Molecular Phylogenetics and Evolution 41 (2006) 606–621 www.elsevier.com/locate/ympev 1055-7903/$ - see front matter  2006 Elsevier Inc. All rights reserved. doi:10.1016/j.ympev.2006.06.005 Linking patterns and processes of species diversiWcation in the cone Xies Strobilomyia (Diptera: Anthomyiidae) Jean-Marie Sachet a,¤ , Alain Roques b , Laurence Després a a Laboratoire d’Ecologie Alpine, UMR 5553, Université Joseph Fourier, BP 53, 38041 Grenoble Cedex 09, France b Unité de Zoologie Forestière, INRA Centre d’Orléans, BP 20619, 45166 Olivet Cedex, France Received 13 February 2006; accepted 7 June 2006 Available online 9 June 2006 Abstract Phytophagous insects provide useful models for the study of ecological speciation. Much attention has been paid to host shifts, whereas situations where closely related lineages of insects use the same plant during diVerent time periods have been relatively neglected in previous studies of insect diversiWcation. Flies of the genus Strobilomyia are major pests of conifers in Eurasia and North America. They are specialized feeders in cones and seeds of Abies (Wr), Larix (larch) ,and Picea (spruce). This close association is accompanied by a large number of sympatric Strobilomyia species coexisting within each tree genus. We constructed a molecular phylogeny with a 1320 base-pair fragment of mitochondrial DNA that demonstrated contrasting patterns of speciation in larch cone Xies, as opposed to spruce and Wr cone Xies; this despite their comparable geographic distributions and similar resource quality of the host. Species diversity is the highest on larch, and speciation is primarily driven by within-host phenological shifts, followed by allopatric speciation during geograph- ical expansion. By contrast, fewer species exploit spruce and Wr, and within-host phenological shifts did not occur. This study illustrates within-host adaptive radiation through phenological shifts, a neglected mode of sympatric speciation.  2006 Elsevier Inc. All rights reserved. Keywords: Adaptive radiation; Ecological speciation; Host shift; Mitochondrial DNA; Molecular phylogeny; Oviposition behavior; Phenological shift 1. Introduction The study of species concepts and speciation has under- gone many developments since Darwin (Pigliucci, 2003). In the 1930s, research shifted away from the study of natural selection as the driving force of speciation, and highlighted the fundamental role of geographical reproductive isolation in population diVerentiation (Bush, 1975; Coyne and Price, 2000; Mayr, 1963). Sympatric speciation was long consid- ered impossible because the conditions required were thought unlikely to occur in nature (Bush, 1994). In the past few years, however, ecological shifts have been shown to play a major role in the process of speciation. They are at the heart of the mechanism of ecological speciation (Orr and Smith, 1998; Rundle and Nosil, 2005; Schluter, 2001; Wiens, 2004); according to which, populations living in diVerent environments or using diVerent resources face con- trasting selection pressures on traits that can ultimately lead to reproductive isolation and the formation of new species. Because of their tremendous biodiversity, phytoph- agous insects have been particularly well studied with respect to sympatric or ecological speciation (Berlocher and Feder, 2002; Roderick and Gillespie, 1998). Much attention has focused on host shifts and the evolution of host races into new species (Abrahamson et al., 2003; Drès and Mal- let, 2002; Emelianov et al., 2004; Filchak et al., 2000; Thomas et al., 2003; Via, 1999), but other interesting situa- tions arise when insect clades specialize in diVerent anatom- ical parts of the same hosts, or use the same resource during diVerent time periods (Groman and Pellmyr, 2000). For example, the tephritid Xies of the genus Blepharone- ura are highly host speciWc, and some species also specialize * Corresponding author. Fax: +33 0 4 76 51 42 79. E-mail address: Jean-Marie.Sachet@ujf-grenoble.fr (J.-M. Sachet).