1
|
Bailey RI. Bayesian hybrid index and genomic cline estimation with the R package gghybrid. Mol Ecol Resour 2024; 24:e13910. [PMID: 38063369 DOI: 10.1111/1755-0998.13910] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2023] [Revised: 11/15/2023] [Accepted: 11/24/2023] [Indexed: 01/12/2024]
Abstract
Admixture, the interbreeding of individuals from differentiated source populations, is now known to be a widespread phenomenon. Genomic studies of natural hybridisation can help to answer many questions on the impacts of admixture on adaptive evolution, reproductive isolation, and speciation. When a large variety of admixture proportions between two source populations exist, both geographic and genomic cline analysis are suitable methods for inferring biased, restricted or excessive gene flow at individual loci into the foreign genomic background, providing evidence for reproductive isolation, selection across an environmental transition, balancing selection, and adaptive introgression. Genomic cline analysis replaces geographic location with genome-wide hybrid index and is therefore useable in circumstances that violate geographic cline assumptions. Here, I introduce gghybrid, an R package for simple and flexible Bayesian estimation of Buerkle's hybrid index and Fitzpatrick's logit-logistic genomic clines using bi-allelic data, suitable for both small and large datasets. gghybrid allows any ploidy and uses Structure input file format. It has separate functions for hybrid index and cline estimation, treating each individual and locus respectively as an independent analysis, making it highly parallelisable. Admixture proportions from other software can alternatively be used in cline analysis, alongside parental allele frequencies. Parameters can be fixed and samples pooled for statistical model comparison with AIC or waic. Here, I describe the functions, pipeline, and statistical properties of gghybrid. Simulations reveal that model comparison with waic is preferred, and use of Bayesian posterior distributions and p values to select candidate non-null loci is problematic and should be avoided.
Collapse
Affiliation(s)
- Richard Ian Bailey
- Department of Ecology and Vertebrate Zoology, Faculty of Biology and Environmental Protection, University of Lodz, Łódź, Poland
| |
Collapse
|
2
|
Maldonado-Coelho M, Dos Santos SS, Isler ML, Svensson-Coelho M, Sotelo-Muñoz M, Miyaki CY, Ricklefs RE, Blake JG. Evolutionary and Ecological Processes Underlying Geographic Variation in Innate Bird Songs. Am Nat 2023; 202:E31-E52. [PMID: 37531273 DOI: 10.1086/725016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/04/2023]
Abstract
AbstractEcological and evolutionary processes underlying spatial variation in signals involved in mate recognition and reproductive isolation are crucial to understanding the causes of population divergence and speciation. Here, to test hypotheses concerning the causes of song divergence, we examine how songs of two sister species of Atlantic Forest suboscine birds with innate songs, the Pyriglena fire-eye antbirds, vary across their ranges. Specifically, we evaluated the influence of isolation by distance and introgressive hybridization, as well as morphological and environmental variation, on geographic variation in male songs. Analyses based on 496 male vocalizations from 63 locations across a 2,200-km latitudinal transect revealed clinal changes in the structure of songs and showed that introgressive hybridization increases both the variability and the homogenization of songs in the contact zone between the two species. We also found that isolation by distance, morphological constraints, the environment, and genetic introgression independently predicted song variation across geographic space. Our study shows the importance of an integrative approach that investigates the roles of distinct ecological and evolutionary processes that influence acoustic signal evolution.
Collapse
|
3
|
Noguerales V, Ortego J. Genomic evidence of speciation by fusion in a recent radiation of grasshoppers. Evolution 2022; 76:2618-2633. [PMID: 35695020 PMCID: PMC9796961 DOI: 10.1111/evo.14508] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2021] [Revised: 03/22/2022] [Accepted: 04/02/2022] [Indexed: 01/22/2023]
Abstract
Postdivergence gene flow can trigger a number of creative evolutionary outcomes, ranging from the transfer of beneficial alleles across species boundaries (i.e., adaptive introgression) to the formation of new species (i.e., hybrid speciation). Although neutral and adaptive introgression has been broadly documented in nature, hybrid speciation is assumed to be rare and the evolutionary and ecological context facilitating this phenomenon still remains controversial. Through combining genomic and phenotypic data, we evaluate the hypothesis that the dual feeding regime (based on both scrub legumes and gramineous herbs) of the taxonomically controversial grasshopper Chorthippus saulcyi algoaldensis resulted from hybridization between the sister taxa C. binotatus (that exclusively feeds on scrub legumes) and C. saulcyi (that only feeds on gramineous herbs). Genetic clustering analyses and inferences from coalescent-based demographic simulations confirm that C. s. algoaldensis represents an independently evolving lineage and support the ancient hybrid origin of this taxon (about 1.4 Ma), which sheds light on its uncertain phylogenetic position and might explain its broader trophic niche. We propose a Pleistocene hybrid speciation model where range shifts resulting from climatic oscillations can promote the formation of hybrid swarms and facilitate their long-term persistence through geographic isolation from parental forms in topographically complex landscapes.
Collapse
Affiliation(s)
- Víctor Noguerales
- Department of Biological SciencesUniversity of CyprusNicosia1678Cyprus,Island Ecology and Evolution GroupInstituto de Productos Naturales y Agrobiología (IPNA‐CSIC)San Cristóbal de La Laguna38206Spain
| | - Joaquín Ortego
- Department of Integrative EcologyEstación Biológica de Doñana (EBD‐CSIC)Sevilla41092Spain
| |
Collapse
|
4
|
Tarasova T, Tishechkin D, Vedenina V. Songs and morphology in three species of the Chorthippusbiguttulus group (Orthoptera, Acrididae, Gomphocerinae) in Russia and adjacent countries. Zookeys 2021; 1073:21-53. [PMID: 34949950 PMCID: PMC8648708 DOI: 10.3897/zookeys.1073.75539] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Accepted: 10/30/2021] [Indexed: 11/23/2022] Open
Abstract
Songs and morphology are compared between Chorthippusmiramae (Vorontsovsky, 1928) that was previously named as C.porphyropterus and two other closely related species, C.brunneus (Thunberg, 1815) and C.maritimus Mistshenko, 1951. We compare them because the calling song of C.miramae was previously shown to have song elements similar to those of other two species. One morphological character, the length of stridulatory file, appeared to be the best character to distinguish between all three species. For C.maritimus and C.miramae, we present the morphological descriptions since they are absent in the literature. We also establish the synonymy C.maritimus = C.bornhalmi Harz, 1971, syn. n. = C.biguttuluseximius Mistshenko, 1951, syn. n. In the song analysis, we analyse not only the sound but also the leg-movement pattern, which is very helpful to find a homology between various song elements. We show that the calling song of C.miramae usually contains two elements, one element being similar to the C.brunneus calling song, and another – to the C.maritimus calling song. Despite some similarities, the calling song elements in C.miramae have some peculiarities. The courtship song of C.miramae is similar to the C.brunneus song, whereas the rivalry songs of C.miramae comprise both the maritimus-like elements and the unique ones. C.miramae generally demonstrates a richer song repertoire than the other two species.
Collapse
Affiliation(s)
- Tatiana Tarasova
- Institute for Information Transmission Problems, Russian Academy of Sciences, Bolshoy Karetny per.19, Moscow 127051 Russia Institute for Information Transmission Problems, Russian Academy of Sciences Moscow Russia
| | - Dmitry Tishechkin
- Department of Entomology, Faculty of Biology, Moscow State University, Leninskie Gory, Moscow 119234 Russia Moscow State University Moscow Russia
| | - Varvara Vedenina
- Institute for Information Transmission Problems, Russian Academy of Sciences, Bolshoy Karetny per.19, Moscow 127051 Russia Institute for Information Transmission Problems, Russian Academy of Sciences Moscow Russia
| |
Collapse
|
5
|
Akopyan M, Gompert Z, Klonoski K, Vega A, Kaiser K, Mackelprang R, Rosenblum EB, Robertson JM. Genetic and phenotypic evidence of a contact zone between divergent colour morphs of the iconic red-eyed treefrog. Mol Ecol 2020; 29:4442-4456. [PMID: 32945036 DOI: 10.1111/mec.15639] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Revised: 07/21/2020] [Accepted: 09/03/2020] [Indexed: 12/28/2022]
Abstract
Hybrid zones act as natural laboratories where divergent genomes interact, providing powerful systems for examining the evolutionary processes underlying biological diversity. In this study, we characterized patterns of genomic and phenotypic variation resulting from hybridization between divergent intraspecific lineages of the Neotropical red-eyed treefrog (Agalychnis callidryas). We found genetic evidence of a newly discovered contact zone and phenotypic novelty in leg colour-a trait suspected to play a role in mediating assortative mating in this species. Analysis of hybrid ancestry revealed an abundance of later-generation Fn individuals, suggesting persistence of hybrids in the contact zone. Hybrids are predominantly of southern ancestry but are phenotypically more similar to northern populations. Genome-wide association mapping revealed QTL with measurable effects on leg-colour variation, but further work is required to dissect the architecture of this trait and establish causal links. Further, genomic cline analyses indicated substantial variation in patterns of introgression across the genome. Directional introgression of loci associated with different aspects of leg colour are inherited from each parental lineage, creating a distinct hybrid colour pattern. We show that hybridization can generate new phenotypes, revealing the evolutionary processes that potentially underlie patterns of phenotypic diversity in this iconic polytypic frog. Our study is consistent with a role of hybridization and sexual selection in lineage diversification, evolutionary processes that have been implicated in accelerating divergence in the most phenotypically diverse species.
Collapse
Affiliation(s)
- Maria Akopyan
- Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY, USA.,Department of Biology, California State University, Northridge, CA, USA
| | | | - Karina Klonoski
- Department of Environmental Science, Policy, and Management, University of California, Berkeley, CA, USA
| | | | - Kristine Kaiser
- Department of Biology, California State University, Northridge, CA, USA
| | | | - Erica Bree Rosenblum
- Department of Environmental Science, Policy, and Management, University of California, Berkeley, CA, USA
| | | |
Collapse
|
6
|
McEntee JP, Burleigh JG, Singhal S. Dispersal Predicts Hybrid Zone Widths across Animal Diversity: Implications for Species Borders under Incomplete Reproductive Isolation. Am Nat 2020; 196:9-28. [PMID: 32552108 DOI: 10.1086/709109] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Hybrid zones occur as range boundaries for many animal taxa. One model for how hybrid zones form and stabilize is the tension zone model, a version of which predicts that hybrid zone widths are determined by a balance between random dispersal into hybrid zones and selection against hybrids. Here, we examine whether random dispersal and proxies for selection against hybrids (genetic distances between hybridizing pairs) can explain variation in hybrid zone widths across 131 hybridizing pairs of animals. We show that these factors alone can explain ∼40% of the variation in zone width among animal hybrid zones, with dispersal explaining far more of the variation than genetic distances. Patterns within clades were idiosyncratic. Genetic distances predicted hybrid zone widths particularly well for reptiles, while this relationship was opposite tension zone predictions in birds. Last, the data suggest that dispersal and molecular divergence set lower bounds on hybrid zone widths in animals, indicating that there are geographic restrictions on hybrid zone formation. Overall, our analyses reinforce the fundamental importance of dispersal in hybrid zone formation and more generally in the ecology of range boundaries.
Collapse
|
7
|
Billerman SM, Cicero C, Bowie RCK, Carling MD. Phenotypic and genetic introgression across a moving woodpecker hybrid zone. Mol Ecol 2019; 28:1692-1708. [DOI: 10.1111/mec.15043] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2017] [Accepted: 01/22/2019] [Indexed: 01/05/2023]
Affiliation(s)
- Shawn M. Billerman
- Department of Zoology and Physiology University of Wyoming Laramie Wyoming
- Program in Ecology University of Wyoming Laramie Wyoming
| | - Carla Cicero
- Museum of Vertebrate Zoology University of California Berkeley California
| | - Rauri C. K. Bowie
- Museum of Vertebrate Zoology University of California Berkeley California
- Department of Integrative Biology University of California Berkeley California
| | - Matthew D. Carling
- Department of Zoology and Physiology University of Wyoming Laramie Wyoming
- Program in Ecology University of Wyoming Laramie Wyoming
| |
Collapse
|
8
|
Lipshutz SE, Meier JI, Derryberry GE, Miller MJ, Seehausen O, Derryberry EP. Differential introgression of a female competitive trait in a hybrid zone between sex-role reversed species. Evolution 2019; 73:188-201. [PMID: 30597557 DOI: 10.1111/evo.13675] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2018] [Accepted: 12/10/2018] [Indexed: 01/04/2023]
Abstract
Mating behavior between recently diverged species in secondary contact can impede or promote reproductive isolation. Traditionally, researchers focus on the importance of female mate choice and male-male competition in maintaining or eroding species barriers. Although female-female competition is widespread, little is known about its role in the speciation process. Here, we investigate a case of interspecific female competition and its influence on patterns of phenotypic and genetic introgression between species. We examine a hybrid zone between sex-role reversed, Neotropical shorebird species, the northern jacana (Jacana spinosa) and wattled jacana (J. jacana), in which female-female competition is a major determinant of reproductive success. Previous work found that females of the more aggressive and larger species, J. spinosa, disproportionately mother hybrid offspring, potentially by monopolizing breeding territories in sympatry with J. jacana. We find a cline shift of female body mass relative to the genetic center of the hybrid zone, consistent with asymmetric introgression of this competitive trait. We suggest that divergence in sexual characteristics between sex-role reversed females can influence patterns of gene flow upon secondary contact, similar to males in systems with more typical sex roles.
Collapse
Affiliation(s)
- Sara E Lipshutz
- Department of Ecology and Evolutionary Biology, Tulane University, New Orleans, Louisiana, 70118.,Department of Ecology and Evolutionary Biology, University of Tennessee, Knoxville, Tennessee, 37996.,Institute of Ecology and Evolution, University of Bern, Switzerland
| | - Joana I Meier
- Institute of Ecology and Evolution, University of Bern, Switzerland.,Fish Ecology and Evolution, Eawag Center for Ecology, Evolution and Biogeochemistry, Kastanienbaum, Switzerland
| | - Graham E Derryberry
- Museum of Natural Science, Louisiana State University, Baton Rouge, Louisiana, 70803
| | - Matthew J Miller
- Smithsonian Tropical Research Institute, Balboa, Republic of Panama.,Sam Noble Oklahoma Museum and Department of Biology, University of Oklahoma, Norman, Oklahoma, 73019
| | - Ole Seehausen
- Institute of Ecology and Evolution, University of Bern, Switzerland.,Fish Ecology and Evolution, Eawag Center for Ecology, Evolution and Biogeochemistry, Kastanienbaum, Switzerland
| | - Elizabeth P Derryberry
- Department of Ecology and Evolutionary Biology, Tulane University, New Orleans, Louisiana, 70118.,Department of Ecology and Evolutionary Biology, University of Tennessee, Knoxville, Tennessee, 37996
| |
Collapse
|
9
|
Tishechkin DY, Vedenina VY. Acoustic signals in insects: A reproductive barrier and a taxonomic character. ACTA ACUST UNITED AC 2017. [DOI: 10.1134/s0013873816090013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
|
10
|
Sradnick J, Klöpfel A, Elsner N, Vedenina V. Variation in complex mating signals in an "island" hybrid zone between Stenobothrus grasshopper species. Ecol Evol 2016; 6:5057-75. [PMID: 27547333 PMCID: PMC4979727 DOI: 10.1002/ece3.2265] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2016] [Revised: 05/24/2016] [Accepted: 05/25/2016] [Indexed: 11/09/2022] Open
Abstract
Two grasshopper species Stenobothrus rubicundus and S. clavatus were previously shown to meet in a narrow hybrid zone on Mount Tomaros in northern Greece. The species are remarkable for their complex courtship songs accompanied by conspicuous movements of antennae and wings. We analyzed variations in forewing morphology, antenna shape, and courtship song across the hybrid zone using a geographic information system, and we documented three contact zones on Mount Tomaros. All male traits and female wings show abrupt transitions across the contact zones, suggesting that these traits are driven by selection rather than by drift. Male clines in antennae are displaced toward S. clavatus, whereas all clines in wings are displaced toward S. rubicundus. We explain cline discordance as depending on sexual selection via female choice. The high covariance between wings and antennae found in the centers of all contact zones results from high levels of linkage disequilibria among the underlying loci, which in turn more likely results from assortative mating than from selection against hybrids. The covariance is found to be higher in clavatus-like than rubicundus-like populations, which implies asymmetric assortative mating in parental-like sites of the hybrid zone and a movement of the hybrid zone in favor of S. clavatus.
Collapse
Affiliation(s)
- Jan Sradnick
- Department of Neurobiology Johann-Friedrich-Blumenbach-Institute Göttingen Germany; Present address: Division of Nephrology Department of Internal Medicine III Dresden University of Technology Dresden Germany
| | - Anja Klöpfel
- Department of Neurobiology Johann-Friedrich-Blumenbach-Institute Göttingen Germany
| | - Norbert Elsner
- Department of Neurobiology Johann-Friedrich-Blumenbach-Institute Göttingen Germany
| | - Varvara Vedenina
- Institute for Information Transmission Problems Russian Academy of Sciences Bolshoy Karetny per. 19 Moscow 127051 Russia
| |
Collapse
|
11
|
McKenzie JL, Dhillon RS, Schulte PM. Evidence for a bimodal distribution of hybrid indices in a hybrid zone with high admixture. ROYAL SOCIETY OPEN SCIENCE 2015; 2:150285. [PMID: 27019720 PMCID: PMC4807441 DOI: 10.1098/rsos.150285] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2015] [Accepted: 11/09/2015] [Indexed: 05/30/2023]
Abstract
The genetic structure of a hybrid zone can provide insights into the relative roles of the various factors that maintain the zone. Here, we use a multilocus approach to characterize a hybrid zone between two subspecies of killifish (Fundulus heteroclitus, Walbaum 1792) found along the Atlantic coast of North America. We first analysed clinal variation along the Atlantic coast using a single-nucleotide polymorphism in the mitochondrial DNA (mtDNA) displacement loop (D-loop) and a panel of nine nuclear microsatellite markers. A model constraining all clines to the same width and centre was not significantly different from a model in which the clines were allowed to vary independently. Locus-by-locus analysis indicated that the majority of nuclear clines shared the same centre as the mtDNA cline, and the widths of these clines were also narrower than that predicted by a neutral model, suggesting that selection is operating to maintain the hybrid zone. However, two of the nuclear clines had widths greater than the neutral prediction and had centres that were displaced relative to the mtDNA cline centre. We also found that a marsh located near the centre of the mtDNA cline demonstrated a bimodal distribution of nuclear hybrid index values, suggesting a deficit of first-generation hybrids and backcrossed genotypes. Thus, selection against hybrid genotypes may be playing a role in maintaining this hybrid zone and the associated steep nuclear and mtDNA clines.
Collapse
Affiliation(s)
- Jessica L. McKenzie
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
- Centre for Aquaculture and Environmental Research, Fisheries and Oceans Canada, West Vancouver, British Columbia, Canada
| | - Rashpal S. Dhillon
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Patricia M. Schulte
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
| |
Collapse
|
12
|
Laiolo P, Illera JC, Obeso JR. Local climate determines intra- and interspecific variation in sexual size dimorphism in mountain grasshopper communities. J Evol Biol 2013; 26:2171-83. [PMID: 23937477 DOI: 10.1111/jeb.12213] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2013] [Revised: 05/16/2013] [Accepted: 06/13/2013] [Indexed: 11/26/2022]
Abstract
The climate is often evoked to explain broad-scale clines of body size, yet its involvement in the processes that generate size inequality in the two sexes (sexual size dimorphism) remains elusive. Here, we analyse climatic clines of sexual size dimorphism along a wide elevation gradient (i) among grasshopper species in a phylogenetically controlled scenario and (ii) within species differing in distribution and cold tolerance, to highlight patterns generated at different time scales, mainly evolutionary (among species or higher taxa) and ontogenetic or microevolutionary (within species). At the interspecific level, grasshoppers were slightly smaller and less dimorphic at high elevations. These clines were associated with gradients of precipitation and sun exposure, which are likely indicators of other factors that directly exert selective pressures, such as resource availability and conditions for effective thermoregulation. Within species, we found a positive effect of temperature and a negative effect of elevation on body size, especially on condition-dependent measures of body size (total body length rather than hind femur length) and in species inhabiting the highest elevations. In spite of a certain degree of species-specific variation, females tended to adjust their body size more often than males, suggesting that body size in females can evolve faster among species and can be more plastic or dependent on nutritional conditions within species living in adverse climates. Natural selection on female body size may therefore prevail over sexual selection on male body size in alpine environments, and abiotic factors may trigger consistent phenotypic patterns across taxonomic scales.
Collapse
Affiliation(s)
- P Laiolo
- Research Unit of Biodiversity (UO, CSIC, PA), Oviedo University, Mieres, Spain
| | | | | |
Collapse
|
13
|
Moody ML, Rieseberg LH. Sorting through the chaff, nDNA gene trees for phylogenetic inference and hybrid identification of annual sunflowers (Helianthus sect. Helianthus). Mol Phylogenet Evol 2012; 64:145-55. [PMID: 22724134 DOI: 10.1016/j.ympev.2012.03.012] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
The annual sunflowers (Helianthus sect. Helianthus) present a formidable challenge for phylogenetic inference because of ancient hybrid speciation, recent introgression, and suspected issues with deep coalescence. Here we analyze sequence data from 11 nuclear DNA (nDNA) genes for multiple genotypes of species within the section to (1) reconstruct the phylogeny of this group, (2) explore the utility of nDNA gene trees for detecting hybrid speciation and introgression; and (3) test an empirical method of hybrid identification based on the phylogenetic congruence of nDNA gene trees from tightly linked genes. We uncovered considerable topological heterogeneity among gene trees with or without three previously identified hybrid species included in the analyses, as well as a general lack of reciprocal monophyly of species. Nonetheless, partitioned Bayesian analyses provided strong support for the reciprocal monophyly of all species except H. annuus (0.89 PP), the most widespread and abundant annual sunflower. Previous hypotheses of relationships among taxa were generally strongly supported (1.0 PP), except among taxa typically associated with H. annuus, apparently due to the paraphyly of the latter in all gene trees. While the individual nDNA gene trees provided a useful means for detecting recent hybridization, identification of ancient hybridization was problematic for all ancient hybrid species, even when linkage was considered. We discuss biological factors that affect the efficacy of phylogenetic methods for hybrid identification.
Collapse
Affiliation(s)
- Michael L Moody
- School of Plant Biology, University of Western Australia, Crawley, WA 6009, Australia.
| | | |
Collapse
|
14
|
Vedenina V, Sradnick J, Klöpfel A, Elsner N. A narrow hybrid zone between the grasshoppers Stenobothrus clavatus and Stenobothrus rubicundus: courtship song analysis. Biol J Linn Soc Lond 2012. [DOI: 10.1111/j.1095-8312.2012.01935.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Varvara Vedenina
- Institute for Information Transmission Problems; Russian Academy of Sciences; Bolshoy Karetny pereulok 19; 127994; Moscow; Russia
| | - Jan Sradnick
- Department of Neurobiology; Johann-Friedrich-Blumenbach-Institute; Berliner Strasse 28; D-37073; Göttingen; Germany
| | - Anja Klöpfel
- Department of Neurobiology; Johann-Friedrich-Blumenbach-Institute; Berliner Strasse 28; D-37073; Göttingen; Germany
| | - Norbert Elsner
- Department of Neurobiology; Johann-Friedrich-Blumenbach-Institute; Berliner Strasse 28; D-37073; Göttingen; Germany
| |
Collapse
|
15
|
Bailey RI, Saldamando-Benjumea CI, Tatsuta H, Butlin RK. Habitat association and seasonality in a mosaic and bimodal hybrid zone between Chorthippus brunneus and C. jacobsi (Orthoptera: Acrididae). PLoS One 2012; 7:e37684. [PMID: 22675485 PMCID: PMC3366992 DOI: 10.1371/journal.pone.0037684] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2011] [Accepted: 04/26/2012] [Indexed: 11/18/2022] Open
Abstract
Understanding why some hybrid zones are bimodal and others unimodal can aid in identifying barriers to gene exchange following secondary contact. The hybrid zone between the grasshoppers Chorthippus brunneus and C. jacobsi contains a mix of allopatric parental populations and inter-mingled bimodal and unimodal sympatric populations, and provides an ideal system to examine the roles of local selection and gene flow between populations in maintaining bimodality. However, it is first necessary to confirm, over a larger spatial scale, previously identified associations between population composition and season and habitat. Here we use cline-fitting of one morphological and one song trait along two valley transects, and intervening mountains, to confirm previously identified habitat associations (mountain versus valley) and seasonal changes in population composition. As expected from previous findings of studies on a smaller spatial scale, C. jacobsi dominated mountain habitats and mixed populations dominated valleys, and C. brunneus became more prevalent in August. Controlling for habitat and incorporating into the analysis seasonal changes in cline parameters and the standard errors of parental trait values revealed wider clines than previous studies (best estimates of 6.4 to 24.5 km in our study versus 2.8 to 4.7 km in previous studies) and increased percentage of trait variance explained (52.7% and 61.5% for transects 1 and 2 respectively, versus 17.6%). Revealing such strong and consistent patterns within a complex hybrid zone will allow more focused examination of the causes of variation in bimodality in mixed populations, in particular the roles of local selection versus habitat heterogeneity and gene flow between differentiated populations.
Collapse
Affiliation(s)
- Richard I Bailey
- Centre for Ecological and Evolutionary Synthesis, Department of Biology, University of Oslo, Oslo, Norway.
| | | | | | | |
Collapse
|
16
|
Bímová BV, Macholán M, Baird SJE, Munclinger P, Dufková P, Laukaitis CM, Karn RC, Luzynski K, Tucker PK, Piálek J. Reinforcement selection acting on the European house mouse hybrid zone. Mol Ecol 2011; 20:2403-24. [PMID: 21521395 DOI: 10.1111/j.1365-294x.2011.05106.x] [Citation(s) in RCA: 85] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Behavioural isolation may lead to complete speciation when partial postzygotic isolation acts in the presence of divergent-specific mate-recognition systems. These conditions exist where Mus musculus musculus and M. m. domesticus come into contact and hybridize. We studied two mate-recognition signal systems, based on urinary and salivary proteins, across a Central European portion of the mouse hybrid zone. Introgression of the genomic regions responsible for these signals: the major urinary proteins (MUPs) and androgen binding proteins (ABPs), respectively, was compared to introgression at loci assumed to be nearly neutral and those under selection against hybridization. The preference of individuals taken from across the zone regarding these signals was measured in Y mazes, and we develop a model for the analysis of the transition of such traits under reinforcement selection. The strongest assortative preferences were found in males for urine and females for ABP. Clinal analyses confirm nearly neutral introgression of an Abp locus and two loci closely linked to the Abp gene cluster, whereas two markers flanking the Mup gene region reveal unexpected introgression. Geographic change in the preference traits matches our reinforcement selection model significantly better than standard cline models. Our study confirms that behavioural barriers are important components of reproductive isolation between the house mouse subspecies.
Collapse
Affiliation(s)
- Barbora Vošlajerová Bímová
- Department of Population Biology, Institute of Vertebrate Biology, Academy of Sciences of the Czech Republic, Brno, Czech Republic
| | | | | | | | | | | | | | | | | | | |
Collapse
|
17
|
VEDENINA VARVARA. Variation in complex courtship traits across a hybrid zone between grasshopper species of the Chorthippus albomarginatus group. Biol J Linn Soc Lond 2011. [DOI: 10.1111/j.1095-8312.2010.01566.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
|
18
|
Gompert Z, Lucas LK, Fordyce JA, Forister ML, Nice CC. Secondary contact between Lycaeides idas and L. melissa in the Rocky Mountains: extensive admixture and a patchy hybrid zone. Mol Ecol 2010; 19:3171-92. [DOI: 10.1111/j.1365-294x.2010.04727.x] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
|
19
|
MUÑOZ AG, SALAZAR C, CASTAÑO J, JIGGINS CD, LINARES M. Multiple sources of reproductive isolation in a bimodal butterfly hybrid zone. J Evol Biol 2010; 23:1312-20. [DOI: 10.1111/j.1420-9101.2010.02001.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
20
|
Berger D, Chobanov DP, Mayer F. Interglacial refugia and range shifts of the alpine grasshopper Stenobothrus cotticus (Orthoptera: Acrididae: Gomphocerinae). ORG DIVERS EVOL 2010. [DOI: 10.1007/s13127-010-0004-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
|
21
|
Abstract
The spatial genetic composition of hybrid zones exhibits a range of possible patterns, with many characterized by patchy distributions. While several hypothetical explanations exist for the maintenance of these "mosaic" hybrid zones, they remain virtually unexplored theoretically. Using computer simulations we investigate the roles of dispersal and assortative mating in the formation and persistence of hybrid zone structure. To quantify mosaic structure we develop a likelihood method, which we apply to simulation and empirical data. We find that long distance dispersal can lead to a patchy distribution that assortative mating can then reinforce, ultimately producing a mosaic capable of persisting over evolutionarily significant periods of time. By reducing the mating success of rare males, assortative mating creates a positive within-patch frequency-dependent selective pressure. Selection against heterozygotes can similarly create a rare-type disadvantage and we show that it can also preserve structure. We find that mosaic structure is maintained across a range of assumptions regarding the form and strength of assortative mating. Interestingly, we find that higher levels of mosaic structure are sometimes observed for intermediate assortment strengths. The high incidence of assortment documented in hybrid zones suggests that it may play a key role in stabilizing their form and structure.
Collapse
Affiliation(s)
- Leithen K M'Gonigle
- Department of Zoology, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
| | | |
Collapse
|
22
|
Brennan AC, Bridle JR, Wang AL, Hiscock SJ, Abbott RJ. Adaptation and selection in the Senecio (Asteraceae) hybrid zone on Mount Etna, Sicily. THE NEW PHYTOLOGIST 2009; 183:702-717. [PMID: 19594693 DOI: 10.1111/j.1469-8137.2009.02944.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Hybrid zone theory provides a powerful theoretical framework for measuring and testing gene flow and selection. The Senecio aethnensis and Senecio chrysanthemifolius hybrid zone on Mount Etna, Sicily, was investigated to identify phenotypic traits under divergent selection and to assess the contributions of intrinsic and extrinsic selection against hybrids to hybrid zone maintenance. Senecio samples from 14 sites across Mount Etna were analyzed for 24 quantitative traits classified into four groups (QTGs), six allozymes and seven simple sequence repeat (SSR) loci to describe patterns of variation throughout the hybrid zone. Narrower cline widths or shifts in cline centre position were observed for three QTGs relative to the molecular clines, indicating that these traits are likely to be under extrinsic environmental selection. Altitude was key to describing species distributions, but dispersal and intrinsic selection against hybrids explained patterns at smaller spatial scales. The hybrid zone was characterized by strong selection against hybrids, high dispersal rates, recent species contact and few loci differentiating QTGs based on indirect measures. These results support the hypothesis that extrinsic and intrinsic selection against hybrids maintains the hybrid zone and species distinctiveness despite gene flow between the two Senecio species on Mount Etna.
Collapse
Affiliation(s)
- Adrian C Brennan
- Sir Harold Mitchell Building, School of Biology, University of St Andrews, St Andrews, Fife KY16 9TH, UK
| | - Jon R Bridle
- School of Biological Sciences, University of Bristol, Bristol, BS8 1UG, UK
| | - Ai-Lan Wang
- Sir Harold Mitchell Building, School of Biology, University of St Andrews, St Andrews, Fife KY16 9TH, UK
- Key Laboratory of Arid and Grassland Ecology, Lanzhou University, Lanzhou, Gansu 730000, China
| | - Simon J Hiscock
- School of Biological Sciences, University of Bristol, Bristol, BS8 1UG, UK
| | - Richard J Abbott
- Sir Harold Mitchell Building, School of Biology, University of St Andrews, St Andrews, Fife KY16 9TH, UK
| |
Collapse
|
23
|
Gay L, Crochet PA, Bell DA, Lenormand T. COMPARING CLINES ON MOLECULAR AND PHENOTYPIC TRAITS IN HYBRID ZONES: A WINDOW ON TENSION ZONE MODELS. Evolution 2008; 62:2789-806. [PMID: 18752618 DOI: 10.1111/j.1558-5646.2008.00491.x] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Laurène Gay
- CEFE-CNRS, UMR 5175, 1919 route de Mende, F-34293 Montpellier cedex 5, France.
| | | | | | | |
Collapse
|
24
|
Yanchukov A, Hofman S, Szymura JM, Mezhzherin SV, Morozov‐Leonov SY, Barton NH, Nürnberger B. HYBRIDIZATION OFBOMBINA BOMBINAANDB. VARIEGATA(ANURA, DISCOGLOSSIDAE) AT A SHARP ECOTONE IN WESTERN UKRAINE: COMPARISONS ACROSS TRANSECTS AND OVER TIME. Evolution 2007. [DOI: 10.1111/j.0014-3820.2006.tb01139.x] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Alexey Yanchukov
- Schmalhausen Institute of Zoology, National Academy of Sciences of Ukraine, B. Khmelnitzkogo Str. 15, 01601 Kiev, Ukraine
- Department of Comparative Anatomy, Jagiellonian University, Ingardena 6,30–0601 Kraków, Poland
- Institute of Evolutionary Biology, University of Edinburgh, West Mains Road, Edinburgh EH9 3JT, Scotland
- Department Biologie II, Ludwig‐Maximilians‐Universität München, Grosshaderner Str. 2, 82152 Planegg‐Martinsried, Germany
| | - Sebastian Hofman
- Department of Comparative Anatomy, Jagiellonian University, Ingardena 6,30–0601 Kraków, Poland
| | - Jacek M. Szymura
- Department of Comparative Anatomy, Jagiellonian University, Ingardena 6,30–0601 Kraków, Poland
| | - Sergey V. Mezhzherin
- Schmalhausen Institute of Zoology, National Academy of Sciences of Ukraine, B. Khmelnitzkogo Str. 15, 01601 Kiev, Ukraine
| | - Sviatoslav Y. Morozov‐Leonov
- Schmalhausen Institute of Zoology, National Academy of Sciences of Ukraine, B. Khmelnitzkogo Str. 15, 01601 Kiev, Ukraine
| | - Nicholas H. Barton
- Institute of Evolutionary Biology, University of Edinburgh, West Mains Road, Edinburgh EH9 3JT, Scotland
| | - Beate Nürnberger
- Department Biologie II, Ludwig‐Maximilians‐Universität München, Grosshaderner Str. 2, 82152 Planegg‐Martinsried, Germany
| |
Collapse
|
25
|
Gottsberger B, Mayer F. Behavioral sterility of hybrid males in acoustically communicating grasshoppers (Acrididae, Gomphocerinae). J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2007; 193:703-14. [PMID: 17440734 DOI: 10.1007/s00359-007-0225-y] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2007] [Revised: 03/30/2007] [Accepted: 03/31/2007] [Indexed: 11/26/2022]
Abstract
The effectiveness of hybridization barriers determines whether two species remain reproductively isolated when their populations come into contact. We investigated acoustic mating signals and associated leg movements responsible for song creation of hybrids between the grasshopper species Chorthippus biguttulus and C. brunneus to study whether and how songs of male hybrids contribute to reproductive isolation between these sympatrically occurring species. Songs of F1, F2, and backcross hybrids were intermediate between those of both parental species in terms phrase number and duration. In contrast, species-specific syllable structure within phrases was largely lost in hybrids and was produced, if at all, in an irregular and imperfect manner. These divergences in inheritance of different song parameters are likely the result of incompatibility of neuronal networks that control stridulatory leg movements in hybrids. It is highly probable that songs of hybrid males are unattractive to females of either parental species because they are intermediate in terms of phrase duration and lack a clear syllable structure. Males of various hybrid types (F1, F2, and backcrosses) are behaviorally sterile because their songs fail to attract mates.
Collapse
Affiliation(s)
- Brigitte Gottsberger
- Department of Zoology II, University of Erlangen-Nürnberg, Staudtstrasse 5, Erlangen, Germany.
| | | |
Collapse
|
26
|
Olafsdóttir GA, Snorrason SS, Ritchie MG. Morphological and genetic divergence of intralacustrine stickleback morphs in Iceland: a case for selective differentiation? J Evol Biol 2007; 20:603-16. [PMID: 17305827 DOI: 10.1111/j.1420-9101.2006.01250.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The evolutionary processes involved in population divergence and local adaptation are poorly understood. Theory predicts that divergence of adjacent populations is possible but depends on several factors including gene flow, divergent selection, population size and the number of genes involved in divergence and their distribution on the genome. We analyse variation in neutral markers, markers linked to putative quantitative trait loci and morphological traits in a recent (<10000 years) zone of primary divergence between stickleback morphs in Lake Thingvallavatn, Iceland. Environmental factors, especially predation, are clearly implicated in reducing gene flow between morphs. There is continuous morphological and genetic variation between habitats with a zone centre similar to secondary contact zones. Individual microsatellite loci are implicated as being linked to adaptive variation by direct tests as well as by differences in cline shape. Patterns of linkage disequilibria indicate that the morphs have diverged at several loci. This divergence shows parallels and differences with the well-studied limnetic-benthic stickleback morphs, both in phenotypic divergence and at the genomic level.
Collapse
Affiliation(s)
- G A Olafsdóttir
- Department of Environmental and Evolutionary Biology, University of St Andrews, St Andrews, UK.
| | | | | |
Collapse
|
27
|
Bridle JR, Saldamando CI, Koning W, Butlin RK. Assortative preferences and discrimination by females against hybrid male song in the grasshoppers Chorthippus brunneus and Chorthippus jacobsi (Orthoptera: Acrididae). J Evol Biol 2006; 19:1248-56. [PMID: 16780525 DOI: 10.1111/j.1420-9101.2006.01080.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The grasshoppers Chorthippus brunneus and Chorthippus jacobsi are highly differentiated for male mating signals, and form a mosaic hybrid zone in northern Spain. At some sites within this zone, many hybrids are observed. At others, few hybrids are observed. Such bimodal sites may reflect recent contacts between parental genotypes, or local variation in levels of assortative mating or selection against hybrids. Playback of 12 parental and F1 male songs to 296 parental and hybrid females revealed positive assortative preferences in C. brunneus and C. jacobsi females, supporting a direct role of male mating signals in female choice. However, all female genotypic classes showed reduced responsiveness to F1 male songs. Such sexual selection against hybrids is consistent with the narrow cline width observed in the field for song characters relative to morphology. These results have implications for the genetic structure of the hybrid zone and for models of speciation by reinforcement.
Collapse
Affiliation(s)
- J R Bridle
- Institute of Zoology, Zoological Society of London, Regent's Park, London, UK.
| | | | | | | |
Collapse
|
28
|
Yanchukov A, Hofman S, Szymura JM, Mezhzherin SV, Morozov-Leonov SY, Barton NH, Nürnberger B. HYBRIDIZATION OF BOMBINA BOMBINA AND B. VARIEGATA (ANURA, DISCOGLOSSIDAE) AT A SHARP ECOTONE IN WESTERN UKRAINE: COMPARISONS ACROSS TRANSECTS AND OVER TIME. Evolution 2006. [DOI: 10.1554/04-739.1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
|
29
|
TAKAMI YASUOKI, SUZUKI HIROBUMI. Morphological, genetic and behavioural analyses of a hybrid zone between the ground beetles Carabus lewisianus and C. albrechti (Coleoptera, Carabidae): asymmetrical introgression caused by movement of the zone? Biol J Linn Soc Lond 2005. [DOI: 10.1111/j.1095-8312.2005.00527.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
|
30
|
Saldamando CI, Miyaguchi S, Tatsuta H, Kishino H, Bridle JR, Butlin RK. Inheritance of song and stridulatory peg number divergence between Chorthippus brunneus and C. jacobsi, two naturally hybridizing grasshopper species (Orthoptera: Acrididae). J Evol Biol 2005; 18:703-12. [PMID: 15842499 DOI: 10.1111/j.1420-9101.2004.00838.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Knowledge of the genetic basis of divergence in mating signal characters that contribute to reproductive isolation is critical to understanding speciation. Here, we describe a semi-automated system for characterizing grasshopper acoustic signals. We used this system to study the genetic basis of divergence in three male calling song components [echeme (EL), syllable (SL) and phrase (PL) lengths] between Chorthippus brunneus and C. jacobsi, two species of grasshoppers that hybridize in northern Spain. We also studied the number of pegs in the stridulatory file. For all characters, additive effects accounted for most of the genetic differentiation between species. However, the three song components also showed small but significant epistatic effects. No sex linkage was detected. Wright-Castle-Lande estimates of the minimum numbers of genetic factors underlying song and peg number divergence were low: peg number (n(e)=5.87+/-5.84), SL (n(e)=2.37+/-4.79) and PL (n(e)=0.87+/-0.86). On the other hand, EL appeared to be controlled by many genes. These results suggest that divergence in SL and PL might be driven by sexual selection whereas EL might not be under selection. This is consistent with experimental results on female song preference in related species. However, the fact that few factors appear to underlie the differences in peg number is surprising. Peg number is not closely related to song characteristics. It often varies between closely related grasshopper species and it has been assumed to be a neutral character. The biometrical approaches used here tend to underestimate the number of factors influencing a trait but provide valuable background for subsequent quantitative trait loci analyses.
Collapse
|
31
|
SALDAMANDO CI, TATSUTA H, BUTLIN RK. Hybrids between Chorthippus brunneus and C. jacobsi (Orthoptera: Acrididae) do not show endogenous postzygotic isolation. Biol J Linn Soc Lond 2005. [DOI: 10.1111/j.1095-8312.2005.000424.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
32
|
Bailey RI, Thomas CD, Butlin RK. Premating barriers to gene exchange and their implications for the structure of a mosaic hybrid zone between Chorthippus brunneus and C. jacobsi (Orthoptera: Acrididae). J Evol Biol 2003; 17:108-19. [PMID: 15000654 DOI: 10.1046/j.1420-9101.2003.00648.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Many hybrid zones contain a deficit of hybrid genotypes relative to expectations from tension zone models. This is often associated with separation of parental genotypes into distinct habitats (mosaicism), but sometimes parentals can be found co-occuring in the same local population (bimodality). In both cases, prezygotic isolation may play an important role in determining the genotypic composition of the zone. Chorthippus brunneus and C. jacobsi (Orthoptera: Acrididae) meet and form a complex hybrid zone in northern Spain. Analysis of stridulatory peg numbers reveals partial spatial and seasonal isolation in a 25 km2 area of the zone: C. jacobsi phenotypes predominate in June and July and are present in both valley and mountain habitats; C. brunneus phenotypes predominate in August and are restricted to valley habitats, always in sympatry with C. jacobsi. Strong assortative mating was observed in laboratory mating experiments. Spatial, seasonal and behavioural isolation combine to produce strong premating isolation in the study area. These results suggest a role for premating isolation in maintaining both the mosaic structure and bimodality of this hybrid zone.
Collapse
Affiliation(s)
- R I Bailey
- Centre for Biodiversity and Conservation, School of Biology, University of Leeds, Leeds, UK.
| | | | | |
Collapse
|
33
|
Babik W, Szymura JM, Rafiński J. Nuclear markers, mitochondrial DNA and male secondary sexual traits variation in a newt hybrid zone (Triturus vulgaris x T. montandoni). Mol Ecol 2003; 12:1913-30. [PMID: 12803641 DOI: 10.1046/j.1365-294x.2003.01880.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The smooth and the Montandon's newts (Triturus vulgaris and T. montandoni) are genetically similar sister species with highly divergent male secondary sexual traits involved in complex courtship behaviour. Their parapatric ranges overlap at moderate elevations in the Carpathian Mountains where they hybridize readily. Here we present a detailed study of genetic and morphological variation in populations from the area of sympatry. Analysis of variation at seven nuclear markers, mtDNA and male sexual secondary traits was complemented with an ecological survey of breeding sites characteristics. Extensive hybridization was revealed with back-cross individuals similar to either parental species predominating among hybrids. The hybrid zone exhibited a mosaic pattern: the genetic composition of the populations was correlated only weakly with their geographical position. No association with habitat type was found. Departures from Hardy-Weinberg proportions, significant linkage disequilibria and bimodal distribution of genotypes suggest strongly that assortative mating is an important factor shaping the genetic composition of hybrid populations. The pattern of cytonuclear disequilibria did not indicate much asymmetry in interspecific matings. Changes in the frequency of nuclear markers were highly concordant, whereas mtDNA showed much wider bidirectional introgression with 14% excess of T. montandoni haplotype. We argue that the mosaic structure of the newt hybrid zone results mainly from stochastic processes related to extinction and recolonization. Microgeographical differences in mtDNA introgression are explained by historical range shifts. Since morphologically intermediate males were underrepresented when compared to hybrid males identified by genetic markers, sexual selection acting against the morphological intermediates is implied. We discuss the implications of these findings in the context of reinforcement of prezygotic isolation in newts.
Collapse
Affiliation(s)
- W Babik
- Department of Comparative Anatomy, Institute of Zoology, Jagiellonian University, Ingardena 6, 30-060 Kraków, Poland.
| | | | | |
Collapse
|
34
|
|
35
|
Vines TH, Köhler SC, Thiel M, Ghira I, Sands TR, MacCallum CJ, Barton NH, Nürnberger B. THE MAINTENANCE OF REPRODUCTIVE ISOLATION IN A MOSAIC HYBRID ZONE BETWEEN THE FIRE-BELLIED TOADS BOMBINA BOMBINA AND B. VARIEGATA. Evolution 2003. [DOI: 10.1554/02-512] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
|