Kerstin Johannesson
University of Gothenburg, SwedenKerstin Johannesson is professor in marine ecology at Göteborg University, Sweden. She is an evolutionary biologist by training and deeply engaged in research on differentiation within species, particularly examples of ecotype formation where ecotypes of species gradually become reproductively isolated owing to ecological drivers. Her most intensively studied case is of a small marine snail, the periwinkle Littorina saxatilis, in which her studies have lead to a much better understanding of how this highly variable species has evolved and of the link between strong differential selection over geographical scales of meters and ecological, morphological and genetical differentiation of snail populations. She is also involved in research on speciation in macro-algae and has recently presented evidence of an intriguing speciation event taking place very recently in the Baltic Sea; the formation of a new habitat-forming macro-alga (Fucus radicans).
She is presently coordinating a 10-year research project focusing on rapid evolution of marine organisms in the recently opened marine environment, the Baltic Sea (ACME, a Swedish Linneus project).
ABSTRACTSympatric speciation — 150 years later
In the Introduction to the first edition of On the Origin of Species Darwin simply states: “Although much remains obscure, and will long remain obscure, I can entertain no doubt ... that the view ... that each species has been independently created ... is erroneous". True enough, Darwin´s own hypothesis of sympatric speciation is more intensively discussed now than ever, and there is more or less a race among leading scientists to find the first unchallengeable evidence for speciation in the presence of gene flow. Starting with Darwin´s own description of how new species are formed (a precursor of today´s sympatric speciation hypothesis), I will briefly review the main issues that have been raised against the theory of sympatric speciation, as well as the more philosophical issue of the consequence of using allopatric speciation as the “null-hypothesis of speciation".
Finally I will go through some appealing recent examples of likely cases of sympatric speciation (or sympatric evolution of reproductive barriers), that after all strongly suggests that sympatric speciation is indeed possible and may have consequences that complicate our view on what is a species and when.
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