Population genetics of antarctic icefishes

Background and Objective

The Southern Ocean around the Antarctic continent is an extreme and cold environment. Its geographic, thermal and hydrographic isolation since more than 20 million years ago lead to a species-poor, but unique fish fauna that is dominated by the clade of Antarctic Icefishes (Notothenioidei). These fishes are mostly endemic and owe their success to the development of key-innovations, such as their ability to express anti-freeze glycoproteins, which prevent body fluids from freezing, and the often absence of competitors for ecological niches. Notothenioids are especically suited to study general questions related to evolution and speciation due to their isolated environment, shared ancestry and ecologcial adaptations.

A comparative analysis of the genetic diversity of ecologically distinct species from the Atlantic sector of the Southern Ocean is conducted to identify the factors regulating population structures, with special emphasis on the gene flow by pelagic larval dispersal.

Approach

Genetic analysis of the population structure and demographic history with the use of mitochondrial gene sequences and nuclear microsatellite markers.

Our Research Questions

How are populations (genetically) structured? Which factors regulate gene flow? What influence has the long pelagic larval phase of the notothenioids on their population connectivity? How do species respond to global climate change?

Results

Based on our set of highly-resolving genetic markers we could show that populations of notothenioid fishes are often more differentiated as previously anticipated. Nonetheless, short distances between populations elevate the levels of gene flow. In contrast to expectations, the prolonged pelagic larval development of notothenioids does not automatically translate into high levels of gene flow.