Wednesday, January 28, 2015

Eco-Evo conservation of Arctic biodiversity

The snow is falling and we just measured winds clocking at over 100km/h. Par for the course, you might think, for the region of Nunavut close to the community of Cambridge Bay where we are sampling for Arctic char. Except it’s August 23rd and we didn't really plan for a wind/snow storm. An elder with us says he’s never seen anything like it in August. We’re about 85km from the closest town, in the middle of the tundra, and our kitchen tent where we usually huddle over a warm meal just flew away. Our gear and food are scattered over the tundra and my colleague and buddy Les Harris and I are running towards the sampling tent, where we’re hoping to salvage our samples. After a few minutes, Meyok, a local Inuit who helps us with our work, comes “knocking” on the tent and tells us that they need help securing shelter for the family of an Inuit hunter who is nearby and who also lost their tent. We answer that we’ll be a minute, we just have to store our samples to make sure they don’t fly away. In typical calm, no-bullshit fashion, Meyok replies: “there will be other samples – we need you”. Les and I look at each other sheepishly and instantly feel very guilty. Of course there will be other samples. We get up and we go help.

Minutes before our kitchen tent flies away scattering our gear across the tundra. Our camp was on Victoria Island, about 85km from the community of Cambridge Bay in the Canadian Arctic, where we were sampling for Arctic char. The photo was taken on August 23rd, 2013.
Hard-won data points: The day after the storm we were back out sampling. It was a little less windy, but still very cold to be playing in the water.

This story happened in 2013. It is not a “typical day” doing fieldwork in the high Arctic, but it gives an idea of the challenges we face once in a while (nobody got hurt and the samples were fine, in case you were wondering). Why, then, would someone choose to work in such difficult conditions? Most people I talk to about my work think I’m crazy for spending my summers in the Arctic: “why didn’t you choose to work on tropical fish like any sane person would do?”. I suspect that many people who read this blog, however, totally understand the thrill of doing fieldwork in a challenging, remote environment. The question for the biologist than becomes: “why did you choose a study system where it is so difficult to get data?”.

Why the Arctic?
Andrew had a really fun post recently on how he came to work on the study systems he chose. Our paths were almost diametrically opposite, but our approach – the “follow-your-nose/serendipity” approach – is surprisingly similar. So here is my own little personal story. Be warned, however, that Andrew’s version has been tried and tested, whereas I don’t have a job yet!

It was while in the Hendry lab as a Master’s student looking for a PhD project that the idea to go study Arctic fishes took form in my head. At the time, I was working on sticklebacks on northern Vancouver Island, studying the effects of gene flow on adaptive divergence in lake–stream pairs of populations. I loved my work on sticklebacks and I really enjoyed the intellectually challenging field of evolutionary ecology, but I was longing for a project with more direct applications. Fisheries work seemed interesting for a molecular ecologist, but there was already a lot of people doing great work – how was I to carve my niche there?

At the time my buddy and fellow Hendry lab-mate Nate Millar had just moved to take a job in Inuvik (funny side story: I was to learn many years later that the job became available because the aforementioned Les Harris just vacated the position – Arctic biology is a small world!). His stories of life in the North and his pictures of the Northern Lights re-kindled a long-term interest in the Arctic regions. I looked around and found out that while there was a lot of good ecology being done on Northern Canadian fishes, there wasn’t too much done in evolutionary ecology, and especially molecular ecology. I decided to start a PhD at UBC with Rick Taylor, who was happy to supervise a project on Arctic char, but had no funds to send me to the field. Thinking back, this was an incredibly risky decision. But it paid off: it turned out the gap I perceived was real, and I soon found scientists from Fisheries and Oceans Canada (DFO) that were very happy to collaborate with a molecular ecologist on a variety of projects on Arctic char – arguably the most important fish species for the Inuit of Nunavut. I was on my way to the Arctic.

And I never looked back. There is something indescribable that I love about the tundra. The rawness of the landscapes, unobstructed by trees. This feeling of extreme vulnerability once you’re out there, far from the closest town, in one of the harshest environments on earth. Doing science in the Arctic is super fun, rewarding, and a huge pain in the neck. You can’t drive to your field sites. In fact, you may have to plan 8 months in advance for a helicopter to take you there. But then, you get to ride in a helicopter over the tundra to go to your field sites. Isn’t that the sort of thing we all dreamed of when we wanted a career in biology?

And then there are the people. Working in the field with Inuit hunters has been one of the most profound and eye-opening experiences of my life. Experiencing the harshness of the climate yourself, you can’t help being amazed at these people’s survival skills – it seems crazy enough today, so imagine back in the day when they lived in igloos!! All this with a very healthy dose of humility and respect for their environment, understanding very well that they are one mistake – or one bit of bad luck – away from death. The opportunity to keep learning from Inuit hunters and to contribute in my small way to helping preserve the environment that sustains their lifestyle is now a huge motivation for me to continue my work in Nunavut.

That was the cute personal story. That’s obviously not what I tell the funding agencies. Thankfully, there are a lot of excellent reasons – scientific and practical – to be working in the Arctic. So here are, in cute baby/werewolf/silver bullet form, the “real” reasons why I work on Arctic char in the Arctic:

The Arctic char
The Arctic char (Salvelinus alpinus) is a salmonid fish and it has the northernmost distribution of all freshwater fishes. It has been used extensively as a model system in evolutionary biology because it frequently diverges into multiple sympatric ecotypes (up to four in Lake Thingvallavatn in Iceland!) in isolated post-glacial lakes where it occurs as the only species. Most of my own work, however, focuses on the anadromous form of the species (i.e., the life-history strategy whereby fish migrate between their spawning grounds in the freshwater and their feeding grounds in the saltwater).

Yours truly with a beautiful specimen of a male Arctic char in spawning colours on Baffin Island.

In Nunavut, anadromous Arctic char has been a staple of the Inuit diet for hundreds of years and remains one of the most harvested species of wildlife. Besides being an important contributor to the modern Inuit subsistence economy, in a few Nunavut communities Arctic char is also harvested commercially. These fish are transformed locally in three government-approved fish-processing plants. The fishery generates one of the few sources of income in the territory, providing employment to many fishers and plant workers to harvest a renewable resource that gives them a culturally meaningful way of participating in the cash economy.

The effective marketing campaign “Nunavut’s Truly Wild Arctic char” has created a demand in southern markets for this luxury fish. Wild-caught Arctic char are harvested in Nunavut and in some cases flown fresh to restaurants in places like Boston and San Francisco.
Commercially harvesting a resource obviously requires sound management to ensure sustainability. All indicators currently suggest that the commercial harvest of Arctic char in Nunavut is sustainable. Still, we could use a lot more biological data on the species, and much of my work has implications for the management of the fishery (more on that later). The real threat comes from the fact that the Arctic environment that is sustaining this fishery is changing. And it’s changing very fast. 

The Arctic is warming up way faster than any other region on earth. This map shows 2010 temperatures compared to average temperatures in 1951–1980. Credit: NASA Goddard Institute for Space Studies.
The response of many temperate species to climate change has been to move their ranges poleward. For Arctic species, whose ranges are already limited by the pole, that won’t be an option. To avoid range contractions, and ultimately extinctions, Arctic species will have to adapt. To predict whether that will occur, and to manage to optimize opportunities for adaptation, will require a lot of work. Thankfully, the development of the eco-evo framework over the last several years provides us with a strong foundation on which to build our understanding of this multifaceted process. The central goal of my research has been to develop the empirical basis required to apply this framework to our understanding of the response of Arctic char to a changing climate.

Dispersal, gene flow, and eco-evo conservation biology of Arctic char
During my work in the Hendry lab, the main focus of my research was on the ecological and evolutionary consequences of gene flow. Naturally, this is what I decided to focus on when I started my work on Arctic char. Having spent a lot of time thinking about how gene flow can hinder local adaptation, but also fuel evolution in response to changing environments, I was very aware of the potential importance of this process for an anadromous species facing climate change.

Not knowing much at first about the complex migratory biology of the species, I did not foresee how challenging and rewarding this line of research was going to be. Like other anadromous salmonids, Arctic char tend to home to their natal streams and lakes to spawn. Contrary to other salmonids, however, char are not able to spend the winter in the saltwater. Remember Chemistry 101: saltwater has a lower freezing temperature than freshwater, meaning that the Arctic Ocean’s water is below zero under the ice during the winter. Char can’t deal with this (and with the increased salinity, but that’s another story) so they have to move back to freshwater every year. That doesn’t leave much time for feeding: in Cambridge Bay, for example, the rivers melt in late June and they start freezing again in September. For char, this means that it takes a couple of years to accumulate enough energy to build gonads, and thus they only spawn once every two or three years. The cool thing is that there were a few studies out there that suggested that char have an increased propensity to stray, or disperse, in the years when they do not spawn. I decided to test that with my favourite tool: genetic markers.

Collaborator Ross Tallman at DFO put at my disposition a large collection of tissue from adults collected from a dozen rivers around Cumberland Sound, Baffin Island, Nunavut. I wanted to assign these fish, for which we had information on reproductive status, to their rivers of origin. The idea was that returning adult fish – if the theory was right – were going to be a mix of fish from different rivers: some homing to their natal streams to spawn, others coming only to over-winter from other rivers. To assign the river of origin for these adult fish, then, I had the idea of going to the rearing lakes to sample pre-smolt juveniles that would better represent the genetic make-up of the local populations. So I got money from a federal agency to charter a helicopter to go sample juvenile char all around Cumberland Sound.

Seining for juvenile Arctic char in a remote lake on Baffin Island. Did I mention how bad the mosquitoes are?
Using these samples of juveniles as baselines, I genetically assigned the samples of adults to their most likely population of origin. When a fish was assigned to a population different from that where it was caught, I classified that individual as a stray, or a disperser. I could then test the hypothesis that fish that were not in spawning condition when caught going upriver were more likely to be classified as dispersers than fish that were going to spawn that year. And that’s exactly what we found using several different methods of assignment: there were quite a few spawners that dispersed, but non-spawners were significantly more likely to stray. You can read all about it in the paper we published on these results in the Canadian Journal of Fisheries and Aquatic Sciences here.

Mosaic plot of reproductive status vs. dispersal strategy in anadromous Arctic char from Baffin Island. Nonbreeding individuals are more likely to disperse than breeding individuals (dispersal, however, is not sex-biased). Adapted from Figure 3 in Moore et al. 2013 CJFAS.

The importance of this behaviour is potentially profound: this means that while dispersal is high, it does not necessarily translate into high gene flow. In that same paper, I used the empirical results we generated to parameterize a population genetic model showing that the reduction in gene flow increases the potential for local adaptation for these populations. I would also argue that this behaviour allows the species to benefit from some of the advantages of dispersal, including buffering adult mortality associated with unpredictable conditions during the upstream run.

As part of my postdoctoral work in the Bernatchez lab at Universit√© Laval, I am now working to extend the precision and reach of these results in populations of anadromous char from Victoria Island, Nunavut. To do so, we are integrating next-generation sequencing data with acoustic telemetry to really tease apart the interplay between migratory behaviour, dispersal, and gene flow. The project is ongoing, but I think we will get some very important insights from combining these two powerful tools. First, we have now been collecting tracking data from Arctic char surgically implanted with acoustic tags for two summers (we’re going back for year three next summer). Those tagged fish are being tracked by an array of moored acoustic receivers that we deployed across a 120-or-so-km-long stretch of Arctic Ocean shoreline. This is a major endeavour (funded by the Ocean Tracking Network) requiring many days out on float planes, small boats, a large research vessel, and some long quad rides on the tundra to access some of the sites. But the data we’ve been getting is amazing and will teach us a lot about the fine-scale patterns of movement that Arctic char do in the Arctic Ocean. For instance, we are finding that Arctic char move back to estuaries throughout the summer – a new finding, as we thought that char spent the whole summer out in the marine environment. What’s more, they are moving in with the spring tides (i.e., when the moon is full or new) as big groups of fish mixed from several tagging locations. This mixing of stocks throughout the summer has implications for fisheries management, but also tells us that fish from different rivers use the same habitats before homing to their river of origin in the fall. Such a detailed and mechanistic understanding of migratory behaviour offers great potential to predict how patterns of dispersal, and ultimately gene flow, will change with a changing environment and how this will influence the capacity of these populations to adapt.

Collaborator Les Harris inserting an acoustic tag in an Arctic char.
Getting ready to deploy acoustic equipment from a zodiac. Left: JS Moore; right: Jack 'Meyok' Omilgoetok.

We are currently working to combine this tracking data with next-generation sequencing technology to genotype all tracked individuals and baseline samples from most possible source populations at thousands of SNPs. Although the microsatellite data presented earlier allowed us to test our hypothesis, there was quite a bit of uncertainty still associated with population assignment. Indeed, populations of Arctic char tend to be less genetically differentiated than other salmonids, perhaps because they only very recently recolonized their current range following the glaciation, or perhaps because they experience elevated gene flow. Anyhow, previous work by colleagues in the Bernatchez lab showed that with many thousands of SNPs, one can assign individuals to their population of origin with high precision even when genetic differentiation is weak. Our plan is therefore to assign the tagged fish to their population of origin to help better interpret patterns of movement. Since we have shown extensive mixing in the marine environment, and since we catch the fish in the summer in the marine environment, location of capture might be a poor indicator of origin. Knowing the origin of tagged fish could reveal population-specific dispersal patterns that would further increase our understanding of the potential role of gene flow in redistributing genetic variation in this system. And then, there are all the cool inferences you can make about local adaptation and gene flow from genomic data.

View of the Pangnirtung Fjord, Baffin Island, Nunavut from a helicopter. Not too difficult to imagine the glacier that snaked through this landscape just a few thousands of years ago.
How does this all fit into an “eco-evolutionary” conservation biology framework? As I wrote before, I see my work to date as putting together the building blocks of such an approach used for char, and I make no claims that my work fully encompasses the eco-evo feedback loop. But the framework guides our work. One particularly helpful concept in my opinion is that of evolutionary rescue. A lot of our work thus far has been directed at understanding how gene flow and existing genetic variation will influence genetic adaptation in the face of changing environments – the third phase of evolutionary rescue. Future work will focus on demographic resilience and on how metapopulations will persist when demographically depressed after environmental degradation – the second phase of evolutionary rescue. I think that the concept of biocomplexity and how it has been applied to salmon stocks in Alaska is particularly promising to understand resilience of Arctic char stocks. We are therefore currently planning work that will help us understand how population diversity at various scales could buffer against environmental change. As always in the Arctic, however, available data is limited, and new data is difficult to acquire...

In closing

It’s probably pretty clear from this post that I have not for one minute regretted my move to do science in the Arctic. In fact, I remain committed enough to Arctic work that I spend a lot of energy volunteering for the Association of Polar Early Career Scientists. So if you want to learn more about working in the polar regions, visit our webpage. The increased difficulty of getting data, however, means that datasets are sometimes imperfect or more limited than would be possible with model organisms that live in your back yard or are easily raised in the lab. This definitely limits the breadth of the inference we can derive, and I can’t say it’s been easy to publish in high impact journals. (But then again, is it easy for anyone?) At the same time, it’s been easier to carve myself a niche of my own, and I found that I am more satisfied with my work when I sit a little closer to the “applied” side of the “pure–applied” spectrum. It’s too soon to tell whether it will be a good move career-wise, but several signs tell me it’s not an absolute disaster either. I see a lot more interest in the Arctic regions from governments and the public, and this is starting to show in the academic world, with new journals, funding opportunities, and job offers specifically targeted at folks working in the Arctic. There have definitely been a few August mornings, as I crawled out of my down sleeping bag to put on my three layers of underwear, that I’ve asked myself “what the heck am I doing here?”. But the sight of the tundra and its endless sunrises in the late summer quickly dissipates the feeling. Or at least it does after I’ve had a cup of coffee.

1 comment:

A 25-year quest for the Holy Grail of evolutionary biology

When I started my postdoc in 1998, I think it is safe to say that the Holy Grail (or maybe Rosetta Stone) for many evolutionary biologists w...