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garfish are the ultimate living fossil , having modify at an improbably obtuse stride since their ancestors emerge during the dinosaur geezerhood 150 million years ago , scientists have revealed . This easy rate of modification means these prehistoric fish have the slowest rate of molecular phylogenesis among all jawed craniate .
The gar ( family Lepisosteidae ) lineage extend across millennia , with the most anatomically modernistic species occur in the fogey record during the lateJurassic period(163.5 million to 145 million age ago ) . Seven bread and butter species dwell the lakes and river of North and South America , while one species occasionally ventures into maritime environments as well .
Alligator gar have one of the lowest rates of evolution among any jawed vertebrates, a study has revealed.
In a new field , issue in the journalEvolutionon March 4 , scientist examined gars and other species referred to as living fogey — organism that have remain the same over long periods of clip .
The term is contentious because while many such species resemble their fossil relatives , they have really undergoneevolutionary changes , even if they are not straightaway evident . To be a living fogey , an organism needs to have ancient mutual ancestry with nonextant lineages , have changed little in physical form from fossil relatives and radiate into a relatively small number of related specie , conduce authorChase Brownstein , a first twelvemonth graduate student at Yale , told Live Science .
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Longnose gars (pictured) can hybridize with alligator gar despite having separated 100 million years ago.
The research worker used electronic computer analysis to study factor sequences that were retained from common root — known as orthologs — which let out the rate of cistron exchange or mutation over time .
" Once a mutant fixes and shift a picky DNA successiveness , it becomes a substitution , " Brownstein said .
The subject found that some animals that are view living fossils , such as the tuatara ( Sphenodon punctatus ) , thecoelacanth(Latimeria chalumnae ) and the Opisthocomus hoazin ( Opisthocomus hoazin ) are different from their fogy relatives in important way , though they have retained many of their characteristic .
Gars and the related to sturgeon , however , look to have evolved at even slower charge per unit .
Of the 471 species surveyed , gars and sturgeons had the slowest rates of substitution . Gars seem to evolve at rate of up to three orders of order of magnitude slower than any other living vertebrates .
Substitutions lead in physical change . The miserable rates of substitution in this mathematical group of fish thus correspond to low rates of speciation — meaning the bloodline has not diversified into huge number of new , physically clear-cut species as other radical have . Instead , the few mintage that have emerged have remain stable over prospicient periods .
They have evolved so slowly , that two species separated by 100 million long time of evolution can still interbreed . Alligator gars ( Atractosteus spatula ) and longnose gars ( Lepisosteus osseus ) are known to interbreed in the rivers of Texas and Oklahoma . Other gar species have bring about hybrids as well .
" That would essentially be the equivalent of people and wombats [ producing hybrids ] , " Brownstein said , referring to the amount of sentence since the two metal money diverge .
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Even more queerly , these hybrids are often fecund . Naturally pass off and artificially bring on hybrids are sometimes sterile , even when more closely refer — as in the classic typeface of the mule ( Equus asinus × caballus ) , a crossbreed between a horse ( E. caballus ) and a donkey ( E. asinus ) .
Interestingly , long - nosed and gator gars do not look to have interbreed significantly over the course of action of their evolutionary history , despite having shared the same environment for around 55 million years . hybrid may occur now because the two species are pull to share spawning ground in sure river floodplains , according to the subject .
Brownstein said the research has raised further questions about how exactly the genomes of gars and other keep fossil have remained so stable .
" There ’s a mechanism behind the low permutation rate as well , " he order . " There ’s some sort of setup that we think is credibly related to desoxyribonucleic acid repair . "
