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Eviatar Nevo - One of the best experts on this subject based on the ideXlab platform.
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incipient Sympatric Speciation in wild barley caused by geological edaphic divergence
Life Science Alliance, 2020Co-Authors: Xifeng Ren, Dongfa Sun, Xiaoying Song, Yu Zhou, Eli Harlev, Eviatar NevoAbstract:Sympatric Speciation (SS) has been contentious since the idea was suggested by Darwin. Here, we show in wild barley SS due to geologic and edaphic divergence in "Evolution Plateau," Upper Galilee, Israel. Our whole genome resequencing data showed SS separating between the progenitor old Senonian chalk and abutting derivative young Pleistocene basalt wild barley populations. The basalt wild barley species unfolds larger effective population size, lower recombination rates, and larger genetic diversity. Both species populations show similar descending trend ∼200,000 yr ago associated with the last glacial maximum. Coalescent demography analysis indicates that SS was local, primary, in situ, and not due to a secondary contact from ex situ allopatric population. Adaptive divergent putatively selected genes were identified in both populations. Remarkably, disease resistant genes were selected in the wet basalt population, and genes related to flowering time, leading to temporal reproductive isolation, were selected in the chalk population. The evidence substantiates adaptive ecological SS in wild barley, highlighting the genome landscape during SS with gene flow, due to geologic-edaphic divergence.
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transcriptomes divergence of ricotia lunaria between the two micro climatic divergent slopes at evolution canyon i israel
Frontiers in Genetics, 2018Co-Authors: Chaoju Qian, Xia Yan, Hengxia Yin, Xingke Fan, Xiaoyue Yin, Peipei Sun, Eviatar NevoAbstract:As one of the hotspot regions for Sympatric Speciation studies, Evolution Canyon (EC) became an ideal place for its high level of microclimatic divergence interslopes. In this study, to highlight the genetic mechanisms of Sympatric Speciation, phenotypic variation on flowering time and transcriptomic divergence were investigated between two ecotypes of Ricotia lunaria, which inhabit the opposite temperate and tropical slopes of EC I (Lower Nahal Oren, Mount Carmel, Israel) separated by 100 m at the bottom of the slopes. Growth chamber results showed that flowering time of the ecotype from south-facing slope population # 3 (SFS 3) was significantly 3 months ahead of the north-facing slope population # 5 (NFS 5). At the same floral development stage, transcriptome analysis showed that 1,064 unigenes were differentially expressed between the two ecotypes, which enriched in the four main pathways involved in abiotic and/or biotic stresses responses, including flavonoid biosynthesis, α-linolenic acid metabolism, plant-pathogen interaction and linoleic acid metabolism. Furthermore, based on Ka/Ks analysis, nine genes were suggested to be involved in the ecological divergence between the two ecotypes, whose homologs functioned in RNA editing, ABA signaling, photoprotective response, chloroplasts protein-conducting channel, and carbohydrate metabolism in Arabidopsis thaliana. Among them, four genes, namely, SPDS1, FCLY, Tic21 and BGLU25, also showed adaptive divergence between R. lunaria and A. thaliana, suggesting that these genes could play an important role in plant Speciation, at least in Brassicaceae. Based on results of both the phenotype of flowering time and comparative transcriptome, we hypothesize that, after long-time local adaptations to their interslope microclimatic environments, the molecular functions of these nine genes could have been diverged between the two ecotypes. They might differentially regulate the expression of the downstream genes and pathways that are involved in the interslope abiotic stresses, which could further diverge the flowering time between the two ecotypes, and finally induce the reproductive isolation establishment by natural selection overruling interslope gene flow, promoting Sympatric Speciation.
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adaptive methylation regulation of p53 pathway in Sympatric Speciation of blind mole rats spalax
Proceedings of the National Academy of Sciences of the United States of America, 2016Co-Authors: Yang Zhao, Kexin Li, Jiawei Tang, Zhi Yang, Yuval Benabu, Xuequn Chen, Jizeng Du, Eviatar NevoAbstract:Epigenetic modifications play significant roles in adaptive evolution. The tumor suppressor p53, well known for controlling cell fate and maintaining genomic stability, is much less known as a master gene in environmental adaptation involving methylation modifications. The blind subterranean mole rat Spalax eherenbergi superspecies in Israel consists of four species that speciated peripatrically. Remarkably, the northern Galilee species Spalax galili (2n = 52) underwent adaptive ecological Sympatric Speciation, caused by the sharply divergent chalk and basalt ecologies. This was demonstrated by mitochondrial and nuclear genomic evidence. Here we show that the expression patterns of the p53 regulatory pathway diversified between the abutting Sympatric populations of S. galili in sharply divergent chalk–basalt ecologies. We identified higher methylation on several sites of the p53 promoter in the population living in chalk soil (chalk population). Site mutagenesis showed that methylation on these sites linked to the transcriptional repression of p53 involving Cut-Like Homeobox 1 (Cux1), paired box 4 (Pax 4), Pax 6, and activator protein 1 (AP-1). Diverse expression levels of p53 between the incipiently Sympatrically speciating chalk–basalt abutting populations of S. galili selectively affected cell-cycle arrest but not apoptosis. We hypothesize that methylation modification of p53 has adaptively shifted in supervising its target genes during Sympatric Speciation of S. galili to cope with the contrasting environmental stresses of the abutting divergent chalk–basalt ecologies.
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Sympatric Speciation revealed by genome wide divergence in the blind mole rat spalax
Proceedings of the National Academy of Sciences of the United States of America, 2015Co-Authors: Wei Hong, Eviatar Nevo, Yang Zhao, Hengwu Jiao, Guodong Wang, Karl A Rodriguez, Rochelle Buffenstein, Huabin ZhaoAbstract:Sympatric Speciation (SS), i.e., Speciation within a freely breeding population or in contiguous populations, was first proposed by Darwin [Darwin C (1859) On the Origins of Species by Means of Natural Selection] and is still controversial despite theoretical support [Gavrilets S (2004) Fitness Landscapes and the Origin of Species (MPB-41)] and mounting empirical evidence. Speciation of subterranean mammals generally, including the genus Spalax, was considered hitherto allopatric, whereby new species arise primarily through geographic isolation. Here we show in Spalax a case of genome-wide divergence analysis in mammals, demonstrating that SS in continuous populations, with gene flow, encompasses multiple widespread genomic adaptive complexes, associated with the sharply divergent ecologies. The two abutting soil populations of S. galili in northern Israel habituate the ancestral Senonian chalk population and abutting derivative Plio-Pleistocene basalt population. Population divergence originated ∼0.2-0.4 Mya based on both nuclear and mitochondrial genome analyses. Population structure analysis displayed two distinctly divergent clusters of chalk and basalt populations. Natural selection has acted on 300+ genes across the genome, diverging Spalax chalk and basalt soil populations. Gene ontology enrichment analysis highlights strong but differential soil population adaptive complexes: in basalt, sensory perception, musculature, metabolism, and energetics, and in chalk, nutrition and neurogenetics are outstanding. Population differentiation of chemoreceptor genes suggests intersoil population's mate and habitat choice substantiating SS. Importantly, distinctions in protein degradation may also contribute to SS. Natural selection and natural genetic engineering [Shapiro JA (2011) Evolution: A View From the 21st Century] overrule gene flow, evolving divergent ecological adaptive complexes. Sharp ecological divergences abound in nature; therefore, SS appears to be an important mode of Speciation as first envisaged by Darwin [Darwin C (1859) On the Origins of Species by Means of Natural Selection].
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Sympatric incipient Speciation of spiny mice acomys at evolution canyon israel
Proceedings of the National Academy of Sciences of the United States of America, 2014Co-Authors: Yarin Hadid, Tomas Pavlicek, Avigdor Beiles, Ron Ianovici, Shmuel Raz, Eviatar NevoAbstract:Does the paucity of empirical evidence of Sympatric Speciation in nature reflect reality, despite theoretical support? Or is it due to inappropriate searches in nature with overly restrictive assumptions and an incorrect null hypothesis? Spiny mice, Acomys, described here at Evolution Canyon (EC) incipiently and Sympatrically speciate owing to microclimatic interslope divergence. The opposite slopes at EC vary dramatically, physically and biotically, representing the dry and hot south-facing slope savannoid-African continent [“African” slope (AS)], abutting with the north-facing slope forested south-European continent [“European” slope (ES)]. African-originated spiny mice, of the Acomys cahirinus complex, colonized Israel 30,000 y ago based on fossils. Genotypically, we showed significantly higher genetic diversity of mtDNA and amplified fragment length polymorphism of Acomys on the AS compared with the ES. This is also true regionally across Israel. In complete mtDNA, 25% of the haplotypes at EC were slope-biased. Phenotypically, the opposite slope’s populations also showed adaptive morphology, physiology, and behavior divergence paralleling regional populations across Israel. Preliminary tests indicate slope-specific mate choices. Colonization of Acomys at the EC first occurred on the AS and then moved to the ES. Strong slope-specific natural selection (both positive and negative) overrules low interslope gene flow. Both habitat slope selection and mate choices suggest ongoing incipient Sympatric Speciation. We conclude that Acomys at the EC is ecologically and genetically adaptively, incipiently, Sympatrically speciating on the ES owing to adaptive microclimatic natural selection.
Stewart H. Berlocher - One of the best experts on this subject based on the ideXlab platform.
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Postzygotic isolating factor in Sympatric Speciation in Rhagoletis flies: Reduced response of hybrids to parental host-fruit odors
Proceedings of the National Academy of Sciences of the United States of America, 2004Co-Authors: Charles E Linn, Stewart H. Berlocher, Satoshi Nojima, Hattie R. Dambroski, Wendell L. RoelofsAbstract:Rhagoletis pomonella is a model for Sympatric Speciation (divergence without geographic isolation) by means of host-plant shifts. Many Rhagoletis species are known to use fruit odor as a key olfactory cue to distinguish among their respective host plants. Because Rhagoletis rendezvous on or near the unabscised fruit of their hosts to mate, behavioral preferences for fruit odor translate directly into premating reproductive isolation among flies. Here, we report that reciprocal F(1) hybrids between the apple and hawthorn host races of R. pomonella, as well as between the host races and an undescribed sibling species infesting Cornus florida (flowering dogwood) do not respond to host fruit volatiles in wind-tunnel assays at doses that elicit maximal directed flight in parental flies. The reduced ability of hybrids to orient to fruit volatiles could result from a conflict between neural pathways for preference and avoidance behaviors, and it suggests that hybrids might suffer a fitness disadvantage for finding fruit in nature. Therefore, host-specific mating may play a dual role as an important postzygotic as well as a premating reproductive barrier to isolate Sympatric Rhagoletis flies.
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fruit odor discrimination and Sympatric host race formation in rhagoletis
Proceedings of the National Academy of Sciences of the United States of America, 2003Co-Authors: Charles E Linn, Stewart H. Berlocher, Satoshi Nojima, Hattie R. Dambroski, Wendell L. RoelofsAbstract:Rhagoletis pomonella is a model for incipient Sympatric Speciation (divergence without geographic isolation) by host-plant shifts. Here, we show that historically derived apple- and ancestral hawthorn-infesting host races of the fly use fruit odor as a key olfactory cue to help distinguish between their respective plants. In flight-tunnel assays and field tests, apple and hawthorn flies preferentially oriented to, and were captured with, chemical blends of their natal fruit volatiles. Because R. pomonella rendezvous on or near the unabscised fruit of their hosts to mate, the behavioral preference for apple vs. hawthorn fruit odor translates directly into premating reproductive isolation between the fly races. We have therefore identified a key and recently evolved (<150 years) mechanism responsible for host choice in R. pomonella bearing directly on Sympatric host race formation and Speciation.
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Sympatric Speciation in phytophagous insects moving beyond controversy
Annual Review of Entomology, 2002Co-Authors: Stewart H. Berlocher, Jeffrey L FederAbstract:▪ Abstract Sympatric Speciation is the splitting of one evolutionary lineage into two without the occurrence of geographic isolation. The concept has been intimately tied to entomology since the 1860s, when Benjamin Walsh proposed that many host-specific phytophagous insects originate by shifting and adapting to new host plant species. If true, Sympatric Speciation would have tremendous implications for our understanding of species and their origins, biodiversity (25–40% of all animals are thought to be phytophagous specialists), insect-plant coevolution, community ecology, phylogenetics, and systematics, as well as practical significance for the management of insect pests. During much of the twentieth century Sympatric Speciation was viewed as much less plausible than geographic (allopatric) Speciation. However, empirical field studies, laboratory experiments, developments in population genetics theory, and phylogenetic and biogeographic data have all recently combined to shed a more favorable light on t...
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radiation and divergence in the rhagoletis pomonella species group inferences from allozymes
Evolution, 2000Co-Authors: Stewart H. BerlocherAbstract:The Rhagoletis pomonella species group has for decades been a focal point for debate over the possibility of Sympatric Speciation via host shift. Here I present the first extensive analysis of genetic (allozyme) divergence in the pomonella group, including all known taxa/populations except the allopatric Mexican population of R. pomonella. The phylogeny is estimated for all four described species (pomonella, mendax, zephyria, and cornivora) plus two undescribed species (the "flowering dogwood fly" and "sparkleberry fly"). Allozyme data for two additional populations of uncertain status (the "plum fly" and "mayhaw fly") are presented for the first time. Two data sets were analyzed, one for 17 loci from 77 populations and one for an additional 12 loci for a subset of 12 of these populations, with more than 4000 flies analyzed in total. Interspecific Nei unbiased genetic distances were generally small, being as low as 0.040. No fixed autapomorphic alleles beyond those already known for R. cornivora and R. zephyria were revealed in the new data, but several loci displaying frequency patterns useful in discriminating the species were discovered. The phylogenetic placement of the flowering dogwood fly differed depending on whether a molecular clock was assumed (UPGMA of Nei distance) or not assumed (frequency parsimony) for tree building. Other than this, however, trees under either assumption were essentially identical. The best tree was used to test the prediction of the Sympatric Speciation hypothesis that sister taxa should be broadly Sympatric. This prediction was not rejected, but the best tree was weakly supported by bootstrap analysis. An unexpected finding was that R. pomonella populations representing ends of its strong latitudinal clines did not cluster together. One possible explanation is that the current R. pomonella is the result of a genetic fusion of two previously isolated, genetically differentiated populations. Such a fusion prior to the origin of the other species in the group could contribute to the poor resolution of the phylogeny.
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the population genetics of the apple maggot fly rhagoletis pomonella and the snowberry maggot r zephyria implications for models of Sympatric Speciation
Entomologia Experimentalis Et Applicata, 1999Co-Authors: Jeffrey L Feder, Stewart H. Berlocher, Bruce A Mcpheron, Scott M Williams, Guy L BushAbstract:True fruit flies belonging to the Rhagoletis pomonella (Diptera:Tephritidae) sibling species complex possess several attributes consistent with a history of Sympatric divergence via host plant shifts. Here, we investigate whether hybridization and genetic introgression is occurring between two members of the group, Rhagoletis pomonella (Walsh), whose primary hosts are domestic apples (Malus pumila) and hawthorns (Crataegus spp., and R. zephyria (Snow) whose host is snowberries (Symphoricarpos spp.). These flies are important because they appear to be at a transition stage between taxa reproductively isolated solely on the basis of host plant-related adaptations and those that have evolved additional non-host dependent sterility and inviability. Observing extensive hybridization and introgression between R. pomonella and R. zephyria would have major repercussions for current models of Sympatric Speciation. In a survey of allozyme and mitochondrial DNA (mtDNA) variation for 1105 flies collected throughout the northern United States we found two results suggesting that low level hybridization occurs between R. pomonella and R. zephyria. (1) Two flies reared from snowberries and one fly reared from hawthoms had genotypes indicative of them being R. pomonella and R. zephyria, respectively. Rhagoletis pomonella and R. zephyria adults may therefore occasionally frequent each others host plant, providing the opportunity for hybridization. (2) Four flies collected from hawthorns and one from snowberries had genotypes that made them likely to be F1 hybrids. Likelihood analysis revealed the data were also consistent with an hypothesis of shared ancestral alleles (i.e., the pattern of genetic variation could also be explained by R. pomonella and R. zephyria sharing alleles/haplotypes whose origins date to a common ancestor). We estimated that, in the absence of interspecific mating, random assortment of genes within R. pomonella and R. zephyria populations would produce an average of 5.4 flies with genotypes suggesting they were F1 hybrids – a number equivalent to the 5 putative F1 hybrids observed in the study. Our results therefore underscore the difficulty in distinguishing between hypotheses of low level introgression and shared ancestral polymorphism. But even if hybridization is occurring, the data suggest that it is happening at a very low and probably evolutionarily insignificant level (perhaps 0.09% per generation), consistent with Sympatric Speciation theory. Future tests are discussed that could help resolve the hybridization issue for R. pomonella and R. zephyria.
Denis Bourguet - One of the best experts on this subject based on the ideXlab platform.
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assortative mating in Sympatric host races of the european corn borer
Science, 2005Co-Authors: Thibaut Malausa, Marietherese Bethenod, Denis Bourguet, Arnaud Bontemps, Jeanmarie Cornuet, Sergine PonsardAbstract:Although a growing body of work supports the plausibility of Sympatric Speciation in animals, the practical difficulties of directly quantifying reproductive isolation between diverging taxa remain an obstacle to analyzing this process. We used a combination of genetic and biogeochemical markers to produce a direct field estimate of assortative mating in phytophagous insect populations. We show that individuals of the same insect species, the European corn borer Ostrinia nubilalis , that develop on different host plants can display almost absolute reproductive isolation—the proportion of assortative mating was >95%—even in the absence of temporal or spatial isolation.
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genetic isolation between two Sympatric host plant races of the european corn borer ostrinia nubilalis hubner i sex pheromone moth emergence timing and parasitism
Evolution, 2003Co-Authors: Yan Thomas, Marietherese Bethenod, Laurent Pelozuelo, Brigitte Frerot, Denis BourguetAbstract:Abstract Adaptation to different environments may be a powerful source of genetic differentiation between populations. The biological traits selected in each environment can pleiotropically induce assortative mating between individuals of these genetically differentiated populations. This situation may facilitate Sympatric Speciation. Successful host shifts in phytophagous insects provide some of the best evidence for the ecological Speciation that occurs, or has occurred, in sympatry. The European corn borer, Ostrinia nubilalis (Lepidoptera: Crambidae), colonized maize after its introduction into Europe by humans about 500 years ago. In northern France, two Sympatric host races feed on maize (Zea mays) and mugwort (Artemisia vulgaris), respectively. We investigated the factors involved in the genetic isolation of these two races at a field site near Paris, France. We identified two biological differences that might make a significant contribution to the genetic divergence between Sympatric populations fe...
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genetic isolation between two Sympatric host plant races of the european corn borer ostrinia nubilalis hubner i sex pheromone moth emergence timing and parasitism
Evolution, 2003Co-Authors: Yan Thomas, Marietherese Bethenod, Laurent Pelozuelo, Brigitte Frerot, Denis BourguetAbstract:Abstract Adaptation to different environments may be a powerful source of genetic differentiation between populations. The biological traits selected in each environment can pleiotropically induce assortative mating between individuals of these genetically differentiated populations. This situation may facilitate Sympatric Speciation. Successful host shifts in phytophagous insects provide some of the best evidence for the ecological Speciation that occurs, or has occurred, in sympatry. The European corn borer, Ostrinia nubilalis (Lepidoptera: Crambidae), colonized maize after its introduction into Europe by humans about 500 years ago. In northern France, two Sympatric host races feed on maize (Zea mays) and mugwort (Artemisia vulgaris), respectively. We investigated the factors involved in the genetic isolation of these two races at a field site near Paris, France. We identified two biological differences that might make a significant contribution to the genetic divergence between Sympatric populations fe...
Axel Meyer - One of the best experts on this subject based on the ideXlab platform.
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incipient Speciation driven by hypertrophied lips in midas cichlid fishes
Molecular Ecology, 2017Co-Authors: Gonzalo Machadoschiaffino, Andreas F Kautt, Julian Torresdowdall, Lukas Baumgarten, Frederico Henning, Axel MeyerAbstract:Sympatric Speciation has been debated in evolutionary biology for decades. Although it has gained in acceptance recently, still only a handful of empirical examples are seen as valid (e.g. crater lake cichlids). In this study, we disentangle the role of hypertrophied lips in the repeated adaptive radiations of Nicaraguan crater lake cichlid fish. We assessed the role of disruptive selection and assortative mating during the early stages of divergence and found a functional trade-off in feeding behaviour between thick- and thin-lipped ecotypes, suggesting that this trait is a target of disruptive selection. Thick-lipped fish perform better on nonevasive prey at the cost of a poorer performance on evasive prey. Using enclosures in the wild, we found that thick-lipped fish perform significantly better in rocky than in sandy habitats. We found almost no mixed pairs during two breeding seasons and hence significant assortative mating. Genetic differentiation between ecotypes seems to be related to the time since colonization, being subtle in L. Masaya (1600 generations ago) and absent in the younger L. Apoyeque (<600 generations ago). Genome-wide differentiation between ecotypes was higher in the old source lakes than in the young crater lakes. Our results suggest that hypertrophied lips might be promoting incipient Sympatric Speciation through divergent selection (ecological divergence in feeding performance) and nonrandom mating (assortative mating) in the young Nicaraguan crater lakes. Nonetheless, further manipulative experiments are needed in order to confirm the role of hypertrophied lips as the main cue for assortative mating.
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incipient Sympatric Speciation in midas cichlid fish from the youngest and one of the smallest crater lakes in nicaragua due to differential use of the benthic and limnetic habitats
Ecology and Evolution, 2016Co-Authors: Andreas F Kautt, Gonzalo Machadoschiaffino, Julian Torresdowdall, Axel MeyerAbstract:Understanding how Speciation can occur without geographic isolation remains a central objective in evolutionary biology. Generally, some form of disruptive selection and assortative mating are necessary for Sympatric Speciation to occur. Disruptive selection can arise from intraspecific competition for resources. If this competition leads to the differential use of habitats and variation in relevant traits is genetically determined, then assortative mating can be an automatic consequence (i.e., habitat isolation). In this study, we caught Midas cichlid fish from the limnetic (middle of the lake) and benthic (shore) habitats of Crater Lake Asososca Managua to test whether some of the necessary conditions for Sympatric Speciation due to intraspecific competition and habitat isolation are given. Lake As. Managua is very small (<900 m in diameter), extremely young (maximally 1245 years of age), and completely isolated. It is inhabited by, probably, only a single endemic species of Midas cichlids, Amphilophus tolteca. We found that fish from the limnetic habitat were more elongated than fish collected from the benthic habitat, as would be predicted from ecomorphological considerations. Stable isotope analyses confirmed that the former also exhibit a more limnetic lifestyle than the latter. Furthermore, split-brood design experiments in the laboratory suggest that phenotypic plasticity is unlikely to explain much of the observed differences in body elongation that we observed in the field. Yet, neutral markers (microsatellites) did not reveal any genetic clustering in the population. Interestingly, demographic inferences based on RAD-seq data suggest that the apparent lack of genetic differentiation at neutral markers could simply be due to a lack of time, as intraspecific competition may only have begun a few hundred generations ago.
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embryonic and larval development in the midas cichlid fish species flock amphilophus spp a new evo devo model for the investigation of adaptive novelties and species differences
BMC Developmental Biology, 2015Co-Authors: Claudius F Kratochwil, Maggie M Sefton, Axel MeyerAbstract:Background Central American crater lake cichlid fish of the Midas species complex (Amphilophus spp.) are a model system for Sympatric Speciation and fast ecological diversification and specialization. Midas cichlids have been intensively analyzed from an ecological and morphological perspective. Genomic resources such as transcriptomic and genomic data sets, and a high-quality draft genome are available now. Many ecologically relevant species-specific traits and differences such as pigmentation and cranial morphology arise during development. Detailed descriptions of the early development of the Midas cichlid in particular, will help to investigate the ontogeny of species differences and adaptations.
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Sympatric Speciation in nicaraguan crater lake cichlid fish
Nature, 2006Co-Authors: Marta Barluenga, Kai N Stolting, Walter Salzburger, Moritz Muschick, Axel MeyerAbstract:One of the hottest controversies in evolutionary biology is Sympatric Speciation, the formation of new species in the absence of geographical boundaries. The controversy is about whether it happens or not: it ‘should’ in theory but it is difficult to prove it. Two new examples of the phenomenon are reported this week, one in fish and one (online) in plants, convincing evidence that as Darwin suggested, Sympatric Speciation is likely to be common. The fishy example is the formation of Amphilophus zaliosus from A. citrinellus in a volcanic crater lake in Nicaragua. And in plants, the curly palm Howea belmoreana and the thatch palm H. forsteriana diverged on Lord Howe Island, a volcanic island 480 km east of Australia in the Tasman Sea. Sympatric Speciation, the formation of species in the absence of geographical barriers, remains one of the most contentious concepts in evolutionary biology. Although Speciation under Sympatric conditions seems theoretically possible1,2,3,4,5, empirical studies are scarce and only a few credible examples of Sympatric Speciation exist6. Here we present a convincing case of Sympatric Speciation in the Midas cichlid species complex (Amphilophus sp.) in a young and small volcanic crater lake in Nicaragua. Our study includes phylogeographic, population-genetic (based on mitochondrial DNA, microsatellites and amplified fragment length polymorphisms), morphometric and ecological analyses. We find, first, that crater Lake Apoyo was seeded only once by the ancestral high-bodied benthic species Amphilophus citrinellus, the most common cichlid species in the area; second, that a new elongated limnetic species (Amphilophus zaliosus) evolved in Lake Apoyo from the ancestral species (A. citrinellus) within less than ∼10,000 yr; third, that the two species in Lake Apoyo are reproductively isolated; and fourth, that the two species are eco-morphologically distinct.
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The Midas cichlid species complex: incipient Sympatric Speciation in Nicaraguan cichlid fishes?
Molecular ecology, 2004Co-Authors: Marta Barluenga, Axel MeyerAbstract:Sympatric Speciation is a contentious concept, although theoretical models as well as empirical evidence support its relevance in evolutionary biology. The Midas cichlid species complex ( Amphilophus citrinellus , labiatus , zaliosus ) from several crater lakes in Nicaragua fits several of the key characteristics of a Sympatric Speciation model. In particular, in A. citrinellus (i) strong assortative mating on the basis of colour polymorphism and (ii) ecological differentiation based on morphological polymorphisms involving the feeding apparatus and body shape might both be mechanisms of incipient Speciation. Seven microsatellite markers and mtDNA control region sequences [836 base pairs (bp)] were used to study the population genetic structure of 519 specimens of Midas cichlid populations from the two Great Lakes Managua and Nicaragua, and three crater lakes in Nicaragua, Central America. The three named species of the species complex occupy different ecological niches, are morphologically distinct and can be distinguished genetically. We uncovered allopatric genetic differentiation of populations of A. citrinellus from different lakes and distant locations within Lake Managua and, more interestingly, incipient genetic differentiation of several Sympatric populations based on colouration (in A. citrinellus and A. labiatus ) but not on the morphology of the pharyngeal jaws (in A. citrinellus ). Sexual selection and assortative mating might be the driven forces of diversification within named species. The Midas cichlid species complex in Nicaragua is an excellent model system for the study of the incipient stages of adaptation, Speciation and the formation of species flocks.
Jeffrey L Feder - One of the best experts on this subject based on the ideXlab platform.
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The diapause response of Rhagoletis pomonella to varying environmental conditions and its significance for geographic and host plant-related adaptation
Entomologia Experimentalis et Applicata, 2010Co-Authors: Jeffrey L Feder, Thomas H Q Powell, Ken Filchak, Brian LeungAbstract:The recent shift of Rhagoletis pomonella Walsh (Diptera: Tephritidae) from its ancestral host hawthorn to apple is a model for incipient Sympatric Speciation in action. Previous studies have shown that changes in the over-wintering pupal diapause are critical for differentially adapting R. pomonella flies to a difference in the fruiting times of apples vs. hawthorns, generating ecologically based reproductive isolation. Here, we exposed pupae of the hawthorn race to various combinations of pre- and over-wintering rearingconditions andanalyzed theireffectsoneclosiontime and genetics. Wereport certainunexpectedresults inregards toa combinationofbrief pre-winterandover-winteringperiods indicative of gene*environment interactions requiring a reassessment of our current understanding ofR.pomonelladiapause.Wepresent ahypothesis thatinvolvesphysiological factorsrelatedtostored energy reserves in pupae that influences the depth and duration of Rhagoletis diapause. This ‘pupal energyreserve’hypothesis canaccount for ourfindings andhelpclarify therolehost plant-relatedlife historyadaptationplaysinphytophagebiodiversity.
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divergent preferences of rhagoletis pomonella host races for olfactory and visual fruit cues
Entomologia Experimentalis Et Applicata, 2006Co-Authors: Andrew A Forbes, Jeffrey L FederAbstract:The apple and hawthorn-infesting host races of Rhagoletis pomonella Walsh (Diptera: Tephritidae) represent a model for incipient Sympatric Speciation. Recent studies have shown that apple and hawthorn flies differ in their responses to host-fruit odor. Each host race preferentially orients to the volatile chemicals emanating from the surface of its natal fruit and is antagonized by non-natal fruit volatiles. Fruit odor discrimination is evolutionarily important due to its contributory role in host-specific mating, generating partial premating reproductive isolation between the races in sympatry. Visual cues are also involved in R. pomonella host searching, yet the extent to which they are used to discriminate between hosts has not been fully resolved, nor has their interaction with olfactory cues. Here, we report results from a series of two-way choice experiments conducted in the field on resident apple and hawthorn flies at a site near Fennville, MI, USA. Four key findings emerged from the study: (1) both olfactory and (2) visual cues increased host discrimination of apple and hawthorn flies for their respective natal fruit, (3) the presence of a single appropriate volatile blend on a natal or non-natal visual model generally increased the ability of flies to discriminate for their natal fruit, and (4) the presence of both natal and non-natal olfactory cues on fruit models did not enhance host discrimination above levels observed for visual models alone. We discuss the implications of our results for interpreting the findings of two-way host choice experiments and for Sympatric Speciation in phytophagous insects.
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evidence for inversion polymorphism related to Sympatric host race formation in the apple maggot fly rhagoletis pomonella
Genetics, 2003Co-Authors: Jeffrey L Feder, Joseph B Roethele, Kenneth E Filchak, Julie Niedbalski, Jeanne RomeroseversonAbstract:Evidence suggests that the apple maggot, Rhagoletis pomonella (Diptera: Tephritidae) is undergoing Sympatric Speciation (i.e., divergence without geographic isolation) in the process of shifting and adapting to a new host plant. Prior to the introduction of cultivated apples (Malus pumila) in North America, R. pomonella infested the fruit of native hawthorns (Crataegus spp.). However, sometime in the mid-1800s the fly formed a Sympatric race on apple. The recently derived apple-infesting race shows consistent allele frequency differences from the hawthorn host race for six allozyme loci mapping to three different chromosomes. Alleles at all six of these allozymes correlate with the timing of adult eclosion, an event dependent on the duration of the overwintering pupal diapause. This timing difference differentially adapts the univoltine fly races to an approximately 3- to 4-week difference in the peak fruiting times of apple and hawthorn trees, partially reproductively isolating the host races. Here, we report finding substantial gametic disequilibrium among allozyme and complementary DNA (cDNA) markers encompassing the three chromosomal regions differentiating apple and hawthorn flies. The regions of disequilibrium extend well beyond the previously characterized six allozyme loci, covering substantial portions of chromosomes 1, 2, and 3 (haploid n = 6 in R. pomonella). Moreover, significant recombination heterogeneity and variation in gene order were observed among single-pair crosses for each of the three genomic regions, implying the existence of inversion polymorphism. We therefore have evidence that genes affecting diapause traits involved in host race formation reside within large complexes of rearranged genes. We explore whether these genomic regions (inversions) constitute coadapted gene complexes and discuss the implications of our findings for Sympatric Speciation in Rhagoletis.
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Sympatric Speciation in phytophagous insects moving beyond controversy
Annual Review of Entomology, 2002Co-Authors: Stewart H. Berlocher, Jeffrey L FederAbstract:▪ Abstract Sympatric Speciation is the splitting of one evolutionary lineage into two without the occurrence of geographic isolation. The concept has been intimately tied to entomology since the 1860s, when Benjamin Walsh proposed that many host-specific phytophagous insects originate by shifting and adapting to new host plant species. If true, Sympatric Speciation would have tremendous implications for our understanding of species and their origins, biodiversity (25–40% of all animals are thought to be phytophagous specialists), insect-plant coevolution, community ecology, phylogenetics, and systematics, as well as practical significance for the management of insect pests. During much of the twentieth century Sympatric Speciation was viewed as much less plausible than geographic (allopatric) Speciation. However, empirical field studies, laboratory experiments, developments in population genetics theory, and phylogenetic and biogeographic data have all recently combined to shed a more favorable light on t...
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the population genetics of the apple maggot fly rhagoletis pomonella and the snowberry maggot r zephyria implications for models of Sympatric Speciation
Entomologia Experimentalis Et Applicata, 1999Co-Authors: Jeffrey L Feder, Stewart H. Berlocher, Bruce A Mcpheron, Scott M Williams, Guy L BushAbstract:True fruit flies belonging to the Rhagoletis pomonella (Diptera:Tephritidae) sibling species complex possess several attributes consistent with a history of Sympatric divergence via host plant shifts. Here, we investigate whether hybridization and genetic introgression is occurring between two members of the group, Rhagoletis pomonella (Walsh), whose primary hosts are domestic apples (Malus pumila) and hawthorns (Crataegus spp., and R. zephyria (Snow) whose host is snowberries (Symphoricarpos spp.). These flies are important because they appear to be at a transition stage between taxa reproductively isolated solely on the basis of host plant-related adaptations and those that have evolved additional non-host dependent sterility and inviability. Observing extensive hybridization and introgression between R. pomonella and R. zephyria would have major repercussions for current models of Sympatric Speciation. In a survey of allozyme and mitochondrial DNA (mtDNA) variation for 1105 flies collected throughout the northern United States we found two results suggesting that low level hybridization occurs between R. pomonella and R. zephyria. (1) Two flies reared from snowberries and one fly reared from hawthoms had genotypes indicative of them being R. pomonella and R. zephyria, respectively. Rhagoletis pomonella and R. zephyria adults may therefore occasionally frequent each others host plant, providing the opportunity for hybridization. (2) Four flies collected from hawthorns and one from snowberries had genotypes that made them likely to be F1 hybrids. Likelihood analysis revealed the data were also consistent with an hypothesis of shared ancestral alleles (i.e., the pattern of genetic variation could also be explained by R. pomonella and R. zephyria sharing alleles/haplotypes whose origins date to a common ancestor). We estimated that, in the absence of interspecific mating, random assortment of genes within R. pomonella and R. zephyria populations would produce an average of 5.4 flies with genotypes suggesting they were F1 hybrids – a number equivalent to the 5 putative F1 hybrids observed in the study. Our results therefore underscore the difficulty in distinguishing between hypotheses of low level introgression and shared ancestral polymorphism. But even if hybridization is occurring, the data suggest that it is happening at a very low and probably evolutionarily insignificant level (perhaps 0.09% per generation), consistent with Sympatric Speciation theory. Future tests are discussed that could help resolve the hybridization issue for R. pomonella and R. zephyria.
