphs should be apparent
  3. mimetic morphs should prefer to mate with their own morph

Whether or not these predictions held was dependent on which transition zone was in question, but most were contrary to expectations. While each transition zone varied in the phenotypic width, no transition zone showed any additional genetic differentiation that couldn’t be explained through isolation by distance alone. Additionally, most populations showed no mating preference for their own morph.

The authors used these results to pitch the idea of a speciation continuum among the different morph transition zones of R. imitator:

At the first stage of population divergence, only mimetic color pattern divergence is present (spotted-striped transition zone). In the second stage, clines get narrower, becoming divergent in multiple aspects of overall color pattern, and mating preferences appear among allopatric populations. Lastly, the final stage of the continuum (shown in the striped-veradero transition zone) includes narrow clines that are variable among color pattern components, preferential mating at the transition zone, and restricted gene flow.

The discovery of this continuum is still the beginning of explaining exactly how this differentiation came to be. Selection on single or multiple traits? Geographic barriers? Secondary contact? Differences in divergence time? The authors discuss these options and provide an argument for simultaneous selection on color pattern and body size that has created reproductive isolation during different time frames for each morph.

I just want to know if they need any field help.

 

Twomey, E., Vestergaard, J. S., Venegas, P. J., & Summers, K. (2016). Mimetic Divergence and the Speciation Continuum in the Mimic Poison Frog Ranitomeya imitator. The American naturalist, 187(2), 205. DOI: 10.1086/684439

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New Faces: Christine Ewers-Saucedo

Christine, catching barnacle-ridden crabs with the Skidaway Institute for Oceanography. (Christine Ewers-Saucedo)

Christine, catching barnacle-ridden crabs with the Skidaway Institute for Oceanography. (Christine Ewers-Saucedo)

This week we’re pleased to welcome a big group of new contributors to the blog. By way of introduction, I asked each of them to answer a few quick questions about him- or herself. —Jeremy

Who am I? My name is Christine Ewers-Saucedo. Originally from a small island in Germany, I moved to the United States in 2010 after receiving my Diplom in Biology at the Christian-Albrechts University of Kiel, Germany. A German Diplom is comparable to a masters degree.

Where am I? I received my PhD from the University of Georgia, and just started a postdoc position at the University of California at Davis.

What do I study? I am fascinated by the evolution of life histories, particularly larval and reproductive traits (think variation in egg size and mating system). My study system of choice are marine invertebrates, which exhibit an impressive diversity of life histories.

What do I do when I am not studying? I began playing soccer when I began my PhD. Since then, I have played almost every week, always loving the game, even though the game didn’t always love me. I also like to read historical novels (I was close to becoming an archeologist once), and all kinds of creative hands-on work, such as sewing and woodwork. Last year, my husband and I adopted the best dog in the world (sorry, Lassie and Beethoven), and every day has been more fun ever since.

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New faces: Patrícia Pečnerová

(Patrícia Pečnerová)

(Patrícia Pečnerová)

This week we’re pleased to welcome a big group of new contributors to the blog. By way of introduction, I asked each of them to answer a few quick questions about him- or herself. —Jeremy

Who are you? My name is Patrícia Pečnerová and I’m a PhD student.

Where are you? I’m doing a PhD in Stockholm, Sweden. I study at Stockholm University and my office is situated at the Swedish Museum of Natural History.

Since my first visit to the Natural History Museum Vienna, I’ve always wanted to work at a museum of natural history, and now I’m fulfilling this dream.

I’m originally from Slovakia and I’ve done my pre-graduate studies in the Czech Republic before coming to Sweden.

What do you study? My PhD research project is about using ancient DNA to trace changes of genetic diversity in the last population of the woolly mammoth before its extinction. My research is a combination of ancient DNA, next generation sequencing, bioinformatics, population and conservation genomics.

What do you do when you’re not studying it? I travel and blog about it at thejourneyjournal.com. I have a sweet tooth and I like to bake, which is a terrible combination. I try to counterbalance the high sugar income by being a Les Mills fitness instructor. In general, I’m happiest when I’m having a good book in one hand and a cup of coffee in the other.

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New faces: Kelle Freel

(Kelle Freel)

(Kelle Freel)

This week we’re pleased to welcome a big group of new contributors to the blog. By way of introduction, I asked each of them to answer a few quick questions about him- or herself. —Jeremy

Who are you? Kelle C. Freel

Where are you? I am currently living in Santa Cruz, California where I was born and raised. I attended the University of California, San Diego, and then stuck around for grad school at Scripps Institution of Oceanography. After graduating, I decided to opt for an international postdoc and studied yeast population genomics in Strasbourg, France.

What do you study? I study the phylogeny and biogeography of microbes and how distinct species fit into their ecological niche. I am interested in studying bacterial communities, and how members interact with each other as well as their environment.

What do you do when you’re not studying it? When I’m not studying, I run, cycle, and (when I’m close to an ocean) go surfing. I also love to cook, travel, and generally have adventures.

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New faces: Ethan Linck

(Ethan Linck)

(Ethan Linck)

This week we’re pleased to welcome a big group of new contributors to the blog. By way of introduction, I asked each of them to answer a few quick questions about him- or herself. —Jeremy

Who are you? Ethan Linck

Where are you? I’m a Ph.D. student at the University of Washington and Burke Museum of Natural History & Culture, in Seattle.

What do you study? I’m in John Klicka’s lab, where we’re broadly concerned with analyzing and archiving avian biodiversity using genomic data and natural history museum specimen collections. My (nascent) dissertation work is focused on the role of natural selection in driving divergence in a lineage of tropical kingfishers distributed along an elevational gradient. My more-realized research has focused on the contribution of ecology and geography in determining phylogeographic structure.

What do you do when you’re not studying it? I spend a lot of time running, climbing, and ski touring in the Cascades, compulsively reading the news, and writing (most frequently at http://beyondtheranges.wordpress.com). I’m usually in search of my next cup of coffee.

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A race to the bottom with a new card from the coevolutionary deck

I’m a sucker for a clever, amusing title, though I’ve recently read that amusing titles are cited less (see here). Alas, maybe a well placed metaphor can enliven a manuscript and also not get lost in a citation-less abyss?

In basic evolution courses, students are taught about the Red Queen Hypothesis or evolutionary “arms races.”

© Lewis Carroll Through the Looking Glass

© Lewis Carroll Through the Looking Glass

Taken from Lewis Carroll’s Through the Looking-Glass, the Red Queen says “it takes all the running you can do, to keep in the same place.” This has been used as a clever way to explain the interaction between hosts and pathogens. A parasite evolves a way to overcome a host’s defenses and the host evolves a new defense. In response, the parasite evolves a new mechanism to attack the host. And so on and so on.

Continue reading

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New faces: Bryan McLean

(Bryan McLean)

(Bryan McLean)

This week and next we’re pleased to welcome a big group of new contributors to the blog. By way of introduction, I asked each of them to answer a few quick questions about him- or herself. —Jeremy

Who are you? Bryan McLean

Where are you? PhD Candidate at University of New Mexico (Albuquerque, NM) and Predoctoral Fellow at National Museum of Natural History (Washington, DC; through March 2016)

What do you study? I study mammalian phylogeny, morphology, ecology and macroevolution. I spend large amounts of time in both the field and the (molecular) lab. I work in, conduct research in, and am in general an appreciator of natural history museums.

What do you do when you’re not studying it? When not doing those things, I’m often traveling, or exploring the great state of New Mexico, or checking items off my museum life list, or exploring the culinary universe.

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