It is not yet clear under what conditions empirical studies can reliably detect progress toward ecological speciation through the analysis of allelic variation at neutral loci. We use a simulation approach to investigate the range of parameter space under which such detection is, and is not, likely. We specifically test for the conditions under which divergent natural selection can cause a generalized barrier to gene flow that is present across the genome. Our individual-based numerical simulations focus on how population divergence at neutral loci varies in relation to recombination rate with a selected locus, divergent selection on that locus, migration rate and population size. We specifically test whether genetic differences at neutral markers are greater between populations in different environments than between populations in similar environments. We find that this expected signature of ecological speciation can be detected under part of the parameter space, most consistently when ...
Evidence for ecological speciation has accumulated from top-down studies of adaptation and reproductive isolation [reviewed in (2, 8, 9)]. We now know of many real species that have, at least in part, evolved by divergent natural selection between environments. The connections between selection on ordinary phenotypic traits and reproductive isolation are often strong and straightforward. It follows that much of the genetic basis of reproductive isolation should involve ordinary genes that underlie differences in phenotypic traits. But we still know little about the genetics of ecological speciation.. One line of evidence comes from tests of parallel speciation, whereby greater reproductive isolation repeatedly evolves between independent populations adapting to contrasting environments than between independent populations adapting to similar environments (20, 23). A major challenge in applying the test to natural populations is to eliminate the possibility that each ecotype has originated just ...
We are meeting this semester in the Biopharm 3rd Floor Fishbowl Mondays and Tuesdays 2-3pm. Please sign up for two dates on the schedule below. A list of topic ideas follows but you can choose anything related to speciation and hybridization. Subtopic Ideas: SPECIATION 1) What did Darwin say about speciation and hybridization? (First week) 2) When does a species become a species? How can the earliest stages of speciation be recognized? 3) How much genetic divergence should we expect within species? Are large genetic divergences within species due to polymorphisms/large population sizes, or artifacts, or are they simply due to our failure to recognize cryptic species? 4) Are there "speciation genes"? What are some examples? Are speciation genes restricted to a certain type of mutation or class of genes? HYBRIDIZATION: It has been estimated that at least 25% of plant species and 10% animal species hybridize* 1) How much gene flow occurs across species boundaries and what are the consequences for ...
We are meeting this semester in the Biopharm 3rd Floor Fishbowl Mondays and Tuesdays 2-3pm. Please sign up for two dates on the schedule below. A list of topic ideas follows but you can choose anything related to speciation and hybridization. Subtopic Ideas: SPECIATION 1) What did Darwin say about speciation and hybridization? (First week) 2) When does a species become a species? How can the earliest stages of speciation be recognized? 3) How much genetic divergence should we expect within species? Are large genetic divergences within species due to polymorphisms/large population sizes, or artifacts, or are they simply due to our failure to recognize cryptic species? 4) Are there "speciation genes"? What are some examples? Are speciation genes restricted to a certain type of mutation or class of genes? HYBRIDIZATION: It has been estimated that at least 25% of plant species and 10% animal species hybridize* 1) How much gene flow occurs across species boundaries and what are the consequences for ...
Explain the difference between the morphological species concept and the biological species concept.. With the morphological species concept, individuals are grouped into species by appearance and professional judgment. Those individuals that appear similar to one another are considered one species. This concept was the origin of taxonomy. Criticisms of this method are that it is arbitrary and that it may not be able to discriminate, for example, when one species mimics another. The biological species concept defines a species as a group of actually or potentially interbreeding individuals who are reproductively isolated from other groups. Individuals must be able to produce successful fertile offspring. Shortcomings of this concept are that it cannot be used with fossils or spatially disconnected populations.. Potential Question ...
A recent study of a pair of sympatric species of palms on the Lord Howe Island is viewed as providing probably one of the most convincing examples of sympatric speciation to date. Here we describe and study a stochastic, individual-based, explicit genetic model tailored for this palms system. Overall, our results show that relatively rapid (, 50 000 generations) colonization of a new ecological niche, and sympatric or parapatric speciation via local adaptation and divergence in flowering periods are theoretically plausible if (i) the number of loci controlling the ecological and flowering period traits is small; (ii) the strength of selection for local adaptation is intermediate; and (iii) an acceleration of flowering by a direct environmental effect associated with the new ecological niche is present. We discuss patterns and time-scales of ecological speciation identified by our model, and we highlight important parameters and features that need to be studied empirically in order to provide ...
Darwin proposed that natural selection had a fundamental role in speciation, but did not elaborate much on the mechanism. It is now believed that much speciation is due not to natural selection, but to geographical isolation and genetic drift (allopatric speciation). However, natural selection is still seen to play a role in other speciation, such as speciation due to specialization on different hosts (Filchak et al. 2000), and natural selection drives incipient species to greater diversity (Presgraves et al. 2003 ...
Leiopotherapon unicolor is the most widespread freshwater fish species in Australia. A comprehensive allozyme and mitochondrial DNA 16S rRNA data set was assembled from 141 specimens of L. unicolor collected Australia-wide in order to test for cryptic speciation in this far-ranging species. Surprisingly, little genetic diversity was observed within L. unicolor and provided no evidence for the existence of cryptic species within this lineage. In contrast, a small sample set of L. aheneus used as the outgroup showed two highly divergent haplotypes strongly suggestive of cryptic speciation. L. unicolor has a number of ecological and life history attributes that may explain the lack of significant genetic divergence over substantial geographical distances. The occurrence of other widespread fish and crustacean species that also display only limited genetic diversity indicate that climate conditions more favourable to dispersal across central and northern Australia than is suggested by the extent of ...
The name Phoberus capensis (Scholtz) is applied to a small flightless, keratinophagous beetle endemic to the Cape Floristic Region of South Africa. Its gross distribution stretches from roughly 1000 km from the Cederberg (S32°2422" E19°0450") to Grahamstown (S33°2007" E26°3250"). The populations are spatially discrete, restricted to relict forests of the southern Cape and disjunct high montane refugia of the Cape Fold Mountains. We test the hypothesis that there is more than one distinct species nested within the name P. capensis. Phylogenetic relationships among populations were inferred using molecular sequence data. The results support three distinct evolutionary lineages, which were also supported by morphological characters. Divergence time estimates suggest Pliocene-Pleistocene diversification. Based on these results, it is suggested that the P. capensis lineage experienced climatically-driven allopatric speciation with sheltered Afrotemperate forests and high mountain peaks ...
Insects represent the worlds largest group of organisms, comprising over 900 000 described species, which is about 70% of all animal species [1]. Their species richness and biological diversity make insects key players in almost every terrestrial ecosystem. Many explanations for this hyperdiversity focus on the ecological niche and on ecological speciation [2]. Central to the concept of ecological speciation is that populations of the same species become genetically isolated because they specialize in different ecological niches [3-5]. This is assumed to result in the evolution of new species owing to restricted gene flow between populations, in allopatry as well as in sympatry [6]. One problem with the concept of ecological speciation is that it must be initiated by the switch of particular individuals of a population to a new ecological niche (e.g. a new host in herbivorous or parasitoid insects) to which they are not yet adapted. It is unclear why the offspring of these pioneers should ...
Rapporteur: Chris B. Cameron. Tricia Abe began her lecture by asking How do genetic drift and selection interact to produce new species?" That is, is speciation a by-product of adaptation or do adaptive differences accumulate after genetic reorganization has occurred in a founder event? Viewing speciation in a historical context we see that Darwin (1859) was the first to recognize lineage splitting in The Evolution of Species, but he didnt address the underlying mechanism of speciation. Fisher (1918) documented the accumulation of new and favorable mutations in a population, and that adaptation produces genetic differences as a side effect. In 1931 Wright noticed that the non adaptive drift in small stable populations is sufficient to favor gene combinations that are unlikely to occur in larger populations, and that eventually this drift would become hard wired by natural selection. In 1940 Mayr formulated the biological species concept and by 1954 recognized that random genetic drift and ...
Author Summary Speciation, the process by which one species splits into two, involves reproductive barriers between previously interbreeding populations. The question of how speciation occurs has rightly occupied the attention of biologists since before Darwins
Many biodiversity hotspots are located in montane regions, especially in the tropics. A possible explanation for this pattern is that the narrow thermal tolerances of tropical species and greater climatic stratification of tropical mountains create more opportunities for climate-associated parapatric or allopatric speciation in the tropics relative to the temperate zone. However, it is unclear whether a general relationship exists among latitude, climatic zonation and the ecology of speciation. Recent taxon-specific studies obtained different results regarding the role of climate in speciation in tropical versus temperate areas. Here, we quantify overlap in the climatic distributions of 93 pairs of sister species of mammals, birds, amphibians and reptiles restricted to either the New World tropics or to the Northern temperate zone. We show that elevational ranges of tropical- and temperate-zone species do not differ from one another, yet the temperature range experienced by species in the ...
From Campbell, (p. 446): 4 different ways of putting it... "...a species [is] a population or group of populations whose members have the potential to interbreed with one another in nature to produce viable, fertile offspring, but who cannot produce viable, fertile offspring with members of another species.". "...a species is the largest unit of population in which genetic exchange is possible, and that is genetically isolated from other such populations." "Members of a biological species are united by being reproductively compatible, at least potentially." "...the biological species concept hinges on reproductive isolation, with each species isolated by factors (barriers) that prevent interbreeding, thereby blocking genetic mixing with other species.". From Freeman & Herron (1998) Evolutionary Analysis, Prentice Hall, Upper Saddle River. p. 314. 1. Species consist of groups of interbreeding populations. 2. Species are fundamental unit of evolution. 3. Species share a distinguishing ...
Sexual reproduction with meiosis exists in all fungal phyla, except the Deuteromycota. It differs in many aspects from sexual reproduction in animals or plants. Many differences also exist between fungal groups and have been used to discriminate fungal clades and species based on morphological differences in sexual structures and reproductive strategies. Experimental crosses between fungal isolates can also be used to identify species based on biological species concepts. The major fungal clades have initially been delineated based on the morphology of their sexual structures and spores; for example, the spore-containing structures, asci and basidia, can be used in the identification of ascomycetes and basidiomycetes, respectively. Many fungal species have elaborate vegetative incompatibility systems that allow mating only between individuals of opposite mating type, while others can mate and sexually reproduce with any other individual or itself. Species of the former mating system are called ...
Sherry, Jessica Lynne, "Ecological Divergence Among Extremely Close Relatives in Bacillus" (2013). Honors Theses - All. 1103 ...
The simulations use an agent-based population model that consists of haploid and hermaphroditic individuals characterized by a binary string of B loci. Reproduction is restricted by a mating area determined by a spatial distance, S, and a genetic distance, G, beyond which other individuals are not considered potential mates. Reproductive isolation caused by this mechanism can be considered a multilocus generalization of the Bateson-Dobzhansky-Muller model whereby individuals accumulate genetic incompatibilities without the population passing through an adaptive valley (22). Reproductive success depends on the number of genetic differences between the individuals attempting mating, without affecting the fitness of the individuals themselves (21). The genetic distance between two individuals is the number of differing loci along their strings. The geographical space is represented by a 128 × 142 lattice with barriers defined by sites that cannot be occupied by individuals (Fig. S1). The remaining ...
In my book Speciation, written with Allen Orr, we give some estimates about how long it takes to make a new species. These estimates vary, of course. In the case of speciation that involves instantaneous genome doubling, as in auto- or allopolyploidy, a new hybrid species can arise in as few as three generations. But…
Slide set: Biological Evolution - Modes of Speciation. Learn about speciation (the formation of new species) and how populations evolve genetic distinctiveness and become reproductively separate.
Slide set: Biological Evolution - Modes of Speciation. Learn about speciation (the formation of new species) and how populations evolve genetic distinctiveness and become reproductively separate.
There is a large body of work evidencing the necessity to evaluate chemical speciation dynamics of trace metals in solution for an accurate definition of their bioavailability to microorganisms. In contrast, the integration of intracellular metal speciation dynamics in biouptake formalisms is still in its ea
Lu Han, Hiroyuki Koike, Praneet Chaturvedi, Keishi Kishimoto, Kentaro Iwasawa, Kirsten Giesbrecht, Phillip C Witcher, Alexandra Eicher, Talia Nasr, Lauren Haines, John M Shannon, Mitsuru Morimoto, James M Wells, Takanori Takebe, Aaron M Zorn
RPM points out that the most recent issue of Heredity tackles the issue of the genetics of speciation. Heres an interesting thing Ive noted, there are two ways to look at species questions. First, there are the taxonomists, who have been strongly influenced by the cladist revolution. They take a big picture philosophical view, and are obviously greatly concerned with process in terms of classification and demarcation. In contrast, there are the evolutionary geneticists who tend to be less interested in species qua species, as opposed to the process of genetic differentiation. In other words, for the latter camp species discussions are simply an ends toward elucidating the evolutionary dynamics of populations. The taxonomists in contrast are focused on species as the ends for generating their systems of evolutionary relationships. The Neandertal introgression story should make it clear Im interested in the dynamics of evolutionary processes, not any rigorous species classification ...
Testing the chromosomal speciation hypothesis for humans and chimpanzees.: Fixed differences of chromosomal rearrangements between isolated populations may prom
Find speciation sampling articles on Environmental XPRT, the worlds largest environmental industry marketplace and information resource.
Get the latest speciation sampling news on Environmental XPRT, the worlds largest environmental industry marketplace and information resource.
New regulatory mandates require elemental analysis of many toxic metals and nutritional elements. Learn how combining the power of IC and ICP-MS to deliver speciation analysis has made it feasible to uncover complete chemical species information.
My apologies if someone here has mentioned this article already: http://www.vanderbilt.edu/exploration/stories/speciation.html Basically, this was...
Many species today exist right on this cusp of a speciation event, and are called ring species. To put it very briefly, population A can interbreed with population B, which can interbreed with population C, but A and C cant interbreed. If B didnt exist, A and C would thus be classified as different species. What they actually represent is a species that is beginning to diverge into two new species, but the intermediate form (in this case, population B) hasnt died out yet. This is a very brief desciption but you can read here for more details ...
This covers rapid speciation, punctuated equilibrium and evolution by means other than natural selection. It covers how scientists use molecular techniques.
Gilead Sciences has been dealing with a slowdown for its hep C superstars Sovaldi and combo drug Harvoni, with prescriptions for the drugs petering off during the second quarter and analysts expecting things to continue in the same vein. As predicted the companys lagging momentum continued into Q3, with sales growth for its hep C treatments staying flat despite beats on earnings.
When God created the kinds, He frontloaded them with genetic differences-with the potential to form all sorts of new species and varieties.
DI-fusion, le Dépôt institutionnel numérique de lULB, est loutil de référencementde la production scientifique de lULB.Linterface de recherche DI-fusion permet de consulter les publications des chercheurs de lULB et les thèses qui y ont été défendues.
Greetings, Thanks for taking the time to look at my post. Ive run into an issue with my computer to which I cant remedy. A few things have begun...
Martínez-Garrido J, Serrão EA, Engelen AH, Cox CJ, García-Murillo P, Gonzalez-Wangüemert M. Multilocus genetic analyses provide insight into speciation and hybridization in aquatic grasses, genus Ruppia. Biological Journal of the Linnean Society. 2016;117(2):177 - 191. doi:10.1111/bij.12666 ...
Since Darwin, researchers have made tremendous progress towards understanding how ecological, genetic and evolutionary factors acting within species lead to the evolution of reproductive isolation and ultimately the origin of new species (Coyne & Orr 2004). One problem that remains largely unresolved concerns the evolution of intrinsic postzygotic isolation. Investigating early stages in the evolution of postzygotic isolation in species, where alleles underlying postzygotic isolation are still polymorphic, is one promising approach.. Previous studies of postzygotic isolation between M. guttatus and M. nasutus have found reduced seed germination and male infertility in hybrids (Vickery 1956, 1973, 1978; Fishman & Willis 2001, 2006; Martin & Willis 2007). Vickery (1956, 1973, 1978) and Sweigart et al. (2007) provided evidence that postzygotic isolation within and among populations of both species varied geographically, though biometrical line crosses were not used to determine the genetic basis. ...
The biologist Ernst Mayr championed the concept of ring species, claiming that it unequivocally demonstrated the process of speciation.[10] A ring species is an alternative model to allopatric speciation, "illustrating how new species can arise through circular overlap, without interruption of gene flow through intervening populations…"[11] However, Jerry Coyne and H. Allen Orr point out that rings species more closely model parapatric speciation.[8]. Ring species often attract the interests of evolutionary biologists, systematists, and researchers of speciation leading to both thought provoking ideas and confusion concerning their definition.[12] Contemporary scholars recognize that examples in nature have proved rare due to various factors such as limitations in taxonomic delineation[13] or, "taxonomic zeal"[10]-explained by the fact that taxonomists classify organisms into "species", while ring species often cannot fit this definition.[12] Other reasons such as gene flow interruption from ...
TY - JOUR. T1 - Gene flow between sexual and asexual strains of parasitic wasps. T2 - A possible case of sympatric speciation caused by a parthenogenesis-inducing bacterium. AU - Adachi-Hagimori, Tetsuya. AU - Miura, Kazuki. AU - Abe, Yoshihisa. PY - 2011/6. Y1 - 2011/6. N2 - Sympatric speciation is strictly defined as the emergence of two species from a population in which mating has been random with respect to the place of birth of the mating partners. Mathematical models have shown that sympatric speciation is possible, but very few examples have been documented in nature. In this article, we demonstrate that arrhenotokous and thelytokous strains of a parasitic wasp, Neochrysocharis formosa, speciated sympatrically through infection by a symbiotic bacterium Rickettsia for the following reasons: First, Rickettsia infection was detected in all of the thelytokous strains collected throughout Japan. Second, the arrhenotokous and thelytokous strains have been collected sympatrically. Third, ...
Hybrid speciation is an example of sympatric speciation that can occur in plants.. Interspecies hybrids are usually sterile because the chromosome pairs, which consist of one chromosome from one species and another from the second species, do not segregate regularly at meiosis. When a hybrid species evolves, sterility may be overcome by polyploidy: the chromosome numbers are doubled. Each chromosome pair at meiosis contains two chromosomes from one species, and regular segregation is restored. Polyploidization is encouraged by applying the chemical colchicine in the commercial production of new species, but it can also occur naturally at a low rate. In this case, a new hybrid species may evolve. The polyploidy hybrids are interfertile among themselves, but reproductively isolated (by the mismatch in chromosome numbers) from the parental species; they are therefore well defined new species.. Many popular species of flower such as tulips (opposite) and orchids are created through artificial ...
Once the basis is ready, we can run the model. Below I am going to focus on some of the results and at the end I am going to attach the complete output file as TXT. you can download an play with the txt if you like:. Part 1 Result: This part gives you the some of the important parameters. First of all, the model has predicted a pH of 8.34 for the sea water. In reality the pH varies between 7.8 to 8.5 depending on the place of sea water collection. Secondly, the CBE is 0.04%. This again tells you that the chemical analysis of the sea water was great. It gives you the carbonate alkalinity 122.22 mg/kg soln as CaCO3 and also tells you that you have a Na-Cl water.. ...
Aquilegia formosa and Aquilegia pubescens are two closely-related species belonging to the columbine genus. Despite their morphological and ecological differences, previous studies have revealed a large degree of intercompatibility as well as little sequence divergence between these two taxa, and the genetic mechanisms underpinning reproductive isolation remain unknown. In order to assess the feasibility of a full genome scan for speciation genes, inter- and intraspecific patterns of variation were compared for 9 nuclear loci; it was concluded that the two species were practically indistinguishable at the level of DNA sequence polymorphism, indicating either very recent speciation or continued gene flow. As a comparison, the variation at two loci was analyzed across 30 other Aquilegia species, revealing slightly more differentiation among taxa and evidence for isolation by geographic distance (which was not the case on a more local geographic scale).; The extremely low levels of genetic ...
Population boundaries are largely determined by local environment, the strength of barriers to migration, and the organisms inherent dispersal abilities. The interaction among these and genetic factors determines the potential for evolutionary divergence, and is at the heart of our understanding of ecological adaptation and ongoing speciation processes. When individuals can easily cross barriers between suitable habitat patches, gene flow acts to homogenize most neutral genetic diversity and may swamp the effects of any local phenotypic selection whereas low levels of migration may facilitate ecological divergence, even when selection is modest. Evolutionary divergence through fine-scale geographic isolation is believed to be one of the main mechanisms promoting speciation in the cichlid radiations of the African Great Lakes [1-3]. Many lake species are extreme local endemics, with distributions limited to small patches of ecologically distinct habitat. Many narrowly endemic cichlid species are ...
I will argue that Drosophila geneticists are not so much interested in finding "speciation genes", but rather interested in understanding the genetics of speciation. To do so requires finding mutations that allow the species boundary to be surmounted. As I have mentioned previously, good species are reproductively isolated, preventing any genetical analysis of the factors that lead to this isolation. Mutations in the "speciation genes" (especially the extremely useful Hybrid Male Rescue mutation), however, allow researchers to cross individuals from different species and study the genetics of speciation.. Geneticists like to find generalities. That is why we study model organisms; they are easy to work with in a laboratory setting and allow us to extend our discoveries regarding molecular biology, cellular function, development, physiology, etc to other related taxa (both closely related and more distant relatives). Wilkins makes a valid point that it is difficult to generalize discoveries ...
Cant speak for others but here at Uncommon Descent, we have been thinking that for quite some time. Were not shocked but we are annoyed when discredited textbook Darwinism is treated as the norm and the true state of affairs is treated as a big surprise.. See also: Bale monkeys more closely related to sister species than same species in different locationsThe "biological species concept" is yet another textbook dead zone.. Girl got mostly a double set of her dads genes, is almost a twin. She has some problems but she is 11 years old. Yes, that was the sound of another lectern splintering in the near distance.. Almost one in five genes coding status is unresolved Researchers: We believe that the three reference databases currently overestimate the number of human coding genes by at least 2000, complicating and adding noise to large-scale biomedical experiments.. Do all genes affect every complex trait? Veronique Greenwood: The roots of many traits, from how tall you are to your susceptibility ...
Darren has published a review of sex chromosomes evolution and speciation in birds and other ZW systems. This is an invited submission for a special issue of Molecular Ecology, on "Sex Chromosomes and Speciation.". Heres the citation and link:. Irwin, D.E. 2018. Sex chromosomes and speciation in birds and other ZW systems. Molecular Ecology, online Early View: https://doi.org/10.1111/mec.14537. ...
Sympatric and parapatric speciation refer to theorigin of biological species in the absence of complete geographic isolation between the diverging taxa
Levels of genetic differentiation between populations can be highly variable across the genome, with divergent selection contributing to such heterogeneous genomic divergence. For example, loci under divergent selection and those tightly physically linked to them may exhibit stronger differentiation than neutral regions with weak or no linkage to such loci. Divergent selection can also increase genome-wide neutral differentiation by reducing gene flow (e.g. by causing ecological speciation), thus promoting divergence via the stochastic effects of genetic drift. These consequences of divergent selection are being reported in recently accumulating studies that identify: (i) outlier loci with higher levels of divergence than expected under neutrality, and (ii) a positive association between the degree of adaptive phenotypic divergence and levels of molecular genetic differentiation across population pairs [isolation by adaptation (IBA)]. The latter pattern arises because as adaptive divergence ...
In Speciation in Birds, Trevor Price, a University of Chicago professor and leading expert in the field, has written the most authoritative and modern synthesis on the subject to date. In clear and engaging prose and through beautiful illustrations, Price shows us why the field is as exciting and vibrant as ever. He evaluates the roles of natural selection and sexual selection. He asks how speciation contributes to some of the great patterns in species diversity such as the large number of species in the tropics, and the many endemic species on isolated islands. Throughout the book, Price emphasizes the integration of behavior, ecology, and genetics.
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Recent developments are providing exciting new insights into the evolutionary dynamics of species diversification and the importance of evolutionary radiations, or rapid episodes of lineage diversification. The aim of this meeting is to explore questions about where, when and why plant evolutionary radiations happen, and how they proceed. The meeting will bring together contributions spanning: (i) new models of species diversification, including paleodiversity and trait evolution, and the increasingly sophisticated and powerful tools available for testing hypotheses about diversification trajectories and their causes; (ii) the proliferation of new molecular phylogenetic data, for more and larger plant clades spanning broader taxonomic, geographical and temporal levels, as well as opportunities for unprecedented phylogenetic resolution of rapidly evolving clades coming from genome-scale DNA sequence data; (iii) assembly of more comprehensive species geographic distribution, functional and life ...