To facilitate broad discussions about literature among members of the RCN, we have set up Slack channel at evolvingseas.slack.com. To join the channel please visit this site. The steering committee has developed a reading list for Winter/Spring 2019, with a schedule for discussions every two weeks and questions for discussion. We encourage you to discuss the papers with other participants prior to joining the larger discussion on slack. For each topic, your group should choose one person to post a summary to the Slack channel that summarizes the group’s reaction to the papers and discussion questions.

Some suggestions to forming a discussion group 1) Start a group at your home institution and meet once or twice during each two-week period (any time during the two weeks is fine) to read and discuss the papers, 2) Find colleagues on the RCN list (linked here) and discuss with them virtually before joining the larger discussion, or 3) If a participant has trouble finding enough critical mass to form a group, that participant can read the papers and discuss them with the community on Slack.

All participants can also use the thread feature in Slack to post additional questions, and react to comments or questions posed by other groups.

We encourage all participants who would like to attend one of our workshops in the next three years (Synthesis, Genomics, or Training/Integration) to participate in the discussions on the Slack channel.

Theme and rationale

For our first set of coordinated readings, we decided to focus the scale of spatial and temporal variability in the ocean, with a focus on how this variability may influence evolutionary processes. We are interested in having discussions about how adaptive change in populations may be structured in space in time, particularly in the case when gene flow is stronger than selection. Some of the readings were also designed to spark discussions about what constitutes evidence for adaptation and how we should design studies to detect adaptation. Keep in mind there are many themes that we hope to discuss in the future (e.g., evolutionary rescue, eco-evo dynamics and evolution in a community context, plasticity and epigenetics, evolutionary perspectives on conservation biology) if this first set of coordinated readings is successful.

Note that the date posted for each week below is the date we expect the discussion to be completed and summaries posted to the Slack channel.

Week 1 (Deadline for discussion January 19)

Topic - Spatial and temporal scale of environmental variation

Rationale:

The ocean is structured in space and time. There is benthic structure and pelagic structure. While benthic structure is similar to structure in terrestrial systems, there are only weak terrestrial parallels to pelagic structure which is critical to both habitat pattern and dispersal in the ocean. This week we want the RCN to think about how the scales of environmental variabilty is reflected in evolution of marine populations.

Paper 1: (Paper and Link)

Comparison of marine and terrestrial ecosystems: suggestions of an evolutionary perspective influenced by environmental variation

John H Steele, Kenneth H Brink & Beth E Scott

Paper 2:

Microgeographic adaptation and the spatial scale of evolution

Jonathan L. Richardson, Mark C. Urban, Daniel I. Bolnick & David K. Skelly

Optional Background Paper:

Why Life Histories Evolve Differently in the Sea

Richard R. Strathmann

Discussion Questions:

  1. Are marine systems less or more variable environments than terrestrial systems and how does this vary across scales?

  2. How can we link the scale of environmental variability to microgeographic adaptation in the ocean? Could other mechanisms be at play?

Week 2 (February 2):

Topic - Local adaptation (Conceptual)

Rationale:

This week we want the RCN to think about different ways we define local adaptation and come to a consensus on a definition of local adaptation that we should use as we move forward with the discussions and in the RCN.

Paper 1: (Paper and Link)

Conceptual issues in local adaptation

Tadeusz J. Kawecki & Dieter Ebert

Paper 2:

A practical guide to measuring local adaptation

François Blanquart, Oliver Kaltz, Scott L. Nuismer & Sylvain Gandon

Discussion Questions:

  1. What are the implications for how we individually define local adaptation on how we study it and what we think about the processes that drive it?

  2. What definition of local adaption should we (the RCN-ECS network) should use?

Week 3 (February 16):

Topic: Local adaptation - Case Studies

Rationale:

Many consider reciprocal transplant to be the gold standard for demonstrating local adaptation, but recently genomic data collected from different populations has been used to argue for local adaptation. This week we want the RCN to compare and contrast different approaches toward measuring local adaptation.

Paper 1: (Paper and Link)

Local adaptation along a continuous coastline: prey recruitment drives differentiation in a predatory snail

Eric Sanford & David J. Worth

Paper 2:

Genomic differentiation between temperate and tropical Australian populations of Drosophila melanogaster

Bryan Kolaczkowski, Andrew D. Kern, Alisha K. Holloway & David J. Begun

Optional Background Paper:

Discussion Questions:

  1. When does landscape genomic data present good evidence of local adaptation (without experiments)?

  2. How do the different research approaches (experimental vs. genomic) give different insights?

  3. How are the processes that drive local adaptation in the snail differ from the fly? How are they similar?

Week 4 (March 2):

Topic: Evolution of genomic architecture

Rationale:

Many marine species are characterized by high levels of gene flow. Traditional population genetic theory predicts that local adaptation will only occur when the strength of selection is greater than migration (gene flow). This week we want the RCN to consider different ways that local adaptation may evolve when the strength of selection is less than migration (gene flow) and the kinds of genomic architectures that evolve in this case.

Paper 1: (Paper and Link)

Chromosome Inversions, Local Adaptation and Speciation

Mark Kirkpatrick & Nick Barton

Paper 2:

Local Adaptation by Alleles of Small Effect

Sam Yeaman

Optional Background Paper:

The genetic theory of adaptation: a brief history

H. Allen Orr

Discussion Questions:

  1. What kind of genomic architectures to expect to evolve under high gene flow?

  2. How does genomic architecture constrain adaptation?

  3. What are the implications of different genomic architectures for our ability to study adaptation using genomic data?

Week 5 (March 16):

Topic: Dispersal

Rationale:

Many marine species have a bipartite life cycle with a pelagic phase as larvae dispersed by currents, and a benthic stage as adults. This week, we want the RCN to think about how dispersal is a key driver of marine population dynamics, and the consequences of dispersal and life history on evolutionary dynamics.

Paper 1: (Paper and Link)

Going against the flow: maintenance of alongshore variation in allele frequency in a coastal ocean

James M. Pringle & John P. Wares

Paper 2:

A Latitudal Gradient in Recruitment of Intertidal Invertebrates in NE Pacific Ocean

Sean R. Connolly, Bruce A. Menge & Joan Roughgarden

Optional Background Paper:

Ecological and Evolutionary Consequences of Linked Life-History Stages in the Sea

Dustin J.Marshall & Steven G.Morgan

Discussion Questions:

  1. How might pelagic life histories with asymmetrical dispersal, coupled with genetic correlations between larvae and adult traits, constrain or promote adaptation?

  2. When and where do we expect population genetic structure to be generated and/or maintained?

Week 6 (March 30):

Topic: Population genetics

Rationale:

Consequences of dispersal via ocean currents are potentially high variance in reproductive success and a combination of continuous and discrete genetic structure. This week we want the RCN to think about how dispersal via ocean currents may affect how we model evolutionary processes (like the coalescent), and potentially come to a consensus on how we should describe genetic structure.

Paper 1: (Paper and Link)

Coalescent Processes when the Distribution of Offspring Number among Individuals is Highly Skewed

Bjarki Eldon & John Wakeley

Paper 2:

Inferring Continuous and Discrete Population Genetic Structure Across Space

Gideon S. Bradburd, Graham M. Coop & Peter L. Ralph

Optional Background Paper:

Gene genealogies and the coalescent process

Richard R. Hudson

Discussion Questions:

  1. What are the implications for sweepstakes reproduction on how we model evolutionary processes in the ocean?

  2. Given the complexity of marine dispersal dynamics, do you think that we as a field should adopt the Bradburd et al approach for characterizing population structure?

  3. Given the potential for high variance in reproductive success, overlapping generations, and a combination of continuous and discrete population structure, how should we sample for population studies (across space and across cohorts)?

Week 7 (April 13):

Topic: Genetic Load

Rationale:

Genetic load occurs when the fitness of a genotype in its environment is less than the theoretically optimum genotype. This week we want the RCN to consider different ways that oceanographic processes may create genetic load and how this relates to the scales of environmental heterogeneity.

Paper 1: (Paper and Link)

Local Adaptation Interacts with Expansion Load during Range Expansion: Maladaptation Reduces Expansion Load

Kimberly J. Gilbert, Nathaniel P. Sharp, Amy L. Angert, Gina L. Conte, Jeremy A. Draghi, Frédéric Guillaume, Anna L. Hargreaves, Remi Matthey-Doret, & Michael C. Whitlock

Paper 2:

Phenotype-environment mismatches reduce connectivity in the sea

D. J. Marshall, K. Monro, M. Bode, M. J. Keough & S. Swearer

Optional Background Paper:

Mutation Load: The Fitness of Individuals in Populations Where Deleterious Alleles Are Abundant

Aneil F. Agrawal & Michael C. Whitlock

Discussion Questions:

  1. What’s the relationship between phenotype-environment mismatches and genetic load?

  2. How does dispersal scale and the scale of environmental heterogeneity contribute to genetic load?

Week 8 (April 27):

Topic: Balancing selection

Rationale:

Balancing selection occurs when polymorphism is maintained in a metapopulation by selection. This week we want the RCN to consider empirical and theoretical arguments for how environmental fluctuations in time can maintain polymorphism in populations.

Paper 1: (Paper and Link)

Genomic Evidence of Rapid and Stable Adaptive Oscillations over Seasonal Time Scales in Drosophila

Alan O. Bergland, Emily L. Behrman, Katherine R. O’Brien, Paul S. Schmidt & Dmitri A. Petrov

Paper 2:

Seasonally fluctuating selection can maintain polymorphism at many loci via segregation lift

Meike J. Wittmann, Alan O. Bergland, Marcus W. Feldman, Paul S. Schmidt & Dmitri A. Petrov

Discussion Questions:

  1. What constitutes strong evidence for fluctuating selection, especially if the trait under fluctuating selection is maintained by many loci with small effects?

  2. What are the benefits (or consequences) of fluctuating selection for long-term changes in the environment?

Week 9 (May 11):

Topic: Plasticity

Rationale: Plasticity is the environmentally induced production of alternate phenotypes from a given genotype (Dewitt and Scheiner 2004). While the evolution of plasticity and the effects of plasticity on the evolutionary trajectory of populations are huge topics, this week we wanted to contrast a classic and more recent study in which plasticity evolved.

Paper 1: (Paper and Link)

Genetic Assimilation of an Acquired Character

C. H. Waddington

Paper 2:

Plasticity predicts evolution in a marine alga

C. Elisa Schaum & Sinéad Collins

Optional Background Paper:

Adaptive versus non‐adaptive phenotypic plasticity and the potential for contemporary adaptation in new environments

C. K. Ghalambor, J. K. McKay, S. P. Carroll, & D. N. Reznick

Discussion Questions:

  1. Compare and contrast the two experiments. In what way are they similar and different?

  2. How does plasticity in an ancestral population determine evolutionary trajectory?

  3. Do empirical results agree or disagree with theoretical arguments?