local adaptation

Hannes back in Chile to repeat common garden experiment!

Posted on September 28, 2025September 28, 2025 by Hannes Baumann

25. September 2025. I have been asked by quite a few people (on both hemispheres), why I had to go again to Chile, to the same place, the same marine station, to repeat the same experiment from two years ago? Did the first fail somehow? No, not at all. The first experiment yielded really intriguing data suggesting similar local adaptation patterns in southern compared to northern hemisphere silversides.

But the catch is that one year could be a coincidence. To make statistically robust inferences about the nature of local adaptation in Chilean silversides, good science simply demands another, a second independent data set of observations. Even more so, because (i) the adaptation strength here is likely subtle, and (ii) some treatments and populations were indeed less successful the first time around.

And so I'm here again. The place where I spent 6 months during my sabbatical feels wonderfully familiar - despite being thousands of miles away from home. The setting September sun pours gold over the halfmoon-shaped Coliumo Bay. Spring is in the air here, but the little beach town is still mostly void of the summer crowds. I wander through the streets, recognize the stray dogs, and many of the people in this little village say they remember me and my family from two years ago.

In the marine station, the experiment is now being set up in a different location. Inside the aquarium, which is climate-controlled and therefore more suitable. It took us two years to gain permission to move in, and I had to have custom tanks made to set it all up. Will it all be worth it?

Now time is really tight, the setup needs to be put together in just a few days, because in the low latitudes of Chile's north, the spawning season of pejerrey has already begun. Fingers crossed.

Another crazy road trip for genetic silverside research

Posted on May 18, 2022April 5, 2025 by Hannes Baumann

15 May 2022. A full, blood red moon rises over Pine Island this Sunday evening. The sight makes not just humans swoon – its pull extents underwater to all kinds of critters that take it as cue for reproduction. Critters just like the Atlantic Silverside, which once again we pursue this season to extract more of its genomic 'secrets'.

Specifically, it is this weekend that we embark on yet another ambitious road trip to find and sample spawning-ripe silversides from two very far apart places: Morehead City, North Carolina and Beverly, Massachusetts. The goal: transport spawners live from each population to UConn's Rankin Seawater lab and produce calculated crosses that will allow studying the role of genomic inversions in local adaptation.

The crew this time are Maria Akopyan and Jessica Rick from Cornell University, along with Lucas Jones and Hannes Baumann from UConn. Big shout-out to Tara Duffy for her help with beach seining at Beverly, MA. During the spawning event on May 15th, Nina Therkildsen also joined the efforts. The design and experiment are part of Jessi's successful NSF post-doctoral fellowship proposal, which the whole UConn-Cornell silverside team supports.

Click through the pictures below to retrace the steps of an exhausting but so far successful effort. Fingers crossed that all goes well during the next weeks, when the fish need to hatch, survive and grow, so they can be assessed for their traits.

[Funding] UConn Today announces new NSF-silverside project

Posted on April 21, 2018April 21, 2018 by Hannes Baumann

Click on the link or the image blow to access the article in UConn Today …

Project page | Collaborators

[Research news] New NSF grant to study silverside genes!

Posted on March 7, 2018March 8, 2018 by Hannes Baumann

We are overjoyed to announce that NSF is funding a new and collaborative research project to look at the genomic underpinning of local adaptation in the Atlantic silverside! Check out below for a first glimpse of the project website.

NSF-OCE #1756751 The genomic underpinnings of local adaptation despite gene flow along a coastal environmental cline (2018-2021)

Principal investigators

Nina Therkildsen (Cornell)

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Hannes Baumann (UConn)

Post-docs

Anna Tigano (Cornell)

Graduate students

Maria Akopyan, Callie Concannon

Collaborators

Aryn Pearce-Wilder

SYNOPSIS

Oceans are large, open habitats, where it was previously believed that the lack of obvious barriers to dispersal would result in extensive mixing, thereby preventing organisms from adapting genetically to particular habitats. It has recently become clear, however, that many marine species are subdivided into multiple populations that have evolved to thrive best under contrasting local environmental conditions. Nevertheless, we still know very little about the genomic mechanisms that enable divergent adaptations in the face of ongoing intermixing.

Learn more …

This project focuses on the Atlantic silverside (Menidia menidia), a small estuarine fish that exhibits a remarkable degree of local adaptation in growth rates and a suite of other traits tightly associated with a climatic gradient across latitudes. Decades of prior lab and field studies have made M. menidia one of the marine species for which we have the best understanding of evolutionary tradeoffs among traits and drivers of selection causing adaptive divergence. Yet, the underlying genomic basis is so far completely unknown.We will integrate whole genome sequencing data from wild fish sampled across the distribution range with breeding experiments in the laboratory to decipher these genomic underpinnings. This will provide one of the most comprehensive assessments of the genomic basis for local adaptation in the oceans to date, thereby generating insights that are urgently needed for better predictions about how species can respond to rapid environmental change. The project will provide interdisciplinary training for a postdoc as well as two graduate and several undergraduate students from underrepresented minorities. The findings will also be leveraged to develop engaging teaching and outreach materials (e.g. a video documentary and popular science articles) to promote a better understanding of ecology, evolution, and local adaptation among science students and the general public.

The project is organized into four interconnected components

Part 1 – SCAN | Characterize genome-wide patterns of differentiation among silverside populations along the cline

Part 1 examines fine-scale spatial patterns of genomic differentiation along the cline to a) characterize the connectivity landscape, b) identify genomic regions under divergent selection, and c) deduce potential drivers and targets of selection by examining how allele frequencies vary in relation to environmental factors and biogeographic features.

Part 2 – MAP | Identify genomic regions that affect key traits previously linked to local adaptation in the silverside

Part 2 maps key locally adapted traits to the genome to dissect their underlying genomic basis.

Part 3 – EVALUATE | Examine how genomic architectures underlying local adaptation vary across gene flow regimes

Part 3 integrates patterns of variation in the wild (part 1) and the mapping of traits under controlled conditions (part 2) to a) examine how genomic architectures underlying local adaptation vary across gene flow regimes and b) elucidating the potential role of chromosomal rearrangements and other tight linkage among adaptive alleles in facilitating adaptation.

Part 4 – TEST | Examine dispersal – selection dynamics over seasonal time scales

Part 4 examines dispersal – selection dynamics over seasonal time scales to a) infer how selection against migrants and their offspring maintains local adaptation despite homogenizing connectivity and b) validate candidate loci for local adaptation.