International Journal of Ecology Ecological Speciation Guest Editors: Marianne Elias, Rui Faria, Zachariah Gompert, and Andrew Hendry Ecological Speciation International Journal of Ecology Ecological Speciation Guest Editors: Marianne Elias, Rui Faria, Zachariah Gompert, and Andrew Hendry Copyright © 2012 Hindawi Publishing Corporation. All rights reserved. This is a special issue published in “International Journal of Ecology.” All articles are open access articles distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Editorial Board Mariana Amato, Italy Jean-Guy Godin, Canada Panos V. Petrakis, Greece Madhur Anand, Canada David Goldstein, USA Daniel I. Rubenstein, USA Joseph R. Bidwell, USA Shibu Jose, USA Herman H. Shugart, USA L. M. Chu, Hong Kong Chandra Prakash Kala, India Andrew Sih, USA Jean Clobert, France Pavlos Kassomenos, Greece R.C. Sihag, India Michel Couderchet, France Thomas H. Kunz, USA C. ter Braak, The Netherlands Ronald D. Delaune, USA Bruce D. Leopold, USA John Whitaker, USA Andrew Denham, Australia A. E. Lugo, USA Walter Whitford, USA Mark A. Elgar, Australia Patricia Mosto, USA J. J. Wiens, USA Jingyun Fang, China Mats Olsson, Australia Xiaozhang Yu, China Contents Factors Influencing Progress toward Ecological Speciation, Marianne Elias, Rui Faria, Zachariah Gompert, and Andrew Hendry Volume 2012, Article ID 235010, 7 pages The Role of Parasitism in Adaptive RadiationsWhen Might Parasites Promote and When Might They Constrain Ecological Speciation?, Anssi Karvonen and Ole Seehausen Volume 2012, Article ID 280169, 20 pages Parallel Ecological Speciation in Plants?, Katherine L. Ostevik, Brook T. Moyers, Gregory L. Owens, and Loren H. Rieseberg Volume 2012, Article ID 939862, 17 pages From Local Adaptation to Speciation: Specialization and Reinforcement, Thomas Lenormand Volume 2012, Article ID 508458, 11 pages Testing the Role of Habitat Isolation among Ecologically Divergent Gall Wasp Populations, Scott P. Egan, Glen R. Hood, and James R. Ott Volume 2012, Article ID 809897, 8 pages Underappreciated Consequences of Phenotypic Plasticity for Ecological Speciation, Benjamin M. Fitzpatrick Volume 2012, Article ID 256017, 12 pages Ecological Adaptation and Speciation: The Evolutionary Significance of Habitat Avoidance as a Postzygotic Reproductive Barrier to Gene Flow,Jeffrey L. Feder, Scott P. Egan, and Andrew A. Forbes Volume 2012, Article ID 456374, 15 pages Larval Performance in the Context of Ecological Diversification and Speciation in Lycaeides Butterflies, Cynthia F. Scholl, Chris C. Nice, James A. Fordyce, Zachariah Gompert, and Matthew L. Forister Volume 2012, Article ID 242154, 13 pages Divergent Selection and Then What Not: The Conundrum of Missing Reproductive Isolation in Misty Lake and Stream Stickleback,KatjaRas¨ anen,¨ Matthieu Delcourt, Lauren J. Chapman, and Andrew P. Hendry Volume 2012, Article ID 902438, 14 pages How Facilitation May Interfere with Ecological Speciation, P. Liancourt, P. Choler, N. Gross, X. Thibert-Plante, and K. Tielborger¨ Volume 2012, Article ID 725487, 11 pages Use of Host-Plant Trait Space by Phytophagous Insects during Host-Associated Differentiation: The Gape-and-Pinch Model,StephenB.Heard Volume 2012, Article ID 192345, 15 pages Habitat Choice and Speciation, Sophie E. Webster, Juan Galindo, John W. Grahame, and Roger K. Butlin Volume 2012, Article ID 154686, 12 pages The Role of Environmental Heterogeneity in Maintaining Reproductive Isolation between Hybridizing Passerina (Aves: Cardinalidae) Buntings, Matthew D. Carling and Henri A. Thomassen Volume 2012, Article ID 295463, 11 pages Pollinator-Driven Speciation in Sexually Deceptive Orchids, Shuqing Xu, Philipp M. Schluter,¨ and Florian P. Schiestl Volume 2012, Article ID 285081, 9 pages Synergy between Allopatry and Ecology in Population Differentiation and Speciation, Yann Surget-Groba, Helena Johansson, and Roger S. Thorpe Volume 2012, Article ID 273413, 10 pages Of “Host Forms” and Host Races: Terminological Issues in Ecological Speciation, Daniel J. Funk Volume 2012, Article ID 506957, 8 pages Learning the Hard Way: Imprinting Can Enhance Enforced Shifts in Habitat Choice, Niclas Vallin and Anna Qvarnstrom¨ Volume 2011, Article ID 287532, 7 pages Sympatric Speciation in Threespine Stickleback: Why Not?, Daniel I. Bolnick Volume 2011, Article ID 942847, 15 pages Ecological Divergence and the Origins of Intrinsic Postmating Isolation with Gene Flow, Aneil F. Agrawal, JeffreyL.Feder,andPatrikNosil Volume 2011, Article ID 435357, 15 pages Hindawi Publishing Corporation International Journal of Ecology Volume 2012, Article ID 235010, 7 pages doi:10.1155/2012/235010 Editorial Factors Influencing Progress toward Ecological Speciation Marianne Elias,1 Rui Faria,2, 3 Zachariah Gompert,4 and Andrew Hendry5 1 CNRS, UMR 7205, Mus´eum National d’Histoire Naturelle, 45 Rue Buffon, CP50, 75005 Paris, France 2 CIBIO/UP—Centro de Investigac¸ao˜ em Biodiversidade e Recursos Gen´eticos, Universidade do Porto, Campus Agrario´ de Vairao,˜ R. Monte-Crasto, 4485-661 Vairao,˜ Portugal 3 IBE—Institut de Biologia Evolutiva (UPF-CSIC), Universitat Pompeu Fabra, PRBB, Avenue Doctor Aiguader N88, 08003 Barcelona, Spain 4 Department of Botany, 3165, University of Wyoming, 1000 East University Avenue Laramie, WY 82071, USA 5 Redpath Museum and Department of Biology, McGill University, 859 Sherbrooke Street West Montreal, QC, Canada H3A 2K6 Correspondence should be addressed to Marianne Elias, [email protected] Received 28 March 2012; Accepted 28 March 2012 Copyright © 2012 Marianne Elias et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. 1. Introduction why there are so many species [13] and also why there are so few species [14]. Ecological speciation occurs when adaptation to divergent This special issue on ecological speciation puts snapshots environments, such as different resources or habitats, leads of progress toward speciation sharply in focus and then to the evolution of reproductive isolation [1, 2]. More specif- investigates this topic from several angles. First, several ically, divergent (or disruptive) selection between environ- papers provide conceptual or theoretical models for how to ments causes the adaptive divergence of populations, which consider progress toward ecological speciation (Funk; Heard; leads to the evolution of reproductive barriers that decrease, Lenormand; Liancourt et al.; Agrawal et al.). Second, several and ultimately cease, gene flow [3, 4]. Supported by a papers highlight the noninevitability of ecological speciation growing number of specific examples, ecological speciation is through investigations where ecological speciation seems to thought to be a primary driving force in evolutionary diver- be strongly constrained (Ras¨ anen¨ et al.; Bolnick) or at least sification, exemplified most obviously in adaptive radiations lacking definitive evidence (Ostevik et al.; Scholl et al.). Some [5–8]. of these papers also uncover specific factors that seem par- As acceptance of the importance of ecological speciation ticularly important to ecological speciation, such as the has grown, so too has the recognition that it is not all power- combination of geographic isolation and habitat differences ful. Specifically, a number of instances of nonecological (Surget-Groba et al.), the strength of disruptive selection and speciation and nonadaptive radiation seem likely [9], and assortative mating (Bolnick), and host-plant adaptation colonization of different environments does not always lead (Scholl et al.). Third, several particularly important factors to speciation [10, 11]. This latter point is obvious when emerge as a common theme across multiple papers, par- one recognizes that although essentially all species are com- ticularly parasites/pollinators (Xu et al.; Karvonen and See- posed of a number of populations occupying divergent envi- hausen), habitat choice (Webster et al.; Feder et al.; Carling ronments [12], only a fraction of these ever spin off to be- and Thomassen; Egan et al.), and phenotypic plasticity come full-fledged species. Instead, populations occupying (Fitzpatrick; Vallin and Qvarnstrom).¨ divergent environments or using different resources show Here we highlight the most important aspects of these varying levels of progress toward ecological speciation—and contributions and how they relate to three major topics: (i) this variation provides the substrate to study factors that models for progress toward ecological speciation; (ii) vari- promote and constrain progress along the speciation contin- able progress toward ecological speciation in nature; and (iii) uum. By studying these factors, we can begin to understand factors affecting progress toward ecological speciation. 2 International Journal of Ecology 2. Models for Progress toward a theoretical and statistical framework for testing this model Ecological Speciation and applies it to insects using goldenrod plants. Local adaptation is often the first step in ecological spe- Terminological issues have long bedevilled communication ciation, and so factors influencing local adaptation will be among researchers working on speciation. D. J. Funk ad- critical for ecological speciation. Local adaptation can either dresses this topic by first clarifying the