1
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Nosil P, de Carvalho CF, Villoutreix R, Zamorano LS, Sinclair-Waters M, Planidin NP, Parchman TL, Feder J, Gompert Z. Evolution repeats itself in replicate long-term studies in the wild. SCIENCE ADVANCES 2024; 10:eadl3149. [PMID: 38787954 PMCID: PMC11122682 DOI: 10.1126/sciadv.adl3149] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2023] [Accepted: 04/22/2024] [Indexed: 05/26/2024]
Abstract
The extent to which evolution is repeatable remains debated. Here, we study changes over time in the frequency of cryptic color-pattern morphs in 10 replicate long-term field studies of a stick insect, each spanning at least a decade (across 30 years of total data). We find predictable "up-and-down" fluctuations in stripe frequency in all populations, representing repeatable evolutionary dynamics based on standing genetic variation. A field experiment demonstrates that these fluctuations involve negative frequency-dependent natural selection (NFDS). These fluctuations rely on demographic and selective variability that pushes populations away from equilibrium, such that they can reliably move back toward it via NFDS. Last, we show that the origin of new cryptic forms is associated with multiple structural genomic variants such that which mutations arise affects evolution at larger temporal scales. Thus, evolution from existing variation is predictable and repeatable, but mutation adds complexity even for traits evolving deterministically under natural selection.
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Affiliation(s)
- Patrik Nosil
- Theoretical and Experimental Ecology (SETE), CNRS, 2 route du CNRS, 09200 Moulis, France
- CEFE, Université de Montpellier, CNRS, EPHE, IRD, Montpellier, France
| | | | | | - Laura S. Zamorano
- Theoretical and Experimental Ecology (SETE), CNRS, 2 route du CNRS, 09200 Moulis, France
- CEFE, Université de Montpellier, CNRS, EPHE, IRD, Montpellier, France
| | | | | | | | - Jeffrey Feder
- Department of Biology, Notre Dame University, South Bend, IN 11111, USA
| | - Zach Gompert
- Department of Biology, Utah State University, Logan, UT 84322, USA
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2
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Nosil P, Gompert Z, Funk DJ. Divergent dynamics of sexual and habitat isolation at the transition between stick insect populations and species. Nat Commun 2024; 15:2273. [PMID: 38480699 PMCID: PMC10937975 DOI: 10.1038/s41467-024-46294-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Accepted: 02/22/2024] [Indexed: 03/17/2024] Open
Abstract
Speciation is often viewed as a continuum along which populations diverge until they become reproductively-isolated species. However, such divergence may be heterogeneous, proceeding in fits and bursts, rather than being uniform and gradual. We show in Timema stick insects that one component of reproductive isolation evolves non-uniformly across this continuum, whereas another does not. Specifically, we use thousands of host-preference and mating trials to study habitat and sexual isolation among 42 pairs of taxa spanning a range of genomic differentiation and divergence time. We find that habitat isolation is uncoupled from genomic differentiation within species, but accumulates linearly with it between species. In contrast, sexual isolation accumulates linearly across the speciation continuum, and thus exhibits similar dynamics to morphological traits not implicated in reproductive isolation. The results show different evolutionary dynamics for different components of reproductive isolation and highlight a special relevance for species status in the process of speciation.
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Affiliation(s)
- Patrik Nosil
- CEFE, Univ Montpellier, CNRS, EPHE, IRD, Montpellier, France
| | | | - Daniel J Funk
- Department of Biological Sciences, Vanderbilt University, Nashville, TN, USA.
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3
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Gompert Z, Feder JL, Nosil P. The short-term, genome-wide effects of indirect selection deserve study: A response to Charlesworth and Jensen (2022). Mol Ecol 2022; 31:4444-4450. [PMID: 35909250 DOI: 10.1111/mec.16614] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 06/21/2022] [Accepted: 07/01/2022] [Indexed: 11/30/2022]
Abstract
We recently published a paper quantifying the genome-wide consequences of natural selection, including the effects of indirect selection due to the correlation of genetic regions (neutral or selected) with directly selected regions (Gompert et al., 2022). In their critique of our paper, Charlesworth and Jensen (2022) make two main points: (i) indirect selection is equivalent to hitchhiking and thus well documented (i.e., our results are not novel) and (ii) that we do not demonstrate the source of linkage disequilibrium (LD) between SNPs and the Mel-Stripe locus in the Timema cristinae experiment we analyse. As we discuss in detail below, neither of these are substantial criticisms of our work.
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Affiliation(s)
- Zachariah Gompert
- Department of Biology, Utah State University, Logan, Utah, USA.,Ecology Center, Utah State University, Logan, Utah, USA
| | - Jeffrey L Feder
- Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, USA
| | - Patrik Nosil
- CEFE, University Montpellier, CNRS, EPHE, IRD, University Paul Valéry Montpellier 3, Montpellier, France
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4
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Chebib J, Guillaume F. Pleiotropy or linkage? Their relative contributions to the genetic correlation of quantitative traits and detection by multitrait GWA studies. Genetics 2021; 219:6375447. [PMID: 34849850 PMCID: PMC8664587 DOI: 10.1093/genetics/iyab159] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Accepted: 09/05/2021] [Indexed: 11/23/2022] Open
Abstract
Genetic correlations between traits may cause correlated responses to selection. Previous models described the conditions under which genetic correlations are expected to be maintained. Selection, mutation, and migration are all proposed to affect genetic correlations, regardless of whether the underlying genetic architecture consists of pleiotropic or tightly linked loci affecting the traits. Here, we investigate the conditions under which pleiotropy and linkage have different effects on the genetic correlations between traits by explicitly modeling multiple genetic architectures to look at the effects of selection strength, degree of correlational selection, mutation rate, mutational variance, recombination rate, and migration rate. We show that at mutation-selection(-migration) balance, mutation rates differentially affect the equilibrium levels of genetic correlation when architectures are composed of pairs of physically linked loci compared to architectures of pleiotropic loci. Even when there is perfect linkage (no recombination within pairs of linked loci), a lower genetic correlation is maintained than with pleiotropy, with a lower mutation rate leading to a larger decrease. These results imply that the detection of causal loci in multitrait association studies will be affected by the type of underlying architectures, whereby pleiotropic variants are more likely to be underlying multiple detected associations. We also confirm that tighter linkage between nonpleiotropic causal loci maintains higher genetic correlations at the traits and leads to a greater proportion of false positives in association analyses.
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Affiliation(s)
- Jobran Chebib
- Department of Evolutionary Biology and Environmental Studies, University of Zürich, 8057 Zürich, Switzerland.,Institute of Evolutionary Biology, University of Edinburgh, Edinburgh EH9 3FL, UK
| | - Frédéric Guillaume
- Department of Evolutionary Biology and Environmental Studies, University of Zürich, 8057 Zürich, Switzerland.,Organismal and Evolutionary Biology Research Program, University of Helsinki, 00014 Helsinki, Finland
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5
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Villoutreix R, de Carvalho CF, Soria-Carrasco V, Lindtke D, De-la-Mora M, Muschick M, Feder JL, Parchman TL, Gompert Z, Nosil P. Large-scale mutation in the evolution of a gene complex for cryptic coloration. Science 2020; 369:460-466. [PMID: 32703880 DOI: 10.1126/science.aaz4351] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Revised: 02/29/2020] [Accepted: 05/19/2020] [Indexed: 11/02/2022]
Abstract
The types of mutations affecting adaptation in the wild are only beginning to be understood. In particular, whether structural changes shape adaptation by suppressing recombination or by creating new mutations is unresolved. Here, we show that multiple linked but recombining loci underlie cryptic color morphs of Timema chumash stick insects. In a related species, these loci are found in a region of suppressed recombination, forming a supergene. However, in seven species of Timema, we found that a megabase-size "supermutation" has deleted color loci in green morphs. Moreover, we found that balancing selection likely contributes more to maintaining this mutation than does introgression. Our results show how suppressed recombination and large-scale mutation can help to package gene complexes into discrete units of diversity such as morphs, ecotypes, or species.
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Affiliation(s)
- Romain Villoutreix
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK.,Centre d'Ecologie Fonctionnelle et Evolutive, UMR 5175 CNRS-Université de Montpellier, École Pratique des Hautes Études, Université Paul Valéry, 34293 Montpellier 5, France
| | | | - Víctor Soria-Carrasco
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK
| | - Dorothea Lindtke
- Department of Biological Sciences, University of Bern, Bern CH-3012, Switzerland
| | - Marisol De-la-Mora
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK.,Escuela Nacional de Estudios Superiores, Unidad Juriquilla, Querétaro 76230, México
| | - Moritz Muschick
- Institute of Ecology and Evolution, University of Bern, Bern 3012, Switzerland.,Department of Fish Ecology & Evolution, EAWAG, Swiss Federal Institute for Aquatic Science and Technology, Kastanienbaum CH-6047, Switzerland
| | - Jeffrey L Feder
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Thomas L Parchman
- Department of Biology, University of Nevada-Reno, Reno, NV 89557, USA
| | - Zach Gompert
- Department of Biology, Utah State University, Logan, UT 84322, USA
| | - Patrik Nosil
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK. .,Centre d'Ecologie Fonctionnelle et Evolutive, UMR 5175 CNRS-Université de Montpellier, École Pratique des Hautes Études, Université Paul Valéry, 34293 Montpellier 5, France.,Department of Biology, Utah State University, Logan, UT 84322, USA
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6
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Muschick M, Soria-Carrasco V, Feder JL, Gompert Z, Nosil P. Adaptive zones shape the magnitude of premating reproductive isolation in Timema stick insects. Philos Trans R Soc Lond B Biol Sci 2020; 375:20190541. [PMID: 32654646 DOI: 10.1098/rstb.2019.0541] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Simpson's fossil-record inspired model of 'adaptive zones' proposes that evolution is dominated by small fluctuations within adaptive zones, occasionally punctuated by larger shifts between zones. This model can help explain why the process of population divergence often results in weak or moderate reproductive isolation (RI), rather than strong RI and distinct species. Applied to the speciation process, the adaptive zones hypothesis makes two inter-related predictions: (i) large shifts between zones are relatively rare, (ii) when large shifts do occur they generate stronger RI than shifts within zones. Here, we use ecological, phylogenetic and behavioural data to test these predictions in Timema stick insects. We show that host use in Timema is dominated by moderate shifts within the systematic divisions of flowering plants and conifers, with only a few extreme shifts between these divisions. However, when extreme shifts occur, they generate greater RI than do more moderate shifts. Our results support the adaptive zones model, and suggest that the net contribution of ecological shifts to diversification is dependent on both their magnitude and frequency. We discuss the generality of our findings in the light of emerging evidence from diverse taxa that the evolution of RI is not always the only factor determining the origin of species diversity. This article is part of the theme issue 'Towards the completion of speciation: the evolution of reproductive isolation beyond the first barriers'.
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Affiliation(s)
- Moritz Muschick
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK.,Department of Fish Ecology and Evolution, Eawag, Swiss Federal Institute for Aquatic Science and Technology, 6047 Kastanienbaum, Switzerland.,Aquatic Ecology and Evolution, Institute of Ecology and Evolution, University of Bern, 3012 Bern, Switzerland
| | - Víctor Soria-Carrasco
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK.,Department of Crop Genetics, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, UK
| | - Jeffrey L Feder
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Zach Gompert
- Department of Biology, Utah State University, Logan, UT 84322, USA
| | - Patrik Nosil
- Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK.,Center for Evolution and Functional Ecology, CNRS, 34000 Montpellier, France
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7
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Hangartner S, Lasne C, Sgrò CM, Connallon T, Monro K. Genetic covariances promote climatic adaptation in Australian
Drosophila
*. Evolution 2019; 74:326-337. [DOI: 10.1111/evo.13831] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2019] [Accepted: 07/12/2019] [Indexed: 12/27/2022]
Affiliation(s)
- Sandra Hangartner
- School of Biological Sciences Monash University Building 18 Melbourne Victoria 3800 Australia
| | - Clementine Lasne
- School of Biological Sciences Monash University Building 18 Melbourne Victoria 3800 Australia
| | - Carla M. Sgrò
- School of Biological Sciences Monash University Building 18 Melbourne Victoria 3800 Australia
| | - Tim Connallon
- School of Biological Sciences Monash University Building 18 Melbourne Victoria 3800 Australia
| | - Keyne Monro
- School of Biological Sciences Monash University Building 18 Melbourne Victoria 3800 Australia
- Centre for Geometric Biology Monash University Melbourne Victoria 3800 Australia
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8
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Byers JA, Sadowsky A, Levi Zada A. Index of host habitat preference explored by movement-based simulations and trap captures. J Anim Ecol 2018; 87:1320-1330. [PMID: 29938788 DOI: 10.1111/1365-2656.12877] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2018] [Accepted: 06/06/2018] [Indexed: 11/30/2022]
Abstract
Animal species likely have different strengths of host habitat preference (HHP) that might be characterized by a standardized index ranging from 0 (no preference) to 1 (maximum preference). We hypothesized that in some species, HHP may result from individuals dispersing out of the host habitat having a probability of turning back at the boundary, or after entering host habitat by reducing speed or increasing size of turning angles. Computer simulations of individuals moving between various sized patches of host and nonhost habitat were conducted based on these three behaviours hypothesized to affect HHP. In the rebounding model, simulations resulted in equilibria of animal numbers inside and outside of host habitat that depend on sizes of these areas, initial number and the rebounding probability. Curvilinear regression of simulation results suggested an equation that predicted numbers in the host habitat and was solved for rebounding probability. A modified equation that sampled population densities (e.g., insect pheromone trap catches) inside and outside host habitat areas gave the rebounding probability, an index of HHP, without requiring the sizes of the areas. Simulations with traps and moving animals verified that the modified equation could predict the index correctly. The modified equation also estimates an index of HHP from sampled densities due to speed reductions and a combination of this and rebounding. Changes in angular turning size upon entering host habitat, however, did not affect habitat preference. Using pheromone trap captures, we found that the lesser date moth Batrachedra amydraula has a HHP for date Phoenix dactylifera plantations of 0.96. Host habitat preference indexes also were calculated from sampled insect densities reported in the literature. The new index of HHP is useful to characterize habitat patches of many organisms and aid understanding of animal spatial distributions and speciation processes. In addition, the index can be applied in studies of invasive species, trap crops of pest insects and conservation management.
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Affiliation(s)
- John A Byers
- Department of Entomology, Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel
| | | | - Anat Levi Zada
- Institute of Plant Protection, Agricultural Research Organization, Volcani Center, Rishon LeZion, Israel
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9
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Zellmer AJ. Microgeographic morphological variation across larval wood frog populations associated with environment despite gene flow. Ecol Evol 2018; 8:2504-2517. [PMID: 29531671 PMCID: PMC5838061 DOI: 10.1002/ece3.3829] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2017] [Revised: 11/22/2017] [Accepted: 12/06/2017] [Indexed: 11/06/2022] Open
Abstract
Gene flow has historically been thought to constrain local adaptation; yet, recent research suggests that populations can diverge despite exchanging genes. Here I use a common garden experiment to assess the combined effects of gene flow and natural selection on morphological variation of 16 wood frog (Rana sylvatica) populations, a species known to experience divergent selection pressures in open- and closed-canopy ponds across relatively small geographic scales. Wood frog tadpoles from different ponds showed significant morphological variation associated with canopy type with a trade-off between tail length and body depth consistent with previous research. In contrast, neutral genetic differentiation of nine microsatellite loci as measured by Jost's D was not associated with canopy type, indicating no pattern of isolation by environment. Genetic structure analyses indicated some substructure across the 16 ponds (K = 4); however, three out of four assigned clusters included both open- and closed-canopy ponds. Together, these results suggest that morphological divergence among these wood frog populations is occurring despite gene flow and that selection within these environments is strong. Furthermore, morphological variation among ponds differed across two sampling periods during larval development, demonstrating the importance of evaluating phenotypic divergence over multiple time periods and at a time relevant to the processes being studied.
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10
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Gutiérrez-Valencia J, Gutiérrez Y, G. Dias L. Species delimitation in the crypsis-defended and polymorphic stick insects of the genusLibethra(Phasmatodea, Diapheromeridae). ZOOL SCR 2017. [DOI: 10.1111/zsc.12242] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- Juanita Gutiérrez-Valencia
- Erasmus Mundus Master Programme in Evolutionary Biology (MEME); University of Groningen; 9747 AG Groningen the Netherlands
| | - Yeisson Gutiérrez
- Institute of Landscape Ecology; Universtiy of Münster; 48149 Münster Germany
| | - Lucimar G. Dias
- Faculty of Exact and Natural Sciences; Bionat Research Group; University of Caldas; Street 65, No. 26-10 A.A. 275 Manizales Colombia
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11
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Willink B, Svensson EI. Intra- and intersexual differences in parasite resistance and female fitness tolerance in a polymorphic insect. Proc Biol Sci 2017; 284:20162407. [PMID: 28123090 PMCID: PMC5310041 DOI: 10.1098/rspb.2016.2407] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2016] [Accepted: 12/20/2016] [Indexed: 11/12/2022] Open
Abstract
To understand host-parasite interactions, it is necessary to quantify variation and covariation in defence traits. We quantified parasite resistance and fitness tolerance of a polymorphic damselfly (Ischnura elegans), an insect with three discrete female colour morphs but with monomorphic males. We quantified sex and morph differences in parasite resistance (prevalence and intensity of water mite infections) and morph-specific fitness tolerance in the females in natural populations for over a decade. There was no evidence for higher parasite susceptibility in males as a cost of sexual selection, whereas differences in defence mechanisms between female morphs are consistent with correlational selection operating on combinations of parasite resistance and tolerance. We suggest that tolerance differences between female morphs interact with frequency-dependent sexual conflict, which maintains the polymorphism locally. Host-parasite interactions can therefore shape intra- and intersexual phenotypic divergence and interfere with sexual selection and sexual conflict.
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Affiliation(s)
- Beatriz Willink
- Department of Biology, Evolutionary Ecology Unit, Lund University, Ecology Building, Lund 223-62, Sweden
| | - Erik I Svensson
- Department of Biology, Evolutionary Ecology Unit, Lund University, Ecology Building, Lund 223-62, Sweden
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12
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Farkas TE, Montejo-Kovacevich G. Density-dependent selection closes an eco-evolutionary feedback loop in the stick insect Timema cristinae. Biol Lett 2015; 10:20140896. [PMID: 25505057 DOI: 10.1098/rsbl.2014.0896] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Empirical demonstrations of feedbacks between ecology and evolution are rare. Here, we used a field experiment to test the hypothesis that avian predators impose density-dependent selection (DDS) on Timema cristinae stick insects. We transplanted wild-caught T. cristinae to wild bushes at 50 : 50 cryptic : conspicuous morph ratio and manipulated density by transplanting either 24 or 48 individuals. The frequency of the conspicuous morph was reduced by 73% in the low-density treatment, but only by 50% in the high-density treatment, supporting a hypothesis of negative DDS. Coupled with previous studies on T. cristinae, which demonstrate that maladaptive gene flow reduces population density, we support an eco-evolutionary feedback loop in this system. Furthermore, our results support the hypothesis that predator satiation is the mechanism driving DDS. We found no effects of T. cristinae density on the abundance or species richness of other arthropods. Eco-evolutionary feedbacks, driven by processes like DDS, can have implications for adaptive divergence and speciation.
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Affiliation(s)
- Timothy E Farkas
- Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK
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13
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Bolnick DI, Shim KC, Brock CD. Female stickleback prefer shallow males: Sexual selection on nest microhabitat. Evolution 2015; 69:1643-1653. [DOI: 10.1111/evo.12682] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Accepted: 05/05/2015] [Indexed: 11/29/2022]
Affiliation(s)
- Daniel I. Bolnick
- Howard Hughes Medical Institute; University of Texas at Austin; Austin Texas 78712
- Department of Integrative Biology; University of Texas at Austin; Austin Texas 78712
| | - Kum Chuan Shim
- Department of Integrative Biology; University of Texas at Austin; Austin Texas 78712
| | - Chad D. Brock
- Department of Integrative Biology; University of Texas at Austin; Austin Texas 78712
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14
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Bolnick DI, Otto SP. The magnitude of local adaptation under genotype-dependent dispersal. Ecol Evol 2013; 3:4722-35. [PMID: 24363900 PMCID: PMC3867907 DOI: 10.1002/ece3.850] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2013] [Revised: 09/06/2013] [Accepted: 09/09/2013] [Indexed: 12/26/2022] Open
Abstract
Dispersal moves individuals from patches where their immediate ancestors were successful to sites where their genotypes are untested. As a result, dispersal generally reduces fitness, a phenomenon known as "migration load." The strength of migration load depends on the pattern of dispersal and can be dramatically lessened or reversed when individuals move preferentially toward patches conferring higher fitness. Evolutionary ecologists have long modeled nonrandom dispersal, focusing primarily on its effects on population density over space, the maintenance of genetic variation, and reproductive isolation. Here, we build upon previous work by calculating how the extent of local adaptation and the migration load are affected when individuals differ in their dispersal rate in a genotype-dependent manner that alters their match to their environment. Examining a one-locus, two-patch model, we show that local adaptation occurs through a combination of natural selection and adaptive dispersal. For a substantial portion of parameter space, adaptive dispersal can be the predominant force generating local adaptation. Furthermore, genetic load may be largely averted with adaptive dispersal whenever individuals move before selective deaths occur. Thus, to understand the mechanisms driving local adaptation, biologists must account for the extent and nature of nonrandom, genotype-dependent dispersal, and the potential for adaptation via spatial sorting of genotypes.
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Affiliation(s)
- Daniel I Bolnick
- Howard Hughes Medical Institute, Department of Integrative Biology, University of Texas at Austin One University Station C0990, Austin, Texas, 78712, USA
| | - Sarah P Otto
- Department of Zoology, University of British Columbia 6270 University Blvd., Vancouver, BC, V6T 1Z4, Canada
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15
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Roy D, Seehausen O, Nosil P. Sexual dimorphism dominates divergent host plant use in stick insect trophic morphology. BMC Evol Biol 2013; 13:135. [PMID: 23819550 PMCID: PMC3707739 DOI: 10.1186/1471-2148-13-135] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2013] [Accepted: 06/18/2013] [Indexed: 01/27/2023] Open
Abstract
BACKGROUND Clear examples of ecological speciation exist, often involving divergence in trophic morphology. However, substantial variation also exists in how far the ecological speciation process proceeds, potentially linked to the number of ecological axes, traits, or genes subject to divergent selection. In addition, recent studies highlight how differentiation might occur between the sexes, rather than between populations. We examine variation in trophic morphology in two host-plant ecotypes of walking-stick insects (Timema cristinae), known to have diverged in morphological traits related to crypsis and predator avoidance, and to have reached an intermediate point in the ecological speciation process. Here we test how host plant use, sex, and rearing environment affect variation in trophic morphology in this species using traditional multivariate, novel kernel density based and Bayesian morphometric analyses. RESULTS Contrary to expectations, we find limited host-associated divergence in mandible shape. Instead, the main predictor of shape variation is sex, with secondary roles of population of origin and rearing environment. CONCLUSION Our results show that trophic morphology does not strongly contribute to host-adapted ecotype divergence in T. cristinae and that traits can respond to complex selection regimes by diverging along different intraspecific lines, thereby impeding progress toward speciation.
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Affiliation(s)
- Denis Roy
- Great Lakes Institute for Environmental Research, University of Windsor, Windsor, ON N9B 3P4, Canada.
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16
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Flaxman SM, Feder JL, Nosil P. Spatially explicit models of divergence and genome hitchhiking. J Evol Biol 2012; 25:2633-50. [DOI: 10.1111/jeb.12013] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2012] [Revised: 08/24/2012] [Accepted: 09/09/2012] [Indexed: 12/11/2022]
Affiliation(s)
- S. M. Flaxman
- Department of Ecology and Evolutionary Biology; University of Colorado; Boulder CO USA
| | - J. L. Feder
- Department of Biological Sciences; University of Notre Dame; Notre Dame IN USA
| | - P. Nosil
- Department of Ecology and Evolutionary Biology; University of Colorado; Boulder CO USA
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17
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Feder JL, Gejji R, Yeaman S, Nosil P. Establishment of new mutations under divergence and genome hitchhiking. Philos Trans R Soc Lond B Biol Sci 2012; 367:461-74. [PMID: 22201175 DOI: 10.1098/rstb.2011.0256] [Citation(s) in RCA: 108] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Theoretical models addressing genome-wide patterns of divergence during speciation are needed to help us understand the evolutionary processes generating empirical patterns. Here, we examine a critical issue concerning speciation-with-gene flow: to what degree does physical linkage (r < 0.5) of new mutations to already diverged genes aid the build-up of genomic islands of differentiation? We used simulation and analytical approaches to partition the probability of establishment for a new divergently selected mutation when the mutation (i) is the first to arise in an undifferentiated genome (the direct effect of selection), (ii) arises unlinked to any selected loci (r = 0.5), but within a genome that has some already diverged genes (the effect of genome-wide reductions in gene flow for facilitating divergence, which we term 'genome hitchhiking'), and (iii) arises in physical linkage to a diverged locus (divergence hitchhiking). We find that the strength of selection acting directly on a new mutation is generally the most important predictor for establishment, with divergence and genomic hitchhiking having smaller effects. We outline the specific conditions under which divergence and genome hitchhiking can aid mutation establishment. The results generate predictions about genome divergence at different points in the speciation process and avenues for further work.
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Affiliation(s)
- Jeffrey L Feder
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA.
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Iserbyt A, Van Gossum H, Stoks R. Biogeographical survey identifies consistent alternative physiological optima and a minor role for environmental drivers in maintaining a polymorphism. PLoS One 2012; 7:e32648. [PMID: 22384278 PMCID: PMC3287987 DOI: 10.1371/journal.pone.0032648] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2011] [Accepted: 01/28/2012] [Indexed: 11/19/2022] Open
Abstract
The contribution of adaptive mechanisms in maintaining genetic polymorphisms is still debated in many systems. To understand the contribution of selective factors in maintaining polymorphism, we investigated large-scale (>1000 km) geographic variation in morph frequencies and fitness-related physiological traits in the damselfly Nehalennia irene. As fitness-related physiological traits, we investigated investment in immune function (phenoloxidase activity), energy storage and fecundity (abdomen protein and lipid content), and flight muscles (thorax protein content). In the first part of the study, our aim was to identify selective agents maintaining the large-scale spatial variation in morph frequencies. Morph frequencies varied considerably among populations, but, in contrast to expectation, in a geographically unstructured way. Furthermore, frequencies co-varied only weakly with the numerous investigated ecological parameters. This suggests that spatial frequency patterns are driven by stochastic processes, or alternatively, are consequence of highly variable and currently unidentified ecological conditions. In line with this, the investigated ecological parameters did not affect the fitness-related physiological traits differently in both morphs. In the second part of the study, we aimed at identifying trade-offs between fitness-related physiological traits that may contribute to the local maintenance of both colour morphs by defining alternative phenotypic optima, and test the spatial consistency of such trade-off patterns. The female morph with higher levels of phenoloxidase activity had a lower thorax protein content, and vice versa, suggesting a trade-off between investments in immune function and in flight muscles. This physiological trade-off was consistent across the geographical scale studied and supports widespread correlational selection, possibly driven by male harassment, favouring alternative trait combinations in both female morphs.
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Affiliation(s)
- Arne Iserbyt
- Evolutionary Ecology Group, Antwerp University, Antwerp, Belgium.
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Poisot T, Bever JD, Nemri A, Thrall PH, Hochberg ME. A conceptual framework for the evolution of ecological specialisation. Ecol Lett 2011; 14:841-51. [PMID: 21699641 DOI: 10.1111/j.1461-0248.2011.01645.x] [Citation(s) in RCA: 195] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Ecology Letters (2011) 14: 841-851 ABSTRACT: Ecological specialisation concerns all species and underlies many major ecological and evolutionary patterns. Yet its status as a unifying concept is not always appreciated because of its similarity to concepts of the niche, the many levels of biological phenomena to which it applies, and the complexity of the mechanisms influencing it. The evolution of specialisation requires the coupling of constraints on adaptive evolution with covariation of genotype and environmental performance. This covariation itself depends upon organismal properties such as dispersal behaviour and life history and complexity in the environment stemming from factors such as species interactions and spatio-temporal heterogeneity in resources. Here, we develop a view on specialisation that integrates across the range of biological phenomena with the goal of developing a more predictive conceptual framework that specifically accounts for the importance of biotic complexity and coevolutionary events.
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Affiliation(s)
- Timothée Poisot
- Institut des Sciences de l'Evolution, Université Montpellier II, Place Eugène Bataillon, CC065, F-34095 Montpellier Cedex 05, France
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Dolgova O, Rego C, Calabria G, Balanyà J, Pascual M, Rezende EL, Santos M. Genetic constraints for thermal coadaptation in Drosophila subobscura. BMC Evol Biol 2010; 10:363. [PMID: 21108788 PMCID: PMC3003277 DOI: 10.1186/1471-2148-10-363] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2010] [Accepted: 11/25/2010] [Indexed: 11/23/2022] Open
Abstract
Background Behaviour has been traditionally viewed as a driver of subsequent evolution because behavioural adjustments expose organisms to novel environments, which may result in a correlated evolution on other traits. In Drosophila subobscura, thermal preference and heat tolerance are linked to chromosomal inversion polymorphisms that show parallel latitudinal clines worldwide, such that "cold-climate" ("warm-climate") chromosome arrangements collectively favour a coherent response to colder (warmer) settings as flies carrying them prefer colder (warmer) conditions and have lower (higher) knock out temperatures. Yet, it is not clear whether a genetic correlation between thermal preference and heat tolerance can partially underlie such response. Results We have analyzed the genetic basis of thermal preference and heat tolerance using isochromosomal lines in D. subobscura. Chromosome arrangements on the O chromosome were known to have a biometrical effect on thermal preference in a laboratory temperature gradient, and also harbour several genes involved in the heat shock response; in particular, the genes Hsp68 and Hsp70. Our results corroborate that arrangements on chromosome O affect adult thermal preference in a laboratory temperature gradient, with cold-climate Ost carriers displaying a lower thermal preference than their warm-climate O3+4 and O3+4+8 counterparts. However, these chromosome arrangements did not have any effect on adult heat tolerance and, hence, we putatively discard a genetic covariance between both traits arising from linkage disequilibrium between genes affecting thermal preference and candidate genes for heat shock resistance. Nonetheless, a possible association of juvenile thermal preference and heat resistance warrants further analysis. Conclusions Thermal preference and heat tolerance in the isochromosomal lines of D. subobscura appear to be genetically independent, which might potentially prevent a coherent response of behaviour and physiology (i.e., coadaptation) to thermal selection. If this pattern is general to all chromosomes, then any correlation between thermal preference and heat resistance across latitudinal gradients would likely reflect a pattern of correlated selection rather than genetic correlation.
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Affiliation(s)
- Olga Dolgova
- Departament de Genètica i de Microbiologia, Grup de Biologia Evolutiva (GBE), Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona, Spain
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21
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MCKINNON JEFFREYS, PIEROTTI MICHELEER. Colour polymorphism and correlated characters: genetic mechanisms and evolution. Mol Ecol 2010; 19:5101-25. [DOI: 10.1111/j.1365-294x.2010.04846.x] [Citation(s) in RCA: 231] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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22
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Nosil P. ADAPTIVE POPULATION DIVERGENCE IN CRYPTIC COLOR-PATTERN FOLLOWING A REDUCTION IN GENE FLOW. Evolution 2009; 63:1902-12. [DOI: 10.1111/j.1558-5646.2009.00671.x] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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23
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Affiliation(s)
- Patrik Nosil
- Zoology Department and Biodiversity Research Centre, University of British Columbia, Vancouver BC, Canada.
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Vesakoski O, Merilaita S, Jormalainen V. Reckless males, rational females: Dynamic trade-off between food and shelter in the marine isopod Idotea balthica. Behav Processes 2008; 79:175-81. [DOI: 10.1016/j.beproc.2008.07.005] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2008] [Revised: 07/12/2008] [Accepted: 07/13/2008] [Indexed: 11/29/2022]
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25
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NOSIL PATRIK, YUKILEVICH ROMAN. Mechanisms of reinforcement in natural and simulated polymorphic populations. Biol J Linn Soc Lond 2008. [DOI: 10.1111/j.1095-8312.2008.01048.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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26
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Agosta SJ. Fitness consequences of host use in the field: temporal variation in performance and a life history tradeoff in the moth Rothschildia lebeau (Saturniidae). Oecologia 2008; 157:69-82. [DOI: 10.1007/s00442-008-1059-1] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2007] [Accepted: 04/22/2008] [Indexed: 11/30/2022]
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28
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Ecological niche dimensionality and the evolutionary diversification of stick insects. PLoS One 2008; 3:e1907. [PMID: 18382680 PMCID: PMC2270911 DOI: 10.1371/journal.pone.0001907] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2007] [Accepted: 02/27/2008] [Indexed: 11/19/2022] Open
Abstract
The degree of phenotypic divergence and reproductive isolation between taxon pairs can vary quantitatively, and often increases as evolutionary divergence proceeds through various stages, from polymorphism to population differentiation, ecotype and race formation, speciation, and post-speciational divergence. Although divergent natural selection promotes divergence, it does not always result in strong differentiation. For example, divergent selection can fail to complete speciation, and distinct species pairs sometimes collapse (‘speciation in reverse’). Widely-discussed explanations for this variability concern genetic architecture, and the geographic arrangement of populations. A less-explored possibility is that the degree of phenotypic and reproductive divergence between taxon pairs is positively related to the number of ecological niche dimensions (i.e., traits) subject to divergent selection. Some data supporting this idea stem from laboratory experimental evolution studies using Drosophila, but tests from nature are lacking. Here we report results from manipulative field experiments in natural populations of herbivorous Timema stick insects that are consistent with this ‘niche dimensionality’ hypothesis. In such insects, divergent selection between host plants might occur for cryptic colouration (camouflage to evade visual predation), physiology (to detoxify plant chemicals), or both of these niche dimensions. We show that divergent selection on the single niche dimension of cryptic colouration can result in ecotype formation and intermediate levels of phenotypic and reproductive divergence between populations feeding on different hosts. However, greater divergence between a species pair involved divergent selection on both niche dimensions. Although further replication of the trends reported here is required, the results suggest that dimensionality of selection may complement genetic and geographic explanations for the degree of diversification in nature.
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Bolnick DI, Fitzpatrick BM. Sympatric Speciation: Models and Empirical Evidence. ANNUAL REVIEW OF ECOLOGY EVOLUTION AND SYSTEMATICS 2007. [DOI: 10.1146/annurev.ecolsys.38.091206.095804] [Citation(s) in RCA: 537] [Impact Index Per Article: 31.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Daniel I. Bolnick
- Section of Integrative Biology, University of Texas, Austin, Texas 78712;
| | - Benjamin M. Fitzpatrick
- Department of Ecology and Evolutionary Biology, University of Tennessee, Knoxville, Tennessee 37996;
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Nosil P, Egan SP, Funk DJ. Heterogeneous genomic differentiation between walking-stick ecotypes: "isolation by adaptation" and multiple roles for divergent selection. Evolution 2007; 62:316-36. [PMID: 17999721 DOI: 10.1111/j.1558-5646.2007.00299.x] [Citation(s) in RCA: 320] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Genetic differentiation can be highly variable across the genome. For example, loci under divergent selection and those tightly linked to them may exhibit elevated differentiation compared to neutral regions. These represent "outlier loci" whose differentiation exceeds neutral expectations. Adaptive divergence can also increase genome-wide differentiation by promoting general barriers to neutral gene flow, thereby facilitating genomic divergence via genetic drift. This latter process can yield a positive correlation between adaptive phenotypic divergence and neutral genetic differentiation (described here as "isolation-by-adaptation"). Here, we examine both these processes by combining an AFLP genome scan of two host plant ecotypes of Timema cristinae walking-sticks with existing data on adaptive phenotypic divergence and ecological speciation in these insects. We found that about 8% of loci are outliers in multiple population comparisons. Replicated comparisons between population-pairs using the same versus different host species revealed that 1-2% of loci are subject to host-related selection specifically. Locus-specific analyses revealed that up to 10% of putatively neutral (nonoutlier) AFLP loci exhibit significant isolation-by-adaptation. Our results suggest that selection may affect differentiation directly, via linkage, or by facilitating genetic drift. They thus illustrate the varied and sometimes nonintuitive contributions of selection to heterogeneous genomic differentiation.
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Affiliation(s)
- Patrik Nosil
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada.
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Abstract
Migration tends to oppose the effects of divergent natural selection among populations. Numerous theoretical and empirical studies have demonstrated that this migration-selection balance constrains genetic divergence among populations. In contrast, relatively few studies have examined immigration's effects on fitness and natural selection within recipient populations. By constraining local adaptation, migration can lead to reduced fitness, known as a "migration load," which in turn causes persistent natural selection. We develop a simple two-island model of migration-selection balance that, although very general, also reflects the natural history of Timema cristinae walking-stick insects that inhabit two host plant species that favor different cryptic color patterns. We derive theoretical predictions about how migration rates affect the level of maladaptation within populations (measured as the frequency of less-cryptic color-pattern morphs), which in turn determines the selection differential (the within-generation morph frequency change). Using data on color morph frequencies from 25 natural populations, we confirm previous results showing that maladaptation is higher in populations receiving more immigrants. We then present novel evidence that this increased maladaptation leads to larger selection differentials, consistent with our model. Our results provide comparative evidence that immigration elevates the variance in fitness, which in turn leads to larger selection differentials, consistent with Fisher's Theorem of Natural Selection. However, we also find evidence that recurrent adult migration between parapatric populations may tend to obscure the effects of selection.
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Affiliation(s)
- Daniel I Bolnick
- Section of Integrative Biology, University of Texas at Austin, Austin, Texas 78712, USA.
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Abstract
In 1996, Schluter showed that the direction of morphological divergence of closely related species is biased toward the line of least genetic resistance, represented by g(max), the leading eigenvector of the matrix of genetic variance-covariance (the G-matrix). G is used to predict the direction of evolutionary change in natural populations. However, this usage requires that G is sufficiently constant over time to have enough predictive significance. Here, we explore the alternative explanation that G can evolve due to gene flow to conform to the direction of divergence between incipient species. We use computer simulations in a mainland-island migration model with stabilizing selection on two quantitative traits. We show that a high level of gene flow from a mainland population is required to significantly affect the orientation of the G-matrix in an island population. The changes caused by the introgression of the mainland alleles into the island population affect all aspects of the shape of G (size, eccentricity, and orientation) and lead to the alignment of g(max) with the line of divergence between the two populations' phenotypic optima. Those changes decrease with increased correlation in mutational effects and with a correlated selection. Our results suggest that high migration rates, such as those often seen at the intraspecific level, will substantially affect the shape and orientation of G, whereas low migration (e.g., at the interspecific level) is unlikely to substantially affect the evolution of G.
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Affiliation(s)
- Frédéric Guillaume
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada.
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FEDER JEFFREYL, FORBES ANDREWA. Habitat avoidance and speciation for phytophagous insect specialists. Funct Ecol 2007. [DOI: 10.1111/j.1365-2435.2007.01232.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Nosil P. Divergent Host Plant Adaptation and Reproductive Isolation between Ecotypes of Timema cristinae Walking Sticks. Am Nat 2007; 169:151-62. [PMID: 17211800 DOI: 10.1086/510634] [Citation(s) in RCA: 192] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2006] [Accepted: 09/22/2006] [Indexed: 11/03/2022]
Abstract
Theoretical and empirical studies have demonstrated that divergent natural selection can promote the evolution of reproductive isolation. Three unresolved questions concern the types of reproductive barriers involved, the role of geography, and the factors determining the extent of progress toward complete speciation. Here I synthesize studies of Timema cristinae host plant ecotypes to address these issues. The approach is to compare the magnitude of multiple reproductive barriers among different ecological and geographic scenarios, where pairs of populations within each scenario are the unit of replication. Application of this approach to T. cristinae revealed that divergent host adaptation can promote the evolution of diverse reproductive barriers, including those that are not inherently ecological. Gene flow in parapatry tended to constrain divergence, with the notable exception of the reinforcement of sexual isolation. Thus, geography affected progress toward speciation but did not influence all reproductive barriers in the same way. Studies of any single pair of taxa often capture only certain stages of the speciation process. For example, reproductive isolation between T. cristinae ecotypes is incomplete, and so only the stages before the completion of speciation have been examined. Studies of more divergent taxa within the genus are required to determine the factors that complete speciation.
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Affiliation(s)
- Patrik Nosil
- Department of Zoology, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada.
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Nosil P, Crespi BJ, Gries R, Gries G. Natural selection and divergence in mate preference during speciation. Genetica 2006; 129:309-27. [PMID: 16900317 DOI: 10.1007/s10709-006-0013-6] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2005] [Accepted: 04/25/2006] [Indexed: 10/24/2022]
Abstract
Sexual isolation can evolve due to natural selection against hybrids (reinforcement). However, many different forms of hybrid dysfunction, and selective processes that do not involve hybrids, can contribute to the evolution of sexual isolation. Here we review how different selective processes affect the evolution of sexual isolation, describe approaches for distinguishing among them, and assess how they contribute to variation in sexual isolation among populations of Timema cristinae stick-insects. Pairs of allopatric populations of T. cristinae living on different host-plant species exhibit greater sexual isolation than those on the same host, indicating that some sexual isolation has evolved due to host adaptation. Sexual isolation is strongest in regions where populations on different hosts are in geographic contact, a pattern of reproductive character displacement that is indicative of reinforcement. Ecological costs to hybridization do occur but traits under ecological selection (predation) do not co-vary strongly with the probability of between-population mating such that selection on ecological traits is not predicted to produce a strong correlated evolutionary response in mate preference. Moreover, F1 hybrid egg inviability is lacking and the factors contributing to reproductive character displacement require further study. Finally, we show that sexual isolation involves, at least in part, olfactory communication. Our results illustrate how understanding of the evolution of sexual isolation can be enhanced by isolating the roles of diverse ecological and evolutionary processes.
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Affiliation(s)
- Patrik Nosil
- Department of Biological Sciences, Simon Fraser University, Burnaby, BC, Canada.
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