"Somewhere in the back of every scientific mind, there likely exists this one idea, a project of special significance that always seems to be waiting. Lingering patiently for years in the shadows of seemingly more pressing tasks. But one day the opportunity is ripe and demands to be pursued. This is that kind of project."


"Enabled by the privilege of sabbatical freedom and fantastic collaborators in Chile, we can now pursue further integrative experimental work on principles of adaption across spatial climate gradients.

At its face, this project is about a replicated Common Garden Experiment with Chilean silversides (Odontesthes regia). But it is also more than that, because we use methods and approaches consistent with such work on northern hemisphere Atlantic and Pacific silversides (e.g., Conover & Present 1990; Baumann et al. 2011).

We therefore hope that our findings will lead to a higher level of integration, because for the first time we will compare adaptation patterns across three major latitudinal climate gradients on earth.

Our main question is therefore not whether Chilean silversides display local adaptation across latitudes, but what form it takes and how its strength likely scales with the strength of the underlying climate gradient."

Lecture | How will organisms adapt to global climate change? | ¿Cómo se adaptarán los organismos al cambio climático global?

Principles of local adaptation and new research in Chile

Want to learn more? Hannes talks about adaptation to climate gradients in space and time, and how this has inspired this new research project.

A budding US-Chile collaboration. Meet Profs. Mauricio Urbina and Cristian Gallardo!

Mauricio Urbina
Prof. Mauricio Urbina Foneron

From the start, Mauricio has been an ever upbeat and optimistic partner in this project. In just a short amount of time, he became the most invaluable collaborator and friend. Without his enthusiastic support, none of this could have happened.

At the Universidad de Concepción, Mauricio works within the Zoology department where he leads the Comparative Animal Physiology Lab that specializes in physiological measurements (e.g., metabolism) in a variety of invertebrate and vertebrate organisms.

Mauricio Urbina Foneron
PhD. Animal Physiology. University of Canterbury. New Zealand, 2013

Prof. Cristian Gallardo-Escárate

Dr. Cristian Gallardo-Escárate is the Director of the Interdisciplinary Center for Aquaculture Research (INCAR) and also the leader of the Laboratory of Biotechnology and Aquatic Genomics at the Center of Biotechnology of the University of Concepcion.

INCAR's facilities at the Dichato Marine Station will house our experiments, to which Cristian brings a whole new set of molecular interests and tools. Welcome to team pejerrey, Cristian!

Check out Cristians career and productivity: ORCID | Web of Science | LOOP

And the invaluable rest of the team / Equipo pejerrey

Alvaro Gallardo-Escárate (INCAR operations manager)
Lucia Soto
Lucia Soto (technician)
Rosa Obando
Rosa Obando (technician)
Don Jose (station manager)

A "Space for Time" approach

What does 'Space for Time" mean?

Many organisms have evolved local adaptations to environmental gradients across latitudes, altitudes or depth. Why wouldn't the same principles also apply for adaptation to climate change in time?

Such ‘space-for-time’ analogies promise a deep understanding how species will adapt, but they cannot tell how long this would take. Hence, they are not a panacea, but most powerful in combination with other approaches (e.g., experiments).


National Science Foundation Award Abstracts

(I) Public NSF-Award Abstract

It is virtually certain that man-made climate change is forcing Earth’s biota to adapt to the novel environments of the future. How exactly evolution accomplishes this is difficult to predict but among the most important problems for mankind to understand.

One approach is to study spatial analogues of climate change; for example, in the way temperature changes predictably with latitude. Many species have evolved adaptations to such latitudinal climate gradients, and this proposal further explores the underlying principles of local adaptation. The research focuses on the Chilean silverside (Odontesthes regia), a small short-lived forage fish that occurs along most of the South-American Pacific coast. Choosing a silverside fish is strategic, because it allows comparing and integrating any patterns into the existing empirical evidence amassed for northern hemisphere silverside species over past decades.

This project will therefore execute a large common garden experiment to rear newly fertilized offspring obtained from wild parents at four locations along the Chilean coast (20 - 43°S) at common temperatures of 10 - 22°C. Measurements of growth rate and vertebral number will show how these traits change between populations from different latitudes – which under common garden conditions are indicative of genetic differences due to local adaptation.

Then the degree of these changes can be compared to what is known about northern hemisphere silversides to derive a potentially novel relationship between gradient strength and adaptation strength. If such a relationship exists, it would allow scaling the strength of evolution to the degree of temperature change in space and – by inference - time.

PIs will conduct a seminar classes at the Universidad de Concepción, covering fish ecology and evolutionary principles of adaptation. To further build theoretical and experimental capacity, the project actively trains a Chilean graduate student to replicate the experiment and to fund an exchange visit to the PIs lab in the United States.

(II) Technical NSF-Award Abstract

How organisms adapt to climate gradients in space and time is a fundamental question for humanity and therefore a central funding objective for NSFs BIO and BIO-OCE programs.

This proposal advances understanding of two forms of local adaptation: co-gradient variation (CoGV) and counter-gradient variation (CnGV), which underlie adaptation to large-scale, latitudinal climate gradients. Both have been extensively studied in northern hemisphere silverside fishes (Atherinopsidae), but whether they also hold for southern hemisphere silversides and whether they scale with the strength of the underlying climate gradient is unknown.

The proposal will fund a comprehensive, replicated common garden experiment with the Chilean silverside Odontesthes regia; to be conducted at the Dichato Marine Station at University of Concepción. Specifically, the experiment will rear newly fertilized offspring obtained from wild founders at four locations along the Chilean coast (20 - 43°S) in triplicates at four common temperatures (10 - 22°C) to a common juvenile size.

Trait measurements of growth capacity, vertebral number, and total mercury concentration will show whether thermal reaction norms show evidence of CnGV in growth capacity and CoGV in vertebral number. These data will then be integrated into the existing empirical evidence for northern hemisphere silversides. If the latitudinal strength of thermal reaction norms varies as predicted, it will allow deriving a novel relationship between gradient strength and adaptation strength.

If such a relationship exists, it would be transformative, because it would allow scaling the strength of thermal reaction norm evolution to the degree of temperature change in space and – by inference - time. ‘Space-for-time’ analogues are one important approach to better understand how organisms and their traits may evolve under global climate change.

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Phase 1: Sabbatical research in Chile (July 2023 - April 2024)

17. Sabbatical and first year experiment ends!

The cove of Puda near Dichato to the north of Concepcion, Chile
16 April 2024. After a 9-month sabbatical stay at the University of Concepcion in Chile, Hannes returned to US soil today, full of experiences, data, and a chest full of samples of larval, juvenile, and adult Chilean silversides. Grateful to the many helpful colleagues and friends, a first year of experiments are in the bag, resulting in a number of interesting findings that await further analysis and - crucially - a second, replicate experiment in the year to follow. In other words, while the sabbatical is now over - the project of revealing co- and countergradient variation in the Chilean silverside is still very much underway. On to the next chapter!

16. Final samples taken for 2023 experiment!

On 25 December, Hannes and Zosia celebrate measuring the final fish of the experiment.
25 December 2023. Today we celebrate another important milestone of this project; the completion of the first year of common garden experiments on Chilean silversides. While not everything worked out as perfectly as hoped, we can still be proud of collecting a large amount of data that paint an encouraging picture consistent with the existence of countergradient variation in this species. We have taken more than 125 different samples of embryos, larvae, juveniles, and adults and measured almost 3000 individual fish. Now the deeper data analysis begins as well as the preparations for the second year in 2024!

15. Chilean silversides now in grow out phase

Dichato growout
Slow motion of juvenile pejerrey from the Dichato population swimming in the big growout tank

29 November 2023. We have time and space for a little extra objective, because we produced way more offspring from the Dichato population than were actually needed for our growth capacity replicates.
So we decided to give those rests a bigger home (1200l circle tank) and see, if we could grow them further out. Good thing, they are already being weaned off nauplii, and now easily switched to pelleted food.
Let's see what will happen!

14. Explaining little silversides to Chilean elementary, middle and highschool students

Left: On 24 November, Hannes talks silversides with students from an elementary school in Chillan. Right: On 14 November, Alvaro engages highschool students from Tomé to think about the purpose of the experiment.

24 November 2023. These days, the Dichato Marine station is often a destiny for school excursions from near and far. Hannes practices his (Spanish) elevator speech, while Alvaro is already a true outreach pro. It is always a great pleasure to see the faces of the children light up when they see the tiny fish larvae and juveniles.

13. A sudden, tragic loss: Don Jose, the soul of the marine station, dies unexpectedly

Don Jose
Announcement of Don Jose's sudden death.

19 November 2023. Today, the marine station and the community of Dichato lost one of it's true heroes. Don Jose Marileo, the station's manager for over 40 years unexpectedly died of a sudden, violent heart attack. He was 78 years old. Although I only knew him since July, he welcomed me with a cheerful 'Buenos dias' every single day, helped where he could, and made me feel welcome.

12. An experimental milestone ...

Final samples are measured, weighed and individually preserved (frozen)

... the first final samples!

Little bags in bigger bags in bigger bags ;-)

Intermediate samples like these ~15mm larvae from the Iquique population are preserved in 95% ethanol

11. First data begin to emerge

Steps from measuring sampled fish with Image J to estimating the growth rate distribution, here for the example Dichato 14C. Small circles = individual fish, large circle/error = mean/SD.

5 November 2023. The experiment now begins to generate data - and I'll try to keep up with the samples and digital measurements. Due to the staggered nature of the field collections and of course the vastly different development rates across temperatures (10-22C), it's super important now to keep track of the individual lines (containers, population) sampling schedule. Like in this example here, we'll soon making such growth rate calculations for other temperatures, stages, and populations. The full dataset, however, is still months away

10. Silverside bonanza in Puerto Montt

26 October 2023. On this last of our sampling trips, this time targeting the southernmost Odontesthes regia population in the coastal waters off Puerto Montt (42S), we were very fortunate to make the acquaintance of a family of truly professional pejerrey fishermen. Hannes joined the crew of four as they fished throughout the night, using an estimated 500m of gillnets deployed in circles and catching upwards of 10,000 fish (~300kg). This was the easiest of all trips to obtain 20 males and females we needed for strip-spawning. Muchas gracias a Oscar Merluza, the fisherman and his family.

9. Fish rearing can be fun!

On 17 October, Hannes and Lucia are distributing hatched larvae into replicates of equal densities
Hannes shows prospective student Pia Ampuero how to feed silverside larvae with brine shrimp nauplii

On 14 October 2023, fisherman 'Choche' deploys his gillnet in Caleta Riquelme, while the sun rises over the desert city of Iquique

8. Success in Iquique

16 October 2023. Hannes went on a second trip to find and strip-spawn Chilean silverside from the northernmost population in Iquique (20S). Thanks to the incredible help of Cristian Azocar and Miguel "El profe" Araya, the skills of local fisherman 'Choche', and the necessary dose of luck, this time around we've produced enough embryos for all temperature treatments and replicates. This means that we now indeed have the contrast we were aiming for!

Newly hatched Chilean silverside larvae

7. Hatch day - Dichato population 22C - 9dpf

5 October 2023. Newly hatched Chilean silverside larvae swimming and catching brine shrimp nauplii.

On 3 October 2023, Alvaro Gallardo is helping fishermen Mauricio Vega prepare the seine net, which is then being set via rowing across the beach and quickly retrieved. Many curious spectators!

6. Troubles in Coquimbo

3 October 2023. Unfortunately, our most recent sampling trip to the Coquimbo region produced more worrisome signs that the coastal marine nature and its phenology are seriously impacted by the particularly strong El Niño year. Fishermen in Coquimbo report having seen no silversides in months and our own attempt at gill netting fared no better. All contribute to new exceptional details, like the appearance of tropical bonitos (Sarda chiliensis chiliensis) in Coquimbo waters, which is further south than anyone can remember. We hear that local water temperatures are 2-3 degrees above averages for the season.

We finally find the small fishing village of Caleta Sierra a bit south of Coquimbo. Here, we at least encounter and sample silversides, but few and across are large size range, and most appeared nowhere close to spawning.

Still, this road trip through arid Chile had many incredible and enriching moments. Moments of awe, friendship, hospitality - and for that I will always be grateful.



5. First successful strip-spawning; Dichato population

25 September 2023. The local strip-spawning trip, together with fisherman Juan at a peaceful Monday night in Coliumo Bay. The pictures show embryos 36 hours post-fertilization (hpf) at 22C.

We have almost 100% fertilization success.

  • desert
    Flying over Chile affords stunning desert views

4. First trip to Iquique - Valuable effort. To be repeated

25 September 2023. A first sampling trip to the northern most site in Iquique (20S) saw all the highs and lows of field work. The numbers of fish, specifically pejerreyes were unusually low, and the few that we could procure from two independent sources were not in their ideal, i.e., running ripe phase yet. We found a great supporter and wonderful colleague in Prof. Miguel Araya (Arturo Prat University), took in this incredibly dry landscape, almost dystopian on one side and then so serene to the other - the blue of the Pacific. In the end, we obtained some embryos but too few to actually start an experiment with them. Most of eggs failed to get fertilized.

An annotated picture of the experimental setup on the eve of the first spawner collection.

3. "Estamos listos!"

20 September 2023. After some intense weeks of continuous building, the experimental setup is now ready.We split two two-tank recirculating systems used normally in salmon research into four individual recirculating systems, all fitted with chilling and biofiltration capacity. The 1400L tanks are being filled with ~ 1000L of water and will be able to house a maximum of 16 individual 20L buckets.

Now the fish embryos can arrive!

Fifty rearing containers of 20L each will need to be fashioned out of standard buckets

2. Assembling parts and pieces

12 August 2023. While Chile begins to see the first signs of spring and starts to feel increasingly familiar, the parts and pieces of the experiment slowly arrive and are being assembled in Dichato. More buckets, heaters, chillers - all while becoming friends and colleagues with the staff of the marine station.

Fishing boat in Dichato. In the background is the Marine Station.

1. Hannes starts sabbatical research in Chile

17 Juli 2023. Hannes just moved for 5 months to a small village called Dichato near Concepción in south-central Chile to build and then conduct a large common garden experiment on the Chilean silverside Odontesthes regia.

It's still early, disorienting days - but thanks to the ever optimistic Mauricio Urbina, the collaborator on this project, the mood is good and full of anticipation.

Phase 0: Proof of Concept (October 2022)


A two-week stint to south-central Chile showed that our planned research on Chilean silversides is feasible, and the conditions for this US-Chilean collaboration are all favorable. You can read more about this trip here: "Fishing for Silversides ... in Chile!"

Theoretical foundation of integrative common garden experiments