Phylogeography is the study of the historical processes that may be responsible for the contemporary geographic distributions of individuals. This is accomplished by considering the geographic distribution of individuals in light of the patterns associated with a gene genealogy. History See also History of genetics The existence of genes was first suggested by Gregor Mendel (1822-1884 who in the 1860s studied inheritance Genealogy (from Greek: el γενεά el-Latn genea, "descent" and el λόγος el-Latn logos, "knowledge" is the study of ^[1] This term was introduced to describe geographically structured genetic signals within and among species. In Biology, a species is one of the basic units of Biological classification and a Taxonomic rank. An explicit focus on a species' biogeography/biogeographical past sets phylogeography apart from classical population genetics and phylogenetics. Biogeography is the study of the distribution of Biodiversity over Space and Time. Population genetics is the study of the Allele frequency distribution and change under the influence of the four evolutionary forces Natural selection, Genetic ^[2] Past events that can be inferred include population expansion, population bottlenecks, vicariance and migration. A population bottleneck (or genetic bottleneck) is an Evolutionary event in which a significant percentage of a population or species is killed or otherwise prevented Allopatric speciation, also known as geographic Speciation, is the phenomenon whereby biological populations are physically isolated by an extrinsic barrier Recently developed approaches integrating coalescent theory or the genealogical history of alleles and distributional information can more accurately address the relative roles of these different historical forces in shaping current patterns. In Genetics, coalescent theory is a retrospective model of population genetics that traces all Alleles of a Gene in a sample from a population to a single ^[3]

Contents 1 Development 2 Phylogeography and conservation 3 Comparative phylogeography 4 Human phylogeography 5 Phylogeography of viruses 6 References

Development

While the term phylogeography was first coined in 1987,^[4] it has existed as a field of study for much longer. Historical biogeography addresses how historical geological, climatic and ecological conditions influenced the current distribution of species. As part of historical biogeography, researchers had been evaluating the geographical and evolutionary relationships of organisms years before. Two developments during the 1960s and 1970s were particularly important in laying the groundwork for modern phylogeography; the first was the spread of cladistic thought, and the second was the development of plate tectonics theory. Cladistics is the hierarchical classification of Species based on evolutionary ancestry Plate tectonics (from Greek τέκτων tektōn "builder" or "mason" describes the large scale motions of Earth 's Lithosphere ^[5] The resulting school of thought was vicariance biogeography, which explained the origin of new lineages through geological events like the drifting apart of continents or the formation of rivers. When a continuous population (or species) is divided by a new river or a new mountain range (i. e. , a vicariance event), two populations (or species) are created. Paleogeography, geology and paleoecology are all important fields that supply information that is integrated into phylogeographic analyses. Palaeogeography (sometimes spelled paleogeography) is the study of what the Geography was in times past Geology (from Greek γη gê, "earth" and λόγος Logos, "speech" lit Paleoecology uses data from Fossils and subfossils to reconstruct the Ecosystems of the past

Phylogeography takes a population genetics and phylogenetic perspective on biogeography. Population genetics is the study of the Allele frequency distribution and change under the influence of the four evolutionary forces Natural selection, Genetic Biogeography is the study of the distribution of Biodiversity over Space and Time. In the mid-1970s, population genetic analyses turned to mitochondrial markers. ^[6] The advent of the polymerase chain reaction (PCR), the process where millions of copies of a DNA segment can be replicated, was crucial in the development of phylogeography. Thanks to this breakthrough, the information contained in mitochondrial DNA sequences was much more accessible. Advances in both laboratory methods (e.g. capillary DNA sequencing technology) that allowed easier sequencing DNA and computational methods that make better use of the data (e. C D E Capillaries are the smallest of a body's Blood vessels measuring 5-10 μm in diameter which connect Arterioles and Venules and enable the interchange The term DNA sequencing encompasses biochemical methods for determining the order of the Nucleotide bases Adenine, Guanine, Cytosine g. employing coalescent theory) have helped improve phylogeographic inference. In Genetics, coalescent theory is a retrospective model of population genetics that traces all Alleles of a Gene in a sample from a population to a single ^[6].

Early phylogeographic work has recently been criticized for its narrative nature and lack of statistical rigor (i.e. it did not statistically test alternative hypotheses). Statistics is a mathematical science pertaining to the collection analysis interpretation or explanation and presentation of Data. F G H I L The only real method was Alan Templeton's Nested Clade Analysis, which made use of an inference key to determine the validity of a given process in explaining the concordance between geographic distance and genetic relatedness. Alan Templeton is a United States Geneticist and statistician from Washington University in St Recent approaches have taken a stronger statistical approach to phylogeography than was done initially. ^{[7] [8] [2]}

Example

Climate change, such as the glaciation cycles of the past 2. 4 million years, has periodically restricted some species into disjunct refugia. These restricted ranges may result in population bottlenecks that reduce genetic variation. A population bottleneck (or genetic bottleneck) is an Evolutionary event in which a significant percentage of a population or species is killed or otherwise prevented Once a reversal in climate change allows for rapid migration out of refugial areas, these species spread rapidly into newly available habitat. A number of empirical studies find genetic signatures of both animal and plant species that support this scenario of refugia and postglacial expansion. ^[3] This has occurred both in the tropics^[9][10] as well as temperate regions that were influenced by glaciers. ^[11]

Phylogeography and conservation

Phylogeography can help in the prioritization of areas of high value for conservation. Phylogeographic analyses have also played an important role in defining evolutionary significant units (ESU), a unit of conservation below the species level that is often defined on unique geographic distribution and mitochondrial genetic patterns. An Evolutionarily Significant Unit (ESU (often lowercased where used without abbreviation as evolutionarily significant unit) is a population of Organisms that is ^[12]

A recent study on imperiled cave crayfish in the Appalachian Mountains of eastern North America^[13] demonstrates how phylogenetic analyses along with geographic distribution can aid in recognizing conservation priorities. Crayfish, crawfish, crawdads, or crodgers are freshwater Crustaceans resembling small Lobsters to which they are closely The Appalachian Mountains ( often called the Appalachians, are a vast system of mountains in eastern North America. Using phylogeographical approaches, the authors found that hidden within what was thought to be a single, widely distributed species an ancient and previously undetected species was also present. Conservation decisions can now be made to ensure that both lineages received protection. Results like this are not an uncommon outcome from phylogeographic studies.

An analysis of salamanders of the genus Eurycea, also in the Appalachians, found that the current taxonomy of the group greatly underestimated species level diversity. Salamander (orig from Persian: sām, "fire" and andarūn, "within" is the common name for a group of approximately 500 Species Eurycea is a Genus of Salamanders commonly referred to as Brook Salamanders, native to North America. ^[14] The authors of this study also found that patterns of phylogeographic diversity were more associated with historical (rather than modern) drainage connections, indicating that major shifts in the drainage patterns of the region played an important role in the generation of diversity of these salamanders. A thorough understanding of phylogeographic structure will thus allow informed choices in prioritizing areas for conservation.

Comparative phylogeography

The field of comparative phylogeography seeks to explain the mechanisms responsible for the phylogenetic relationships and distribution of different species. For example, comparisons across multiple taxa can clarify the histories of biogeographical regions. ^[15] For example, phylogeographic analyses of terrestrial vertebrates on the Baja California peninsula^[16] and marine fish on both the Pacific and gulf sides of the peninsula^[15] display genetic signatures that suggest a vicariance event affected multiple taxa during the Pleistocene or Pliocene. Baja California (pronounced ˈbɑːhɑː kælɨˈfɔrnjə in English is the northernmost state of Mexico. The Pleistocene ('plaɪstəsin is the epoch from 18 million to 10000 years BP covering the world's recent period The Pliocene epoch (spelled Pleiocene in some older texts is the period in the Geologic timescale that extends

Phylogeography also gives an important historical perspective on community composition. History is relevant to regional and local diversity in two ways. ^[9] One, the size and makeup of the regional species pool results from the balance of speciation and extinction. Speciation is the Evolutionary process by which new biological Species arise In Biology and Ecology, extinction is the cessation of existence of a Species or group of taxa. Two, at a local level community composition is influenced by the interaction between local extinction of species’ populations and recolonization. ^[9] A comparative phylogenetic approach in the Australian Wet Tropics indicates that regional patterns of species distribution and diversity are largely determined by local extinctions and subsequent recolonizations corresponding to climatic cycles.

Human phylogeography

Main articles: Recent single-origin hypothesis and Multiregional hypothesis

Phylogeography has also proven to be useful in understanding the origin and dispersal patterns of our own species, Homo sapiens. In Paleoanthropology, the recent African origin of modern humans is one of two hypotheses of the origin of anatomically modern humans Homo sapiens sapiens In paleoanthropology, the multiregional hypothesis is one of two accounts of the origin of anatomically modern humans Homo sapiens. Human beings, humans or man (Origin 1590–1600 L homō man OL hemō the earthly one (see Humus Based primarily on observations of skeletal remains of ancient human remains and estimations of their age, anthropologists proposed two competing hypotheses about human origins. The first hypothesis is referred to as the Out-of-Africa with replacement model, which contends that the last expansion out of Africa around 100,000 years ago resulted in the modern humans displacing all previous Homo spp. In Paleoanthropology, the recent African origin of modern humans is one of two hypotheses of the origin of anatomically modern humans Homo sapiens sapiens populations in Eurasia that were the result of an earlier wave of emigration out of Africa. For the superstate in George Orwell 's novel see Nations of Nineteen Eighty-Four. The multiregional scenario claims that individuals from the recent expansion out of Africa intermingled genetically with those human populations of more ancient African emigrations. In paleoanthropology, the multiregional hypothesis is one of two accounts of the origin of anatomically modern humans Homo sapiens. A phylogeographic study that uncovered a Mitochondrial Eve that lived in Africa 150,000 years ago provided early support for the Out-of-Africa model. Mitochondrial Eve ( mt-mrca) is the name given by researchers to the woman who is defined as the Matrilineal most recent common ancestor (MRCA for all currently ^[17] While this study had its shortcomings, it received significant attention both within scientific circles and a wider audience. A more thorough phylogeographic analysis that used ten different genes instead of a single mitochondrial marker indicates that at least two major expansions out of Africa after the initial range extension of Homo erectus played an important role shaping the modern human gene pool and that recurrent genetic exchange is pervasive. Homo erectus ( Latin: "upright man" is an extinct species of the genus Homo, believed to have been the first hominin ^[18] These findings strongly demonstrated Africa's central role in the evolution of modern humans, but also indicated that the multiregional model had some validity. eVolution is the third Album by eLDee, it was due to be released in 2008

Phylogeography of viruses

Viruses are informative in understanding the dynamics of evolutionary change due to their rapid mutation rate and fast generation time. ^[19] Phylogeography is a useful tool in understanding the origins and distributions of different viral strains. A phylogeographic approach has been taken for many diseases that threaten human health, including dengue fever, rabies, influenza and HIV. Rabies (from rabies “madness rage fury” Also known as “ hydrophobia ” is a viral Zoonotic neuroinvasive disease that Human immunodeficiency virus ( HIV) is a Lentivirus (a member of the Retrovirus family that can lead to acquired immunodeficiency syndrome ^[19] Similarly, a phylogeographic approach will likely play a key role in understanding the vectors and spread of avian influenza (HPAI H5N1), demonstrating the relevance of phylogeography to the general public. For the H5N1 subtype of Avian influenza see H5N1. Avian influenza, sometimes Avian flu, and commonly Bird flu refers Influenza A virus subtype H5[[Neuraminidase N1]], also known as A(H5N1 or simply H5N1, is a subtype of the Influenza A virus which can cause

References

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