ORIGINAL PAPER Speciation: from diversification to reproductive isolation Roger Ha ¨rdling Æ A ˚ sa Lankinen Æ Jo ¨rgen Ripa Æ Erik Svensson Received: 3 December 2007 / Accepted: 8 December 2007 / Published online: 4 January 2008 Ó Springer Science+Business Media B.V. 2008 A fundamental goal of evolutionary biology is to explain the enormous diversity among animal and plant species. But also within species there is often large genetic and pheno- typic variation, and such variation is necessary for evolution to create new reproductively isolated species. This general idea was the impetus for an international symposium organized by the undersigned, and held at the Department of Ecology at Lund University in September 2006. The title of this symposium: Speciation: from diversification to reproductive isolation broadly summarizes the overarching theme: to integrate and synthesize related work from a variety of areas dealing with within-population processes pertinent to vari- ation within and between populations. The present special issue contains contributions from some of the speakers at the conference but we have also invited some additional authors that were invited to the symposium but unable to attend. The subject of differentiation within populations has a long history at the University of Lund, dating back to the groundbreaking work of plant ecological geneticist Go ¨ te Turesson in the early 1920s (Turesson 1922). Go ¨te Turesson is known for coining the term ‘‘ecotype’’ for the heritable phenotypic varieties that are adapted to local environmental conditions. Turesson’s important contributions, published in a rather small scientific journal based in Sweden, gained increased attention in the nineties with the renewed interest in the role of ecology in speciation (Schluter 2000). These contributions from a pioneer in plant ecological genetics are surprisingly modern and have still much to tell us today, when ecological speciation has been widely accepted and ecological and genetic studies of polymorphic system are exploding in numbers, often integrated with modern molecular techniques. R. Ha ¨rdling (&) Á E. Svensson Animal Ecology, Ecology Building, Lund University, 223 62 Lund, Sweden e-mail: roger.hardling@zooekol.lu.se A ˚ . Lankinen Plant Ecology and Systematics, Ecology Building, Lund University, 223 62 Lund, Sweden J. Ripa Theoretical Ecology, Ecology Building, Lund University, 223 62 Lund, Sweden 123 Evol Ecol (2009) 23:1–4 DOI 10.1007/s10682-007-9240-2