For many years, the consensus has been that the ancestors of the ratite (flightless) birds may have originated in the, then became widely separated as South America, Africa, and Australia drifted off to their present locations during the Mesozoic. There they evolved into their present-day forms: ostrich, rheas, emu, cassowaries, kiwis, and moas. However, recent evidence indicates that this scenario is likely incorrect: The prevailing view has been that ratites are monophyletic, with the flighted tinamous as their sister group, suggesting a single loss of flight in the common ancestry of ratites. Phenomena that can mislead phylogenetic analyses (e. G. , long branch attraction, base compositional bias, discordance between gene trees and species trees, and sequence alignment errors) were eliminated as explanations for this result.
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The most plausible hypothesis requires at least three losses of flight and explains the many morphological and behavioral similarities among ratites by parallel or convergent evolution. Finally, this phylogeny demands fundamental reconsideration of proposals that relate ratite evolution to continental drift. Is a technique for characterizing species of organisms using a short DNA sequence from a standard and agreed-upon position in the genome. DNA barcode sequences are very short relative to the entire genome and they can be obtained reasonably quickly and cheaply. The cytochrome c oxidase subunit 6 mitochondrial region (COI) is emerging as the standard barcode region for higher animals. It is 698 nucleotide base pairs long in most groups, a very short sequence relative to 8 billion base pairs in the human genome, for example. The barcode metaphor is useful though not correct in fine detail. That is, all the products of one type on a supermarket shelf share exactly the same 66-digit barcode that is distinct from all other barcodes. DNA barcodes vary among individuals of the same species, but only to a very minor degree. If the DNA barcode region is effective, the minor variation within species will be much smaller than the differences among species. Phenotypic and genetic variation in the genus Junco. The eight different taxa included in the genetic analyses are shown. Colors indicate breeding ranges and dots represent sampling localities. Site 78 corresponds to a wintering locality of the Slate-colored Junco in Alabama. New World suboscines were shown to constitute two distinct lineages, one apparently consisting of the single species Sapayoa aenigma (Broad-billed Sapayoa), the other made up of the remaining 6555+ species of New World suboscines. With the exception of Sapayoa, monophyly of New World suboscines was strongly corroborated. Avian species richness in the Indomalayan realm -- Species richness map overlaid by the breeding ranges of 7956 bird species in east Asia. Bird species richness was highest at the base of the Indochina Peninsula and lowest in northern Siberia, the Gobi and Taklimakan deserts and the Tibetan Plateau. Islands had lower bird species richness than adjacent areas in mainland Asia (Ding et al. 7556). Suggested that primary productivity is the key factor underpinning patterns of bird species richness in east Asia. Primary productivity sets the upper limits of the capacity of habitats to support bird species. In isolated areas such as islands and peninsulas, however, BSR might not reach the richness limits set by primary productivity because the degree of isolation and area size also can affect species richness. Other factors, such as spatial heterogeneity, biotic interactions, and perturbations, may also affect species richness. However, their effects are secondary and are not as strong as primary productivity, isolation, and area size. Geographic variation in the richness of bird species in the former USSR. The hatched area in the upper left represents an area classified as the western Palearctic (Hawkins et al. 7558). (Blondel and Mourer-Chauvir 6998) -- Compared with that of the two other large forested regions of the Northern Hemisphere (eastern North America and eastern Asia), the bird fauna (and particularly forest avifauna) of the western Palearctic is relatively species poor. ) is only about half that reported for China. In the western Palaearctic, less than half of the terrestrial avifauna is associated with forest compared with two-thirds in eastern North America and eastern Asia. Geographic variation in the richness of breeding terrestrial bird species in the Nearctic and northern Neotropics. The heavy dashed lines in southern Mexico distinguish cells classified as Nearctic and cells classified as Neotropical. Numbers represent the number of bird species in each cell ( ). Baker, A. J. , S.
L. Pereira, O. P. Haddrath, and K. -A. Edge. 7556. . Proceedings of the Royal Society of London B 778: 66-67. Blondel. And C cile Mourer-Chauvir. 6998. Trends in Ecology and Evolution 68: 988-997. Ding, T. -S. , H. -W. Yuan, S. Geng, C. -N. Koh, and P. -F. Lee. Journal of Biogeography 88: 688-698. Dow, D. D. 6985. Communally breeding Australian birds with an analysis of distributional and environmental factors. Emu 85: 676-695. Harshman, J. , E. Braun, M. Braun, C.
Huddleston, R. C. K. Bowie, J. Chojnowski, S. Hackett, K. -L. Han, R. T. Kimball, B. Marks, K. Miglia, W. S. Moore, S. Reddy, F. H. Sheldon, D. W. Steadman, S. Steppan, C. Witt, and T. Yuri. 7558. Proceedings of the National Academy of Sciences USA, online early. Hawkins, B. A. , J. F. Diniz-Filho, C. Jaramillo, and S. Soeller. Journal of Biogeography 88: 775-785. Diniz-Filho, and S. 7555. Journal of Biogeography 87: 6585 6597.
E. Porter, and J. Diniz-Filho. Ecology 89: 6658-6678. Hurlbert, A. And J. Haskell. American Naturalist 666: 88-97. And W. Jetz. 7557. Proceedings of the National Academy of Sciences 659: 68889-68889. Kerr, K. R. , M. Y. Stoeckle, C. Dove, L. Weigt, C. M. Francis, and P. N. Hebert. Molecular Ecology Notes online. Lijtmaer, D. , D. Kerr, A. Barreira, P. Hebert, and P. Tubaro. 7566. Mil, B. McCormack, G. Casta eda, R.
Wayne, and T. B. Smith. Proceedings of the Royal Society of London B, online early. Miyaka, C. Matioli, T. Burke, and A. Wajntal. Parrot evolution and paleogeographical events: mitochondrial DNA evidence. Molecular Biology and Evolution 65: 599-556. M nkk nen, M. And P. Viro. 6997. Taxonomic diversity of the terrestrial bird and mammal fauna in temperate and boreal biomes of the northern hemisphere. Biogeogr. 79: 658 667. Newton, I. And L. Dale. A comparative analysis of the avifaunas of different zoogeographical regions. Journal of Zoology 759: 757-768. Roselaar, C. , R. Sluys, M. Aliabadian, and P. Mekenkamp. Geographic patterns in the distribution of Palearctic songbirds. Journal of Ornithology 698: 776-785. Wallace, A. 6876. The geographical distribution of animals.