Experiments in eco-evolutionary biology have traditionally focused on experiments conducted in the laboratory, or in controlled semi-natural settings. However, to understand how species interact in the real world, there is a need for studies conducted in perfectly natural settings using wild populations. Such experiments are valuable for science, but often complicated and difficult to set up. A rare opportunity was presented to us when an entire lake system was intentionally rendered fishless by the State of Alaska as part of a lake restoration effort to remove an invasive species.
Alaska has a wide range of different types of freshwater systems spread across coastal temperate rainforests to boreal forests and tundra. The lakes can also vary significantly in elevation, connecting the mountains to the sea through streams flowing from alpine glacial lakes to estuaries at sea level. These habitats are rich in biodiversity and support species that have significant value to Alaskan culture and economy. In addition to being essential for aquatic wildlife, lakes support terrestrial wildlife as migration stops and breeding grounds. However, like many ecosystems, Alaskan lakes are also fragile and their ecological balance can be easily disrupted, especially by human activities.
Northern pike (Esox lucius) is a large apex predator that naturally occurs in most parts of Alaska, except south and east of the Alaska Mountain Range. Due to illegal stocking activities by humans, northern pike has spread to lake systems beyond its natural range. Recent introductions of pike in Southcentral Alaska has led to significant declines in many other fish species, including salmonids, as fish that have evolved in the absence of pike are highly susceptible to pike predation. Due to its negative environmental impacts, the northern pike is considered an invasive species. In order to prevent the spread, the Alaska Department of Fish & Game (ADFG) has taken measures to eradicate pike. In 2018, ADFG treated a lake system consisting of eight lakes in the Kenai Peninsula using rotenone. Rotenone is one of the few efficient methods for eradicating invasive fish, but requires restocking of all naturally occurring species post-treatment.
Helping with the restocking efforts presented us with a rare opportunity to study how different ecotypes of sticklebacks respond to novel environments in nature. The newly established empty lakes were set up as a large-scale natural experiment to study eco-evolutionary dynamics of wild populations in real time. Previously, experimental evolution studies have most commonly been conducted in artificial laboratory settings. Well-replicated and large-scale studies where the ancestral population is known have rarely been conducted under natural conditions in the wild. Yet, such studies are important for understanding how populations evolve in the real world.
Threespine stickleback (Gasterosteus aculeatus) is a naturally occurring species of fish in Southcentral Alaskan lakes. It has an important position in the food web and acts as a significant food source for both birds and larger predatory fish, such as salmonids. It is also an interesting model organism for research. Sticklebacks are abundant across the northern hemisphere and have shown to be extremely adaptable to different types of habitats ranging from marine environments to freshwater streams and lakes.
Being a naturally occurring fish species in Alaska, sticklebacks play a central role in supporting a healthy ecosystem and they have an important part in lake restoration.
Freshwater environments vary in many physical and biotic properties, giving rise to different ecotypes of sticklebacks. These ecotypes vary in morphology and behaviour due to different diets and predatory pressures. Limnetic sticklebacks are typically found in deeper lakes and feed on zooplankton. They are more streamlined which allows them to escape large predatory fish more efficiently. Benthic sticklebacks, on the other hand, inhabit shallower lakes with more structural complexity created by vegetation, generally feeding on invertebrates at the bottom of the lakes. This gives them a deeper body and jaw structures suited for crushing their food.
In 2019, we collected three-spined sticklebacks from eight different source populations from healthy (pike-free) lakes in the Mat-Su region and the Kenai Peninsula. Half of the source population lakes corresponded to a typical limnetic habitat and half of the lakes had the characteristics of a benthic habitat. The fish from different populations were pooled into multiple batches to create an experimental design where each of the eight empty rotenone-treated lakes received a mixture of benthic and/or limnetic sticklebacks. We also restocked a ninth lake that had been rotenoned in 2017 with sticklebacks from all source populations. A total of approximately 10000 individual fish were collected, photographed and fin clipped prior to being released into their new habitat. This will allow us to study the genomics and morphology of the ancestral populations and to track how they change over time.
Today, the project has become a large international collaboration involving over 50 scientists from 22 different research groups across 17 universities and institutions. We are divided into six different axes of research. Each year, we have multiple teams conducting fieldwork in the experimental lakes in Alaska to collect samples and data, allowing us to monitor how the populations evolve and to conduct additional experiments. Our projects have received external funding from multiple organizations, such as the Swiss National Science Foundation, the Natural Sciences and Engineering Research Council (Canada) and the National Science Foundation (USA).
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Application of environmental DNA metabarcoding for ecological tracking
in a large- scale field experiment of eco-evolutionary dynamics in Alaska, USA
2021-2022
Eco-evolutionary consequences of adaptive reversals in consumer foraging traits in nature.
2019-2020
Funding student field research.
2019 - present
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