As noticed already by Mayr (1963), sustained disruptive selection, operating over many generations, is only achieved under highly restrictive and unrealistic conditions in classical population genetical models. Speciation theory is the prototype example of a research field where scientific truth can only be approached through the intersection of independent lies (Levins 1966). However, most of these models rely on the simultaneous occurrence of two Fisherian runaway processes, which will only occur in the presence of large variation in female preferences. Even though selection was seen as critically important in . * Views captured on Cambridge Core between #date#. Proc Roy Soc Lond B 267:21332141, Wu CI (1985) A stochastic simulation study on speciation by sexual selection. We thank Thor Veen for many stimulating discussions and Roger Butlin and the referees for their useful comments. A preference for locally adapted mates is even more advantageous when offspring are more likely to end up in the same habitat as the parents (for example, when individuals are philopatric to some degree) or exert matching habitat choice on the basis of their ecological phenotype (Edelaar et al. Such a divergence is not implausible in case of Fisherian runaway selection: since a Fisherian runaway process can be based on any arbitrary male trait, it easy to imagine that it runs in different directions in different (daughter) populations. Am Nat 156:S77S101, Doebeli M, Dieckmann U (2005) Adaptive dynamics as a mathematical tool for studying the ecology of speciation processes. The above example of branching induced by the competition of a consumer species for resources may appear specific, but in the last decade a multitude of ecological scenarios have been identified where evolutionary branching is expected to occur (Dieckmann et al. 2008; Ripa 2009), and it is explained by the fact that assortative mating induces stabilising selection when choosiness is costly. Even if this is not the case, it is conceivable that environmental differences create the genetic associations between ecological and mating strategies required for speciation if different combinations of ecotypes and mating types are favoured in different environments (e.g., Kawata et al. and more. J Evol Biol 12:2737, Nosil P, Yukilevich R (2008) Mechanims of reinforcement in natural and simulated polymorphic populations. The concept of evolutionary branching reveals how a stable regime of disruptive natural selection can be created and maintained in a plausible and realistic way. Although this path to speciation through sexual selection is possible in principle, we do not consider it very likely because it will only occur if the change in environment is sudden and large (see Higashi et al. Being the elaboration of a conference talk, this contribution is biased to our own work, and it does not address important aspects, such as the explanatory power of speciation models when applied to well-studied real-world systems (cichlids: Lande et al. Evol Ecol Res 5:739757, Andersson M (1994) Sexual selection. 1993a, b; Day 2005). The model discussed above takes a more integrative perspective by viewing the evolution of ecological differentiation and the evolution of assortative mating are mutually dependent processes that are both required for adaptive speciation. In addition, ecological differentiation of the incipient species is required in order to allow their coexistence in a longer-term perspective. Weissing, F.J., Edelaar, P. & van Doorn, G.S. volume65,pages 461480 (2011)Cite this article. TAUTZ, D. Accordingly, externally induced prezygotic isolation is replaced by internal prezygotic isolation mechanisms. 2004; see also Lande et al. In a case like this, no alternative ecotype can invade, and there is stabilising selection for the ecotype matching the peak of the resource distribution. As we will discuss in the next section, the main problem of ecological models is to explain the evolution of assortative mating and, as a consequence, reproductive isolation. The orange boxes and arrows indicate the classical view of speciation, as championed by Ernst Mayr (1942, 1963) and other architects of the Modern Synthesis. Accordingly, speciation models seemed to suggest that adaptive speciation is a rare and unlikely phenomenon. This is now changing gradually, and the mating process, in particular the costs of choosiness, receive more attention in the recent literature on ecological speciation (e.g., Matessi et al. This book was first published in 2004. In the DieckmannDoebeli model, no costs are associated with assortative mating, while it seems plausible that choosiness always involves at least some costs (Andersson 1994). There is, however, a good reason why sexual selection models have focused on Fisherian runaway selection. In the model, this can be achieved by a combination of weak selection and a large influx of new mutations: female preferences will become sufficiently variable if the costs of being choosy are small and if the distribution of new preference mutations is relatively broad. Google Scholar, Kokko H, Heubel K (2008) Condition-dependence, genotype-by-environment interactions and the lek paradox. CAS Van Doorn et al. However, Darwin's verbal arguments are often vague and not always convincing, partly because of his pre-Mendelian ideas on inheritance. In the simulation shown, two daughter species have evolved: a large-billed species with blue males and female preference for blue, and a small-billed species with red males and female preference for red. Accordingly, natural and sexual selection work hand in hand, mutually reinforcing each other and paving the way to adaptive speciation (Fig. Moreover, one might argue that speciation in this case is not really adaptive, since it relies on non-adaptive processes like the accumulation of mutations. 2004; Bolnick and Fitzpatrick 2007; Ritchie 2007). Steinfartz, Sebastian Scientists use the term "genomic island" to refer to the parts of the genome that underlie this reproductive isolation or adaptation. Species and the Ability to Reproduce Over time, the varied demands of their new lifestyles lead to multiple speciation events originating from a single species. One point of concern is related to the fact that speciation is not the only possible outcome when a population is subject to evolutionary branching (Rueffler et al. As argued by Van Doorn et al. This is illustrated in Fig. Darwin himself fully recognized the puzzle. Science 277:18081811, Servedio MR (2004) The what and why of research on reinforcement. Over time, the varied demands of their new lifestyles lead to multiple speciation events originating from a single species. To save content items to your account, Recently, we demonstrated by means of a good genes model that the divergence of mating preferences is actually not required to give sexual selection a crucial role in adaptive speciation (Van Doorn et al. TREE 16:330343, Turner GF, Burrows MT (1995) A model of sympatric speciation by sexual selection. The two isolated populations evolve separately, thereby gradually diverging from each other. Adaptive Radiation is one of the patterns of Macroevolution Is macroevolution a fact or a theory? For example, it has been argued that the decline in haplochromine cichlid diversity in Lake Victoria was caused by the deterioration of underwater light conditions, because the increased turbidity of the water compromised female mate choice based on male coloration (Seehausen et al. Speciation is completed when, in addition, a genetic association (i.e., linkage disequilibrium) develops between ecotypes and mating types, giving rise to reproductively isolated and, at the same time, ecologically differentiated daughter species. Willensdorfer, Martin The fixed level of assortative mating based on ecology turned out to be a model parameter of crucial importance. Accordingly, mate choice based on such indicator traits has a clear directionality, making it difficult to conceive how sexual selection could lead to the divergence of preferences between two nascent species. 4) Area effects: Speciation driven by ecological factors is promoted by larger geographic areas (e.g., of islands or lakes). Evolution 55:10851094, Panhuis TM, Butlin R, Zuk M, Tregenza T (2001) Sexual selection and speciation. 1999; Fig. Now several things can happen. Adaptive radiation, as a phenomenon, has tremendous research potential: The existence of a suite of closely related species adapted to exploit different habitats or lifestyles allows one to make comparative studies on the processes of speciation and selection in natural populations. However, ecological differentiation is not sufficient for achieving speciation (Fig. 2006. A variety of assortative-mating models has been comprehensively reviewed by Gavrilets (2004, chapter 10). We may conclude that speciation through sexual selection, driven by diverging Fisherian runaway processes, is a possibilityat least in theory. It is a key process in the evolution of biodiversity and has played a significant role in the evolution of many different groups of organisms. Reproductive isolation can evolve via two routes. The analytical results underlying Fig. By means of an integrated model, incorporating both ecological interactions and sexual selection, we demonstrate that disruptive selection on both ecological and mating strategies is necessary, but not sufficient, for speciation to occur. 5, in the absence of ecological divergence, the splitting into daughter species is usually only a transient phenomenon. Second, sexual selection creates or strengthens assortative mating with respect to the ecological strategy, since it reduces the rate of interbreeding between specialists for different habitats. The same observation has been made in other models (e.g., Kirkpatrick and Nuismer 2004; Kopp and Hermisson 2008; Pennings et al. Disruptive selection on the ecological character leads to a broad distribution of bill sizes (Fig. 2001; palms: Gavrilets and Vose 2007). Google Scholar, Eizaguirre C, Lenz TL, Traulsen A, Milinski M (2009) Speciation accelerated and stabilized by pleiotropic major histocompatibility immunogenes. Otherwise, the required genetical correlation between ecological and mating strategies does apparently not evolve. It is important to realise that both approaches have their virtues and their shortcomings; and that each approach sheds light on different aspects of the process of speciation. Evolution 58:222237, PubMed These models can explain the evolution of prezygotic reproductive isolation, but they are typically vague on questions like ecological coexistence. 2008; guppies: Labonne and Hendry 2010; walking sticks: Nosil and Yukilevich 2008; snails: Sadedin et al. NAESJE, T. F. J Evol Biol 21:10051023, Kotiaho JS, Simmons LW, Tomkins JL (2001) Towards a resolution of the lek paradox. As a consequence, natural and sexual selection can favour the same traits, thereby mutually reinforcing each other (as in the case of condition-dependent ornaments discussed above). For example, a large-billed bird is efficient in utilising seeds of large size (illustrated by the dashed line in Fig. Males which are ecologically not well adapted to the local conditions (e.g., a large-billed bird in habitat 1) do not only have an ecological disadvantage, but also a mating disadvantage, since they are not are not in the condition to develop the bright plumage preferred by females. In other words, for speciation to occur, disruptive natural and sexual selection have to be assisted by at least some degree of assortative mating based on the ecological character. As Mayr famously quipped, sympatric speciation is like the Lernean Hydra: "which grew two new heads whenever one of its heads was cut off" (p. 451; ( Mayr 1963 )). is added to your Approved Personal Document E-mail List under your Personal Document Settings In addition, the fitness penalty associated with assortative mating should be frequency dependent, since rare phenotypes will have more difficulty in finding a mate of similar phenotype than common ones. In situations like these, it is often impossible to say that one model variant is inherently better than an alternative one. 7, it becomes apparent that speciation does not occur for parameter combinations where mating is solely dependent on sexual selection, that is, the match between female preferences and male ornaments (left-hand side of Fig. 2004. Book summary views reflect the number of visits to the book and chapter landing pages. From Fig. Correspondence to From this, Dieckmann and Doebeli conclude that the verbal arguments of Darwin (1859) and the graphical approach of Rosenzweig (1978) were essentially correct and that competitive speciation completely driven by disruptive natural selection is indeed a plausible scenario. 2007. International Institute for Applied Systems Analysis, Austria, University of British Columbia, Vancouver, Rijksuniversiteit Leiden, The Netherlands, Select 2 - Speciation in Historical Perspective, Select 3 - Genetic Theories of Sympatric Speciation, Select 4 - Adaptive Dynamics of Speciation: Ecological Underpinnings, Select 5 - Adaptive Dynamics of Speciation: Sexual Populations, Select 6 - Genetic Theories of Allopatric and Parapatric Speciation, Select 7 - Adaptive Dynamics of Speciation: Spatial Structure, Select B - Ecological Mechanisms of Speciation, Select 8 - Speciation and Radiation in African Haplochromine Cichlids, Select 9 - Natural Selection and Ecological Speciation in Sticklebacks, Select 10 - Adaptive Speciation in Northern Freshwater Fishes, Select 11 - Sympatric Speciation in Insects, Select 12 - Adaptive Speciation in Agricultural Pests, Select 13 - Ecological Speciation in Flowering Plants, Select 14 - Experiments on Adaptation and Divergence in Bacterial Populations, Select 15 - Phylogeography and Patterns of Incipient Speciation, Select 16 - Evolutionary Diversification of Caribbean Anolis Lizards, Select 17 - Adaptive Radiation of African Montane Plants, Select 18 - Diversity and Speciation of Semionotid Fishes in Mesozoic Rift Lakes, Find out more about saving to your Kindle, 3 - Genetic Theories of Sympatric Speciation, 4 - Adaptive Dynamics of Speciation: Ecological Underpinnings, 5 - Adaptive Dynamics of Speciation: Sexual Populations, 6 - Genetic Theories of Allopatric and Parapatric Speciation, 7 - Adaptive Dynamics of Speciation: Spatial Structure, 8 - Speciation and Radiation in African Haplochromine Cichlids, 9 - Natural Selection and Ecological Speciation in Sticklebacks, 10 - Adaptive Speciation in Northern Freshwater Fishes, 12 - Adaptive Speciation in Agricultural Pests, 13 - Ecological Speciation in Flowering Plants, 14 - Experiments on Adaptation and Divergence in Bacterial Populations, 15 - Phylogeography and Patterns of Incipient Speciation, 16 - Evolutionary Diversification of Caribbean, 17 - Adaptive Radiation of African Montane Plants, 18 - Diversity and Speciation of Semionotid Fishes in Mesozoic Rift Lakes, Book DOI: https://doi.org/10.1017/CBO9781139342179. 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