This blog post is by MSU postdoc Murielle Ålund.
It all started with a-real life tetris game: trying to fit six gigantic coolers full of field gears, luggage, two kids and three adults into what was going to be our field car. And yet Greg Byford (Boughman Lab Research Technologist) had asked the rental agency for the biggest car they had!
Once finally on the road, as the amazing Icelandic landscapes were unfolding at each turn, I remember thinking that the trip – (and the postdoc position and the big move oversea with my family)- were already worth it, no matter how field work would go. And Iceland did not disappoint! It was such an amazing experience to spend almost six weeks in this beautiful country and to learn about Icelandic culture and fish.
Yes, the fish! I should probably have started with them, this is not a travel blog after all! The reason I got to visit such amazing places is that we are studying Threespine sticklebacks (Gasterosteus aculeatus) and how they adapt to their local environments in the Artic, a project led by Dr Janette Boughman. These tiny fish are impressive in their ability to colonize new habitats and adapt to very different environmental conditions all over the Northern hemisphere. They are very well known for their ability to repeatedly invade freshwater bodies from an original marine morph, which comes with drastic changes associated with the differences in salinity, food and predators. As Icelandic glaciers have been retreating for thousands of years and continue to do so at an accelerated rate (with a current estimated yearly surface loss of 0.2%)1, new lakes are continuously formed that can eventually be colonized by different populations of fish.
These glacial lakes are fed by constantly melting ice, and are thus extremely turbid, so much so that you can see the difference in color by looking at satellite images of the area! Once you have lost a trap in one of these lakes and realize that you cannot even see your own fingers in the water (making for an interesting time trying to find said trap by feeling it with your feet), you start wondering how sticklebacks can find food, avoid predators and choose a mating partner in these conditions!!!
This brings me to the main goals of our project: studying how sticklebacks adapt to widely different environments in these harsh and rapidly changing climates. We are specifically interested in the evolution of sensory systems, the idea being that other senses might compensate for the extreme low visibility of the turbid waters. To test that, we are collecting fish from glacial lakes, spring-fed lakes (these are very clear lakes) and from the sea and comparing their responses to visual and olfactory cues in a controlled behavioral experiment. We are then sampling and measuring their eyes, noses, lateral lines and comparing the different parts of their brains, to get a complete overview of their sensory systems and how developed their different senses are. In addition to being able to compare fish from lakes of different turbidity, we are also hoping to reconstruct a timeline of adaptation to these different habitats, as these lakes were formed anything in-between ten thousand and just hundred years ago, and have thus variable and known (max) colonization times. This will allow us to get an idea of the rate of evolution of sensory systems in sticklebacks.
This is a highly collaborative project. As I write, our amazing Icelandic team is still in the lab and in the field collecting fish and running trials. This includes our talented local technician Sven Wargenau from Hólar University, Julian Ohl (studying in Reykjavík for a Master’s degree in Environment and Natural Resources), the Boughman Lab’s brand new PhD student Brielle Dominguez and a visiting PhD student from Uppsala University: Javier Vargas Calle, specialist in gut microbiomes. Back here at MSU, Greg and I are starting to process some of the 1200 fish we already brought back and sending brain samples to the Hofmann Lab in Texas and eye samples to the Stenkamp Lab in Idaho, while the behavioral experiments are overseen by Dr. Jason Keagy at university of Illinois. To hear more about this project, come and listen to my talk at the BEACON congress next week!
That was for the tale of scales, ice and volcanoes. But the feathers you will ask? That would be enough for another full blog post… First let me say that the feathers were everywhere in Iceland, and bird watching there was amazingly easy: you can see rare species from your hot tub! But more seriously, my background is in studying speciation in birds, specifically two species of Eurasian passerines, collared and pied flycatchers (Ficedula albicollis and F. hypoleuca), that hybridize on a (much smaller) island in Sweden: Öland. During my PhD, I studied the consequences of hybridization for these two species and was particularly interested in their reproduction, and how sexual selection and fertility are affected by mating between different species.
My work involved quite a bit of fieldwork, catching, measuring and ringmarking thousands of young and adult birds, and collecting sperm samples and analysing them under the microscope directly in the forest. I first looked at what makes a male successful at siring as many chicks as possible in his nest and found that in collared flycatchers, sperm size matters, but differently depending on how “sexy” the males are: males with relatively small ornaments (white forehead patches) benefit from having long sperm, and vice-versa (coming out soon in Behavioural Ecology!2). I also found that hybridizing is really bad for these birds, as hybrids seem to be mostly sterile: the females lay empty eggs and the males do not manage to produce any functional sperm3. Since one of the species is pushed away from good territories by the other one, the females do not always really have a choice, and are sometimes constrained to mate with a male of the “wrong” species to secure a territory and food for their offspring. In a collaboration with a team at the Natural History Museum of Oslo, I found that females can still mostly avoid producing costly hybrids by seeking extra-pair copulations with males of their own species, and biasing against the sperm of the “unwanted” male inside their reproductive tract, so that it has fewer chances to fertilize their eggs4.
I find it fascinating that interactions between eggs, sperm, ovarian and seminal fluids can all influence the outcome of competition for fertilization and want to study this less understood phase of sexual selection in the future. Check my website for updates on this and more stories about birds, fish, cool behaviors and fascinating evolution!
Work cited:
1: https://notendur.hi.is/oi/icelandic_glaciers.htm
2: Ålund, M., Persson Schmiterlöw, S., McFarlane, S.E. and Qvarnström, A., 2018 Optimal sperm length for high siring success depends on forehead patch size in collared flycatchers, Behavioral Ecology, accepted
3: Ålund, M., Immler, S., Rice, A. M. & Qvarnstrom, A. 2013 Low fertility of wild hybrid male flycatchers despite recent divergence. Biol. Lett. 9:3, 20130169. (doi:10.1098/rsbl.2013.0169)
4: Cramer E.R.A. and Ålund†, M., McFarlane, S. E., Johnsen, A. and Qvarnström, A., 2016 Females discriminate against heterospecific sperm in a natural hybrid zone, Evolution 70 (8), 1844-1855. (doi: 10.1111/evo.12986)
