Evolutionary biology Allopatricspeciation from the ancient Greek allos, other Greek patrida, fatherland or geographic speciation is speciation that occurs when biological populations of the same species .... Allopatric isolation is a key factor in speciation and a common process by which new species arise ... , is a consequence of allopatricspeciation among island populations. Isolating Mechanisms Image Speciation modes.svg right thumb 360px Comparison of allopatric , peripatric speciation peripatric , parapatric speciation parapatric and sympatric speciation sympatric speciationAllopatricspeciation may occur when a species is subdivided into two genetically isolated populations. Allopatric and allopatry ... species , such a distribution is usually the result of allopatricspeciation . Separation may ... the two groups is disrupted, speciation becomes a possibility. Allopatricspeciation in peripheral populations Main Peripatric speciation When populations become genetically isolated, heritable variations ... viable, fertile offspring with members of other species. Mayr, a proponent of allopatricspeciation, hypothesized that adaptive genetic changes that accumulate between allopatric populations cause ... 2002 p 473 ref Allopatricspeciation is thought to be the dominant mode of speciation. ref Harvnb Futuyma 1980 p 254 ref Examples Image Drosophila speciation experiment.svg right thumb 425px Allopatric ... first2 Gregory C year 1980 title Non AllopatricSpeciation in Animals journal Systematic Zoology volume ... drives rapid allopatricspeciation journal Nature volume 437 pages 1353 1356 url http www.nature.com ... do not evolve as a consequence of external forces that drive populations toward speciation. Rather, the evolution of reproductive isolation, leading to speciation, is generally thought to be an incidental ... of other types of speciation, such as sympatric speciation , parapatric speciation , and heteropatric speciation , is debated. Proponents of peripatric speciation contend that small population ... more details
brief intervals, a view known as punctuated equilibrium . Allopatric Image Speciation modes.svg right thumb 300px Comparison of allopatricspeciationallopatric , peripatric speciation peripatric , parapatric speciation parapatric and sympatric speciation . Main allopatricspeciation During allopatric from the ancient Greek allos , other Greek patr , fatherland speciation, a population splits ... of allopatricspeciation, new species are formed in isolated, smaller peripheral populations that are prevented ... and allopatricspeciation. Ecologists refer to parapatric and peripatric speciation in terms ... examples of micro allopatric, or heteropatric speciation . The most widely accepted example of sympatric ... of double invasion a form of allopatricspeciation in which repeated invasions of marine forms have ...Template Evolutionary biology Speciation is the evolution ary process by which new biological species arise. The biologist Orator F. Cook seems to have been the first to coin the term speciation for the splitting ... contributor to speciation is the subject matter of much ongoing discussion. There are four geographic modes of speciation in nature, based on the extent to which speciating populations are geographically isolated from one another allopatricspeciationallopatric , peripatric speciation peripatric , parapatric speciation parapatric , and sympatric speciation sympatric . Speciation may also be induced ... kind of speciation are provided throughout. ref http www.talkorigins.org faqs faq speciation.html Observed Instances of Speciation by Joseph Boxhorn. Retrieved 8 June 2009. ref Natural speciation All forms of natural speciation have taken place over the course of evolution however it still remains a subject ... journal title Adaptive speciation The role of natural selection in mechanisms of geographic and non geographic speciation author J.M. Baker journal Studies in History and Philosophy of Biological and Biomedical ... One example of natural speciation is the diversity of the three spined stickleback , a Marine ... more details
Template Evolutionary biology Image Speciation modes.svg left thumb 300px Comparison of allopatricspeciationallopatric , peripatric, parapatric speciation parapatric and sympatric speciation sympatric speciation . Peripatric and peripatry are terms from biogeography , referring to organism s whose ranges are closely adjacent but do not overlap, being separated where these organisms do not occur &ndash for example a wide river or a mountain range. Such organisms are usually closely related e.g. sister species , their distribution being the result of peripatric speciation . Peripatric speciation is a form of speciation , the formation of new species through evolution . In this form, new species are formed in isolated peripheral populations this is similar to allopatricspeciation in that populations are isolated and prevented from exchanging genes. However, peripatric speciation, unlike allopatricspeciation, proposes that one of the populations is much smaller than the other. Peripatric speciation was originally proposed by Ernst Mayr , and is related to the founder effect , because small living populations may undergo selection bottlenecks. ref cite journal author Provine WB title Ernst Mayr Genetics and speciation url http www.genetics.org cgi content full 167 3 1041 journal Genetics volume 167 issue 3 pages 1041 6 date 1 July 2004 pmid 15280221 pmc 1470966 ref Genetic drift is often proposed to play a significant role in peripatric speciation. ref cite journal author Templeton AR title The theory of speciation via the founder principle url http www.genetics.org cgi reprint 94 4 1011 journal Genetics volume 94 issue 4 pages 1011 38 date 1 April 1980 pmid 6777243 pmc 1214177 ref speciation show no evolution show no References Reflist DEFAULTSORT Peripatric Speciation Category Ecology Category Evolutionary biology Category Speciation Category Scientific classification Category Taxonomy pt Especia o perip trica ru ... more details
Image Speciation modes.svg right thumb 300px Comparison of allopatricspeciationallopatric , peripatric speciation peripatric , parapatric speciation parapatric and sympatric speciation sympatric speciation . Heteropatric and heteropatry are terms from biogeography , referring to organism s whose geographical ranges overlap or are even identical, so that they occur together at least in some places, but which occupy ecological niche s distinct enough to prevent frequent Hybrid biology hybridization ... being the result of heteropatric speciation . Heteropatric speciation is a special case of sympatric speciation that occurs when different ecotypes or Race biology race s of the same species geographically ... speciation is a refinement of our notion of sympatric speciation in that it represents a behavioral .... The importance of behavioral separation as a mechanism for promoting sympatric speciation in a heterogeneous ... speciation . ref J. Maynard Smith, 1966. Sympatric speciation. The American Naturalist 110 637 ... Biology 36 34 58. ref of conditions that facilitate sympatric speciation . Although some evolutionary biologists still regard sympatric speciation as a highly contentious issue, both theoretical ref D. I. Bolnick, 2006. Multispecies outcomes in a common model of sympatric speciation. Journal .... Habitat avoidance overlooking an important aspect of host specific mating and sympatric speciation. Evolution 59 1552 1559. ref studies increasingly support sympatric speciation as a likely process ... resolves the issue of sympatric speciation by reducing it to a scaling issue in terms of the way ..., the process looks sympatric, but from an individual s perspective, the process looks allopatric ... into account. See also Adaptive radiation Sympatry Allopatry Cladistics Phylogenetics speciation sympatric speciationallopatricspeciation References references speciation DEFAULTSORT Heteropatric Speciation Category Biogeography Category Speciation evolution stub ... more details
Template Evolutionary biology Image Speciation modes.svg left thumb 300px Comparison of allopatricspeciationallopatric , peripatric speciation peripatric , parapatric and sympatric speciation sympatric speciation . Parapatric and parapatry are terms from biogeography , referring to organism s whose ranges do not significantly overlap but are immediately adjacent to each other they only occur together in the narrow contact zone, if at all. Such organisms are usually closely related e.g. sister species , their distribution being the result of parapatric speciation . Parapatric speciation is a form of speciation that occurs due to variations in the mating system mating habits of a population within a continuous geographical area. In this model, the parent species lives in a continuous habitat , in contrast with allopatricallopatricspeciation and peripatric speciation where subpopulations become geographically isolated. Ecological niche Niche s in this habitat can differ along an environmental gradient , hampering gene flow , and thus creating a Cline population genetics cline . In parapatric speciation there is no specific extrinsic barrier to gene flow. The population is continuous, but nonetheless, the population does not mate randomly. Individuals are more likely to mate with their geographic neighbors than with individuals in a different part of the population s range. In this mode ... ref of this is the grass Anthoxanthum , which has been known to undergo parapatric speciation in such cases ... evidence for parapatric speciation in Tennessee cave salamander s, involving divergence with gene ... online ref Another example are ring species . See also Allopatry Speciation Adaptive radiation ... evolibrary article 0 0 speciationmodes 04 Parapatric speciation. in Understanding Evolution ... evolution 101 speciation show yes evolution show no DEFAULTSORT Parapatric Speciation Category Ecology Category Evolutionary biology Category Speciation Category Scientific classification Category ... more details
for the phenomenon of speciation. In contrast to Allopatricspeciation allopatry , populations undergoing sympatric speciation are not geographically isolated by, for example, a mountain or a river. In multicellular Eukaryotes eukaryotic organisms, sympatric speciation is thought to be an uncommon ... biology Allopatricspeciation Parapatric speciation Heteropatric speciation Polymorphism biology ...Evolutionary biology Sympatric speciation is the process through which new species evolve from a single ... related e.g. sister species , such a distribution may be the result of sympatric speciation . Etymological ... of Genetics publisher Oxford University Press edition 7th year 2006 ref Evidence Image Speciation modes.svg frame left Comparison of allopatricspeciationallopatric , peripatric speciation peripatric , parapatric speciation parapatric and sympatric speciation A number of models have been proposed to account for this mode of speciation. The most popular, which invokes the disruptive selection model, was first put forward by John Maynard Smith in 1966. ref cite journal title Sympatric Speciation ... would be favoured over heterozygosity, eventually leading to speciation. Sympatric divergence could ... may drive speciation because they also affect mating signals. In this case, different beak phenotype ... ref A well studied circumstance of sympatric speciation is when insects feed on more than one species ... speciation. The apple feeding race of this species appears to have spontaneously emerged from the Crataegus ... speciation. For example, Nicaragua crater lake cichlid fishes include at least one species that has evolved by sympatric speciation ref Sympatric speciation in Nicaraguan crater lake cichlid fish ... speciation has taken place, as many examples exist of recently diverged sister taxon sister taxa allochronic species. Sympatric speciation events are vastly more common in plants, as they are prone to developing ... isolated. A rare example of sympatric speciation in animals is the divergence of resident ... more details
Speciation may refer to Speciation biology , evolutionary process by which new biological species arise Speciation chemistry , distribution of chemical elements disambig it Speciazione ... more details
Template Evolutionary biology Hybrid speciation is the process wherein Hybrid biology hybridization between two different closely related species leads to a distinct phenotype . This phenotype in very rare cases can also be fitter than the parental lineage and as such natural selection may then favor these individuals. Eventually, if reproductive isolation is achieved, it may lead to a separate species. However, reproductive isolation between hybrids and their parents is particularly difficult to achieve and thus hybrid speciation is considered an extremely rare event. Hybridization without change in chromosome number is called homoploid hybrid speciation. It is considered very rare but has been shown in Heliconius butterfly butterflies and in sunflower s. Polyploid speciation, which involves changes in chromosome number, is a more common phenomenon, especially in plant species. See also Mariana Mallard Pomarine Skua New Mexico Whiptail Genetic pollution References references Mavarez, J., Salazar, C.A., Bermingham, E., Salcedo, C., Jiggins, C.D. , Linares, M. 2006 Speciation by hybridization in Heliconius butterflies. Nature. evolution stub speciation Category Hybridisation biology Category Genetics Category Speciation Category Evolutionary biology terminology ... more details
Speciation of ions refers to the changing concentration of varying forms of an ion as the pH of the solution changes. Image Weak acid speciation3.png thumb 200px right The ratio of acid, AH and conjugate base, A sup &minus sup , concentrations varies as the difference between the pH and the p K sub a sub varies, in accordance with the Henderson Hasselbalch equation . The pH of a solution of a monoprotic weak acid can be expressed in terms of the extent of dissociation. After rearranging the expression defining the acid dissociation constant , and putting pH log sub 10 sub H sup sup , one obtains pH p K sub a sub log AH A sup sup This is a form of the Henderson Hasselbalch equation . It can be deduced from this expression that when the acid is 1 dissociated, that is, when AH A sup sup 100, pH p K sub a sub 2 when the acid is 50 dissociated, that is, when AH A sup sup 1, pH p K sub a sub when the acid is 99 dissociated, that is, when AH A sup sup 0.01, pH p K sub a sub 2 It follows that the range of pH within which there is partial dissociation of the acid is about p K sub a sub 2. This is shown graphically at the right. A practical application of these results is that the pH transition range of a pH indicator is approximately p K sub a sub 1 the colour of the indicator in its acid form is different from the colour of the conjugate base form. In the transition range both forms are in equilibrium, so the colour is intermediate. Outside the transition range the concentration of acid or conjugate base is less than 10 and the colour of the major species dominates. Image Citric acid speciation.png thumb 200 px Species concentrations calculated with the program http www.hyperquad.co.uk hyss.htm HySS for a 10mM solution of citric acid. p K sub a1 sub 3.13, p K sub a2 sub 4.76, p K sub a3 sub 6.40. A weak acid may be defined as an acid with p K sub a sub greater than about 2. An acid with p K sub a sub 2 would be 99 dissociated at pH 0, that is, in a 1 M HCl solution. Any acid ... more details
Summary Geographic illustration of SPATIAL ASPECTS OF SPECIATIONallopatricspeciation physical barrier divides population parapatric speciation founding population leaves original sympatric speciationspeciation occurs without physical separation Based on http www.bio.miami.edu dana 160 speciation.jpg from http www.bio.miami.edu dana 160 160S04 6.html Adapted from Spring 2006, Lecture Notes for EVOLUTION AND BIODIVERSITY class BIL 160 Section HJ by Dr. Dana Krempels, dana at miami dot edu. Licensing self2 GFDL with disclaimers cc by sa 2.5,2.0,1.0 migration relicense ... more details
Multiple issues unreferenced December 2007 orphan November 2006 Speciation is a process that occurs naturally in evolution and is modeled explicitly in some genetic algorithms . Speciation in nature occurs when two similar reproducing beings evolve to become too dissimilar to share genetic information effectively or correctly. In the case of living organisms , they are incapable of mating to produce offspring . Interesting special cases of different species being able to breed exist, such as a horse and a donkey mating to produce a mule . However in this case the Mule is usually infertile, and so the genetic isolation of the two parent species is maintained. In implementations of genetic search algorithms, the event of speciation is defined by some mathematical function that describes the similarity between two candidate solutions usually described as individuals in the population. If the result of the similarity is too low, the chromosomal crossover crossover Operation mathematics operator is disallowed between those individuals. See also DEFAULTSORT Speciation Genetic Algorithm Category Evolutionary algorithms Category Genetic algorithms ... more details
Unreferenced date April 2008 Expert subject Genetics date April 2008 A genetic isolate is population of organisms that has little genetic mixing with other organisms within the same species. This may result in speciation , but this is not necessarily the case. Genetic isolates may form new species in several ways allopatric speciation , in which two populations of the same species are geographically isolated from one another by an extrinsic barrier, and evolve intrinsic genetic reproductive isolation peripatric speciation , in which a small group of a population is separated from the main population, and experiences genetic drift parapatric speciation , in which zones of two diverging populations are separate, but do overlap somewhat partial separation is afforded by geography, so individuals of each species may come in contact from time to time, but selection for specific behaviours or mechanisms may prevent breeding between the two groups. sympatric speciation , a contentious method of speciation in which species diverge while inhabiting the same place. Human influences on genetic isolates include restricted Dog breeding breeding of dogs , or a community living secluded away from others such as Tristan da Cunha or Pitcairn Islands . A far larger and less secluded human genetic isolate is the ethnic Finns , natives of Finland see Finnish disease heritage . See also Language isolate Linkage disequilibrium DEFAULTSORT Genetic Isolate Category Speciation ... more details
italictitle Taxobox name Drosophila pseudoobscura regnum Animal ia phylum Arthropod a classis Insect a ordo Fly Diptera familia Drosophilidae genus Drosophila subgenus Sophophora species group Drosophila obscura species group obscura group species subgroup Drosophila pseudoobscura species subgroup pseudoobscura subgroup species D. pseudoobscura binomial Drosophila pseudoobscura binomial authority Frolova & Astaurov, 1929 ref ITIS id 146332 taxon Drosophila pseudoobscura ref Drosophila pseudoobscura is a species of Drosophilidae fruit fly , used extensively in lab studies of speciation . In 2005, D. pseudoobscura was the second Drosophila species to have its genome sequenced, after the model organism Drosophila melanogaster . ref cite journal author S. Richards, Y. Liu, et al. year 2005 title Comparative genome sequencing of Drosophila pseudoobscura Chromosomal, gene, and cis element evolution journal Genome Research journal Genome Research volume 15 pages 1 18 url http www.genome.org cgi content full 15 1 1 pmid 15632085 doi 10.1101 gr.3059305 pages 1 issue 1 pmc 540289 ref Diane Dodd was able to show allopatric speciation by reproductive isolation in D. pseudoobscura after only eight generations using different food types, starch and maltose. ref cite journal author D. M. B. Dodd year 1989 title Reproductive isolation as a consequence of adaptive divergence in Drosophila pseudoobscura journal Evolution journal Evolution volume 43 pages 1308 1311 url http www.eebweb.arizona.edu Courses Ecol525 Readings Dodd 1989.pdf ref Dodd s experiment has been easy for many others to replicate, including with other kinds of fruit flies and foods. ref cite journal author M. Kirkpatrick & V. Ravign year 2002 title Speciation by natural and sexual selection models and experiments journal The American Naturalist volume 159 pages S22 S35 doi 10.1086 338370 pmid 18707367 ref References reflist Wikispecies Drosophila pseudoobscura Category Drosophilidae Category Sequenced genomes ... more details
Vicariance is a process by which the geographical range of a taxon is split into discontinuous parts by the formation of a physical barrier, such as the uplift of a mountain, or the incursion of a body of water. An example of vicariance in marine organisms is the formation of the Isthmus of Panama , which resulted in the evolution of related species pairs on the Atlantic and Pacific sides. In biogeography , vicariance is contrasted with biological dispersal as a means of explaining the patterns of distribution among related species. For example, the occurrence of some plant genera in both Africa and Australia may be explained in one of two different ways The genus may have a Gondwana n origin that is, it may have arisen before Africa and Australia separated into distinct continents. What was once a contiguous range was broken into a widely disjunct distribution by continental drift this is an example of vicariance. The genus may be much younger, having arisen on one continent, and subsequently established populations on the other by long distance seed dispersal . Once a species has been split by vicariance into multiple populations with little to no genetic exchange , the populations begin to genetic drift drift independently. Thus vicariance is a necessary precursor to allopatric speciation . For this reason, each member of a group of closely related species that have speciated after separation into disjunct ranges by vicariance, is termed a vicariad . biology stub Category Biogeography pt Vicari ncia de Vikariismus ... more details
species surrounds the daughter species so there is no Allopatricspeciation geographic isolation . The speciation in the early stages would depend on assortative mating in which the evolving goby ... been invoked to explain sympatric speciation . For some populations there are two different resources ... assortative mating is believed to be the cause of the speciation of a daughter species from the parent ... for sympatric speciation by host shift in the sea. Current Biology 14 16 , pp. 1498 1504. ref Footnotes ... speciation Category Reproduction Category Sexual selection Category Demography Category Fertility ... more details
italic title taxobox name Layia discoidea regnum Plantae unranked divisio Angiosperms unranked classis Eudicots unranked ordo Asterids ordo Asterales familia Asteraceae genus Layia species L. discoidea binomial Layia discoidea binomial authority David D. Keck Keck Layia discoidea is a rare species of flowering plant in the Asteraceae daisy family known by the common name rayless tidytips , or rayless layia . Distribution It is Endemism endemic to California , where it is known only from the Diablo Range in southern San Benito County, California San Benito County and far western Fresno County, California Fresno County . It is a member of the serpentine soil s flora. Description This is an annual herb growing a small glandular stem to a maximum height of about 20 centimeters. The thin leaves are generally lance shaped, but the larger leaves on the lower part of the stem are usually lobed. Unlike other tidytips species, which are known for their sharply white tipped yellow ray florets, the rayless tidytips has no ray flowers or real bract phyllaries . The Head botany flower head is a cluster of many golden disc florets with a base of bractlike scales. The fruit is an achene with a short scaly brown Pappus flower structure pappus . Speciation Genetic analysis performed on this species suggest that it evolved directly from Layia glandulosa in what may be an example of both allopatric speciation and peripatric speciation . ref Baldwin, B. G. 2005 . Origin of the serpentine endemic herb Layia discoidea from the widespread L. glandulosa Compositae . Evolution journal Evolution 59 11 2473 79. ref Layia discoidea looks quite different from the white rayed Layia glandulosa , and it lives in a specialized habitat, but the two species are genetically very similar and produce robust, fertile Hybrid biology hybrids when crossed. ref Gottlieb, L. D., S. I. Warwick and V. S. Ford. 1985 . Morphological and electrophoretic divergence between Layia discoidea and L. glandulosa . Systema ... more details
Tempo and Mode in Evolution 1944 was George Gaylord Simpson George Gaylord Simpson s seminal contribution to the modern evolutionary synthesis evolutionary synthesis , which integrated the facts of paleontology with those of genetics and natural selection . Simpson argued that the microevolution of population genetics was sufficient in itself to explain the patterns of macroevolution observed by paleontology . Simpson also highlighted the distinction between tempo and mode. Tempo encompasses evolutionary rates . . . their acceleration and deceleration, the conditions of exceptionally slow or rapid evolutions, and phenomena suggestive of inertia and momentum. While mode embraces the study of the way, manner, or pattern of evolution, a study in which tempo is a basic factor, but which embraces considerably more than tempo. Simpson s Tempo and Mode attempted to draw out several distinct generalizations That evolution s tempo can impart information about its mode. That multiple tempos can be found in the fossil record bradytelic, tachytelic, horotelic . That the facts of paleontology are consistent with the Neo Darwinism genetical theory of natural selection . Moreover, that theories such as orthogenesis , Lamarckism , mutation pressures, and Hopeful Monster macromutations are either false or play little to no role. Most evolution& 151 nine tenths & 151 occurs by the steady phyletic transformation of whole lineages anagenesis . In contrast to Ernst Mayr Ernst Mayr s interpretation of speciation by splitting, particularly Allopatric speciation allopatric and Peripatric speciation peripatric speciation. The lack of evidence for evolutionary transitions in the fossil record is best accounted for, first, by the poorness of the geological record, and secondly as a consequence of quantum evolution which is responsible for the origin taxonomic units of relatively high rank, such as families, orders, and classes. . Quantum evolution built upon Sewall Wright Sewall Wright s theo ... more details
become allopatric. Over time, this led to speciation populations of the same species which ... environment, reconnecting the refugia. Scholars have since expanded the idea of this mode of speciation .... But this model of speciation remains highly controversial. Citation needed date July 2010 Simple ..., Jerry A. & Orr, H. Allen. 2004. Speciation . Sunderland Sinauer Associates, Inc. ISBN 0 87893 091 4 Haffer, Jurgen. 1969. Speciation in Amazonian Forest Birds. Science . Vol. 165 131 137. Category ... more details
This article was auto generated by User Polbot . Taxobox name Gymnophaps image Papuan Mountain Pigeon 3.jpg image caption Papuan Mountain pigeon regnum Animalia phylum Chordata classis Aves ordo Columbiformes familia Columbidae genus Gymnophaps Gymnophaps is a genus of bird in the pigeon family Columbidae it includes three species , all called Mountain pigeons. Mountain pigeons live in the forested hills and mountains of certain islands in eastern Indonesia and in the region of Melanesia . They are tree dwellers and eat fruit. A remarkable aspect of these pigeons is that they have bright red skin around the eyes. Otherwise, they are dark gray on the back and wings, with paler heads and undersides. Males and females look mostly alike, though the female Papuan Mountain pigeon has a grayer belly than the male. Mountain pigeons move around a lot and are often seen flying, usually in Flock birds flocks of at least ten or as many as a hundred or more birds. They are not known to do a lot of loud cooing, rather their vocalizations are muted or wheezy when they make any noise at all. The ranges of the three species do not overlap, so this genus is an example of probable allopatric speciation . Two species are island Endemism endemics the Long tailed Mountain pigeon is endemic to the Maluku Islands , and the Pale Mountain pigeon is endemic to the Solomon Islands archipelago Solomon Islands . The Papuan Mountain pigeon has a range in between the others it lives on the island of New Guinea and on nearby smaller islands. Species Papuan Mountain pigeon , Gymnophaps albertisii Long tailed Mountain pigeon , Gymnophaps mada Pale Mountain pigeon , Gymnophaps solomonensis Bot notice new species go here References cite book last1 Gibbs first1 David last2 Barnes first2 Eustace last3 Cox first3 John title Pigeons and Doves A Guide to the Pigeons and Doves of the World publisher Yale University Press year 2001 pages 168 169, 577 580 isbn 0 300 07886 2 Category Columbidae Columbiformes st ... more details
italictitle Taxobox name Jensenia spinosa image image width 240px image caption regnum Plant ae divisio Marchantiophyta classis Jungermanniopsida ordo Metzgeriales familia Pallaviciniaceae genus Jensenia genus authority Lindb. 1868 species J. spinosa binomial Jensenia spinosa binomial authority Lindenb. & Gott. Grolle synonyms Symphyogyna spinosa Symphyogyna serrata Pallavicinia spinosa Pallavicinia stephanii Makednothallus stephanii Jensenia stephanii Jensenia spinosa is a Monoicous dioicous bryophyte plant in the Marchantiophyta liverwort family biology family Pallaviciniaceae . It is the only African member of the Jensenia genus, and generally occurs at high elevations. ref name P Cite journal authorlink S.M. Perold title The hepatic, Jensenia spinosa Pallavicinia stephanii Pallaviciniaceae , in southern Africa journal Bothalia volume 23,2 pages 223 229 year 1993 ref It is widespread but scarce, and has been found in South Africa, Malawi, Tanzania, Rwanda Volcanoes National Park at 3,650m , the DRC, as well as the islands of Mauritius, R union and St Helena. ref name G Grolle, 1979 ref Jensenia spinosa is very similar to its neotropical relative J. erythropus , ref name G though Allopatric speciation geographically isolated . Both may be confused with Symphyogyna species, but the latter s scale shaped, rather than cup shaped involucre s have been useful in distinguishing the two genera. ref name P ref Van der Gronde, 1980 ref References Reflist Bryophyte stub Category Metzgeriales ... more details
originated as an extension of Ernst Mayr Ernst Mayr s concept of genetic revolutions by allopatricspeciationallopatric and especially peripatric speciation . Although some of the basic workings of the theory ... record and argued that Ernst Mayr s preferred mechanism of allopatricspeciation might suggest .... ref Theoretical mechanisms When Eldredge and Gould published their 1972 paper, allopatricspeciation was considered the standard theory of speciation. ref name pe1972 This theory was popularized by Ernst ... and Evolution . Cambridge, MA Harvard University Press. ref Allopatricspeciation suggests that species ... Mayr1954 As time went on Gould moved away from wedding punctuated equilibrium to allopatricspeciation, particularly as evidence accumulated in support of other modes of speciation. ref Gould, S. J. 1982 ... did not know about allopatricspeciation or had not considered its translation to geological time ... followed from long accepted conventional Darwinism, namely Ernst Mayr Mayrian allopatricspeciation ... is broken up by rare and rapid events of branching speciation called cladogenesis . Cladogenesis ... www.nileseldredge.com NELE.htm . ref Their paper built upon Ernst Mayr Ernst Mayr s theory of allopatricspeciation geographic speciation , ref name Mayr1954 Mayr, Ernst 1954 . http www.blackwellpublishing.com ... . ref name eldredge1971 Cite journal doi 10.2307 2406508 author Eldredge, Niles year 1971 title The allopatric ... Allopatric Model Phylogeny Paleozoic Invertebrates Eldredge 1971.pdf journal Evolution volume 25 issue ... s meeting, assigned Gould the topic of speciation. Gould recalls that Eldredge s 1971 publication ... edges of ecological tolerance. If most evolution happens in these rare instances of allopatricspeciation then evidence of gradual evolution should be rare. This stimulating hypothesis was alluded ..., a speciation that took 50,000 years would seem instantaneous , relative to the several million ... evolutionary change once speciation is complete, they are not claiming that there is no change ... more details
Plant Newsletter . He argued that subspecies should be reserved for those occasions where allopatricspeciationallopatric , or geographically isolated, speciation occurred and varieties are best used in cases where sympatric speciation is suspected. ref name Schlauer Schlauer, J. 1996. http carnivorousplants.org ... more details
hybridisation. Topics related to speciation Species problem Allopatric vs. sympatric speciation Sexual selection and speciation Islands as natural laboratories for exploring speciation Species concepts biological vs. phylogenetic Instant speciation via polyploidy etc. Ecological vs. genetics genetic speciation Punctuated equilibrium evolution and speciation Shifting balance theorem Haldane s rule External links ContribZool76 59 note uses Sibley Ciconiiformes An introduction to Speciation http www.uwyo.edu dbmcd molmark lect2a.html Speciation and Hybridization A Bird Hybrids Database Search ... more details
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