Abstract
Swedish marine ecosystems are strongly affected by a salinity gradient and both geographically ecologically marginal. Populations are substantially impacted by extreme selection pressures and stochastic evolutionary forces (a result of isolation and population bottlenecks) and have evolved more extreme traits than usually found. On the other hand, this marginal environment might be a promotor of evolutionary novelties. A key-species of the Baltic Sea is Fucus vesiculosus, a perennial macroalgae dominating sublittoral hard bottoms. A dwarf form of this species dominating the Bottnian Bay is a separate taxon reproductively isolated from F. vesiculosus. The new species, Fucus radicans, reproduce by cloning, a unique strategy of the genus. We will investigate what keeps the two species reproductively isolated to understand the process of speciation, if the new species evolved in the Baltic (less than 8000 years ago) to assess time needed for speciation, and what is the effects on the ecosystem with a species with very little genetic diversity. These results have obvious implications for conservation of marine ecosystems of this area. One reason for this is that climate change might further reduce the genetic variation of F. radicans, a species that is already genetically poor. Another reason is that F. radicans might successively replace F. vesiculosus in other Baltic areas if cloning is promoted over sexual reproduction as salinity decreases.
Sweden