Líffræðifélag Íslands
Líffræðiráðstefnan 2015

Erindi/veggspjald / Talk/poster E100

Egg size variation and its influence on evolutionary diversification in sympatric populations of Icelandic Arctic charr (Salvelinus alpinus)

Samantha, V. Beck (1), LeBlanc, Camille (1), Katja, Räsänen (2), Zophonías, O. Jónsson (3), Skúli Skúlason (3), Bjarni, K. Kristjánsson (1)

(1) Hólar University college, Department of Aquaculture and Fish Biology, Háeyri 1, Sauðárkrókur, Iceland (2) Dept. of Aquatic Ecology, Eawag/Institute of Integrative Biology, ETH-Z (3) University of Iceland, Faculty of Life and Environmental Sciences, Askja, Sturlugata 7, Reykjavík, Iceland

Kynnir / Presenter: Samantha Victoria Beck

Tengiliður / Corresponding author: Samantha Victoria Beck (beck@holar.is)

The ability of organisms to respond to environmental conditions has never been more important at a time of unprecedented extinctions. However, the amount of phenotypic plasticity of a given character can often change throughout development. In particular, organisms seem to be more plastic during early ontogeny, likely due to the lack of natural selection. However, once exogeneous feeding occurs, the need for ecological specialisation increases and may reduce variation through natural selection. Maternal effects are one of the most important factors influencing offspring phenotype, as mothers act to increase offspring fitness under spatial and temporal heterogeneity, ultimately promoting phenotypic plasticity if these maternal effects are also transgenerational. Egg size cannot only facilitate the multigenerational transmission of maternal effects, but can also profoundly impact the development of offspring. However, it is uncertain as to how long these maternal effects can last for. It has been demonstrated that Arctic charr embryos originating from smaller eggs develop earlier than those from larger eggs, and that those charr that are smaller in early life, were also amongst the smallest 2.5 years later. What if this relationship also holds true from as early in ontogeny as the embryonic stage? Maternal effects could thus be a factor for influencing evolutionary divergence via their differential distribution of resources amongst eggs, ultimately reinforcing trophic polymorphism. This study will use six wild populations of Icelandic Arctic charr (Salvelinus alpinus), distributed along a gradient of evolutionary divergence, to further understand how variation in egg size may act as a mechanism to reinforce trophic polymorphism via developmental plasticity, and ultimately promote evolutionary diversification. The recently diverged Vatnshlidarvatn brown (VB) morph displays high variation in egg size compared to other populations of Arctic charr, including the silver Vatnshlidarvatn (VS) morph. This variation in egg size could be attributed to the shallow nature of this lake, however, the lack of egg size variation in VS suggests otherwise. This system is ideal for exploring how variation in egg size (i.e. maternal effects) could ultimately alter a species evolutionary trajectory. Variation in egg size may thus present an unstable system poised for directedness, depending upon the selective forces acting upon such plasticity. We use eight growth genes and six skeletal genes, combined with staining of feeding structures at various stages during development, to determine how egg size variation may alter the rate of ontogeny in populations of Arctic charr that differ along a gradient of evolutionary divergence. Those populations that are the least diverged are expected to show a larger variation in egg size, with earlier gene expression and earlier development of feeding structures in those smaller eggs, ultimately reinforcing evolutionary divergence if egg size mediated phenotypes become heritable.