The Lerma River ( Spanish : Río Lerma ) is Mexico 's second longest river.
59-531: It is a 750 km-long (470 mi) river in west-central Mexico that begins in Mexican Plateau at an altitude over 3,000 metres (9,843 ft) above sea level, and ends where it empties into Lake Chapala , Mexico's largest lake, near Guadalajara , Jalisco . Lake Chapala is also the starting point of Río Grande de Santiago , which some treat as a continuation of the Lerma River. In combination,
118-556: A cave environment limits an organism's ability to disperse, since caves are often not connected to each other. One hypothesis for how closely related troglobite species could become isolated from one another in different caves is that their common ancestor may have been less restricted to cave habitats. When climate conditions became unfavorable, the ancestral species was extirpated from the surface, but some populations survived in caves, and diverged into different species due to lack of gene flow between them. Isolated islands commonly develop
177-478: A euendemic the vicariance was geologic in nature, such as the movement of tectonic plates, but in a cryptoendemic the disjunct distribution was due to the extinction of the intervening populations. There is yet another possible situation that can cause a disjunct distribution, where a species is able to colonize new territories by crossing over areas of unsuitable habitat, such as plants colonizing an island – this situation they dismiss as extremely rare and do not devise
236-435: A few Chirostoma silversides and all three Evarra chubs are already extinct . The Lerma–Chapala–Grande de Santiago basin and associated systems have four endemic cambarid crayfish: Cambarellus chapalanus , C. lermensis , C. prolixus and Procambarus digueti . The Lerma River has had chronic problems with pollution. Most of the problems are due to untreated and under-treated wastewater being discharged into
295-402: A holoendemic is a cosmopolitan species. Stenoendemics, also known as local endemics, have a reduced distribution and are synonymous with the word 'endemics' in the traditional sense, whereas euryendemics have a larger distribution -both these have distributions that are more or less continuous. A rhoendemic has a disjunct distribution . Where this disjunct distribution is caused by vicariance, in
354-437: A limited range. Paleoendemism is more or less synonymous with the concept of a ' relict species ': a population or taxon of organisms that were more widespread or more diverse in the past. A 'relictual population' is a population that currently occurs in a restricted area, but whose original range was far wider during a previous geologic epoch . Similarly, a 'relictual taxon' is a taxon (e.g. species or other lineage) that
413-513: A much larger area, but died out in most of their range, are called paleoendemic , in contrast to neoendemic species, which are new species that have not dispersed beyond their range. The ginkgo tree, Ginkgo biloba , is one example of a paleoendemic species. In many cases biological factors, such as low rates of dispersal or returning to the spawning area ( philopatry ), can cause a particular group of organisms to have high speciation rates and thus many endemic species. For example, cichlids in
472-522: A name for. Traditionally, none of Myers and de Grave's categories would be considered endemics except stenoendemics. Some environments are particularly conducive to the development of endemic species, either because they allow the persistence of relict taxa that were extirpated elsewhere, or because they provide mechanisms for isolation and opportunities to fill new niches. Serpentine soils act as ' edaphic islands' of low fertility and these soils lead to high rates of endemism. These soils are found in
531-465: A number of endemics. Many species and other higher taxonomic groups exist in very small terrestrial or aquatic islands, which restrict their distribution. The Devil's Hole pupfish, Cyprinodon diabolis , has its whole native population restricted to a spring that is 20 x 3 meters, in Nevada 's Mojave Desert . This 'aquatic island' is connected to an underground basin; however, the population present in
590-548: A plateau more than 2,600 metres (8,500 ft) above sea level, and 24 kilometres (15 mi) southeast from the city of Toluca . The lagoons receive their water from springs rising from basaltic volcanics that flow down from Monte de Las Cruces . These are located between the Valley of Toluca and the Basin of Mexico. The river forms the short border between the states of Querétaro and Michoacán then flows west-northwest through
649-403: A regular basis with an average running efficiency of about 70 per cent. Six further treatment facilities were under construction to raise the regional capacity to 9.56 cubic metres per second (338 cu ft/s). In Lake Chapala, into which the Lerma River flows, water quality improved from 90% of the lake having poor water quality in 1989 to 85% of the lake having good quality in 1997. However,
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#1732781164975708-405: A species that is endemic is "precinctive", which applies to species (and other taxonomic levels) that are restricted to a defined geographical area. Other terms that sometimes are used interchangeably, but less often, include autochthonal, autochthonic, and indigenous; however, these terms do not reflect the status of a species that specifically belongs only to a determined place. The word endemic
767-504: A very restrictive range, due to the unique environmental characteristics. The Kula Volcano , one of the fourteen volcanoes in Turkey , is home to 13 endemic species of plants. Endemics might more easily become endangered or extinct because they are already restricted in distribution. This puts endemic plants and animals at greater risk than widespread species during the rapid climate change of this century. Some scientists claim that
826-625: A wide variety of evolutionary histories, so researchers often use more specialized terms that categorize endemic species based upon how they came to be endemic to an area. Different categorizations of endemism also capture the uniqueness and irreplaceability of biodiversity hotspots differently and impact how those hotspots are defined, affecting how resources for conservation are allocated. The first subcategories were first introduced by Claude P. E. Favager and Juliette Contandriopoulis in 1961: schizoendemics, apoendemics and patroendemics. Using this work, Ledyard Stebbins and Jack Major then introduced
885-437: A wider distributed taxon that has become reproductively isolated without becoming (potentially) genetically isolated – a schizoendemic has the same chromosome count as the parent taxon it evolved from. An apoendemic is a polyploid of the parent taxon (or taxa in the case of allopolyploids ), whereas a patroendemic has a lower, diploid chromosome count than the related, more widely distributed polyploid taxon. Mikio Ono coined
944-457: Is also of interest in evolutionary biology , because it provides clues about how changes in the environment cause species to undergo range shifts (potentially expanding their range into a larger area, or becoming extirpated from an area they once lived), go extinct, or diversify into more species. The extreme opposite of an endemic species is one with a cosmopolitan distribution , having a global or widespread range. A rare alternative term for
1003-487: Is endemic to Earth. However, endemism is normally used only when a species has a relatively small or restricted range. This usage of "endemic" contrasts with "cosmopolitan." Endemics are not necessarily rare; some might be common where they occur. Likewise, not all rare species are endemics; some may have a large range but be rare throughout this range. The evolutionary history of a species can lead to endemism in multiple ways. Allopatric speciation , or geographic speciation,
1062-469: Is from Neo-Latin endēmicus , from Greek ἔνδημος, éndēmos , "native". Endēmos is formed of en meaning "in", and dēmos meaning "the people". The word entered the English language as a loan word from French endémique , and originally seems to have been used in the sense of diseases that occur at a constant amount in a country, as opposed to epidemic diseases, which are exploding in cases. The word
1121-503: Is home to its biggest metro areas of Guadalajara , León , Querétaro , Morelia , Mexico City , Toluca , Cuernavaca , and Puebla . The Mesa del Norte or northern plateau averages 1,100 metres (3,600 ft) in elevation above mean sea level and extends south from the Rio Grande (Río Bravo del Norte) through the states of Chihuahua , Coahuila , Durango , Zacatecas and San Luis Potosí . Various narrow, isolated ridges cross
1180-584: Is mostly covered by deserts and xeric shrublands , with pine-oak forests covering the surrounding mountain ranges and forming sky islands on some of the interior ranges. The Mexican Altiplano is one of six distinct physiographic sections of the Basin and Range Province , which in turn is part of the Intermontane Plateaus physiographic division. In phytogeography , the Sonoran Desert
1239-511: Is not navigable by water craft, but it is critical to regional agricultural irrigation. In the Lerma River/Lake Chapala watershed, 52,125 of the total 78,000 (roughly 67%) farmers are classified as small farmers. Currently 820,000 hectares are irrigated and an estimated three million hectares are in agricultural production. The population in the watershed as of 1997 was 9.35 million with an annual growth rate slightly less than
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#17327811649751298-434: Is only possible where 1.) the taxonomy of the species in question is not in dispute; 2.) the species distribution is accurately known; and 3.) the species have relatively small distributional ranges. In a 2000 article, Myers et al . used the standard of having more than 0.5% of the world's plant species being endemic to the region to designate 25 geographical areas of the world as biodiversity hotspots . In response to
1357-618: Is the sole surviving representative of a formerly diverse group. The concept of phylogenetic endemism has also been used to measure the relative uniqueness of the species endemic to an area. In measurements that incorporate phylogenetic endemism, branches of the evolutionary tree are weighted by how narrowly they are distributed. This captures not only the total number of taxa endemic to the area (taxonomic endemism), but also how distant those species are from their living relatives. Schizoendemics, apoendemics and patroendemics can all be classified as types of neoendemics. Schizoendemics arise from
1416-498: Is therefore said to be endemic to that particular part of the world. An endemic species can also be referred to as an endemism or, in scientific literature, as an endemite . Similarly many species found in the Western ghats of India are examples of endemism. Endemism is an important concept in conservation biology for measuring biodiversity in a particular place and evaluating the risk of extinction for species. Endemism
1475-718: Is when two populations of a species become geographically separated from each other and as a result develop into different species. In isolated areas where there is little possibility for organisms to disperse to new places, or to receive new gene flow from outside, the rate of endemism is particularly high. For example, many endemic species are found on remote islands , such as Hawaii , the Galápagos Islands and Socotra . Populations on an island are isolated, with little opportunity to interbreed with outside populations, which eventually causes reproductive isolation and separation into different species. Darwin's finches in
1534-729: Is within the Sonoran Floristic Province of the Madrean Region in southwestern North America , part of the Holarctic realm of the northern Western Hemisphere . While the plateau stretches from north to south, the southern east-west arc of the Central Mexican Plateau from Jalisco to Veracruz states historically as well as today has served as the population nexus of the Mexican nation, it
1593-812: The United States border in the north to the Trans-Mexican Volcanic Belt in the south, and is bounded by the Sierra Madre Occidental and Sierra Madre Oriental to the west and east, respectively. A low east-west mountain range in the state of Zacatecas divides the plateau into northern and southern sections. These two sections, called the Northern Plateau ( Mesa del Norte ) and Central Plateau ( Mesa Central ), are now generally regarded by geographers as sections of one plateau. The Mexican Plateau
1652-529: The 400-kilometre (249 mi) long Río Grande de Santiago , which continues from Lake Chapala northwest towards the Pacific Ocean , to be a continuation of the Lerma River. During the 17th and 18th centuries, large haciendas were established along this river, including the Atenco Ranch, which was founded with bulls that belonged to Hernán Cortés . The bulls from this area are considered some of
1711-960: The Balkan Peninsula, Turkey, Alps, Cuba, New Caledonia, South Africa, Zimbabwe, the North American Appalachians, and scattered distribution in California, Oregon, and Washington and elsewhere. For example, Mayer and Soltis considered the widespread subspecies Streptanthus glandulosus subsp. glandulosus which grows on normal soils, to be a paleoendemic, whereas closely related endemic forms of S. glandulosus occurring on serpentine soil patches are neoendemics which recently evolved from subsp. glandulosus . Obligate cave-dwelling species, known as troglobites, are often endemic to small areas, even to single individual caves, because cave habitats are by nature restricted, isolated, and fragmented. A high level of adaptation to
1770-571: The East African Rift Lakes have diversified into many more endemic species than the other fish families in the same lakes, possibly due to such factors. Plants that become endemic on isolated islands are often those which have a high rate of dispersal and are able to reach such islands by being dispersed by birds. While birds are less likely to be endemic to a region based on their ability to disperse via flight, there are over 2,500 species which are considered endemic, meaning that
1829-756: The Galápagos archipelago are examples of species endemic to islands. Similarly, isolated mountainous regions like the Ethiopian Highlands , or large bodies of water far from other lakes, like Lake Baikal , can also have high rates of endemism. Endemism can also be created in areas which act as refuges for species during times of climate change like ice ages . These changes may have caused species to become repeatedly restricted to regions with unusually stable climate conditions, leading to high concentrations of endemic species in areas resistant to climate fluctuations. Endemic species that used to exist in
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1888-679: The Mesa del Norte and numerous depressions also dot the region, the largest of which is the Bolsón de Mapimí . The Río Bravo del Norte and its tributary, the Río Conchos , drain portions of the northern plateau, and the Río Pánuco and its tributaries drain the southeastern corner. Both drain to the Gulf of Mexico . Much of the northern plateau comprises internal drainage basins that do not drain to
1947-546: The above, the World Wildlife Fund has split the world into a few hundred geographical ' ecoregions '. These have been designed to include as many species as possible that only occur in a single ecoregion, and these species are thus 'endemics' to these ecoregions. Since plenty of these ecoregions have a high prevalence of endemics existing within them, many National Parks have been formed around or within them to further promote conservation. The Caparaó National Park
2006-583: The concept. In their view, everything is endemic, even cosmopolitan species are endemic to Earth, and earlier definitions restricting endemics to specific locations are wrong. Thus the subdivisions neoendemics and paleoendemics are without merit regarding the study of distributions, because these concepts consider that an endemic has a distribution limited to one place. Instead, they propose four different categories: holoendemics, euryendemics, stenoendemics and rhoendemics. In their scheme cryptoendemics and euendemics are further subdivisions of rhoendemics. In their view,
2065-518: The concepts of neoendemics and paleoendemics in 1965 to describe the endemics of California. Endemic taxa can also be classified into autochthonous, allochthonous, taxonomic relicts and biogeographic relicts. Paleoendemism refers to species that were formerly widespread but are now restricted to a smaller area. Neoendemism refers to species that have recently arisen, such as through divergence and reproductive isolation or through hybridization and polyploidy in plants, and have not dispersed beyond
2124-609: The cool climates of mountain peaks are geographically isolated. For example, in the Alpes-Maritimes department of France, Saxifraga florulenta is an endemic plant that may have evolved in the Late Miocene and could have once been widespread across the Mediterranean Basin . Volcanoes also tend to harbor a number of endemic species. Plants on volcanoes tend to fill a specialized ecological niche , with
2183-478: The eastern portion of the southern plateau. The Central Mexican matorral covers much of the southern plateau, with the subtropical Bajío dry forests occupying the lower portions of the Lerma–Río Grande de Santiago basin. Higher altitudes are covered by pine–oak woodlands , with oak woodlands and forests at lower elevations, and mixed pine–oak and conifer forests up to the tree line of the volcanoes that surround
2242-541: The finest stock for bullfighting. The river is dotted with cities such as Lerma and San Mateo Atenco to small picturesque villages with cultural significance such as Malinalco . The Lerma River–Lake Chapala basin is considered to be the most important watershed in the country by the federal government. With its major tributaries, the Laja , Apaseo, and Turbio the Lerma constitutes Mexico's largest river system. The Lerma River
2301-454: The late 1980s because of uncoordinated water policies that did little or nothing to regulate water use among competing interests and failed to consider the effects of upstream activities to those living downstream. Government plans were drawn up due to intense public pressure leading to improvement of the water quality in the 1990s. By 1997, 45 plants with a treatment capacity of 5.72 cubic metres per second (202 cu ft/s) were operating on
2360-481: The most polluted, especially in stretches closest to its source near Almoloya del Río. Since 2005, industrial contaminants have become a serious concern as well as the continuing loss of plant life in and around the river itself. In 2005, thousands of fish suddenly died in the river in the municipality of Pénjamo in Guanajuato state when effluent flow depleted the oxygen in that part of the river. The lower parts of
2419-526: The national average. The population is distributed among 6,224 localities; 18 of these have a population greater than 50,000 inhabitants. The rural population is currently 32 per cent. The Lerma's water is also a source for the municipal water supply in the Guadalajara and Toluca metropolitan areas. While water extraction and use has been adequate for the region's larger population centers, rural areas have had chronic problems with access to potable water from
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2478-478: The native species in the basin), followed by the poeciliids and cyprinids (each has about 1 ⁄ 8 of the native species in the basin). Among these are many endemics , including several Chirostoma ("charales") silversides, several splitfins, a few Poeciliopsis livebearers, a few Algansea chubs, two Yuriria chubs, a few Notropis shiners, two Ictalurus catfish, two Tetrapleurodon lampreys, and more. Many of these are threatened , and
2537-615: The pool remains isolated. Other areas very similar to the Galapagos Islands of the Pacific Ocean exist and foster high rates of endemism. The Socotra Archipelago of Yemen, located in the Indian Ocean, has seen a new endemic species of parasitic leech, Myxobdella socotrensis, appear. This species is restricted to freshwater springs, where it may attach to and feed upon native crabs. Mountains can be seen as ' sky islands ': refugia of endemics because species that live in
2596-404: The presence of endemic species in an area is a good method to find geographical regions that can be considered priorities for conservation. Endemism can thus be studied as a proxy for measuring biodiversity of a region. The concept of finding endemic species that occur in the same region to designate 'endemism hotspots' was first proposed by Paul Müller in a 1973 book. According to him, this
2655-403: The river and the aquifers that feed it. Wells drilled into these aquifers have very low yields. The Lerma–Chapala–Grande de Santiago basin and associated systems are rich in freshwater fish, being the home of more than 100 native species and 19 introduced species. Among the natives, the two most diverse families are the splitfins and Neotropical silversides (each has about 1 ⁄ 4 of
2714-564: The river, closer to Lake Chapala are in better shape because there is less urbanization there. 20°13′N 102°46′W / 20.217°N 102.767°W / 20.217; -102.767 Mexican Plateau The Central Mexican Plateau , also known as the Mexican Altiplano ( Spanish : Altiplano mexicano ), is a large arid-to-semiarid plateau that occupies much of northern and central Mexico . Averaging 1,825 m (5,988 ft) above sea level, it extends from
2773-506: The river. Reservoirs constructed to control the highly varied flow of the river are often choked with water hyacinths due to eutrophication caused by the untreated effluents. The most important industries in the Lerma River area are those that produce meat, dairy, produce, beverages, pulp and paper, leather goods, petrochemical and chemical products. Little or no emphasis on wastewater treatment and recycling has been imposed upon these economic activities. The situation became extremely bad in
2832-640: The sea. The Chihuahuan Desert extends across the northern portion of the northern plateau, while the Meseta Central matorral covers the central portion, and the Central Mexican matorral extends from the southern portion of the northern plateau across the southern plateau. The Mesa Central or southern plateau is higher than its northern counterpart, averaging 2,000 m (6,600 ft) in elevation. The southern plateau contains numerous valleys originally formed by ancient lakes. It extends across
2891-453: The southern and western edges. Endemism Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsewhere. For example, the Cape sugarbird is found exclusively in southwestern South Africa and
2950-484: The species is restricted to an area less than five million hectares (twelve million acres). Microorganisms were traditionally not believed to form endemics. The hypothesis 'everything is everywhere', first stated in Dutch by Lourens G.M. Baas Becking in 1934, describes the theory that the distribution of organisms smaller than 2 mm is cosmopolitan where habitats occur that support their growth. Endemism can reflect
3009-441: The state of Guanajuato . After turning southward, the river separates Guanajuato and Michoacán, and Michoacán and Jalisco before flowing, after a course of about 560 kilometres (350 mi), into Lake Chapala, 24 kilometres (15 mi) west-southwest of La Barca. It has a length of 750 kilometres (470 mi). When it empties into Lake Chapala, the system stands at 1,510 metres (4,950 ft) above sea level. Some people consider
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#17327811649753068-589: The states of Aguascalientes , Jalisco , Zacatecas , Guanajuato , Querétaro , and Michoacán . Several of Mexico's most prominent cities, including Guadalajara, are located in the valleys of the southern plateau. Much of the southern plateau is drained by the Río Grande de Santiago and its tributaries, including the Río Lerma , which drain west into the Pacific Ocean . Tributaries of the Río Pánuco drain
3127-424: The term 'aneuendemics' in 1991 for species that have more or fewer chromosomes than their relatives due to aneuploidy . Pseudoendemics are taxa that have possibly recently evolved from a mutation. Holoendemics is a concept introduced by Richardson in 1978 to describe taxa that have remained endemic to a restricted distribution for a very long time. In a 2000 paper, Myers and de Grave further attempted to redefine
3186-572: The threatened nature of a geographic region. A similar pattern had been found regarding mammals, Lasioglossum bees, Plusiinae moths, and swallowtail butterflies in North America: these different groups of taxa did not correlate geographically with each other regarding endemism and species richness. Especially using mammals as flagship species proved to be a poor system of identifying and protecting areas of high invertebrate biodiversity. In response to this, other scientists again defended
3245-493: The two are often called the Lerma Santiago River ( Spanish : Río Lerma Santiago ). The Lerma River is notorious for its pollution , but the water quality has demonstrated considerable improvement in recent years due mostly to government environmental programs and through a vast program of upgrading local sanitation infrastructure. The Lerma River originates from the Lerma lagoons near Almoloya del Río , on
3304-516: The worst water quality was still closest where the Lerma River discharged into the lake. However, in the decade beginning in 2000, contamination levels of the river system were alarming, with studies in Michoacán and Guanajuato documenting an increase in cancer and neurocysticercosis in populations that live near the river. The Lerma River portion of the Lerma–Chapala basin is considered to be
3363-518: Was first used in botany by Vaughan MacCaughey in Hawaii in 1917. A species is considered to be endemic to the area where it is found naturally, to the exclusion of other areas; presence in captivity or botanical gardens does not disqualify a species from being endemic. In theory, the term "endemic" could be applied on any scale; for example, the cougar is endemic to the Americas, and all known life
3422-566: Was formed in the Atlantic Forest , a biodiversity hotspot located in Brazil, in order to help protect valuable and vulnerable species. Other scientists have argued that endemism is not an appropriate measure of biodiversity, because the levels of threat or biodiversity are not actually correlated to areas of high endemism. When using bird species as an example, it was found that only 2.5% of biodiversity hotspots correlate with endemism and
3481-469: Was used in biology in 1872 to mean a species restricted to a specific location by Charles Darwin . The less common term 'precinctive' has been used by some entomologists as the equivalent of 'endemic'. Precinctive was coined in 1900 by David Sharp when describing the Hawaiian insects, as he was uncomfortable with the fact that the word ' endemic ' is often associated with diseases. 'Precinctive'
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